FR2922960A1 - Blow-by gas reinjection system for e.g. petrol engine of motor vehicle, has exhaust gas recuperating circuit emerging from air intake circuit of engine, and blow-by gas recuperating circuit connected in exhaust gas recuperating circuit - Google Patents

Abstract

The system has an exhaust gas recuperating circuit (4) emerging from an air intake circuit (2) of an engine (10). A blow-by gas recuperating circuit (3) is connected in the exhaust gas recuperating circuit in downstream of a heat exchanger (41). The heat exchanger is placed on the exhaust gas recuperating circuit. An upstream pipe (42) of the recuperating circuit (4) and a settled gas transfer pipe (32) of the recuperating circuit (3) emerge from a common inlet case of the heat exchanger.

Description

BACKGROUND OF THE INVENTION The present invention relates to a crankcase gas reinjection system at the intake of a motor vehicle engine. It also relates to a heat exchanger for cooling exhaust gases in an exhaust gas recovery circuit.

The invention finds a particularly advantageous application in the field of recovery of crankcase gases of motor vehicle engines. In an internal combustion engine, gases are created in the crankcase of the engine, called crankcase gases or blow-by gases, coming from different sources: gas leakage at segments, from the combustion chamber to the piston volumes, -gas leakage at the bearings of the turbocharger or turbochargers, from the turbine and compressor bodies to the crankcase by the oil return, 15-gas leakage through the valve stem seals, from the intake and exhaust pipes to the cylinder head, - leakage of the oil pump gases, from the braking circuit to the cylinder head. The crankcase gases are therefore composed of: - combustion gases, mainly water, carbon dioxide and nitrogen, - unburned gases: air, fuel and nitrogen, - residual oil after the passage of the gases. through a settling chamber. In order to avoid the risks of escape to the outside and the discharge into the atmosphere of polluting hydrocarbons, as well as to keep the bottom of the crankcase in depression and to avoid a fire of the engine, the crankcase gases must be discharged through closed-loop recovery circuits operating by suction to the engine gas intake ducts for consumption in the combustion chamber. In a supercharged engine, the crankcase gases are reinjected preferably into the intake circuit upstream of the compressor.

It should also be noted that these gases, directly from the engine block, are extremely hot. It is also known that most self-ignition internal combustion engines, namely diesel engines, produce exhaust gases rich in nitrogen oxides, together NOx, whose environmental effects are particularly important. adverse. One known way to limit the production of nitrogen oxides is to recycle the exhaust gas. According to this technique, called EGR for Exhaust Gas Recirculation, at least a portion of the exhaust gas formed is taken from the exhaust line and mixed with the fresh intake air upstream of the inlet distributor. This mixture is then introduced into the combustion chamber of the engine. The presence of exhaust gas in the gas mixture has the effect of reducing the combustion temperature in the chamber and, since NOx formation is highly temperature dependent, it is understood that the recirculation of the exhaust gas helps to reduce the amount of nitrogen oxides formed. This effect increases with the amount of exhaust gas mixed with the intake air. To ensure proper cylinder filling and protection of the intake line components, the recovered exhaust gas is generally cooled using water exchangers designated EGRc for EGR cooler. This technology is also used for spark ignition engines, such as gasoline engines, to reduce full load consumption, knocking, and partial load pumping losses. In order to reinject clean and cold EGR gases into the intake circuit in the supercharged diesel engines, it is known to take these low pressure gases (LP) downstream of the turbine and preferably downstream of the particulate filter, cool them in a water exchanger, designated in this case by LP EGRc, and reinject them, like the crankcase gases, upstream of the compressor. This LP EGRc cooling process extends in the same way to gasoline engines, whether supercharged or not. The EGR gases reinjected at the inlet consist partly of water, in vapor or liquid form, and by acidic compounds. Finally, in order not to disturb the compression in the combustion chamber, it is preferable that the crankcase gases and the EGR gases form a mixture as homogeneous as possible. It can thus be noted that, in the current context, the reinjection of the crankcase gases requires a particular connecting device of the recovery circuit of these gases to the intake line, which requires additional parts and therefore leads to additional costs of manufacturing. Also, an object of the invention is to provide a crankcase gas reinjection system that would avoid the installation in the intake ducts specific connecting means of the crankcase recovery circuit. This object is achieved, in accordance with the invention, by means of a crankcase reinjection system at the intake of a motor vehicle engine, said system comprising an exhaust gas recovery circuit opening into a circuit engine air intake, remarkable in that said system comprises a crankcase recovery circuit opening into said exhaust gas recovery circuit. Thus, the result of the invention is that only one intake gas feed-back system is used, common to the crankcase gases and the EGR gases, by connecting the crankcase recovery circuit in the crankcase. EGR gas recovery circuit, the latter circuit reinjecting all of these gases in the engine intake line. It is therefore not necessary to provide on the intake circuit particular connecting pieces for the reinjection of the crankcase gases. Another advantage is the reduction of the acoustic effects induced by the connections of the recovery circuits in the intake line.

It should also be noted that, since the crankcase gases are directly injected into the EGR gas recovery circuit and not into the intake line, the mixing of these gases is more homogeneous with all the advantages that this represents at compression.

In the case of a supercharged air motor, the exhaust gas recovery circuit emerges from the exhaust line of the engine downstream of a turbine of a turbocharger and opens into an intake duct. air upstream of the compressor of said turbocharger. According to a first embodiment, the gas recovery circuit to the casing opens into the exhaust gas recovery circuit downstream of a heat exchanger placed on said exhaust gas recovery circuit. According to a second embodiment, the crankcase recovery circuit opens into the exhaust gas recovery circuit 15 upstream of a heat exchanger placed on said exhaust gas recovery circuit. According to a third embodiment, the crankcase recovery circuit opens into the exhaust gas recovery circuit in a heat exchanger placed on said exhaust gas recovery circuit. The last two embodiments have the advantage of cooling the crankcase gases which have been seen to come out very hot from the engine block. This ensures better protection of mechanical parts until admission. It will be generally appreciated that the EGR gases condensing in the EGRc exchanger produce acidic condensates which can reduce their performance and damage the materials that constitute it. In addition, these condensates may also end up in the intake line and damage the components therein such as valves, the supercharger or the charge air cooler (RAS) charged with fuel. increase the density of air at the intake of a turbocharged engine.

Likewise, the residual oil, water and fuel contained in the crankcase gas injected at the intake are deposited along the intake line by condensation or trapping. These deposits can disturb and damage parts, especially moving parts, and reduce the thermal efficiency of the EGRc exchanger and the RAS cooler and, as well as the acid condensates from the EGR gases, deteriorate the materials that compose them. Finally, it should also be noted that, in cold climatic conditions, the condensates produced by the EGR gases as well as the crankcase gas deposits can freeze and cause chiller breakage and engine choking. Also, the object of the invention is also to protect the heat exchanger EGRc as well as the components of the intake line, in particular the RAS cooler, against the condensation products, acid condensates of the EGR gases and / or deposits of the crankcase gases, which could affect their performance and integrity. This object is achieved by means of a system according to the invention comprising, on the exhaust gas recovery circuit, recovery means and means for discharging condensation products formed in said gas recovery circuit. 'exhaust. According to one embodiment, said recovery means are constituted by a low point of the exhaust gas recovery circuit and said exhaust means comprise a discharge duct extending between said low recovery point and the engine. According to another embodiment in which an EGRc heat exchanger is placed on said exhaust gas recovery circuit, said recovery means comprise a recovery receptacle arranged in an outlet box of said heat exchanger, said receptacle of recovery being able to recover by gravitation condensation products formed in the heat exchanger, and said discharge means comprise a discharge conduit communicating with said receptacle.

The condensation products formed in the heat exchanger are thus collected by gravitation in the recovery receptacle, located at the bottom of the exchanger, at a low point of the EGR gas recovery circuit. Then, the condensation products thus recovered can be discharged from the recovery receptacle to the intake manifold, for example, through the exhaust duct, parallel to the intake duct. In this way, the recovered condensation products are conveyed directly to the engine intake separately from the gaseous EGR gas / crankcase gas mixture, which can therefore be kept clean and cold ~ o until admission, without risk. to damage the parts located on the intake circuit. The transfer of condensation products along the exhaust duct is carried out by any means: gravity, depression by metering or venturi, etc. Advantageously, said evacuation means further comprise at least one condensation product discharge tube collected by gravitation in an inlet box of the heat exchanger. This effectively protects the cooling body from the heat exchanger because the condensation products collected in the inlet box can be evacuated by avoiding the cooling body, without passing through it and thus without damaging it. In particular, the invention provides that said evacuation tube opens into said recovery receptacle of the outlet box of the heat exchanger. The condensates from the inlet box are thus bundled together with the condensates from the outlet box into the same collection receptacle and vented to the inlet through a common vent. In the embodiment where the crankcase recovery circuit opens into the exhaust gas recovery circuit inside the heat exchanger, it is provided by the invention that an upstream duct of the exhaust gas recovery circuit and a conduit of the crankcase recovery circuit open into the same heat exchanger by two separate orifices, for example in a common inlet box of the heat exchanger. As a variant, an upstream duct of the exhaust gas recovery circuit and a duct of the casing gas recovery circuit open into separate inlet boxes of the heat exchanger. The invention also relates to a heat exchanger for cooling exhaust gases in an exhaust gas recovery circuit, which is remarkable in that said heat exchanger comprises an inlet box able to receive a duct of a fuel circuit. ~ o crankcase gas recovery. According to a first embodiment, said heat exchanger comprises an inlet box separate from the crankcase gas inlet box, adapted to receive an upstream duct of the exhaust gas recovery circuit. In this embodiment, each recovered gas type, crankcase gas or EGR gas, has its own inlet box. According to a second embodiment, said crankcase gas inlet box is also adapted to receive an upstream pipe of the exhaust gas recovery circuit. In this embodiment, the inlet box of the exchanger is common to both types of recovered gas. According to one embodiment of the recovery tube, said discharge tube is external to a cooling body of the exchanger. According to another embodiment, said evacuation tube is integrated with a cooling body of the exchanger, consisting of a bundle of tubes or plates. According to yet another embodiment, said evacuation tube is a tube at the bottom of a cooling body of the exchanger, consisting of a bundle of tubes. The following description with reference to the accompanying drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be achieved. Figure 1 is a diagram of a crankcase reinjection system according to the invention.

Figure 2 is a schematic diagram of a variant of the system of Figure 1 including a recovered exhaust gas heat exchanger. Figure 3 is a diagram of the system of Figure 2 applied to a supercharged engine.

Figure 4 is a diagram of the system of Figure 1 including a circuit for recovering and discharging condensation products. Figure 5 is a schematic of a variant of the system of Figure 4 including a recovered exhaust gas heat exchanger. Figure 6 is a schematic diagram of a heat exchanger comprising an inlet box common to recovered gases. Figure 7 is a diagram of the exchanger of Figure 6, the outlet box is provided with means for recovering and discharging condensation products. Figure 8 is a diagram of the exchanger of Figure 7, the inlet box is provided with means for discharging condensation products. Fig. 9 is a diagram of a heat exchanger comprising a separate inlet box for each type of recovered gas. Fig. 10 is a diagram of the exchanger of Fig. 9 including a separate cooling body for each type of recovered gas. FIG. 1 shows a motor vehicle engine 10 comprising an intake distributor 11, a combustion chamber 12 and an exhaust manifold 13. According to the EGR technique for reducing pollution by NOx nitrogen oxides, exhaust gases are taken from the exhaust line 1 and injected into the engine air intake circuit 2 via a circuit 4. EGR gas recovery opening into an inlet duct 21 downstream of the air filter 22. In order to limit the disadvantages mentioned above with respect to the formation of crankcase gas in the cylinder block of the engine 10, a circuit 3 for recovering these crankcase gases is provided, comprising a chamber 31 for decanting the contained oil. in these gases, and a conduit 32 for transferring gases thus decanted.

In order to avoid directly reinjecting the crankcase gases into the intake circuit 2 by means of a specific connection of the transfer duct 32 to the intake duct 21, it is preferred, in accordance with FIG. 32 for transfer of the crankcase recovery circuit 3 in the EGR gas recovery circuit 4. The crankcase gases are thus reinjected into the intake circuit 2 with the EGR gas, which has the further advantage of ensuring a good homogeneity of the gaseous mixture of the two types of recovered gas. In the case where the EGR gas recovery circuit 4 comprises a heat exchanger heat exchanger EGRc, as indicated in FIG. 2, the casing gas transfer duct 32 may open upstream or downstream of the exchanger 41, or in the exchanger itself. Situations where the outlet 32 of the transfer conduit is upstream or in the exchanger 41 can cool the crankcase gases that come out very hot engine block and may damage the parts in the circuit 2 of admission. In FIG. 2, the casing gas transfer duct 32 opens upstream of the heat exchanger 41. It could however lead into the exchanger itself, as shown in FIG. 6, which shows an exchanger 41 comprising a first orifice for receiving the duct 42 of the exhaust gas recovery circuit 4 and a second orifice receiving the conduit 32 of the crankcase recovery circuit 3. Here, the heat exchanger 41 includes an inlet box 411, a tube bundle cooling body 412, and an outlet box 413. It can be seen in FIG. 6 that the upstream gas recovery line EGR and the casing gas transfer duct 32 open into the same inlet box 411 which is then common to both types of recovered gas. FIG. 3 illustrates a particular embodiment in which the engine 10 operates by supercharging the intake air by means of a turbocharger whose turbine 15 is placed on the exhaust line 1, upstream of the filter 14 with particles. The turbine 15, driven in rotation by the flow of exhaust gas, in turn drives a compressor 23 placed on the inlet line 2 downstream of the air filter 22. The compression of the intake air induced by the rotational movement of the compressor 23 produces the desired supercharging. In the example of FIG. 3, the exhaust gases are recovered according to the low-pressure EGR technique (LP EGR) by sampling on the exhaust line 1 downstream of the turbine 15 and preferably downstream of the particulate filter 14. and reinjection in the inlet line 2 upstream of the compressor 23 after being cooled through the LP EGRc exchanger 41. It will be noted in FIG. 3 the presence of a supercharging air cooler 24 disposed on the inlet line 2 downstream of the compressor 23. This cooler 24 is intended to increase the density of the intake air at the inlet of the engine 10. FIGS. 4 and 5 relate to crankcase gas reinjection systems comprising, on the EGR gas recovery circuit 4, means 15 for recovering and discharging means to the engine 10 of condensation products formed in said exhaust gas recovery circuit. It will be recalled that these recovery and evacuation means have the advantage of eliminating from the gaseous mixture air / gas EGR / crankcase gas the condensation products, acid condensates and residual oil deposits in particular, which can affect the components of the 2 amission circuit and the quality of the gas mixture on admission. These various means will now be written in detail. In the embodiment of FIG. 4, in which the EGR gas recovery circuit 4 does not comprise an EGRc heat exchanger, the means for recovering the condensation products are constituted by a low point 43 of the recovery circuit 4. EGR gas, and the exhaust means comprise a discharge conduit 50 extending between the low point 43 and the inlet 11 of the engine 10. The injection of the condensation products through the conduit 50 30 evacuation is carried out by any means: metering or venturi for example. In the embodiment of FIG. 5, in which the EGR gas recovery circuit 4 comprises an EGRc heat exchanger 41, the means for recovering the condensation products comprise a recovery receptacle capable of recovering the condensation products formed in the heat exchanger. As indicated by the embodiments of the exchanger 41 shown in FIGS. 7 to 10, the recovery receptacle 414 is formed in the bottom of the outlet box 413 of the exchanger 41. condensation products, they comprise, according to the embodiments of Figures 7 to 10, a discharge pipe 50 connected to a discharge orifice 415 formed in the receptacle 414 and intended to transfer to the engine 10 the products of condensation collected in said recovery receptacle 414. An appropriate system by metering or venturi for example, not shown, provides the necessary depression for this transfer. In practice, the recovery receptacle 414 and the evacuation conduit 50 may be molded with the outlet box 413. According to FIG. 8, the evacuation means may also comprise a tube 417 for evacuating condensation products collected by gravitation in the inlet box 411 of the exchanger 41, in order to prevent the products of condensation present in the inlet box 411 does not penetrate inside the body 412 cooling the exchanger 20 and damage it. Advantageously, the evacuation tube 417 opens into the receptacle 414 for collecting the outlet box 413. Thus, the condensation products present in the inlet box 411 are grouped in the receptacle 414 with the products formed in the cooling body 412 for common evacuation to the motor 10 through the evacuation conduit 50. The discharge tube 417 may be molded with the inlet 411 and outlet 413. The cooling bodies 412 shown in FIGS. 6-10 are tube bundles cooled by a heat transfer medium which may be air outside or coolant. The fluid to be cooled, EGR gas and crankcase gas, circulates in the tubes 418 of the bundle.

In the example of Figure 8, the tube 417 discharge, rigid or flexible, is outside the beam 412 and bypasses. It could, however, be integrated into the tube bundle itself or be simply one of the tubes at the bottom of the bundle 412 of tubes. This can also be applied to plate heat exchanger technology. Figures 9 and 10 illustrate the situation where EGR gases and crankcase gases are cooled separately. In the case of Figure 9, the gases are cooled with the same cooling fluid. The gases enter the heat exchanger 41 through two separate inlet boxes, the upstream gas recovery line 42 EGR opening into a first inlet box 411a and the conduit 32 for transferring the casing gases opening into a second 411b input box separate from the first. Only the tube bundle 412 and the output box 413 are common.

In the case of Figure 10, the gases are cooled with different cooling fluids in different tube bundles. The upstream gas recovery line EGR 48 opens into the inlet box 411a of a first tube bundle 412a and the casing gas transfer conduit 32 opens into the inlet box 411b of a second bundle 412b. separate tubes from the first. Only the 413 output box is common.25

Claims (12)

1. Crankcase feed-back system at the intake of a motor vehicle engine (10), said system comprising an exhaust gas recovery circuit (4) opening into an intake circuit (2). engine air, characterized in that said system comprises a crankcase gas recovery circuit (3) opening into said exhaust gas recovery circuit (4). 2. System according to claim 1, wherein the circuit (3) for recovering crankcase gas flows into the exhaust gas recovery circuit (4) downstream of a heat exchanger (41) placed on said circuit. (4) exhaust gas recovery. 3. System according to claim 1, wherein the circuit (3) for recovering crankcase gas flows into the exhaust gas recovery circuit (4) upstream of a heat exchanger (41) placed on said circuit. (4) exhaust gas recovery. 4. System according to claim 1, wherein the circuit (3) for recovering crankcase gas flows into the exhaust gas recovery circuit (4) in a heat exchanger (41) placed on said circuit (4). exhaust gas recovery. 5. System according to any one of claims 1 to 4, wherein the exhaust gas recovery circuit (4) opens out of the exhaust line (1) of the engine (10) downstream of a turbine ( 15) of a turbocharger and opens into an air intake duct (21) upstream of a compressor (23) of a turbocharger. 6. System according to any one of claims 1 to 5, comprising, on the circuit (4) for recovering exhaust gas, means (43; 414) for recovery and means (50) for discharging products. condensation formed in said exhaust gas recovery circuit (4). 7. System according to claim 6, wherein said recovery means are constituted by a low point (43) of the exhaust gas recovery circuit (4) and wherein said exhaust means comprise a conduit (50) of evacuation extending between said low point (43) of recovery and the motor (10). 8. System according to claims 6 or 7, wherein said recovery means comprise a recovery receptacle (414) arranged in a box (413) outlet of said heat exchanger (41), said recovery receptacle 1s being able to recover by gravitation of the condensation products formed in the heat exchanger, and wherein said evacuation means comprises a discharge conduit (50) communicating with said receptacle (414). 20 9. System according to claim 8, wherein said evacuation means also comprise at least one tube (417) for discharging condensation products collected by gravitation in a box (411) inlet of the exchanger (41). heat. 25 10. System according to claim 9, wherein said evacuation tube (417) opens into the receptacle (414) for recovering the outlet box (413) of the heat exchanger (41). 11. System according to any one of claims 2 to 10, claims 5 to 10 to be taken in their connection to one of claims 2 to 4, wherein an upstream duct (42) of the circuit (4) of exhaust gas recovery and a conduit (32) of the circuit (3) recovering crankcase gas open into a box (411) common inlet of the heat exchanger (41). 12. System according to any one of claims 2 to 10, claims 5 to 10 to be taken in their connection to one of claims 2 to 4, wherein an upstream duct (42) of the circuit (4) recovery exhaust gas and a conduit (32) of the crankcase gas recovery circuit (3) open into separate inlet boxes (411a, 411b) of the heat exchanger (41). io