FR2889246A1 - Internal combustion engine for motor vehicle, has exhaust circuit comprising pulse type exhaust gas collector favoring formation of pressure waves generated by exhaust puff and fluid flow of exhaust gas in recirculating circuit - Google Patents

Abstract

The engine has an air intake circuit (16) having a fresh gas intake collector (22) connected to a supplying orifice of a combustion chamber (12). An exhaust circuit (18) has a pulse type exhaust gas collector (28) connected to an exhaust orifice of the chamber. An exhaust gas recirculating circuit (20) of a drive train is connected to the collectors by its respective input and output and comprises a closing circuit to close the circuit (20), where the collector (28) favors the formation of pressure waves generated by exhaust puff and a fluid flow of the exhaust gas in the circuit (20).

Description

"Powertrain with means for

  The invention relates to a power train comprising means for increasing the recirculation rate of the exhaust gas.

  The present invention relates more particularly to a power unit of a motor vehicle, of the type comprising: - an air intake circuit comprising a fresh gas intake manifold connected to a supply port of at least one chamber to engine combustion; an exhaust circuit comprising a flue gas exhaust manifold connected to an exhaust port of at least one combustion chamber of the engine; an exhaust gas recirculation circuit (EGR) of the engine connected via its inlet to the exhaust manifold and connected via its outlet to the intake manifold for fresh gases and means for controlling the flow of gases in the exhaust gas circuit; recirculation.

  Internal combustion engines produce and emit toxic pollutants in the exhaust gases, in particular nitrogen oxides or NOx.

  However, the anti-pollution standards applicable to motor vehicles impose on manufacturers maximum quantities of pollutants released into the atmosphere, which must be lower and lower.

  Exhaust gas recirculation, also called EGR for "Exhaust Gas Recirculation" in English terminology, consists of injecting or reinjecting a portion of the flue gases into a cylinder combustion chamber.

  Exhaust gas recirculation is one of the solutions to achieve a significant reduction in discharges and to comply with anti-pollution standards.

  Indeed, it is known that the recirculation of at least a portion of the exhaust gas to the intake of the internal combustion engine can lower the combustion temperature, and therefore reduce the amount of nitrogen oxides or NOx emitted by the engine.

  More specifically, the formation reaction of the nitrogen oxides is favored by a high temperature because the nitrogen oxides are formed mainly in the areas of the combustion chamber of the cylinder in which the richness of the air-fuel mixture is close to the stoichiometric ratio.

  The exhaust gas recirculation is therefore based on the thermodynamic properties of the exhaust gases, which, containing a large fraction of carbon dioxide, have a higher heat capacity than the other species that are predominantly present in the atmospheric air, such as nitrogen and oxygen.

  Thus, during the release of energy caused by the combustion of the fuel, the carbon dioxide absorbs a greater amount of energy than that absorbed by the other species mainly present in the fresh air. As a result, the temperature of the gases in the combustion chamber is reduced, which greatly reduces the amount of nitrogen oxides produced.

  However, the quantity of gas discharged into the exhaust system decreases as the engine load decreases, so that at a certain load level the exhaust gases circulate little in the gas recirculation circuit. exhaust, as well as this small amount of exhaust gas does not allow a turbine of a supercharging machine, such as a turbo-compressor, to be effectively driven in rotation by the exhaust gas.

  This finding is all the more true that the exhaust gas recirculation circuits are often connected to the exhaust system depending on the space available, often at the expense of a good flow of gas in the EGR circuit.

  It is known to use methods to improve the flow of exhaust gas in the exhaust system, in particular for feeding a supercharging machine.

  For example, the document BE-A-759,780 proposes to modulate the pressure waves coming from combustion chambers of the engine by making nozzles on the exhaust circuit for feeding a supercharging machine.

  Other known processes such as the "Pulse" exhaust manifold make it possible, by the shape and arrangement of their ducts, to improve the flow of the exhaust puffs and the propagation of the pressure waves produced by and in the exhaust.

  The invention aims to improve the circulation and increase the amount of gas in the exhaust gas recirculation circuit.

  For this purpose, the invention proposes an internal combustion engine, in particular for a motor vehicle, of the type mentioned above, characterized in that the exhaust circuit comprises means promoting the formation of pressure waves and / or promoting a fluid flow. exhaust gases to improve their flow in the exhaust gas recirculation circuit.

  According to other features of the invention: the exhaust manifold is of the so-called "Pulse" type which comprises a main duct connected to secondary ducts oriented in the direction of the gas flow and connected to the exhaust ports the combustion chambers of the engine, the axis of the outlet section of each secondary duct and the axis of the main duct form an acute angle, and the main duct and the inlet of the exhaust gas recirculation circuit are connected in the extension and in the direction of the flow of the exhaust gases; - The powertrain comprises a turbo-compressor whose turbine is connected to the exhaust system of the engine downstream of said means promoting the formation of pressure waves and / or promoting a fluid flow.

  Other features and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: FIG. 1 is a diagram in plan view representing a powertrain comprising a gas recirculation circuit according to the state of the art; - Figure 2 is a diagram similar to that of Figure 1 showing the exhaust gas recirculation circuit and an exhaust manifold of the "Pulse" type according to a first embodiment of the invention; FIG. 3 is a schematic perspective view of an exhaust manifold of the "Pulse" type of FIG. 1; - Figure 4 is a diagram similar to that of Figure 2 showing a powertrain according to the invention further comprising a turbocharger supercharger; FIG. 5 is a detailed view of a "Pulse" type collector of FIG. 3; FIG. 6 is a detailed view of a "Pulse" type collector of FIG. 3 according to an embodiment comprising a supercharging machine; In order to facilitate the understanding of the description, as well as the claims, use will be made of an upstream orientation, downstream corresponding to the direction of the flow of gases in the different circuits, from left to right in accordance with FIG.

  Figures 1 and 2 show schematically a combustion engine 10, here four cylinders C1, C2, C3 and C4 each delimiting a combustion chamber 12.

  In known manner, such a combustion chamber 12 s is delimited, axially along the axis of the cylinder formed in the engine block 14, in its lower part by the upper face of a piston (not shown) which slides in the cylinder- ci in a reciprocating reciprocating movement, and in its upper part by the underside of a cylinder head (not shown) of the engine 10.

  The engine 10 comprises, downstream upstream, an air intake circuit 16 and or air-fuel mixture, an exhaust circuit 18, and a recirculation circuit 20 of the exhaust gas.

  The air intake circuit 16 comprises an intake manifold 22 which supplies each combustion chamber 12 of the engine 10.

  The intake manifold 22 comprises a main duct 24, or plenum, which divides into a plurality of secondary ducts 26. The secondary ducts 26 are connected to the combustion chambers 12.

  The exhaust circuit 18 makes it possible to evacuate to an exhaust duct 27 the flue gases in the combustion chambers 12.

  The circuit comprises for this purpose an exhaust manifold 28 which comprises a main duct 30, or plenum, and secondary ducts 32 which are connected between the combustion chambers 12 and the main duct 30.

  The exhaust gas recirculation circuit 20 comprises at least one recirculation duct 34 and a recirculation valve 36.

  The recirculation duct 34 comprises an exhaust end section 37 which is connected to the intake circuit 16 and an intake end section 35 which is connected to the exhaust circuit 18.

  The valve 36 makes it possible to open and close the exhaust gas recirculation circuit in order to supply or not the intake circuit 16 with exhaust gas and to regulate the flow rate or the quantity of the recirculated gases.

  Thus arranged, the exhaust gas recirculation circuit 20 makes it possible to circulate, in a controlled manner, a part of the exhaust gas of the exhaust circuit 18 towards the intake circuit 16.

  FIG. 2 represents a combustion engine as previously described but comprising an exhaust gas manifold 28 and a recirculation circuit 20 according to the invention.

  The exhaust manifold 28 is of the type called "Pulse". It comprises essentially the same elements as the exhaust manifold 18 of Figure 1, namely the main duct 30 and the secondary ducts 32. The main duct 30 has the main axis of flow axis A. Each secondary duct 32 comprises a main axis of flow, the axis B, and an outlet end section 33. The outlet end section 33 has an approximate shape of a quarter circle and is connected to the main duct 30 of the collector The axis B of the outlet end section 33 and the axis A of the main duct 30 form an acute angle α, as shown in FIG.

  The intake end section 35 of the recirculation duct 34 is connected in the extension and at the downstream end of the main duct 30 of the exhaust manifold 28.

  The flue gases are expelled from the combustion chambers 12 by generating so-called exhaust bursts. A collector of the "Pulse" type promotes the formation of pressure waves generated by the exhaust puffs. It also allows the exhaust to lose less speed than with a conventional collector.

  The invention makes it possible to improve the circulation of the exhaust gases in the exhaust gas recirculation circuit 20 benefiting from the advantages of the "Pulse" type collector.

  According to another embodiment illustrated in FIG. 4, the engine is supercharged by means of a turbo-compressor 50.

  The turbo-compressor 50 comprises a compressor 52 which pressurizes the atmospheric intake air and a turbine 54 which is fed with gases from the exhaust duct 27 and which supplies the mechanical energy necessary for driving the engine. compressor 52.

  The fresh atmospheric air is conveyed to the compressor via a supply line 57 of the compressor 52 by previously passing through an air filter 58 so as to prevent the dust of the atmospheric air from entering the compressor 52 .

  A discharge circuit 60 is connected upstream of the turbine 54 to the conduit 27 via a bypass duct 62 and is connected to the exhaust duct 66 via a duct 64.

  The discharge circuit 60 comprises a discharge valve 68 through which any surplus of exhaust gas can be derived from the duct 27 to the exhaust duct 66 without passing through the turbine 54.

  The compression of the atmospheric air in the compressor 52 causes an increase in its temperature. For this reason, the intake duct 24 which connects the outlet of the compressor 52 to the intake manifold 22 preferably comprises an air-cooling device 70 in order to limit the increase in the temperature of the gases injected into the inlet manifold. the combustion chambers 12.

  The outlet of the exhaust manifold 28 here comprises a first end section 55 connected to the exhaust duct 27 and a second end section 56 connected to the intake end section 35 of the recirculation duct 34.

  According to this embodiment, the exhaust manifold 28 of the "Pulse" type benefits the exhaust gas recirculation circuit 20 and the turbo-compressor 50.

  For this purpose, the orientations and conformations of the connection sections 55 and 56 of the outlet of the "Pulse" collector are such that the sections are oriented in the direction of the gas flow and that their respective axes form an acute angle 8, as shown in Figure 6.

Claims (3)

  An internal combustion engine (10), in particular for a motor vehicle, of the type comprising: an air intake circuit (16) comprising an intake manifold (22) for fresh gases connected to a supply orifice; at least one combustion chamber (12) of the engine (10); an exhaust circuit (18) comprising an exhaust gas manifold (28) connected to an exhaust port of at least one combustion chamber (12) of the engine (10); - a recirculation circuit (20) of the exhaust gas from the engine (10) connected via its inlet to the exhaust manifold (28) and connected via its outlet to the intake manifold (22) fresh gases and comprising an organ closing (36) the recirculation circuit (20); characterized in that the exhaust circuit (18) comprises means (28) for promoting the formation of pressure waves and / or promoting a fluid flow of the exhaust gases to improve their flow in the recirculation circuit (20) exhaust gas.   2. Combustion engine according to claim 1, characterized in that the exhaust manifold (28) is of the type called "Pulse" which comprises a main duct (30) connected to secondary ducts (32) oriented in the direction of the flow of gases and connected to the exhaust ports of the combustion chambers (12) of the engine (10), in that the axis (B) of the outlet section (33) of each secondary duct (32) and the axis (A) of the main duct (30) form an acute angle (a), and in that the main duct (30) and the inlet of the recirculation circuit (20) of the exhaust gases are connected in the extension and in the direction of the flow of the exhaust gas. io   3. Combustion engine according to claims 1 and 2, characterized in that the engine comprises a turbo-compressor (50) whose turbine (54) is connected to the exhaust circuit (18) of the engine (10) downstream of said means (28) promoting the formation of pressure waves and / or promoting a fluid flow.