GB2542809A

GB2542809A - Heat engine for a motor vehicle

Info

Publication number: GB2542809A
Application number: GB1517265.3A
Authority: GB
Inventors: Dunn Jonathan; Subrumanian Ganesan
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2015-09-30
Filing date: 2015-09-30
Publication date: 2017-04-05
Also published as: GB201517265D0

Abstract

A heat engine comprises: heat absorption heat exchange means 156A, 156B provided in thermal communication with a heat source 115, 116 of a vehicle, the heat absorption heat exchange means heating a working fluid passing there through; a working body 158 (such as a turbine) downstream of the heat absorption heat exchange means, wherein the working body generates work by expansion of the working fluid to drive pumping means 154, the pumping means pumping the working fluid to cause circulation through the heat engine; and a heat rejection heat exchanger 152 downstream of the working body to reject to atmosphere heat carried by the working fluid. The working fluid may remain as a gas, and may be helium. The heat engine may operate as a Brayton cycle or a Rankine cycle. The heat engine may be provided as part of a motor vehicle to cool components thereof, such as its exhaust, fuel, turbocharger, EGR or charge air.

Description

HEAT ENGINE FOR A MOTOR VEHICLE

TECHNICAL FIELD

The present disclosure relates to heat engines for recovering energy from heat generated by motor vehicles. In particular, but not exclusively, embodiments of the invention relate to a heat engine for recovering energy from heat generated by an internal combustion engine. Aspects of the invention relate to a heat engine, a motor vehicle, a method of cooling a portion of a motor vehicle, a method of cooling one or more vehicle systems, and a method of utilising one or more heat energy sources of a motor vehicle to drive pumping means of a cooling system.

BACKGROUND

It is known to employ heat engines in motor vehicles to recover energy from waste heat generated by a variety of sources such as internal combustion engine exhaust systems. The waste heat is used to heat a working fluid such as steam in an evaporator. Compressed steam is allowed to expand in a turbine device. The turbine device may be mechanically connected to a crankshaft of the vehicle or to an electrical generator.

It is an aim of the present invention to provide an improved apparatus and method for utilising heat energy generated by a motor vehicle.

SUMMARY OF THE INVENTION

Aspects and embodiments of the present invention provide a heat engine, a motor vehicle a method of cooling a portion of a motor vehicle, a method of cooling one or more vehicle systems, and a method of utilising one or more heat energy sources of a motor vehicle to drive pumping means of a cooling system, as claimed in the appended claims.

According to an aspect of the invention for which protection is sought, there is provided a heat engine for a motor vehicle, comprising: heat absorption heat exchange means configured to be provided in thermal communication with a heat source of the vehicle, the heat absorption heat exchange means being arranged to allow heating of a working fluid passing therethrough by the heat source; a working body arranged downstream of the heat absorption heat exchange means, the working body being configured to generate work by expansion of the working fluid to drive a pumping means, the pumping means being arranged to pump the working fluid to cause circulation of the working fluid through the heat engine.

In a further aspect of the invention for which protection is sought, there is provided a heat engine, comprising: heat absorption heat exchange means configured to be provided in thermal communication with a heat source of the vehicle, the heat absorption heat exchange means being arranged to allow heating of a working fluid passing therethrough by means of heat from the heat source; a working body arranged downstream of the heat absorption heat exchange means, the working body being configured to generate work by expansion of the working fluid to drive a pumping means, the pumping means being arranged to pump working fluid to cause circulation of the working fluid through the heat engine; and a heat rejection heat exchanger arranged downstream of the working body configured to reject to atmosphere external to the heat engine heat carried by the working fluid.

The heat source may be a ‘waste’ heat source such as an engine exhaust system, turbocharger device or any other available source of heat.

The heat absorption heat exchange means may relate to a heat absorption heat exchange device. The pumping means may relate to a heat pump, and/or to a mechanical pump such as a rotary pump, optionally a turbine.

Embodiments of the present invention have the advantage that a heat engine may be provided that facilitates cooling of one or more components of a motor vehicle, the heat engine being driven at least in part by heat energy, such as waste heat energy, reducing the amount of energy required to be drawn from an alternative energy source to enable cooling.

In some embodiments, the heat engine may be substantially entirely powered by waste heat, at least once the heat engine is operating, requiring little or no power to be drawn from a power source such as an engine or battery.

Furthermore, the heat engine may be arranged to pump working fluid, and in turn waste heat, at a rate that is dependent on the amount of waste heat available. Thus, in some embodiments the heat engine may be arranged to pump heat at an increasingly faster rate as the amount of waste heat increases. Thus, in some embodiments the heat engine may provide a self-regulating cooling system that increases the amount of cooling as the amount of waste heat available for absorption by the heat absorption heat exchange means increases.

The heat absorption heat exchange means may be provided by evaporator means arranged to cause evaporation of the working fluid therein. Such an arrangement may be provided in the case that the heat engine operates according to an evaporation/condensation cycle, such as the Rankine cycle. In some embodiments, a non-evaporation/condensation cycle such as the Brayton cycle may be employed, the working fluid remaining in the gas phase, and therefore the heat absorption heat exchange means may not be referred to as evaporator means. It is to be understood that some heat absorption heat exchange means may be suitable for use in heat engines operating according to an evaporation/condensation cycle and heat engines operating according to a non-evaporation/condensation cycle.

The evaporator means may comprise an evaporator.

Optionally, the working body comprises a rotary device driven by expansion of the working fluid in the working body, the rotary device of the working body being arranged to drive the pumping means arranged to pump the working fluid.

Optionally, the rotary device of the working body comprises a rotary turbine arranged to provide a rotary output, or a reciprocating piston arrangement arranged to provide the rotary output.

Optionally, the rotary device of the working body is substantially directly coupled to the pumping means arranged to pump the working fluid.

Optionally, the pumping means arranged to pump the working fluid comprises a pump device driven by the working body, optionally a rotary pump device.

Optionally, the rotary pump device of the pumping means comprises a turbine. Alternatively, the pump device may comprise a piston pump device.

Optionally, the working fluid has a boiling point that is below a minimum temperature of operation of the heat engine.

This feature has the advantage that operation of the heat engine is less likely to be compromised by the presence of liquid working fluid and pockets of gas, such that the pockets of gas disrupt flow of working fluid in the heat engine.

Optionally, the working fluid has a boiling point that is substantially equal to or less than 0°C.

Optionally, the working fluid has a boiling point that is substantially equal to or less than -10°C.

Optionally, the working fluid has a boiling point that is substantially equal to or less than: a) -40°C; or b) -100C.

Optionally, the working fluid consists substantially of helium.

Optionally, the working fluid consists substantially of at least one of: methane, ethane, propane, butane, isobutane, pentane, hexane, ethanol, an ethanol/water mixture, ammonia, binary mixtures of ammonia and water, or a refrigerant, such as R245fa, R11, and/or R236fa.

In certain embodiments other hydrocarbons may be used in addition to, or in place of the aforementioned hydrocarbons.

The heat engine may comprise pumping means for pumping the working fluid of the heat engine through the heat engine.

Optionally, the heat engine is provided in a substantially closed loop configuration wherein the working fluid passes in a substantially closed loop through the system.

Optionally, the heat absorption heat exchange means comprises at least one heat exchange device.

The heat engine may be configured to operate according to the Rankine cycle.

Thus the heat engine may comprise a closed loop system in some embodiments.

It is to be understood that other heat engine arrangements employing a bottoming cycle in which expansion of a compressed fluid takes place may be used, in some embodiments.

The heat engine may be configured to operate according to the Brayton cycle.

According to another aspect of the invention for which protection is sought, there is provided a motor vehicle cooling system comprising a heat engine as described above.

According to a further aspect of the invention for which protection is sought, there is provided a motor vehicle comprising a heat engine, or a cooling system, as described above.

The motor vehicle may comprise a body and a powertrain comprising an internal combustion engine, the heat absorption heat exchange means of the heat engine being provided in thermal communication with a portion of the internal combustion engine.

According to a further aspect of the invention for which protection is sought, there is provided a method of cooling a portion of a motor vehicle by means of a heat engine, comprising: heating by means of heat from a heat source of the vehicle, a working fluid passing through a heat absorption heat exchange means of the heat engine; supplying the working fluid to a working body arranged downstream of the heat absorption heat exchange means, the working body being configured to generate work by expansion of the working fluid to drive a pumping means, the pumping means being arranged to pump the working fluid to cause circulation of the working fluid through the heat engine; and rejecting to atmosphere external to the motor vehicle heat carried by the working fluid, by means of a heat rejection heat exchanger arranged downstream of the working body.

This aspect of the invention benefits from the same advantages as set out previously in relation to the other aspects of the invention.

According to a further aspect of the invention for which protection is sought, there is provided a method of cooling by absorption, one or more vehicle systems, comprising: heating by means of heat from a heat source of the vehicle, a working fluid passing through a heat absorption heat exchange means of a heat engine; supplying the working fluid to a working body arranged downstream of the heat absorption heat exchange means, the working body being configured to generate work by expansion of the working fluid to drive pumping means, the pumping means being arranged to pump the working fluid to cause circulation of the working fluid through the heat engine; and rejecting to atmosphere external to the one or more vehicle systems, heat carried by the working fluid by means of a heat rejection heat exchanger arranged downstream of the working body.

The method may comprise cooling at least one of: a fuel reservoir, a charge air cooling apparatus, an exhaust gas recirculation (EGR) apparatus and an exhaust system.

According to a further aspect of the invention for which protection is sought, there is provided a method of utilising one or more heat energy sources of a motor vehicle to drive a pumping means of a cooling system, comprising: heating by means of heat from a heat source of the vehicle, a working fluid passing through a heat absorption heat exchange means of a heat engine; supplying the working fluid to a working body arranged downstream of the heat absorption heat exchange means, the working body being configured to generate work by expansion of the working fluid to drive a pumping means, the pumping means being arranged to pump the working fluid to cause circulation of the working fluid through the heat engine; and rejecting to atmosphere external to the motor vehicle, heat carried by the working fluid by means of a heat rejection heat exchanger arranged downstream of the working body.

The heat source may be a waste heat source.

It is to be understood that the controller or controllers described herein may comprise a control unit or computational device having one or more electronic processors. The system may comprise a single control unit or electronic controller or alternatively different functions of the controller may be embodied in, or hosted in, different control units or controllers. As used herein the term “control unit” will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the stated control functionality. A set of instructions could be provided which, when executed, cause said computational device to implement the control techniques described herein. The set of instructions could be embedded in said one or more electronic processors. Alternatively, the set of instructions could be provided as software to be executed on said computational device. The controller may be implemented in software run on one or more processors. One or more other controllers may be implemented in software run on one or more processors, optionally the same one or more processors as the controller. Other arrangements are also useful.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

For the avoidance of doubt, it is to be understood that features described with respect to one aspect and/or embodiment of the invention may be included within any other aspect and/or embodiment of the invention, alone or in appropriate combination with one or more other features.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is a schematic illustration of a heat engine according to an embodiment of the present invention; and FIGURE 2 is a schematic illustration of the undercarriage of a motor vehicle comprising the heat engine of FIG. 1.

DETAILED DESCRIPTION FIG. 1 is a schematic illustration of a heat engine 150 according to an embodiment of the present invention. The heat engine 150 forms part of a cooling system 100C and is installed in a vehicle 100 illustrated schematically in FIG. 2. The vehicle has a powertrain that includes an engine 100, transmission 108 and driveline 109.

The heat engine 150 is configured to operate according to the Brayton Cycle (BC) in which a working fluid of the heat engine 150 remains in a gaseous phase throughout the cycle of operation of the heat engine 150. In the embodiment of FIG. 1 the working fluid is Helium in the gas phase, although other working fluids may be used in some embodiments, such as one or more other inert gases such as any one or more of: neon, argon, krypton, xenon and/or radon.

The working fluid is circulated within the heat engine 150 in a closed loop cycle by means of a compressor 154. The compressor 154 is located downstream of a heat rejection heat exchanger (e.g. an airblast heat exchanger) 152 and upstream of a pair of heat absorption heat exchangers 156A, 156B that are arranged in series in the illustrated embodiment, although other arrangements may be used in other embodiments. The heat rejection heat exchanger 152 is arranged to allow rejection of thermal energy carried by the working fluid to atmosphere by the flow of air thereover. As shown in FIG. 1, relatively low temperature air 152L is arranged to flow over the heat rejection heat exchanger 152, the low temperature air 152L becoming heated air 152H due to thermal transfer by the heat rejection heat exchanger 152. A blower unit 152B is provided for forcing low temperature air 152L over the heat rejection heat exchanger 152. In the present embodiment, the blower unit 152B is configured to operate when the temperature of working fluid flowing through the heat rejection heat exchanger 152 exceeds a predetermined temperature. For example, in the present embodiment the predetermined temperature is 100°C although other temperatures may be useful and employed in some embodiments. In some alternative embodiments, the blower unit 152B may be configured for substantially continuous operation when the heat engine 150 is operating.

A first one (156A) of the pair of heat absorption heat exchangers 156A, 156B is provided in thermal communication with a fuel cooler device 116 of the vehicle 100, that is arranged to cool fuel prior to injection of the fuel into cylinders of the internal combustion engine 110. A coolant circuit 156AC is arranged to circulate a water-based coolant in a substantially closed loop between the heat absorption heat exchanger 156A and the fuel cooler device 116, in order to cause transfer of thermal energy (waste heat) from the fuel cooler device 116 to the heat absorption heat exchanger 156A. Thus, relatively low temperature coolant 156AL flows from the heat absorption heat exchanger 156A to the fuel cooler device 116 and relatively high temperature coolant 156AH flows from the fuel cooler device 116 to the heat absorption heat exchanger 156A. A second one (156B) of the pair of heat absorption heat exchangers 156A, 156B is provided in thermal communication with a turbocharger device 115 of the vehicle 100 arranged to deliver a flow of intake gas to an intake manifold 110IN of the internal combustion engine 110. It is to be understood that in the present embodiment the intake gas comprises a mixture of air and exhaust gases provided by an exhaust gas recirculation (EGR) system (not shown).

The turbocharger device 115 is configured to deliver a flow of intake gas into the cylinders of the internal combustion engine 110. In a similar arrangement to that of the first one of the pair of heat absorption heat exchangers 156A, 156B, a coolant circuit 156BC is arranged to circulate a coolant in a substantially closed loop between the second heat absorption heat exchanger 156B and turbocharger device 115, to cause transfer of thermal energy (waste heat) from the turbocharger device 115 to the heat absorption heat exchanger 156B. In the present embodiment, the coolant is lubricating oil used to lubricate bearings of the turbocharger device 115. Thus, lubricating oil is drawn from the turbocharger device 115, circulated through the heat absorption heat exchanger 156B, and fed back to the turbocharger device 115.

In some alternative embodiments, the coolant may be arranged to flow in a dedicated coolant circuit through the turbocharger device 115 in fluid isolation from lubricant within the turbocharger device 115. The coolant may be any suitable coolant such as a water-based coolant or an oil-based coolant.

The pair of heat absorption heat exchangers 156A, 156B are provided in the heat engine 150 upstream of a working body 158 in the form of a turbine pump that is arranged to convert energy carried by the working fluid into mechanical energy. The mechanical energy is employed to drive the compressor 154, which, as described above, circulates working fluid within the heat engine 150 in a closed loop cycle. The compressor 154 may be any suitable type of compressor and may also be described as a fluid pump. The compressor may be a piston drive fluid pump, a turbine-type fluid pump or any suitable fluid pump.

It is to be understood that when the internal combustion engine 110 is initially started, with the fuel cooler device 116 and turbocharger device 115 substantially at ambient temperature, little or no mechanical work can be performed by the working body 158. Accordingly, in the present embodiment an electric motor 154M is provided for driving the compressor 154 when the working body 158 is unable to drive the compressor 154.

However, as the fuel cooler device 116 and turbocharger device 115 warm, in use, an increasing amount of thermal energy (waste heat) is transferred to working fluid in the heat engine 150. The pressure of the working fluid in the heat absorption heat exchanger 156 thereby increases, creating a larger pressure difference between the heat absorption heat exchanger 156 and the heat rejection heat exchanger 152 across the working body 158. This pressure difference may be measured by a controller 150C by reference to pressure sensors P1, P2 arranged to measure pressure at an inlet and outlet, respectively, of the working body 158. Once the pressure difference exceeds a predetermined value, the controller 150C causes the motor 154M to stop driving the compressor 154. The compressor 154 is then driven by the working body 158 alone.

The controller 150C also receives a signal from a temperature sensor T1 that is provided in fluid communication with working fluid in the heat rejection heat exchanger 152. When the temperature of working fluid therein rises to around 100°C, the controller 150C causes the blower 152B to be switched on to force air over the heat rejection heat exchanger 152 to cool working fluid therein.

It is to be understood that a variety of working fluids may be employed in embodiments of the present invention such as water, ethanol, ethanol/water mixtures, binary mixtures of ammonia and water or organic compound refrigerants such as R245fa, R236fa, methane, ethane, propane, butane, isobutane, pentane, hexane or a mixture of one or more thereof, helium, neon, argon, krypton, xenon and/or radon. A working fluid that is in the gaseous state at the lowest anticipated temperature, that working fluid of the heat engine 150 may be at immediately prior to, or during, operation is advantageous in that the working fluid will substantially never be in a liquid state when operation thereof is commenced. Such embodiments may be considered to operate according to the Brayton Cycle or variation thereof. If the working fluid remains in the gaseous state, the risk that blockages to flow of working fluid occur, for example due to the formation of air pockets in the system, such as in the case that the working fluid is water, may be reduced. It is to be understood that in embodiments in which evaporation and condensation of working fluid takes place a reservoir may be provided downstream of the heat rejection heat exchanger 152 in which condensed working fluid may be collected. Some such embodiments may operate according to the Rankine Cycle (RC).

It is to be understood that, in embodiments in which condensation of working fluid is expected to occur, whether during operation of the heat engine or when the vehicle 100 is not running and parked, for example when parked under relatively cold ambient conditions, the heat engine 150 may advantageously be configured to reduce the risk that pockets of air or other gases become trapped in one or more portions of the heat engine 150. If such pockets do become trapped, system malfunction or degraded operation may result. The heat engine 150 may be configured to reduce the risk of this problem by careful selection of the location of components of the heat engine 150, and careful routing of conduits carrying working fluid between components of the heat engine 150. It is to be understood that this task may represent a not inconsiderable challenge given the substantial constraints that exist in respect of the packaging of automotive components. Accordingly, selection of a working fluid that remains in the gaseous state over the expected range of temperatures to which the vehicle 100 may be subject, in use, is advantageous.

In some embodiments, the working body 158 may comprise a piston-driven device instead of a turbine-driven device.

Furthermore, in some alternative embodiments one or more other heat sources may be employed to heat the working fluid, in addition to or instead of a fuel cooler device 116 and a turbocharger device 115. In some embodiments one or more components of an exhaust gas after-treatment apparatus may be arranged to be cooled by the heat engine 150. The components of the exhaust gas after-treatment apparatus that are cooled may be components downstream of one or more catalytic converters of the after-treatment apparatus, so as to avoid overcooling of the one or more converters, degrading the performance thereof.

In some embodiments, the heat engine may have a heat absorption heat exchanger that is provided in thermal communication with an engine exhaust gas (EGR) cooler. The EGR cooler may be arranged to cool engine exhaust gas before it is mixed with intake air and drawn into the engine, heat carried by the exhaust gases being transferred to coolant flowing through the heat absorption heat exchanger, and used to heat working fluid of the heat engine.

In some embodiments, the heat engine may have a heat absorption heat exchanger that is provided in thermal communication with a charge air cooler. The charge air cooler may be arranged to cool intake air that has been compressed by a turbocharger device before the air is drawn into the engine.

In some embodiments, one or more heat sources may be arranged to generate additional heat in order to facilitate operation of the heat engine 150. This heat may be referred to as ‘waste’ heat in that it would be rejected to atmosphere if it were not employed by the heat engine 150. Thus the ‘waste heat’ becomes useful heat in that it facilitates powering of the heat engine 150 and therefore cooling of one or more components by the heat engine 150.

Embodiments of the present invention have the advantage that heat generated by one or more components of a vehicle 100 that would otherwise be lost to atmosphere, and thereby wasted, may be used to drive cooling apparatus for cooling the one or more components of the vehicle. Embodiments of the present invention have the advantage that a cooling system may be provided that draws less energy or substantially no energy from a source that might compromise vehicle operation, such as from the engine itself as in the case of conventional cooling systems having engine-driven coolant pumps, or an electrical source of the vehicle.

Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Claims

CLAIMS:

1. A heat engine (150), comprising: heat absorption heat exchange means (156A, 156B) configured to be provided in thermal communication with a heat source (115, 116) of a vehicle (100), the heat absorption heat exchange means (156A, 156B) being arranged to allow heating of a working fluid passing therethrough by means of heat from the heat source (115, 116); a working body (158) arranged downstream of the heat absorption heat exchange means (156A, 156B), the working body (158) being configured to generate work by expansion of the working fluid to drive a pumping means (154), the pumping means being arranged to pump the working fluid to cause circulation of the working fluid through the heat engine (150); and a heat rejection heat exchanger (152) arranged downstream of the working body (158), the heat rejection heat exchanger (152) being configured to reject heat carried by the working fluid to the atmosphere external to the heat engine (150).

2. A heat engine (150) according to claim 1, wherein the working body (158) comprises a rotary device configured to be driven by expansion of the working fluid in the working body (158), the rotary device being arranged to drive the pumping means(154).

3. A heat engine (150) according to claim 2, wherein the rotary device (158) comprises a rotary turbine arranged to provide a rotary output, or a reciprocating piston arrangement arranged to provide the rotary output.

4. A heat engine (150) according to claim 2 or claim 3, wherein the rotary device (158) is substantially directly coupled to the pumping means (154).

5. A heat engine (150) according to any preceding claim, wherein the pumping means (154) comprises a pump device driven by the working body (158).

6. A heat engine (150) according to claim 5, wherein the pump device (154) comprises a turbine.

7. A heat engine (150) according to any preceding claim, wherein the working fluid has a boiling point that is below a minimum temperature of operation of the heat engine (150).

8. A heat engine (150) according to any preceding claim, wherein the working fluid has a boiling point that is substantially equal to or less than 0°C.

9. A heat engine (150) according to any preceding claim, wherein the working fluid has a boiling point that is substantially equal to or less than -10°C.

10. A heat engine (150) according to any preceding claim, wherein the working fluid has a boiling point that is substantially equal to or less than: a) -40°C; or b) -100°C.

11. A heat engine (150) according to any preceding claim, wherein the working fluid consists substantially of helium.

12. A heat engine (150) according to any one of claims 1 to 7, wherein the working fluid consists substantially of at least one of: methane, ethane, propane, butane, isobutane, pentane, hexane, ethanol, an ethanol/water mixture, ammonia, binary mixtures of ammonia and water or a refrigerant, such as R245fa, R11, and/or R236fa.

13. A heat engine (150) according to any preceding claim, wherein the heat engine (150) is provided in a substantially closed loop configuration wherein the working fluid passes in a substantially closed loop through the heat engine.

14. A heat engine (150) according to any preceding claim, wherein the heat absorption heat exchange means (156A, 156B) comprises at least one heat exchange device.

15. A heat engine (150) according to any preceding claim, configured to operate according to the Rankine cycle.

16. A heat engine (150) according to any one of claims 1 to 14, configured to operate according to the Brayton cycle.

17. A motor vehicle cooling system comprising a heat engine (150) according to any preceding claim.

18. A motor vehicle (100) comprising a heat engine (150) according to any one of claims 1 to 16, or comprising a cooling system according to claim 17.

19. A motor vehicle (100) according to claim 18, comprising a body and a powertrain (110, 108, 109) comprising an internal combustion engine (110), the heat absorption heat exchange means (156A, 156B) of the heat engine (150) being provided in thermal communication with a portion of the internal combustion engine (110).

20. A method of cooling a portion of a motor vehicle (100) by means of a heat engine (150), comprising: heating by means of heat from a heat source (115, 116) of the vehicle (100), a working fluid passing through a heat absorption heat exchange means (156A, 156B) of the heat engine (150); supplying the working fluid to a working body (158) arranged downstream of the heat absorption heat exchange means (156A, 156B), the working body (158) being configured to generate work by expansion of the working fluid to drive a pumping means (154), the pumping means (154) being arranged to pump the working fluid to cause circulation of the working fluid through the heat engine (150); and rejecting to atmosphere external to the motor vehicle (100), heat carried by the working fluid by means of a heat rejection heat exchanger (152) arranged downstream of the working body (158).

21. A method of cooling by absorption one or more vehicle systems (115, 116), comprising: heating by means of heat from a heat source (115, 116) of the vehicle (100), a working fluid passing through a heat absorption heat exchange means (156A, 156B) of a heat engine (150); supplying the working fluid to a working body (158) arranged downstream of the heat absorption heat exchange means (156A, 156B), the working body (158) being configured to generate work by expansion of the working fluid to drive a pumping means (154), the pumping means (154) being arranged to pump working fluid to cause circulation of the working fluid through the heat engine (150); and rejecting to atmosphere external to the one or more vehicle systems (115,116), heat carried by the working fluid by means of a heat rejection heat exchanger (152) arranged downstream of the working body (158).

22. A method according to claim 20 or 21, comprising cooling at least one of: a fuel reservoir, a charge air cooling apparatus, an exhaust gas recirculation (EGR) apparatus and an exhaust system.

23. A method of utilising one or more heat energy sources of a motor vehicle (100) to drive pumping means (154) of a cooling system, comprising: heating by means of heat from a heat source of the vehicle, a working fluid passing through a heat absorption heat exchange means of a heat engine; supplying the working fluid to a working body arranged downstream of the heat absorption heat exchange means, the working body being configured to generate work by expansion of the working fluid to drive a pumping means, the pumping means being arranged to pump the working fluid to cause circulation of the working fluid through the heat engine; and rejecting to atmosphere external to the motor vehicle, heat carried by the working fluid by means of a heat rejection heat exchanger arranged downstream of the working body.

24. A cooling system, vehicle or method substantially as hereinbefore described, and/or as illustrated in any one of FIG.’s 1 and 2.