INTERNAL COMBUSTION ENGINE FOR A MOTOR VEHICLE

Abstract

An internal combustion engine for a motor vehicle may include at least one cylinder including a combustion chamber for combusting a fuel-air mixture introduced into the combustion chamber. The engine may also include at least one fuel injector and a fresh air feed. The engine may further include an exhaust gas discharge for discharging exhaust gas from the combustion chamber and an exhaust gas recirculation for recirculating the discharged exhaust gas into the combustion chamber. Additionally, the engine may include a heat exchanger arranged in the exhaust gas recirculation, the heat exchanger may include at least one first fluid path and at least one second fluid path. A knock number of the fuel may be increased when the fuel flows through the heat exchanger. The at least one second fluid path may fluidically communicate with the at least one fuel injector.

Claims

1. An internal combustion engine for a motor vehicle, comprising: at least one cylinder including a combustion chamber for combusting a fuel-air mixture introduced into the combustion chamber; at least one fuel injector for injecting a fuel into the combustion chamber; a fresh air feed for feeding fresh air into the combustion chamber of the at least one cylinder; an exhaust gas discharge for discharging exhaust gas from the combustion chamber; an exhaust gas recirculation for recirculating the exhaust gas discharged from the at least one cylinder into the combustion chamber, the exhaust gas recirculation fluidically communicating with the fresh air feed and the exhaust gas discharge; a heat exchanger arranged in the exhaust gas recirculation, the heat exchanger including at least one first fluid path integrated into the exhaust gas recirculation and through which the exhaust gas to be recirculated is flowable, the heat exchanger further including at least one second fluid path, fluidically separated from the at least one first fluid path, through which the fuel is flowable; wherein a knock number of the fuel is increased when the fuel flows through the heat exchanger; and wherein the at least one second fluid path fluidically communicates with the at least one fuel injector.

2. The internal combustion engine according to claim 1, wherein the heat exchanger is a catalytic fuel evaporator for chemically converting the fuel flowing through the at least one second fluid path.

3. The internal combustion engine according to claim 1, further comprising a catalytic coating disposed in the at least one second fluid path.

4. The internal combustion engine according to claim 1, wherein the heat exchanger is configured to convert long-chain hydrocarbons contained in the fuel into short-chain hydrocarbons.

5. The internal combustion engine according to claim 1, wherein the heat exchanger configured to convert a hydrocarbon compound C.sub.8H.sub.18 into a hydrocarbon compound C.sub.3H.sub.8.

6. The internal combustion engine according to claim 1, wherein the heat exchanger is configured such that a chemical conversion of hydrocarbons contained in the fuel increases the knock number of the fuel by at least 2 RON.

7. The internal combustion engine according to claim 1, further comprising a fuel cooler arranged between the at least one second fluid path and the at least one fuel injector for cooling the fuel exiting the heat exchanger.

8. The internal combustion engine according to claim 7, wherein the fuel cooler is a second heat exchanger through which the fuel to be cooled and a coolant fluidically separated from the fuel are flowable, and wherein the coolant is thermally coupled to the fuel within the second heat exchanger for cooling of the fuel.

9. The internal combustion engine according to claim 1, further comprising an exhaust gas cooler arranged between the at least one first fluid path and the fresh air feed for cooling the exhaust gas exiting the heat exchanger.

10. The internal combustion engine according to claim 9, wherein the exhaust gas cooler is a second heat exchanger through which the exhaust gas to be cooled and a coolant fluidically separated from the exhaust gas are flowable, and wherein the exhaust gas is thermally coupled to the coolant within the second heat exchanger for cooling the exhaust gas.

11. A motor vehicle, comprising: an internal combustion engine including: at least one cylinder including a combustion chamber for combusting a fuel-air mixture introduced into the combustion chamber; at least one fuel injector for injecting a fuel into the combustion chamber; a fresh air feed for feeding fresh air into the combustion chamber of the at least one cylinder; an exhaust gas discharge for discharging exhaust gas from the combustion chamber; an exhaust gas recirculation for recirculating the exhaust gas discharged from the at least one cylinder into the combustion chamber, the exhaust gas recirculation fluidically communicating with the fresh air feed and the exhaust gas discharge; a heat exchanger arranged in the exhaust gas recirculation, the heat exchanger including at least one first fluid path integrated into the exhaust gas recirculation and through which the exhaust gas to be recirculated is flowable, the heat exchanger further including at least one second fluid path fluidically separated from the at least one first fluid path through which the fuel is flowable; wherein a knock number of the fuel is increased when the fuel flows through the heat exchanger; and wherein the at least one second fluid path fluidically communicates with the at least one fuel injector.

12. The motor vehicle according to claim 11, further comprising: a refrigeration system including a refrigeration circuit through which a refrigerant is flowable; the refrigeration circuit including at least one of: a fuel cooler for cooling the fuel exiting the heat exchanger; and an exhaust gas cooler for cooling the exhaust gas exiting the heat exchanger; wherein the refrigerant circuit is configured to cool at least one of (i) the fuel flowing through the fuel cooler and (ii) the exhaust gas flowing through the exhaust gas cooler.

13. The motor vehicle according to claim 12, further comprising an air conditioning system including the refrigeration system for air conditioning a vehicle interior.

14. The motor vehicle according to claim 11, wherein the heat exchanger is a catalytic fuel evaporator for chemically converting the fuel flowing through the at least one second fluid path.

15. The motor vehicle according to claim 11, further comprising a catalytic coating disposed in the at least one second fluid path.

16. The motor vehicle according to claim 11, wherein the heat exchanger is configured to convert long-chain hydrocarbons contained in the fuel into short-chain hydrocarbons.

17. The motor vehicle according to claim 11, wherein the heat exchanger is configured such that a chemical conversion of hydrocarbons contained in the fuel increases the knock number of the fuel by at least 2 RON.

18. The motor vehicle according to claim 12, wherein the fuel cooler is a second heat exchanger through which the fuel to be cooled and the refrigerant, fluidically separated from the fuel, are flowable, and wherein the refrigerant is thermally coupled to the fuel within the second heat exchanger for cooling of the fuel.

19. The motor vehicle according to claim 12, wherein the exhaust gas cooler is a second heat exchanger through which the exhaust gas to be cooled and the refrigerant, fluidically separated from the exhaust gas, are flowable, and wherein the refrigerant is thermally coupled to the exhaust gas within the second heat exchanger for cooling the exhaust gas.

20. An internal combustion engine for a motor vehicle, comprising: at least one cylinder including a combustion chamber for combusting a fuel-air mixture introduced into the combustion chamber; at least one fuel injector for injecting a fuel into the combustion chamber; a fresh air feed for feeding fresh air into the combustion chamber of the at least one cylinder; an exhaust gas discharge for discharging exhaust gas from the combustion chamber; an exhaust gas recirculation for recirculating the exhaust gas discharged from the at least one cylinder into the combustion chamber, the exhaust gas recirculation fluidically communicating with the fresh air feed and the exhaust gas discharge; a heat exchanger arranged in the exhaust gas recirculation, the heat exchanger including at least one first fluid path integrated into the exhaust gas recirculation and through which the exhaust gas to be recirculated is flowable, the heat exchanger further including at least one second fluid path, fluidically separated from the at least one first fluid path, through which the fuel is flowable; a fuel cooler arranged between the at least one second fluid path and the at least one fuel injector for cooling the fuel exiting the heat exchanger; an exhaust gas cooler arranged between the at least one first fluid path the fresh air feed for cooling the exhaust gas exiting the heat exchanger; wherein a knock number of the fuel is increased when the fuel flows through the heat exchanger; and wherein the at least one second fluid path fluidically communicates with the at least one fuel injector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings show:

[0028] FIG. 1 an example of an internal combustion engine according to the invention,

[0029] FIG. 2 the fuel evaporator arranged in the exhaust gas recirculation of the internal combustion engine that is substantial for the invention in a separate schematic representation.

DETAILED DESCRIPTION

[0030] In a schematic representation, FIG. 1 illustrates an example of an internal combustion engine 1 according to the invention, which can be embodied as spark-ignition engine. In the example of FIG. 1, the internal combustion engine 1 is realised as four-cylinder engine and accordingly comprises four cylinders 2, in which in each case a combustion chamber 3 for combusting a fuel-air mixture introduced into the respective combustion chamber 3 is present. It is to be understood that in versions of the example, a different number of cylinders 2 and thus also a different number of combustion chambers 3 can be provided.

[0031] For each combustion chamber 3, a respective fuel injector 3 for injecting fuel 15 into the combustion chamber 3 concerned is provided in the internal combustion engine 1. The fuel injectors 30 communicate via fuel lines 31 with a fuel reservoir 32 which is only schematically represented in the figures, from which the fuel injectors 30 are supplied with fuel 15. Typically, the fuel reservoir 32 is a fuel tank of the vehicle equipped with the internal combustion engine 1 according to the invention.

[0032] Furthermore, the internal combustion engine 1 comprises a fresh air feed 4 for feeding fresh air 6 into the combustion chambers 3 of the cylinders 2. The fresh air feed 4 can be part of a fresh air system of the internal combustion engine 1 which is not shown in more detail in the figures. Feeding fresh air 6 into the combustion chambers 3 can be controlled with the help of a valve device 33 arranged in the fresh air feed 4. Furthermore, the internal combustion engine 1 comprises an exhaust gas discharge 5 for discharging exhaust gas 7 generated in the combustion chambers 3 of the cylinders 2 by combustion of the fuel-air mixture. The exhaust gas discharge 5 can be part of an exhaust system which is not shown in more detail in the figures, which discharges the exhaust gas 7 from the combustion chambers 3 via individual exhaust pipes 9 usually described as bends.

[0033] The internal combustion engine 1 also comprises an exhaust gas recirculation 8 for partly recirculating the exhaust gas 7 discharged from the cylinders 2 via the fresh air feed 4 into the combustion chambers 3 of the internal combustion engine 1. For this purpose, a branch 24 is provided in the exhaust gas discharge 5, in which the exhaust gas recirculation 8 branches off the exhaust gas discharge 5. A part of the exhaust gas 7 discharged from the cylinders 2 of the internal combustion engine 1 exits the exhaust gas discharge 5 in the branch 24 and is subsequently conducted through the exhaust gas recirculation 8. The exhaust gas recirculation 8 can comprise a recirculation line 10 which can be flowed through by the exhaust gas 7 to be recirculated and fluidically communicates with the fresh air feed 4 and the exhaust gas recirculation 8. The recirculation line 10 can be designed in the manner of a recirculation pipe 11 at least in sections. The recirculation of the exhaust gas 7 into the combustion chambers 3 can be controlled with the help of a valve device 34 arranged in the exhaust gas recirculation 8.

[0034] In the exhaust gas recirculation 8 a heat exchanger 40 is arranged, which can be designed as a conventional stacked-plate heat exchanger 41. The stacked-plate heat exchanger 41 comprises first and second fluid paths 42a, 42b which are arranged fluidically separated and alternately adjacent to one another in the stacked-plate heat exchanger 41. The construction of the stacked-plate heat exchanger 41 is only roughly schematically indicated in FIG. 1. The first fluid paths 42a are part of the exhaust gas recirculation 8 and for this purpose fluidically integrated in the recirculation line 10 or in the recirculation pipe 11. The first fluid paths 42a of the heat exchanger 40 are thus flowed through by the exhaust gas 7 to be recirculated.

[0035] The second fluid paths 42b are flowed through by fuel 15 fluidically separately from the first fluid paths 42a, which fuel 15 is drawn from the fuel reservoir 32 via a fuel feed line 43. The knock number of the fuel 15 is elevated in the heat exchanger 40 or in the stacked-plate heat exchanger 41. For this purpose, the second fluid paths 42b of the heat exchanger 40 are designed as catalytic fuel evaporator 12 for chemically converting the fuel 15 flowing through the second fluid paths 42b.

[0036] FIG. 2 shows a single second fluid path 42b of the heat exchanger 40 or of the stacked-plate heat exchanger 41, which is realised as fuel evaporator 12, in a separate representation. According to FIG. 2, each second fluid path 42b of the fuel evaporator 12 can comprise a respective tube body 16 by means of which the second fluid path 42b is incorporated in the fuel feed line 43. The tube body 16 delimits a tube body interior 17 that can be flowed through by the fuel 15. On an internal wall 25, in particular on an internal circumferential wall of the tube body 16, a catalytic coating 18 is present by means of which the long-chain hydrocarbons present in the fuel 15 are converted into shorter-chain hydrocarbons. For this purpose, oxidation reactions occur in the tube body interior 17 with the help of the catalytic coating 18. The temperatures required for the oxidation reactions to proceed are reached in the fuel 15 in that heat is extracted from the exhaust gas 7 flowing through the first fluid paths 42a and transferred to the fuel 15. In the process, the evaporation of the fuel 15 takes place. During the course of the evaporation of the fuel 15, the long-chain hydrocarbon compound C.sub.8H.sub.18 contained in the fuel 15 is converted by adding oxygen (O.sub.2) as oxidant into the short-chain hydrocarbon compound C.sub.3H.sub.8, wherein carbon dioxide (CO.sub.2) is liberated. The oxidation of the fuel 15 preferably takes place in the presence of severe air deficiency (<0.1).

[0037] In addition, the heat exchanger 40 or the fuel evaporator 12 can be equipped with an electric heating device 19. The electric heating device 19 then serves for heating the fuel 15 to be converted. The electric heating device 19 can be designed for example as electric heating coil 20 which is only roughly schematically indicated in FIG. 2, which is arranged in the tube body interior 17. With the help of the electric heating device 19, the temperature that is required for the oxidation reactions can be reached in the fuel 15 without the calorific value of the fuel 15 being reduced in the process. When the temperature of the fuel 15 to be converted is high enough for carrying out the oxidation reactions when entering the fuel evaporator 12 an additional heating of the fuel 15 by means of the electric heating device 19 can be dispensed with.

[0038] The gaseous fuel 15 with the short-chain hydrocarbon compounds C.sub.3H.sub.8 exiting the heat exchanger 40 or fuel evaporator 12 after the conversion has a higher knock resistance than the fuel 15 with the long-chain hydrocarbon compound C.sub.8H.sub.18 before entering the heat exchanger 40. In the example scenario, the octane or knock number is increased during the course of the conversion from RON 98 to a value of RON>=100.

[0039] On the outlet side, the second fluid paths 42b of the heat exchanger 40 fluidically communicate with the fuel injectors 30 for introducing the fuel 15 with elevated knock number into the combustion chambers 3 of the internal combustion engine 1. For this purpose, the second fluid paths 42b are connected to the fuel line 31 via whichas already explained abovefuel 15 from the fuel reservoir 32 is injected into the combustion chambers 3 without direct increase of the knock number.

[0040] In order to cool and liquefy the fuel 15 with elevated knock number before injection into the combustion chambers 3 a fuel cooler 27 for cooling or liquefying the fuel 15 exiting the heat exchanger 40 is arranged downstream of the heat exchanger 40, i.e. between the second fluid paths 42b of the heat exchanger 40 and the fuel injectors 30. The fuel cooler 27 can also be designed as heat exchanger 28 or comprise such a heat exchanger 28. Conceivable is a technical realisation of the heat exchanger 28 as so-called finned-tube heat exchanger or as conventional stacked-plate heat exchanger. Other technical forms of realisation are also known to the specific person skilled in the art. The heat exchanger 28 is flowed through by the fuel 15 to be cooled in the known manner.

[0041] Apart from this, the heat exchanger 28fluidically separated from the fuel 15is flowed through by a coolant which is not shown in more detail in FIG. 1. Within the heat exchanger 28, the coolant is thermally connected to the fuel 15 in the known manner for cooling the fuel 15. By transferring heat from the fuel 15 to the coolant, the temperature of the fuel 15 is reduced. In the process, the fuel 15 is liquefied. Having left the fuel cooler 27 designed as heat exchanger 28, the fuel 15 is introduced into the fuel line 31 with elevated knock number via a junction point 29 wheremixed with the fuel 15 with non-elevated knock number, which is directly taken from the fuel reservoir 32it is introduced into the combustion chambers 3 via the fuel lines 31 and the fuel injectors 30.

[0042] In order to also cool the exhaust gas 7 prior to the intermixing with the fresh air 6 in the fresh air feed 4 and the renewed introduction of the exhaust gases 7 into the combustion chambers 3, an exhaust gas cooler 21 for cooling the exhaust gas 7 exiting the heat exchanger 40 is arranged in the exhaust gas recirculation 8 downstream of the heat exchanger 40, i.e. between the first fluid paths 42a of the heat exchanger 40 and the fresh air feed 4. In FIG. 1, the exhaust gas cooler 21 is only schematically indicated. The exhaust gas cooler 21 can also be designed as heat exchanger 22 or comprise such a heat exchanger 22. Conceivable is a technical realisation of the heat exchanger 22 as so-called finned-tube heat exchanger or as conventional stacked-plate heat exchanger. Other technical forms or realisation are also known to the specific person skilled in the art. In the known manner, the heat exchanger 22 is flowed through by the exhaust gas 7 to be cooled. Apart from this, the heat exchanger 22 is flowed throughfluidically separated from the exhaust gas 7 to be recirculatedby a coolant which is not shown in more detail in FIG. 1. Within the heat exchanger 22, the coolant is thermally coupled to the exhaust gas 7 in the known manner for cooling the exhaust gas 7. By transferring heat from the exhaust gas 7 to the coolant, the temperature of the exhaust gas 7 is reduced.

[0043] Having flowed through the exhaust gas cooler 21, the cooled exhaust gas 7 is discharged from the exhaust gas recirculation 8 via a branch 23 which opens into the fresh air feed 4 and together with fresh air 6 again introduced into the cylinders 2 of the internal combustion engine 1.

[0044] The internal combustion engine 1 introduced above can be optionally used in a motor vehicle which is equipped with a refrigeration system (not shown in the figures). Such a refrigeration system comprises a refrigeration circuit in which a refrigerant circulates (not shown). The refrigeration system can be part of an air conditioning system provided in the motor vehicle by means of which the vehicle interior of the motor vehicle is air conditioned. In the refrigeration circuit, the exhaust gas cooler 21 designed as heat exchanger 22 and, alternatively or additionally, the fuel cooler 27 designed as heat exchanger 28, can be incorporated. In the first case, the refrigerant of the refrigeration system serves as coolant for cooling the exhaust gas 7 flowing through the exhaust gas cooler 21. In the second case, the refrigerant of the refrigeration system serves as coolant for cooling the fuel 15 flowing through the fuel cooler 27.