Cooling system for a vehicle

Abstract

A cooling system 10 for the intake gas of an internal combustion engine of a vehicle, comprises a condenser (heat exchanger 44) positioned in the path of at least some of the engine exhaust gases, a receptacle (condensate tank 46) configured to collect water from the condenser 44, a pump 48 to pump condensed water from the receptacle, and at least one spray head 34 connected to the pump to spray the condensed water from the receptacle 46 onto the exterior of a heat exchanger (intercooler 30). The engine preferably comprises a supercharger, optionally a turbocharger (26, 28), an exhaust gas recirculation (EGR) passage, and may be fuelled by hydrogen. The system provides a supply of cooling water, without having to rely on a refillable tank, and reduces the water content of any EGR gases fed back into the combustion chamber which may cause contamination of engine fluids and corrosion.

Description

TECHNICAL FIELD The present disclosure relates to a cooling system for a vehicle. Aspects of the invention relate to a cooling system and method for the intake gas of an internal combustion engine, to an internal combustion engine, and to a vehicle comprising an internal combustion engine in accordance with the invention. BACKGROUND Hydrogen combustion in an internal combustion engine can produce significant water vapour quantity compared to conventional spark ignition engines using gasoline as a fuel, due to the higher dew point temperature of hydrogen gas compared with gasoline. Therefore, the management of water condensate is necessary. Additionally, if an exhaust gas recirculation (EGR) system is fitted to a hydrogen-fuelled engine, the high-water content in the exhaust gas can be recirculated back into the combustion chamber which can eventually lead to contamination of engine fluids (e.g., engine oil) and corrosion of ferritic based components. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION In accordance with a first aspect of the invention, a cooling system for the intake gas of an internal combustion engine, the system comprises a condenser positioned in the path of at least some of the engine exhaust gases, a receptacle configured to collect water condensed in the condenser, a pump configured to pump condensed water from the receptacle, and optionally at least one spray head connected to the pump and configured to spray the condensed water pumped from the receptacle onto at least one heat exchanger. The invention provides a supply of cooling water for spraying onto the heat exchanger without having to rely on a refillable tank. The engine may comprise a supercharger, optionally a turbocharger (26, 28), wherein said at least one heat exchanger comprises an intercooler positioned downstream of the supercharger. The at least one heat exchanger onto which the at least one spray head may be configured to spray the condensed water may comprise the condenser. This enhances the cooling of the exhaust gases by the condenser, which reduces the temperature of the condensed water and / or allows the use of a smaller condenser. The cooling system may comprise a plurality of spray heads connected to the pump and configured to spray the condensed water pumped from the receptacle onto at least one heat exchanger. This assists in targeting the areas of the heat exchanger over which the condensed water is sprayed. The cooling system may comprise a plurality of heat exchangers, onto which the condensed water can be sprayed. The cooling system may comprise an intercooler for the intake gas, and the at least one heat exchanger onto which the at least one spray head may be configured to spray the condensed water comprises the intercooler. Spraying the condensed water onto the intercooler enhances the cooling of intake air supplied to the engine, thereby reducing its temperature and / or allowing the use of a smaller intercooler. The condenser may be positioned in a bypass passage of an engine exhaust. By positioning the condenser in a bypass passage of the engine exhaust, only a portion of the engine exhaust gases pass through the condenser. This ensures that only the proportion of the exhaust gases required for condensing the desired amount of water needs to pass through the condenser, which in turn minimises the size of the required condenser. The bypass passage may bypass a catalytic converter for engine outlet gases. This ensures that the size of the catalytic converter can be minimised, to handle the anticipated flow of exhaust gases. The condenser may be positioned downstream of a catalytic converter for the engine outlet gases. Positioning the bypass passage downstream of a catalytic converter reduces the levels of undesirable components (e.g., NOx components) in the portion of the exhaust gas passing through the condenser, and therefore the levels of undesirable components in the condensed fluid which is ultimately sprayed onto the heat exchanger. In addition, many catalytic converters increase the amount of water vapour in the exhaust gases. The cooling system may comprise an exhaust gas recirculation passage extending between an engine exhaust passage and an engine intake passage. Positioning a condenser in the path of at least some of the engine exhaust gases reduces the water content of the exhaust gases. This is particularly useful for engines which burn fuels, e.g. hydrogen, which produce higher levels of water vapour when combusted, as compared with hydrocarbon fuels, and which might otherwise eventually lead to contamination of engine fluids (e.g. engine oil) and corrosion of ferritic based components. The exhaust gas recirculation passage may comprise an exhaust gas recirculation cooler and the at least one heat exchanger onto which the at least one spray head may be configured to spray the condensed water comprises the exhaust gas recirculation cooler. This cools the temperature of recirculated exhaust gas entering the engine, thereby helping to keep the temperature of the air / recirculated gas mixture to the appropriate temperature. The invention also includes an internal combustion engine comprising a cooling system as discussed herein. The engine may comprise a supercharger. The supercharger may comprise a turbocharger. The turbocharger has a compressor stage disposed in the intake gas and a turbine stage in the exhaust gas and the exhaust gas recirculation passage may be either a low pressure circuit extending from upstream of the turbine stage and downstream of the compressor stage or a high pressure circuit extending from downstream of the turbine stage and upstream of the compressor stage. The engine may be configured to use hydrogen as a fuel. The invention also includes a vehicle comprising an internal combustion engine in accordance with the present invention. An engine or vehicle according to the invention may comprise an intercooler downstream of the supercharger and at least one spray head connected to the pump may be configured to spray the condensed water pumped from the receptacle onto the intercooler. The invention also includes a method of cooling the intake gas of an internal combustion engine. The method comprises the steps of: condensing, using a condenser, water from at least some of the engine exhaust gases; collecting the condensed water in a receptacle; pumping the condensed water from the receptacle; and spraying, using at least one spray head connected to the pump, the condensed water pumped from the receptacle onto at least one heat exchanger. The method may further comprise any steps which the cooling system as described herein is configured to perform. 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: Figures 1 to 5 show schematic representations of an internal combustion engine having a cooling system for the intake gas in accordance with embodiments of the invention; and Figure 6 shows a flow diagram of a method according to a further embodiment of the invention. DETAILED DESCRIPTION Figure 1 is a schematic representation of an embodiment of a cooling system 10 for the intake gas of a turbocharged internal combustion engine whose cylinder head 12 is also shown schematically. In this particular embodiment, the cylinder head 12 is for an engine having six identical cylinders 14 each having two inlet ports 16 and two outlet ports 18, the opening of each of the ports being controlled by a respective valve (not shown) in a conventional manner. The engine is a hydrogen-fuelled engine and hydrogen is injected into the engine cylinders 14 in a conventional manner by means of injectors (not shown) connected between a source of hydrogen and each of the engine cylinders 14. The inlet ports 16 are fed with air from an engine intake manifold shown schematically at 20 and the airflow into the engine cylinders 14 is controlled by an adjustable throttle 22 located in the intake manifold. Exhaust gases are exhausted from the outlet ports 18 into an exhaust gas manifold shown schematically at 24. As in a conventional turbocharged engine, the exhaust gases from the engine drive a turbine stage 26 of the turbocharger located downstream of the exhaust manifold, which in turn drives a compressor stage 28 of the turbocharger located upstream of the inlet manifold 20. The temperature of the inlet air in the inlet manifold 20 increases after being compressed by the compressor 28 and so, as for a conventional turbocharged engine, the compressed air is passed through an intercooler 30 in order to reduce its temperature, thereby increasing its density in order to increase the amount of fuel which can be ignited in the engine. In that respect, the intercooler is referred to as being downstream of the turbocharger, even though it is upstream of the turbine stage. The intercooler is conventional and has inlet and outlet pipes 31a, 31 b for liquid coolant. Additional cooling of the intercooler is achieved by spraying water 32 from a plurality of water sprays 34 onto the exterior of the intercooler 30. The water supplied to the sprays 34 is obtained by condensing water vapour in the engine exhaust gases, which will be explained in more detail below. As further shown in Figure 1, the exhaust gases exiting the turbine 26 pass along an exhaust pipe 36 and sequentially through a catalytic converter 38 and a selective catalytic reduction (SCR) unit 40 located in the exhaust pipe and are then exhausted to atmosphere. A portion of the exhaust gases is diverted from the main exhaust gas flow by a circuit 42 extending from a position in the exhaust 36 between the catalytic converter 38 and the SCR unit 40 to a position downstream of the SCR unit 40. The diverted portion of the exhaust gases passes over a heat exchanger 44 and then rejoins the main exhaust gas flow. The heat exchanger is conventional and has inlet and outlet pipes 45a, 45b for liquid coolant. As explained previously, the engine is a hydrogen-fuelled engine, and consequently the exhaust gases will contain relatively large amounts of water vapour as compared with the exhaust gases from conventional gasoline engines. The water vapour in the bypass circuit 42 is condensed by the heat exchanger 44 and is collected in a water condensate tank 46. A pump 48 is connected to the water condensate tank 46 and can be operated, when desired, to pump water condensed in the tank to spray heads 34 and thereby to spray water 32 onto the exterior of the intercooler 30 in order to provide additional cooling of the compressed air passing through the inlet manifold 20. Figure 2 is a schematic representation of a different embodiment of a cooling system 110 for the intake gas of a turbocharged internal combustion engine whose cylinder head 112 is also shown schematically. The engine configuration of the embodiment of Figure 2 is very similar to that of the embodiment of Figure 1, and corresponding features are identified by the same reference numeral, increased by 100. Different from Figure 1, however, a high-pressure exhaust gas recirculation (EGR) passage 150 extends between the engine exhaust 136 at a position upstream of the turbine 126 and the intake manifold 120 at a position downstream of the compressor 128 and the throttle 122. Exhaust gas recirculated through the EGR passage 150 passes over a conventional heat exchanger 152 having inlet and outlet pipes 153a, 153b for liquid coolant. The heat exchanger 152 reduces the temperature of the recirculated exhaust gases and causes water vapour within the gases to condense. Removal of water vapour from the recirculated exhaust gases reduces the occurrence of contamination of engine fluids (e.g., engine oil) and corrosion of ferritic based components, which are more likely to occur in engines fuelled by hydrogen, whose exhaust gases have a relatively high water vapour content. After condensing the water vapour in the heat exchanger 152, the recirculating exhaust gases are then fed to the inlet manifold 120 and then to the engine and the flow of recirculated exhaust gases through the EGR passage 150 is controlled by means of an exhaust gas recirculation (EGR) valve 154. The exhaust gases which are not recirculated through the EGR passage 150 pass sequentially through the catalytic converter 138 and the selective catalytic reduction (SCR) unit 140 and are then exhausted to atmosphere. As in Figure 1, a portion of those exhaust gases is diverted from the main exhaust gas flow to pass over the heat exchanger 144. As explained previously, the water vapour in the bypass circuit 142 is condensed by the heat exchanger 144 and is collected in a water condensate tank 146. The pump 148 pumps water condensed in the tank to spray heads 158 in order to spray water 160 onto the exterior of the heat exchanger 152 in order to provide additional cooling of the exhaust gas passing through the EGR passage 150. Figure 3 is a schematic representation of a further embodiment. The engine configuration of the embodiment of Figure 3 is very similar to that of Figures 1 and 2, and corresponding features are identified by the same reference numeral, preceded by a 2. However, here low-pressure exhaust gas recirculation (EGR) passage 250 extends from a position downstream of the turbine 226, between the turbine 226 and the catalytic converter 238 in the exhaust 236, to the intake manifold 220 at a position upstream of the compressor 230. Exhaust gas recirculated through the EGR passage 250 passes over a conventional heat exchanger 252 having inlet and outlet pipes 253a, 253b for liquid coolant. As in Figure 2, the exhaust gases which are not recirculated through the EGR passage 250 pass sequentially through the catalytic converter 238 and the selective catalytic reduction (SCR) unit 240 and are then exhausted to atmosphere. A portion of those exhaust gases is diverted over the conventional heat exchanger 244 and the water vapour in the bypass circuit 242 is condensed by the heat exchanger 244 and is collected in a water condensate tank 246. Pump 248 is connected to the water condensate tank 246 and can be operated, when desired, to pump water condensed in the tank to spray heads 258 which are positioned to spray water 260 onto the exterior of the heat exchanger 252 in order to provide additional cooling of the exhaust gas passing through the EGR passage 250. Figure 4 is a schematic representation of a yet further embodiment of a cooling system 21 O’. The arrangement is very similar to that of Figure 3. The only difference between the embodiments of Figures 3 and 4 is that the spray heads 258 in the embodiment of Figure 3 which are configured to spray water 260 onto the exterior of the heat exchanger 252 are omitted and instead the pump 248 can be operated, when desired, to pump water condensed in the water condensate tank 246 to spray heads 264 in order to spray water 266 onto the exterior of the heat exchanger 230 in the intake manifold 220. The yet further embodiment shown in Figure 5 is effectively a combination of the embodiments of Figures 3 and 4, in that the pump 248 is configured to pump water to the spray heads 258 to spray water 260 onto the exterior of the heat exchanger 252 in the EGR passage 250, as in the embodiment of Figure 3, and is also configured to pump water to the spray heads 264 to spray water 266 onto the exterior of the heat exchanger 230 in the intake manifold 220, as in the embodiment of Figure 4. Figure 6 shows a flow diagram of a method of cooling the intake gas of an internal combustion engine which may be undertaken by the cooling system according to embodiments of the invention. The method comprises a step 601 of condensing, using a condenser, water from at least some of the engine exhaust gases. The method further comprises a step 602 of collecting the condensed water in a receptacle. The method further comprises a step 603 of pumping the condensed water from the receptacle. The method further comprises a step 604 of spraying, using at least one spray head connected to the pump, the condensed water pumped from the receptacle onto at least one heat exchanger cooling the intake gas of the engine. In a yet further embodiment not illustrated in the drawings, at least one heat exchanger onto which the spray heads (34,158, 258 264) is configured to spray the condensed water may include the condenser (44, 144, 244). It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A cooling system for the intake gas of an internal combustion engine, the system comprising a condenser positioned in the path of at least some of the engine exhaust gases, a receptacle configured to collect water condensed in the condenser, a pump configured to pump condensed water from the receptacle, and at least one spray head connected to the pump and configured to spray the condensed water pumped from the receptacle onto at least one heat exchanger associated with the intake gas of the engine.

2. A cooling system as claimed in claim 1, wherein the engine comprises a supercharger, the supercharger optionally comprising a turbocharger, wherein said at least one heat exchanger comprises an intercooler positioned downstream of the supercharger.

3. A cooling system as claimed in claim 1 or 2, comprising a plurality of said spray heads connected to the pump.

4. A cooling system as claimed in claim 3, comprising a plurality of heat exchangers, onto which the condensed water can be sprayed by said plurality of said spray heads.

5. A cooling system as claimed in any of the preceding claims, wherein the condenser is positioned downstream of a first catalytic converter for the engine outlet gases.

6. A cooling system as claimed in any of the preceding claims, wherein the condenser is positioned in a bypass passage of an engine exhaust.

7. A cooling system as claimed in claim 6, wherein the bypass passage bypasses a second catalytic converter for engine outlet gases.

8. A cooling system as claimed in any of the preceding claims, comprising an exhaust gas recirculation passage extending between an engine exhaust passage and an engine intake passage.

9. A cooling system as claimed in claim 8, wherein the exhaust gas recirculation passage comprises an exhaust gas recirculation cooler and wherein the at least one heat exchanger onto which the at least one spray head is configured to spray the condensed water comprises the exhaust gas recirculation cooler.

10. A cooling system as claimed in claim 8 or 9 when dependent on claim 2, wherein the supercharger is a turbocharger having a compressor stage disposed in the intake gas and a turbine stage in the exhaust gas and wherein the exhaust gas recirculation passage is either a low pressure circuit extending from upstream of the turbine stage and downstream of the compressor stage or a high pressure circuit extending from downstream of the turbine stage and upstream of the compressor stage.11, A cooling system as claimed in any preceding claim, wherein the at least one heat exchanger onto which the at least one spray head is configured to spray the condensed water comprises the condenser.

12. An internal combustion engine comprising a cooling system as claimed in any of the preceding 5 claims.

13. An internal combustion engine according to claim 12 wherein the internal combustion engine is configured to use hydrogen as a fuel.10 14. A vehicle comprising an internal combustion engine according to claim 12 or 13.

15. A method of cooling the intake gas of an internal combustion engine, the method comprising thesteps of:condensing, using a condenser, water from at least some of the engine exhaust gases;15 collecting the condensed water in a receptacle;pumping the condensed water from the receptacle; andspraying the condensed water pumped from the receptacle onto at least one heat exchanger.

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