FR2941014A1 - Exhaust gas recirculation device for petrol engine, has recirculation circuit deriving part of exhaust gas from exhaust line and returning derived gas to manifold, and heating system arranged upstream of mixing element to heat derived gas - Google Patents

Abstract

The device has a recirculation circuit (22) deriving a part of exhaust gas from an exhaust line (18) of an internal combustion engine (10) and returning the derived exhaust gas to a pressurized air intake manifold (14) of the engine. A heating system (28) is arranged upstream of a mixing element (24) for heating the derived exhaust gas. The recirculation circuit is connected with the heating system. The mixing element mixes the derived exhaust gas with fresh air entering into an intake line (20) of the engine. Independent claims are also included for the following: (1) an internal combustion engine assembly comprising an air cooler (2) a method for recirculation of exhaust gas for an internal combustion engine.

Description

The present invention relates to a device and a method for recirculating exhaust gas. BACKGROUND OF THE INVENTION It also relates to an engine assembly provided with such a device.

The invention applies in particular to gasoline or diesel internal combustion engines equipped with an exhaust gas recirculation circuit in which part of the exhaust gas is derived from an exhaust line of the exhaust gas. engine and is returned to an engine intake manifold. This part of the exhaust is called recycled.

In some engines equipped with turbochargers, the recycled gases are derived from the exhaust line upstream of the turbine of the turbocharger and returned to the intake manifold downstream of the compressor of the turbocharger after a possible cooling. The exhaust gas recirculation circuit is then referred to as high pressure and high temperature circuit.

In other engines equipped with turbochargers, the recycled gases are derived from the exhaust line downstream of the turbine of the turbocharger, and even downstream of a particulate filter or a set of pollution control disposed in out of the turbine, and carried back into the intake manifold upstream of the turbocharger compressor. The exhaust gas recirculation circuit is then qualified as a low pressure and low temperature circuit.

This recirculation high pressure or low pressure of the exhaust gas is intended to reduce the amount of nitrogen oxides (NOx) released into the atmosphere by the engine. Indeed, these nitrogen oxides are produced by the combination of nitrogen and oxygen present in the intake air under the effect of a very high temperature. The recirculation system decreases, during certain operating phases, the amount of oxygen available in the cylinder by introducing into the intake manifold a certain amount of oxygen-poor exhaust gas thus replacing the fresh oxidizing air. In this way, this system can very significantly reduce NOx emissions. The purpose of exhaust gas recirculation is also to reduce the amount of carbon dioxide (CO2) released into the atmosphere by optimizing fuel consumption.

This makes it possible to meet in particular the constraints of existing and forthcoming European regulations concerning the limitation of pollutant emissions. [0007] Exhaust gas recirculation engines are also generally provided with air coolers arranged in the recirculation circuit or in the intake line.

But when starting at room temperature, it is sometimes necessary to obtain recycled exhaust gases less cold than in current use.

Thus, exhaust gas recirculation is generally not used during cold starts of the engine. Indeed, this would have the effect of creating instabilities of the engine and thus to generate a driving inconvenience, or to cause misfires on ignition.

To remedy at least partially this drawback, the document published under the number FR 2 836 700 provides a bypass circuit of a supercharged air cooler, or the provision of heating resistors in the intake line of the engine to heat the incoming air through the air filter.

However, the bypass circuit of the supercharged air cooler is not sufficient in all cold start situations and the provision of heating elements in the engine intake line to heat the fresh air entering either.

To better take advantage of the benefits in terms of depollution that provides an exhaust gas recirculation circuit, it may be desired to provide a device that allows to overcome the aforementioned problems and constraints. The invention therefore relates to an exhaust gas recirculation device for an internal combustion engine, comprising a recirculation circuit in which a part of the exhaust gas is derived from an engine exhaust line. and is brought into an intake manifold of the engine, characterized in that it comprises a heating system of said portion of the exhaust gas derivative.

Thus, by heating the exhaust gas returned to the intake manifold, and no longer only by heating the incoming fresh air or by a bypass of a cooling system, the elevation of the Recycled gas temperature is made possible and exhaust gas recirculation can be used in many cold engine starting situations.

Optionally, the heating system is disposed upstream of a mixing element of said part of the exhaust gas derived with air entering an intake line of the engine. Also optionally, the heating system is disposed in the recirculation circuit.

The invention also relates to an internal combustion engine assembly comprising a motor, an exhaust line of the engine, an intake manifold of the engine and an exhaust gas recirculation device as defined above.

[0017] Optionally, the engine is a spark ignition engine, commonly called a gasoline engine.

Also optionally, the engine assembly further comprises an air cooler disposed upstream of the intake manifold and a bypass circuit of the air cooler.

[0o19] The subject of the invention is also an exhaust gas recirculation method for an internal combustion engine, comprising a step of diversifying, with the aid of a recirculation circuit, a part of the gases of exhaust from an exhaust line of the engine to an intake manifold of the engine, characterized in that it comprises a step of heating said part of the exhaust gas derivative.

Optionally, the heating step is performed before said portion of the exhaust gas derivative is mixed with incoming air through an engine intake line.

Also optionally, the heating step is performed when said portion of the exhaust gas flows into the recirculation circuit.

Also optionally, the step of heating said part of the exhaust gas is carried out during a cold start of the engine.

The invention will be better understood with the aid of the description which follows, given solely by way of example and with reference to the accompanying drawings in which:

FIG. 1 schematically represents an exhaust gas recirculation engine assembly according to a first embodiment of the invention, and

• Figure 2 schematically shows an exhaust gas recirculation engine assembly according to a second embodiment of the invention.

The internal combustion engine assembly shown in FIG. 1 comprises an internal combustion engine 10 with four cylinders 121, 122, 123, 124.

This engine is for example a gasoline engine, but the invention also applies to a diesel engine. This engine further comprises a pressurized air intake manifold 14 and an exhaust manifold 16 supplying exhaust gas to an exhaust line 18 of the engine.

The intake manifold 14 is supplied with combustion gas by a line 20 for supplying fresh air from outside, generally called the intake line. The engine assembly of Figure 1 further comprises a recirculation circuit 22 in which a portion of the exhaust gas is derived from the exhaust line 18 of the engine 10 and is returned to the intake manifold 14 It may also comprise a supercharging device comprising a turbocharger not shown in this schematic representation and the recirculation circuit 22 may be at high temperature and high pressure or low temperature and low pressure depending on the places where it is connected to the lines. exhaust 18 and intake 20.

In the inlet line 20, the gases recycled by the recirculation circuit 22 are mixed with incoming fresh air by means of a mixing element 24 which can be simply the place of connection of the circuit recirculation 22 at the inlet line 20.

In a conventional manner, the flow rate of the gases flowing in this recirculation circuit 22, and therefore the composition of the fresh air / recycled gas mixture, is further regulated by a valve 26 arranged in the recirculation circuit 22 upstream. of the mixing element 24.

According to the invention, the engine assembly comprises a system 28 for heating the part of the exhaust gas which is deflected by the recirculation circuit 22 to the intake manifold 14, that is to say say a heating system of recycled gases. This heating system 28 may for example comprise one or more heating resistors.

To heat the recycled gases more efficiently, this heating system 28 may be arranged upstream of the mixing element 24, so as not to heat the incoming fresh air in addition: it can also also be heated independently of the recycled gases, upstream of the mixing element 24 in the intake line 20, as suggested by the document FR 2 836 700. In Figure 1, the heating system is more precisely disposed in the recirculation circuit 22 upstream of the flow control valve 26.

An exhaust gas recirculation method implemented by the motor assembly described above thus comprises the following steps: • Derivation El, using the recirculation circuit 22, a part of the gases of exhaust from the exhaust line 18 of the engine 10 to the intake manifold 14, and

• heating E2 of said part of the exhaust gas derivative. This method may, as indicated above, be carried out during a cold start of the engine 10.

In addition, the heating step E2 can be carried out before the recycled gases are mixed with the fresh air entering at the mixing element 24, and even more precisely, as is the case. in FIG. 1, when these recycled gases circulate in the recirculation circuit 22.

In the embodiment shown in Figure 2, the inlet line 20 may comprise, downstream of the mixing element 24, a supercharged air cooler 30. In addition, a bypass valve 32 is arranged between the mixing element 24 and the supercharged air cooler 30 to direct the air at the outlet of the mixing element 24 to a bypass circuit 34 of the supercharged air cooler 30. Thus, when the recycled gases are heated by means of the heating system 28, the bypass valve can be actuated to direct the combustion gas to the bypass circuit 34.

As in the previous embodiment, the engine assembly shown in Figure 2 may further comprise a supercharging device comprising a turbocharger not shown in this schematic representation.

It is clear that the recirculation device described above allows the use of recycled gases for the internal combustion of the engine 10, including in cold start situations. This allows an optimization of the fuel consumption and thus an optimization of the CO2 emission. This also allows a reduction of polluting NOx emissions. Finally, this makes it possible to avoid the instabilities of the engine 10 during the cold start phases while advantageously using the recirculation device. Note also that the invention is not limited to the embodiments described above. It will be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching that has just been disclosed. In the following claims, the terms used are not to be construed as limiting the claims to the embodiments set forth in this specification, but should be interpreted to include all the equivalents that the claims are intended to cover because of their formulation and whose prediction is within the reach of the person skilled in the art by applying his general knowledge to the implementation of the teaching which has just been disclosed to him.

Claims (10)

REVENDICATIONS1. An exhaust gas recirculation device for an internal combustion engine (10), comprising a recirculation circuit (22) in which a part of the exhaust gas is derived from an exhaust line (18) of the engine (10). ) and is brought into an intake manifold (14) of the engine, characterized in that it comprises a system (28) for heating said portion of the derived exhaust gas. 2. Recirculation device according to claim 1, wherein the heating system (28) is disposed upstream of a member (24) for mixing said part of the exhaust gas derived with air entering a line. intake (20) of the engine (10). 3. Recirculation device according to claim 1 or claim 2, wherein the heating system (28) is disposed in the recirculation circuit (22). An internal combustion engine assembly comprising a motor (10), an exhaust line (18) of the engine (10), an intake manifold (14) of the engine (10) and a gas recirculation device (10). exhaust system according to any one of claims 1 to 3. 5. Engine assembly according to claim 4, wherein the engine (10) is a gasoline engine. An engine assembly according to claim 4 or claim 5, further comprising an air cooler (30) disposed upstream of the intake manifold (14) and a circuit (34) for bypassing said air cooler ( 30). 7. Process for the recirculation of exhaust gas for an internal combustion engine (10), comprising a step (E1) of bypassing, using a recirculation circuit (22), a portion of the gases of exhaust from an exhaust line (18) of the engine (10) to an intake manifold (14) of the engine (10), characterized in that it comprises a step (E2) for heating said part exhaust gas derived. The recirculation method according to claim 7, wherein the heating step (E2) is performed before said portion of the derived exhaust gas is mixed with incoming air through an inlet line (20). the engine (10). The recirculation method of claim 7 or claim 8, wherein the heating step (E2) is performed when said portion of the derived exhaust gas flows into the recirculation circuit (22). 10. Recirculation method according to any one of claims 7 to 9, wherein the step of heating (E2) of said portion of the exhaust gas derivative is performed during a cold start of the engine (10).