FR2875849A1 - Internal combustion engine for motor vehicle, has turbocharger interposed between pressure wave supercharger and engine head, where turbocharger and supercharger double supercharge engine at low and high engine rotation speeds, respectively - Google Patents

Abstract

The engine has a turbocharger (26) interposed between a pressure wave supercharger (14) and an engine head (8) with reference to intake and exhaust systems (4, 6). The supercharger and the turbocharger are used for double supercharging the engine at engine`s low and high rotation speeds, respectively. The intake system includes air inlet conduits (10, 12) extending parallel to each other in downstream of an air filter. An independent claim is also included for a method for operating an internal combustion engine of a motor vehicle.

Description

The invention relates to motor vehicle engines, and

  particular the supercharging function of these engines.

  It is known to perform a supercharging of air internal combustion engines, which is to increase the pressure of air from outside in the intake circuit.

  It is known to perform this supercharging by means of a pressure wave compressor or PWS (Pressure Wave Supercharger). This compressor consists of a rotor formed by one or more layers of channels. The rotor is in contact with lights with the exhaust system and the intake circuit. The pressure difference existing between the gases of these two circuits causes a shock wave inside each tube of the rotor. The good sizing of the channels and a correct phasing of the opening and closing of the compressor rotor lights make it possible to ensure the supercharging of the engine. Such a device is for example disclosed in the document EP-205 843. One of the problems posed by this technology lies however in the control of the so-called recirculated gas rate in the engine, that is to say the rate of gas circuit exhaust pipes intended to be reintroduced into the intake circuit. These recirculated gases can in fact strongly limit the specific high-speed performance of engines using such compressors.

  It is also known to perform turbocharging supercharging comprising a turbine set in motion by the exhaust gas and actuating a compressor located in the intake circuit.

  It is now difficult to find a system to ensure a sufficient level of supercharging for both low and high revolutions of the engine. (The problem is all the more acute because the engine displacement is low, because the efficiency of small turbines and small compressors is lower than that of larger compressors.) The supercharging devices are indeed sized to reach their optimum operating in a certain speed range of the engine. This partial adaptation is therefore paid either by a fall in performance at high speed, or by a high inertia of the engine at low speed.

  In addition, clean combustion modes, ie low emissions, rely on high levels of recirculated gas (or EGR gas) as well as high supercharging pressures. However, these two points are hardly compatible with traditional supercharging systems.

  An object of the invention is to improve the supercharging function to increase the performance of the engine.

  For this purpose, there is provided according to the invention a vehicle engine comprising a pressure wave compressor and a turbocharger.

  In a preferred embodiment, there is provided a double supercharging with an element dedicated to low revolutions of the engine and another dedicated to high revolutions. In other words, the pressure wave compressor is preferably used for low revolutions of the engine, knowing that this compressor is completed by a turbocharger sized to ensure him, supercharging at high speeds. Indeed, in low speeds, the turbocharger type systems are not very efficient because of their high response time (turbo lag) and volumetric compressor type systems (roots, Iysholm, e-boost, etc.) are very penalizing in terms of energy. In addition, the pressure wave compressor can act as an effective low pressure EGR valve. All that is needed is to control the rotational speed of the compressor.

  The pressure wave compressor has a very low response time and energy requirements also very low to operate. It must simply compensate for any friction on the motor shaft. It is therefore the ideal element for low revolutions of the engine, in addition to a turbocharger that would be dedicated to high revs.

  The double boost of the engine by the pressure wave compressor and the turbocharger provides the best possible performance of the engine throughout its operating range.

  The engine according to the invention may also have at least any of the following characteristics: the turbocharger is interposed between the pressure wave compressor and a cylinder head of the engine by reference to an engine intake circuit; it is designed to allow the engine to be supercharged together by means of the pressure wave compressor and the turbocharger; it is designed to allow the engine to be supercharged by means of the single pressure wave compressor; it is arranged to allow the engine to be supercharged by means of the single turbocharger; it is arranged to allow the engine to run without supercharging; it comprises a bypass duct of the turbocharger compressor and means for controlling a circulation of gas in the duct; it comprises a bypass duct of the turbocharger turbine and means for controlling a circulation of gas in the duct; it comprises a bypass duct of the exhaust side pressure wave compressor and means for controlling a circulation of gas in the duct; it comprises a bypass duct of the intake-side pressure wave compressor and means for controlling a circulation of gas in the duct; it comprises a cooler interposed between the pressure wave compressor and the turbocharger with reference to an intake circuit; it comprises a cooler located on the intake side downstream of the pressure wave compressor and the turbocharger; it comprises an exhaust gas after-treatment system interposed between the turbocharger and the pressure wave compressor; and it comprises an exhaust aftertreatment system located downstream of the turbocharger and the pressure wave compressor.

  The invention also provides a method of operating a vehicle engine, in which the engine is supercharged by means of a pressure wave compressor and a turbocharger.

  Said supercharging corresponding to a first mode of operation, the method according to the invention may furthermore have at least one of the following characteristics: a second mode of operation is implemented in which the engine is supercharged by means of the single pressure wave compressor; a third mode of operation is implemented in which the engine is supercharged by means of the single turbocharger; and a fourth mode of operation is implemented in which no supercharging is performed.

  Other features and advantages of the invention will become apparent in the following description of two preferred embodiments given by way of nonlimiting example with reference to the accompanying drawings, in which: FIGS. 1 and 2 are two diagrammatic views of two embodiments of the engine according to the invention.

  First Embodiment We will first describe the main components constituting the motor in the first embodiment of the invention illustrated in FIG.

  The engine 2 comprises an intake circuit 4 and an exhaust circuit 6 located respectively upstream and downstream of a cylinder head 8 of the engine comprising chambers in which are received movable pistons.

  The intake circuit 4 comprises two air intake ducts 10, 12 extending in parallel with each other downstream of an engine air filter. The conduit 10 opens into a pressure wave compressor 14 of a type known per se. The air exits the compressor through a duct 16 which passes through a cooler 18. The ducts 12 and 16 open into a member 20. This member is connected by a duct 22 to a compressor 24 of a turbocompressor 26, and via a duct 28. directly to a conduit 30 extending downstream of the compressor 24 from the latter to lead to a cooler 32. The conduit 28 is therefore a bypass of the compressor 24. The member 20 can control the opening or closing at the choice of this bypass duct 28 and the duct 22.

  The cooler 32 is connected by a duct 34 to the cylinder head 8.

  From the cylinder head 8, the exhaust circuit 6 comprises a duct 40 connecting the cylinder head 8 to a member 42 similar to the member 20. Thus, a duct 44 connects the member 42 to a turbine 46 the turbocharger, which opens through a conduit 48 in a post-processing device 50. The member 42 is also associated with a bypass conduit 52 communicating at its upstream end with the member 42 and its downstream end with the conduit 48 .

  The after-treatment system 50 will for example be a NOx-Trap type device, an oxidation or reduction catalyst, a particulate filter, a combination thereof, etc. The device 50 communicates via a conduit 54 with a member 56 similar to the member 20. Thus, a conduit 60 connects the member 56 to the pressure wave compressor 14, which communicates via another conduit 62 with a second after-treatment device 64 which may be of one of the types listed with reference to the device 50. Furthermore, a bypass duct 66 directly connects the member 56 to the post-processing device 64.

  Finally, the motor comprises a member 70 adapted to rotate the pressure wave compressor 14. In a manner known per se, the turbine 46 is connected by a shaft 72 to the compressor 24 to rotate the latter.

  As can be seen, the turbocharger 26 is thus interposed between the pressure wave compressor 14 and the cylinder head 8 with reference to the circuits 4 and 6.

  In addition, on the intake side, the cooler 18 is interposed between the pressure wave compressor 14 upstream and the compressor 24.

  Still on the intake side, the cooler 32 extends downstream of the two supercharging devices 14 and 24.

  On the exhaust side, the engine comprises the two aftertreatment devices 50 and 64. The first of them, 50, is interposed between the upstream turbine 46 and the downstream pressure wave compressor 14, while the second, 64, extends downstream of these two supercharging devices.

  The engine according to the invention may have several modes of operation, ranging from the so-called atmospheric mode, that is to say without supercharging mode, to the dual supercharging mode by the pressure wave compressor and the turbocharger, via modes wherein the supercharging is provided by the pressure wave compressor alone or the turbocharger alone. These modes of operation can be implemented in whole or in part on the same engine. The transition from one mode to another is controlled by the members 20, 42 and 56 controlling the bypass ducts, and the ducts which are parallel thereto, which members are themselves controlled by the computer controlling the entire operation. of the motor.

  Dual Boost Mode of Operation In this mode of operation, the engine operates the two booster stages, namely the pressure wave compressor 14 and the turbocharger 26. Thus, the air from the duct 10 enters the engine. pressure wave compressor 14, is compressed by the exhaust gas, then leaves. This air, possibly mixed with exhaust gas, enters the charge cooler 18 and then into the compressor 24. In this mode of operation, no air enters through the conduit 12 and the bypass 28 is closed. In other words, all the gases coming from the pressure wave compressor 14 also pass through the compressor 24. At their outlet from the compressor, the gases enter the cooler 32 and then enter the cylinder head 8.

  The gases leaving the cylinder head 8 pass into the turbine 46, except possibly a part of these gases that can pass directly downstream of the turbine without passing through the latter through the bypass 52. Whether or not they pass through the turbine, the The gases then pass through the pressure wave compressor 14, except possibly a part of these gases which can be directly redirected downstream of this compressor by means of the bypass 66. The gases passing through the pressure wave compressor 14 serve to compress the intake air. Part of these gases can also be recirculated in the intake circuit by means of the pressure wave compressor. The fraction of the gases exiting the pressure wave compressor via line 62, possibly mixed with air, passes into the aftertreatment system 64, as do the gases arriving via line 66.

  Modes of operation with simple supercharging The engine computer may, however, control another operating mode of the engine in which the supercharging is provided solely by the pressure wave compressor 14, without the turbocharger 46 intervening. In this case, the turbocharger is excluded from the circuit by closing the conduits 22 and 44 controlled by the members 20 and 42. In this case, the inlet gas comes entirely from the pressure wave compressor 14 and therefore integrally from the conduit 10. This operating mode will be particularly suitable for low speeds.

  The computer can also control an operating mode in which the supercharging is provided by the single turbocharger 26. This time, it is the pressure wave compressor 14 which is short-circuited. For this, the air enters only through the conduit 12 and not by the conduit 10. In addition, the ducts 28 and 52 to bypass the turbocharger are closed. Finally, the duct 60 is also closed, so that all the exhaust gases pass through the duct 66.

  This mode of operation will be particularly suitable for high speeds.

  Mode of operation without supercharging The computer can still control a mode of operation of the engine in which no supercharging occurs. In this case, the pressure wave compressor 14 and the turbocharger are short-circuited as before.

  The various actuators of the system (associated with the supply of the engine in the cylinder head 8, the drive system 70 of the compressor 14, the members 20, 42 and 56 controlling the branches) are controlled by the computer according to the services expected in terms of approval performance and polluting emissions.

  Chillers 18 and 32 may be air coolers or water coolers, the latter may be part of the engine circuit or a specific circuit for cooling the supercharging.

  This engine can exist without providing charge cooler 18, 32 or by providing only one of these two coolers. In addition, it will be possible to delete some of the aforementioned derivations. Finally, it will also be possible to eliminate at least one of the two post-processing systems 50, 64.

  Second Embodiment A second embodiment of the engine according to the invention is illustrated in FIG. 2. Most of the main components of the engine of FIG. 1 are taken up and arranged in the same way, namely the pressure wave compressor. 14, the turbocharger 26, the cylinder head 8, the coolers and the after-treatment systems. Also preserved are the bypass ducts 28, 52 and 66 and the members 20, 42 which serve to control the first two. The control device 56 associated in the first embodiment with the bypass conduit 66 is removed.

  The engine 102 further comprises a valve system constituted in this case by valves that regulate the feed rates associated respectively with the pressure wave compressor 14 and the turbocharger 26. Each of the valves 80 thus provided may be electrical, mechanical or hydraulic control. These valves are controlled by the engine computer.

  In this embodiment, each of the fresh air supply ducts 10 and 12 is associated with one of the valves 80, the two ducts being connected to each other upstream of these valves and downstream of the filter. air.

  The upstream end of duct 66 communicates with duct 54 and its downstream end communicates with duct 62. Between these two ends, duct 66 carries a valve 80. Downstream of its junction with duct 66, duct 54 also carries a valve 80. It is the same for the conduit 62 upstream of its branch with the conduit 66.

  Again, the engine may have different modes of operation.

  Thus, in the operating mode in which the supercharging is carried out jointly by the pressure wave compressor 14 and the turbocharger 26, it will be provided that the conduit 12 is closed by the valve 80 while the conduit 28 is closed by the member 20. On the exhaust side, a portion of the gas will pass through the turbine 46 but it may be allowed that another portion of the gas passes through the conduit 52. Similarly, it will be ensured that at least a portion of the gas passes through the compressor 14 while allowing another portion of the gas passes through the bypass duct 66 controlled by the valve 80.

  In another mode of operation, the supercharging can be performed by the pressure wave compressor 14 alone. In this case, the conduit 12 is still closed by the valve 80 while the device 20 controls the integral passage of the intake gas through the bypass 28 associated with the compressor 24. On the exhaust side, the device 42 will control the passage of the entire gases in the bypass 52. Some of the gases may pass through the pressure wave compressor 14 while at most another part may be allowed to pass through the bypass 66.

  We can provide a mode of operation in which the supercharging is performed by the single turbocharger. This time, the duct 10 is closed by closing the associated valve 80. The bypass duct 28 is closed. Part of the exhaust gas will be allowed to pass through the conduit 52 while the portion of the conduit 54 extending downstream of the branch with the conduit 66 will be closed, all the exhaust gases bypassing the compressor wave pressure by the bypass 66.

  Finally, it will be possible to authorize another mode of operation of the engine in which no supercharging occurs. For this, the duct 10 will be closed and all the inlet gases will be forced to pass through the duct 28, so that these gases will bypass and the pressure wave compressor 14 and the compressor 24. On the exhaust side, the gases will pass in full by the conduit 52 and the bypass 66.

  2875849 II When the supercharging is carried out both by the pressure wave compressor and the turbocharger, the valves and taps can be arranged to allow this supercharging to take place by these two members arranged in series (so that they successively compress the same air fractions) or in parallel (so that they compress each of the air fractions not compressed by the other organ nor intended to be compressed) or else a mixed configuration in which the configurations are combined in series and in parallel.

  The positioning of the turbocharger 26 upstream of the pressure wave compressor 14 on the exhaust side is favorable to the proper operation of the latter for which is preferably adapted a smooth pressure signal input on the exhaust side. Thus, the turbine placed upstream of the compressor 14 on the exhaust side acts as a filter of the pressure signal seen by the compressor 14.

  The operation of the compressor 14 being based on the pressure ratios, it is less affected by the enthalpy drop caused by the passage of the exhaust gas through the turbine 46 than if the opposite configuration was provided. It is recalled that the enthalpy is critical for optimum operation of the turbine. It also avoids the problem that would occur in an engine using two turbochargers placed in series and in which the downstream turbine would probably be penalized by the low enthalpy of the gases coming from the upstream turbine. Furthermore, this lower sensitivity to enthalpy loss can be exploited by inserting a post-treatment system between the two exhaust energy recovery devices, as is the case for the after-treatment device 50 .

  Of course, we can bring to the invention many changes without departing from the scope thereof.

Claims (1)

12 CLAIMS   A vehicle engine comprising a pressure wave compressor (14), characterized in that it further comprises a turbocharger (26).   2. Engine according to the preceding claim, characterized in that the turbocharger (26) is interposed between the pressure wave compressor (14) and a cylinder head (8) of the engine by reference to an intake circuit (4) of the engine .   3. Engine according to any one of the preceding claims, characterized in that it is arranged to allow supercharging the engine jointly by means of the pressure wave compressor and the turbocharger.   4. Motor according to any one of the preceding claims, characterized in that it is arranged to allow to supercharge the engine by means of the single pressure wave compressor.   5. Motor according to any one of the preceding claims, characterized in that it is arranged to allow to supercharge the engine by means of the single turbocharger.   6. Motor according to any one of the preceding claims, characterized in that it is arranged to allow to operate the engine without supercharging.   7. Motor according to any one of the preceding claims, characterized in that it comprises a bypass duct (28) of the compressor (24) of the turbocharger and means (20) for controlling a flow of gas in the duct.   8. Motor according to any one of the preceding claims, characterized in that it comprises a bypass duct (52) of the turbine (46) of the turbocharger and means (42) for controlling a flow of gas in the duct.   9. Motor according to any one of the preceding claims, characterized in that it comprises a bypass duct (66) of the pressure wave compressor (14) on the exhaust side (6) and means (56; a circulation of gas in the conduit.   10. Engine according to any one of the preceding claims, characterized in that it comprises a bypass duct (12) of the pressure wave compressor (14) on the intake side and means (80) for controlling a circulation of gas in the conduit.   11. Engine according to any one of the preceding claims, characterized in that it comprises a cooler (18) interposed between the pressure wave compressor and the turbocharger with reference to an intake circuit.   12. Engine according to any one of the preceding claims, characterized in that it comprises a cooler (32) located on the intake side downstream of the pressure wave compressor and the turbocompressor.   13. Engine according to any one of the preceding claims, characterized in that it comprises an exhaust gas after-treatment system (50) interposed between the turbocharger and the pressure wave compressor.   14. Engine according to any one of the preceding claims, characterized in that it comprises an aftertreatment system (64) of exhaust gas located downstream of the turbocharger and the pressure wave compressor 15. Operating method of a vehicle engine, characterized in that the engine is supercharged by means of a pressure wave compressor (14) and a turbocharger (26).   16. Method according to the preceding claim, characterized in that said supercharging corresponding to a first mode of operation, it implements a second mode of operation in which the engine is supercharged by means of the single compressor pressure wave (14).   17. Method according to any one of claims 15 or 16, characterized in that said supercharging corresponding to a first mode of operation, it implements a third mode of operation in which the engine is supercharged by means of the single turbocharger (26). ).   18. A method according to any one of claims 15 to 17, characterized in that the supercharging corresponding to a first mode of operation, it implements a fourth mode of operation in which it does not perform supercharging.