SE534872C2 - Arrangements for cooling compressed air and / or recirculating exhaust gases led to an internal combustion engine - Google Patents

Abstract

The present invention relates to an arrangement for cooling at least one medium which is fed to an internal combustion engine (2). The arrangement comprises a conduit (8, 11) adapted to direct the medium to the internal combustion engine (2) and at least one cooler (9, 15) for cooling the medium in the conduit (8, 11). The arrangement comprises a cooling circuit with a circulating refrigerant which is adapted to the second phase during operation, fuels (24, 25, 33, 34) which are adapted to provide operation of the cooling circuit mainly by means of heat energy from a heat source and an evaporator (16) which is arranged line (8, 11) in a position downstream of the above-mentioned cooler (9, 15) with respect to the direction of destruction of the medium fl in the line (8, 11) so that the medium is cooled in a final step on the evaporator (16) before being led to the internal combustion engine (2). (Fia 1)

Description

25 30 35 53¿l B72 to a temperature exceeding the ambient temperature by about 10-15 ° C. The recirculating exhaust gases and the compressed one are thus cooled to a temperature which is dependent on the ambient temperature. On occasions when the environment has a high temperature, a significantly worse cooling is thus obtained than when the environment has a low temperature.

SUMMARY OF THE INVENTION The object of the present invention is to provide an arrangement which cools compressed air and / or recirculating exhaust gases which are led to an internal combustion engine in a relatively simple and economical manner to a desired low temperature even when the ambient air has a relatively high temperature.

This jam is achieved with the arrangement of the kind mentioned in the introduction, which is characterized by the features stated in the characterizing part of claim 1. According to the invention, the compressed air and / or the recirculating exhaust gases are cooled in at least one stage by a cooler, which can with the aid of lu fi or a circulating coolant. The compressed air and / or the recirculating exhaust gases can thus be given a relatively low temperature before it is cooled in a final step in an evaporator of a cooling circuit with a phase-changing cooling medium. Such a cooling circuit thus only needs to be used to cool the compressed air and / or the recirculating exhaust gases in a final step. Thus, the cooling circuit can provide a cooling of the medium to a temperature corresponding to or below the ambient temperature without being given too large dimensions. Heat energy is used to drive the cooling circuit. There is plenty of excess heat in connection with a dry burning engine.

By utilizing such a reliable energy source, the cooling circuit can be operated in a very - economical way. The compressed air and the recirculating exhaust gases can be cooled separately in their respective front or in a common evaporator after they have been mixed with each other.

According to an embodiment of the present invention, said propellant comprises a steam generator in which the refrigerant is adapted to be heated by said heat source to a temperature at which it is evaporated. With the help of a steam generator, a relatively large amount of heat energy can be absorbed from a heat source in a very efficient manner when the refrigerant is evaporated. Said propellant advantageously comprises an ejector means which is adapted to mix gaseous refrigerant from the evaporator with gaseous refrigerant from the steam generator. The ejector means may be an ejector pump or a venturi having a tapered portion through which the gaseous refrigerant from the steam generator flows through at a high speed. This creates a low static pressure inside the ejector means so that refrigerant from the dry evaporator can be sucked in and mixed with refrigerant from the steam generator. The ejector means thus enables mixing of refrigerant from the evaporator which has a low pressure with the refrigerant fi from the steam generator which has a significantly higher pressure. Because the ejector means has the ability to suck refrigerant from the evaporator, a circulation of refrigerant to and from the evaporator can be created which enables cooling of the compressed air and / or the recirculating exhaust gases in the evaporator. According to another preferred embodiment of the present invention, the cooling circuit comprises a condenser where the cooling medium from the ejector means is adapted to be cooled to a temperature at which it condenses. In a closed cooling circuit, a circulating refrigerant evaporated in an evaporator must be returned to a liquid state in a condenser. The cooling circuit may comprise a manifold arranged downstream of the condenser, which comprises a first line with a pump which pumps liquid refrigerant from the condenser to the steam generator and a second line with an expansion valve which directs liquid refrigerant from the condenser to the evaporator used for the evaporator. to absorb heat from the heat source for operation of the cooling circuit while the refrigerant which is led to the dry evaporator is used to cool the compressed heat and / or the recirculating exhaust gases in the evaporator.

According to a preferred embodiment of the present invention, the arrangement comprises a control unit which is adapted to control the drive of the cooling circuit.

The control unit can be a computer unit with a suitable software. The control unit can appreciate when the cooling circuit needs to be used. During certain shit cases, it may be sufficient to cool the compressed air and / or the recirculating exhaust gases in said cooler. The cooling circuit should at least not be activated on occasions when there is a risk that the compressed air and / or the recirculating exhaust gases will be cooled to a temperature below 0 ° C. In this case, there is a risk of ice formation inside the radiator and that the fate of the internal combustion engine is stopped. The control unit can receive information from, for example, a sensor that senses the compressed air and / or the recirculating exhaust gas temperature or that it has cooled in the radiator or the ambient temperature to estimate whether the cooling circuit should be activated or not. 10 15 20 25 30 35 534 B72 According to a preferred embodiment of the present invention, the compressed air and / or the recirculating exhaust gases are adapted to be cooled directly or indirectly by air with ambient temperature in said cooler. The cooler can thus be air-cooled and permeated by air with ambient temperature or liquid-cooled and cooled by a circulating coolant which is cooled by lu fi with ambient temperature. With such a cooler, the compressed air and / or the recirculating exhaust gases can be cooled to a relatively low temperature relative to the ambient temperature before the final cooling in the evaporator. Thus, the cooling circuit can be made rather small.

According to an embodiment of the present invention, said steam generator is arranged in a position so that it absorbs heat from the exhaust gases in an exhaust line of the internal combustion engine. The exhaust gases from an internal combustion engine are a reliable source of energy that can be used to advantage to drive the cooling circuit. Alternatively, the steam generator may be arranged in a position so that it absorbs heat from the compressed air and / or the recirculating exhaust gases in said line in a position upstream of the radiator. Thus, the compressed air and / or the recirculating exhaust gases can deliver heat energy to the steam generator and thus be cooled in a first step; This eases the load on the subsequent regular radiator. According to a further alternative, the steam generator can be arranged in a position so that it absorbs heat from a coolant circulating in a cooling system which cools the internal combustion engine. The coolant in the cooling system has a constant high temperature. It is thus suitable for use as a heat source to evaporate the refrigerant in the steam generator. The cooling system's ordinary cooler is hereby relieved.

BRIEF DESCRIPTION OF THE DRAWINGS A Exemplary embodiments of the invention are described by way of example with reference to the accompanying drawings, in which: Fig. 1 shows an arrangement for cooling compressed lu fi and recirculating exhaust gases which are led to a dry combustion engine, Pig. Fig. 2 shows the ejector pump in Fig. 1 in more detail and Fig. 3 shows an alternative arrangement for cooling compressed air and recirculating exhaust gases which are led to an internal combustion engine. 10 15 20 25 30 35 534 B72 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 shows a vehicle I driven by a supercharged internal combustion engine 2. The vehicle 1 may be a heavy vehicle driven by a supercharged diesel engine. The exhaust gases from the cylinders of the internal combustion engine 2 are led, via an exhaust gas collector 3, to an exhaust line 4.

The exhaust gases in the exhaust line 4, which have an overpressure, are led to a turbine 5 of a turbocharger. The turbine 5 then provides a driving force, which is transmitted, via a connection, to a compressor 6. The compressor 6 compressed lu fi which, via an air filter 7, is led into an air line 8. A charge cooler 9 is arranged in the lu line 8.

The charge air cooler 9 is arranged at a front part of the vehicle 1. The function of the charge air cooler 9 is to cool the compressed air before it is led to the internal combustion engine 2. The compressed air is cooled in the charge air cooler 9 by air with ambient temperature flowing through the charge air cooler 9 10.

The cooling shaft 10 is driven by the combustion engine 2 by means of a suitable connection.

Internal combustion engine 2 equipped with an EGR (Exhaust Gas Recirculation) system for recirculation of the exhaust gases. By mixing exhaust gases into the compressed air that is led to the engine cylinders, the combustion temperature is lowered and thus also the content of nitrogen oxides NOX that are formed during the combustion processes. An exhaust line 11 for recirculating exhaust gases extends from the exhaust line 4 to the exhaust line 8. The return line 11 comprises an EGR valve 12, with which the exhaust gas in the return line 11 can be switched off. The EGR valve 12 can also be used to steplessly control the amount of exhaust gases led from the exhaust line 4, via the return line 11, to the lu line 8. The return line 11 comprises a first EGR cooler 14 and a second EGR cooler 15 for cooling the recirculating exhaust gases. in two steps. In the case of supercharged diesel engines 2, during certain operating conditions, the exhaust gas pressure in the exhaust line 4 is lower than the compressed air pressure in the inlet line 8. During such operating conditions it is not possible to directly mix the exhaust gases in the return line 11 with the compressed air in the inlet line 8 without special aids. In this case, for example, a venturi or a turbocharger with a variable geometry can be used.

If the combustion engine 2 is instead an overcharged otto engine, the exhaust gases in the return line 11 can be led directly into the inlet line 8 as the exhaust gases in the exhaust line 4 of an otto engine have a higher pressure than the compressed air in the inlet line 8. lu fi in the position Sa of the inlet line 8, the mixture is led to an evaporator 16 where the mixture is cooled in a final step before it, via a dry branch 17, is led to the respective cylinders of the diesel engine 2.

The internal combustion engine 2 is cooled in a conventional manner by means of a cooling system which comprises a circulating coolant. A coolant pump 18 circulates the coolant in the cooling system. The coolant pump 18 circulates a main flow of the coolant through the internal combustion engine 2. After the coolant has cooled the internal combustion engine 2, it is led in a line 21 to a thermostat 19 in the cooling system. When the coolant has reached a normal operating temperature, the thermostat 19 is adapted to direct the coolant to a cooler 20 for cooling. However, some of the coolant in the cooling system is led, via a line 22, to the first EGR cooler 14 where it cools the recirculating exhaust gases in a first step.

After the coolant has cooled the exhaust gases in the first EGR cooler 14, it is led back to the line 21 via a line 23. The hot coolant is cooled in the cooler 20 which is mounted on a different part of the vehicle 1. However, the cooler 20 is mounted downstream of the charge cooler 9 and the air-cooled second EGR cooler 15 with respect to the intended direction of scattering of the air. With such a location of the second EGR cooler 15 and the charge cooler 9, the recirculating exhaust gases and the compressed air can be cooled by lu fi at ambient temperature. With normally dimensioned such coolers 9, 15, the compressed air and the recirculating exhaust gases here provide a cooling to a temperature which exceeds the ambient temperature by about 10-155 ° C. The lower the temperature of the air and the exhaust gases, the greater the amount of air and recirculating exhaust gases can be led to the cylinders of the dry combustion engine.

The evaporator 16 forms a component of a cooling circuit with a circulating refrigerant.

The cooling circuit comprises a steam generator 24 which is arranged in the exhaust line 4 in a position downstream of the turbine 5. The refrigerant is heated in the steam generator 24 by the exhaust gases in the exhaust line 4 to a temperature so that it evaporates. The evaporated refrigerant is led to an ejector pump 25. Gaseous refrigerant from the steam generator 24 is mixed here with gaseous refrigerant from the evaporator 16. The gaseous refrigerant is led from the ejector 25 to a condenser 26. A fan 27 driven by an electric motor 28 forces a cooling air here. through the condenser 26 so that the refrigerant is cooled to a temperature at which it condenses. The cooling circuit includes a manifold located downstream of the condenser 26. The manifold includes a first conduit with a pump 29 which directs liquid refrigerant from the condenser 26 to the steam generator 24 and a second conduit with a check valve 30 which conducts liquid refrigerant 10 15 20 25 30 35 534 from the condenser 26 to the evaporator 16. A control unit 31 which is adapted to control the operation of said cooling circuit by means of information from, for example, a sensor 32 which senses the charge and the temperature of the recirculating exhaust gases in the inlet line 8.

During operation of the internal combustion engine 2, when the EGR valve 12 is open, hot exhaust gases are returned through the return line 11. The exhaust gases may have a temperature of 500 ° C-600 ° C when they reach the first EGR cooler 14. The exhaust gases are cooled in the first EGR the cooler 14 of the coolant in a first step. After the exhaust gases have been cooled in the first EGR cooler 14, they are passed on in the return line 11 to the second EGR cooler 15. The exhaust gases are cooled here in a second stage of air with ambient temperature to a temperature exceeding the ambient temperature by about 10-1 5 ° C. The compressed hatch is cooled in the charge hatch cooler 9 by air at ambient temperature. The compressed air can thus also be cooled to a temperature which exceeds the ambient temperature by 10-15 ° C. The cooled exhaust gases are mixed with the cooled air in position Sa in the inlet line 8.

The sensor 32 senses the temperature of the mixture of lu fi: and exhaust gases in the inlet line 8. Using e.g. from this information, the control unit 31 estimates whether it is possible to cool the mixture in a further step in the evaporator 16. Lu fi and in particular exhaust gases contain relatively abundant water vapor. As the air and exhaust gases are cooled, liquid water falls out inside the charge cooler 9 and the EGR cooler 15. Thus, liquid water will be led to the dry combustion engine 2. However, this is not a problem as long as it takes place under controlled conditions. However, the hatch and exhaust gases should not be cooled to a temperature lower than 0 ° C as the precipitated water in this case risks freezing to ice and stopping the flow in the inlet line 8. When the control unit 31 assesses that there is no risk of ice formation, the cooling circuit is activated. In this case, the control unit activates the pump 29 which pumps liquid refrigerant to the steam generator 24. The coolant provides a pressure p; in the steam generator 24. The hot exhaust gases in the exhaust line 4 heat the refrigerant so that it evaporates at the prevailing pressure pg. The gaseous refrigerant formed in the steam generator 24 is led to the ejector pump 25.

Fig. 2 shows the ejector pump 25 in more detail. When the gaseous refrigerant from the steam generator 24 reaches the ejector pump 25, it provides an acceleration in a tapered portion 25a. The gaseous refrigerant from the steam generator 24 thus obtains a very high velocity as it flows out of the draining portion 25a and into an interior space 25b. of the ejector pump 25. Thus, a very low static pressure po is provided in the space 25b. The ejector pump 25 comprises an inlet 250 adjacent the space 25b. The inlet 25c is connected to a line which carries refrigerant from the evaporator 16 to the ejector pump 25. The low static pressure po in the space 25b is lower than the pressure p1 prevailing in the evaporator 16. Thus gaseous refrigerant is sucked from the evaporator 16 to said space 25b in the ejector pump. 25. The gaseous refrigerant from the evaporator 16 is mixed here with the gaseous refrigerant from the steam generator 24. The ejector pump 25 finally comprises an expanding portion 25d with an increasing cross-sectional area where the gaseous refrigerant is slowed down. The gaseous refrigerant receives the pressure p; when it is led fi- from the ejector pump 25 to the condenser.261. The pressure p; is higher than the pressure p; but lower than the pressure po. The above-mentioned pressures po, p1, po, p; has been provided with sign names that are related to the mutual size of the new week.

The refrigerant is cooled in the condenser 26 by air which is forced through the condenser 26 by the gas 21. The refrigerant is cooled to a temperature such that the refrigerant conaososemf at the prevailing pressure p; inside the condenser 26. The cooling circuit thus comprises a branch in the form of two lines downstream of the condenser 26. One of the lines comprises the pump 29 which leads a part of the liquid refrigerant from the condenser 26 back to the steam generator 24. The pump 29 here supplies a pressure to the refrigerant so that the refrigerant pressure increases from po to po. The second conduit comprising the expansion valve 30 directs a remaining portion of the liquid refrigerant to the evaporator 16.

The expansion valve 30 lowers the refrigerant pressure from p; to po. The liquid refrigerant has at the pressure p; a lower temperature the air and the exhaust gases in the inlet line 8. The refrigerant thus absorbs heat from the air and the exhaust gases in the evaporator 16. The refrigerant has an evaporation temperature, at the pressure pi, which is advantageously lower than the ambient temperature. Thus, the mixture of lu fi and exhaust gases can be cooled to a temperature equal to or lower than the ambient temperature in the evaporator 16. The refrigerant evaporated in the evaporator 16 is sucked to the ejector pump 25 where it is thus mixed with the refrigerant from the steam generator 24.

Thus, in this case, a cooling circuit is used to cool the compressed air and the recirculating exhaust gases in a final step before they are led into the internal combustion engine 2. 534 a? 2_ is used to evaporate the refrigerant at the highest pressure on the cooling circuit. The evaporated refrigerant, which thus has a relatively high pressure pg, is used to create a fate at a high velocity through the ejector pump 25. Thus, a very low static pressure po can be created inside the ejector purge 25 which results in the refrigerant from the evaporator 16 with the pressure p ; can be sucked into the ejector pump 25 and mixed with the refrigerant n from the steam generator 24. In addition to said heat energy, only energy needs to be supplied for operation of the pump 29. The energy required to drive the pump 29 is substantially negligible. In this case, existing heat energy is thus used to drive the cooling circuit. At times when the control unit 31 receives information from the sensor 32 indicating that the air and the exhaust gases risk being cooled to a temperature below 0 ° C, the operation of the pump 29 and thus the operation of the cooling circuit is deactivated. Thus, in this case, the dry evaporator 16 is not used to cool the air and the exhaust gases before they are led to the combustion engine 2.

An alternative steam generator 35 is marked with dashed lines in Fig. I. When such a steam generator 35 is used, the coolant in the cooling system which cools the combustion engine 2 is used as a heat source. The coolant may have a temperature of about 100 ° C when it leaves the combustion engine 2. In this case, an additional cooling of the coolant is thus provided which reduces the load on the ordinary cooler 20.

Fig. 3 shows an alternative cooling circuit for cooling the air and the exhaust gases which are led to the dry combustion engine 2. In this case a steam generator 33 which absorbs heat from the compressed air is used in a position upstream of the charge air cooler and a steam generator 34 which absorbs heat energy from the recirculating exhaust gas. a position upstream of the EGR cooler 9. Since both the compressed air and in particular the recirculating exhaust gases can have a very high temperature, the refrigerant can be heated fi effectively to the temperature at which it is evaporated in such steam generators 33, 34. The absorbed heat energy is also used here for to operate a corresponding cooling circuit as described in the outlet form in Fig. 1. We therefore do not make any further review of the fi irrlction cooling circuit here. The two steam generators 33, 34 are arranged in parallel here. As heat energy is taken up from the compressed air and the recirculating exhaust gases, they provide a cooling in a first stage in the two steam generators 33, 34. There, the compressed air in the charge air cooler 9 and the recirculating exhaust gases in the EGR cooler 15 are cooled. . The mixture is cooled in a final step in the evaporator 16. When the two steam generators 33, 34 provide an initial cooling 534 B72 10, the cooling of the compressed air and the recirculating exhaust gases is further streamlined.

The invention is in no way limited to the embodiments described in the drawings, but can be varied slightly within the scope of the claims. It is possible, for example, to cool only the recirculating exhaust gases or the compressed air in the manner mentioned above. That is, the evaporator 16. is arranged in a conduit which only conducts recirculating exhaust gases or compressed air.

Claims (6)

10 15 20 25 30 534 B72 1 '\ Patent claim An arrangement for cooling at least one medium which is led to an internal combustion engine (2), the arrangement comprising a line (8, 11) which is adapted to lead the medium to the internal combustion engine (2) and a first cooler (9, 15) for cooling the medium in an initial step in the line (8, l 1) by means of lu fi or a circulating coolant, a cooling circuit with a circulating refrigerant which is adapted to change phase during dri fi, fuels (24, 25, 33, 34) which are adapted to provide operation of the cooling circuit mainly by means of heat energy from a heat source, an evaporator (16) arranged in the line (8, 11) in a position downstream of the above-mentioned first cooler (9, 15) with respect to the direction of fate of the medium led in the line (8, 1 1) so that the medium is cooled in a final step in the evaporator (16) before it is led to the internal combustion engine (2), said propellant comprising a steam generator (24, 33, 34) where the refrigerant is adapted to be heated by said evaporator. heat source to a temperature at which steam and an ejector means (25) adapted to mix gaseous refrigerant from the evaporator (16) with gaseous refrigerant from the steam generator (24, 33, 34) and the cooling circuit comprising a condenser (26) where the refrigerant from the ejector means (25) is adapted to be cooled to a temperature at which it condenses, characterized in that the arrangement comprises a control unit (31) adapted to control the operation of the cooling circuit so that the medium is cooled in the final step of the evaporator (16) to a temperature corresponding to or below the ambient temperature as long as the medium does not risk cooling to a temperature below 0 ° C. Arrangement according to claim 1, characterized in that the cooling circuit comprises a branch arranged downstream of the condenser (26), which comprises a first line with a pump (29) which conducts liquid refrigerant from the condenser (26) to the steam generator (24, 33, 34) and a second conduit with an expansion valve (30) which conveys liquid refrigerant from the condenser (26) to the evaporator (16). Arrangement according to claim 1 or 2, characterized in that said medium is compressed lu / and / or recirculating exhaust gases and that they are adapted to be cooled directly or indirectly by air with ambient temperature in said first cooler (9, 15). 10 15 534 8? 2 12 Arrangement according to any one of the preceding claims, characterized in that said steam generator (24) is arranged in a position so that it absorbs heat from the exhaust gases in an exhaust line (4) of the internal combustion engine. Arrangement according to any one of the preceding claims 1-3, characterized in that said steam generator (33, 34) is arranged in a position so that it absorbs heat from the medium in said line (8, 11) in a position upstream of the cooler ( 9, 15). Arrangement according to any one of the preceding claims 1-3, characterized in that said steam generator (35) is arranged in a position so that it absorbs heat from coolant circulating in a cooling system which cools the combustion engine (2).