CN106762185B

CN106762185B - System and method for compensating hexadecane

Info

Publication number: CN106762185B
Application number: CN201611120509.5A
Authority: CN
Inventors: E·库尔茨; D·库赫尔
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2012-02-21
Filing date: 2013-02-07
Publication date: 2020-03-31
Anticipated expiration: 2033-02-07
Also published as: CN106762185A; RU2013105763A; CN103256135B; DE102013202660A1; CN103256135A; RU2614308C2

Abstract

Methods and systems for regulating multiple fuel injections provided to a cylinder during a cycle of the cylinder are disclosed. In one example, the amount of fuel is shifted between fuel injections in response to combustion phasing. Engine intake hydrocarbons and/or carbonaceous particulate matter can be reduced when the cetane of the fuel being combusted changes.

Description

System and method for compensating hexadecane

The name of the application is submitted in 2013, 2 month and 7 days as follows: divisional application of chinese patent application 201310049803.1 for a system and method for compensating for hexadecane.

Cross Reference to Related Applications

This application is a continuation of part of U.S. patent application serial No. 13/291,852 entitled "method for controlling low temperature combustion" filed on 8.11.2011, while U.S. patent application serial No. 13/291,852 is a continuation of U.S. patent application No. 12/900,959 entitled "method for controlling low temperature combustion" filed on 8.10.2010, i.e., now U.S. patent No. 8,051,829, the entire contents of which are incorporated herein by reference for all purposes.

Technical Field

Background

Diesel fuel can be supplied to consumers (customers) at different times of the year with different properties. For example, the additive may be mixed with diesel fuel to improve combustion during cold or warm weather. Moreover, different fuel refiners may treat diesel in slightly different ways, and therefore the properties of diesel fuel may vary slightly between different distributors. One property that may vary between different seasons and different dispensers is the cetane number of the diesel fuel. Diesel with a higher cetane number may advance combustion phase in the engine (e.g., ignition timing relative to crankshaft position), while diesel with a lower cetane number may retard combustion phase in the engine. Changes in combustion phasing can increase engine emissions, such as HC, CO, NOx, fuel consumption, combustion noise, and/or carbonaceous particulate matter. Therefore, it is desirable to compensate for fuels having different cetane numbers than fuels having a nominal cetane number. Fuels with different cetane numbers can be compensated by adjusting the injection start timing; however, simply adjusting the start of injection timing increases engine hydrocarbon emissions and particulate matter.

Disclosure of Invention

The inventors herein have recognized the above disadvantages and have developed a method for operating an engine comprising: combusting a first fuel in the cylinder, the first fuel mixture being ignited by compression ignition; combusting a second fuel in the cylinder, the combustion phase of the cylinder being advanced when the first fuel is combusted compared to when the second fuel is combusted; and adjusting a number of fuel injections provided to the cylinder during a cycle of the cylinder in response to the combustion phase.

By varying the number of injections provided to a cylinder during a cycle of the cylinder or the relative amount of fuel in each injection, variations in cetane that affect combustion phase of a cylinder can be compensated for. For example, during combustion of a nominal cetane fuel, three fuel injections can provide a desired amount of cylinder emissions and combustion noise. However, if the fuel combusted in a cylinder has a lower cetane number than the nominal cetane fuel, the number of fuel injections provided to the cylinder during one cycle of the cylinder may be adjusted (e.g., increased) to compensate for variations in ignition dwell time associated with combusting fuels having a lower cetane number. In other examples, the amount of fuel may be exchanged between fuel pulses provided to the cylinder to compensate for variations in fuel cetane.

In another embodiment, a method for operating an engine, comprises: injecting fuel in at least two fuel injection events during one cycle of the cylinder; and adjusting the amount of fuel between the at least two fuel injection events in response to the combustion phasing of the engine.

In another embodiment, adjusting the amount of fuel between the at least two fuel injection events includes increasing a preceding fuel injection event first amount of fuel and decreasing a following fuel injection event first amount of fuel.

In another embodiment, the method further comprises adjusting the number of fuel injections during the at least two fuel injection events in response to a combustion phase of the engine.

In another embodiment, adjusting the number of fuel injections includes decreasing the number of fuel injections from three fuel injections to two fuel injections.

In another embodiment, adjusting the number of fuel injections includes increasing the number of fuel injections from three fuel injections to four fuel injections

In another embodiment, adjusting the amount of fuel in the at least two fuel injection events occurs during a plurality of cycles of the cylinder.

In another embodiment, an engine system comprises: a compression ignition engine having a combustion chamber; a fuel nozzle that injects fuel directly into the combustion chamber; and a control system having a computer program stored in a non-transitory medium, the computer program including executable instructions to adjust an amount of fuel between a plurality of fuel injections provided to the cylinder via a fuel injector in response to at least combustion phasing of the cylinder, the amount of fuel between the plurality of fuel injections occurring during one cycle of the cylinder, and instructions to limit an amount of fuel transferred from a second fuel injection to a first fuel injection in response to the second fuel injection reaching a minimum fuel injection pulse width, the first fuel injection and the second fuel injection included in the plurality of fuel injections.

In another embodiment, adjusting the amount of fuel between the plurality of fuel injections includes decreasing a first amount of fuel for a preceding fuel injection event and adding the first amount of fuel for a following fuel injection event.

In another embodiment, fuel is transitioned from the second fuel injection to the first fuel injection by increasing the pulse width of the first fuel injection, and further comprising additional executable instructions to stop providing the second fuel injection after the pulse width of the fuel injector reaches a minimum pulse width.

In another embodiment, the amount of fuel between fuel injections is adjusted during multiple cycles of the cylinder.

In another embodiment, the engine system further comprises additional executable instructions that adjust a number of fuel injections provided to the cylinder in response to combustion phasing.

The present invention may provide several advantages. In particular, the method may reduce engine emissions when the engine combusts fuels having different cetane numbers. Furthermore, the method may also be used to reduce engine noise by controlling the rate of heat release during one cycle of the cylinder. Moreover, the method may address fuel injector limitations when fuel quantities are exchanged between different fuel pulses provided to the engine cylinders.

The above and other advantages and features of the present invention will become readily apparent from the following detailed description taken alone or in conjunction with the accompanying drawings.

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

Drawings

FIG. 1 shows a schematic diagram of an engine;

2-6 illustrate signals associated during a condition in which combustion phase of a cylinder changes in response to cetane of fuel combusted in the cylinder; and

7-8 illustrate flow charts of exemplary methods for controlling fuel injection to compensate for fuels having different cetane numbers.

Detailed Description

The invention relates to compensating for combustion of fuels having different cetane numbers. FIG. 1 illustrates one example of a boosted diesel engine in which the methods of FIGS. 7-8 may adjust fuel injection to improve engine emissions and/or reduce combustion noise. 2-6 illustrate examples of simulating fuel injection timing to compensate for combusting fuels having different cetane numbers.

Referring to FIG. 1, an internal combustion engine 10 including a plurality of cylinders, one of which is shown in FIG. 1, is controlled by an electronic engine controller 12. Engine 10 includes a combustion chamber 30 and cylinder walls 32 having a piston 36 disposed therein, and the piston is coupled to a crankshaft 40. Combustion chamber 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. The intake and exhaust valves may each be operated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 may be determined by an intake sensor 55. The position of exhaust cam 53 may be determined by exhaust sensor 57.

Fuel nozzles 66 are shown positioned to inject fuel directly into combustion chamber 30, which is known to those skilled in the art as direct injection. Fuel injector 66 provides liquid fuel in proportion to the pulse width of signal FPW from controller 12. Fuel is provided to fuel injector 66 by a fuel system (not shown) including a fuel tank 95, fuel pump 91, fuel pump control valve 93, and a fuel rail (not shown). The fuel pressure provided by the fuel system may be adjusted by changing a position valve that regulates flow to a fuel pump (not shown). Further, a metering valve may be disposed in or near the fuel rail for closed loop fuel control. The pump metering valve may also regulate fuel flow to the fuel pump, thus reducing fuel pumped to the high pressure fuel pump.

Intake manifold 44 is shown communicating with an optional electronic throttle 62, which electronic throttle 62 adjusts a position of a throttle plate 64 to control air flow from intake plenum 46. Compressor 162 draws air from air intake 42 to supply plenum 46. The exhaust gas rotates a turbine 164 connected to the compressor 162 via a shaft 161. In some examples, a charge air cooler may be provided. Compressor speed may be adjusted by adjusting the position of variable vane control 72 or compressor bypass valve 158. In alternative embodiments, the wastegate 74 may replace the variable vane controller 72 or utilize the wastegate 74 in addition to the variable vane controller 72. The variable vane controller 72 adjusts the position of the variable geometry turbine vanes. When the vanes are in the open position, the exhaust gas may pass through the turbine 164, providing a small amount of energy to rotate the turbine 164. When the vanes are in the closed position, the exhaust gas may pass through and impart increased force on the turbine 164. Alternatively, the wastegate 74 enables exhaust gas to flow around the turbine in order to reduce the energy provided to the turbine. Compressor bypass valve 158 enables compressed air at the outlet of compressor 162 to be returned to the inlet of compressor 162. In this manner, the efficiency of the compressor 162 may be reduced to affect the flow of the compressor 162 and reduce the likelihood of compressor surge.

Combustion begins within combustion chamber 30 when fuel ignites automatically due to piston 36 nearing top-dead-center compression stroke. Universal Exhaust Gas Oxygen (UEGO) sensor 126 may be coupled to exhaust manifold 48 upstream of exhaust device 70. In other examples, the UEGO sensor may be disposed downstream of one or more exhaust aftertreatment devices. Also, in some examples, the UEGO sensor may be replaced with a NOx sensor having both NOx and oxygen sensing elements.

At lower engine temperatures, glow plug 68 may convert electrical energy into heat energy in order to raise the temperature of combustion chamber 30. By increasing the temperature of combustion chamber 30, the cylinder air-fuel mixture may be readily ignited by compression.

In one example, the exhaust 70 may include a particulate filter and a catalyst block. In another example, multiple emission control devices, each having multiple pieces of catalyst, may be used. The exhaust device 70 may include an oxidation catalyst in one example. In other examples, the emissions device may include a lean NOx trap or Selective Catalytic Reduction (SCR) and/or a Diesel Particulate Filter (DPF).

Exhaust gas recirculation may be provided to the engine through an Exhaust Gas Recirculation (EGR) valve 80. EGR valve 80 is a three-way valve that terminates or allows exhaust gas to flow from downstream of exhaust device 70 to a location in the engine intake system upstream of compressor 162. In an alternative embodiment, EGR may flow from upstream of turbine 164 to intake manifold 44. EGR may bypass EGR cooler 85 or, alternatively, EGR may be cooled via passing through EGR cooler 85. In other examples, high and low pressure EGR systems may be provided.

Controller 12 is shown in FIG. 1 as a conventional microcomputer including: a microprocessor unit (CPU)102, input/output ports (I/O)104, Read Only Memory (ROM)106, Random Access Memory (RAM)108, Keep Alive Memory (KAM)110, and a conventional data bus. Controller 12 is shown receiving various signals from a connection to engine 10, including, in addition to those signals mentioned above: engine Coolant Temperature (ECT) from temperature sensor 112 coupled to cooling jacket 114; a position sensor 134 connected to an accelerator pedal 130 for detecting an accelerator position adjusted by a foot 132; a measurement of engine manifold pressure (MAP) from a pressure sensor 121 coupled to intake manifold 44; boost pressure from pressure sensor 122; exhaust oxygen concentration from oxygen sensor 126; an engine position sensor from a Hall effect sensor 118 that detects the position of crankshaft 40; a measurement of air mass entering the engine from a sensor 120 (e.g., a hot wire air flow meter); and a throttle position measurement from sensor 58. Atmospheric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present invention, the engine position sensor 118 generates a predetermined number of equally spaced pulses for each revolution of the crankshaft from which the engine speed (RPM) can be determined.

During operation, each cylinder within engine 10 typically undergoes a four stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, generally, exhaust valve 54 closes and intake valve 52 opens. Air is introduced into combustion chamber 30 via intake manifold 44 and piston 36 moves to the bottom of the cylinder to increase the volume within combustion chamber 30. The position at which piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when combustion chamber 30 is at its largest volume) is typically referred to by those skilled in the art as Bottom Dead Center (BDC). During the compression stroke, intake valve 52 and exhaust valve 54 are both closed. Piston 36 moves toward the cylinder head to compress the air within combustion chamber 30. The position at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at a minimum volume) is commonly referred to by those skilled in the art as Top Dead Center (TDC). In a process hereinafter referred to as injection, fuel is drawn into the combustion chamber. In some examples, fuel may be injected into a cylinder multiple times during a single cylinder cycle. In a process hereinafter referred to as ignition, the injected fuel is ignited by compression ignition, resulting in combustion. During the expansion stroke, the expanding gases push the piston back to BDC. Crankshaft 40 converts piston movement into rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48 and the piston returns to TDC. It should be noted that the above is described merely as an example, and that the opening and/or closing timing of the intake and exhaust valves may be varied, for example, to provide positive or negative valve overlap, late intake valve closing, or various other examples. Also, in some examples, a two-stroke cycle may be used instead of a four-stroke cycle.

Accordingly, the system of fig. 1 provides an engine system comprising: a compression ignition engine having a combustion chamber; a fuel nozzle that injects fuel directly into the combustion chamber; and a control system having a computer program stored in a non-transitory (non-transient) medium, the computer program including executable instructions to adjust an amount of fuel between a plurality of fuel injections provided to the cylinder during a cycle of the cylinder in response to a combustion phase of the cylinder, and instructions to adjust a fuel injection amount of a first fuel injection when the amount of fuel of a second fuel injection reaches a minimum fuel injection pulse width of a fuel injector providing the plurality of injections, the first and second fuel injections included in the plurality of fuel injections. In this manner, the system may account for a minimum fuel injection pulse width when providing multiple fuel injections to the cylinder during a cylinder cycle.

The engine system includes: adjusting the amount of fuel between the plurality of fuel injections includes decreasing a first amount of fuel for a preceding fuel injection event and adding the first amount of fuel for a following fuel injection event. The engine system further includes: adjusting the fuel injection quantity of the first fuel injection includes increasing the fuel quantity of the first fuel injection and further includes additional executable instructions to stop providing the second fuel injection after the pulse width of the fuel injector reaches the minimum pulse width. In some examples, the engine system includes adjusting an amount of fuel between the plurality of fuel injections during a plurality of cycles of the cylinder. The engine system further includes additional executable instructions to adjust a number of fuel injections provided to the cylinder in response to the combustion phase.

Referring to FIG. 2, FIG. 2 shows the relevant signals during a time when the combustion phase of a cylinder is advanced and then retarded. The signals and sequence of fig. 2 may be provided by the system shown in fig. 1 that performs the methods of fig. 7 and 8. The engine is operated at substantially the same speed and torque requirements for all cylinder cycles shown, so the fuel adjustments and the effects of the fuel adjustments can be shown under similar conditions. Moreover, the fuel timing and quantity are for illustrative purposes only and are not limiting as to the scope or breadth of the invention.

The first plot from the top of fig. 2 represents cylinder stroke of one cylinder of the engine. The X-axis is divided into a series of segments, each representing the cylinder stroke that cylinder number one is performing as time progresses from the left to the right side of the graph. The exhaust stroke is abbreviated as EXH, while the intake, compression and expansion strokes are abbreviated as INT, COMP and EXP, respectively. At vertical time mark T₁-T₄In between, the interruption in time is indicated by the SS mark along the X-axis. The interruption in time may be over a period of multiple cylinder cycles or over an extended period of time. Thus, FIG. 2 shows the course of the varying signals over time or during a cylinder cycle.

The second plot from the top of FIG. 2 represents fuel injection timing during a cylinder cycle. Pulse width 250-254 varies across a width and represents the amount of fuel injected in the pulse, the wider the pulse, the greater the amount of fuel injected into the cylinder during the pulse. The number indicates the position of ignition in the cylinder. It should be noted that when ignition occurs before the end of the last fuel injection, an increase in particulate matter may occur because the injected fuel has less time to mix in the cylinder.

The third plot from the top of FIG. 2 represents the fuel pressure of the fuel injected into the cylinder at the timing shown. The Y-axis represents fuel pressure, and the fuel pressure increases in the direction of the Y-axis arrow. The X-axis represents time and time increases from the left to the right of the graph.

The fourth plot from the top of fig. 2 represents the desired combustion phase for cylinder number one. The combustion phase advances along the Y-axis in the direction of the ADV arrow. The combustion phase is retarded in the RET direction along the X-axis. The X-axis represents time and time increases from the left to the right of the graph.

The fifth plot from the top of fig. 2 represents the actual combustion phase for cylinder number one. The combustion phase advances along the Y-axis in the direction of the ADV arrow. The combustion phase is retarded in the RET direction along the X-axis. The X-axis represents time and time increases from the left to the right of the graph.

At T₀And T₁The desired combustion phase for cylinder number one is toward the retarded range and the actual combustion phase substantially matches the desired combustion phase. The fuel pressure is also at a lower level. Although not shown, the fuel injection pulse is such as at time T₁And T₂The timing in between shows, and the fuel cetane number is a nominal cetane number, e.g., 45.

At T₁And T₂The desired combustion phase is maintained at and during time T₀The same levels are shown. Three fuel injections 250-254 are injected during the compression stroke of cylinder number one. The amount of fuel in each of the three fuel injections 250-254 is substantially equal. It should also be noted that at time T₁And T₂Fuel injection quantity and pressure and time T in between₁The same as before. The duration of the fuel injection time is indicated at 202. The fuel pressure is also at a lower value. As indicated by the asterisk, combustion occurs shortly after the third fuel pulse 254. And time T₁The previous actual combustion phase is advanced compared to the actual combustion phase. In this example, the cetane number of the fuel due to combustion is from time T₀To T₁As a change, combustion phase is advanced. In this example, the sum hasA given cetane number of fuel increases compared to the cetane number. The fuel cetane number may change when the engine-running vehicle is refueled. Thus, the increased fuel cetane number advances the actual combustion phase away from the desired combustion phase.

At time T₂And T₃In between, the fuel injection timing is adjusted and the fuel injection pressure is increased. Specifically, a portion of the amount of fuel in the preceding or first fuel pulse 250 is transferred to the following or third fuel pulse 254. In this manner, the duration of pulse 254 increases and the duration of pulse 250 decreases. Removing an amount of fuel from the preceding injection and adding the same amount of fuel to the late injection as was removed from the preceding injection delays combustion in that cylinder even for fuels with a higher cetane number. FIG. 2 also shows when the start of injection is held for fuel pulse 250. Also, the amount of fuel injected in the duration 204 is the same as that injected in the duration 202. Further, the duration of the time of fuel injection may be substantially maintained to provide for at time T₁The same ignition delay (dwell) before (e.g., at the time of ignition after the end of the previous fuel injection). The fuel injection pressure also increases, thus improving mixing of fuel and air in the cylinder for the late injection pulse 254. It can be seen that at time T₂And T₃The actual combustion phase therebetween is retarded in response to the fuel pulse adjustment and is shifted toward the desired combustion phase.

At time T₃And T₄In between, the fuel injection timing is further adjusted and the fuel injection pressure is increased. Specifically, the fuel pulse width of the first fuel pulse 250 reaches a minimum pulse width (e.g., the shortest fuel pulse in which the amount of fuel injected may be repeated to a desired extent) as fuel moves from the preceding fuel pulse 250 to the following fuel pulse 254. Fuel is then transferred from the middle fuel pulse 252 to the late fuel pulse 254 to further retard combustion phase. Removing a certain amount of fuel from the middle injection and adding the same amount of fuel as removed from the middle injection to the late injection for the injection having a higher cetane numberThe fuel is also used to retard combustion in the cylinder. The ignition start time is also maintained for fuel pulse 250. Also, the amount of fuel injected at duration 206 is the same as that injected at duration 202. Further, the duration of the time of fuel injection may be substantially maintained to provide for at time T₁The same ignition delay before. The actual combustion phasing and the asterisk are shown to be further retarded. The fuel injection pressure is also increased so that mixing of fuel and air in the cylinder for the late fuel injection pulse 254 is improved. It can be seen that at time T₃And T₄The combustion phase therebetween is further retarded in response to the fuel pulse adjustment.

At time T₄After that, the fuel injection timing is further adjusted and the fuel injection pressure is increased. Specifically, the middle fuel pulse width is cancelled after the second fuel pulse 252 reaches a minimum pulse width (e.g., the shortest fuel pulse where the amount of fuel injected may be repeated to a desired extent), and further combustion phase retard is desired. The portion of fuel removed from the middle fuel pulse 252 is moved to the early fuel pulse 250 and the amount of fuel remaining from the middle fuel pulse 252 is transferred to the late fuel pulse 254. The actual fuel phase and the asterisk are shown to be further retarded. If additional combustion phase delay is desired to match the actual combustion phase to the desired combustion phase, the fuel in the early fuel pulse can be transferred to the late fuel pulse 254. When the early fuel pulse 250 reaches a minimum fuel injector pulsewidth and additional combustion phase delay is desired, the early fuel pulse 250 may transition to the late fuel pulse 254. The amount of fuel injected during duration 208 is the same as that injected during duration 202.

In this manner, the amount between fuel injections provided to the cylinder during a cylinder cycle may be adjusted with respect to the number of combustion events to retard the combustion phase of the cylinder when the combustion phase of the cylinder is advanced further than desired. And at T₁And T₄The start of injection time is maintained for fuel injection pulse 250 during each cylinder cycle shown in between. Also, fuel injection pressure may be increased to improve air-fuel in the cylinderMixing, and therefore particulate matter can be reduced when combustion phase is retarded.

The sequence of fig. 3-6 shows the same signals as shown in fig. 2. Accordingly, common signals and sequence parts between the figures are not repeated for the sake of brevity.

Referring now to FIG. 3, FIG. 3 shows the relevant signals during a certain time when the combustion phase of a cylinder is advanced and then retarded. The signals and sequence of fig. 3 may be provided by the system shown in fig. 1 that performs the methods of fig. 7-8. The engine is operated at substantially the same speed and torque request for all cylinder cycles shown, so the fuel adjustments and the effects of the fuel adjustments can be shown under similar conditions.

At T₀And T₁The desired combustion phase for cylinder number one is toward the retarded range and the actual combustion phase substantially matches the desired combustion phase. The fuel pressure is also at a lower level. Although not shown, the fuel injection pulse is such as at time T₁And T₂The timing in between shows, and the fuel cetane number is the nominal cetane number.

At T₁And T₂The desired combustion phase is maintained as in time T₀The same levels are shown. Three fuel injections 350-354 are injected during the compression stroke of cylinder number one. The amount of fuel per each of the three fuel injections 350-354 is substantially equal. It should also be noted that at time T₁And T₂Fuel injection quantity and pressure and time T in between₁The same as before. The duration of the fuel injection time is indicated at 302. The fuel pressure is also at a lower value. As indicated by the asterisk, combustion occurs shortly after the third fuel pulse 354. And time T₁The previous actual combustion phase is advanced compared to the actual combustion phase. In this example, the cetane number of the fuel due to combustion is from time T₀To T₁As a change, combustion phase is also advanced. Thus, the increased cetane number of the fuel advances the actual combustion phase away from the desired combustion phase.

At time T₂And T₃In between, the fuel injection timing is adjusted and the fuel injection pressure is increased. Specifically, a portion of the amount of fuel in the early or first fuel pulse 350 is transferred to the late or third fuel pulse 354. Also, removing an amount of fuel from the early injection and adding the same amount of fuel to the late injection as was removed from the early injection can retard combustion in the cylinder even with a higher cetane number of the fuel. Also, the amount of fuel injected during duration 304 is the same as that injected during duration 302. The fuel injection pressure also increases, thus improving the mixing of fuel and air in the cylinder for the late injection pulse 354. It can be seen that at time T₂And T₃The actual combustion phase therebetween is retarded in response to the adjustment of the fuel phase and is shifted toward the desired combustion phase.

At time T₃And T₄In between, the fuel injection timing is further adjusted and the fuel injection pressure is increased. Specifically, the fuel pulse width of the first fuel pulse 350 reaches a minimum pulse width as fuel moves from the preceding fuel pulse 350 to the following fuel pulse 354. Fuel is also transferred from the middle fuel pulse 352 to the late fuel pulse 354 to further retard the combustion phase of the cylinder. Removing an amount of fuel from the middle injection and adding the same amount of fuel to the late injection as removed from the middle injection also serves to retard combustion in the cylinder for fuels with higher cetane numbers. The time at which ignition begins may also be retarded in some examples for early and mid fuel pulses as shown at 310. Also, the amount of fuel injected at duration 306 is the same as that injected at duration 302. The actual combustion phasing and the asterisk are shown to be further retarded. The fuel injection pressure also increases. It can be seen that at time T₃And T₄The combustion phase therebetween is further retarded in response to the fuel pulse adjustment.

At time T₄After that, the fuel injection timing is further adjusted and the fuel injection pressure is increased. Specifically, the preceding pulse width is cancelled after the second fuel pulse 352 reaches the minimum pulse width and further combustion phase retard is desired. From the beginningThe portion of fuel that the fuel pulse 350 cancels is moved to the middle fuel pulse 352 and the remaining amount of fuel is transferred from the early fuel pulse 350 to the late fuel pulse 354. The actual fuel phase and the asterisk are shown to be further retarded. If additional combustion phase delay is desired to match the actual combustion phase to the desired combustion phase, the fuel of the middle fuel pulse may be transferred to the late fuel pulse 354. The injection start time is delayed by eliminating the preceding or most preceding pulse width. An additional amount of delayed SOI is shown at 312. When the intermediate fuel pulse 35 reaches the minimum fuel nozzle pulsewidth and additional combustion phase delay is desired, all of the fuel remaining in the intermediate fuel pulse 352 may be transferred to the late fuel pulse 354. The amount of fuel injected at duration 308 is the same as that of duration 302.

In this manner, when the combustion phase of a cylinder is advanced more than desired, the amount of fuel between fuel injections provided to the cylinder during a cylinder cycle may be adjusted over several combustion events to retard the combustion phase of the cylinder. Also, the timing of start of injection may be delayed for both the early and middle fuel injections. Further, fuel injection pressure may be increased to improve air-fuel mixing in the cylinder, and thus particulate matter may be reduced when combustion phase is retarded.

Referring now to FIG. 4, FIG. 4 shows the relevant signals during a certain time when the combustion phase of the cylinder is retarded and then advanced. The signals and sequence of fig. 4 may be provided by the system shown in fig. 1 that performs the methods of fig. 7-8. The engine is operated at substantially the same speed and torque requirements for all cylinder cycles shown, so the fuel adjustments and the effects of the fuel adjustments can be shown under similar conditions.

At T₀And T₁The desired combustion phase for cylinder number one is toward the advanced range and the actual combustion phase substantially matches the desired combustion phase. The fuel pressure is also at a higher level. Although not shown, the fuel injection pulse is such as at time T₁And T₂The timing in between, and the fuel cetane number isNominal cetane number.

At T₁And T₂The desired combustion phase is maintained at and during time T₀The same levels are shown. The three fuel injections 450-454 are injected during the compression stroke of cylinder number one. The amount of fuel for each of the three fuel injections 450-454 is substantially the same. The duration of the fuel injection time is indicated at 402. The fuel pressure is also at a higher value. As indicated by the asterisk, combustion retard occurs after the third fuel pulse 454. And time T₁The previous actual combustion phase is retarded compared to the actual combustion phase. In this example, the cetane number of the fuel due to combustion is from time T₀To T₁The combustion phase is also retarded, varying. Thus, the reduced cetane number of the fuel retards the actual combustion phase away from the desired combustion phase.

At time T₂And T₃In between, the fuel injection timing is adjusted and the fuel injection pressure is reduced. Specifically, a portion of the amount of fuel in the late or third fuel pulse 454 is transferred to the early or first fuel pulse 450. And the fuel injection end time is kept unchanged. Removing an amount of fuel from the late injection and adding the same amount of fuel to the first injection as was removed from the late injection advances combustion in the cylinder even for fuels with lower cetane numbers. Also, the amount of fuel injected during duration 404 is the same as that injected during duration 402. The fuel injection pressure is also reduced since less fuel mixing may be desired when less fuel is injected late in the cylinder cycle. It can be seen that at time T₂And T₃The actual combustion phase therebetween is advanced in response to the adjustment of the fuel pulse and moved toward the desired combustion phase.

At time T₃And T₄In between, the fuel injection timing is further adjusted and the fuel injection pressure is reduced. Specifically, as fuel moves from the late fuel pulse 454 to the early fuel pulse 450, the fuel pulse width of the late fuel pulse 454 reaches a minimum pulse width. Fuel is also transferred from the intermediate fuel pulse 452 to the prior fuel pulse 450 to proceed furtherAdvancing the combustion phase of the cylinder. Removing an amount of fuel from the middle injection and adding the same amount of fuel to the previous injection as was removed from the middle injection also serves to advance combustion in the cylinder for fuels with lower cetane numbers. Also, the amount of fuel injected at duration 406 is the same as that injected at duration 402. The actual combustion phasing and the asterisk are shown to be further advanced. The fuel injection pressure is also reduced. It can be seen that at time T₃And T₄The combustion phase therebetween is further advanced in response to the fuel pulse adjustment.

At time T₄After that, the fuel injection timing is further adjusted and the fuel injection pressure is decreased. Specifically, intermediate pulse width 452 is cancelled and further combustion phase advance is desired after intermediate fuel pulse 452 reaches a minimum pulse width. The portion of fuel removed from the middle fuel pulse 452 is moved to the late fuel pulse 454 and the amount of fuel remaining from the middle fuel pulse 452 is transferred to the early fuel pulse 450. The actual fuel phase and the asterisk are shown to be further advanced. If additional combustion phase advance is desired to match the actual combustion phase to the desired combustion phase, the fuel in the late fuel pulse 454 may be transferred to the early fuel pulse 450. The end of injection time is maintained by eliminating the intermediate fuel pulse width. When the late fuel pulse 454 reaches the minimum fuel injection pulse width, all of the fuel remaining in the late fuel pulse 452 may be transferred to the early fuel pulse 450. The amount of fuel injected during duration 408 is the same as that injected during duration 402.

In this manner, the amount of fuel between multiple fuel injections provided to a cylinder during a cylinder cycle may be adjusted over several combustion events to advance the combustion phase of the cylinder when the combustion phase of the cylinder is retarded further than desired. Further, the fuel injection pressure may be reduced to improve engine efficiency.

Referring now to FIG. 5, FIG. 5 shows the relevant signals when the combustion phase of a cylinder is retarded and then advanced during a certain time. The signals and sequence of fig. 5 may be provided by the system shown in fig. 1 that performs the methods of fig. 7-8. The engine is operated at substantially the same speed and torque requirements for all cylinder cycles shown, so the fuel adjustments and the effects of the fuel adjustments can be shown under similar conditions.

At T₀And T₁The desired combustion phase for cylinder number one is toward the advanced range and the actual combustion phase substantially matches the desired combustion phase. The fuel pressure is also at a higher level. Although not shown, the fuel injection pulse is such as at time T₁And T₂The timing in between is shown, and the fuel cetane number is the nominal cetane number.

At T₁And T₂The desired combustion phase is maintained at and during time T₀The same levels are shown. Three fuel injections 550-554 are injected during the compression stroke of cylinder number one. The fuel quantities of each of the three fuel injections 550-554 are substantially the same. The duration of the fuel injection time is indicated at 502. The fuel pressure is also at a higher value. As indicated by the asterisk, combustion retard occurs after the third fuel pulse 554. And time T₁The previous actual combustion phase is retarded compared to the actual combustion phase. In this example, the cetane number of the fuel due to combustion is from time T₀To T₁The combustion phase is also retarded, varying. Thus, the reduced cetane number of the fuel retards the actual combustion phase away from the desired combustion phase.

At time T₂And T₃In between, the fuel injection timing is adjusted and the fuel injection pressure is reduced. Specifically, a portion of the amount of fuel in the late or third fuel pulse 554 is transferred to the early or first pulse 550. Also, in some examples, the late fuel injection time may be delayed. Also, removing a certain amount of fuel from the late injection and adding the same amount of fuel as removed from the late injection to the first injection can advance combustion in the cylinder even for fuels with a lower cetane number. Also, the amount of fuel injected in duration 504 is the same as that injected in duration 502. Because of the time of making the fuel in the steamThe fuel injection pressure is also reduced as the air is mixed in the cylinder. It can be seen that at time T₂And T₃The actual combustion phase therebetween is retarded in response to the adjustment of the fuel pulse and is shifted toward the desired combustion phase.

At time T₃And T₄In between, the fuel injection timing is further adjusted and the fuel injection pressure is reduced. Specifically, after the fuel pulse width of the late fuel pulse 454 reaches the minimum pulse width, the late fuel pulse width is cancelled. Fuel is transferred from the late fuel pulse 554 to the middle fuel pulse 552 and the early fuel pulse 550. Removing an amount of fuel from the late fuel injection 554 and adding the same amount of fuel as removed from the late fuel injection 554 to the early middle fuel injection 552 also serves to advance combustion in the cylinder for fuels with lower cetane numbers. The end of injection time may also be advanced by eliminating the late fuel injection as shown at 510. The actual combustion phasing and the asterisk are shown to be further advanced. The fuel injection pressure is also reduced. It can be seen that at time T₃And T₄The combustion phase therebetween is further advanced in response to the fuel pulse adjustment.

At time T₄After that, the fuel injection timing is further adjusted and the fuel injection pressure is decreased. Specifically, the early fuel pulse is expanded by the addition of fuel to it from the middle fuel pulse 552. The actual fuel phase and the asterisk are shown to be further advanced. The end of injection is also advanced further as shown at 512. If additional combustion phase advance is desired to match the actual combustion phase to the desired combustion phase, the fuel in the middle fuel pulse 552 may be transferred to the early fuel pulse 550. When the intermediate fuel pulse 552 reaches the minimum fuel injection pulse width, all of the fuel remaining in the intermediate fuel pulse 552 may be transferred to the preceding fuel pulse 550. The amount of fuel injected during duration 508 is the same as that injected during duration 502.

Referring now to FIG. 6, FIG. 6 shows the relevant signals when the combustion phase of a cylinder is retarded and then advanced during a certain time. The signals and sequence of fig. 6 may be provided by the system shown in fig. 1 that performs the methods of fig. 7-8. The engine is operated at substantially the same speed and torque requirements for all cylinder cycles shown, so the fuel adjustments and the effects of the fuel adjustments can be shown under similar conditions.

At T₁And T₂The desired combustion phase is maintained at and during time T₀The same levels are shown. Three fuel injections 650-654 are injected during the compression stroke of cylinder number one. The amount of fuel for each of the three fuel injections 650-654 is substantially the same. The duration of the fuel injection time is indicated at 602. The fuel pressure is also at a higher value. As indicated by the asterisk, combustion retard occurs after the third fuel pulse 654. And time T₁The previous actual combustion phase is retarded compared to the actual combustion phase. In this example, the cetane number of the fuel due to combustion is from time T₀To T₁The combustion phase is also retarded, varying. Thus, the reduced cetane number of the fuel retards the actual combustion phase away from the desired combustion phase.

At time T₂And T₃In between, the fuel injection timing is adjusted and the fuel injection pressure is reduced. Specifically, a portion of the amount of fuel in the late or third fuel pulse 654 is transferred to the early or first pulse 650. Also, the late fuel injection time may be delayed in some examples. Also, fromRemoving an amount of fuel in the post injection and adding the same amount of fuel to first injection 650 as was removed from the post injection can advance combustion in the cylinder even for fuels with a lower cetane number. Also, the amount of fuel injected in duration 604 is the same as that injected in duration 602. The fuel injection pressure is also reduced due to the time to mix fuel with air in the cylinder. It can be seen that at time T₂And T₃The actual combustion phase therebetween is advanced in response to the adjustment of the fuel pulse and is shifted toward the desired combustion phase.

At time T₃And T₄In between, the fuel injection timing is further adjusted and the fuel injection pressure is reduced. Specifically, a portion of intermediate fuel pulse 652 is transferred to new fuel pulse 656 that precedes prior fuel pulse 650. The number of fuel pulses increases in response to the fuel cetane number. Removing an amount of fuel from the middle fuel pulse 652 and adding the same amount of fuel to the new fuel injection 656 as was removed from the middle fuel injection 652 also serves to advance combustion in the cylinder for fuels with lower cetane numbers. The fuel injection pressure is also reduced.

At time T₄After that, the fuel injection timing is further adjusted and the fuel injection pressure is decreased. Specifically, the fuel in the middle fuel pulse 652 reaches a minimum pulse width and then transitions from the original prior fuel pulse 650 to the new pulse 656. If further combustion phase advance is desired, fuel from intermediate fuel pulse 652 can be added to fuel pulse 656 and intermediate pulse 652 can be discarded (drop). When the intermediate pulse 653 is aborted, the post-pulse 654 is held to maintain the ignition dwell time (e.g., the amount of time from the last fuel pulse to when ignition occurred). The actual fuel phase and the asterisk are shown to be further advanced. The amount of fuel injected in duration 608 is the same as that injected for

durations

602, 604, and 606.

Referring now to fig. 7 and 8, fig. 7 and 8 illustrate a method for compensating for a combustion fuel having a higher or lower cetane number than the rated cetane number. The methods of fig. 7 and 8 may be performed in the system shown in fig. 1 by computer readable instructions.

At 702, method 700 determines operating conditions including combustion phasing. Combustion phase may be determined by pressure sensors in the engine cylinders, accelerator output, or from crankshaft position. Other operating conditions may include, but are not limited to, ambient temperature, engine torque demand, and engine speed. Method 700 proceeds to 704 after combustion phase is determined.

At 704, method 700 judges whether or not the actual combustion phase is advanced from the desired combustion phase. In one example, the actual combustion phase is subtracted from the desired combustion phase to determine whether the actual combustion phase is advanced from the desired combustion phase by more than a threshold amount. For example, if the actual combustion phase is advanced by 20 crankshaft degrees from top dead center of the compression stroke of the cylinder, and the desired combustion phase is advanced by 15 crankshaft degrees from top dead center of the compression stroke of the cylinder, and the threshold is 2 crankshaft degrees, method 700 proceeds to 730. If the actual combustion phase is advanced more than the threshold amount from the desired combustion phase, method 700 proceeds to 730. Otherwise method 700 proceeds to 706.

At 706, method 700 judges whether or not the actual combustion phase is retarded from the desired combustion phase. In one example, the actual combustion phase is subtracted from the desired combustion phase to determine whether the actual combustion phase is retarded more than a threshold amount from the desired combustion phase. For example, if the actual combustion phase is advanced 5 crankshaft degrees from compression stroke top dead center of the cylinder, while the desired combustion phase is advanced 15 crankshaft degrees from compression stroke top dead center of the cylinder, and the threshold is 2 crankshaft degrees, method 700 proceeds to 708. If the actual combustion phase is retarded more than a threshold amount from the desired combustion phase, method 700 proceeds to 708. Otherwise, method 700 proceeds to exit.

At 708, method 700 judges whether or not a fuel injection end timing (EOI) is maintained. In one example, EOI timing may be based on engine speed and load. If the engine speed and load are within the predetermined ranges, the EOI is maintained, as shown in FIG. 4, and method 700 proceeds to 710. Otherwise, method 700 proceeds to 780.

At 710, method 700 increases fuel in a prior fuel injection event, where fuel is injected multiple times in one cylinder cycle. The amount of fuel in the late fuel injection is reduced by the amount of fuel added to the early fuel injection. The fuel pressure may be reduced by adjusting the voltage supplied to the fuel pump or by adjusting a valve that controls the fuel flow to the fuel injection pump. Method 700 proceeds to 712 after a fuel pulse supplied to a cylinder during a cycle of the cylinder is adjusted to advance combustion phase of the cylinder.

At 712, method 700 judges whether or not the actual combustion phase is within the range of the desired combustion phase. If so, method 700 proceeds to exit. If false, method 700 proceeds to 714.

At 714, method 700 judges whether or not the late fuel injection of the plurality of fuel injections provided to the cylinder is at a minimum pulse width. The fuel pulse width may be compared to a minimum fuel pulse width amount stored in memory. The minimum fuel pulse width may vary with pressure. The fuel injection duration that results in the minimum fuel pulse width may vary with operating conditions. If the late fuel injection pulse width is at the minimum fuel pulse width, method 700 proceeds to 716. Otherwise, method 700 proceeds to 710 where the fuel pulse delivered to the cylinder is adjusted again at 710.

At 716, method 700 decreases the fuel amount of the middle fuel injection and increases the fuel amount injected in the early fuel pulse. The amount of fuel removed from the middle fuel pulse is provided to the preceding fuel pulse. The pressure of the fuel provided to the cylinder is further reduced, for example, as shown in FIG. 4. Method 700 proceeds to 718 after the fuel pulse width is adjusted.

At 718, it is judged whether the actual combustion phase of the cylinder is at the desired combustion phase. If so, method 700 proceeds to exit. If not, method 700 proceeds to 720.

At 720, method 700 judges whether or not the middle fuel pulse is at the minimum fuel pulse width. If so, method 700 proceeds to 722. Otherwise, method 700 returns to 716 where additional fuel may be removed from the intermediate fuel pulsewidth at 716.

At 722, method 700 judges whether or not the maximum number of fuel pulses is reached during the cylinder cycle. The maximum number of fuel pulses may be determined by fuel injection pressure and nozzle response and engine speed. In one example, the maximum number of fuel pulses during a cylinder cycle may be empirically determined and stored in a table that is consulted/indexed by engine speed. If method 700 determines that the maximum number of injections during a cylinder cycle has been reached, method 700 proceeds to 724. Otherwise, method 700 proceeds to 723.

At 723, method 700 adds an additional fuel pulse to the number of injections during the cylinder cycle. When adding fuel injection, fuel is removed from the last fuel pulse in the cylinder cycle that is not the minimum fuel pulse and added to the new fuel pulse. Method 700 returns to 710 where fuel is added to the new fuel pulse from the last fuel pulse that is not the minimum fuel pulse width at 710.

At 724, method 700 cancels or discards the intermediate fuel pulse width. The amount of fuel removed from the middle fuel pulse is added to the preceding fuel pulse width. In this way, the torque provided by the engine may remain substantially constant. The pressure supplied to the fuel nozzle is also reduced. Method 700 proceeds to 726 after the mid fuel pulse is cancelled.

At 726, method 700 increases the amount of fuel provided in the early fuel pulse and decreases the amount of fuel provided in the late fuel pulse. The pressure of the fuel supplied to the cylinder is also reduced. Method 700 proceeds to 728 after the amount of fuel in the fuel pulse is adjusted.

At 728, method 700 judges whether or not the combustion phase of the cylinder is at the desired combustion phase. If so, method 700 proceeds to exit. If not, method 700 returns to 726 and additional fuel is added from the late fuel pulse to the early fuel pulse. It should be noted that the EOI of the late fuel pulse width is maintained at 710, 716, 722, and 724.

In this manner, the combustion phase of the cylinder may be advanced in response to the cetane number of the fuel being combusted. And EOI timing may be maintained.

Returning to the methods of fig. 7 and 8, at 780 method 700 increases the amount of fuel provided to the cylinder by a preceding fuel pulse of the plurality of fuel pulses provided to the cylinder during the cycle of the cylinder. As shown in FIG. 5, method 700 regulates fuel in a fuel pulse. The fuel of the late fuel pulse is advanced or reduced. The amount of the late fuel pulse is decreased by the amount added to the early fuel pulse. The pressure supplied to the fuel nozzle at 780 is also consumed and reduced. The method proceeds to 782 after the fuel pulse is adjusted.

At 782, method 700 judges whether or not the actual fuel pulse is at the desired combustion phase. If so, method 700 proceeds to exit. Otherwise, method 700 proceeds to 784.

At 784, method 700 judges whether or not the late fuel injection pulse is at a minimum pulse width. If so, method 700 proceeds to 786. Otherwise, method 700 returns to 780 where additional fuel is added to the early fuel pulse and removed from the late fuel pulse at 780.

At 786, method 700 advances and decreases fuel in an intermediate pulse of a plurality of fuel injections provided to the cylinder during a combustion cycle of the cylinder. Also, the decrease in fuel of the middle fuel pulse adds to the preceding fuel pulse and the fuel pressure provided to the nozzle providing fuel is decreased. Method 700 proceeds to 788 after fuel in multiple injections provided to the cylinder is adjusted during a cylinder cycle.

At 788, method 700 judges whether or not the actual combustion phase of the cylinder is at the desired combustion phase. If so, method 700 proceeds to exit. If not, method 700 proceeds to 790.

At 790, method 700 judges whether or not the middle fuel pulse is at the minimum fuel pulse. If so, method 700 proceeds to 792. If not, method 700 returns to 786. At 786, additional fuel is removed from the middle fuel pulse and the same amount of fuel is added to the prior fuel pulse.

At 792, method 700 cancels the late fuel pulse, so the middle fuel pulse is the late fuel pulse and is advanced to further advance combustion phase. The amount of fuel remaining in the late fuel pulse is added to the early fuel pulse and the middle fuel pulse. As shown in FIG. 6, in some examples, additional fuel pulses may also be provided. Also, in some examples, the start of injection timing of the preceding fuel pulse may be advanced. Thus, the EOI timing is advanced. Method 700 proceeds to 794 after the fuel pulse is adjusted. In some examples, the actual combustion phase may be compared to the desired combustion phase after the fuel pulse is adjusted. If the actual combustion phase is at the desired combustion phase, method 700 exits. Otherwise, method 700 proceeds to 794.

At 794, method 700 advances the EOI timing of the middle fuel pulse and additional fuel is removed from the middle fuel pulse (e.g., the now late fuel pulse) and added to the early fuel pulse and/or a new fuel pulse generated prior to the early fuel pulse. And the fuel pressure supplied to the fuel nozzle is reduced. Method 700 proceeds to 796 after the fuel pulse is adjusted.

At 796, method 700 judges whether or not the actual combustion phase is at the desired combustion phase. If so, method 700 proceeds to exit. If not, method 700 returns to 794 where additional fuel is removed from the intermediate fuel pulse at 794.

At 730, method 700 judges whether or not fuel injection start timing (SOI) is maintained. In some examples, SOI timing may be based on engine speed and load. If the engine speed and load are within the predetermined range, SOI is maintained, as shown in FIG. 2, and the method proceeds to 732. Otherwise, method 700 proceeds to 750.

At 732, method 700 reduces fuel in a prior fuel injection event, where fuel is injected multiple times in a cylinder cycle. The amount of fuel in the late fuel injection is increased by the amount of fuel removed from the early fuel injection. The pressure of the fuel injection also increases. By increasing and decreasing the fuel pulse width fuel, fuel is removed from the preceding fuel pulse and added to the following fuel pulse. The fuel pressure may be increased by adjusting the voltage supplied to the fuel pump or by adjusting a valve that controls the fuel flow into the fuel injection pump. Method 700 proceeds to 734 after a fuel pulse supplied to a cylinder during a cylinder cycle is adjusted to reduce combustion phase of the cylinder.

At 734, method 700 judges whether or not the actual combustion phase is within a predetermined range of the desired combustion phase. If so, method 700 proceeds to exit. If not, method 700 proceeds to 736.

At 736, method 700 judges whether or not the early fuel injection pulse of the plurality of fuel injections provided to the cylinder is at the minimum pulse width. The fuel pulse width may be compared to a minimum fuel pulse width amount stored in memory. If the prior fuel injection pulse width is at the minimum fuel pulse width, method 700 proceeds to 738. Otherwise, method 700 proceeds to 732 where the fuel pulse delivered to the cylinder is adjusted again at 732.

At 738, method 700 decreases the fuel amount of the middle fuel injection and increases the fuel amount injected in the late fuel pulse. The amount of fuel removed from the middle fuel injection is provided to the late fuel pulse. The pressure of the fuel supplied to the cylinder is also further increased, for example, as shown in FIG. 2. Method 700 proceeds to 740 after the fuel pulse width is adjusted.

At 740, it is determined whether the actual combustion phase of the cylinder is at the desired combustion phase. If so, method 700 proceeds to exit. Otherwise, method 700 proceeds to 742.

At 742, method 700 judges whether or not the middle fuel pulse is at the minimum fuel pulse width. If so, method 700 proceeds to 744. Otherwise, method 700 returns to 738 where additional fuel may be removed from the intermediate fuel pulsewidth at 738.

At 744, method 700 cancels or discards the intermediate fuel pulse width. The amount of fuel removed from the middle fuel pulse is added to the late fuel pulse width. In this way, the torque provided by the engine may remain substantially constant. The fuel pressure supplied to the fuel nozzle also increases. Method 700 proceeds to 746 after the intermediate fuel pulse is cancelled.

At 746, method 700 decreases the amount of fuel in the early fuel pulse and increases the amount of fuel provided to the late fuel pulse. The pressure of the fuel supplied to the cylinder also increases. Method 700 proceeds to 748 after the amount of fuel in the fuel pulse is adjusted.

At 748, method 700 judges whether or not the combustion phase of the cylinder is at a desired combustion phase. If so, method 700 proceeds to exit. If not, method 700 returns to 746 and additional fuel is removed from the preceding fuel pulse and added to the following fuel pulse. It should be noted that at 732, 738, 744, and 746, the SOI of the late fuel pulse width is maintained.

In this manner, the combustion phase of the cylinder may be retarded in response to the cetane number of the fuel being combusted. Also, SOI timing can be maintained.

Returning now to fig. 7 and 8, at 750, method 700 decreases an amount of fuel provided to a cylinder by a preceding fuel pulse of a plurality of fuel pulses provided to the cylinder during a cycle of the cylinder. Method 700 regulates fuel in a fuel pulse, as shown in FIG. 3. The fuel in the previous fuel pulse is delayed and reduced. The fuel amount of the preceding fuel pulse is reduced by the fuel amount added to the following fuel pulse. The pressure supplied to the fuel nozzle at 750 also increases or increases. Method 700 proceeds to 752 after the fuel pulse is adjusted.

At 752, method 700 judges whether or not the actual combustion phase is at the desired combustion phase. If so, method 700 proceeds to exit. Otherwise, method 700 proceeds to 754.

At 754, method 700 judges whether or not the preceding fuel injection pulse is at a minimum pulse width. If so, method 700 proceeds to 756. Otherwise, method 700 returns to 750 where additional fuel is added to the late fuel pulse and removed from the early fuel pulse at 750.

At 756, method 700 delays and reduces fuel in an intermediate pulse of the plurality of fuel pulses provided to the cylinder during a combustion cycle of the cylinder. Also, a decrease in fuel of the middle fuel pulse is added to the late fuel pulse, and the fuel pressure supplied to the fuel nozzle is increased. Method 700 proceeds to 758 after fuel in multiple injections provided to a cylinder during a cycle of the cylinder is adjusted.

At 758, method 700 judges whether or not the actual combustion phase of the cylinder is at the desired combustion phase. If so, method 700 proceeds to exit. Otherwise, method 700 proceeds to 760.

At 760, method 700 judges whether or not the middle fuel pulse is at the minimum fuel pulse. If so, method 700 proceeds to 762. If not, method 700 returns to 756 where at 756 additional fuel is removed from the middle fuel pulse and the same amount of fuel is added to the late fuel pulse.

At 762, method 700 cancels the prior fuel pulse, so the middle fuel pulse becomes the first fuel pulse and is delayed to further retard combustion phase. The amount of fuel remaining in the first fuel pulse is added to the late fuel pulse and the middle fuel pulse. Also, in some examples, the prior fuel pulse injection start timing may be retarded. So the SOI timing is retarded. Method 700 proceeds to 764 after the fuel pulse is adjusted. In some examples, the actual fuel phase may be compared to the desired fuel phase after the fuel pulse adjustment is performed. If the actual combustion phase is at the desired combustion phase, method 700 exits. Otherwise, method 700 proceeds to 764.

At 764, method 700 retards the SOI timing of the middle fuel pulse and additional fuel is removed from the middle fuel pulse (e.g., the now preceding fuel pulse) and added to the following fuel pulse. Also, the pressure provided to the fuel nozzle is increased. Method 700 proceeds to 766 after the fuel pulse is adjusted.

At 766, method 700 judges whether or not the actual combustion phase is at the desired combustion phase. If so, method 700 proceeds to exit. Otherwise, method 700 returns to 744. At 744, additional fuel is removed from the middle fuel pulse and added to the late fuel pulse.

Accordingly, the methods of fig. 7 and 8 provide a method for an engine, comprising: combusting a first fuel in the cylinder, the first fuel mixture being ignited by compression ignition; combusting a second fuel in the cylinder, the first fuel being combusted with an advanced combustion phase of the cylinder compared to when the second fuel is combusted; and adjusting a number of fuel injections provided to the cylinder during a cycle of the cylinder in response to the combustion phase. In this way, the cylinder combustion phase variation due to fuel cetane number may be compensated for.

The method also includes where the first fuel has a first cetane number and the second fuel has a second cetane number, the second cetane number different from the first cetane number. The method further includes increasing a number of fuel injections in response to the retarded combustion phase. The method further includes adjusting a pressure of fuel provided to the engine in response to a combustion phase of the engine. The method also includes decreasing the fuel amount of the preceding fuel injection event of the cylinder cycle and increasing the fuel amount of the following fuel injection event of the cylinder cycle in response to the advanced combustion phase. In some examples, the method further includes increasing the fuel amount of the preceding fuel injection event and decreasing the fuel amount of the following fuel injection event of the cylinder cycle in response to the retarded combustion phase. The method further includes advancing a timing of a late fuel injection event during a cycle of the cylinder in response to the retarded combustion phase.

The method of fig. 7 and 8 is also provided to operate an engine, comprising: the method includes injecting fuel in at least two fuel injection events during one cycle of a cylinder, and adjusting an amount of fuel between the at least two fuel injection events in response to a combustion phase of the engine. By moving fuel between fuel injection events, combustion phasing can be adjusted while engine noise is kept low.

The method comprises the following steps: adjusting fuel in at least two fuel injection events includes injecting fuel to a cylinder in three separate fuel pulses. The method further comprises the following steps: adjusting the amount of fuel between the at least two fuel injection events includes decreasing a first amount of fuel for a preceding fuel injection event and adding the first amount of fuel to a following fuel injection event. In some examples, the method comprises: adjusting the amount of fuel between the at least two fuel injection events includes increasing a first amount of fuel for a preceding fuel injection event and decreasing the first amount of fuel for a following fuel injection event. The method also includes adjusting a number of fuel injections in the at least two fuel injection events in response to a combustion phasing of the engine. The method further comprises the following steps: adjusting the number of fuel injections includes decreasing the number of fuel injections from three fuel injections to two fuel injections. The method further comprises the following steps: the adjusting at the number of fuel injections includes increasing the number of fuel injections from three fuel injections to four fuel injections. The method also includes adjusting an amount of fuel between the at least two fuel injection events to occur during a plurality of cycles of the cylinder.

Those skilled in the art will appreciate that the methods disclosed in fig. 7 and 8 may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various steps 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 objects, features, and advantages described herein, but is provided for ease of illustration and description. Although not explicitly illustrated, one of ordinary skill in the art will recognize that one or more of the illustrated steps, methods, or functions may be repeatedly performed depending on the particular strategy being used.

This concludes the description. Numerous variations and modifications will occur to those skilled in the art upon reading the foregoing description without departing from the spirit and scope of the invention. For example, single cylinder, I2, I3, I4, I5, V6, V8, V10, V12, and V16 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations may benefit from the present invention.

Claims

1. A method for operating an engine, comprising:

injecting fuel in at least two fuel injection events during one cycle of the cylinder; and

adjusting an amount of fuel between the at least two fuel injection events in response to the ignition timing of the cylinder relative to crankshaft position, including increasing a number of fuel injections as cetane of fuel decreases, and combusting the fuel in the at least two fuel injection events via compression ignition.

2. The method of claim 1 wherein injecting fuel in at least two fuel injection events comprises injecting fuel to the cylinder in three separate fuel pulses, and wherein the timing of a prior fuel injection is retarded in response to advanced combustion phasing related to cetane number of fuel.

3. The method of claim 1, wherein adjusting the amount of fuel between the at least two fuel injection events comprises decreasing a first amount of fuel from a preceding fuel injection event and adding the first amount of fuel to a late injection event.

4. The method of claim 1, wherein adjusting the amount of fuel between the at least two fuel injection events comprises increasing a preceding fuel injection event first amount of fuel and decreasing a following fuel injection event first amount of fuel.

5. The method of claim 1, further comprising adjusting a number of fuel injections during the at least two fuel injection events in response to a combustion phase of the engine.

6. The method of claim 1, wherein adjusting the number of fuel injections includes decreasing the number of fuel injections from three fuel injections to two fuel injections.

7. The method of claim 1, wherein adjusting the number of fuel injections includes increasing the number of fuel injections from three fuel injections to four fuel injections.

8. The method of claim 1, wherein adjusting the amount of fuel in the at least two fuel injection events occurs during a plurality of cycles of the cylinder.

9. An engine system, comprising:

a compression ignition engine having a combustion chamber;

a fuel nozzle that injects fuel directly into the combustion chamber; and

a control system having a computer program stored in a non-transitory medium, the computer program comprising: executable instructions to adjust an amount of fuel between a plurality of fuel injections provided to the cylinder via the fuel injector in response to at least the combustion phase of the cylinder, the amount of fuel between the plurality of fuel injections occurring during one cycle of the cylinder; and, including instructions to limit an amount of fuel transferred from the second fuel injection to the first fuel injection in response to the second fuel injection reaching the minimum fuel injection pulse width, the first fuel injection and the second fuel injection included in the plurality of fuel injections.

10. The engine system of claim 9, wherein adjusting the amount of fuel between the plurality of fuel injections includes decreasing a first amount of fuel for a preceding fuel injection event and adding the first amount of fuel for a following fuel injection event.

11. The engine system of claim 9, wherein fuel is transitioned from the second fuel injection to the first fuel injection by increasing a pulse width of the first fuel injection, and further comprising additional executable instructions to stop providing the second fuel injection after a pulse width of the fuel injector reaches a minimum pulse width.

12. The engine system of claim 9, wherein the amount of fuel between fuel injections is adjusted during cycles of the cylinder.

13. The engine system of claim 9, further comprising additional executable instructions that adjust a number of fuel injections provided to the cylinder in response to combustion phasing.