SE533123C2 - Arrangement for cooling of recirculating exhaust gases of an internal combustion engine - Google Patents

Description

533 123 the cooling system thus high load peaks at times when the internal combustion engine is heavily loaded. In heavy vehicles, the internal combustion engine cooling system is generally also used for other cooling needs in the vehicle, such as, for example, cooling of the oil in a hydraulic retarder. It is therefore desirable to reduce the load on the internal combustion engine cooling system.

SUMMARY OF THE INVENTION The object of the present invention is to provide an arrangement for cooling recirculating exhaust gases where the recirculating exhaust gases can be cooled in a first step in a relatively simple but functional first EGR cooler.

This seam 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.

The exhaust gases discharged from an internal combustion engine in an exhaust line show kinetic energy and pressure energy. According to the invention, an ejector pump device is applied in a suitable part of the exhaust line. With the aid of such an ejector pump device, a suction cup fi can be created, as the exhaust gases flow through the ejector pump device, which sucks air into the exhaust line from the air line and the first EGR cooler. With such a cooling air stream, the first EGR cooler can provide a good cooling of the exhaust gases. The load on the second EGR cooler, which cools the exhaust gases in a second stage, is thus significantly reduced. The first EGR cooler thus does not need to be equipped with an energy-intensive fan or similar component in order for a cooling air stream to be obtained through the EGR cooler. The first EGR cooler can thus be given a relatively simple construction.

According to a preferred embodiment of the present invention, the ejector pump device comprises a converging nozzle with an outlet opening having a smaller cross-sectional area than the cross-sectional area of the exhaust line upstream of the nozzle and the air line having an outlet opening in the exhaust line located radially. With such a converging nozzle, the exhaust gases obtain a tapered flow passage which results in a correspondingly increased speed. The exhaust gases are led out of the nozzle outlet opening at a high speed. This creates a low pressure in an area around the nozzle opening. Since the overhead line has an outlet opening adjacent to this low pressure zone, air is sucked in a copious amount into the exhaust line 5133 '123 from the overhead line. When air is sucked into the exhaust line from the air line, a corresponding air flow is obtained through the first EGR cooler, which cools the exhaust gases in the EGR cooler. The non-pump pump device advantageously comprises a converging portion with a decreasing cross-sectional area which is located downstream of the outlet opening of the nozzle with respect to the intended flow direction of the exhaust gases in the exhaust line. Thus, the air sucked into the exhaust pipe can obtain an increased speed downstream of the nozzle, which further increases the ejector pump device's ability to suck air into the exhaust pipe and thus the air flow that flows through the first EGR cooler.

According to a preferred embodiment of the present invention, the first EGR cooler comprises a plurality of parallel exhaust ducts leading the recirculating exhaust gases through the EGR cooler and a plurality of parallel air ducts guiding air through the EGR cooler. The ducts can be formed by pipelines which have external surfaces, which are advantageously flat, so that optimal contact surfaces can be formed between the pipelines which conduct the exhaust gases and the pipelines which conduct the air. The exhaust gases can be led in the exhaust ducts in the EGR cooler in a first direction and the air can be led in the EGR cooler in the air ducts in a second direction that is perpendicular to the first direction. The EGR cooler can also be designed so that air and exhaust gases are led in opposite directions through the EGR cooler or in the same direction. The exhaust duct and / or air duct of the first EGR cooler may comprise heat-conducting elements which increase the heat-absorbing surface inside the respective ducts. Such thermally conductive elements can consist of pleated metal plates, so-called vines, which divide the channel into a number of parallel flow passages. Thereby a larger contact surface is obtained between the exhaust gases and the pipeline which forms the exhaust duct and / or between the air and the pipeline which forms the air duct. The presence of such thermally conductive elements results in a more efficient heat exchange between the air and the exhaust gases in the first EGR cooler.

According to an embodiment of the present invention, the EGR cooler comprises an inlet opening which is adapted to suck air into the EGR cooler from an area which is located in direct connection with the EGR cooler. The exhaust line for recirculation of exhaust gases normally has a main route in connection with the internal combustion engine.

The first EGR cooler therefore normally also receives a location close to the internal combustion engine. In this case, lu fi is sucked into the EGR cooler from an area in the engine compartment adjacent to the internal combustion engine. The air here normally has a clearly higher temperature than ambient air, but this temperature is clearly lower than the temperature of the L-J DJ .J FU CC 'exhaust gases. This air can therefore be used to cool the exhaust gases with a good result in a first step in the first EGR cooler. According to an alternative embodiment, the EGR cooler comprises an air duct which has a distance between the first EGR cooler and an air inlet which is adapted to suck in air from an area which is located at a distance from the EGR cooler. Such an overhead line can be drawn to an area where there is good access to cold air. In this case, air with a significantly lower temperature can be used to cool the exhaust gases in the first stage, which further improves the cooling of the exhaust gases in the first EGR cooler.

According to another embodiment of the invention, the recirculating exhaust gases are adapted to be cooled in the second EGR cooler in a second stage of coolant from the cooling system of the internal combustion engine. The cooling system that cools the internal combustion engine is an already existing cooling system which is advantageously also used to cool the recirculating exhaust gases. The coolant in the cooling system of the internal combustion engine has a temperature of 80-100 ° C during normal operation. It is thus possible to use the coolant in the cooling system of the dry combustion engine to cool the recirculating exhaust gases to a corresponding temperature. Since the recirculating exhaust gases have already been cooled in a first stage in the first EGR cooler, a relatively moderate load on the cooling system of the internal combustion engine is obtained in this case. As the primary task of this cooling system is to cool the internal combustion engine, it should not be overburdened with other cooling tasks as the cooling of the internal combustion engine can be replaced in such circumstances.

According to another preferred embodiment of the invention, the arrangement comprises a third EGR cooler where the recirculating exhaust gases are adapted to be cooled in a third stage of a medium which during normal operation of the internal combustion engine has a lower temperature than the coolant in the cooling system of the internal combustion engine. Since the coolant in the dry combustion engine cooling system has an operating temperature of 80-100 ° C, the exhaust gases can only be cooled to a temperature close to the coolant temperature in the other EGR cooler. It is often desirable to cool the exhaust gases to a lower temperature. The recirculating exhaust gases can then be cooled in a third EGR cooler by, for example, coolant in a low-temperature cooling system where the coolant has a lower temperature than the coolant in the cooling system of the internal combustion engine. Such a low temperature cooling system may comprise a cooling element where the coolant in the cooling system is cooled by air of ambient temperature. Thus, the coolant in the low temperature cooling system can obtain a temperature close to the ambient temperature. The exhaust gases can thus be cooled to a relatively low temperature before they are mixed with air and led to the internal combustion engine. Alternatively, the exhaust gases can be cooled in a third stage in a third EGR cooler which is air cooled. In this case, the recirculating exhaust gases are cooled with the advantage of lu fi with the ambient temperature.

According to another preferred embodiment of the invention, the exhaust line comprises a turbine and that the return line receives exhaust gases from the exhaust line in a position upstream of the turbine with respect to the flow direction of the exhaust gases in the exhaust line.

Such a turbine may be included in a turbocharger which also includes a compressor which granules air which is led to the internal combustion engine. To facilitate the mixing of the recirculating exhaust gases into the compressed air, it is advisable to recirculate exhaust gases from the exhaust line before they expand in the turbine.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, preferred 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 recirculating exhaust gases of a diesel engine according to a first embodiment of the invention, Fig. 2 shows the ejector pump device in Fig. 1 in more detail, Fig. 3 shows the first EGR cooler in Fig. 1 in more detail and Fig. 4 shows an arrangement for cooling recirculating exhaust gases of a diesel engine according to a second embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 shows an internal combustion engine adapted to drive a schematically shown vehicle 1. The internal combustion engine is exemplified here as a diesel engine 2.

The diesel engine 2 can be intended as a drive engine for a heavier vehicle 1. The exhaust gases from the cylinders of the diesel engine 2 are led, via an exhaust 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 thus provides a driving force which is transmitted, via a liner connection, to a compressor 6 of the turbocharger. The compressor 6 sucks in and compresses air which, via an air filter 7, is led into an inlet line 8. A charge air cooler 9 is arranged in the inlet line 8. The charge air cooler 9 is stated to cool the compressed air before it is led to the diesel engine 2. The compressed 533 ' The air is cooled in the charge cooler 9 by ambient air which is forced through the charge cooler 9 by means of a cooling fan 10. The cooler 10 is driven by the diesel engine 2 by means of a suitable connection.

A return line 11 for recirculating a part of the exhaust gases in the exhaust line 4 has a distance between the exhaust line 4 and the inlet line 8 for the air which is led to the diesel engine 2. The return line 11 is connected to the exhaust line 4 in a position 4a upstream of the turbine 5. The exhaust gases have a high pressure and a high temperature.

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 fed to the diesel engine 2. A control unit 13 is adapted to control the EGR valve 12 with information about the current operating condition of the diesel engine 2.

The control unit 13 may be a computer unit provided with a suitable software.

The recirculating exhaust gases in the return line 11 are mixed with the compressed air in the inlet line 8 by means of a mixing device 14. In 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. 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 turbocharger with a variable geometry can be used. If the internal combustion engine 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.

An arrangement for cooling the recirculating exhaust gases comprises a first EGR cooler 15 where the recirculating exhaust gases are cooled in a first stage in the return line 11.

The first EGR cooler 15 is air cooled. To obtain a luminous flux through the first EGR cooler 15, an ejector pump device 16 is used which is applied in the exhaust line 4 in a position downstream of the turbine 5 and downstream of a muffler 17.

The muffler 17 may also comprise a catalyst and a particle filter for purifying the exhaust gases. An overhead line 18 connects the first EGR cooler 15 to the ejector pump device 16. In this case, air is sucked into the iEGR cooler 15 from an area 22 in the engine compartment which is located in the vicinity of the diesel engine 2. 533 'I-Éíši The diesel engine 2 is cooled in a conventional method of a cooling system 23 with a circulating coolant. A coolant pump 24 circulates the coolant in the cooling system 23. After the coolant has circulated through the diesel engine 2, it is led in a line 25 to a thermostat 26. In cases where the coolant has reached a normal operating temperature, the thermostat 26 is adapted to direct the coolant to a cooler element 27, which is mounted in the area A in the vehicle in a position behind the charge cooler 9. A part of the coolant in the line 25 is led into a line circuit 28 at a position 25a of the line 25. The coolant in the line circuit 28 is led through a second EGR cooler 29 where the coolant cools the recirculating the exhaust gases in the return line 11 in a second step. The coolant is then returned to the line 25 in a position 25b which is located downstream of the position 25a with respect to the intended direction of destiny of the coolant in the line 25.

The recirculating exhaust gases are passed on in the return line 11 to a third EGR cooler where they are cooled in a third stage by the coolant in a low temperature cooling system 31.

The low temperature cooling system 31 comprises a circulating coolant which during normal operation of the diesel engine 2 has a lower temperature than the coolant in the diesel engine cooling system 23. A coolant pump 32 circulates the coolant in the low temperature cooling system 31. The low temperature cooling system 31 comprises a radiator element 33 position in front of the radiator 27. After cooling in the three EGR coolers 15, 29, 30, the recirculating exhaust gases are led to the mixing device 14 where they are mixed with the compressed air in the inlet line 8. There the mixture of air and exhaust gases, via a branch 34, is led to diesel engine 2 and cylinders respectively.

Fig. 2 shows the ejector pump device 16 in more detail. Upstream and downstream of the ejector pump device 16, the exhaust line 4 has an internal substantially constant cross-sectional area A1. The ejector pump device 16 comprises a nozzle 16a which forms a successively decreasing cross-sectional area of the exhaust gases as they flow through the ejector pump device 16. The nozzle 16a has an outlet opening 16a 'for the exhaust gases having a cross-sectional area A; which is considerably smaller than the exhaust line cross-sectional area A1 upstream of the ejector pump device 16. The Lu line 18 is connected to the non-ejector pump device 16 via an outlet opening 18a which is located in a position radially outside the nozzle outlet opening 16a of the nozzle. Outlet opening 18a opens into a low pressure zone area 16b of the ejector pump device 16.

The ejector pump device 16 comprises, in a position downstream of the nozzle 16a, a converging portion 16c with a cross-sectional area A3 which decreases in the direction of flow of the exhaust gases. Finally, the ejector pump device 16 comprises a diverging portion 16d with an increasing cross-sectional area A4i in the flow direction of the exhaust gases. Downstream of the diverging portion 16d, the exhaust line 4 regains its original internal cross-sectional area A1.

Fig. 3 shows the first EGR cooler 15 in more detail. When the recirculating exhaust gases reach the first EGR cooler 15, the return line 11 is split into a number of exhaust ducts 19 arranged in parallel which extend through the first EGR cooler 15. In this case the EGR cooler 15 comprises nine such exhaust ducts 19 which are arranged in three plane with three exhaust ducts 19 in each plane. The exhaust ducts 19 are formed by pipelines that have a rectangular: cross section. The EGR cooler 15 comprises air ducts extending between the plane of exhaust ducts 19. The air ducts 20 are also formed by pipelines with a rectangular cross-section. The pipelines forming the exhaust ducts 19 abut with flat relatively large contact surfaces against the pipelines forming the air ducts 20. Thus a good heat transfer is obtained in the EGR cooler between the exhaust gases in the exhaust ducts 19 and the air in the air ducts 20. The air is sucked into the ducts 20, via inlets, openings 20 after which it is passed through the EGR cooler 15 in a direction which is perpendicular to the flow direction of the exhaust gases in the exhaust ducts 19.

The air that has passed through the EGR cooler 15 is collected in a collecting portion 18b before it is led into the air line 18 which leads the air to the ejector pump device 16.

The air ducts 20 contain pleated metal plates 21 which divide the air ducts 20 into a large number of parallel fate passages. The metal plates can be made of aluminum.

The metal plates 21 supply an extra contact surface in the air ducts 20, which increases the heat exchange between the air in the air ducts 20 and the exhaust gases in the exhaust ducts 20. The metal plates 21 can also have a shape which promotes a turbulent flow of the air in the air ducts 20.

Such a flow further increases the heat exchange between the air and the exhaust gases in the first EGR cooler 15.

During operation of the diesel engine 2, exhaust gases flow out of the diesel engine 2 and into the exhaust line 4. During most of the operating conditions of the diesel engine 2, the control unit 13 keeps the EGR valve 12 open so that some of the exhaust gases in the exhaust line 4 are led into the return line 11. which is led into the return line 11 usually has a temperature in the range 150 ° C - 600 ° C depending on the operating state of the diesel engine.

The exhaust gases in the exhaust line 4 reaching the ejector pump device 16 provide an increased velocity as they flow through the nozzle 16a which thus forms a flow passage with a decreasing cross-sectional area. The exhaust gases thus eject 123 through the nozzle opening 16a 'at a high speed. Thereby a low static pressure is obtained in the low pressure area 16b which is located around the exhaust stream. The low pressure in the low pressure zone 16b results in air being sucked into the low pressure area 16b from the air line 18 having an outlet port 18a in a position radially outside the nozzle outlet 16a '. The air sucked into the low pressure area 16b is carried by the exhaust stream into the converging portion 16c of the ejector pump device 16. In the converging portion 16c the air obtains a velocity increase. thus also the ability to suck lu fi through the EGR cooler 15. The velocity of the exhaust gases and air then decreases in the diverging portion l6d of the non-eector pump device 16. The mixture of exhaust gases and air then leaves the ejector pump device 16 and is led back into the ordinary exhaust line 4 which has cross-sectional area A1 . The recirculating exhaust gases in the return line 11 are thus cooled in a first stage in the first EGR cooler 15 by air sucked in from the engine compartment 22 by means of the ejector pump device 16 in the exhaust line 4. The recirculating exhaust gases can, for example, be cooled to a temperature in the range 150 ° C - 200 ° C when leaving the first EGR cooler 15.

The recirculating exhaust gases are then led to the second EGR cooler 20 where they are cooled by coolant from the cooling system 23 of the diesel engine. The coolant here normally has a temperature in the temperature range 80 ° C-100 ° C. Thus, the recirculating exhaust gases can be cooled to a temperature of about 100 ° C - 120 ° C in the second EGR cooler 23.

The recirculating exhaust gases are finally led to the third EGR cooler 30 where they are cooled in the third stage by coolant from the low temperature cooling system 31. The cooling element 33 in the low temperature cooling system 31 is cooled by ambient temperature forced through the cooling element 33 by means of cooler fl. in the low temperature cooling system have a temperature close to the ambient temperature when it is introduced into the third EGR cooler 30. The recirculating exhaust gases can thus be cooled to a relatively low temperature in the third stage of the third EGR cooler 30 before being mixed with the compressed the air, which is advantageously cooled to a corresponding temperature in the charge air cooler 9, before the mixture of exhaust gases and air is led to the diesel engine 2.

During the shit cases when the diesel engine 2 is heavily loaded, it requires a good cooling.

The exhaust gases also have a high temperature during these operating events. The initial cooling of the recirculating exhaust gases by means of the first EGR cooler 533 '23 significantly reduces the temperature of the exhaust gases before they are led to the second EGR cooler 29 where they are cooled in a second stage by the coolant in the cooling system 23 of the diesel engine. such a first EGR cooler 15, the load on the cooling system 23 of the diesel engine can be considerably reduced.

Fig. 4 shows an alternative embodiment of the arrangement for cooling the recirculating exhaust gases. In this case, an air duct 35 is used to lead liquor to the first EGR cooler 15. The air duct 35 includes an inlet opening 35a located in an area 22a located at a distance from the first EGR cooler 15 where there is good access to cold luñ. In this case, air is thus sucked from the area 22a, via the lu line 35 to the first EGR cooler 15 where it cools the recirculating exhaust gases. The lu fi is then led via the lu line 18 to the ejector pump device 16 and out into the exhaust line 4. By taking air from an area 22a containing relatively cold lu fi, the exhaust gases can provide a further improved cooling in the first EGR cooler. In this embodiment, a third EGR cooler 36 is used which is closed. The third EGR cooler 36 is located in area A next to the charge cooler 9 and in front of the cooler element 27. The third EGR cooler 36 is thus flowed through by air at ambient temperature. The recirculating exhaust gases can thus be cooled in the third EGR cooler 33 in a third step to a temperature close to the ambient temperature before they are mixed with the compressed air and led to the diesel engine 2. Otherwise, the embodiment in Figs. 4 shows the embodiment of FIG. 1.

The invention is in no way limited to the embodiments described above, but can be varied freely within the scope of the claims. Thus, it is not necessary to cool the recirculating exhaust gases in three steps, but they can be cooled in two steps where the cooling of the recirculating exhaust gases in the first EGR cooler 15 constitutes a first step.

Claims (8)

10 15 20 25 30 35 533 'H33 Patent claim An arrangement for cooling recirculating exhaust gases of an internal combustion engine (2), the internal combustion engine comprising an exhaust line (4) intended to discharge exhaust gases from the internal combustion engine (2) and a return line (1 1) adapted to recirculate a part of the exhaust gases in the exhaust line (4) to the internal combustion engine (2), and wherein the arrangement comprises a first EGR cooler (1S) in which the exhaust gases in the return line (11) are adapted to be cooled in a first stage, a second EGR cooler (29) in which the exhaust gases in the return line (1 l) are adapted to be cooled in a second stage of coolant from the internal combustion engine cooling system (23) and a third EGR cooler (33, 36) in which the exhaust gases in the return line (1 1) are adapted to be cooled in a third stage of a medium which during normal operation of the internal combustion engine has a lower temperature than the coolant in the cooling system (23) of the internal combustion engine, characterized in that the arrangement comprises an ejector pump device (16) arranged in the exhaust line ( 4) and an air line (18) extending between the first EGR cooler (15) and the ejector pump device (16), the ejector pump device (16) being adapted to suck lu fi through the first EGR cooler (15) and the lu fi line (18) to the exhaust line (4) by means of the exhaust gases flowing through the ejector pump device (16), Arrangement according to claim 1, characterized in that the ejector pump device (16) comprises a converging nozzle (16a) with an outlet opening (16a ") having a smaller cross-sectional area (A2) than the cross-sectional area (A1) in the exhaust line (4) upstream of the nozzle (16a). ) and that the lu line (18) has an outlet opening (18a) in the exhaust line (4) which is located in a position radially outside the nozzle outlet opening (16a ') of the nozzle. Arrangement according to claim 2, characterized in that the ejector pump device (16) comprises a converging portion (16c) with a decreasing cross-sectional area (A3) located downstream of the outlet opening (16a °) of the nozzle with respect to the intended direction of flow (4) of the exhaust gases in the exhaust gas. . Arrangement according to claim 1, characterized in that the first EGR cooler (15) comprises a number of parallel exhaust ducts (19) which direct the recirculating exhaust gases through the EGR cooler (15) and a number of parallel air ducts (20) which conduct air through EGR cooler (15). 10 15 20 Arrangement according to claim 4, characterized in that the exhaust duct (19) and / or the lu duct (20) of the first EGR cooler (15) comprises heat-conducting elements (21) which increase the heat-absorbing surface inside the respective ducts (19, 20). . Arrangement according to claim 5, characterized in that the first EGR cooler (15) comprises an inlet opening (20a) which is adapted to suck lu fl into the EGR cooler (15) from an area (22) located in direct connection to the EGR cooler (15). Arrangement according to one of the preceding claims, characterized in that the first EGR cooler (15) comprises a heat pipe (35) which has a distance between the first EGR cooler (15) and a heat inlet (3 Sa) which is adapted to suck in air from an area (22a) located at a distance from the EGR cooler (15). Arrangement according to one of the preceding claims, characterized in that the exhaust line (4) comprises a turbine (5) and in that the return line (11) receives exhaust gases from the exhaust line (4) in a position upstream of the turbine (5) with respect to the flow direction of the exhaust gas in the exhaust line. (4).