SE530582C2 - Arrangement and method of a supercharged internal combustion engine - Google Patents

Description

530 582 tion disorders. In addition, incomplete evaporation of the urea solution leads to a reduced ability to reduce nitrogen oxides in the exhaust gases.

Exhaust lines of diesel engines, in addition to a catalyst, normally also comprise a particulate filter which is intended to filter out soot particles in the exhaust gases. To clean the filter from soot particles, fuel can be injected into the exhaust line in connection with the particle filter. The injection of fuel into the exhaust line increases the exhaust temperature to a level so that soot particles stuck in the particle filter are burned. In order to be able to carry out such a cleaning process of the particle filter, it is required that the existing exhaust gases in the exhaust line have a temperature so that they can evaporate the fuel that is injected into the exhaust line.

SUMMARY OF THE INVENTION The object of the present invention is to provide an arrangement and a method of a supercharged internal combustion engine, in which a supplied medium can substantially always be vaporized by the exhaust gases in an exhaust line regardless of the operating condition of the internal combustion engine.

This object is achieved with arrangements of the kind mentioned in the introduction, which is characterized by the features stated in the characterizing part of claim 1. When a turbine is used to absorb energy from exhaust gases in an exhaust line, the exhaust gases in the part of the exhaust line which is located downstream of the turbine obtain a considerably lower pressure than the exhaust gases which are located upstream of the turbine. The same applies to the temperature of the exhaust gases. In this case, exhaust gases from the part of the exhaust line located upstream of the turbine are thus used to heat the medium. The exhaust gases here have a relatively high temperature even during times when the internal combustion engine is under low load. With the help of these hot exhaust gases, it is essentially always possible to heat the medium to a temperature so that it can be guaranteed to evaporate before or in connection with it being injected into the part of the exhaust line which is located after the turbine.

According to a preferred embodiment of the invention, the heat exchanger is adapted to flow through the exhaust gases from the first part of the exhaust line so that the medium provides a heating in the heat exchanger to a temperature which exceeds the evaporation temperature of the medium at the pressure prevailing in the second part of the exhaust line. Thus, the medium can be evaporated before or in connection with the injection of the second part of the exhaust line without any additional heat energy having to be supplied from the exhaust gases in the second part of the exhaust line. The arrangement advantageously comprises pressure-supplying means which are adapted to give the medium a higher pressure in the heat exchanger than the pressure prevailing in the second part of the exhaust line. Such a pressure-increasing means may be a pump which is transported the medium with a suitable overpressure through the heat exchanger. The media can do that. be adapted to be heated in the heat exchanger to a temperature lower than the evaporation temperature of the medium in the heat exchanger. Since the medium has a higher pressure in the heat exchanger than the pressure prevailing in the second part of the exhaust line, it is possible to heat the medium in the liquid form in the heat exchanger to a higher temperature than the evaporation temperature of the medium in the second part of the exhaust line. An advantage of this is that the medium can be transported in the liquid form from the heat exchanger to the injection means. As soon as the medium is injected into the exhaust line, where there is thus a lower pressure than in the heat exchanger, it will evaporate. Alternatively, the medium can be heated in the heat exchanger to a temperature so that it evaporates in the heat exchanger. The medium can then be transported in gaseous form to the injection means and injected into the second part of the exhaust line.

According to another preferred form of drying of the invention, said injecting means is arranged in a position so that the medium is injected into or upstream of an exhaust gas cleaning component in the second part of the exhaust line. Media mixed with the exhaust gases in an exhaust line are usually supplied for the purpose of enabling a purification of the exhaust gases or to enable a cleaning of an exhaust gas purifying component. Such a medium may be a urea solution and the exhaust gas purifying component being a catalyst. Thus, the nitrogen oxides in the exhaust gases can be converted to nitrogen gas and water. It is also conceivable to use other types of reducing agent than a urea solution to purify the exhaust gases in a subsequent catalyst. According to a further alternative, said medium may be a fuel and that the exhaust gas purifying component is a particulate filter. Fuel in the form of, for example, diesel oil can be injected into an exhaust line with the aim of raising the temperature of the exhaust gases flowing through the particle filter. The exhaust gases in this case obtain such a high temperature that they burn soot particles stuck in the particle filter.

According to another preferred embodiment of the invention, the arrangement comprises a conduit adapted to guide the medium from said source of radiation to the injection means, and a control unit adapted to control the flow of the medium through said conduit and the amount of medium being sprayed. into the second part of the exhaust line. Such a control unit may comprise a computer which is provided with a software adapted 530 582 to control the medium and the injection means so that an optimum amount of the medium is injected into the second part of the exhaust line.

According to another preferred embodiment of the invention, the heat exchanger is adapted to flow through exhaust gases which are led in a line which has a distance from the first part of the exhaust line to an inlet line for air to the internal combustion engine. In this case, the recirculating exhaust gases in a hazardous EGR system are used as a heat source. In such an EGR system, the recirculating exhaust gases provide cooling in at least one EGR cooler before being mixed with the air in an inlet line to the internal combustion engine. By utilizing the heat of the recirculating exhaust gases in the existing EGR system, a good heat source for the medium can be provided in a relatively simple way and with a relatively small number of additional components. In addition, the extra cooling that the exhaust gases provide in the heat exchanger can be seen as a complement to the regular cooling of the recirculating exhaust gases. Alternatively, the heat exchanger may be adapted to be traversed by exhaust gases which are led in a line which extends from the first part of the exhaust line to the second part of the exhaust line. In this case, a separate line is used to lead exhaust gases from the thirst part of the exhaust line to the heat exchanger. Such a line may include a valve means for controlling the flow of exhaust gases through the line and the heat exchanger. Since there is a pressure difference between the first part of the exhaust line and its second part, such a valve means only needs to be placed in an open position for an exhaust flow to be obtained through the line and the heat exchanger.

The above object is also achieved with the method of the kind mentioned in the introduction, which is characterized by the features stated in the characterizing part of claim II.

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 according to a first embodiment of the invention and Fig. 2 shows an arrangement according to a second embodiment of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION FIG. 1 shows an overcharged internal combustion engine in the form of a diesel engine 1. The diesel engine 1 can be intended as a drive engine for a heavier vehicle. The exhaust gases from the cylinders of the diesel engine 1 are led, via an exhaust collector 2, to an exhaust line 3. The exhaust line comprises a first part 3a which extends to a turbine 4 of a turbocharger.

The exhaust gases have a relatively high pressure and a high temperature in the first part 3a.

The turbine 4 is intended to convert the energy of the exhaust gases in the exhaust line 3 into mechanical work to drive a compressor 5 of the turbocharger. The exhaust line comprises a second part 3b which is located after the turbine 4. The temperature and pressure of the exhaust gases in the second part 3b are considerably lower than in the first part 3a. The compressor 5 is intended to compress air which, via an air filter 6, is sucked into an inlet line 7 to the diesel engine 1. A charge air cooler 8 is arranged in the inlet line 7 to cool the compressed air before it, via a branch 9, is led to the diesel engine 1. respective cylinders.

The combustion engine 1 is in this case equipped with an EGR (Exhaust Gas Recirculation) system for recirculation of the exhaust gases. By mixing exhaust gases in the compressed air that is led to the engine cylinders, the combustion temperature is lowered and thus also the content of nitrogen oxides (N OX) in the exhaust gases. A return line 10 for recirculating exhaust gases extends from the first part 3a of the exhaust line to the inlet line 7. The return line 10 comprises, in a first position 10 °, a division into two parallel line portions 10a, b. The first line portion 10a comprises a first EGR valve 11a and an EGR cooler 12. The second line portion 10b comprises a second EGR valve 11b and a heat exchanger 13. The flow of recirculating exhaust gases through the individual line portions 10a, b can be regulated by means of the respective EGR valves. 1 la, b. Advantageously, the EGR valves 11a, b can steplessly regulate the amount of exhaust gases passed through the respective conduit portions 10a, b. The exhaust gas flow in the return conduit 10 can also be completely shut off by means of the EGR valves 11a, b. , b merges in a second position 10 ”. From the second position 10 "the exhaust gases in the return line 10 are led to the inlet line 7. In supercharged diesel engines 1, under certain operating conditions, the exhaust gas pressure in the exhaust line 4 is lower than the compressed air pressure in the inlet line 8. Under 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 7 without special aids. In this case, for example, a venturi v14 or a turbocharger with a variable geometry can be used to ensure that the exhaust gases are led 530 582 into the inlet line 7. If the internal 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 7. in the exhaust line of an otto engine substantially under all operating conditions has a higher pressure than the compressed air in the inlet line 8. After the exhaust gases have been mixed with the compressed air in the inlet line 7, the mixture is led, via the branch 9, to the internal combustion engine 1 and cylinders.

The diesel engine 1 is also equipped with a catalytic exhaust gas purification according to the method called SCR (Selective Catalytic Reduction). This method means that a medium in the form of a urea solution is supplied to the exhaust gases in the diesel engine's exhaust line 3. The urea solution is stored in a tank 15. A line 16 extends between the tank 15 and the exhaust line 3. A control unit 17 is adapted to control the activation of a pump 18 which transports and pressurizes the urea solution in the line 16. The line 16 comprises the heat exchanger 13 and an injection means 19 which is adapted to inject the urea solution into the exhaust line 3 in an amount as calculated by the control unit. The injector 19 is mounted in the second part 3b of the exhaust line. The supplied urea solution is intended to evaporate and be converted to ammonia in the exhaust line 3 before it is passed through a catalyst 21. A particle filter 20 may be arranged in a common container such as the catalyst 21. Such a container can also serve as a muffler. In the catalyst 21, the nitrogen oxides in the exhaust gases are reduced to nitrogen gas and water vapor, which is discharged to ambient air. The injector 19 may alternatively be located between the particle filter 20 and the catalyst 21.

During operation of the diesel engine 1, the Control Unit 17 receives substantially continuous information regarding relevant engine parameters. With this information, the control unit 17 calculates the amount of the urea solution that needs to be added in order for the content of nitrogen oxides in the exhaust gases to be reduced in an optimal way. The control unit 17 activates the pump 18 which pressurizes and transports ureal solution from the tank 15, via the line 16, to the friend exchanger 13. The pump 18 is adapted to give the ureal solution a higher pressure in the line 16 than the exhaust gas pressure in the second part 3b of the exhaust line. The control unit 17 is adapted to control the EGR valves 11a, b so that an optimal amount of exhaust gases is recirculated through the return line 10. The control unit 17 simultaneously controls the EGR valves 11a, b so that a mandatory amount of exhaust gases from the first part of the exhaust line 3a is led through the heat exchanger 13. This amount is so adapted that it heats the pressurized urea solution to a suitable temperature.

ESÜ 582 Such a suitable temperature may be just below the evaporation temperature of the urea solution at the pressure prevailing in line 16. Thus, the urea solution provides a heating while remaining in the liquid form in line 16. However, the temperature is advantageously higher than the evaporation temperature of the urea solution. at the pressure exerted by the second part 3b of the exhaust line. The urea solution is thus transported in liquid form after heating in the heat exchanger 13 further in the line 16 to the injection means 19. The control unit 17 controls the injection means 19 so that it injects a calculated amount of urea solution into the second part 3b of the exhaust line in a position upstream of the catalyst 21. has a higher temperature than its evaporating temperature at the pressure prevailing in the second part 3b of the exhaust line, the urease solution evaporates substantially immediately after it has been injected into the second part 3b of the exhaust line. The evaporated urea solution provides ammonia in the gas form which is mixed with the exhaust gases. The mixture of ammonia and the exhaust gases is then passed through the catalyst 21 where the nitrogen of the nitrogen oxides in the exhaust gases reacts with the nitrogen in the ammonia so that. nitrogen gas is formed. The oxygen of the nitrogen oxides reacts with the hydrogen in the ammonia to form water. The nitrogen oxides in the exhaust gases are thus reduced in the catalyst to nitrogen gas and water vapor. With the correct dosage of urea, the diesel engine's 1 emissions of nitrogen oxides can be greatly reduced. The heating of the urea solution in the heat exchanger 13 results in a corresponding cooling of the recirculating exhaust gases in the return line 10. Thus, the EGR system provides an additional cooling capacity in addition to the capacity of the EGR cooler 12 to cool the recirculating exhaust gases before mixing with the air in the inlet line 7.

Fig. 2 shows a supercharged diesel engine 1 provided with a turbocharger 4, 5 which uses the exhaust gas energy of the diesel engine 1 to compress the air led to the diesel engine 1. The diesel engine 1 here comprises an arrangement for supplying a medium in the form of a fuel. to a second part 3b of an exhaust line adjacent to a. Particle filter 20. By supplying fuel to the exhaust gases and burning it adjacent to the particulate filter 20, the exhaust gases reaching the particulate filter 20 provide an elevated temperature. The exhaust gases here have a temperature so that they burn the remaining soot particles in particle 20. lter 20. The arrangement includes a fuel source which can be a fuel rich 15 ”. The fuel, which is thus diesel oil, is led from the tank 15 ", via a line 16", to a second part 3b of the exhaust line which is thus located after the turbine 4. A control unit 17 "is adapted to control the supply of the fuel by activating an 18 ”pump. The pump 18 'is adapted to pressurize and transport the fuel, via a heat exchanger 13 °, to an injection means 19 "which injects a calculated amount of fuel 530 582 into the exhaust line 3. The injection means 19 * is connected to the second part 3b of the exhaust line. so that it injects fuel downstream of the turbine 4 with respect to the direction of exhaust of the exhaust gases in the exhaust line 3. The supplied fuel is intended to evaporate in the exhaust line 3. An exhaust line 23, which comprises a valve 22 and the heat exchanger 13 ", extends between the exhaust line first part 3a and the second part 3b of the exhaust line.

During operation of the diesel engine 1, the control unit 17 ”can initiate a cleaning process of the particle filter 20 at predetermined distances and / or predetermined time intervals. Alternatively, the control unit 17 ”can receive information regarding the pressure drop across the particle filter from suitably placed pressure sensors and initiate a cleaning process of the particle filter 20 when the pressure drop across the particle filter 20 exceeds a predetermined value. When the particle filter 20 is to be cleaned, the control unit 17 activates the pump 18 which transports a fuel from the tank 152 via the line 16 "to the heat exchanger 13". The pump 18 ”is adapted to give the fuel a pressure that exceeds the pressure of the exhaust gases in the second part 3b of the exhaust line. The control unit 17 is adapted to control the valve 22 so that a suitable amount of exhaust gases is led through the exhaust line 23 and the heat exchanger 13 ". This amount is so adjusted that it heats the pressurized fuel to a suitable temperature. This temperature may be just below the pre-freezing temperature of the fuel at the prevailing pressure in line 16 ”. However, the temperature is advantageously higher than the evaporation temperature of the fuel at the pressure prevailing in the second part 3b of the exhaust line. The fuel is thus transported in liquid form in the line 16 'from the heat exchanger 13' to the injector 19 '. The injector 19 'injects the calculated amount of fuel into the second part 3b of the exhaust line in a position upstream of the particle filter 20. Since the fuel has a higher temperature than its evaporation temperature at the pressure prevailing in the second part 3b of the exhaust line, the fuel evaporates substantially immediately in the second part of the exhaust line 3b. The vaporized fuel is mixed with the exhaust gases after which it provides an oxidation in an oxidation catalyst so that the exhaust gases provide an elevated temperature. The exhaust gases now have a temperature so that they burn and thus clean the particle filter 20 from soot particles as they pass it again.

The invention is not limited to the embodiment described above, but it can be varied freely within the scope of the claims. It is of course also possible to heat and supply a urea solution with the arrangement shown in the embodiment in Fig. 2. Correspondingly, it is also possible to heat and supply fuel with the arrangement shown in the embodiment shown in Fig. 1. exemplified arrangements enable 530 582. the supply of essential arbitrary liquid media which are adapted to evaporate when they are led into an exhaust line. The arrangement according to the invention may also comprise components for turning and supplying both a urea solution and fuel. i A common heat exchanger could be used here for heating the urea solution and the fuel. Instead of, as shown in Fig. 1, arranging the EGR cooler 12 and friend changer 13 in parallel lines of line sections, they can be arranged in series in the same line in the line section.

Claims (20)

10 15 20 25 30 35 530 582 10 Patent claims Arrangement of an overcharged internal combustion engine (1), the arrangement comprising an exhaust line (3) of the internal combustion engine (1) which has a first part 3a which is located upstream of a turbine (4) and a second part 3b which is located downstream of said turbine (4) with respect to the intended flow path of the exhaust gases through the exhaust line (3), a media source (15, 15 ') comprising a liquid medium and an injection means (19, 19') adapted to inject the medium into the exhaust line second part (3b), characterized in that the arrangement comprises a heat exchanger (13, 13 °) which is adapted to flow through the liquid medium and exhaust gases from the first part (3a) of the exhaust line so that the medium provides a heating of the exhaust gases from the exhaust line. first part (3 a) in the heat exchanger (13, 13 °) before it is injected into the second part (3b) of the exhaust line. Arrangement according to claim 1, characterized in that the heat exchanger (13, 13 ") is adapted to flow through the exhaust gases from the first part (3a) of the exhaust line so that the medium provides a heating in the heat exchanger (13, 13") to a temperature exceeding the evaporation temperature of the medium at the pressure prevailing in the second part of the exhaust line (3b). Arrangement according to claim 1 or 2, characterized in that the arrangement comprises pressure supply means (18, 18 ') which are adapted to give the medium a higher pressure in the heat exchanger (13, 13 *) than the pressure prevailing in the second part of the exhaust line ( 3b). Arrangement according to claim 3, characterized in that the heat exchanger (13, 13 ") is adapted to flow through the exhaust gases from the first part (3a) of the exhaust line so that the medium provides a heating in the heat exchanger (13, 13") to a temperature which is lower than the evaporation temperature of the medium in the heat exchanger (13, 13 ”). Arrangement according to any one of the preceding claims, characterized in that said injection means (19, 19 ") are arranged in a position so that the medium is injected into or upstream of an exhaust gas cleaning component (20, 21) in the second part (3b) of the exhaust line. . Arrangement according to Claim 5, characterized in that the medium is a urea solution and in that the exhaust gas purifying component is a catalyst (21). 10 20 30 35 530 582 ll Arrangement according to Claim 5, characterized in that the medium is fuel and in that the exhaust gas purifying component is a particle filter (20). Arrangement according to any one of the preceding claims, characterized in that the arrangement comprises a conduit (16, 16 '), which is adapted to guide the medium from said media source (15, 15 ") to the injection means (19, 19"), and a control unit (17, 17 ”), which is adapted to control the flow of the medium through said line (16, 16,) and thus the amount of the medium which is injected into the second part of the exhaust line (3b). Arrangement according to one of the preceding claims, characterized in that the heat exchanger (13, 13 ") is adapted to flow through exhaust gases which are led in a line (10) which has a distance from the first part (3a) of the exhaust line to an inlet line (7). for air to the internal combustion engine (1). Arrangement according to claim 9, characterized in that the heat exchanger (13, 13 ') is adapted to flow through exhaust gases which are led in a line (23) which has a distance from the first part (3a) of the exhaust line to the second part (3 of the exhaust line). b). A method of a supercharged internal combustion engine (1), wherein the internal combustion engine (1) comprises an exhaust line (3) having a first part 3a located upstream of a turbine (4) and a second part 3b located downstream of said turbine (4). ) with respect to the intended direction of flow of the exhaust gases through the exhaust line (3), a media source (15, 15 ") comprising a liquid medium and an injection means (19, 19 ') adapted to inject the medium into the second part of the exhaust line. (3b), by the step of passing the liquid medium and exhaust gases from the first part (3a) of the exhaust line through a heat exchanger (13, 13 °) so that the medium provides a heating of the exhaust gases from the first part (3a) of the exhaust line in the heat exchanger (13, 13 °) before it is injected into the second part (3b) of the exhaust line. Method according to claim 1 1, characterized by the step of providing a heating of the medium in the heat exchanger (13, 13 °) to a temperature which exceeds the evaporation temperature of the medium at the pressure prevailing in the second part (3b) of the exhaust line. Method according to claim 11 or 12, characterized by the step of giving the medium a higher pressure in the friend exchanger (13, 13 ') than the pressure prevailing in the second part (3b) of the exhaust line. 15 20 25 530 582 12 An arrangement according to claim 13, characterized by the step of providing a heating of the medium in the heat exchanger (13, 13 °) to a temperature lower than the evaporation temperature of the medium in the heat exchanger (13, 13 '). Method according to any one of the preceding claims 11-14, characterized by the step of arranging said injection means (19, 19 °) in a position so that the medium is injected into or upstream of an exhaust gas purifying component (20, 21) in the second part of the exhaust line. (3b). Method according to claim 15, characterized by the step of using a urea solution as medium and a catalyst (2 l) as exhaust gas purifying component. Method according to claim 15, characterized in that the step of using fuel as medium and that a particle terlter (20) as exhaust gas purifying component. Method according to any one of the preceding claims 11-17, characterized by the steps of directing the medium from said media source (15, 15 ") to the injection means (19, 19") in a conduit and controlling the fate of the medium through said conduit ( 16, 16,) by means of a control unit (17, 17). A method according to any one of the preceding claims 11-18, characterized by the step of conducting exhaust gases in a line (10), which has a distance from the first part (Sa) of the exhaust line to an inlet line (7) for air to the internal combustion engine (1). ), through the heat exchanger (13, 13 *). Method according to claim 19, characterized by the step of conducting exhaust gases in a line (10), which has a distance from the first part (3a) of the exhaust line to the second part (3b) of the exhaust line, through the heat exchanger (13, 13 ").