A TURBOCHARGED ENGINE SYSTEM AND A METHOD OF CONTROLLING BOOST PRESSURE

Abstract

A turbocharged engine system with electric compressor arranged to inject a compressed fluid into the exhaust subsystem upstream of the turbine of the turbocharger such that, in use, the compressed fluid injected by the electric compressor into the exhaust subsystem maintains the speed of or accelerates the turbine, thereby maintaining or increasing the boost pressure supplied to the turbocharged internal combustion engine. A method of controlling the boost pressure supplied to an internal combustion engine by a turbocharger, said method comprising the steps of: producing a stream of compressed fluid; injecting the stream of compressed fluid into an exhaust stream of the internal combustion engine to produce a pressure-boosted exhaust stream; and controlling the speed of a turbine of the turbocharger using the pressure-boosted exhaust stream to control the boost pressure supplied to the internal combustion engine

Claims

1. A turbocharged engine system comprising: an internal combustion engine, the internal combustion engine in fluid communication with an intake subsystem and an exhaust subsystem; a turbocharger arranged to supply a boost pressure to the internal combustion engine via a turbine coupled to a compressor wheel, the turbine being located in the exhaust subsystem and the compressor wheel being located in the intake subsystem; and an electric compressor arranged to inject a compressed fluid into the exhaust subsystem upstream of the turbine such that, in use, the compressed fluid injected by the electric compressor into the exhaust subsystem maintains the speed of or accelerates the turbine and thereby maintains or increases the boost pressure supplied to the internal combustion engine by the turbocharger.

2. The turbocharged engine system of claim 1, wherein the turbocharged engine system comprises one or more control valves arranged to control the injection timing, pressures and quantity of the compressed fluid into the exhaust by the electric compressor.

3. The turbocharged engine system of claim 2, wherein the one or more control valves comprises an isolator valve arranged to prevent or inhibit the stream of compressed fluid into the exhaust subsystem.

4. The turbocharged engine system of claim 2, wherein the one or more control valves comprises a bypass valve arranged to bypass the electric compressor.

5. The turbocharged engine system of claim 2, wherein the one or more control valves comprises a blow-off valve arranged to control the venting of the compressed fluid produced by the electric compressor into the external environment.

6. The turbocharged engine system of claim 2, wherein the one or more control valves comprises a check valve arranged to prevent fluid in the exhaust subsystem flowing towards the electric compressor.

7. A method of controlling the boost pressure supplied to an internal combustion engine by a turbocharger, said method comprising the steps of: producing a stream of compressed fluid; injecting the stream of compressed fluid into an exhaust stream of the internal combustion engine to produce a pressure-boosted exhaust stream; and controlling the speed of a turbine of the turbocharger using the pressure-boosted exhaust stream such that the boost pressure supplied to the internal combustion engine is controlled.

8. The method of claim 7, wherein the method controls the boost pressure supplied to the internal combustion engine by maintaining or increasing the boost pressure supplied to the internal combustion engine, such that the step of controlling the speed of the turbine comprises the step of maintaining the speed of or accelerating the turbine of the turbocharger using the pressure-boosted exhaust stream, thereby maintaining or increasing the boost pressure supplied to the internal combustion engine.

9. The method of claim 7, wherein the method comprises the additional step of reducing the amount of compressed fluid injected into the exhaust stream when the load of the internal combustion engine or boost pressure approaches, achieves or exceeds a threshold or predetermined value.

10. The method of claim 9, wherein the step of reducing the amount of compressed fluid injected into the exhaust stream comprises a step of restricting the flow of compressed fluid into the exhaust stream.

11. The method of claim 7, wherein the method comprises an additional step of increasing the amount of the compressed fluid injected into the exhaust stream when the load of the internal combustion engine or the boost pressure approaches, is below or falls below a threshold or predetermined value.

12. The method of claim 11, wherein the step of increasing the amount of the compressed fluid injected into the exhaust stream comprises a step of increasing the flow of compressed fluid into the exhaust stream.

13. The method of claim 11, wherein the step of increasing the amount of the compressed fluid injected into the exhaust stream comprises a step of increasing the proportion of the compressed fluid stream that is injected into the exhaust stream.

14. The method of claim 9, wherein the step of reducing the amount of compressed fluid injected into the exhaust stream or the step of increasing the amount of the compressed fluid injected into the exhaust stream comprises a step of venting at least some of the compressed fluid into the external environment or bypassing the electric compressor.

15. The method of claim 7, wherein the compressed fluid is air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0045] Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0046] FIG. 1 is a schematic drawing of a first embodiment of a turbocharged engine system in accordance with present invention, the system of this embodiment comprises an electric compressor that is arranged to inject a compressed fluid into the exhaust subsystem of the engine upstream of the turbine of the turbocharger;

[0047] FIG. 2 is a schematic drawing of a second embodiment of a turbocharged engine in accordance with the present invention; the system of this embodiment comprises a check valve and a blow off valve to assist in the control of the electric compressor of the first embodiment;

[0048] FIG. 3 is a schematic drawing of a third embodiment of a turbocharged engine in accordance with the present invention, the system of this embodiment comprises an isolator valve and a compressor bypass valve to assist in the control of the electric compressor of the first embodiment; and

[0049] FIG. 4 is a flowchart depicting a method of increasing the boost pressure supplied to an internal combustion engine by a turbocharger in accordance with the present invention.

[0050] FIG. 1 of the drawings depicts a schematic drawing of the first embodiment of a turbocharged engine system 100 in accordance with present invention.

[0051] When the turbocharged engine system 100 of FIG. 1 is operational, a mixture of air and fuel is supplied to an internal combustion engine 10 via an intake subsystem 12. In this embodiment, and the subsequent embodiments, the internal combustion engine 100 is a spark-ignition engine. Other embodiments are envisaged for different types of internal combustion engine known in the art, such as compression-ignition engines.

[0052] The intake subsystem 12 comprises an air inlet conduit 14 with an aperture through which air is drawn into the intake subsystem 12. This air is mixed with fuel from the gas supply 16 in the air inlet conduit 14. The flow of fuel from the gas supply 16 to the air inlet conduit 14 is controlled by a fuel control valve 18. The air and fuel mixture in the air inlet conduit 14 has a pressure P1 and a temperature T1 that can be measured by sensors (not shown) incorporated into the air inlet conduit 14.

[0053] During operation, the air inlet conduit 14 supplies the air and fuel mixture to a compressor wheel 20 of a turbocharger 22, where the mixture is compressed. The increased mass and pressure of the air and fuel mixture by the action of the compressor wheel 20 of the turbocharger 22 is known as the boost pressure or the boost. This compression of the air and fuel mixture by the compressor wheel 20 of the turbocharger 22 results in additional air being drawn into the air inlet conduit 14 as is well known in the art.

[0054] The intake subsystem 12 further comprises a radiator inlet conduit 24 that supplies the compressed air and fuel mixture exiting the compressor wheel 20 to a radiator 26. The compressed air and fuel mixture in the radiator inlet conduit 24 has a pressure P2 and temperature T2 that can be measured by sensors (not shown) incorporated into the radiator inlet conduit 24. The pressure P2 of the air and fuel mixture inside the radiator inlet conduit 24 is greater than the pressure P1 of the air and fuel mixture inside the air inlet conduit 14 due to the boost pressure imparted on the mixture by the compressor wheel 20 of the turbocharger 20.

[0055] The radiator 26 cools the compressed air and fuel mixture to provide a cooled and compressed air and fuel mixture to an engine inlet conduit 28. The cooled and compressed air and fuel mixture in the engine inlet conduit 28 has a pressure P2′ and temperature T2′ that can be measured by sensors (not shown) incorporated into the engine inlet conduit 28. The radiator 26 and the engine inlet conduit 28 are part of the intake subsystem 12.

[0056] The engine inlet conduit 28 channels the cooled compressed air and fuel mixture from the radiator 26 to the internal combustion engine 10. During operation, the flow of the cooled compressed air and fuel mixture along the inlet engine conduit 26 into the internal combustion engine 10 is controlled by a throttle 30 in a manner as in known in the art.

[0057] During operation of the turbocharged engine system 100, the internal combustion engine 10 combusts the cooled and compressed air fuel mixture producing mechanical power. The greater mass of air entering the engine 10 because of the action of the compressor wheel 20 of the turbocharger 22 can be used to increase the power output and/or fuel efficiency of the engine as well as reducing the emissions of certain species such as nitrous oxides NO.sub.x.

[0058] The combustion of the air and fuel mixture by the internal combustion engine 10 also produces waste or exhaust fluids that are expelled from the internal combustion engine 10 into the external environment via an exhaust subsystem 32.

[0059] The exhaust subsystem 32 comprises an engine exhaust conduit 34 along which the exhaust fluids from the internal combustion engine 10 flow to a turbine 36 of the turbocharger 22. The pressure P3 and temperature T3 of the exhaust fluid egressing the engine 10 can be measured by sensors (not shown) incorporated into the engine exhaust conduit 34.

[0060] The turbine 36 is rotationally connected or coupled to the compressor wheel 20 by a turbocharger shaft 37. Together the turbine 36, the turbocharger shaft 37 and the compressor wheel 20 make up the turbocharger 20.

[0061] The flow of the hot pressurised exhaust fluids from the engine exhaust conduit 34 rotates the turbine 36 that in turn drives the rotation of the turbocharger shaft 37 and the compressor wheel 20. This power imbalance between the turbine 36 and the compressor wheel 20 causes it to compress the air and fluid mixture in intake subsystem 12, increasing the air mass entering the engine 10, as is known in the art for turbocharged engines.

[0062] After rotating the turbine 36, the exhaust fluid is egressed through an exhaust conduit 38. The exhaust conduit 38 forms part of the exhaust subsystem 32. The pressure P4 and temperature T4 of the exhaust fluid within the exhaust conduit 38 can be measured by sensors (not shown) incorporated into the exhaust conduit 38. The exhaust conduit 38 egress, or exhausts, the exhaust fluid into the environment via aftertreatment, heat recovery, noise attenuation or whatever equipment is installed downstream of the engine.

[0063] In accordance with the present invention, the exhaust subsystem 32 is fluidly connected with an electric compressor 40. The electric compressor 40 comprises an electric motor 42 that rotationally drives a compressor shaft 44 that is coupled to a compressor 46. The electric motor 42 is electrically connected to an external power source (not shown) such as the electrical grid or battery.

[0064] The rotation of the compressor 46 by the electric motor 42 draws in air through a compressor inlet conduit 48 and compresses it, boosting the pressure of the air. This pressure-boosted air is expelled from the compressor 46 into the compressor outlet conduit 50. The pressure P5 and temperature T5 of the pressure-boosted air from the electric compressor 40 can be measured by sensors (not shown) incorporated into the compressor outlet conduit 50.

[0065] The compressor outlet conduit 50 is fluidly connected to the engine exhaust conduit 34. The pressure-boosted air from the electrical compressor 40 is injected into the exhaust conduit 34 and mixed with the exhaust fluid in the engine exhaust conduit 34 to form a mixture of exhaust fluid and air in the engine exhaust conduit 34. The pressure P3′ and temperature T3′ of the exhaust fluid and air mixture can be measured by sensors (not shown) incorporated into the engine exhaust conduit 34 downstream of the fluid connection with the compressor outlet conduit 50. When the electric compressor 40 is running, the air and exhaust fluid mix within the exhaust conduit can have a pressure P3′ that is greater than would be measured if the electric compressor 40 were not installed or operational

[0066] By increasing the pressure P3′ of the fluid entering the turbine 36 of the turbocharger 22, the boost pressure supplied to the engine 10 is increased as the compressor wheel 20 will rotate more quickly. In this way, the amount of boost pressure, i.e. the mass of air, supplied to engine 10 can be controlled by the speed of the electric motor 42 of the electric compressor 40. Increasing the speed of the electric motor 42 increases the pressure of air mixed with the exhaust fluid, thereby increasing the rotation of the turbocharger 22 and increasing the boost pressure supplied to the engine 10. This can be used to accelerate the turbocharger 22 and raise the boost pressure to a desired or optimal value when the internal combustion engine 10 is starting up or experiencing a transient load event.

[0067] FIG. 2 and FIG. 3 of the drawings depict schematic drawings of a second embodiment of a turbocharged engine system 200 and a third embodiment of a turbocharged engine system 300 in accordance with present invention.

[0068] The following features of the second embodiment and third embodiment are substantially identical in structure and function to the equivalent features of the first embodiment in FIG. 1 and the reference numerals for these features are maintained across the embodiments and their respective figures: the internal combustion engine 10; the intake subsystem 12; the air inlet conduit 14; the gas supply 16; the fuel control valve 18; the compressor wheel 20; the turbocharger 22; the radiator inlet conduit 24; the radiator 26; the engine inlet conduit 28; the throttle 30; the exhaust subsystem 32; the engine exhaust conduit 34; the turbine 36; the turbocharger shaft 37; the exhaust conduit 38; the electric compressor 40; the electric motor 42; the compressor shaft 44; the compressor 46; the compressor inlet conduit 48; and compressor outlet conduit 50.

[0069] The second embodiment of the turbocharged engine system 200 in FIG. 2 and the third embodiment of the turbocharged engine system 300 in FIG. 3 differ from the first embodiment in that they comprise valves in series or parallel with the electrical compressor 40 to assist in controlling the flow of pressure-boosted air from the electrical compressor 40 into the engine exhaust conduit 34.

[0070] Referring to the second embodiment of the turbocharged engine system 200 in FIG. 2, the compressor outlet conduit 50 comprises a blow off valve 52 downstream of the electric compressor 40 and a check valve 54 downstream of the blow off valve 52 prior to the connection with the engine exhaust conduit 34.

[0071] The blow off valve 52 is configured to vent the pressure-boosted air produced by the electric compressor 40 into the environment prior to its entry into the exhaust subsystem 32.

[0072] The check valve 54 is configured to prevent the pressurized exhaust fluid in the engine exhaust conduit 34 from flowing through the compressor outlet conduit 50 towards and into the electric compressor 40. The check valve 54 can also be configured to open when the pressure P5 in the compressor outlet conduit 50; the pressure P3 in the engine exhaust conduit 34; or the pressure difference between the pressure P5 in the compressor outlet conduit 50 and the pressure P3′ of the mixture of pressure-boosted air (P5-P3′) exceeds or falls below a threshold or predetermined value.

[0073] In this way, the blow off valve 52 can be used to control or limit the pressure difference between the pressure P5 and pressure P3′ (P5-P3′) supplied to the turbocharger 22 as the blow off valve 52 can be opened to vent any excess or shortfall in pressure P5 generated by the electric compressor 40. Another example of when the blow off valve 52 may vent pressure-boosted air is when the pressure P3′ of the air and exhaust fluid mixture prior to turbine 36 of the turbocharger 22 has reached an optimal or desired value the blow off valve 52 can open to prevent the pressure P3′ exceeding the desired or optimal value. A further example is when the pressure P5 being produced by the electric compressor 40 has reached a desired or optimal value, the blow off valve 52 can open to prevent the pressure P5 exceeding the desired or optimal value.

[0074] Alternatively, the blow off valve 52 can be opened to allow the electric compressor 40 to ramp up to a desired speed. By opening the blow off valve 52 while accelerating the electric motor 42, the load on the electric motor 42 is decreased as the pressure P5 within the compressor outlet conduit 50 is reduced due to the venting of the pressure-boosted air. This means that the electric motor 42 can accelerate to the desired or optimal speed more quickly and once the desired compressor 46 speed has been achieved, the blow off valve 52 can then be shut and the pressure-boosted air supplied to the turbocharger 22 via the engine exhaust conduit 34 when the check value 54 is open or opened. This will provide even more aggressive turbocharger speed increases at the early part of the transient and thus further improve the engine 10 load acceptance capability.

[0075] Referring to the third embodiment of the turbocharged engine system 300 in FIG. 3, the compressor outlet conduit 50 comprises an isolator valve 56 downstream of the electric compressor 40 prior to the connection with the engine exhaust conduit 34. The turbocharged engine system 300 further comprises a bypass conduit 58 that is connected between the compressor inlet conduit 48 and compressor outlet conduit 50 in parallel with the electric compressor 40. The bypass conduit 58 comprises a compressor bypass valve 60.

[0076] The isolator valve 56 is configured to control the flow of pressure-boosted air from the electric compressor 40 into the exhaust subsystem 32. The isolator valve 56 can do this by occluding the compressor outlet conduit 50 partially or completely, thereby limiting the injection of pressure-boosted air form the compressor 40. In this way, the pressure P3′ of the air and fuel mixture prior to entry into the turbine 36 of turbocharger can be controlled. For example, this can be used to ramp up the electric motor 42 to a desired speed prior to opening. Further, the occlusion of the compressor outlet conduit 50 by the isolator valve 56 can prevent flow of the exhaust fluid from the exhaust subsystem 32 into or towards the electric compressor 40.

[0077] The bypass valve 60 is configured to vent the pressure-boosted air produced by the electric compressor 40 back to the inlet of the electric compressor 42 prior to its entry into the exhaust subsystem 32. For example, the bypass valve 60 can open to prevent pressure building up within the compressor outlet conduit 50 when the isolator valve 56 partially or completely occludes the compressor outlet conduit 50, such as when the isolator valve 56 is shut and the electric motor 42 is ramping up to a desired speed. Alternatively, the bypass valve 60 can be actuated to relieve pressure or increase the flow through the electric compressor 40 as it approaches its surge line. The electric compressor 40 will approach its surge line when the isolator valve 56 (or the check valve 54in the second embodiment) is closed and the electric compressor 40 is still spinning, or when the pressure at P3′ is equal to or close to being equal to P5 such that the flow of air through the electric compressor 40 will naturally decrease.

[0078] An immediate injection of pressure-boosted air can be supplied by closing the isolator valve 56 and opening the bypass valve 60 while the electric compressor 40 is running. During this time, the electric compressor 40 can be ramped or spun up to a desired, or maximum, speed raising the pressure P5 of the pressure-boosted air to a desired, or maximum, value. When a load increase occurs on or is requested by the internal combustion engine 10, the isolator valve 56 can then be opened and the bypass valve 60 closed. This causes an instantaneous injection of pressure-boosted air from the electric compressor 40 into the exhaust subsystem 32. The instantaneous injection rapidly accelerates the turbocharger 22 and rapidly increases the boost pressure, enabling rapid load acceptance by the internal combustion engine 10.

[0079] Other embodiments are envisaged where a turbocharged engine system comprises alone or combination any of the blow-off valve of the second embodiment, the check valve of the second embodiment, the isolator valve of the third embodiment and the bypass valve of the third embodiment.

[0080] FIG. 4 of the drawings depicts a method of increasing the boost pressure supplied to the internal combustion engine 10 by a turbocharger 22 using the turbocharged engine systems 100, 200, 300 of FIG. 1, FIG. 2 and FIG. 3.

[0081] The method begins with the electric compressor 40 producing a stream of compressed fluid in step S1. The stream of compressed fluid, typically air, is produced by the action of the compressor 46 being rotated by the electric motor 42. The pressure P5, mass and flow of the compressed fluid is therefore controlled by the speed of the electric motor 42.

[0082] This stream of compressed fluid is then injected or added into the exhaust stream from the internal combustion engine in step S2. The stream of compressed fluid form the electric compressor 40 and exhaust stream mix within the engine exhaust conduit 34 to produce a pressure-boosted exhaust stream.

[0083] This pressure-boosted exhaust stream can then accelerate the turbine 36 of the turbocharger 22 in step S3, which causes the turbocharger 22 to supply a great boost pressure to the internal combustion engine 10.

[0084] Subsequently in step S4, the amount, or mass flow, of the pressure-boosted air being injected into the exhaust subsystem is increased, maintained or decreased. The change or maintenance of the production of the pressure-boosted air is typically made in reference to the boost pressure and the engine load by controlling the speed of the electric compressor 40 or by actuating the isolator valve 56, bypass valve 60, check valve 54 and/or blow-off valve 52 as is described above for the first, second and third embodiments.