SE540467C2

SE540467C2 - A cooling system for cooling charge air delivered to a combustion engine in a vehicle

Info

Publication number: SE540467C2
Application number: SE1551380A
Authority: SE
Inventors: Kardos Zoltan; Ekman Mats; Hall Ola
Original assignee: Scania Cv Ab
Priority date: 2015-10-27
Filing date: 2015-10-27
Publication date: 2018-09-18
Also published as: SE1551380A1

Abstract

The present invention relates to a. cooling system for cooling of charge air delivered to a combustion engine (2) in a vehicle. The vehicle comprises an air inlet line (7) configured to deliver charge air to the combustion engine (2), a low pressure compressor (6a) configured to compress the air in the air inlet line (7) in a first stage and a high pressure compressor (6b) configured to compress the charge air in the air inlet line (7) in a second stage. The cooling system comprises a charge air cooler (8) configured to cool the charge air in a position between the low pressure compressor (6a) and the high pressure compressor (6b) in the air inlet line (7) and a charge air cooler line (22) configured to receive coolant from the radiator line (20) and direct it through the charge air cooler (8). The first valve device (13, 24) is configured to direct at least a small coolant flow rate through the radiator line (20) and, via the charge air cooler line (22), to the charge air cooler (8) during all operating conditions of the combustion engine (2).

Description

A cooling system for cooling of charge air delivered to a combustion engine in a vehicle BACKGROUND OF THE INVENTION AND PRIOR ART The present invention relates to a cooling system for cooling of charge air delivered to a combustion engine in a vehicle according to the preamble of claim 1.

Twin turbo installations are usually used to increase the power of a combustion engine by supplying charge air of a high pressure to the combustion engine. In a twin turbo installation, the charge air is compressed in a first stage by a low pressure compressor and in a second stage by a high pressure compressor. The amount of charge air which can be received and compressed in the compressors depends on the specific volume of the charge air. The charge air leaving the low pressure compressor has a raised pressure and a raised temperature. In order to reduce the specific volume of the charge air and increase the amount of charge air which can be received and compressed in the high pressure compressor, the charge air can be cooled in a charge air cooler arranged in a position between the compressors. The charge air leaving the high pressure compressor can be cooled in a further charge air cooler, for example, by air of ambient temperature in order to decrease the specific volume of the charge air and increase the amount of charge air which can be delivered to the combustion engine.

US 2006/0195362 shows a circuit arrangement comprising a low-temperature circuit for cooling charge air that is fed, via an air inlet line, to a motor in a motor vehicle equipped with a turbocharger. In the charged air line the charge air is compressed in a first stage in a low-pressure turbocharger and in a second stage in a high-pressure turbocharger. To cool the charge air a first charge air cooler is provided downstream of the low-pressure turbocharger and upstream of the high-pressure turbocharger. A second charged air cooler is provided downstream of the high-pressure turbocharger and upstream of the motor.

SUMMARY OF THE INVENTION The object of the present invention is to provide a relatively simple cooling system in a vehicle providing an effective and reliable cooling of charge air in a position between two compressors in an air inlet line directing charge air to a combustion engine.

This object is achieved by the cooling system of the initially mentioned kind which is characterized by the features defined in the characterizing part of claim 1. In order to provide an effective cooling of charge air in a position between two compressors, it has to be cooled to a substantially constant low temperature. In a conventional cooling system for a combustion engine, a thermostat directs coolant to a radiator bypass line when the coolant has a lower temperature than a regulating temperature of the thermostat and to a radiator line when the coolant has a higher temperature than the regulating temperature. Thus, low temperature coolant from a radiator is not available in a conventional cooling system during all operating conditions. For this reason it is not possible to provide an effective cooling of charge air by coolant from a conventional cooling system.

In order to modify such a cooling system, the thermostat has been replaced by a first valve device which at all times can direct at least a small coolant flow to the radiator. Depending on this measure, cooled coolant from the radiator is always available during all operating condition of the combustion engine. The coolant flow from the radiator is directed to the charge air cooler where it cools the charge air. A small coolant flow to the charge air cooler is usually enough to cool the charge air to a low temperature before it is compressed in a second stage in the high pressure compressor. The small coolant flow may be less than 10 % of the entire coolant flow in the cooling system. Such a small coolant flow through the radiator can be cooled to a temperature corresponding to the temperature of the air flowing through the radiator. Consequently, it is possible with relatively small changes to modify a conventional cooling system for cooling of a combustion engine such that it is also capable of cooling charge air to a relatively low temperature between two compression stages in an air inlet line directing charge air to a combustion engine.

According to an embodiment of the invention, the first valve device is adjustable in a stepless manner. In this case, it is possible to direct the coolant flow to the radiator line and the radiator bypass line with a high accuracy.

According to an embodiment of the invention, the first valve device comprises a thermostat, a thermostat bypass line and a valve controlling the flow rate through the thermostat bypass line. When the coolant has a lower temperature than the regulating temperature of the thermostat, it is possible to open said valve and provide a small coolant flow through the thermostat bypass line and to the radiator. Alternatively, the first valve device is a three way valve having an inlet opening receiving coolant, a first outlet opening directing coolant to the radiator bypass line and a second outlet opening directing coolant to the radiator line. By such a three way valve, it is always possible to direct at least a small part of the coolant flow, via the second outlet opening, to the radiator.

According to an embodiment of the invention, the cooling system comprises a control unit configured to control the first valve device. The control unit may be configured to control the first valve device by means of information from a temperature sensor sensing the temperature of the coolant in a suitable line of the cooling system defining the temperature of the combustion engine. During operating conditions when the combustion engine has a too low temperature, the control unit controls the first valve device such that it directs a main part of the coolant flow to the radiator bypass line and a small part of the coolant flow to the radiator. The small part of the coolant flow from the radiator is used to cool the charge air in the charge air cooler. As the temperature of the combustion engine increases, the control unit controls the first valve device such that it directs a successively larger part of the coolant flow to the radiator such that the cooling system is able to cool the combustion engine to a desired operating temperature.

According to an embodiment of the invention, the cooling system comprises a second valve device configured to receive coolant from the radiator line and direct it to a charge air cooler line and /or a charge air cooler bypass line. When a large part or the entire coolant flow is directed to radiator, it is not suitable to direct the whole coolant flow from the radiator to the charge air cooler. In this case, the second valve device may direct a suitable part of the coolant flow from the radiator to the charge air cooler line and a remaining part of the coolant flow from the radiator to the charge air cooler bypass line.

According to an embodiment of the invention, the cooling system comprises a control unit configured to control second valve device. The same control unit may be used to control the first valve device and the second valve device. The control unit may be configured to control the second valve device by means of information from a temperature sensor sensing the temperature of the charge air in a position between the compressors. The temperature sensor may sense the temperature of the charge air upstream or downstream of the charge air cooler. Depending on the temperature of the charge air, the control unit may control the second valve device such that it directs a larger coolant flow rate to the charge air cooler when the temperature of the charge air is high and a smaller coolant flow rate to the charge air cooler when the temperature of the charge air is low.

According to an embodiment of the invention, the second valve device is adjustable in a stepless manner. In this case, it is possible to direct the coolant flow to the charge air cooler line and the charge air cooler bypass line with a high accuracy.

According to an embodiment of the invention, the second valve device is a three way valve. The three way valve may have one inlet opening receiving coolant from the radiator line, a first outlet opening directing coolant to the charge air cooler line and a second outlet opening directing coolant to the charge air cooler bypass line. The control unit may control the three way valve such that it directs a suitable part of the coolant flow from the radiator to the charge air cooler and a remaining part of the coolant flow to the charge air cooler bypass line.

Alternatively, the second valve device is a throttle valve arranged in the charge air cooler bypass line. In this case it is possible to adjust the flow resistance in the charge air cooler bypass line in relation to the flow resistance in the charge air cooler line. In case the throttle valve is adjusted such that it increases the flow resistance in the charge air cooler bypass line, a larger part of the coolant from the radiator will be directed to the charged air cooler. On the other hand, in case the throttle valve is adjusted such that it decreases the flow resistance in the charge air cooler bypass line, a smaller part of the coolant flow from the radiator will be directed to the charged air cooler.

According to another embodiment of the invention, the charge air cooler line directs the coolant from the charge air cooler to the engine inlet line. Thus, the coolant which has been used to cool the charge air in the charge air cooler is then used to cool the combustion engine. The charge air cooler bypass line may direct the coolant to the engine inlet line. Consequently, the cooled coolant from the radiator which is not directed to the charge air cooler is also used to cool the combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS In the following preferred embodiments of the invention is described, as examples, with reference to the attached drawings, in which: Fig. 1 shows a cooling system according to a first embodiment of the invention, Fig. 2 shows a cooling system according to a first embodiment of the invention and Fig. 3 shows a cooling system according to a third embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 shows a cooling system for a combustion engine 2 powering a schematically indicated vehicle 1. The combustion engine is here exemplified as a diesel engine 2. The diesel engine 2 may be intended to power a heavy vehicle 1. The exhaust gases from the cylinders of the diesel engine 2 are led via an exhaust manifold 3 to an exhaust line 4. The diesel engine 2 is provided with a low pressure turbo unit comprising a turbine 5a and a compressor 6a, and a high pressure turbo unit comprising a turbine 5b and a compressor 6b. The exhaust gases are initially led, via a first part 4a of an exhaust line 4, to the turbine 5b of the high pressure turbo unit. The high pressure turbine 5b is thus provided with driving power which is transmitted, via a connection, to the compressor 6b of the high pressure turbo unit. The exhaust gases are led thereafter via a second part 4b of the exhaust line 4 to the turbine 5a of the low pressure turbo unit. The turbine 5a is thus provided with driving power which is transmitted, via a connection, to the compressor 6a of the low pressure turbo unit. The low pressure compressor 6a drawn air into an air inlet line 7. The air inlet line 7 comprises a first part 7a with air at ambient pressure p0. The air in the inlet line 7 is compressed in a first stage by the low pressure compressor 6a to a first charge pressure pi. The air inlet line 7 comprises a second part 7b located between the low pressure compressor 6a and the high pressure compressor 6b provided with charged air at the first charge pressure p1. The charge air is cooled in a first charge air cooler 8. The cooled charged air is compressed in a second stage in the high pressure compressor 6b. The air in the air inlet line 7 is cooled in a second stage in a second charge air cooler 9 in a position downstream of the high pressure compressor 6b before it is directed to the combustion engine 2. The second charge air cooler 9 is arranged in a front position of the vehicle 1 where the charge air is cooled by air of ambient temperature.

The vehicle 1 comprises a cooling system comprising an engine inlet line 10 provided with a coolant pump 11 circulating a coolant in the cooling system. When the coolant has circulated through the combustion engine 2, it is received in an engine outlet line 12. A first valve device 13 is arranged at an end of the engine outlet line 12. The first valve device 13 comprises a conventional thermostat 13a which opens when the coolant in the engine outlet line 12 has a temperature above a regulating temperature of the thermostat 13a. The first valve device 13 comprise further a thermostat bypass line 13b and a valve 13c controlled by a control unit 14. The valve 13c is adjustable in a stepless manner between a closed position and a fully open position. A temperature sensor 15 senses the temperature of the coolant in the engine outlet line 12. The coolant temperature in the engine outlet line 12 corresponds to the temperature of the combustion engine 2.

The cooling system comprises a radiator 17 arranged at a front position of the vehicle in a position downstream of the second charge air cooler 9 with respect to the intended air flow direction through the second charge air cooler 9 and the radiator 17. A radiator fan 18 and the ram air of the vehicle 1 provide a cooling air flow through the second charge air cooler 9 and the radiator 17. The cooling system comprises a radiator bypass line 19 directing coolant past the radiator 17 and a radiator line 20 directing coolant through the radiator 17. In case the coolant in the engine outlet line 12 has a lower temperature than the regulating temperature of the thermostat 13a, the thermostat 13a is in a closed position in which it directs the entire coolant flow to the radiator bypass line 19. The radiator bypass line 19 leads the coolant to the engine inlet line 10. In order to provide a coolant flow through the radiator line 20 during all operating condition, the control unit 14 may open the valve 13c and provide a coolant flow through the thermostat bypass line 13b when the thermostat 13a is closed position. In this case, a relatively small first part of the coolant flow in the engine outlet line 12 is directed to the radiator line 20 and a remaining second relatively large part of the coolant flow is directed to the radiator bypass line 19. Since the first part of the coolant flow is cooled in the radiator 17, it has a lower temperature than the second part of the coolant flow directed through the radiator bypass line 19. Such a small coolant flow through the radiator 17 will be cooled to a temperature which substantially corresponds to the temperature of the air flowing through the radiator.

The cooling system comprises a second valve device in the form of a three way valve 21 controlled by the control unit 14. The three way valve 21 an inlet opening receiving coolant from the radiator line 20. The control unit 14 may adjust the three way valve 21 such that it directs a part of the coolant flow from the radiator line 20 to the charge air cooler line 22 and a remaining part of the coolant flow from the radiator line 20 to the charge air cooler bypass line 23. Alternatively, the control unit 14 may adjust the three way valve 21 such that it receives the coolant flow from the radiator line 20 and a part of the coolant flow in the radiator bypass line 19, via the charge air cooler bypass line 23, and directs a mixture of these coolant flows to the charge air cooler line 22. The charged air cooler line 22 directs the coolant through the first charge air cooler 8 and to a first position 10a of the engine inlet line 10. The charge air bypass line 23 directs the coolant to a second position 10b of the engine inlet line 10 located upstream of said first position 10a. Said first position 10a and said second position of the engine inlet line 10 is located upstream of the coolant pump 11.

During operation of the diesel engine 2, exhaust gases flow through the exhaust line 4 and drive the turbines 5a, b of the turbo units. The turbines 5a, b are thus provided with driving power which drives the compressors 6a, b of the turbo units. The compressor 6a of the low pressure turbo unit draws surrounding into the air inlet line 7 and compresses the air in a first stage. The air thus acquires a raised pressure and a raised temperature. The charge air is cooled in the first charge air cooler 8 by the coolant flow in the charge air cooler line 22. The air maintains its pressure during the cooling process in the first charge air cooler 8. However, air which is cooled assumes a lower specific volume, i.e. occupies a smaller volume per unit weight. The air thus becomes more compact. A compressor normally has a space with a constant volume in which to receive and compress air. The cooling of the air in the first charge air cooler 8 thus makes it possible for a larger amount of air to be compressed in the compressor 6a of the high pressure turbo unit. The air is here compressed in a second stage so that it assumes a further raised pressure. The charge air is led thereafter through the second charge air cooler 9, in which it is cooled in a second stage by air of ambient temperature. The charge air is cooled in the second charge air cooler 9 to a temperature close to ambient temperature. Furthermore, the cooling of the air in the first charge air cooler 8 eliminates the risk that the high pressure compressor 6b, the third part of the air line 7c and the second air cooler 9 will be subjected to too high charged air temperatures.

The control unit 14 receives substantially continuously information from the temperature sensor 15 about the temperature of the coolant in the engine outlet line 12 which corresponds to the temperature of the combustion engine 2. Furthermore, the control unit 14 receives substantially continuously information from the temperature sensor 16 about the temperature of the charge air when it leaves the low pressure compressor 6a. In view of this information, it is possible for the control unit 14 to control the valve 13c in the thermostat bypass line 13b such that at least a small coolant flow is directed to the radiator 17 even when the coolant has a lower temperature than a regulating temperature of the thermostat 13a. The control unit 14 receives substantially continuously information from the temperature sensor 16 about the temperature of the charge air when it leaves the low pressure compressor 6a. In view of this information, the control unit 14 estimates a suitable cooling effect of the charge air in the first charge air cooler 8 whereupon it controls the three way valve 21 such that it directs a suitable coolant flow rate to the first charge air cooler 8. The cooling effect of the charge air in the first charge air cooler 8 may often be of the same magnitude as the cooling effect of the coolant in the radiator 9.

A conventional cooling system for a supercharged combustion engine provided with a twin turbo installation can relatively easily be modified to the cooling system above. A primary step is to arrange an intermediate charge air cooler 8 in the air inlet line 7 in a position between the low pressure compressors 6a and the high pressure compressor 6b. Further, it needs a first valve device directing a coolant flow to the radiator 17 when the coolant has a lower temperature than a regulating temperature of the thermostat 13a. In this case, the first valve device comprises a thermostat bypass line 13b and a valve 13c by which it is possible to provide a controlled coolant flow to the radiator 17. Furthermore, the cooling system needs a second valve device which may be designed as a three way valve 21 directing a suitable coolant flow rate from the radiator 17 to the intermediate charge air cooler line 8. Finally, the control unit 14 needs software for the control of the first valve device 13 and the second valve device 21.

Fig. 2 shows an alternative embodiment of the cooling system. In this case, the first cooling device is designed as a three way valve 24. The control unit 14 controls the three way valve 24 such that it directs the coolant flow in the engine outlet line 12 to radiator bypass line 19 and the radiator line 20 depending on the temperature of the coolant in the engine outlet line 12. During all operating condition, it directs at least a small part of the coolant flow to the radiator line 20. In this case, the second valve device is designs as a throttle valve 25 by which it is possible to control the flow resistance in the charge air cooler bypass line 23 in relation to the constant flow resistance in the charge air cooler line 22. By increasing the flow resistance in the charge air cooler bypass line 23, a larger part of the coolant flow from the radiator 17 will be directed to the charge air cooler 8. By decreasing the flow resistance in the charge air cooler bypass line 23, a smaller part of the coolant flow from the radiator 17 will be directed to the charge air cooler 8.

Fig. 3 shows an alternative embodiment of the cooling system. In this case, the first valve device is a three way valve 24 and the second valve device is a three way valve 21. In this case, the radiator bypass line 19 directs coolant from the first three way valve 24 to the second three way valve 21. The control unit 14 controls the first three way valve 24 such that directs at least a small coolant flow through the radiator line 20 and ,via the charge air cooler line 22, to the charge air cooler 8 during all operating conditions of the combustion engine 2. During certain operating condition, the control unit 14 may control the second three way valve 21 such that it directs a part of the coolant flow from the radiator line 20 to the air cooler line 22 and a remaining part to the charge air cooler bypass line 23. Furthermore, the control unit 14 may control the second three way valve 21 such that it directs a part of the coolant flow in the radiator bypass line 19 to the to the charge air cooler bypass line 23 and a remaining part to the air cooler line 22. Thus, it is also in this case possible to provide a coolant flow to the charged air cooler 8 of a desired flow rate and temperature in the form of a mixture of the cooled coolant from the radiator line 20 and the warm coolant from the radiator bypass line 19.

The invention is in no way limited to the embodiments described with reference to the drawings but may be varied freely within the scopes of the claims.

Claims

1. A cooling system for cooling of charge air delivered to a combustion engine (2) in a vehicle, wherein the vehicle comprises an air inlet line (7) configured to deliver charge air to the combustion engine (2), a low pressure compressor (6a) configured to compress the air in the air inlet line (7) in a first stage and a high pressure compressor (6b) configured to compress the charge air in the air inlet line (7) in a second stage, and wherein the cooling system comprises a radiator line (20) configured to direct coolant through a radiator (17), a radiator bypass line (19) directing coolant past the radiator (17), a first valve device (13, 24) configured to receive coolant from a coolant line (12) in the cooling system and direct it to the radiator bypass line (19) and /or the radiator line (20), and an engine inlet line (10) configured to receive coolant from the radiator line (20) and /or the radiator bypass line (19) and direct it to the combustion engine (2), characterized in that the cooling system comprises a first charge air cooler (8) configured to cool the charge air in a position between the low pressure compressor (6a) and the high pressure compressor (6b) in the air inlet line (7) and a charge air cooler line (22) configured to receive coolant from at least the radiator line (20) and direct it through the charge air cooler (8), and that the first valve device (13, 24) is configured to direct at least a small coolant flow rate through the radiator (17) via the radiator line (20) and to the charge air cooler (8) via the charge air cooler line (22), during all operating conditions of the combustion engine (2).

2. A cooling system according to claim 1, characterized in that the first valve device (13, 24) is adjustable in a stepless manner.

3. A cooling system according to claim 1 or 2, characterized in that the first valve device (13) comprises a thermostat (13a), a thermostat bypass line (13b) and a valve (13c) controlling the coolant flow through the thermostat bypass line (13c).

4. A cooling system according to claim 1 or 2, characterized in that the first valve device is a three way valve (24).

5. A cooling system according to any one of the preceding claims, characterized in that it comprises a control unit (14) configured to control first valve device (13, 24).

6. A cooling system according to claim 5, characterized in that the control unit (14) is configured to control the first valve device (13, 24) by means of information from a temperature sensor (15) sensing the temperature of the coolant in a line (12) in which the coolant has a corresponding temperature as the combustion engine (2).

7. A cooling system according to any one of the preceding claims, characterized in that it comprises a second valve device (21, 25) configured to receive coolant from the radiator line (19) and direct it to charge air cooler line (22) and /or a charge air cooler bypass line (23).

8. A cooling system according to claim 7, characterized in that it comprises a control unit (14) configured to control the second valve device (21, 25).

9. A cooling system according to claim 8, characterized in that the control unit (14) is configured to control the second valve device (21, 25) by means of information from a temperature sensor (16) sensing the temperature of the charge air in a position between the compressors (6a, 6b).

10. A cooling system according to any one of the claims 7 to 9, characterized in that the second valve device (13) is adjustable in a stepless manner.

11. A cooling system according to any one of the claims 7 to 10, characterized in that the second valve device is a three way valve (21).

12. A cooling system according to any one of the claims 7 to 10, characterized in that the second valve device is a throttle valve (25) arranged in the charge air cooler bypass line (23).

13. An arrangement according to any one of the preceding claims, characterized in that the charge air cooler line (22) directs the coolant from the charge air cooler (8) to the engine inlet line (10).

14. An arrangement according to any one of the preceding claims 7 to 12, characterized in that the charge air cooler bypass line (23) directs the coolant to the engine inlet line (10).