GB2628835A

GB2628835A - Thermal management of an internal combustion engine

Info

Publication number: GB2628835A
Application number: GB2305152.7A
Authority: GB
Inventors: Eager Antony
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2023-04-06
Filing date: 2023-04-06
Publication date: 2024-10-09
Also published as: GB202305152D0; WO2024211047A1

Abstract

An internal combustion engine 100 includes a combustion chamber with an inlet 120 for supplying air to the combustion chamber and an outlet 140 for releasing exhaust gas from the combustion chamber. An exhaust channel receives exhaust from the combustion chamber outlet and supplies the exhaust to an aftertreatment apparatus 440 and a recirculation circuit 500. In the recirculation circuit, exhaust gas flows through the second exhaust channel 404 and back into to the combustion chamber. Flow of the exhaust gas through the recirculation circuit is controllable by a valve 510 and a pump 525. A controller controls the pump and the valve so that, in one mode, the pump, working against the operation of the valve, produces thermal energy and raises the temperature of the exhaust in the recirculation circuit, enabling effective operation of the aftertreatment apparatus sooner after start-up.

Description

THERMAL MANAGEMENT OF AN INTERNAL COMBUSTION ENGINE

Technical field

The disclosure relates to the field of internal combustion engines and, in particular, to internal combustion engines having an exhaust gas recirculation pump and an aftertreatment system that requires thermal energy.

Background

It is a desire of engine manufacturers and users to increase engine efficiency and performance characteristics and to reduce engine emissions.

Engine exhaust is often processed downstream of an internal combustion engine in an aftertreatment apparatus so as to remove various emissions. The aftertreatment apparatus may require specific thermal conditions in order to operate and/or in order to perform periodic cleaning processes.

When an engine is first operated after a period of non-use (e.g. having been left unused overnight) the engine and the aftertreatment system are likely to be cold. While steps may be taken to raise the temperature of the engine. There is generally a delay between bringing the temperature of the engine up to a steady operating temperature and bringing the temperature of the aftertreatment apparatus up to a desired aftertreatment temperature.

The delay may be greater where the thermal environment in the aftertreatment system is controlled indirectly by controlling the engine in such a way as to target a temperature increase in the aftertreatment system.

Improved techniques for increasing the temperature of an aftertreatment system more quickly are desirable for reducing emissions.

Summary of the disclosure

Against this background there is provided an engine assembly comprising: an internal combustion engine having: a combustion chamber with a combustion chamber inlet for supplying air to the combustion chamber and a combustion chamber outlet for releasing exhaust gas from the combustion chamber; an exhaust channel arrangement configured to receive exhaust from the combustion chamber outlet and to supply exhaust to a first exhaust channel and a second exhaust channel; an aftertreatment apparatus configured to receive exhaust from the first exhaust channel; an exhaust gas recirculation circuit configured to receive exhaust gas from the second exhaust channel and to supply exhaust gas to the combustion chamber inlet for supplying recirculated exhaust gas to the combustion chamber, wherein the exhaust gas recirculation circuit comprises an exhaust gas recirculation valve for regulating flow of exhaust through the exhaust gas recirculation circuit and a pump for increasing flow of exhaust through the exhaust gas recirculation circuit, wherein the exhaust gas recirculation valve is downstream of the pump; and a controller configured to control the pump and the exhaust gas recirculation valve such that in response to a request for thermal energy the controller provides an instruction (a) to the exhaust gas recirculation valve to restrict flow and (b) to the pump to pump exhaust gas towards the exhaust gas recirculation valve such that the pump working against the exhaust gas recirculation valve performs work that is converted to thermal energy thereby raising temperature of exhaust in the exhaust channel arrangement.

In this way, the arrangement of the present disclosure may provide increased benefit of the exhaust gas recirculation circuit not only (a) by enabling use of exhaust gas recirculation for conventional exhaust gas recirculation purposes in circumstances where there would otherwise be a negative delta-pressure between the exhaust gas recirculation circuit 500 and the combustion chamber inlet 120 (second mode); but also (b) when the temperature of the exhaust gas exiting the combustion chamber does not exceed the threshold value (first mode).

This may increase overall efficiency of the engine. Furthermore, this may enable effective operation of the aftertreatment apparatus sooner after the engine is first switched on from cold, and may enable aftertreatment cleaning routines to be initiated sooner after the engine is first switched on from cold.

Brief description of the drawings

Figure 1 shows a schematic diagram of an engine assembly useful for understanding the disclosure; Figure 2 shows a schematic diagram of an engine assembly according to a first

embodiment of the disclosure; and

Figure 3 shows a schematic diagram of an engine assembly according to a second embodiment of the disclosure.

Detailed description

A schematic diagram of an engine assembly in accordance with the prior art is shown in Figure 1.

The engine assembly 10 comprises an internal combustion engine 100, a turbocharger system 200, an air supply circuit 300, an exhaust circuit 400 and an exhaust gas recirculation circuit 500.

The internal combustion engine 100 may comprise a combustion chamber 110, a combustion chamber inlet 120 for supplying air to the combustion chamber, a fuel injector (not shown) for injecting fuel into the combustion chamber, a combustion chamber outlet 140 for releasing exhaust gas from the combustion chamber and a rotatable drive shaft (not shown). As is well known in the art, combustion of fuel in air within the combustion chamber 110 results in rotation of the drive shaft. The combustion chamber 110 may comprise one or more pistons (not shown) each of which may be associated with one or more fuel injectors and each of which may have one or more combustion chamber inlets 120 and one or more combustion chamber outlets 140. Again, the specific configuration of combustion chamber inlet 120, combustion chamber outlet 140 and fuel injectors may be as known in the art. In arrangements having a plurality of combustion chambers, the combustion chamber inlet may divide into a plurality of branches each configured to supply one combustion chamber. Similarly, in arrangements having a plurality of combustion chambers, a single combustion chamber outlet may be fed by a plurality of branches each configured to receive exhaust from one of the plurality of combustion chambers.

The engine assembly 10 comprises an exhaust channel arrangement configured to receive exhaust from the combustion chamber outlet 140 and to supply exhaust to a first exhaust channel 402 and a second exhaust channel 404.

The turbocharger system 200 comprises a turbine 210 and a compressor 220. The turbine 210 comprises a turbine inlet 212 by which gas may enter the turbine 210 and a turbine outlet 214 by which gas may exit the turbine 210. The turbine inlet 212 receives exhaust gas from the first exhaust channel 402. Gas passing through the turbine 210 between the turbine inlet 212 and the turbine outlet 214 may cause the turbine 210 to rotate. A mechanical connection between the turbine 210 and the compressor 220 enables rotational kinetic energy in the turbine 210 to be transferred to the compressor 220 in order to compress gas in the compressor 220.

The compressor 220 comprises a compressor inlet 222 by which air may enter the compressor 220 and a compressor outlet 224 by which compressed air may leave the compressor 220.

In this way, in operation, the turbocharger system 200 may be used to recover energy from exhaust gas released by the internal combustion engine 100 and use that energy to compress air upstream of the internal combustion engine 100 in order to enable more fuel to be burned given the increased amount of air available by virtue of the compression. In this way, engine output and efficiency may be increased.

In alternative embodiments, not illustrated, the turbocharger system 200 may comprise a plurality of turbochargers, each comprising a compressor and a turbine, and may be configured such that air flows through the compressor of each turbocharger in turn.

The air supply circuit 300 comprises an air inlet for receiving air and supplying air to the compressor inlet 222. The air supply circuit 300 further comprises a charge cooler 320 (such as an air to air aftercooler (ATACC) 320) configured to receive compressed air from the compressor outlet 224. Downstream of the charge cooler 320, the air supply circuit 300 may comprise an inlet throttle valve 330 configured to enable throttling of the air in the air supply circuit 300. Downstream of the inlet throttle valve 330, the air supply circuit 300 continues to the one or more combustion chamber inlets 120 of the internal combustion engine 100.

The exhaust circuit 400 comprises a route, including the first exhaust channel 402, for transferring exhaust gas from the combustion chamber outlet 140 of the internal combustion engine 100 to the turbine inlet 212 to enable energy recovery within the turbine 210. The exhaust circuit 400 further comprises a bypass loop 410 between the turbine inlet 212 and the turbine outlet 214. The bypass loop 410 comprises a waste gate valve 420. In this way, the waste gate valve 420 may be used to regulate flow of exhaust gas through the turbine 210 between a situation where the waste gate valve 420 is fully closed (such that all exhaust gas in the exhaust circuit passes through the turbine 210) and a situation where the waste gate valve 420 is fully open (such that little exhaust gas in the exhaust circuit passes through the turbine 210).

Downstream of the turbine 210 and the waste gate valve 420, the exhaust circuit 400 comprises a back pressure valve 430 and an aftertreatment apparatus 440 comprising a diesel particulate filter. The back pressure valve 430 may be controlled with an objective of influencing a temperature of the diesel particulate filter in the aftertreatment apparatus 440. As is understood by those skilled in the art, a cleaning process of the diesel particular filter may only be possible when the temperature of the exhaust gas reaching the diesel particulate temperature exceeds a minimum cleaning temperature.

The exhaust gas recirculation circuit 500 extends between the second exhaust channel 404 and the combustion chamber inlet 120 of the internal combustion engine 100. In this way, the exhaust gas recirculation circuit 500 facilitates recirculation of exhaust gas from the combustion chamber 110 back into the combustion chamber 110 for a further combustion cycle.

The exhaust gas recirculation circuit 500 comprises an EGR valve 510, a first EGR cooler 520, a second EGR cooler 540, and a bypass loop 550 comprising a bypass valve 560.

Although the EGR valve 510 is shown upstream of the first EGR cooler 520, the EGR valve may alternatively be located downstream of the first EGR cooler 520. If the EGR valve 510 is located upstream of the first EGR cooler 520, the EGR valve 510 may be termed a hot side EGR valve 510. If the EGR valve 510 is located downstream of the first EGR cooler 520, the EGR valve 510 may be termed a cold side EGR valve 510.

The EGR valve 510 regulates exhaust flow into the exhaust gas recirculation circuit 500. The first EGR cooler 520 may be downstream of the EGR valve 510. The first EGR cooler 520 may be configured to transfer thermal energy away from the exhaust gas. The thermal energy transferred by the first EGR cooler 520 may be transferred to the internal combustion engine 100 so as to retain the thermal energy close to the combustion chamber 110 in order to warm the internal combustion engine 100.

The second EGR cooler 540 may be located downstream of the first EGR cooler 520. Downstream of the second EGR cooler 540 the exhaust gas recirculation circuit 500 supplies recirculated exhaust gas into the combustion chamber 110 via the combustion chamber inlet 120.

The bypass loop 550 enables bypass of the second EGR cooler 540. The bypass loop 550 is deployable by opening the bypass valve 560 such that exhaust gas travels preferentially in the bypass loop 550 over the second EGR cooler 540.

It is known to deploy exhaust gas recirculation, in appropriate circumstances, as a technique for reducing peak combustion temperature in order to reduce the production of NOx. In circumstances where there is a negative delta-pressure between the exhaust gas recirculation circuit 500 and the combustion chamber inlet 120, it may not be possible to open the EGR valve 510 without risking flow of gases in the reverse direction and therefore no exhaust gas arriving at the combustion chamber inlet 120. A control strategy for use of the EGR valve 510 must therefore take account of this.

Figure 2 shows schematic diagram of an engine assembly of a first embodiment of the

disclosure in accordance with the claims.

The arrangement of the Figure 2 embodiment differs from that of Figure 1 by the introduction of a pump 525 in the exhaust gas recirculation circuit. The pump 525 of the Figure 2 embodiment is located upstream of the first EGR cooler 520.

The pump 525 may be used in a first mode of the exhaust recirculation gas circuit and a second mode of the exhaust recirculation gas circuit. (Note that the second mode is deployable in response to the request for thermal energy (c.f. claim 1) while the first mode is deployable in response to a call for increased EGR pressure (c.f. claim 8).) In accordance with the first mode, the pump 525 may be deployed when the EGR valve 510 is (at least partially) open in order to increase a flow of exhaust gas in the exhaust gas recirculation circuit 500. One purpose of operating the pump in the first mode may be to enable use of the exhaust gas recirculation circuit 500 in circumstances for its conventional purpose where it would otherwise not be feasible due to a negative delta-pressure between the exhaust gas recirculation circuit 500 and the combustion chamber inlet 120.

In accordance with the second mode, the pump 525 may be deployed when the EGR valve 510 is closed such that the pump 525 is used for the purpose of doing work against the closed EGR valve 510. Thermal energy is produced by this work which serves the purpose of increasing the temperature of the exhaust system which contributes to a more rapid increase in temperature of the internal combustion engine and the exhaust circuit 400 than would otherwise be possible. This may be particularly useful if certain activities of the aftertreatment apparatus 440 are achievable only once a particular temperature threshold has been reached. Therefore, by deploying the pump in the second mode it is possible to reduce the time delay before being able to perform certain activities of the aftertreatment apparatus 440 (which activities require a certain temperature).

The pump 525 may be an electric pump 525 that is powered by an electricity supply. The electricity supply may include a battery (not shown) and an alternator (also not shown) that converts mechanical energy directly or indirectly from the drive shaft of the engine into electrical energy which may charge the battery and/or power the pump 525.

In circumstances where the pump 525 is an electric pump connected to an electric circuit that receives energy from an alternator that receives mechanical energy from the engine, the work done by the electric pump 525 has a direct result of increasing the work done by the engine, which has a direct result of increasing the generation of thermal energy by the engine 100.

Figure 3 shows schematic diagram of an engine assembly of a second embodiment of the disclosure which is in accordance with the claims.

The arrangement of the Figure 3 embodiment differs from that of Figure 2 only in that EGR valve 510 and the pump 525 are differently located. In particular, the pump 525 and the EGR valve 510 are located downstream of first EGR cooler 520. In both the first embodiment and the second embodiment, the pump 525 is upstream of the EGR valve 510.

While the location of the pump 525 and EGR valve 510 are different in the second embodiment (Figure 3) than in the first embodiment (Figure 2), use of the pump 525 and EGR valve 510 (in both the first mode and the second mode) may be the same as for the first embodiment.

When a user starts an internal combustion engine from cold, it can take some time for the engine to reach a steady state temperature at which it is likely to run most efficiently and at which the aftertreatment apparatus 440 is likely to be most effective at performing its intended processes. In addition, various periodic cleaning operations of the aftertreatment apparatus 440 may require a minimum temperature in order to be initiated.

In some circumstances, there may be a desire to increase exhaust gas recirculation but negative delta-pressure between the exhaust gas recirculation circuit 500 and the combustion chamber inlet 120 may mean that opening the valve 510 would result in gases flowing in the reverse direction. This should be avoided.

In such circumstances, the arrangement of the disclosure with the pump 525 operating in the first mode may be particularly useful.

The second mode of the exhaust gas recirculation circuit may be deployed in circumstances where a temperature of the exhaust gas exiting the combustion chamber outlet 140 is less than the threshold value. In the second mode, the exhaust gas recirculation valve 510 (located downstream of the pump) is closed. To increase the temperature in these circumstances, an instruction is sent to the pump 525 to operate the pump 525 notwithstanding that flow in the exhaust gas recirculation circuit 500 is prevented by the closed exhaust gas recirculation valve 510. In this way, the pump performs work in converting electrical energy to thermal energy. In addition, in circumstances where the pump 525 is an electric pump connected to an electric circuit that receives energy from an alternator that receives mechanical energy from the engine, the work done by the pump has a direct result of increasing the work done by the engine, which has a direct result of increasing the generation of thermal energy by the engine.

Thus, operation of the exhaust gas recirculation circuit in the first mode may be deployed when an engine is first started from cold in order to provide an immediate boost to the thermal energy of the engine before the threshold temperature value is reached. This may be helpful for increasing engine efficiency as well as for enabling various procedures (e.g. cleaning procedures) of the aftertreatment apparatus to take place more quickly after the engine is first started from cold.

Industrial applicability

The arrangement of the present disclosure may provide increased benefit of the exhaust gas recirculation circuit not only (a) by enabling use of exhaust gas recirculation for conventional exhaust gas recirculation purposes in circumstances where there would otherwise be a negative delta-pressure between the exhaust gas recirculation circuit 500 and the combustion chamber inlet 120 (second mode); but also (b) when the temperature of the exhaust gas exiting the combustion chamber does not exceed the threshold value (first mode).

Claims

CLAIMS: 1. An engine assembly comprising: an internal combustion engine having: a combustion chamber with a combustion chamber inlet for supplying air to the combustion chamber and a combustion chamber outlet for releasing exhaust gas from the combustion chamber; an exhaust channel arrangement configured to receive exhaust from the combustion chamber outlet and to supply exhaust to a first exhaust channel and a second exhaust channel; an aftertreatment apparatus configured to receive exhaust from the first exhaust channel; an exhaust gas recirculation circuit configured to receive exhaust gas from the second exhaust channel and to supply exhaust gas to the combustion chamber inlet for supplying recirculated exhaust gas to the combustion chamber, wherein the exhaust gas recirculation circuit comprises an exhaust gas recirculation valve for regulating flow of exhaust through the exhaust gas recirculation circuit and a pump for increasing flow of exhaust through the exhaust gas recirculation circuit, wherein the exhaust gas recirculation valve is downstream of the pump; and a controller configured to control the pump and the exhaust gas recirculation valve such that in response to a request for thermal energy the controller provides an instruction (a) to the exhaust gas recirculation valve to restrict flow and (b) to the pump to pump exhaust gas towards the exhaust gas recirculation valve such that the pump working against the exhaust gas recirculation valve performs work that is converted to thermal energy thereby raising temperature of exhaust in the exhaust channel arrangement.
2. The engine assembly of claim 1 wherein the exhaust gas recirculation circuit comprises a first EGR cooler located within the internal combustion engine.
3. The engine assembly of claim 2 wherein the pump and the exhaust gas recirculation valve are located downstream of the first EGR cooler.
4. The engine assembly of claim 2 wherein the pump and the exhaust gas recirculation valve are located upstream of the first EGR cooler.
5. The engine assembly of claim 2 wherein the exhaust gas recirculation circuit comprises a second EGR cooler located downstream of the pump and the exhaust gas recirculation valve.
6. The engine assembly of any preceding claim wherein the exhaust gas recirculation circuit comprises a primary route and an EGR bypass loop running in parallel with the primary route, wherein the EGR bypass loop includes an EGR bypass valve controllable to regulate flow through the EGR bypass loop, wherein the pump is located in the primary route.
7. The engine assembly of any preceding claim wherein the request for thermal energy is triggered when a sensed or inferred temperature of exhaust gas downstream of the combustion chamber outlet is below a threshold temperature value.
8. The engine assembly of claim 7 wherein the controller is further configured to control the pump and the exhaust gas recirculation valve such that in response to a call for increased EGR pressure the controller provides an instruction (a) to the exhaust gas recirculation valve to enable flow and (b) to the pump to pump exhaust gas towards the exhaust gas recirculation valve such as to increase a flow rate of exhaust gas in the exhaust gas recirculation circuit.
9. The engine assembly of any preceding claim wherein the engine assembly comprises an alternator that converts mechanical energy directly or indirectly from the drive shaft of the engine into electrical energy, and wherein the pump is an electric pump powered by the electrical energy from the alternator.
10. The engine assembly of claim 9 wherein the engine assembly further comprises a battery for storage of the electrical energy provided by the alternator and for providing electrical energy to the pump.
11. The engine assembly of any preceding claim wherein the aftertreatment apparatus comprises a diesel particulate filter.
12. The engine assembly of any preceding claim further comprising a turbocharger system comprising: a turbine configured to recover energy from exhaust gas provided via the first exhaust channel; and a turbocharger compressor configured to receive energy from the turbine and thereby to compress air for supply to the combustion chamber inlet; wherein the turbocharger system is configured to release the exhaust gas to the aftertreatment apparatus.
13. A method of influencing a temperature of an internal combustion engine, the internal combustion engine having: a combustion chamber with a combustion chamber inlet for supplying air to the combustion chamber and a combustion chamber outlet for releasing exhaust gas from the combustion chamber; an exhaust channel arrangement configured to receive exhaust from the combustion chamber outlet and to supply exhaust to a first exhaust channel and a second exhaust channel; an aftertreatment apparatus configured to receive exhaust from the first exhaust channel; and an exhaust gas recirculation circuit configured to receive exhaust gas from the second exhaust channel and to supply exhaust gas to the combustion chamber inlet for supplying recirculated exhaust gas to the combustion chamber, wherein the exhaust gas recirculation circuit comprises an exhaust gas recirculation valve for regulating flow of exhaust through the exhaust gas recirculation circuit and a pump for increasing flow of exhaust through the exhaust gas recirculation circuit, wherein the exhaust gas recirculation valve is downstream of the pump; wherein the method comprises, in response to a request for thermal energy: providing an instruction to the exhaust gas recirculation valve to restrict flow; and providing an instruction to the pump to pump exhaust gas towards the exhaust gas recirculation valve such that the pump working against the exhaust gas recirculation valve performs work that is converted to thermal energy thereby raising temperature of exhaust in the exhaust channel arrangement.
14. The method of claim 13 wherein the request for thermal energy is triggered when a sensed or inferred temperature of exhaust gas downstream of the combustion chamber outlet is below a threshold temperature value.
15. The method of claim 14 wherein the method further comprises receiving an actual value for sensed or inferred temperature of exhaust gas downstream of the combustion chamber outlet and comparing the actual value with the threshold temperature value in order to determine whether to trigger the request for thermal energy.
16. The method of any of claims 13 to 15 wherein, in response to receiving a call for increased EGR pressure, the method comprises: providing an instruction to the exhaust gas recirculation valve to enable flow; and providing an instruction to the pump to pump exhaust gas towards the exhaust gas recirculation valve such as to increase a flow rate of exhaust gas in the exhaust gas recirculation circuit.
17. The method of claim 16 wherein the method further comprises receiving an actual value for sensed or inferred temperature of exhaust gas downstream of the combustion chamber outlet and comparing the actual value with the threshold temperature value in order to determine whether to trigger the call for increased EGR.