CN102877964B - The method and system of turbocharged engine - Google Patents

Abstract

Method and system for the engine with supercharger with the separate type gas handling system coupled with separate type gas extraction system is provided.The air with heterogeneity, pressure and temperature can be conveyed at the difference of cycle of engine to engine by separate type gas handling system to inflate.In this way, it is possible to extend supercharging and EGR benefits.

Description

Method and system for a turbocharged engine

Cross References to Related Applications

This application is a continuation-in-part of U.S. Patent Application Serial No. 12/878,838, filed September 9, 2010, entitled "Method and system for turbocharging an engine," in its entirety incorporated herein by reference.

technical field

The present description relates to methods for increasing the thermal efficiency of a turbocharged engine. This method may be particularly beneficial in providing EGR in turbocharged engines.

Background technique

Engine cylinders may be configured with one or more intake ports for receiving an air charge. One or more air intakes may branch off from a common air intake, or may have different air intake ducts. Additionally, one or more air intakes may receive fresh air or may circulate exhaust.

An example of a cylinder with a branched intake system is shown by Duret in 6,135,088. Therein, during low load conditions, the first inlet port of the cylinder is configured to receive recirculated exhaust gas and the second inlet port is configured to receive the air-fuel mixture that has been pressurized after the intake port by the compressor.

However, the inventors herein have recognized potential problems with such systems. As one example, adding an exhaust turbine to drive a compressor can destroy the desired functionality of the system. Specifically, if the turbines are included in a common exhaust port, high pressure exhaust gas may be drawn into a lower pressure (ie, unboosted) intake port, causing EGR control issues. As another example, under certain conditions it may be difficult to provide higher pressure EGR (HP-EGR) to further improve engine performance.

Contents of the invention

Accordingly, in one example, the above problem is at least partially addressed by a method of operating an engine comprising providing a charge of air at or below atmospheric pressure to an engine cylinder through a first intake port and through a separate second intake port A second boost air charge is provided to the cylinders, which is boosted by an intake compressor driven by an exhaust turbine. In this way, the intake compressor may be driven by the exhaust turbine to provide a boosted intake air charge to the cylinder through the intake port while concurrently providing a naturally aspirated air charge to the cylinder through a separate intake port. The different air charges can then be mixed with each other and charged into the cylinder prior to combustion.

In one example, a first intake port may be coupled to a first exhaust port, while a separate second intake port is coupled to a separate second exhaust port. A turbocharger compressor coupled only to the second intake port may be driven by a turbocharger turbine coupled only to the second exhaust port to provide a charge air charge within the second intake port. In one example, fresh air at or below barometric pressure (BP) may be delivered to the cylinders via a first intake valve in communication with the first intake port, while fresh air at compressor pressure (ie, charge air ) may be delivered to the cylinder via a second intake valve in communication with the second intake port. In this way, at least a portion of the fresh intake air can be provided by natural aspiration, while another portion is compressed. By reducing the portion of the intake air that needs to be compressed, compressor efficiency can be increased and control delays can be reduced. In addition, ideal boost can be provided by smaller compressors and turbines without compromising boost performance.

In an alternative example, one or both of the first and second air charges may include at least some fresh air and at least some recycled exhaust gas. For example, at least some low-pressure EGR (LP-EGR) circulating from the first exhaust port to the first intake port may mix with fresh air within the first intake port at or below BP to form the first air charge. Additionally, at least some high pressure EGR (HP-EGR) circulated from the second exhaust port to the second intake port may mix with charge fresh air within the second intake port to form a second air charge. The first and second air charges may be mixed with each other and injected directly into the cylinder prior to combustion. The opening timing of different intake valves coupled to different intake ports may be different relative to each other to deliver different air charges at different points of the engine's intake stroke. Intake valve timing may also be coordinated with opening of different exhaust valves coupled to different exhaust ports.

In this way, by allowing only a portion of the exhaust to flow through the turbine while the remainder is naturally drawn into the cylinders, the heat recovered from the exhaust is increased and the thermodynamic efficiency of the turbine is increased. By naturally drawing some fresh air into the engine cylinders while boosting the remainder, compressor work can be reduced, increasing compressor efficiency. In addition, boost control delay can be reduced. By providing air charge to the engine cylinders via no intake ports with different proportions of recirculated exhaust gas and fresh air at different pressures, the EGR benefits can be extended and the benefits of the turbocharger can be increased, even with smaller turbochargers. The compressor is still the same. In this way, engine efficiency and performance can be improved.

In another example, a method of operating an engine includes delivering a first subatmospheric pressure air charge to engine cylinders via a first intake port, the first air charge including a first amount of recirculated exhaust gas and a first amount of fresh air; and delivering a second air charge at compressor pressure to the engine cylinders via a separate second intake port, the second air charge comprising a second amount of recirculated exhaust gas and a second amount of fresh air.

In another example, the method further includes directly injecting fuel into the cylinder; mixing the first air charge with the second air charge and the injected fuel within the cylinder; and combusting the mixture within the cylinder.

In another example, delivering the first charge of air includes opening a first intake valve of the first intake port at a first intake valve timing; and wherein delivering the second charge of air includes opening the second intake valve timing The second intake valve of the second intake port.

In another example, delivering the first charge of air further includes opening the first EGR valve to circulate the first amount of exhaust gas from the first exhaust port to the first intake port; and delivering the second charge of air further includes opening the first EGR valve. The two EGR valves thereby circulate a second amount of exhaust gas from the separate second exhaust port to the second intake port.

In another example, delivering the second charge of air at compressor pressure further includes operating a compressor included in the second intake passage, the compressor being driven by a turbine included in the second exhaust passage, and wherein the second A large amount of exhaust gas is circulated from upstream of the turbine to downstream of the compressor.

In another example, the first intake valve and the second intake valve are coupled to the valve actuator, further comprising: adjusting a valve phase of the valve actuator to open the first valve at the first intake valve timing and The second valve is opened at a second intake valve timing, the first intake valve timing being earlier than the second intake valve timing in an intake stroke of the engine cycle.

In another example, delivering the first charge of air further includes opening a first exhaust valve of a first exhaust port at a first timing and opening a second exhaust valve of a second exhaust port at a second, earlier timing. Door.

In another example, an engine system is provided. The system includes an engine cylinder; a first intake port communicating an uncompressed air charge to the engine cylinder via a first intake valve; a second intake port communicating a compressed air charge to the cylinder via a second intake valve; configured to compress a turbocharger compressor coupled to the first intake port for delivering air charge to the cylinder; a valve actuator for opening the first intake valve and the second intake valve; and a control system having Computer readable instructions for adjusting phasing of the valve actuators to open the first intake valve at a first timing and open the second intake valve at a second, different timing.

In another example, the uncompressed air charge includes at least some fresh air and at least some EGR at or below atmospheric pressure, and wherein the compressed air charge includes at least some fresh air and at least some EGR at compressor pressure.

In another example, the first intake port is parallel to and independent of the second intake port, the system further includes: first and second exhaust ports, the first exhaust port is parallel to and independent of the second exhaust port and a turbocharger turbine coupled to the second exhaust passage, the turbine configured to drive the compressor.

In another example, the system further includes: a first EGR passage communicatively coupling the first exhaust passage to the first intake passage, the first EGR passage including a first EGR cooler and a first EGR valve; and The second exhaust port is communicatively coupled to the second EGR passage of the second intake port, the second EGR passage includes a second EGR cooler and a second EGR valve, wherein the control system further includes instructions for opening the first an EGR valve to deliver at least some EGR at or below ambient pressure to the first intake port and open a second EGR valve to deliver at least some EGR at compressor pressure from the second exhaust port upstream of the turbine to the compressor Downstream second intake.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is to be defined solely by the claims of this application. Furthermore, the claimed subject matter is not limited to implementations that overcome any disadvantages noted above or in any part of this disclosure.

Description of drawings

Figure 1 shows a schematic diagram of an engine including a split intake manifold and a split exhaust manifold and associated exhaust gas circulation system.

FIG. 2 illustrates an exemplary embodiment of the engine cylinder of FIG. 1 coupled to first and second intake ports and first and second exhaust ports.

Figure 3 shows a partial engine view.

FIG. 4 shows a high level flow diagram illustrating a routine executable for operating cylinders of the engine of FIG. 2 in accordance with the present disclosure.

FIG. 5 shows example cylinder intake and exhaust valve timings for the engine cylinder of FIG. 2 .

FIG. 6 illustrates an example air-charge mixture that may be provided to the cylinder of FIG. 2 during different operating conditions via the first and second intake ports.

FIG. 7 shows a high level flowchart illustrating a routine that may be executed for coordinating intake air throttle operation with turbocharger operation during tip-in.

FIG. 8 shows a diagram explaining example intake air throttle and EGR valve adjustments during a tip-in.

FIG. 9 shows a high level flowchart illustrating a routine that may be executed for adjusting operation of the EGR cooler based on engine operating conditions.

detailed description

The following description relates to systems and methods for controlling an engine, such as the engine system of FIGS. 1-3 , by supplying engine cylinders with different pressures and / or air charge of different composition (eg different ratio of fresh air to EGR). Specifically, the intake air charge at or below atmospheric pressure can be provided to the cylinders separately from the intake air charge at compressor pressure. Similarly, an intake air charge including recirculated exhaust gas can be provided to the cylinders separately from the intake air charge with fresh air. As shown in FIG. 6, other combinations are also possible. The engine controller may be configured to execute a control routine, such as the FIG. 4 routine, to open the intake valve of the first cylinder at an earlier timing than the intake valve of the second cylinder ( FIG. 5 ) so as to be consistent with the intake valve of the second component The first air charge of the first composition is provided at a different time in the engine cycle than the second air charge. Intake valve timing can also be coordinated with the corresponding exhaust valve timing (Figure 5). The positions of one or more air intake throttles and EGR valves coupled to different intake ports may be adjusted and coordinated to compensate for transients, as shown in FIGS. 7-8 . In addition, various EGR valves may be adjusted to enable heating or cooling of the intake air charge of each intake port by a respective EGR cooler. In this way, the amount of turbocharger compression work expended pulling EGR may be reduced, thereby increasing the average intake and/or exhaust pressure to and from the turbocharger, thereby improving turbocharging output. Furthermore, by keeping the EGR-based air charge separate from the boost-based air charge until they mix within the cylinder, both EGR control and boost control delays may be reduced. Taken together, the benefits of both EGR and boosting can be extended, thereby improving engine performance and fuel efficiency.

FIG. 1 shows a schematic diagram of an exemplary turbocharged engine system 100 including a multi-cylinder internal combustion engine 10 and a turbocharger 50 . As a non-limiting example, engine system 100 could be included as part of a propulsion system of a passenger vehicle. Engine 10 may include a plurality of cylinders 14 . In the example shown, engine 10 includes three cylinders arranged in an inline configuration. However, in alternative examples, engine 10 can include two or more cylinders, such as 4, 5, 8, 10 or more cylinders, and it can be provided in alternative configurations, such as V-type, box-type, etc. . Each cylinder 14 may be configured with a fuel injector 166 . In the example shown, fuel injector 166 is a direct injection cylinder injector. In other examples, however, fuel injector 166 could be configured as a port fuel injector. Further details of the individual cylinders 14 are described below with respect to FIGS. 2-3 .

Each cylinder 14 of engine 10 is configured to receive an intake air charge (including fresh air and/or recirculated exhaust gas) from first intake passage 42 and second intake passage 44 . As such, the second intake passage 44 may be separate from but parallel to the first intake passage 42 . First intake passage 42 may include an air intake throttle 62 downstream of air filter 60 . The position of throttle valve 62 can be adjusted by control system 15 via a throttle actuator (not shown) communicatively coupled with controller 12 . By adjusting throttle 62 , a quantity of fresh air from ambient may be introduced into engine 10 via first intake passage 42 at or below atmospheric (or ambient) pressure and delivered to the engine cylinders. First intake passage 42 may branch into a plurality of intake conduits 43 a - 43 c downstream of throttle 62 . Each intake conduit 43a-43c may be coupled to a different engine cylinder and may be configured to deliver a portion of the intake air charge of intake passage 42 to the corresponding cylinder.

Second intake passage 44 may include an air intake throttle 64 downstream of charge air cooler 56 and turbocharger compressor 52 . Specifically, compressor 52 of turbocharger 50 may be included within and coupled to second intake passage 44 instead of first intake passage 42 . The position of throttle 64 can be adjusted by control system 15 via a throttle actuator (not shown) communicatively coupled with controller 12 . By adjusting air intake throttle 64 while compressor 52 is running, a quantity of fresh air may be introduced into engine 10 from ambient at compressor (or boost) pressure via second intake passage 44 and transmission to the engine cylinders. Second intake passage 44 may branch into a plurality of intake conduits 45 a - 45 c downstream of throttle 64 . Each intake conduit 45a - 45c may be coupled to a different cylinder and may be configured to deliver a portion of the intake air charge of intake passage 44 to the corresponding cylinder.

Exhaust gas generated during a cylinder combustion event may be expelled from each cylinder 14 along first exhaust passage 46 and second exhaust passage 48 . Exhaust passage 46 may branch into a plurality of exhaust ducts 47a-47c. Specifically, each exhaust conduit 47a - 47c may be coupled to a different cylinder and may be configured to convey a portion of the exhaust gas emitted from the corresponding cylinder into exhaust passage 46 . Exhaust gas flowing through first exhaust passage 46 may be treated by one or more exhaust aftertreatment devices, such as catalysts 70 and 72 , before being expelled to atmosphere along tailpipe 35 .

In the same way, the second exhaust duct 48 may branch into a plurality of exhaust ducts 49a-49c. Specifically, each exhaust conduit 47a - 47c may be coupled to a different cylinder and may be configured to convey a portion of the exhaust gas emitted from the corresponding cylinder into exhaust passage 48 . Turbine 54 of turbocharger 50 may be included in and coupled to second exhaust passage 48 instead of first exhaust passage 46 . Accordingly, products of combustion expelled via exhaust passage 48 can be directed through turbine 54 to provide mechanical work to compressor 52 via a shaft (not shown). In some examples, turbine 54 may be configured as a variable geometry turbine, wherein controller 12 may adjust the position of turbine wheel blades (or blades) in order to vary the level of energy obtained from the exhaust flow and applied to compressor 52 . Alternatively, exhaust turbine 54 may be configured as a variable nozzle turbine, where controller 12 may adjust the position of the turbine nozzle in order to vary the level of energy derived from the exhaust flow and applied to compressor 52 .

Exhaust flowing through second exhaust passage 48 may be treated by one or more exhaust aftertreatment devices, such as catalyst 72 , before being expelled to atmosphere along tailpipe 35 . In the example shown, exhaust gas from second exhaust passage 48 is combined with exhaust gas from first exhaust passage 46 downstream of turbine 54 and catalyst 70 but upstream of catalyst 72 such that the combined exhaust gas The gas is exhausted to the atmosphere along the exhaust pipe 35 . However, in alternative embodiments, exhaust passages 46 and 48 may not re-merge, and exhaust may be discharged via a separate tailpipe. Exhaust passages 46 and 48 may also include one or more exhaust gas sensors, as further shown in FIG. 3 .

Engine 10 may also include one or more exhaust gas recirculation (EGR) passages to recirculate at least a portion of exhaust gas from first and second exhaust passages 46 and 48 to first and second intake passages, respectively. 42 and 44. Specifically, first exhaust passage 46 may be communicatively coupled to first intake passage 42 via a first EGR passage 80 including a first EGR cooler 82 and a first EGR valve 84 . The engine controller may be configured to open first EGR valve 84 to circulate an amount of exhaust gas at or below ambient pressure to first intake passage 42 . In this way, low pressure EGR (LP-EGR) may be diverted from the first exhaust port to the first intake port.

Similarly, second exhaust passage 48 may be communicatively coupled to second intake passage 44 via second EGR passage 90 including second EGR cooler 92 and second EGR valve 94 . The engine controller may be configured to open second EGR valve 94 to circulate an amount of exhaust gas at compressor pressure from upstream of turbine 54 to second intake passage 44 downstream of compressor 52 . In this way, high pressure EGR (HP-EGR) may be provided to the engine via the second intake and exhaust passages. By providing LP-EGR via a first EGR passage and simultaneously providing HP-EGR via a separate second EGR passage, both HP-EGR and LP-EGR may be provided simultaneously, extending the benefits of EGR.

EGR coolers 82 and 92 may be configured to reduce the temperature of exhaust gas flowing through the respective EGR passages prior to circulation into the engine intake. In an alternative embodiment, EGR coolers 82 and 92 may be positioned at the junction of the EGR passage and the corresponding intake passage. In this position, as shown herein with respect to FIG. 9 , under certain conditions, an EGR cooler(s) may advantageously be used to heat the intake air charge being delivered to the cylinders. Specifically, the EGR cooler may be used to provide heated air charge (such as heated fresh air, or a mixture of heated gas and fresh air) to the engine cylinders under some conditions and to the engine cylinders under other conditions. The cylinders provide a cooled air charge (eg, cooled EGR). In one example, under cold engine conditions, the air charge delivered to the cylinder via the second intake port may be heated before entering the compressor in order to avoid water dripping on the compressor.

In yet other embodiments, a conduit may be coupled to an EGR passage. A conduit may couple second EGR passage 90 to first EGR passage 80 at a location between EGR valve 84 and EGR cooler 82 from a location between EGR valve 94 and EGR cooler 92 . Here, under some conditions, higher pressure exhaust gas released into the second exhaust passage via the second exhaust valve may be cooled within EGR cooler 92 and heat transferred to the coolant. Cooled exhaust gas may be circulated to the engine intake via the lower pressure first intake port. Alternatively, the cooled exhaust may be exhausted to atmosphere via first exhaust passage 46 and tailpipe 35 . In this way, a greater amount of work can be extracted from the exhaust.

Engine system 100 may also include valve actuator 96 for regulating valve operation of cylinder 14 . Specifically, valve actuator 96 may be configured to open a first intake and/or exhaust valve of cylinder 14 at a first timing and to open a second intake and/or exhaust valve of cylinder 14 at a second timing. valve. In this manner, a first air charge of a first composition at or below atmospheric pressure may be provided to engine cylinders at a first timing, while a second air charge of a second, different composition at compressor pressure may be provided at a first timing. Two timings are provided to the engine cylinders. As a non-limiting example, as shown in FIGS. 2-3 , valve actuator 96 may be configured as a cam actuator where the intake and/or exhaust valves of each cylinder 14 are coupled to respective cams. The controller may be configured to adjust the phase (or cam profile) of the valve actuator 96 (or cam actuator) to open the first intake valve at a first timing to deliver the first air charge based on engine operating conditions. And the second intake valve is opened at a second timing to deliver a second charge of air. For example, as shown here in FIG. 5 , the intake valve timing may be staggered so that a portion of the intake air charge is introduced by the compressor and another portion of the intake air charge is naturally aspirated.

The controller may also be configured to adjust valve phasing to open the first exhaust valve at a first timing and open the second exhaust valve at a second different timing to release exhaust gas at different pressures at different locations in the engine cycle. exhaust. For example, as shown here in Figure 5, the exhaust valve timing can be staggered to balance the release of blow down gases (such as the expanding exhaust gas in the cylinder when the cylinder piston reaches bottom dead center of the expansion stroke) with the residual exhaust gas. The release of gas (such as the gas remaining in the cylinder after blowing) is separated. In one example, emissions Energy can be diverted from the release of blown gases through the turbocharger turbine in the second exhaust passage to operate the turbocharger compressor in the second intake passage to provide boost benefit. At substantially the same time, residual gases can be diverted from the first exhaust port to the first intake port to provide EGR advantage. In this way, ideal EGR dilution may be provided, even under higher load conditions, without expending additional energy to pump exhaust gas from the exhaust manifold to the intake manifold via the EGR cooler.

It will be appreciated that while the illustrated engine system 100 circulates exhaust gases at or below atmospheric pressure through the first intake port, in other embodiments such as when the first intake port is coupled to the engine's fuel vapor recovery system , the first intake port may be configured to circulate one or more of pumped vapors, crankcase vapors, and gaseous or vaporized fuel vapors to the cylinders at or below atmospheric pressure.

Engine system 100 may be controlled at least in part by control system 15 including controller 12 and by input from a vehicle operator via an input device (shown in FIG. 3 ). The illustrated control system 15 receives information from a plurality of sensors 16 (various examples of which are described herein) and sends control signals to a plurality of actuators 81 . As one example, sensors 16 may include intake air pressure and temperature sensors, MAP sensors, and MAT sensors in one or both intake passages. Other sensors may include a throttle inlet pressure (TIP) sensor coupled in each intake port downstream of the throttle for estimating throttle inlet pressure (TIP) and/or a throttle air temperature (TCT) sensor for estimating throttle air temperature (TCT). Throttle inlet temperature sensor. In other examples, one or more EGR passages may include pressure, temperature, and/or air-to-fuel ratio sensors for determining EGR flow characteristics. Additional system sensors and actuators are shown below with reference to FIG. 3 . As another example, actuator 81 may include fuel injector 166 , EGR valves 84 and 94 , valve actuator 96 , and throttle valves 62 and 64 . Other actuators, such as various additional valves and throttles, may be coupled at various locations in engine system 100 . Based on instructions or code programmed therein corresponding to one or more programs, controller 12 may receive input data from various sensors, process the input data, and trigger actuators in response to the processed input data. Exemplary control routines are described herein with reference to FIGS. 4 , 7 and 9 .

Referring now to FIGS. 2-3 , a single cylinder 14 of internal combustion engine 10 is shown. As such, the same reference numerals are used to denote the components previously described in FIG. 1 and will not be described again. FIG. 2 shows a first view 200 of cylinder 14 . Here, cylinder 14 is shown with four ports, including two intake ports 17 and 18 and two exhaust ports 19 and 20 . Specifically, first intake port 17 in cylinder 14 may receive a first charge of air at or below ambient pressure from a first intake conduit 43 a coupled to first intake passage 42 via first intake valve 30 . The first air charge may include fresh air, low pressure recirculated exhaust gas (LP-EGR), or a mixture of fresh air and LP-EGR introduced into the cylinder at or below ambient pressure. Second intake port 18 of cylinder 14 may receive a second air charge at compressor pressure from second intake conduit 45 a coupled to second intake passage 44 via second intake valve 31 . The second air charge may include fresh air introduced into the cylinder at boost pressure after being compressed by compressor 52 , high pressure exhaust gas recirculated (HP-EGR), or a mixture of fresh air and HP-EGR.

A portion of cylinder combustion products may be exhausted from first exhaust port 19 of cylinder 14 via first exhaust valve 32 into first exhaust conduit 47 a coupled with first exhaust passage 46 . Another portion of the cylinder combustion products may be exhausted from the second exhaust port 20 of the cylinder 14 via the second exhaust valve 33 into a second exhaust conduit 49 a coupled with the second exhaust passage 48 . Exhaust gas may be sequentially released to the atmosphere along tailpipe 35 . Specifically, the first and second exhaust ports may be recombined downstream of the turbine and upstream of emission control device 72, allowing exhaust gas released into the first exhaust port to be processed by emission control devices 70 and 72 prior to release. Exhaust gases that are allowed to be released into the second exhaust passage before being released along the tailpipe 35 are processed by the device 72 . Additionally or alternatively, a portion of the exhaust gas may also be circulated from the first exhaust conduit 47a to the first intake passage 43a via the first EGR passage 80 while a portion of the exhaust gas may be circulated from the second bank via the second EGR passage 90 The air duct 49a is circulated to the second intake channel 45a. In other embodiments, the second exhaust port may be configured to provide exhaust to either the first or second intake port, and the first exhaust port may be configured to provide exhaust gas to either the first or second intake port. Provide exhaust.

In the example shown, first intake valve 30 and second intake valve 31 may each be operated by a respective intake valve cam ( FIG. 3 ). The position of the intake cams, and thus the timing of the intake valves, may be determined by intake cam actuator 97 via camshaft 101 . Similarly, first exhaust valve 32 and second exhaust valve 33 may each be operated by a respective exhaust cam ( FIG. 3 ), the position of which may be determined by exhaust cam actuator 98 via camshaft 102 . However, in alternative embodiments, each intake valve and each exhaust valve may have independent valve actuators. Further, the first intake valve and the first exhaust valve may be coupled to one (common) valve actuator, while the second intake valve and the second exhaust valve may be coupled to a different valve actuator . Controller 12 may be configured to adjust the phase of intake valve actuator 97 to open first intake valve 30 at a first intake valve timing and open second intake valve 30 at a different second intake valve timing based on engine operating conditions. Two intake valves 31. For example, the first timing may be adjusted relative to the second timing to provide a first, lower pressure to supply cylinder 14 with fresh air and/or recirculated exhaust gas early in the engine cycle (eg, early in the intake stroke). The first intake air is charged, and the first intake air comprising fresh air and/or recirculated exhaust gas is provided to cylinder 14 at a second, higher pressure later in the engine cycle (e.g., later in the same intake stroke in the same engine cycle). Two intake air inflation.

In the same manner, controller 12 may be configured to adjust the phase of exhaust valve actuator 98 to open first exhaust valve 32 and second exhaust valve 33 at particular timings based on engine operating conditions. In one example, the phase of exhaust valve actuator 97 may be adjusted relative to the phase of valve actuator 98 such that the opening and/or closing of intake valves 30 and 31 are coordinated with (or based on) the corresponding exhaust valve 32 and 33 on and/or off. For example, a first exhaust valve may be opened to selectively exhaust (or recirculate) residual exhaust gas and a second exhaust valve may be opened to selectively exhaust blown gas through the turbine to drive a coupled compressor. Exemplary first and second intake and exhaust valve timings are shown in FIG. 5 .

Referring to FIG. 3 , an alternate view 300 of internal combustion engine 10 is shown. Engine 10 is shown with combustion chamber 14 , coolant sleeve 118 and cylinder walls 136 with piston 138 positioned within and connected to crankshaft 140 . Combustion chamber 14 can communicate with intake passage 146 and exhaust passage 148 via respective intake valve 150 and exhaust valve 156 . As previously shown in FIGS. 1-2 , each cylinder 14 of engine 10 may receive an intake air charge along two intake conduits and may expel combustion products along two exhaust conduits. In the illustrated view 300, intake passage 146 and exhaust passage 148 represent the first intake and exhaust conduits to and/or from the cylinders (eg, conduits 43a and 47a of FIG. 2 ), whereas in this The second intake and/or exhaust ducts to and/or from the cylinders are not visible in the view. As also previously shown in FIG. 2 , each cylinder of engine 10 may include two (or more) intake valves and two (or more) exhaust valves coupled to respective intake and exhaust conduits. In the illustrated view 300 , at least one intake valve is shown as an intake poppet valve 150 located at an upper region of the cylinder 14 and at least one exhaust valve is shown as an exhaust poppet valve located at an upper region of the cylinder 14 156.

Intake valve 150 and exhaust valve 156 may be controlled by controller 12 using respective cam actuation systems including one or more cams. Cam actuation systems may utilize changes in one or more of Cam Profile Shift (CPS), Variable Cam Timing (VCT), Variable Valve Timing (VVT) and/or Variable Valve Lift (VVL) systems The valves operate. In the example shown, each intake valve 150 is operated by an intake cam 151 and each exhaust valve 156 is operated by an exhaust cam 153 . The positions of intake valve 150 and exhaust valve 156 may be determined by valve position sensors 155 and 157 , respectively. In alternative embodiments, the intake and/or exhaust valves may be controlled by electronic valve actuation. For example, cylinder 14 may alternatively include intake valves actuated via electronic valves and exhaust valves controlled via cam actuation including CPS and/or VCT systems. In other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system.

In one example, intake cam 151 includes separate and distinct cam lobes that provide a different valve profile (eg, valve timing, valve lift, duration, etc.). Similarly, exhaust cam 153 may include separate and distinct cam lobes that provide a different valve profile (e.g., valve timing, valve lift) for each of the two exhaust valves of combustion chamber 14. program, duration, etc.). Alternatively, exhaust cam 153 may include a common lobe or similar lobe that provides substantially similar valve profiles for each of the two exhaust valves.

For example, a first cam profile of a first intake valve of combustion chamber 14 may have a first amount of lift and a first opening timing and duration. The second cam profile of the second intake valve of combustion chamber 14 may have a second amount of lift and a second opening timing and duration. In one example, the first lift amount may be less than the second lift amount, the first opening timing may be earlier (or earlier) than the second opening timing, and/or the first opening duration may be shorter than the second opening timing. Open duration. Additionally, in some examples, the phases of the first and second cam profiles may be adjusted independently of the phase of the engine crankshaft. Thus the first intake cam profile can be positioned to open the intake valve on the intake stroke of the combustion chamber 14 near TDC so that the first intake valve can open on the intake stroke near TDC and on the intake stroke near BDC closed. On the other hand, the second intake cam profile enables opening of the second intake valve near BDC on the intake stroke. Thus, the timing of the first and second intake valves is capable of separating a first charge of intake air received via a first intake port from a second charge of intake air received via a different second intake port .

In the same way, different cam profiles for different exhaust valves can be used to separate exhaust gas discharged at cylinder pressure from exhaust gas discharged at exhaust pressure. For example, a first exhaust cam profile can open a first exhaust valve after a BDC expansion stroke. In another aspect, the second exhaust cam profile can be positioned to open the second exhaust valve at BDC of the expansion stroke such that the second exhaust valve can open and close before BDC of the expansion stroke. Additionally, the second cam profile can be adjusted in response to engine speed to regulate exhaust valve opening and closing to selectively exhaust blown gases from the combustion chamber. Thus, the timing of the first and second exhaust valves is capable of isolating cylinder blow-in gases from residual gases. While in the examples above the first exhaust valve timing is later in the cylinder cycle than the second exhaust valve timing, it will be appreciated that in alternative examples the first exhaust valve timing could be earlier in the cylinder cycle than Second exhaust valve timing. For example, during surge conditions, the second exhaust valve may open after the first exhaust valve opens.

Heat recovery from the exhaust can be increased by having a portion of the exhaust gas (e.g. high pressure exhaust) flow through the turbine and high pressure exhaust port while the remaining portion of the exhaust gas (e.g. low pressure exhaust gas) flow through the catalyst device and the first exhaust port And at the same time improve the working efficiency of the turbine. By coordinating the timing of the exhaust valves with the timing of the intake valves, a portion of the residual gas can be delivered to provide EGR while another portion drives the turbocharger compressor. Specifically, in one embodiment, the engine can be split into a naturally aspirated portion that operates at low pressure and a supercharged portion that operates at high pressure, thereby providing the various synergistic benefits of EGR and supercharging. Additionally, this configuration enables the engine to operate with a smaller turbine and compressor while producing less turbo lag.

In yet other embodiments, both exhaust valves may be opened simultaneously to provide wastegate-like behavior. Similarly, both intake valves may be opened simultaneously to provide compressor bypass valve like behavior. In this way, the advantages offered by a branched intake manifold can be utilized even in the absence of a branched exhaust manifold. Furthermore, said advantages are provided even in the absence of EGR channels. For example, wastegate-like behavior and compressor bypass valve-like behavior may be achieved regardless of the presence or absence of one or more EGR passages or no EGR passages between the branched intake and branched exhaust.

Exhaust gas sensor 128 is shown coupled to exhaust passage 148 . Sensor 128 may be positioned in the exhaust passage upstream of one or more emission control devices, such as devices 70 and 72 of FIGS. 1-2 . Sensor 128 may be selected from a variety of suitable sensors that provide an indication of the air/fuel ratio of the exhaust gases, such as a linear oxygen sensor or UEGO (universal or wide range exhaust gas oxygen sensor), a dual state oxygen sensor or EGO (as described) , HEGO (Heated EGO), NOx, HC or CO sensor. Downstream emission control devices may include one or more three way catalysts (TWCs), NOx traps, various other emission control devices, or combinations thereof.

Exhaust temperature may be estimated by one or more temperature sensors (not shown) within exhaust passage 148 . Alternatively, exhaust temperature may be inferred based on engine operating conditions (eg, speed, load, air-fuel ratio (AFR), spark retard, etc.).

Cylinder 14 can have a compression ratio, which is the ratio of the volume of piston 138 at bottom dead center to the volume at top dead center. Conventionally, the compression ratio is in the range of 9:1 to 10:1. However, in some examples using different fuels, the compression ratio is increased. For example, this can occur when using higher octane fuels or fuels with higher latent enthalpy of vaporization. The compression ratio is also increased if direct injection is used due to its effect on knock.

In some embodiments, each cylinder of engine 10 may include a spark plug 192 for initiating combustion. Ignition system 190 can provide an ignition spark to combustion chamber 14 via spark plug 192 in response to spark advance signal SA from controller 12 , under select operating modes. However, in some embodiments, spark plug 192 may be omitted, such as where the engine can initiate combustion by auto-ignition or by fuel injection, as is the case with some diesel engines.

In some embodiments, each cylinder of engine 10 may be configured with one or more fuel injectors to provide fuel thereto. As a non-limiting example, cylinder 14 is shown including one fuel injector 166 . Fuel injector 166 is shown coupled directly to cylinder 14 for injecting fuel therein in proportion to the pulse width of the FPW signal received from controller 12 via electronic driver 168 . In this manner, fuel injector 166 provides fuel into combustion cylinder 14 in a manner known as direct fuel injection. Although FIG. 3 shows injector 166 as a side injector, it could also be located on top of the piston, such as near spark plug 192 . This location improves mixing and combustion when running the engine on alcohol-based fuels due to the low volatility of some alcohol-based fuels. Alternatively, injectors may be located on top or near the intake valves to improve mixing. In an alternative embodiment, injector 166 may be a port injector that provides fuel into the intake port upstream of cylinder 14 .

Fuel may be delivered to fuel injector 166 from a high pressure fuel system 8 including a fuel tank, a fuel pump, and a fuel manifold. Alternatively, fuel may be delivered at low pressure by a single stage fuel pump, in which case direct fuel injection timing may be more restricted during the compression stroke than if a high pressure fuel system is used. Additionally, although not shown, the fuel tank may have a pressure transducer/sensor that provides a signal to controller 12 . Fuel tanks in fuel system 8 may hold fuel of different fuel qualities (eg, different fuel compositions). These differences may include different alcohol contents, different octane ratings, different heats of vaporization, different fuel blends and/or combinations thereof, and the like. In some embodiments, fuel system 8 may be coupled to a fuel vapor recovery system that includes a canister for storing refueling and daily fuel vapors. Fuel vapors may be pumped from the canister to engine cylinders during engine operation when pumping conditions are met. For example, pumped vapor may be naturally drawn into the cylinder via the first intake port at or below atmospheric pressure.

The controller 12 shown in FIG. 3 is a microcomputer including a microprocessor unit (CPU) 106, input/output (I/O) ports 108, electronic storage media for executable programs and test values (in this Shown in specific examples are read only memory (ROM) chip 110 ), random access memory (RAM) 112 , keep alive memory (KAM) 114 and a data bus. Storage medium read-only memory 110 can be programmed with computer readable data representing instructions executable by processor 106 for performing the methods and procedures described below as well as variations that are foreseen but not specifically listed. Controller 12 may receive a variety of signals from sensors coupled to engine 10 , in addition to those previously discussed, including: incoming mass air flow (MAF) measurements from mass air flow sensor 122 , incoming mass air flow (MAF) measurements from cooling sleeve 118 coupled to engine coolant temperature (ECT) from temperature sensor 116, pulsed ignition sense signal (PIP) from hall effect sensor 120 (or other type) coupled to crankshaft 140, throttle position (TP) from throttle position sensor , absolute manifold pressure signal (MAP) from sensor 124 , cylinder air-fuel ratio (AFR) from EGO sensor 128 and abnormal combustion from knock sensor and crankshaft acceleration sensor. Engine speed signal RPM may be generated by controller 12 from the pulse ignition sense PIP signal. A manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum or pressure within the intake manifold.

Based on input from one or more of the aforementioned sensors, controller 12 may adjust one or more actuators, such as fuel injector 166, throttle valve 162, spark plug 199, intake/exhaust valves and cams, etc. . The controller may receive input data from various sensors, process the input data, and trigger actuators in response to the processed delivery input based on instructions or code programmed therein corresponding to one or more programs. An exemplary control routine is described herein with reference to FIG. 4 .

Turning now to FIG. 4 , an example routine 400 is shown for delivering a first air charge to an engine cylinder through a first intake port and a second air charge to an engine cylinder through a second parallel but separate intake port. The first and second air charges can have different compositions (e.g. different ratios of fresh air to recirculated exhaust), different pressures (e.g. one at higher boost pressure and the other at lower sub-atmospheric pressure ), different temperatures (e.g. one air charge is heated to a higher temperature and the other air charge is cooled to a lower temperature), etc. Additionally, different air charges may be delivered at different timings to stagger their delivery during a given intake stroke.

In step 402, engine operating conditions may be estimated and/or measured. These may include, for example, ambient temperature and pressure, engine temperature, engine speed, crankshaft speed, transmission speed, battery state of charge, available fuel, fuel alcohol content, catalyst temperature, driver requested torque, and the like.

In step 404 , based on estimated engine operating conditions, an ideal (total) air charge may be determined. This may include determining the amount of fresh intake air, the amount of exhaust gas recirculation (EGR), and the amount of boost. Additionally, a ratio of fresh intake air delivered at or below barometric pressure (BP) relative to fresh intake air delivered at boost pressure may be determined. Similarly, the ratio of EGR delivered at higher pressure (HP-EGR) relative to EGR delivered at lower pressure (LP-EGR) may be determined.

In one example, the ideal (total) air charge may include a greater amount of fresh intake air and a lesser amount of EGR in response to a higher torque request. Additionally, the air charge may include a larger amount of charge fresh intake air and a smaller amount of fresh air at or below BP. In another example, the ideal (total) air charge may include a larger amount of EGR and a smaller amount of fresh intake air while the engine is warming up under moderate to high engine load conditions. Additionally, the air charge may include a larger amount of LP-EGR and a smaller amount of HP-EGR.

Based on the desired total air charge, the program may further determine the first air charge to be delivered to the engine cylinders along the first intake port at a first lower pressure (eg, at or below atmospheric pressure) and the second separate air charge to be delivered to the engine cylinders. The port is charged with a second air delivered to the cylinder at a second higher pressure (eg, boost pressure). Specifically, the first and second air charges may be mixed within the cylinder to provide a desired total air charge. The first air charge delivered along the first intake passage may include fresh air delivered at or below atmospheric pressure, recirculated exhaust gas (LP-EGR), or a mixture of both. Similarly, the second air charge delivered along the second intake port may include fresh air delivered at boost pressure or compressor pressure, recirculated exhaust gas (HP-EGR), or a mixture of both. Various combinations of first and second air charges that may be delivered to the cylinder along the first and second intake ports are further contemplated herein with reference to FIG. 6 .

In step 406 , settings of the first and second EGR valves may be determined based on the ideal air charge. For example, based on the ideal air charge, the first EGR valve in the first EGR passage may be opened an amount such that a first amount of exhaust gas is recirculated from the first exhaust port to the first intake port. Here, the first amount of exhaust gas may be at a first lower pressure (eg, at or below atmospheric pressure) to provide LP-EGR. As another example, based on an ideal air charge, the second EGR valve in the second separate EGR passage may be opened an amount such that a second amount of exhaust gas is recirculated from the separate second exhaust passage to the separate second intake port. airway. As explained above, the second exhaust port may be arranged in parallel with the first exhaust port, the second intake port may be arranged in parallel with the first intake port, and the second EGR passage may be arranged in parallel with the first EGR passage. Parallel, although all channels can be separated from each other. Here, the second amount of exhaust gas may be at a second higher pressure (eg, at boost or compressor pressure) to provide HP-EGR. Specifically the second EGR valve may be opened to route a second amount of exhaust gas from upstream of the turbocharger turbine coupled to the second exhaust passage to downstream of the turbocharger compressor coupled to the second intake passage.

In step 408, based on the ideal air charge, the timing of the first intake valve to deliver the first air charge to the cylinder through the first intake valve coupled to the first intake port and the timing of the first intake valve coupled to the second intake port may be determined. A second intake valve timing at which the second intake valve delivers a second charge of air to the cylinder. In one example, where the first intake valve and the second intake valve are coupled to the intake valve actuator, the valve phasing of the intake valve actuator may be adjusted to open at the timing of the first intake valve The first intake valve and the second intake valve open at a second intake valve timing. Based on engine operating conditions, the first intake valve timing may be adjusted relative to the second intake valve timing. Specifically, the first timing may be adjusted earlier in the engine cycle than the second timing. For example, as shown in Figure 5, the first intake valve timing can be earlier in the intake stroke (i.e., closer to intake stroke TDC), while the second timing can be later in the same intake stroke (i.e., closer to away from intake stroke TDC).

In addition to the first and second intake valve timings, the valve lift of each intake valve and the intake valve opening duration may also be determined. The valve phasing of the intake valve actuator may be adjusted accordingly. In one example, a first intake valve may be opened a first amount of valve lift and a second intake valve may be opened a second, different amount of valve lift. For example, as shown in FIG. 5 , the first amount of valve lift of the first intake valve may be less than the second amount of valve lift of the second intake valve. In another example, a first intake valve may be open for a first duration and a second intake valve may be open for a second, different duration. For example, as shown in FIG. 5 , the first intake valve may be opened for a lesser duration than the second intake valve.

In the same manner, a first exhaust valve timing of a first exhaust valve coupled to a first exhaust port and a second exhaust valve timing of a second exhaust valve coupled to a second exhaust port may be determined. In one example, where a first exhaust valve and a second exhaust valve are coupled to an exhaust valve actuator, the valve phasing of the exhaust valve actuator may be adjusted to open at the timing of the first exhaust valve The first exhaust valve and the second exhaust valve open at a second exhaust valve timing. The first and second exhaust valve timings may be selected based on engine operating conditions. In one example, as shown in FIG. 5 , the first and second exhaust valves may be opened at a common exhaust valve timing. Alternatively, they can be staggered.

The valve phasing of the intake and exhaust valve actuators may also be adjusted such that the timing of the exhaust valve event is coordinated with the timing of the intake valve event. Specifically, the first intake valve timing of the first intake valve may be based on the first exhaust valve timing of the first exhaust valve (eg, the first intake valve timing may be retarded from the first exhaust valve timing a predetermined amount), while the intake valve timing of the second intake valve can be based on the second exhaust valve timing of the second exhaust valve (for example, the second intake valve timing can be derived from the second exhaust valve timing delayed by a predetermined amount).

At 410 , based on the desired air charge and engine operating conditions, settings for air intake throttles coupled to each intake port may be determined. Additionally, fuel injector settings (eg, timing, injection volume, opening duration, etc.) as well as turbocharger settings may be determined. For example, a compressor setting for a turbocharger coupled to the second intake port may be determined based on a desired amount of boost (eg, based on a desired amount of charge air charge).

In step 412 , based on the determined EGR valve setting, the first and second EGR valves may be opened. Specifically, the routine includes opening a first EGR valve in the first EGR passage to recirculate a first amount of exhaust gas at or below atmospheric pressure from the first exhaust port to the first intake port. The routine also includes opening a second EGR valve in the second EGR passage to recirculate a second amount of exhaust gas at compressor pressure (ie, boost pressure) from the second exhaust passage upstream of the turbocharger turbine to the Second intake port downstream of the turbocharger compressor.

In step 414 , the routine includes opening a first intake valve of the first intake port at a first intake valve timing to deliver a first (unboosted) air charge at or below atmospheric pressure to the cylinder. In step 416 , the routine includes opening a second intake valve of the second intake port at a second intake valve timing to deliver a second (boost) air charge at compressor pressure to the cylinder. As such, providing the second charge of charge air includes operating a turbocharger compressor coupled to the second intake port (but not coupled to the first intake port) according to the determined boost setting.

As further shown with reference to FIG. 6 , the first and second air charges may include various combinations of fresh air at varying pressures and recirculated exhaust gas. For example, a first air charge delivered to a cylinder may include a first amount of fresh intake air at or below atmospheric pressure and a first amount of recirculated exhaust gas (LP-EGR), while a second air charge delivered to the cylinder The charge may include a second amount of fresh intake air at boost pressure and a second amount of recirculated exhaust gas (HP-EGR).

In step 418 , the routine includes directly injecting an amount of fuel into the cylinder and mixing the first air charge with the second air charge and the injected fuel within the cylinder. The mixture of the injected fuel and the first and second air charges may then be combusted within the cylinder. In one example, where the first intake air charge includes only recirculated exhaust gas and the second intake air charge includes only fresh air, fresh air and EGR may be delivered separately to the cylinders along separate intake passages, and The air charge can then be initially mixed within the cylinder. The mixed air charge may then be further mixed with injected fuel and combusted within the cylinder. In another example, where the first intake air charge includes only LP-EGR and the second intake air charge includes only HP-EGR, different pressures of recirculated exhaust gas may be delivered separately along separate intake passages to the cylinder, and then the initial mixing in the cylinder. Similarly, in examples where the first intake air charge includes fresh intake air at or below ambient pressure and the second intake air charge includes boosted fresh intake air, fresh air at different pressures may be The air passages are delivered individually to the cylinders, where they are then initially mixed.

In yet another example, where each of the first air charge and the second air charge includes at least some fresh air and at least some recirculated exhaust gas, the first amount of LP-EGR may be The first air charge is mixed with a first amount of fresh air at or below atmospheric pressure in the duct, and a second amount of HP-EGR can be mixed with the second amount of supercharged fresh air in the second intake port The air mixes to form a second air charge. Each air charge is then delivered individually into the engine cylinders and mixed initially within the cylinders rather than earlier within the intake ports. The air-charged mixture is then mixed with the injected fuel in the cylinder and combusted.

In this way, different air charges may be delivered separately but thoroughly mixed within the cylinder to provide a homogeneous cylinder air charge. Engine performance and EGR benefits may be enhanced by allowing homogenization of the air charge within the cylinders to occur. By adjusting the first timing of the first intake valve relative to the second timing of the second intake valve and the timing of the first and second exhaust valves, different air charges can be delivered at different times but can be in the cylinder internal mixing to provide a homogeneous final cylinder air charge.

Turning now to FIG. 5 , map 500 illustrates exemplary intake and exhaust valve timing relative to piston position for an engine cylinder configured to pass through the first intake valve from the first intake port receives a first intake air charge, receives a second intake air charge from a separate second intake port through a different second intake valve, and exhausts cylinder combustion products to each first bank through a first exhaust valve exhaust into a different second exhaust port through the second exhaust valve. By adjusting the first timing of the first intake valve relative to the second timing of the second intake valve and the timing of the first and second exhaust valves, different air charges can be delivered at different times to provide some distribution. layer, but can be mixed within the cylinder to provide a homogeneous final cylinder air charge.

Map 500 shows engine position in crankshaft angles (CAD) along the x-axis. Curve 502 is referenced to its position from top dead center (TDC) and/or bottom dead center (BDC) and further to its position in the four strokes (intake, compression, power and exhaust) of the engine cycle (along the y-axis ) shows the piston position.

During engine operation, each cylinder typically undergoes a four stroke cycle including the intake stroke, compression stroke, expansion stroke and exhaust stroke. During the intake stroke, generally, the exhaust valves close and the intake valves open. Air is introduced into the cylinder through the corresponding intake port, and the cylinder piston moves to the bottom of the cylinder so as to increase the volume inside the cylinder. The point at which the piston is near the bottom of the cylinder and at the end of its stroke (ie, when the combustion chamber is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, the intake and exhaust valves close. The piston moves toward the cylinder head to compress the air in the combustion chamber. The point at which the piston is at the end of its stroke and closest to the cylinder head (eg when the combustion chamber is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means, such as a spark plug, resulting in combustion. During the expansion stroke, the expanding gases push the piston back to BDC. The crankshaft converts the motion of this piston into a rotational torque of the rotating shaft. During the exhaust stroke, the exhaust valves open to release residual combusted air-fuel mixture to the corresponding exhaust port and the piston returns to TDC.

Curve 504 shows the first intake valve timing, lift and duration of the first intake valve (Int_1) coupled to the first port of the engine cylinder, while curve 506 shows the Second intake valve timing, lift and duration of the second intake valve (Int_2) of the second port. Curves 508a and 508b show the second intake valve timing, lift and duration of the second exhaust valve (Exh_2) coupled to the second exhaust port of the engine cylinder, while curves 510a and 510b show the The first exhaust valve timing, lift and duration of the first exhaust valve (Exh_1) of the first exhaust port of the engine cylinder. As detailed above, the first and second inlet ports may be separated from each other but arranged in parallel. Similarly, the first and second exhaust passages may be separated from each other but arranged in parallel. Further, the first intake port may be communicatively coupled to the first exhaust port via a first EGR passage, and the second intake port may be communicatively coupled to the second exhaust port via a second EGR passage.

In the example shown, the first intake valve opens at a first timing (plot 502 ) that is earlier in the engine cycle at a second timing (plot 504 ) when the second intake valve opens. Specifically, the first timing of the first intake valve is closer to intake stroke TDC, just before CAD 2 (eg, at or just before intake stroke TDC). In contrast, the second timing of the second intake valve is retarded from intake stroke TDC, after CAD 2 but before CAD 3 . In this way, the first intake valve may open at or before the start of the intake stroke and may close before the end of the intake stroke, while the second intake valve may open after the start of the intake stroke and may remain open at least until subsequent The compression stroke has started.

In addition, the first intake valve may be opened by a first smaller amount of valve lift L1 at the first timing, and the second intake valve may be opened by a second larger amount of valve lift L2 at the second timing. Additionally, the first intake valve may be opened at a first timing for a first shorter duration D1 and the second intake valve may be opened at a second timing for a second longer duration D2.

In one example, where the first and second intake valves are coupled to an intake valve actuator, the valve phasing of the actuator may be adjusted to open the first intake valve at a first timing and open the intake valve at a second Timing to open the second intake valve. The valve phasing of the actuator may also be adjusted such that the first intake valve is opened by a first amount of valve lift for a first duration and the second intake valve is opened by a second, different amount of valve lift for a second duration. Two duration. While the illustrated example depicts different timings, lifts, and durations for different intake valves, it will be appreciated that in alternative embodiments, the intake valves may have the same amount of valve lift and/or the same opening. duration but opens with staggered timing.

Turning now to the exhaust valves, curves 508a and 510a show a first example of exhaust valve timing where both the first and second exhaust valves (Exh_1, Exh_2) are opened at a common timing, ie starting substantially at Exhaust stroke BDC, at or near CAD 1 , and substantially ends exhaust stroke TDC, at or near CAD 2 . Specifically, in this example, the first and second exhaust valves may operate during the exhaust stroke. Furthermore, in this example, both the first and second exhaust valves are opened by the same amount of lift L3 and for the same duration D3. In the example shown, the lift L3 may have a value smaller than the lift L2 of the intake valve but greater than the lift L1 of the intake valve. In one example, lift L3 may have a value equal to the mean or average of lifts L1 and L2.

Plots 508b and 510b illustrate a second example of exhaust valve timing where the timing of the first and second exhaust valves is staggered. Specifically, the opening of the second exhaust valve is closer to (or at) the power (or expansion) stroke BDC, at or just before CAD1 (for example, at or just before the power stroke BDC), while the opening of the second exhaust valve is The timing is delayed from the power stroke BDC, after CAD1 but before CAD2. In this way, the opening of the second exhaust valve can be at or before the beginning of the exhaust stroke, just as the piston bottoms out at the end of the power stroke, and can close before the end of the exhaust stroke. In contrast, the first exhaust valve may open after the exhaust stroke begins and may remain open at least until a subsequent intake stroke has begun. Furthermore, the second exhaust valve may be opened by a second, smaller amount of valve lift L4, while the first exhaust valve is opened by a first, greater amount of valve lift L5. Additionally, the second exhaust valve may be open for a second shorter duration D4 while the first exhaust valve is open for a first longer duration D5. In the example shown, the first exhaust valve timing is later than the second exhaust valve timing in the engine cycle. In alternative embodiments, however, the first exhaust valve timing may be earlier in the engine cycle than the second exhaust valve timing, such as during surge conditions. In yet other examples, both exhaust valves may be open simultaneously to provide wastegate-like behavior. Similarly, both intake valves may be open simultaneously to provide compressor bypass valve like behavior.

In one example, the cam profile of the second exhaust valve can be adjusted to open and close the second exhaust valve and selectively discharge blown gases of the cylinder into the second exhaust passage during the expansion stroke BDC. On the other hand, the cam profile of the first exhaust valve can be adjusted to open the exhaust valve after the expansion stroke BDC and selectively exhaust remaining residual gases of the cylinder into the first exhaust port.

In one example, where the first and second exhaust valves are coupled to an exhaust valve actuator, the valve phasing of the actuators may be adjusted to open the first exhaust valve at a first timing while at (same or a different) second timing to open the second exhaust valve. The valve phasing of the actuator may also be adjusted to open the first exhaust valve with a first amount of valve lift for a first duration and open the second exhaust valve with a (same or different) second amount of valve lift. Exhaust valve and open (same or different) for a second duration. For example, the valve phasing of the intake valve actuators may be adjusted based on the valve phasing of the exhaust valve actuators so that the staggered intake valve timing (shown by plots 504 , 506 ) and the staggered exhaust valve timing (as shown by curves 508b, 510b) are coordinated. Additionally, the amount of overlap of the intake and exhaust valve timings may be adjusted to adjust the amount of EGR provided to the cylinders. In yet other examples, both exhaust valves may be open simultaneously to provide wastegate-like behavior. Similarly, both intake valves may be open simultaneously to provide compressor bypass valve like behavior. In the same manner, the amount of valve overlap between the exhaust valves may be adjusted based on an ideal wastegate, and the amount of valve overlap between the intake valves may be adjusted based on an ideal compressor bypass.

In this way, different exhaust valve timings are used to separate the exhaust gases released at higher pressures (such as blown exhaust gases in the expanding cylinder before the time the cylinder piston reaches bottom dead center expansion stroke) from lower pressures When the exhaust is released (such as the residual exhaust gas remaining in the cylinder after blowing), it can increase engine efficiency and reduce engine emissions at the same time. Specifically, exhaust energy can be diverted from blown exhaust to one of the two exhaust passages to run the turbocharger turbine (which in turn drives the turbocharger compressor) or to provide higher pressure EGR. Substantially simultaneously, residual gases may be directed to the other of the two exhaust ports to heat the catalyst, thereby reducing engine emissions, or thereby provide lower pressure EGR. In this way, exhaust gas can be used more efficiently than simply directing all of the cylinder's exhaust gas to the turbocharger turbine through a single common exhaust port. In this way, several advantages can be achieved. For example, the average exhaust gas pressure supplied to the turbocharger can be increased to increase turbocharger output. Furthermore, by reducing engine warm-up time, fuel economy can be improved and particulate emissions can be reduced. Additionally, the method can reduce engine emissions because at least a portion of cylinder exhaust gas is directed from the cylinder to the catalyst.

Referring now to FIG. 6 , various examples of intake air charges delivered to the cylinders through the first and second intake ports are shown. Specifically, table 600 lists the first air charge delivered to the cylinder at the first earlier intake valve timing along the first intake port through the first intake valve versus the separate second intake valve along the separate An exemplary combination of a second air charge being delivered to the cylinder by the second intake port of the second intake valve timing at a second late intake valve timing. In this way, the first and second air charges may be delivered separately and then (primarily) mixed within the cylinder with each other and with the directly injected fuel before the mixture is combusted.

In one example, during the first condition (Cond_1 ), the first charge of intake air delivered along the first intake passage may include naturally drawn fresh intake air at or below atmospheric pressure. Meanwhile, the second intake air charge may include pressurized fresh intake air at compressor pressure delivered along the second intake passage. Here, by providing naturally aspirated fresh intake air and supercharged fresh intake air to the engine cylinders via separate intake ports, the naturally aspirated portion of the intake air charge can be introduced without consuming (of the turbocharger) compression work while only the boosted portion of the intake air charge needs to be compressed. In this way, a thermal efficiency gain is advantageously achieved.

In another example, during the second condition (Cond_2), the first intake air charge provided along the first intake passage may include at least some recirculated exhaust gas at or below atmospheric pressure. That is, low-pressure-EGR may be recirculated from the first exhaust port to the first intake port. At the same time, the second intake air charge may include fresh intake air boosted at compressor pressure delivered along the second intake passage.

Here, LP-EGR can be kept out of the compressed air path by providing low pressure EGR and charge fresh intake air via a separate intake port. This provides several advantages. First, the compression work of the turbocharger is not expended to deliver EGR. Therefore, the compression efficiency of the turbocharger is improved. Second, by keeping LP-EGR away from the turbocharger compressor, compressor plugging and fouling related problems due to EGR are reduced. Third, because EGR is not used to dilute the supercharged fresh intake air charge, a temperature advantage is realized that does not require charge air cooler operation to reduce the temperature of the intake air charge. Fourth, by having the boost intake air charge separate from the EGR-based intake air charge, both boost control delay and EGR control delay can be reduced, providing a synergistic advantage. Finally, by dividing the total air charge into a portion delivered through the natural intake intake (i.e., a portion that is not boosted) and a portion delivered through the compressor, the compression work required by the compressor is reduced, thereby providing Advantages of thermodynamic efficiency. As such, this may allow the same compression to be provided by a smaller turbocharger (with a smaller compressor and/or turbine) without compromising boost efficiency while reducing turbo lag.

As another example, during a third condition (Cond_3), the first intake air charge delivered along the first intake port may include recirculated exhaust gas at or below atmospheric pressure and fresh intake air being naturally drawn in air mixture. Accordingly, a first amount of LP-EGR may be mixed with the first amount of fresh intake air and delivered to the cylinders via the first intake port at or below BP. At the same time, the second intake air charge may include fresh intake air at compressor pressure. Here, as in the last example (during Cond_2), compressor clogging can be reduced by providing at least some EGR via an intake port separate from the intake port comprising the compressor, turbocharger and EGR control delays can be reduced, turbocharger and EGR control delays can be reduced, turbocharger Supercharger efficiency, and boost and EGR benefits can be extended to a wider engine operating range.

In yet another example, during the fourth condition (Cond_4), the first intake air charge delivered along the first intake passage may include at least some recirculated exhaust gas at or below atmospheric pressure. At the same time, the second intake air charge may include at least some recirculated exhaust gas at compressor pressure. That is, LP-EGR may be provided through the first intake port while HP-EGR is provided through the second intake port. Here, by providing LP-EGR and HP-EGR to engine cylinders via separate intake ports, the benefits of exhaust gas recirculation can be extended to a wider range of engine speed and/or load conditions. In addition, LP-EGR and HP-EGR can be controlled independently.

In another example, during the fifth condition (Cond_5), the first charge of intake air delivered along the first intake passage may include fresh intake air that is naturally drawn in at or below atmospheric pressure. At the same time, the second intake air charge may include at least some recirculated exhaust gas at compressor pressure. That is, high pressure-EGR (HP-EGR) may be recirculated from a second exhaust passage upstream of the turbocharger turbine to a second intake passage downstream of the turbocharger compressor. Here, by supplying naturally drawn fresh intake air and supercharged EGR to engine cylinders via separate intake ports, dilution of intake air with EGR can be reduced.

In yet another example, during a sixth condition (Cond_6), the first intake air charge delivered along the first intake port may include recirculated exhaust gas at or below atmospheric pressure and naturally aspirated fresh intake air air mixture. At the same time, the second intake air charge may include at least some recirculated exhaust gas at compressor pressure. Thus, a first amount of LP-EGR may be mixed with a first amount of fresh intake air at or below BP and delivered to the cylinders via the first intake port, while HP-EGR is delivered via the second intake port to the cylinder. Here, as in the previous example (Cond_4), by providing LP-EGR and HP-EGR via separate intake ports, the benefits of exhaust gas recirculation can be extended to a wider range of engine speed and/or load conditions.

As yet another example, during the seventh condition (Cond_7), the first intake air charge delivered along the first intake passage may include at least some recirculated exhaust gas at or below atmospheric pressure. Meanwhile, the second intake air charge may include a mixture of recirculated exhaust gas and fresh intake air at compressor pressure. Thus, a second amount of HP-EGR may be mixed with a second amount of fresh intake air at compressor pressure and delivered to the cylinder via the second intake port, while LP-EGR is delivered to the cylinder via the first intake port . Here, as in the previous examples (Cond_4 and Cond_6), by providing LP-EGR and HP-EGR via separate intake ports, the benefits of exhaust gas recirculation can be extended to a wider range of engine speed and/or load conditions.

As yet another example, during an eighth condition (Cond_8), the first intake air charge delivered along the first intake port may comprise a mixture of recirculated exhaust gas and naturally drawn fresh air at or below atmospheric pressure. mixture. Meanwhile, the second intake air charge may include a mixture of recirculated exhaust gas and fresh intake air at compressor pressure. Thus, a first amount of LP-EGR may be mixed with a first amount of fresh intake air at or below BP and delivered to the cylinders via the first intake port, while a second amount of HP-EGR may be delivered at compression Air pressure is mixed with a second quantity of fresh intake air and delivered to the cylinders via a second intake port. Here, by separating the first air charge supplied to the cylinder at a lower first pressure from the second air charge supplied to the cylinder at a higher second pressure via a different intake port, it can be used in a wide range of operating conditions. EGR and boost while allowing better control of EGR and boost.

As another example, during a ninth condition (Cond_9), the first charge of intake air delivered along the first intake passage may include naturally drawn fresh intake air at or below atmospheric pressure. At the same time, the second intake air charge may include a mixture of recirculated exhaust gas and at least some fresh intake air at compressor pressure. Thus, a second amount of HP-EGR can be mixed with a second amount of fresh intake air at compressor pressure and delivered to the cylinder via the second intake port, while naturally aspirated fresh intake air is delivered to the cylinder via the first intake port. delivered to the cylinder. Here, by providing the boosted intake air charge and the naturally aspirated intake air charge via different intake ducts, the naturally aspirated intake air charge can be introduced without expending compression work and at the same time only compressing the turbocharger Work is expended in charging the boost intake air.

Turning now to FIG. 7 , an example routine 700 for reducing turbo lag is depicted. Specifically, the routine illustrates coordinating intake air throttle operation in a first port with turbocharger operation in a second port during a tip-in event to reduce turbo lag. By reducing turbo lag, turbocharger efficiency can be increased and engine performance can be improved. FIG. 8 illustrates example throttle-EGR valve adjustments during tip-in by way of map 800 , as in the FIG. 7 routine.

At step 702, the routine includes confirming a tip-in event. In one example, a tip-in event may be confirmed in response to a driver tipping (or depressing) the accelerator pedal beyond a threshold position. In another example, a tip-in event may be confirmed in response to a driver torque request above a threshold.

In this way, prior to the tip-in event, each engine cylinder already receives a certain amount of recirculated exhaust gas (specifically, LP-EGR) through the first intake port, while via the separate but parallel second intake port Receive fresh intake air. Exhaust gas may have been recirculated at a lower pressure from a first exhaust port coupled in communication with the first intake port downstream of the first air intake throttle via a first EGR passage including a first EGR valve. In response to the tip-in event, at 704 the routine includes increasing the amount of fresh intake air while decreasing the amount of recirculated exhaust gas delivered to the cylinders via the first intake port. Specifically, the procedure includes opening (or increasing the opening amount of) the first air intake throttle in the first intake port to increase the amount of fresh intake air being introduced into the cylinder through the first intake port, while closing is A first EGR valve coupled (or reduced opening thereof) within a first EGR passage between the first intake port and the first exhaust port thereby reducing the amount of exhaust gas recirculated through the first intake port.

When adjusting the air intake throttle and the EGR valve in the first intake port, at step 706, the routine also includes operating a turbocharger compressor coupled to the second intake port during a tip-in period to increase The amount of pressurized fresh intake air that is delivered to the cylinders. Specifically, the engine controller may initiate operation of the turbocharger compressor while simultaneously opening (or increasing the opening amount of) a second air intake throttle coupled in the second intake passage downstream of the compressor to increase the amount delivered The amount of boosted fresh intake air to the cylinders. The controller may also close the second EGR valve included in the second EGR passage coupled between the second intake port and the second exhaust port (or reduce its opening amount) to reduce the flow through the second intake port. The amount of higher pressure exhaust gas that is recirculated. In one example, the first air intake throttle may be gradually opened and the first EGR valve may be gradually closed at a profile based on a compressor speed profile. Adjustment of the first and second air intake throttles and the first and second EGR valves may be for a period of time corresponding to a period of time before the compressor reaches a threshold speed. In one example, the threshold speed may correspond to a speed beyond which turbo lag is reduced, such as a speed at which a compressor's pressure output is greater than ambient (or atmospheric) pressure for a given engine operating condition.

In step 708, it may be determined whether the compressor speed has reached a threshold speed. Alternatively, it may be confirmed (eg by using a timer) whether a predetermined time period corresponding to the time period before the compressor attains a threshold speed has elapsed. If not, the routine may keep the first intake air throttle open and the first EGR valve closed while operating the compressor at 710 . In contrast, if the compressor speed has reached the threshold speed, or if a predetermined period of time has elapsed, then at step 712, after the time period has elapsed, the routine includes reducing fresh air delivered to the cylinder via the first intake port. The amount of intake air while increasing the amount of recirculated exhaust gas delivered to the cylinders via the first intake port. Specifically, the routine includes closing (or reducing the amount of opening) a first air intake throttle in the first intake port to reduce the amount of fresh intake air being introduced into the cylinder through the first intake port, and Simultaneously open the first EGR valve (or increase its opening amount) in the first EGR passage connected between the first intake port and the first exhaust port to increase the amount of exhaust gas recirculated through the first intake port quantity. In one example, the first air intake throttle may be gradually closed and the first EGR valve may be gradually opened at a profile based on a compressor speed profile.

In this way, the cylinder can be filled with fresh intake air via the first intake port while the compressor is accelerated to a speed in the second intake port so that the cylinder can already be filled with fresh intake air when the compressor is at the desired boost speed. filling. In other words, when the compressor is at boost pressure, boosted fresh intake air may be provided to the cylinder via the second intake port while additional fresh air is provided to the cylinder via the first intake port. Thus, turbo lag due to waiting for the compressor to come up to speed before pressurized fresh air can be introduced into the cylinders may be reduced. Afterwards, when the compressor has reached the desired speed, EGR can be phased in through the first and second intake ports (specifically LP-EGR via the first intake port and HP-EGR via the second intake port) thereby eliminating EGR benefits are provided in addition to boost benefits. By reducing turbo lag, turbocharger efficiency is improved and engine performance is increased. By providing both boost and EGR benefits together, a synergistic improvement in engine performance can be achieved.

The steps in FIG. 7 are further clarified through the example in FIG. 8 . Map 800 shows engine torque output during engine operation at plot 802 . The corresponding change in turbocharger compressor speed is shown at plot 804 . Plots 810 and 812 show changes in position of a first air intake throttle and a first EGR valve coupled to a first intake port, respectively, while plots 806 and 808 show changes in position of a first air intake throttle coupled to a second intake port, respectively. The positions of the secondary air intake throttle and the secondary EGR valve vary. As such, only the second intake port may include a turbocharger compressor. Changes in the composition of the first air charge (Air_Int_1 ) delivered to the cylinder through the first intake port due to adjustments to the first EGR valve and throttle are shown at plots 818 and 820 , while plots 814 and 816 show The change in composition of the second air charge (Air_Int_2 ) delivered to the cylinder through the second intake port due to adjustment of the second EGR valve and throttle is shown. Changes in net cylinder air charge (Cyl_aircharge) are shown at plot 822 and plot 824 , respectively. In each of plots 814-824, the solid line represents the fresh air composition of the air charge, while the dashed line represents the EGR composition of the air charge.

Prior to t1, based on engine operating conditions, less torque may be requested. Here, a net cylinder air charge corresponding to a smaller torque output may include a relatively larger amount of EGR (dashed line in plot 824 ) and a relatively smaller amount of fresh air (solid line in plot 822 ). By using EGR under light load conditions, fuel economy benefits and emissions reduction benefits may be realized. A net cylinder air charge delivered to the cylinder prior to t1 may be provided by mixing a first intake air charge delivered along a first intake port with a second intake air charge delivered along a second intake port. Specifically, the first intake air charge may include at or below atmospheric pressure (ie, LP-EGR) provided by opening the first EGR valve (plot 812 ) and the second intake throttle (plot 810 ) corresponding amounts. A larger amount of recirculated exhaust gas (plot 820 ) and a smaller amount of naturally drawn fresh air (plot 818 ). In contrast, the second intake air charge may include fresh air (solid line in plot 814 ) provided by opening the second intake throttle (plot 806 ) while closing the second EGR valve (plot 808 ) and Essentially no EGR (dotted line in plot 816 ).

At t1 , a tip-in event may occur, resulting in a larger torque request. For example, a greater torque output may be requested in response to a vehicle operator depressing an accelerator pedal beyond a threshold position. In response to a tip-in event, the compressor (plot 804 ) may be operated to provide a charge of boosted intake air, while the second intake throttle (plot 806 ) is opened (eg, fully open) to direct boosted fresh air to inside the cylinder. However, the boost air charge is not available until the compressor reaches the threshold speed, causing turbo lag. To reduce turbo lag, while the compressor is accelerating in the second intake port, the first intake air charge delivered along the first intake port can be temporarily adjusted to supercharge the fresh intake air fraction while reducing EGR section (drawings 808-820). Specifically, the first EGR valve (plot 812 ) may be closed while the first intake throttle valve (plot 810 ) is fully opened to increase the amount of naturally aspirated fresh air directed into the cylinder while reducing the delivery to The amount of LP-EGR for the cylinder.

At t2 , when the compressor is at or above the desired threshold speed, a boosted fresh intake air charge may be delivered to the cylinder along the second intake port (plot 814 ). At this point, the amount of fresh air delivered along the first intake port can be reduced by gradually closing the first intake throttle (plot 810 ), while gradually restoring LP by opening the first EGR valve (plot 812 ) -EGR. In this way, as the compressor accelerates in one intake port, fresh air can be drawn into the cylinder through the other intake port to dilute any EGR already present in the cylinder. Thus, when the compressor has been accelerated, the fresh air introduced in the second intake port can be compressed to meet the larger torque demand. Additionally, when the compressor has been ramped up, the compressor can be used to introduce charge fresh air through one intake port while LP-EGR is delivered in parallel to the engine cylinders through the other intake port. In this way, turbo lag can be reduced while providing EGR benefits in addition to boost benefits.

It will be appreciated that in other embodiments, turbo lag may additionally or alternatively be reduced by closing the EGR valve, deactivating the first exhaust valve, and fully opening the second exhaust valve. Thereafter, if EGR is required, one or more EGR valves may be opened to provide the required EGR, as indicated at 808 and 812 above.

Turning now to FIG. 9 , an example routine 900 for adjusting operation of the EGR cooler based on engine operating conditions is shown. Specifically, the program enables an EGR cooler located at the junction of the EGR passage and the intake port (eg the junction of the first EGR passage and the first intake port) to be used for cooling under certain conditions (eg via the first intake air The intake air charge delivered to the cylinders enables the EGR cooler to heat the intake air charge under other conditions.

In step 902, engine operating conditions may be estimated and/or measured. These may include, for example, ambient temperature and pressure, engine temperature, engine speed, crankshaft speed, transmission speed, battery state of charge, available fuel, fuel alcohol content, catalyst temperature, driver requested torque, and the like. At 904 , it may be determined whether heating of the intake air charge is required. In one example, it may be desirable to heat the intake air charge when the engine is not knock limited. For example, if no knock is predicted, the intake air charge may be heated to reduce engine pumping work and improve fuel economy.

If heating is requested, then at step 906, heating conditions may be confirmed. Specifically, it can be confirmed whether all conditions exist to be able to operate the EGR cooler as a heater to heat the intake air charge. For example, when the EGR cooler is a liquid coolant based cooler, it may be confirmed that the coolant temperature is higher than the intake air temperature. In addition, it may be confirmed that knock conditions do not exist (ie, knock does not occur or is predicted). If all heating conditions are met, then at step 908 the routine includes closing the first EGR valve and simultaneously opening the first intake throttle in the first intake port to use the first EGR cooler to heat the The intake air charged into the cylinder. In this way, the intake air charge delivered along the first intake port can be heated prior to being introduced into the cylinders, thereby reducing engine pumping losses and improving engine efficiency. As such, if any or all of the heating conditions are not met, the controller may determine that the EGR cooler cannot be operated as an air charge heater at this time. And the program can end.

If heating of the intake air charge is not required at 904 , it may be determined at 910 whether cooling of the intake air charge is required. In one example, cooling may be used to reduce the temperature of EGR delivered to the cylinders. Cooled EGR may reduce cylinder knock while also providing fuel economy and NOx reduction benefits. If cooling is not required, the program can end. If cooling is required, then at step 912, cooling conditions may be confirmed. Specifically, it may be determined whether all conditions exist to enable operation of the EGR cooler to cool the intake air charge. For example, it can be confirmed that cooling will not cause condensation on the compressor. If all cooling conditions are met, then at step 914 the routine includes opening a second EGR valve in the second intake port and simultaneously closing a second intake throttle in the second intake port to cool the The second intake port is directed to EGR in the intake air charge within the cylinder. Additionally or alternatively, the routine may include opening a first EGR valve in the first intake port while simultaneously closing a first intake throttle in the first intake port to cool the air along the first intake port by using the first EGR cooler. EGR channels the intake air charge that is directed into the cylinders. In this way, the intake air charge may be cooled before being directed into the cylinders, and temperature control of the EGR may be achieved. As such, if any or all of the cooling conditions are not met, the controller may determine that the EGR cooler cannot operate as an air charge cooler at this time, and the routine may end.

In one example, heating the intake air charge may include heating only EGR delivered to the cylinders. For example, when the EGR cooler is located in the recirculation passage (or EGR passage) (as shown in Figures 1-2), the EGR valve can be opened and the EGR cooler can be operated as a heater to heat the EGR and deliver it to The cylinders mix heated EGR with cooler fresh intake air in the intake port before the cylinders. Alternatively, if the EGR cooler is located at the junction of the EGR passage and the intake passage, heating the intake air charge may include heating fresh intake air and/or EGR delivered to the cylinders. For example, the EGR valve may be closed while the EGR cooler is operated as a heater to heat the fresh intake air before being delivered to the cylinders. Alternatively, the EGR valve may be opened and the EGR cooler may be operated as a heater to heat fresh air and EGR, the heated EGR and heated fresh air being mixed within the intake port before being delivered to the cylinders.

In still other examples, one EGR cooler may operate as a cooler and the other EGR cooler as a heater. For example, during a first condition, the engine controller may operate a first EGR cooler within the first intake port to heat a first amount of exhaust gas before recirculating the exhaust gas to the first intake port, and during a second During the condition, the controller may operate a first EGR cooler within the first intake port to cool the first amount of exhaust gas before recirculating the exhaust gas to the first intake port. Also, during the first condition, the engine controller may operate a second EGR cooler in the second intake port to cool a second amount of exhaust gas before recirculating the exhaust gas to the second intake port, while during the second During the condition, the controller may operate a second EGR cooler within the second intake port to heat a second amount of exhaust gas before recirculating the exhaust gas to the second intake port. In this way, the second EGR cooler can be used as a heater only when the compressor is not running and not providing boost.

Additionally, operation of the EGR cooler may be coordinated with operation of a charge air cooler (eg, charge air cooler 56 of FIGS. 1-2 ) located downstream of the turbocharger compressor. For example, a first EGR cooler within the first intake port may be used as a heater to provide a heated intake air charge (including fresh intake air and/or LP-EGR) to cylinders via the first intake port. Simultaneously, a compressor in the second intake passage may be operated to provide a boosted intake air charge and a charge air cooler downstream of the compressor is operated to cool the boosted intake air charge. In this way, heated natural intake air (at or below atmospheric pressure) and cooled charge air can be provided to the cylinders simultaneously. The heated and cooled air charge is then able to mix and burn within the cylinders. Here, by combining and combusting heated and cooled air charges delivered to the cylinders individually and simultaneously, a substantially constant compression temperature may be achieved under varying load conditions, thereby enhancing engine performance.

In this way, split engine intake may be combined with split engine exhaust to deliver different air charges of different compositions and pressures to the cylinders at different timings. Specifically, the naturally aspirated air charge may be introduced separately from the charge air charge to reduce the amount of compression work required. By reducing the amount of work required by the compressor, engine boosting efficiency can be increased even with smaller turbochargers. In another embodiment, EGR may be delivered separately from the pressurized fresh intake air charge. By keeping EGR out of the compressor, compressor plugging and fouling can be reduced while allowing EGR control delay and turbocharger control delay to be reduced. In another embodiment, HP-EGR and LP-EGR may be delivered via separate passages. Here, overall EGR control can be improved while allowing EGR benefits to extend to a wider range of conditions. Furthermore, excessive dilution of air by EGR can be reduced by enabling a second path of undiluted air, particularly when transitioning from a large cylinder air charge to a small cylinder air charge. Together, EGR and boost efficiency can be improved to increase engine performance.

Note that the example control and evaluation routines included here can be used with a variety of system configurations. The specific programs described herein may represent one or more of any number of processing strategies (eg, event-driven, interrupt-driven, multitasking, multithreading, etc.). Likewise, various acts, operations, or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the embodiments described herein, but is merely for convenience of illustration and description. One or more of the illustrated actions, functions or operations may be repeatedly performed depending on the particular strategy being used. In addition, the described operations, functions and/or actions graphically represent code to be programmed into the computer readable storage medium in the control system.

It should be understood that the systems and methods disclosed herein are exemplary in nature and that these specific embodiments or examples are not to be construed as limiting, as many variations are possible. Accordingly, the subject matter of the invention includes all novel and non-obvious combinations of the various systems and methods disclosed herein, and any and all equivalents thereof.

Claims (10)

1. a kind of method for operating engine, including：

Inflated by the first air intake duct to first air of the engine cylinder offer at or below atmospheric pressure, first air Inflation includes the new charge air of the first amount；And

The second air for providing supercharging to the cylinder by single second air intake duct is inflated, and second air inflation includes the The new charge air of two amounts, second air inflation is pressurized via the inlet air compressor driven by exhaust steam turbine.

2. according to the method described in claim 1, wherein first air intake duct is attached to first row air flue, and wherein institute State the second air intake duct and be attached to second row air flue, the inlet air compressor is included in second air intake duct, the row Gas turbine is included in the second row air flue.

3. method according to claim 2, in addition to so that the first air inflation and second air inflation exist Mixed in the cylinder with fuel and in the combustor inner cylinder mixture.

4. according to the method described in claim 1, wherein providing at least some air inflation bag at or below atmospheric pressure Include and open the first inlet valve in first air intake duct in the first inlet valve timing, and at least some pressurizing airs are wherein provided Gas inflation is included in same engine circulation opens second in second air intake duct in the second different inlet valve timings Inlet valve；Engine operating condition is wherein based on, the first inlet valve timing is adjusted relative to the second inlet valve timing.

5. method according to claim 4, in addition to, operate and first inlet valve with phase difference and described The air inlet door actuator of second inlet valve connection, thus the first inlet valve timing open first inlet valve and Second inlet valve is opened in the second inlet valve timing.

6. according to the method described in claim 1, wherein first air inflation further comprises at or below atmospheric pressure The EGR of first amount of power, and wherein described second air inflation includes the EGR of the second amount in boost pressure.

7. according to the method described in claim 1, wherein first air inflation includes the institute at or below atmospheric pressure State the mixture of the new charge air of the first amount and the EGR gas of the first amount, and wherein described second air inflation bag Include the mixture of the new charge air of second amount in boost pressure and the EGR gas of the second amount.

8. method according to claim 2, wherein second air intake duct is parallel with first air intake duct, and wherein The second row air flue and the first row air flue are parallel.

9. a kind of method for operating engine, including：

The first air for conveying subatmospheric power to engine cylinder via the first air intake duct is inflated, first air inflation bag Include the EGR gas of the first amount and the new charge air of the first amount；And

The second air in compressor pressure is conveyed via single second air intake duct to the engine cylinder to inflate, this The inflation of two air includes the EGR gas of the second amount and the new charge air of the second amount.

10. a kind of engine system, including：

Engine cylinder；

Uncompressed air is inflated to the first air intake duct that engine cylinder is communicated to via the first inlet valve；

Compressed air is inflated to the second air intake duct that the cylinder is communicated to via the second inlet valve；

It is connected to second air intake duct and is configured to compress the turbocharger of the air for being transported to cylinder inflation Compressor；

Valve actuator for opening first inlet valve and second inlet valve；And

Control system, it has computer-readable instruction, for：

The phase of the valve actuator is adjusted, so as to open first inlet valve and different second in the first timing Second inlet valve is opened in timing, wherein the uncompressed air inflation is including at least some at or below atmospheric pressure Fresh air and at least some EGR, and wherein described compressed air inflation is including at least some new in compressor pressure Fresh air and at least some EGR.