GB2620977A

GB2620977A - Engine system

Info

Publication number: GB2620977A
Application number: GB2211057.1A
Authority: GB
Inventors: Subramanian Ganesan; Kenneth Sharp Nicholas
Original assignee: Cummins Ltd
Current assignee: Cummins Ltd
Priority date: 2022-07-28
Filing date: 2022-07-28
Publication date: 2024-01-31
Also published as: GB202211057D0

Abstract

An engine system comprising an internal combustion engine, a heat recovery system, and a compressor. The engine comprises at least one cylinder and piston. The heat recovery system 105 comprising a gas expander 132, a closed-loop circuit containing a working fluid, the circuit being arranged with a heat source from the engine such that the working fluid is heated by the heat source, causing expansion of the working fluid that moves a movable part of the gas expander. The moveable part of the gas expander is coupled to the compressor 150 so as to drive the compressor and the compressor outlet is connected to the inlet of the at least one cylinder. Driving the compressor using the energy recovered by the heat recovery system may provide for increased efficiency of the engine system as delivering compressed air to the engine will reduce the fuel consumption of the engine, by reducing the pumping work.

Description

Engine System The present invention relates to an engine system comprising a heat recovery system and particularly, but not exclusively, to an engine system for use in a turbomachine (e.g. a machine comprising a turbocharger).

It is currently known to provide an engine system with a waste heat recovery system in the form of an Organic Rankine Cycle (ORC) waste heat recovery system. The ORC waste heat recovery system uses a closed loop circuit in which a working fluid is circulated. A heat source of the engine system (e.g. heat from exhaust gases from the engine) is provided in the circuit. The heat source heats the working fluid, causing it to expand. A gas expander, for example a turbine expander, or a piston type reciprocating expander, included in the circuit, is driven by the expanding working fluid, thereby converting the heat from the heat source into mechanical work.

The mechanical work output is then converted into electrical energy, for example using a high speed turbine generator, and stored in electrical form, such as in a battery. The electrical energy is then converted into mechanical energy, for example using an electrical motor, to drive an additional load of the engine.

A problem with this heat recovery system is that energy losses occur during the conversion of mechanical work to electrical energy and back again, leading to a reduction in efficiency in the heat recovery system. In addition, the equipment needed for the energy conversion adds cost, complexity and weight to the engine system, and increases its overall size.

In a turbo compound system, there is provided a turbocharger comprising a compressor driven by a turbine, the turbine being driven by exhaust gas from an engine. A power turbine is also provided in, and driven by, the flow of exhaust gas from the engine. The power turbine may be used to augment power produced by the engine (for example, the power turbine may be directly coupled to the crank). Alternatively, the power turbine may be used to drive an additional load (for example the power turbine may be coupled to a power generator and any produced electrical power may be stored and subsequently used to drive the additional load). However, this compound arrangement suffers from the disadvantage that the power turbine, as well as the turbine of the turbocharger, adds additional back pressure in the engine and limits the gain in brake specific fuel consumption, provided by the power turbine, towards high speed/load conditions of the engine.

It is an object of the invention to provide an engine system that at least partially addresses one or more problems or disadvantages present in the prior art.

According to a first aspect of the present invention there is provided an engine system comprising: an internal combustion engine comprising at least one cylinder, the at least one cylinder defining a respective bore, within which a piston is arranged to reciprocate; the at least one cylinder provided with an inlet and an outlet; a heat recovery system comprising a gas expander provided with a moveable part, a closed-loop circuit provided with a working fluid, the circuit being arranged with a heat source of the engine system such that, in use, the working fluid is heated by the heat source, causing expansion of the working fluid, and the gas expander being located in the circuit such that said expansion moves the movable part of the gas expander; and a compressor having an inlet and an outlet and arranged to compress fluid from the inlet and pass the compressed fluid to the outlet; wherein the moveable part of the gas expander is coupled to the compressor so as to drive the compressor; and wherein the outlet of the compressor is connected to the inlet of the at least one cylinder.

Driving the compressor using the energy recovered by the heat recovery system may provide for increased efficiency of the engine system. The compressor can be used to deliver compressed air to the internal combustion engine, which will reduce the fuel consumption of the engine, by reducing the pumping work. In this regard, this can contribute to an increase in the peak torque capability of the engine, with lower fuel consumption.

In addition, the working fluid in the heat recovery system is entirely separate to the gas flow of the internal combustion engine (i.e. the flow of gas out of and into the engine).

This is advantageous in that the heat recovery system does not act to increase the back pressure in the engine. This helps to keep the pumping work of the engine positive in a wider area of the torque curve map.

Furthermore, if the engine system is provided with exhaust gas recirculation, in which the outlet and the inlet of the at least one cylinder are in fluid communication, the burden on the turbocharger compressor is reduced. Exhaust gas recirculation (EGR) systems reduce the turbine power necessary to drive the compressor of the turbocharger and hence reduce the pumping work, reducing burden on a conventional turbocharger compressor.

The moveable part of the gas expander may be mechanically coupled to the compressor to drive the compressor. In this context, a mechanical coupling between first and second members is intended to include arrangements wherein mechanical energy of the first member can be transferred to mechanical energy of the second member without any intermediate conversion to another form of non-mechanical energy. For example, the first and second members are not considered to be mechanically coupled in an arrangement wherein the first member is coupled to the second member via an electrical generator that converts mechanical energy of the first member to electrical energy and an electrical motor that converts said electrical energy into mechanical energy of the second member.

This is advantageous in that, since the gas expander is coupled to the compressor to drive the compressor, there are no losses associated with the conversion of the mechanical work generated by the gas expander into another energy form (e.g. electrical) and back to mechanical work to drive the compressor.

The moveable part of the gas expander may be directly coupled to the compressor so as to drive the compressor. Alternatively, the gas expander may be indirectly coupled to the compressor by a transmission, for example a mechanical transmission.

The heat recovery system may comprise an evaporator provided in the closed loop circuit upstream of the gas expander. The evaporator may be arranged in thermal connection with the heat source such that as the working fluid passes through the evaporator it is heated by the heat source and expands. The heat recovery system may comprise a condenser, provided in the closed loop circuit downstream of the gas expander and arranged to cool the working fluid. The heat recovery system may be provided with a pump arranged to pump the working fluid around the closed loop circuit.

The working fluid may be any suitable type of working fluid. In this respect, the working fluid may be any type of fluid suitable for use in an Organic Rankine Cycle fluid. For example, the working fluid may be an organofluorine compound, for example a fluorocarbon or a hydrofluorocarbon such as, for example, R134a (1,1,1,2-tetrafluoroethane) or R245fa (1,1,1,3,3-Pentafluoropropane). Alternatively, the working fluid may be a hydrocarbon such as, for example, isobutane, pentane or propane.

In use, the compressor inlet may be in gas communication with an air source and the compressor outlet is in gas communication with the inlet of the at least one cylinder, the compressor being arranged to compress air received through the compressor inlet and pass the compressed air to the inlet of the at least one cylinder of the internal combustion engine.

The outlet of the compressor may be connected to the inlet of the at least one cylinder directly. For example, the outlet of the compressor may be connected to the inlet of the at least one cylinder by a pipe or passageway.

Alternatively, the outlet of the compressor may be connected to the inlet of the at least one cylinder via one or more intermediate components. For example, in some embodiments, the engine system comprises a turbocharger comprising a turbine and a second compressor. For such embodiments, the outlet of the compressor may be connected to the inlet of the at least one cylinder via the second compressor. That is, the outlet of the compressor may be in gas communication with an inlet of the second compressor such that air compressed by the compressor is also compressed by the second compressor and passes from the outlet of the second compressor to the inlet of the at least one cylinder. Therefore air compressed by the compressor is further compressed by the second compressor (of the turbocharger) before delivery to the at least one cylinder of the engine.

The second compressor may comprise a housing, the housing defining an inlet, an outlet, and a compressor chamber between the inlet and outlet. An impeller wheel may be rotatably mounted within the compressor chamber to compress air from the inlet and pass the compressed air to the outlet. The outlet may be in gas communication with the inlet of the at least one cylinder of the internal combustion engine.

The turbine may comprise a housing, the housing defining a turbine inlet for receiving exhaust gas from the outlet of the at least one cylinder, a turbine outlet, and a turbine chamber between the turbine inlet and the turbine outlet. A turbine wheel may be rotatably mounted within the turbine chamber and arranged to be drivably rotated by said exhaust gas. The turbine wheel may be coupled to the impeller wheel of the second compressor so as to drivably rotate the impeller wheel.

In some embodiments, the internal combustion engine comprises a plurality of cylinders. The internal combustion engine may comprise an intake manifold assembly connecting an air source to the inlet of each of the plurality of cylinders. The intake manifold assembly may comprise one or more intake manifolds. The internal combustion engine may comprise an outlet manifold assembly connecting the outlet of each of the plurality of cylinders with an exhaust system. The outlet manifold assembly may comprise one or more outlet manifolds.

The internal combustion engine may comprise a plurality of cylinder sets, each set comprising at least one said cylinder. Different cylinder sets may be connected to different intake manifolds and/or different outlet manifolds.

In one embodiment, the internal combustion engine comprises first and second cylinder sets, each set comprising at least one said cylinder; the internal combustion engine has an intake manifold assembly comprising first and second intake manifolds, the first and/or second intake manifolds connecting an air source to one or more inlets of the cylinders of the first and/or second cylinder sets respectively; and the outlet of the compressor may be in gas communication with the second intake manifold such that air compressed by the compressor is passed to the inlet of each cylinder of the second cylinder set.

The second intake manifold may be provided with a separate air source. That is, the second air source may be in gas communication with the second intake manifold such that air from the second air source is passed to the inlet of each cylinder of the second cylinder set.

The first and second intake manifolds may be separate to each other. The first and second intake manifolds may be not in gas communication with each other.

The engine system may further comprise an exhaust gas recirculation system. The outlet of one or more of the at least one cylinder may be in gas communication with the exhaust gas recirculation system, which may be arranged to pass exhaust gas from said one or more cylinder to the inlet of one or more of the at least one cylinder. This allows a portion of exhaust gas to be recirculated to the inlet of one or more of the cylinders. In turn, this may reduce the level of nitrogen oxide in the exhaust gases of the engine system.

For embodiments wherein the internal combustion engine comprises first and second cylinder sets and the first and second intake manifolds connecting an air source to one or more inlets of the cylinders of the first and/or second cylinder sets respectively, the exhaust gas recirculation system may be arranged to pass exhaust gas from said one or more cylinder to only one of the first or second intake manifolds, for example the first intake manifold. Alternatively, separate exhaust gas recirculation systems may be provided for the first and second intake manifolds respectively.

Optionally the compressor inlet may be in gas communication with the outlet of one or more of the at least one cylinder; the compressor outlet may be in gas communication with the inlet of one or more of the at least one cylinder; and the compressor may be arranged to receive exhaust gas from the outlet of said one or more of the at least one cylinder and to pump it to the inlet of said one or more of the at least one cylinder. In this case, the compressor may act as a pump in the exhaust gas recirculation system.

The compressor inlet may be arranged to receive exhaust gas directly from the outlet of the at least one cylinder.

Additionally, or alternatively, the compressor inlet may be arranged to receive exhaust gas indirectly from the outlet of the at least one cylinder. That is, the compressor inlet may be arranged to receive exhaust gas from the outlet of the at least one cylinder via one or more intermediate components. For example, for embodiments wherein the engine system comprises a turbocharger comprising a turbine and a second compressor, the inlet of the compressor may be arranged to receive the exhaust gas from the turbine outlet. The inlet of the compressor may be arranged to receive the exhaust gas directly from the turbine outlet, or indirectly, for example after having passed through an evaporator of the heat recovery system.

The compressor may comprise a housing, the housing defining an axially extending inlet, an outlet, a compressor chamber between the inlet and outlet and an impeller wheel rotatably mounted within the compressor chamber to compress fluid from the inlet and pass the compressed fluid to the outlet, wherein the movable part of the gas expander is coupled to the impeller wheel so as to rotatably drive the impeller wheel.

The compressor may be a radial compressor. In this regard, the housing of the first compressor may comprise an annular volute that defines an annular diffuser passage that extends radially outwardly from the impeller wheel to the outlet.

Alternatively, the compressor may be an axial compressor. In this regard, the housing of the first compressor may define an axially extending outlet passage that connects the impeller wheel to the outlet.

The compressor may comprise a cylinder that defines a bore within which a piston is arranged to reciprocate, the cylinder having an inlet and an outlet, wherein the movable part of the gas expander is coupled to the piston so as to reciprocally drive the piston within the cylinder and thereby compress fluid from the inlet and pass the compressed fluid to the outlet.

The fluid compressed by the compressor may be air.

The gas expander may be any type of expander for use in any suitable waste heat recovery system, including where it is desired to extract energy from a flowing and expanding fluid, including where the fluid is a liquid or gas.

The movable part of the gas expander may be rotatable such that the expansion of the working fluid rotates the movable part of the gas expander. In this case, the movable part of the gas expander may be a turbine wheel.

The movable part of the gas expander may be movable in an axial direction. In this case, the movable part of the gas expander may be a piston arranged such that the expansion of the working fluid causing reciprocal linear motion of the piston in a bore defined by a cylinder of the gas expander.

The gas expander may be any suitable type of gas expander. The gas expander may, for example, be one of a group comprising: a turbine, a piston-type expander, a swashplate type expander, a rotary vane expander or a screw-type expander.

The internal combustion engine may comprise third and fourth cylinder sets, each set comprising at least one said cylinder; the internal combustion engine may comprise an outlet manifold assembly comprising first and second outlet manifolds, the first outlet manifold connecting the outlet of the at least one cylinder of the third set with a first exhaust pathway and the second outlet manifold connecting the outlet of the at least one cylinder of the fourth set with a second exhaust pathway. For embodiments wherein the engine system comprises a turbocharger comprising a turbine and a second compressor, the first exhaust pathway may connect to the turbine inlet. For embodiments wherein the engine system comprises an exhaust gas recirculation system, the second exhaust pathway may connect to the exhaust gas recirculation system.

The first and second outlet manifolds may be separate to each other. The first and second outlet manifolds may be not in gas communication with each other. The second outlet manifold may also connect the outlet of the at least one cylinder of the second set with the turbine inlet. For example, the turbine may be a twin entry turbine.

The second outlet manifold may have a smaller cross-sectional area than the first outlet manifold.

The turbine inlet may comprise first and second inlet ports fluidly connected to the turbine wheel by first and second flow passages respectively, the first and second flow passages being in gas communication with the first and second outlet manifolds respectively.

The other advantages and features of the invention will be apparent from the following

description:

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of a known engine system; Figure 2 shows a schematic view of an engine system according to a first embodiment of the present invention; Figure 3 shows a schematic view of an engine system according to a second embodiment of the present invention; Figure 4 shows a schematic view of an engine system according to a third embodiment of the present invention; Figure 5 shows a schematic view of an engine system according to a fourth embodiment of the present invention; Figure 6 shows a schematic view of an engine system according to a fifth embodiment of the present invention, and Figure 7 shows a schematic view of an engine system according to a sixth embodiment of the present invention.

Referring to Figure 1, there is shown a schematic view of a known engine system 1. The engine system 1 comprises an internal combustion engine 2, a turbocharger 3, an exhaust gas recirculation system 4 and a waste heat recovery system 5.

The internal combustion engine 2 comprises six cylinders 6, each cylinder defining a respective cylindrical bore 7 within which a piston (not shown) is arranged to reciprocate. Each cylinder 6 has an inlet 8 and an outlet 9. An intake manifold 24 provides a fluid connection to each inlet 8 of the cylinders 6. The intake manifold 24 may alternatively be described as an inlet manifold 24.

The turbocharger 3 comprises a turbine 11 and a compressor 12. The turbine 11 comprises a turbine housing 13, the housing 13 defining a turbine inlet 14 and a turbine outlet 15. A turbine wheel 16 is rotatably mounted in a chamber defined by the turbine housing 13 between the inlet 14 and outlet 15.

An outlet manifold 17 connects the outlet 9 of each cylinder 6 to the turbine inlet 14. The outlet manifold 17 may alternatively be described as an outtake manifold 17. The turbine wheel 16 is arranged to be driveably rotated by exhaust gas from the outlet 9 of each cylinder 6.

The compressor 12 comprises a housing 18 that defines an inlet 19 and an outlet 20. An impeller wheel 21 is rotatably mounted in a chamber defined by the housing 18 between the inlet 19 and the outlet 20.

The impeller wheel 21 is coupled to the turbine wheel 16 by a shaft 22 that is rotatably supported by bearings of a bearing assembly 23 for rotation about a shaft axis. In this respect, the rotation of the turbine wheel 16 by the exhaust gas from the engine 2 driveably rotates the impeller wheel 21 about said shaft axis. The rotation of the impeller wheel 21 draws air in through the compressor inlet 19, compresses the air and passes it to the compressor outlet 20. The compressor outlet 20 is in gas communication with the inlet 8 of each cylinder 6 by the intake manifold 24. The compressor inlet 19 is in gas communication with an air source 10.

The compressor outlet 20 is in gas communication with the intake manifold 24 of the engine 2 via a compressor outlet passage 25. A charge air cooler 26 is disposed in the compressor outlet passage 25, between the compressor outlet 20 and the engine intake manifold 24.

Accordingly, the compressor 12 supplies compressed air to the inlets 8 of the engine cylinders 6, for combustion in an engine combustion cycle.

The exhaust gas recirculation system 4 comprises an exhaust gas recirculation passage 27 that connects (in gas communication) the outlet manifold 17 of the engine 2 with the intake manifold 24. Flow of exhaust gas through the exhaust gas recirculation passage 27 is controlled by an exhaust gas recirculation valve 55. An exhaust gas cooler 28 is provided in the exhaust gas recirculation passage 27, between the engine outlet manifold 17 and the engine intake manifold 24. An exhaust gas recirculation mixer 29 is provided between the exhaust gas recirculation cooler 28 and the engine intake manifold 24. The exhaust gas mixer 29 mixes exhaust gas from the exhaust gas recirculation passage 27, which has been cooled by the exhaust gas recirculation cooler 28 with the compressed air from the outlet 20 of the compressor 12, which has been cooled by the charge air cooler 26.

The recirculation of the exhaust gas acts to reduce the levels of polluting emissions from the engine 2. This benefit of exhaust gas recirculation is known in the art and therefore will not be explained in any more detail here.

The waste heat recovery system 5 comprises a closed loop circuit 30 within which an Organic Rankine Cycle (CRC) working fluid circulates. The working fluid may for example be an organofluorine compound, for example a fluorocarbon or a hydrofluorocarbon such as, for example, R134a (1,1,1,2-tetrafluoroethane) or R245fa (1,1,1,3,3-Pentafluoropropane). Alternatively, the working fluid may be a hydrocarbon such as, for example, isobutane, pentane or propane. The waste heat recovery system 5 comprises an evaporator 31, a gas expander 32, a condenser 33 and a pump 34.

In more detail, the evaporator 31 comprises an inlet 35 and an outlet 36 for the working fluid circuit 30. The evaporator 31 is in thermal communication with a heat source of the engine system such that heat from the heat source heats the working fluid passing through the evaporator, causing the working fluid to expand. The heat source is the gas exhaust from the turbine 16 of the turbocharger 3. In this regard, the turbine outlet 15 is in gas communication with the evaporator by a turbine outlet passage 46. The turbine outlet passage 46 passes through the evaporator and heat from the exhaust gas passes from the turbine exhaust passage 46 to the working fluid passing through the evaporator 31.

As exhaust gas passes through the turbine exhaust passage 46 it passes through first and second exhaust after treatment systems 47, 48. The first exhaust after treatment system 47 comprises a catalytic converter and/or a diesel particulate filter. The catalytic converter may be a diesel oxidation catalyst (DOC) and may be operable to encourage oxidation of hydrocarbons and carbon monoxide in the exhaust gas, to form carbon dioxide and water. The diesel particulate filter is arranged to remove diesel particulate matter from the exhaust gas. The second exhaust after treatment system 48 uses selective catalytic reduction (SCR) to reduce nitrogen oxides to diatomic nitrogen and water, using a suitable catalyst.

In the described embodiment, the gas expander 32 is in the form of a turbine 32. The turbine 32 comprises a turbine housing 39 that defines a turbine inlet 37 and a turbine outlet 38. The housing 39 further defines a chamber within which a turbine wheel 40 is rotatably mounted between the inlet 37 and the outlet 38. The turbine wheel 40 is arranged to be rotatably driven about an axis by expansion of working fluid in the circuit 30 passing from the inlet 37 to the outlet 38 (as described in more detail below).

The turbine wheel 40 is driveably coupled to an electrical generator 41 by a shaft 42.

The rotation of the turbine wheel 40 rotates the rotor (not shown) of the generator 41 relative to a stator (not shown) of the generator 41 so as to generate electricity.

The turbine outlet 38 is fluidly connected by the working fluid circuit 30 to an inlet 43 of the condenser 33. An outlet 44 of the condenser 33 is fluidly connected by the working fluid circuit 30 to the pump 34 via a working fluid tank 45.

In use, the pump 34 pumps the working fluid around the circuit 30. The working fluid passes through the evaporator 31 from its inlet 35 to its outlet 36. The heat from the exhaust gas from the turbine 15 heats the working fluid passing through the evaporator 31, causing it to expand and pass, under pressure, to the turbine wheel 40 via the turbine inlet 37.

This rotatably drives the turbine wheel 40, which rotatably drives the rotor of the generator 41 relative to the stator of the generator. This generates electricity which is stored in batteries (not shown). The stored electricity is then converted into mechanical work by a motor (not shown), which is then used to drive additional loads of the engine system 1. Such additional loads may, for example, include any combination of the following: an air conditioning pump, power steering, a water pump and/or an oil pump.

The working fluid passes from the turbine wheel 40 through the turbine outlet 38 to the condenser 33. The expanded working fluid passes from the inlet 43 to the outlet 44 of the condenser and, as it does so, is cooled and condensed by the condenser. The working fluid passes from the outlet 44 of the condenser 33 back to the pump 34 via the fluid tank 45 and the waste heat recovery cycle repeats.

The working fluid circuit 30 further comprises a heat exchanger 49 arranged to form a thermal link between two different sections of the working fluid circuit 30. The working fluid passes through the heat exchanger 49 both as it flows from the turbine outlet 38 to the inlet 43 of the condenser 33 and as it flows from the pump 34 to the inlet 35 of the evaporator 31. This allows heat to be transferred from relatively warmer fluid that exits the turbine outlet 38 to relatively cooler fluid that is pumped to the inlet 35 of the evaporator 31. This both pre-heats the fluid before it passes through the evaporator 31 and pre-cools the fluid before it is cooled and condensed by the condenser 33.

In this way, waste heat from the exhaust of the turbine 16 is recovered by the waste heat recovery system 5 and converted into electrical energy, which is then stored before being converted back into mechanical energy to drive additional loads of the engine system 1.

This known engine system has the disadvantages described in the introductory portion of the specification.

Referring now to Figure 2, there is shown a schematic view of an engine system 101 according a first embodiment of the present invention. The engine system 101 of the first embodiment is identical to that of the known engine system 1 shown in Figure 1, except for the differences described below. Corresponding features are given the same reference numerals, but incremented by 100 in Figure 2.

The engine system 101 of this embodiment differs from the engine system 1 shown in Figure 1 in that the generator 41 is replaced with a compressor 150. The compressor 150 comprises a compressor housing 151 that defines an inlet 152 and an outlet 153.

An impeller wheel 154 is rotatably mounted in a chamber between the inlet 152 and the outlet 153. The impeller wheel 154 is coupled to the turbine wheel 140 by a shaft 142 for rotation about the shaft axis.

The rotation of the turbine wheel 140 by the expanding fluid in the waste heat recovery system 105 (which operates in substantially the same way as in the waste heat recovery system 5 shown in Figure 1) driveably rotates the impeller wheel 154. This draws air in through the inlet 152 from an air source 110', compresses the air and passes it out through the compressor outlet 153. The air source 110' may be the same, or different to, the air source 110 which supplies the engine 102 via the turbocharger 103.

The compressor outlet 153 is in gas communication with the engine intake manifold 124, via outlet path 166, and therefore with the inlets 108 of the engine cylinders 106.

The engine system 101 of this embodiment comprises a compressor gas cooler 156 provided in the outlet path 166, between the compressor outlet 153 and the engine intake manifold 124. A compressor gas mixer valve 157 is provided between the compressor gas cooler 156 and the engine intake manifold 124. The compressor gas mixer valve 157 controls the mixing of gas from the compressor outlet 153, which has been cooled by the compressor gas cooler 156 with the compressed air from the outlet 20 of the compressor 12, which has been cooled by the charge air cooler 26.

This is advantageous in that, since the turbine 140 is coupled to the compressor 150 to drive the compressor 150, there are no losses associated with the conversion of the mechanical work generated by the turbine 132 into another energy form (e.g. electrical) and back to mechanical work to drive the compressor 150.

Furthermore, driving the compressor 150 using the energy recovered by the heat recovery system provides for increased efficiency of the engine system 1. In this regard, the compressed air from the compressor 154 reduces the fuel consumption of the engine by reducing the pumping work. This contributes to an increase in the peak torque capability of the engine 102 with lower fuel consumption.

In addition, the working fluid in the heat recovery system 105 is entirely separate from the gas flow of the engine (i.e. the flow of gas out of and into the engine 102). This is advantageous in that the heat recovery system 105 does not act to increase the back pressure in the engine 102 whilst potentially increasing boost pressure to the intake manifold 108 of the engine 102. This helps to keep the pumping work of the engine 102 positive in a wider area of the torque curve map.

Referring to Figure 3 there is shown a schematic view of an engine system 201 according to a second embodiment of the invention. The engine system 201 of this embodiment is identical to the engine system 101 shown in Figure 2, except for the differences described below. Corresponding features to those shown in the engine system 101 shown in Figure 2 are given the same reference numerals in Figure 3, but incremented by 100.

In this embodiment, the compressor outlet 253 is in gas communication with the inlet 219 of the compressor 221 of the turbocharger 203 by the compressor outlet passage 166. A compressor gas mixer valve 257 is provided between the compressor outlet 253 and the inlet 219 of the compressor 221 of the turbocharger 203. The compressor gas mixer valve 257 controls the mixing of gas from the compressor outlet 253 with air from the air source 210. The compressed air is then further compressed by the compressor 221 of the turbocharger 203 before it is passed out of the outlet 220 of the compressor 221 and passed to the engine intake manifold 224.

Optionally, the engine system 201 of this embodiment may comprise a compressor gas cooler (not shown) provided in the outlet path 266, between the compressor outlet 253 and inlet 219 of the compressor 221 of the turbocharger 203. In general, all air that is supplied to the engine intake manifold 224 is cooled. However, in this embodiment, air from the compressor outlet 253 passes through the charge air cooler 226 so that no additional cooler is provided in the outlet path 266.

Referring to Figure 4 there is shown a schematic view of an engine system 301 according to a third embodiment of the invention. The engine system 301 of this embodiment is identical to the engine system 101 shown in Figure 2, except for the differences described below. Corresponding features to those shown in the engine system 101 shown in Figure 2 are given the same reference numerals in Figure 4, but incremented by 200.

The engine system 301 of this embodiment differs from that shown in Figure 2 in that the internal combustion engine 302 comprises a first set 375 and a second set 376 of said engine cylinders 306.

The first set 375 comprises four of said engine cylinders 306 and the second set 376 comprises two of said engine cylinders 306. The second set 376 of engine cylinders is disposed axially adjacent to the first set of cylinders 375. Each of the cylinders 306 of the first and second sets 375, 376 are substantially identical.

The engine 302 further comprises an intake manifold assembly comprising a first intake manifold 371 and a second intake manifold 372. The first intake manifold 371 connects the exhaust gas recirculation mixer 329 to the inlets 308 of each cylinder 306 of the first set 375. In this regard, the first intake manifold 371 connects the air source 310, the compressor outlet passage 325 and the exhaust gas recirculation passage 327 to the inlet 308 of each cylinder 306 of the first cylinder set 375. Accordingly, the first intake manifold 371 passes compressed air from the compressor 321, recirculated exhaust gas and air from the air source 310 to the inlets 308 of each cylinder 306 of the first cylinder set 375.

The second intake manifold 372 is separate to the first intake manifold 371 and is not in fluid communication with the first intake manifold 371.

In this embodiment, the outlet 353 of the compressor 354 is connected to the inlets 308 of the cylinders 306 of the second cylinder set 376 by a compressor outlet passage 366 which connects the compressor outlet 353 to the second intake manifold 372. The engine system 301 of this embodiment comprises a compressor gas cooler 356 provided in the outlet path 366, between the compressor outlet 353 and the second intake manifold 372.

Accordingly, air compressed by the compressor 354 (that is driven the turbine 340 in the waste heat recovery system 305) is passed to the cylinders 306 of the second cylinder set 376.

This provides similar advantages to the first embodiment in that the compressed air delivered to the internal combustion engine 302 reduces the fuel consumption of the engine 302 by reducing the pumping work.

In addition, the compressed air supplied by the compressor 354 to the cylinders 306 of the second cylinder set 376 may be used for cylinder deactivation. That is, under some operating conditions, the cylinders 306 of the second cylinder set 376 can be deactivated such that the engine 302 only uses the cylinders 306 of the first cylinder set 375. When deactivated, the cylinders 306 of the second cylinder set 376 would not need to be supplied air from the compressor 354 of the exhaust gas recirculation system 304.

In such an embodiment, the compressor 312 of the turbocharger 303 would only need to be sized to accommodate the (four) cylinders 306 of the first cylinder set 375 (rather than needing to accommodate all six cylinders 306). When activated, the cylinders 306 of the second cylinder set 376 can be supplied air from the compressor 354 of the exhaust gas recirculation system 304 (rather than from the turbocharger 303).

Referring to Figure 5 there is shown a schematic view of an engine system 401 according to a fourth embodiment of the present invention. The engine system 401 of this embodiment is identical to the engine system 101 shown in Figure 2, except for the differences described below. Corresponding features to those shown in the engine system 101 shown in Figure 2 are given the same reference numerals in Figure 5, but incremented by 300.

Referring to Figure 5 the engine system 401 differs from that of the engine system 101 shown in Figure 2 in that the compressor inlet 453 is in gas communication with the turbine exhaust passage 446. Accordingly, exhaust gas passing from the turbine 416, through the turbine outlet 415, passes to the compressor wheel 454. Specifically, the turbine exhaust passage 446 is connected to the compressor inlet 453 at a point downstream of the evaporator 431.

The compressor outlet 453 is in gas communication with the EGR cooler 428 via a compressor outlet passage 466. In use, the compressor wheel 454 pumps exhaust gas from the turbine outlet 415 to the EGR cooler 328 and therefore back to the intake manifold 424 of the engine 402.

Referring to Figure 6 there is shown a schematic view of an engine system 501 according to a fifth embodiment of the present invention. The engine system 501 is identical to the engine system 201 shown in Figure 3, except for the differences described below. Corresponding features to those shown in the engine system 201 shown in Figure 3 are given the same reference numerals as in Figure 3, but incremented by 300.

Referring to Figure 6, the engine system 501 of this embodiment differs from that of the embodiment shown in Figure 3 in that the internal combustion engine 502 comprises a first cylinder set 575 and a second cylinder set 576. The first cylinder set 575 comprises four of said cylinders 506 and the second cylinder set 576 comprises two of said cylinders 506. The cylinders 506 of the first and second cylinder sets 575, 576 are substantially identical. The cylinders 506 of the second cylinder set 576 are disposed axially adjacent to the cylinders 506 of the first cylinder set 575.

The internal combustion engine 502 comprises an outlet manifold assembly comprising a first outlet manifold 581 and a second outline manifold 582. The first outlet manifold 581 connects (in gas communication) the outlets of each cylinder 506 of the first cylinder set 575 with an engine outlet passage, that connects the first outlet manifold 581 to the turbine inlet 514.

The second outlet manifold 582 connects the outlets 509 of each cylinder 506 of the second cylinder set 576 to the exhaust gas recirculation passage 527 at a point upstream of the EGR cooler 528.

Accordingly, exhaust gas from the cylinders 506 of the second cylinder set 576 is passed by the exhaust gas recirculation circuit back to the inlets 508 of the cylinders of both the first and second cylinder sets 575, 576 via the exhaust gas recirculation cooler 528 and the exhaust gas recirculation mixer 529.

In this embodiment, such a split outlet manifold is used with an engine system 501 otherwise having all of the features of the engine system 201 shown in Figure 3-i.e. in which the turbine 540 of the waste heat recovery system 505 driveably rotates a compressor 554 which delivers compressed air to the compressor 521 of the turbocharger 503 It will be appreciated that the split outlet manifold arrangement shown in Figure 6 may be used in place of the outlet manifold of any of the preceding embodiments.

Referring to Figure 7 there is shown an engine system 601 according to a fifth embodiment of the invention. The engine system 601 is identical to the engine system 201 shown in Figure 3, except for the differences described below. The corresponding features to those shown in the engine system 201 shown in Figure 3 are given the same reference numerals in Figure 7, but incremented by 400.

The engine system 601 shown in Figure 7 differs from the engine system 201 shown in Figure 3 in that the turbine 232 and the compressor 250 of the waste heat recovery system 205 have been replaced with a piston-type expander 691 and a piston-type compressor 692.

In this regard, the gas expander 691 comprises a housing 693 that defines a substantially cylindrical bore in which a piston 694 is arranged to reciprocate linearly. The cylinder is provided with an inlet 695 and an outlet 696. The inlet 695 is disposed in the working fluid circuit 630 downstream of the evaporator 631. The expanded working fluid passes from the evaporator 631 to the inlet 695 of the piston expander 691. This drives the piston 694 within the bore, before passing out of the outlet 696 of the expander 691. The outlet 696 is in gas communication with the working fluid circuit 630 upstream of the condenser 643 and, accordingly, the working fluid passes from the piston expander 691 to the condenser 633.

The compressor 692 comprises a housing 697 that defines a bore in which a cylinder 700 is arranged to linearly reciprocate. The bore is provided with an inlet 698 and an outlet 699. The inlet 698 is in gas communication with an air source 610'. The outlet 699 is in gas communication, via a compressor outlet passage 666, with the inlet 619 of the compressor 621 of the turbocharger 603, as with the embodiment shown in Figure 3.

The piston 694 of the turbine 691 is coupled to the piston 700 of the compressor 692 by a crank shaft (not shown), such that the reciprocating linear motion of the piston 694 of the turbine 691 caused by the expansion of the working fluid drives the piston 700 of the compressor 692 in a linear reciprocal manner. The motion of the piston 700 of the compressor compresses air within the cylinder that has passed into the cylinder from the compressor inlet 698 and passes the compressed air out through the outlet 691 to the compressor outlet passage 666, where it is passed to the inlet 619 of the compressor 621 (as with the embodiment shown in Figure 3).

It will be appreciated that the piston-type turbine 691 and compressor 692 may be used in place of the turbine wheel and compressor wheel shown in any of the preceding embodiments.

The embodiments shown in Figures 3 to 7 provide the advantages described in relation to the embodiment shown in Figure 2.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected.

For example, in the described embodiments, the heat source used in the waste heat recovery system is the exhaust gas from the turbocharger. It will be appreciated that alternatively, or additionally, any other heat source may be used, including heat from the gas in the exhaust gas recirculation system, heat from the charge air cooler, etc. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary. For the avoidance of doubt, optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional and/or preferred features for each aspect of the invention set out herein are also applicable to any other aspects of the invention, where appropriate.

Claims

Claims 1. An engine system comprising: an internal combustion engine comprising at least one cylinder, the at least one cylinder defining a respective bore, within which a piston is arranged to reciprocate; the at least one cylinder provided with an inlet and an outlet; a heat recovery system comprising a gas expander provided with a moveable part, a closed-loop circuit provided with a working fluid, the circuit being arranged with a heat source of the engine system such that, in use, the working fluid is heated by the heat source, causing expansion of the working fluid, and the gas expander being located in the circuit such that said expansion moves the movable part of the gas expander; and a compressor having an inlet and an outlet and arranged to compress fluid from the inlet and pass the compressed fluid to the outlet; wherein the moveable part of the gas expander is coupled to the compressor so as to drive the compressor; and wherein the outlet of the compressor is connected to the inlet of the at least one cylinder.
2. The engine system of claim 1 wherein the moveable part of the gas expander is mechanically coupled to the compressor to drive the compressor.
3. The engine system of claim 1 or claim 2 wherein the heat recovery system is an Organic Rankine Cycle.
4. The engine system of any preceding claim wherein the compressor is connected to the inlet of the at least one cylinder directly.
The engine system of any one of claims 1 to 3 wherein the outlet of the compressor is connected to the inlet of the at least one cylinder via one or more intermediate components.
6. The engine system of claim 5 wherein the engine system further comprises a turbocharger comprising a turbine and a second compressor and wherein the outlet of the compressor is connected to the inlet of the at least one cylinder via the second compressor.
7. The engine system of any preceding claim wherein the internal combustion engine comprises a plurality of cylinder sets, each set comprising at least one said cylinder and wherein different cylinder sets are connected to different intake manifolds and/or different outlet manifolds.
8. The engine system of claim 7 wherein the internal combustion engine comprises first and second cylinder sets, each set comprising at least one said cylinder; the internal combustion engine has an intake manifold assembly comprising first and second intake manifolds, the first and/or second intake manifolds connecting an air source to one or more inlets of the cylinders of the first and/or second cylinder sets respectively; and wherein the outlet of the compressor is in gas communication with the second intake manifold such that air compressed by the compressor is passed to the inlet of each cylinder of the second cylinder set.
9. The engine system of claim 8 wherein the first intake manifold is provided with a separate air source, the separate air source being in gas communication with the first intake manifold such that air from the separate air source is passed to the inlet of each cylinder of the first cylinder set.
10. The engine system of claim 8 or claim 9 wherein the first and second intake manifolds are separate from each other such that the first and second intake manifolds are not in gas communication with each other.
11. The engine system of any preceding claim further comprising an exhaust gas recirculation system, the outlet of one or more of the at least one cylinder being in gas communication with the exhaust gas recirculation system, and the exhaust gas recirculation system being arranged to pass exhaust gas from said one or more cylinder to the inlet of one or more of the at least one cylinder.
12. The engine system of claim 11, when dependent either directly or indirectly on claim 8 wherein the exhaust gas recirculation system is arranged to pass exhaust gas from said one or more cylinder to only one of the first or second intake manifolds.
13. The engine system of claim 11 or claim 12 wherein the compressor inlet is in gas communication with the outlet of one or more of the at least one cylinder; the compressor outlet is in gas communication with the inlet of one or more of the at least one cylinder; and the compressor is arranged to receive exhaust gas from the outlet of said one or more of the at least one cylinder and to pump it to the inlet of said one or more of the at least one cylinder.
14. The engine system of claim 13 wherein the compressor inlet is arranged to receive exhaust gas directly from the outlet of the at least one cylinder.
15. The engine system of claim 13 or claim 14 wherein the compressor inlet is arranged to receive exhaust gas indirectly from the outlet of the at least one cylinder via one or more intermediate components.
16. The engine system of claim 15 wherein the engine system comprises a turbocharger comprising a turbine and a second compressor, and wherein the inlet of the compressor is arranged to receive the exhaust gas from the turbine outlet.
17. The engine system of any one of claims 7 to 16 wherein the internal combustion engine comprises third and fourth cylinder sets, each of the third and fourth cylinder sets comprising at least one said cylinder; the internal combustion engine comprising an outlet manifold assembly comprising first and second outlet manifolds, the first outlet manifold connecting the outlet of the at least one cylinder of the third set with a first exhaust pathway and the second outlet manifold connecting the outlet of the at least one cylinder of the fourth set with a second exhaust pathway.
18. The engine system of claim 17 comprising a turbocharger comprising a turbine and a second compressor, and wherein the first exhaust pathway connects to an inlet of the turbine.
19. The engine system of claim 17 or claim 18 comprising an exhaust gas recirculation system, and wherein the second exhaust pathway connects to the exhaust gas recirculation system.
20. The engine system of any one of claims 17 to 19 wherein the first and second outlet manifolds are separate from each other such that the first and second outlet manifolds are not in gas communication with each other.
21. The engine system of any one of claims 17 to 20 when dependent either directly or indirectly on claim 18 wherein the second outlet manifold also connects the outlet of the at least one cylinder of the fourth set with the turbine inlet.
22. The engine system of any one of claims 17 to 21 wherein the second outlet manifold has a smaller cross-sectional area than the first outlet manifold.
23. The engine system of any one of claims 17 to 22 when dependent either directly or indirectly on claim 18 wherein the turbine inlet comprises first and second inlet ports fluidly connected to the turbine wheel by first and second flow passages respectively, the first and second flow passages are in gas communication with the first and second outlet manifolds respectively.
24. The engine system of any preceding claim wherein the compressor comprises a housing, the housing defining an axially extending inlet, an outlet, a compressor chamber between the inlet and outlet and an impeller wheel rotatably mounted within the compressor chamber to compress fluid from the inlet and pass the compressed fluid to the outlet, wherein the movable part of the gas expander is coupled to the impeller wheel so as to rotatably drive the impeller wheel.
25. The engine system of any one of claims 1 to 23 wherein the compressor comprises a cylinder that defines a bore within which a piston is arranged to reciprocate, the cylinder having an inlet and an outlet, wherein the movable part of the gas expander is coupled to the piston so as to reciprocally drive the piston within the cylinder and thereby compress fluid from the inlet and pass the compressed fluid to the outlet.
26. The engine system of any preceding claim wherein the gas expander is one of a group comprising: a turbine, a piston-type expander, a swash-plate type expander, or a screw-type expander.