GB2544479A

GB2544479A - Internal combustion engine with increased thermal efficiency

Info

Publication number: GB2544479A
Application number: GB1520185.8A
Authority: GB
Inventors: Rutledge John; Dris Antonis
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2015-11-16
Filing date: 2015-11-16
Publication date: 2017-05-24
Anticipated expiration: 2035-11-16
Also published as: GB2544479B; GB201520185D0

Abstract

An internal combustion engine 30 comprising an engine block 380, a cylinder head 281 and a combustion chamber defined as a cylindrical cavity within the engine block enclosed by the cylinder head 281; the combustion chamber comprises an oxidant inlet; an exhaust outlet; and a fuel injector, and at least one of the oxidant inlet, the exhaust outlet and the fuel injector passes through the cylinder head; the internal combustion engine further comprises an exhaust gas recirculation conduit configured to direct exhaust from the exhaust outlet to the oxidant inlet; the internal combustion engine further comprises a primary thermal transfer circuit 301 configured to facilitate thermal transfer from the engine block 380, and a secondary thermal transfer circuit 402 configured to facilitate thermal transfer from both the cylinder head 281 and the exhaust gas recirculation conduit; the secondary thermal transfer circuit 402 is fluidly independent from the primary thermal transfer circuit 301. The secondary thermal transfer circuit 402 may comprise an expander, and the assembly may comprise a tertiary exhaust after-treatment heat transfer circuit (600, Fig. 6).

Description

Internal Combustion Engine with Increased Thermal Efficiency Technical Field

The disclosure relates to the field of internal combustion engines and, in particular, to internal combustion engines having increased thermal efficiency.

Background

Increasing engine efficiency is a desire of engine manufacturers and users alike.

Efficiency of constituent parts of an engine (and related components, such as an after-treatment system) may be temperature dependent. Moreover, different constituent parts of an engine may have different optimum operating temperatures for both efficiency and durability. Furthermore, during certain periods of engine use, there may be a desire for some components of an engine to increase in temperature rapidly in order to increase efficiency while other components may run more efficiently when kept cooler for longer. A prior art engine coolant circuit 100 is shown schematically in Figure 1 in the context of an internal combustion engine 10 including an engine block 180 having one or more combustion cylinders, a cylinder head 181 and an exhaust gas recirculation cooler 182.

The engine may be a conventional internal combustion engine 10, wherein each of one or more combustion cylinders contains a piston (not shown) that oscillates within the combustion cylinder and which is connected to a crank shaft (also not shown) that converts translational movement of the piston into rotational movement of the crank shaft. The crank shaft may provide the main work output of the engine 10. The enginelO may include an exhaust gas recirculation (EGR) channel for feeding a portion of exhaust gas emitted from the combustion cylinder back into the combustion cylinder via an air inlet to aid further combustion. A coolant circuit 100 may be used to transfer thermal energy between the engine block 180, the cylinder head 181 and the exhaust gas recirculation cooler 182 and a radiator 150. The coolant circuit may comprise the radiator 150 in conjunction with a fan 140 by which thermal energy may be released from the coolant circuit 100 to atmosphere. The coolant circuit 100 may further comprise a pump 120 by which a working fluid may be pumped around the coolant circuit 100.

The coolant circuit 100 may be a closed loop system comprising a plurality of conduits 110. In parts of the coolant circuit 100, there may be a single conduit (e.g. 111) between two points whereas in other parts of the coolant circuit there may be a plurality of conduits (e.g. 113 and 114) running in parallel between two points. A first conduit 111 exits the radiator 150 and feeds into the pump 120. Subsequently, the first conduit 111 divides into a plurality of engine block conduits 111a — 111g that comprise channels in the engine block 180.

Next, the plurality of engine block conduits 111a— 111g feeds into a single intermediate conduit 113 before bifurcating into (a) a cylinder head conduit 114 that may comprise a channel (or more than one channel in parallel) through the cylinder head 181 and (b) an exhaust gas recirculation cooler conduit 115 that may comprise a channel or more than one channel in parallel through the exhaust gas recirculation cooler 182.

The cylinder head conduit 114 and the exhaust gas recirculation cooler conduit 115 join into a return conduit 116 that feeds into the inlet of the radiator 150.

In addition, a radiator bypass conduit 117 may be provided parallel to the radiator 150, branching off from the return conduit 116 and joining the first conduit 111. A bypass valve 130 that may be controlled based on fluid temperature may be located at a location where the radiator bypass conduit 117 branches off from the return conduit 116 in order to allow control of flow into the radiator bypass conduit 117 and/or the radiator 150.

In use, fluid (e.g. coolant) may be pumped round the coolant circuit 100 by the pump 120. Fluid may flow from the radiator 150 into the first conduit 111 and then into the engine block conduits 111 a - 111 g where thermal energy may be transferred from the combustion cylinders of the internal combustion engine 10 into the fluid. Fluid may then pass into the intermediate conduit 113 before being divided into that which flows into the cylinder head conduit 114 and that which flows into the exhaust gas recirculation cooler conduit 115.

Fluid in the cylinder head conduit 114 may circulate in fluidly enclosed channels around components in the cylinder head 181, such as fuel injectors, exhaust ports or manifold and air intakes and thermal energy may thereby be transferred from these components into the fluid. Fluid in the exhaust gas recirculation cooler conduit 115 passes through a heat exchanging device in the exhaust gas recirculation cooler and thereby transfers thermal energy from exhaust gas in the exhaust gas recirculator and into the fluid. Fluid then passes to the bypass valve 130 where some or all of the fluid may be directed to the radiator 150 (by which means thermal energy may be released from the fluid) and some or all of the fluid may be directed to the bypass conduit 117. Fluid passing through the radiator 150 and fluid passing through the bypass conduit 117 may recombine as the first conduit 111. Fluid may be circulated constantly by the pump 120.

The rate of flow of fluid in the coolant circuit 100 may be controlled by the pump 120. The relative rates of flow of fluid in the radiator 150 and the bypass conduit 117 may be further controlled by controlling the bypass valve 130 and the extent to which each of these two paths may be open. The coolant circuit described and illustrated omits, for the sake of clarity, components such as oil coolers, cab heater connections, diesel exhaust fluid injectors, turbocharger bearings and other additional items that may or may not be present but which the skilled person would understand as being common options for an engine coolant circuit.

The temperatures of each of the engine block 180, the cylinder head 181 and the exhaust gas recirculation cooler 182 may be affected by a range of different factors. It may often be the case that the temperature of each is different. Moreover, it may often be the case that, at any particular time, the optimum operating temperature of each is different.

Furthermore, it may often be the case that the optimum operating temperature of each varies dependent upon the time that has elapsed since the engine starts. This may be because different components of the engine rise in temperature at different rates.

Accordingly, since efficiency of each component cannot necessarily be maximised within the limitations of what may be controllable, control of the pump 120 and the bypass valve 130 may be designed in accordance with a strategy that seeks to maximise overall efficiency of the engine. A schematic representation of a prior art engine 20 with a heat recovery circuit 200 is shown in Figure 2. This engine 20 may be similar to that of Figure 1 and may also include a heat recovery system 200 that may be configured to collect thermal energy from exhaust, either downstream of an after-treatment system (if fitted) or in an exhaust conduit 203 such as an exhaust gas recirculation system and to use that thermal energy to convert thermal energy to kinetic and/or electrical energy.

Also shown in Figure 2 are the air and exhaust paths for fluid through the engine. In particular, air may flow through a compressor 186, via a charge air cooler 185 and into a combustion cylinder. Downstream of the combustion cylinder, exhaust gas that results from air and fuel being combusted, may flow either (a) into a turbine 187 and onwards to an after-treatment system 204 or (b) into the exhaust gas recirculation channel and may then return to the air inlet downstream of the charge air cooler and upstream of the combustion cylinder. Flow of exhaust through the exhaust gas recirculation channel may be controlled by an EGR valve 184. The exhaust gas recirculation channel may comprise an exhaust gas recirculation cooler 382 for recovering thermal energy from exhaust in the exhaust gas recirculation cooler 382. In alternative arrangements, not illustrated here but familiar to the skilled person, an exhaust gas recirculation channel may begin and end at different parts of the engine. For example, an inlet to the exhaust gas recirculation channel may derive from downstream of the turbine 187 or downstream of the after-treatment system 204.

The heat recovery circuit 200 may include a EGR heat exchanger 210 located in the exhaust gas recirculation cooler 382 and an after-treatment heat exchanger 230 located downstream of an after-treatment portion 204 that, respectively, enable thermal energy to be transferred from the exhaust gas recirculation cooler and from exhaust downstream of the after-treatment portion 204 into the heat recovery circuit 200. The EGR heat exchanger 210 and the after-treatment heat exchanger 230 may be located in parallel branches 201, 202 of the heat recovery circuit 200 and a valve 205 may control flow of fluid into one or both of the parallel branches 201,202.

Furthermore, the heat recovery circuit 200 may comprise a Rankine cycle system that includes an expander 250 configured to convert thermal energy into kinetic energy. The expander 250 may comprise a turbine. The expander 250 may be located in the heat recovery circuit 200 downstream of where the first and second parallel branches 201,202 recombine. The expander 250 may output rotational kinetic energy to a shaft 251 that may provide additional kinetic energy to the crank shaft 188 of the engine 20 or be used for some other purpose. Alternatively, the heat recovery circuit 200 may comprise a thermoelectric generator for converting thermal/kinetic energy of fluid in the heat recovery circuit 200 into electrical energy. Optionally, there may be an expander bypass circuit (not illustrated) to enable working fluid to flow round the heat recovery circuit avoiding the expander 250. This may be particularly appropriate in seeking to prevent unevaporated working fluid from damaging the expander 250.

The heat recovery circuit may further comprise a condenser 270 for cooling working fluid, a reservoir 280 for providing a store of working fluid and a pump 290 for increasing the pressure and flow rate of working fluid. The condenser 270 may be located adjacent the radiator 150 of the engine 20.

The heat recovery circuit 200 may further comprise one or more super heaters 220, 240 (one per parallel branch, 201,202) configured to add additional thermal energy to the heat recovery circuit 200.

The heat recovery circuit 200 may further comprise a recuperator 260. The recuperator 260 may comprise a low pressure inlet 261, a low pressure outlet 262, a high pressure inlet 263 and a high pressure outlet 264. The recuperator 260 may be configured to transfer thermal energy between fluid flowing between the low pressure inlet 261 and the low pressure outlet 262 and fluid flowing between the high pressure inlet 263 and the high pressure outlet 264.

The low pressure inlet 261 may be configured to receive fluid from an outlet of the expander 250. The low pressure outlet 262 may feed into the condenser.

The high pressure inlet 263 may be configured to receive fluid from the reservoir 280 via the pump 290. The high pressure outlet 264 may be configured to supply fluid to the EGR heat exchanger 210, 220 and the after-treatment heat exchanger 230.

In use, cold fluid may be pumped by the pump 290 from the reservoir 280 and into the high pressure inlet 263 of the recuperator 260 where it may collect thermal energy from fluid that passes into the low pressure inlet 261 of the recuperator 260. The warmed high pressure fluid may then pass out of the high pressure outlet 264 and then bifurcates such that some of the fluid may pass into the first parallel branch 201 and some of the fluid may pass into the second parallel branch 202. The valve 205 may be used to influence a proportion of fluid in each branch 201,202. It may be possible that the valve 205 prevents fluid from flowing in one of the branches such that all fluid flows in the other branch.

Fluid in the first branch 201 may pass through an after-treatment heat exchanger 230 that recovers heat from exhaust prior to release of the exhaust to atmosphere. Subsequently, the fluid may collect thermal energy from a heater 240 that may be configured both to heat the fluid and to heat the exhaust gas.

Fluid in the second branch 202 may pass through an EGR heat exchanger 210 that may recover heat from the exhaust gas recirculation system. Subsequently, the fluid may collect thermal energy from the super heater 220.

Fluid in the first and second branches 201,202 may combine upstream of the expander 250. At this point in the heat recovery circuit 200, the fluid may have its greatest thermal energy and highest pressure. The expander 250 may convert thermal energy and pressure in the fluid into kinetic and/or electrical energy. Fluid may thereby lose pressure and temperature in the expander 250 and may then flow into the low pressure inlet 261 of the recuperator wherein thermal energy may be transferred from the low pressure fluid into the high pressure fluid (as described above). Fluid that has entered the low pressure inlet 261 of the recuperator 260 may exit the recuperator at the low pressure outlet 262 and travel on to the condenser 270 and then into the reservoir 280. Fluid in the reservoir 280 may then be available again to be pumped around the heat recovery circuit 200 by the pump 290.

The order of components in the heat recovery circuit 200 may vary from that described herein and illustrated in Figure 2. For example, the pump 290 may be relocated in another part of the circuit 200. The locations of other components may also be altered, depending on the application.

Against this background there is provided an internal combustion engine with increased thermal efficiency.

Summary of the disclosure

The present disclosure provides an internal combustion engine comprising: an engine block, a cylinder head and a combustion chamber defined as a cylindrical cavity within the engine block enclosed by the cylinder head, the combustion chamber comprising an oxidant inlet; an exhaust outlet; and a fuel injector; wherein at least one of the oxidant inlet, the exhaust outlet and the fuel injector passes through the cylinder head; an exhaust gas recirculation conduit configured to direct exhaust from the exhaust outlet to the oxidant inlet; a primary thermal transfer circuit configured to facilitate thermal transfer from the engine block, and a secondary thermal transfer circuit configured to facilitate thermal transfer from both the cylinder head and the exhaust gas recirculation conduit, wherein the secondary thermal transfer circuit is fluidly independent from the primary thermal transfer circuit.

Brief description of the drawings

Figure 1 shows a schematic view of a conventional (prior art) internal combustion engine coolant circuit;

Figure 2 shows a schematic view of a prior art internal combustion engine having an exhaust gas recirculation circuit and an after-treatment system with a heat recovery circuit;

Figure 3 shows a schematic view of part of a coolant circuit of an internal combustion engine in accordance with a first embodiment of the disclosure;

Figure 4 shows a schematic view of a part of a coolant circuit of an internal combustion engine in accordance with a second embodiment of the disclosure;

Figure 5 shows a schematic view of an internal combustion engine in accordance with a third embodiment of the disclosure;

Figure 6 shows a schematic view of an internal combustion engine in accordance with a fourth embodiment of the disclosure; and

Figure 7 shows a schematic view of an internal combustion engine in accordance with a fifth embodiment of the disclosure.

Detailed description

There is shown in Figure 3 a schematic view of an engine coolant circuit 300 in accordance with an embodiment of the disclosure. The engine coolant circuit 300 is shown in the context of an internal combustion engine 30 including an engine block 380 having one or more combustion cylinders, a cylinder head 381 and an exhaust gas recirculation cooler 382.

The internal combustion engine 30 may comprise a primary coolant circuit 301 that may be used to transfer thermal energy away from the engine block 380. The primary coolant circuit 301 may comprise a radiator 150 in conjunction with a fan 140 by which thermal energy may be released from the primary coolant circuit 301 to atmosphere. The primary coolant circuit 301 may further comprise a pump 120 by which a working fluid may be pumped around the primary coolant circuit 301.

The primary coolant circuit 301 may be a closed loop system comprising a plurality of conduits 310. In parts of the primary coolant circuit 301, there may be a single conduit (.e.g. 311) between two points whereas in other parts of the coolant circuit there may be a plurality of conduits (e.g. 312a- 312g) running in parallel between two points. A first conduit 311 may exit the radiator 150 and feed into the pump 120. Subsequently, the first conduit 311 may divide into a plurality of engine block conduits 311 a — 311 g that may comprise channels in the engine block 380.

Next, the engine block conduits 311 a — 311 g may feed into a single return conduit 316 that feeds into the inlet of the radiator 150.

In addition, a radiator bypass conduit 317 may be provided parallel to the radiator 150, branching off from the return conduit 316 and joining the first conduit 311. A bypass valve 130 may be located at a location where the radiator bypass conduit 317 branches off from the return conduit 316 in order to allow control of flow into the radiator bypass conduit 317 and/or the radiator 150. The bypass valve 130 and bypass conduit 317 may be integrated within the cylinder head 380 and cylinder block 381 arrangement, may be remotely mounted or may be of some other arrangement.

In use, fluid (e.g. coolant) may be pumped round the primary coolant circuit 301 by the pump 120. Fluid may flow from the radiator 150 into the first conduit 311 and then into the engine block conduits 311 a - 311 g where thermal energy may be transferred from the combustion cylinders of the internal combustion engine 30 into the fluid. Fluid may then pass to the bypass valve 130 where some or all of the fluid may be directed to the radiator 150 (by which means thermal energy may be released from the fluid) and some or all of the fluid may be directed to the radiator bypass conduit 317. Fluid passing through the radiator 150 and fluid passing through the radiator bypass conduit 317 may recombine as the first conduit 311. Fluid may be circulated constantly by the pump 120.

The rate of flow of fluid in the primary coolant circuit 301 may be controlled by the pump 120. The relative rates of flow of fluid in the radiator 150 and the radiator bypass conduit 317 may be further controlled by the bypass valve 130 and, in particular, the extent to which each of the two paths may be open. The coolant circuit described and illustrated omits, for the sake of clarity, components such as oil coolers, cab heater connections, diesel exhaust fluid injectors, turbocharger bearings and other additional items that may or may not be present but which the skilled person would understand as being common options for an engine coolant circuit.

The internal combustion engine 30 may further comprise a secondary coolant circuit 302 used to transfer thermal energy away from the cylinder head 381 and an exhaust gas recirculation cooler 382.

The secondary coolant circuit 302 may comprise an arrangement of conduits 333. The arrangement of conduits 333 may comprise an inlet conduit 303 that divides into plurality of parallel cylinder head conduits 303a - 303d that are located adjacent components of the cylinder head 381 that emit heat in use, such as fuel injector sleeves, exhaust ports, valve bridges, etc.. The plurality of parallel cylinder head conduits 303a - 303d may converge into a single intermediate conduit 304 that runs into an exhaust gas recirculation cooler 382. The exhaust gas recirculation cooler 382 may comprise a channel or more than one channel in parallel through the exhaust gas recirculation cooler 382 and configured to transfer thermal energy away from exhaust gas travelling in an exhaust gas conduit of the exhaust gas recirculation cooler 382. Downstream of the exhaust gas recirculation cooler 382, the secondary coolant circuit 302 may comprise a return conduit 305.

The secondary coolant circuit 302 may differ from that illustrated in Figure 3. In an alternative embodiment, the order may be reversed in that the secondary coolant circuit 302 may pass through the EGR cooler 382 before passing through the cylinder head 381.

In a further alternative arrangement, the secondary coolant circuit 302 may have two parallel branches, with one directed through the EGR cooler 382 and the other directed through the cylinder head 381. Other potential arrangements may include the secondary coolant circuit 302 having a parallel split between the EGR cooler 382 and only a portion of the cylinder head 381, or some other arrangement.

The secondary coolant circuit 302 may further comprise a bypass conduit 307 that may extend between the inlet conduit 303 and the return conduit 305. A control valve 306 may be situated in the bypass conduit 307 or at an inlet to the bypass conduit 307 to regulate flow of fluid either in the bypass conduit 307 and/or in the remainder of the secondary coolant circuit 302. In this way, it may be possible to divert fluid away from the main part of the secondary coolant circuit 302 (by directing all fluid into the bypass conduit 307) when the internal combustion engine 30 is cold. This may be particularly desirable when the engine is first turned on, so that the exhaust gas can come up to optimum temperature more rapidly and that exhaust gas recirculation can be used sooner after starting the engine from cold without risk of cooler fouling (through faster coolant temperature increase).

Figure 5 shows an embodiment of the disclosure in which the secondary coolant circuit 302 of Figure 3 is used in conjunction with a heat recovery circuit 500. In particular, the return conduit 305 of the secondary coolant circuit 302 may feed directly into the heat recovery circuit 500 and the heat recovery circuit 500 may feed directly into the inlet conduit 303 such that the secondary coolant circuit 302 and the heat recovery circuit 500 may form a single closed loop circuit.

Conceptually, the heat recovery circuit 500 of the Figure 5 embodiment may be similar to that of the Figure 2 embodiment except that, rather than thermal energy being recovered directly from exhaust (in EGR heat exchanger 210), thermal energy may instead be recovered from the secondary coolant circuit 302. In this indirect way, heat may be recovered from both the exhaust gas recirculation cooler 382 and the cylinder head 381. Thermal energy may also be recovered from exhaust downstream of the after-treatment system 204 in addition to that recovered from secondary coolant circuit 302.

In more detail, the heat recovery circuit 500 may comprise a Rankine cycle system that may include an expander 250 configured to convert thermal energy into kinetic energy.

The expander 250 may comprise a turbine. The expander 250 may output rotational kinetic energy to a shaft 251 that may provide additional kinetic energy to the crank shaft (not shown in Figure 5) of the internal combustion engine 30. Alternatively, the heat recovery circuit 500 may comprise a thermoelectric generator for converting thermal/kinetic energy of fluid in the heat recovery circuit into electrical energy. Optionally, there may be an expander bypass circuit (not illustrated) to enable working fluid to flow round the heat recovery circuit avoiding the expander 250. This may be particularly appropriate in seeking to prevent unevaporated working fluid from damaging the expander 250.

The heat recovery circuit may further comprise a condenser 270 for cooling working fluid, a reservoir 280 for providing a store of working fluid and a pump 290 for increasing the pressure and flow rate of working fluid. The condenser 270 may be located adjacent the radiator 150 of the internal combustion engine 30.

The heat recovery circuit 500 may further comprise a super heater 240 configured to add additional thermal energy to the heat recovery circuit 500.

The heat recovery circuit 500 may further comprise a recuperator 260. The recuperator 260 may comprise a low pressure inlet 261, a low pressure outlet 262, a high pressure inlet 263 and a high pressure outlet 264.

The low pressure inlet 261 may be configured to receive fluid from an outlet of the expander 250. The low pressure outlet 262 may feed into a condenser 270 that may be located adjacent the radiator 150 of the engine 20.

The high pressure inlet 263 may be configured to receive fluid from the reservoir 280 via the pump 290. The high pressure outlet 264 of the recuperator 260 may be configured to supply fluid to the secondary coolant circuit 302, as illustrated in detail in Figure 3 and in context in Figure 5.

In use, cold fluid may be pumped by the pump 290 from the reservoir 280 into the high pressure inlet 263 of the recuperator 260 where it may collect thermal energy from fluid that passes into the low pressure inlet 261 of the recuperator 260. The fluid thereby warmed may pass out of the high pressure outlet 264 and then into the secondary coolant circuit 302 where it may be available to transfer thermal energy from the cylinder head 381 and the exhaust gas recirculation cooler 382. The control valve 306 may, however, be used to divert some or all of the fluid away from the cylinder head 381 and the exhaust gas recirculation cooler 382 and into the bypass conduit 307. Downstream of the cylinder head 381 and the exhaust gas recirculation cooler 382, the bypass conduit 307 may merge with the return conduit 305 from the exhaust gas recirculation cooler 382 and then feed into after-treatment heat exchanger 230 downstream of the after-treatment system so as to recover heat from exhaust before releasing the exhaust to atmosphere. The heat recovery circuit 500 then feeds into the inlet of the expander 250, as described above.

The order of components in the heat recovery circuit 500 may vary from that described herein and illustrated in Figure 5. For example, the pump 290 may be relocated in another part of the heat recovery circuit 500. The locations of other components may also be altered, depending on the application.

Further embodiments of the disclosure are illustrated in Figures 4 and 6. These embodiments differ from the embodiments of Figures 3 and 5 in that a secondary coolant circuit 402 may form a closed loop system having a dedicated pump 420 and the heat recovery circuit 600 may form a separate closed loop system that is fluidly independent of the secondary coolant circuit 402. The embodiments of Figures 4 and 6 include a heat exchanger 650 that facilitates flow of thermal energy between the secondary coolant circuit 402 and the heat recovery circuit 600. Flow of fluid within the secondary coolant circuit 402 may be controlled by pump 420.

In a still further embodiment, shown in Figure 7, the secondary coolant circuit may be the same as that disclosed in respect of the embodiment of Figures 4. Flowever, in the Figure 7 embodiment, the heat recovery circuit 700 may differ from that shown in the embodiment of Figure 6 in that the order of components is altered.

In particular, by contrast with the Figure 6 embodiment, in the heat recovery circuit 700, the order of the heat exchanger 450 and the high pressure conduit through the recuperator 260 may be reversed. In particular, a heat exchanger 450 may be located downstream of the pump 290 configured to transfer thermal energy between the secondary coolant circuit 402 and the heat recovery circuit 700. Downstream of the heat exchanger 450 may be located the high pressure inlet 263 of the recuperator 260. The high pressure outlet 264 of the recuperator may feed into after-treatment heat exchanger 230 downstream of the after-treatment system so as to recover heat from exhaust before releasing the exhaust to atmosphere. The heat recovery circuit 700 may then feed into the inlet of the expander 250, as described above in relation to Figure 5.

The order of components in the heat recovery circuit 700 may vary from that described herein and illustrated in Figure 7. For example, the pump 290 may be relocated in another part of the heat recovery circuit 700. The locations of other components may also be altered, depending on the application.

In the context of this disclosure, when discussing parallel branches of fluid circuits, parallel does not necessarily mean strictly geometrically parallel. Rather, it means that there are multiple channels that travel from one location A to one location B.

As the skilled person would readily understand, the disclosure may apply to an engine having any number of cylinders including one, two, three, four, six, eight and more.

Industrial application

The present disclosure may provide an internal combustion engine having primary, secondary and potentially tertiary thermal transfer circuits configured to enable improved thermal efficiency. The secondary or, where present, tertiary thermal transfer circuit may provide heat recovery functionality to convert thermal energy to kinetic and/or electrical energy.

By providing a thermal transfer circuit for the cylinder head and the exhaust gas recirculation conduit that is separate from the thermal transfer circuit for the engine block, it may be possible to control the temperature of these elements independently. The length of the secondary circuit may be shorter than the length of the primary circuit and the secondary circuit may therefore have a lower thermal mass than the primary circuit. Furthermore, since the cylinder head may arrive sooner at a high temperature, it may be possible to use exhaust gas recirculation earlier after starting the engine from cold whilst avoiding a risk of over-cooling the exhaust gas which may result in fouling of the exhaust gas recirculation cooler. This may reduce a delay that may be necessary prior to opening the exhaust gas recirculation valve which may assist in the reduction of particulate and/or NOx emissions.

Furthermore, it may be possible to have primary and secondary thermal transfer circuits at different temperatures that may be more closely aligned to optimum operating temperatures of the components they serve. For example, a preferred operating temperature of the secondary thermal transfer circuit may be higher than that of the primary thermal transfer circuit. Moreover, it may therefore be possible to use different working fluids in the different circuits that may be suited to different operating temperatures. A conventional single thermal transfer circuit may need to operate at the maximum temperature suitable for cooling the most thermally limited components. By contrast, use of a plurality of thermal transfer circuits may allow a circuit with less thermally limited components to operate at a higher temperature. Running a thermal transfer circuit at a higher temperature may give rise to additional benefits including allowing a radiator of reduced size or reduced fan power requirements due to larger temperature differences between coolant fluid and ambient air.

Furthermore, the disclosure provides functionality that gives rise to faster warm up and improved thermal efficiency by recovering thermal energy for conversion to kinetic and/or electrical output.

Claims

CLAIMS:

1. An internal combustion engine comprising: an engine block, a cylinder head and a combustion chamber defined as a cylindrical cavity within the engine block enclosed by the cylinder head, the combustion chamber comprising an oxidant inlet; an exhaust outlet; and a fuel injector; wherein at least one of the oxidant inlet, the exhaust outlet and the fuel injector passes through the cylinder head; an exhaust gas recirculation conduit configured to direct exhaust from the exhaust outlet to the oxidant inlet; a primary thermal transfer circuit configured to facilitate thermal transfer from the engine block, and a secondary thermal transfer circuit configured to facilitate thermal transfer from both the cylinder head and the exhaust gas recirculation conduit, wherein the secondary thermal transfer circuit is fluidly independent from the primary thermal transfer circuit.

2. The internal combustion engine of claim 1 further comprising an exhaust after-treatment system and an after-treatment heat exchanger configured to facilitate transfer of heat between exhaust gas in or downstream of the after-treatment system and the secondary thermal transfer circuit.

3. The internal combustion engine of claim 2 wherein the after-treatment heat exchanger is located in the secondary thermal transfer circuit.

4. The internal combustion engine of any preceding claim wherein the secondary thermal transfer circuit further comprises an expander configured to convert thermal and kinetic energy of fluid in the secondary thermal transfer circuit into another form of energy, optionally rotational kinetic energy.

5. The internal combustion engine of claim 4 wherein the secondary thermal transfer circuit comprises: an expander bypass conduit configured to provide a bypass of the secondary thermal transfer circuit away from the expander; and an expander bypass valve configured to enable control of flow of fluid into the expander bypass conduit.

6. The internal combustion engine of claim 1 further comprising: a tertiary thermal transfer circuit; an exhaust after-treatment system; and an after-treatment heat exchanger configured to facilitate transfer of heat between exhaust gas in or downstream of the after-treatment system and the tertiary thermal transfer circuit; wherein the tertiary thermal transfer circuit comprises an intermediate heat exchanger configured to facilitate thermal transfer between the secondary thermal transfer circuit and the tertiary thermal transfer circuit.

7. The internal combustion engine of claim 6 wherein the after-treatment heat exchanger is located in the tertiary thermal transfer circuit.

8. The internal combustion engine of claim 6 wherein the tertiary thermal circuit further comprises an expander configured to convert thermal and kinetic energy of fluid in the tertiary thermal transfer circuit into another form of energy, optionally rotational kinetic energy.

9. The internal combustion engine of claim 8 wherein the tertiary thermal transfer circuit comprises: an expander bypass conduit configured to provide a bypass of the tertiary thermal transfer circuit away from the expander; and an expander bypass valve configured to enable control of flow of fluid into the expander bypass conduit.

10. The internal combustion engine of any of claims 4, 5, 8 and 9 wherein the expander comprises a turbine configured to convert thermal energy into rotational kinetic energy.

11. The internal combustion engine of any preceding claim wherein the primary thermal transfer circuit is configured to facilitate thermal transfer from the engine block by the provision of an engine block channel or channels for thermally conductive fluid that surround at least a portion of the cylindrical cavity.

12. The internal combustion engine of any preceding claim wherein the secondary thermal transfer circuit is configured to facilitate thermal transfer from both the cylinder head and the exhaust gas recirculation conduit by provision of one or more secondary circuit channels that surround at least a portion of the cylinder head and at least a portion of the exhaust gas recirculation conduit.

13. The internal combustion engine of any preceding claim wherein the secondary thermal transfer circuit further comprises a cylinder head bypass conduit configured to provide a bypass of the secondary thermal transfer circuit away from the cylinder head and the exhaust gas recirculation conduit, the cylinder head bypass conduit comprising a cylinder head bypass valve configured to control flow of fluid in the bypass conduit.

14. A machine comprising: the internal combustion engine of any preceding claim; a radiator configured to facilitate thermal transfer from the primary coolant circuit; and a pump configured to propel fluid to circulate around the primary transfer circuit.

15. The machine of claim 14 comprising the internal combustion engine of claim 2 or claim 6 or any claim dependent upon claim 2 or claim 6 and an after-treatment module comprising one or more of a diesel oxidation catalyst module, a diesel particulate filter module and a selective catalytic reduction module.

16. An internal combustion engine as hereinbefore described and with reference to the accompanying drawings.