EGR condensate siphon

Description

Technical field of the invention

[0001] The present invention relates to a thermal engine for a motor vehicle.

[0002] The present invention relates to a combustion engine burnt gas exhaust circuit.

[0003] The present invention relates more particularly to a device for managing and removing condensates, in particular acid condensates, in a heat engine exhaust line. State of the art

[0004] As is well known, a motor vehicle's combustion engine is equipped with pollution control systems to reduce the release of pollutants outside the vehicle. These pollution control systems are located in the engine's exhaust system and include a catalyst or a particulate filter. The exhaust system of an engine refers to the entire circuit of burnt gases from the engine via the exhaust valves.

[0005] To reduce the emission of pollutants generated by combustion, it is known to return burnt gases to the exhaust, i.e. downstream of combustion in the cylinders, towards the intake ducts. There are thus different types of recirculated burnt gases taken from the exhaust line: high-pressure recirculated gases taken from the exhaust system upstream according to the direction of flow of the gases from pollution control devices such as a catalyst or nitrogen oxide (NOx) trap. Generally, the high-pressure recirculated burnt gases are taken directly from an exhaust manifold attached to an exhaust face of the cylinder head, on the lateral side opposite the intake face. The high-pressure recirculated gases are then sent to the intake ducts or into the intake manifold. low-pressure recirculated burnt gases taken from the exhaust system and in a known manner after a pollution control device. Said low-pressure recirculated gases are returned in a known manner to the intake system upstream of the compressor. They are then mixed with the fresh air captured at the front of the vehicle.

[0006] The low-pressure recirculated burnt gases are therefore taken downstream of an exhaust system and returned to the engine intake. In a known manner, the recirculated gases are cooled before being mixed with fresh air captured from the front of the vehicle, for example. The mixture is then capable of being compressed by passing a compressor.

[0007] Condensate may form in the low-pressure exhaust gas recirculation circuit, particularly when the engine is stopped. This condensate may consist of water, oil, and toxic and corrosive waste. It may then be transported in liquid form to the compressor during engine start-up, particularly into the compressor wheel, and damage the wheel through corrosion.

[0008] Publication EP2375047-A2 thus presents a device for reducing corrosive compounds in an exhaust gas condensate of an internal combustion engine, in which the exhaust gases of the internal combustion engine are returned to the internal combustion engine via an exhaust gas return duct consisting of an exhaust gas cooler and at least one exhaust gas recirculation duct. The device relates to a recirculation circuit for high-pressure recirculated gases which are taken from an exhaust manifold to be reintroduced into the engine intake. The device also comprises a unit for neutralizing the corrosive compounds of the exhaust gas condensate arranged downstream of the burnt gas recirculation circuit and through which the exhaust gases pass. The device can be complex and adds additional weight to the engine.

[0009] The aim of the invention is to remedy these problems and one of the objects of the invention is a simple device for managing and removing condensates formed when the engine is stopped, downstream of a pollution control device arranged on a heat engine exhaust line without altering the circulation of recirculated gases.

[0010] Publication EP3059434-A1 and DE102010048466-A1 discloses a low-pressure recirculated flue gas circuit of a motor vehicle heat engine comprising a pollution control device aeraulically connected downstream to an exhaust outlet pipe and to a flue gas cooler connected to a flue gas recirculation circuit, the cooler comprising a condensate removal circuit opening at a first end located downstream of the cooler and at a second end into the exhaust outlet pipe and comprising a condensate retention tank connected to the exhaust outlet pipe by a condensate ejection pipe. A means for controlling the ejection pipe is provided, which is in the form of a valve.

[0011] Publication US2008 / 028757-A1 discloses a similar low pressure recirculated flue gas circuit, but without a reservoir and means of controlling the ejection duct.

[0012] Publication DE102010048466 -A1 also discloses a similar low pressure recirculated flue gas circuit, but without a means of controlling the ejector duct. Presentation of the invention

[0013] The present invention relates more particularly to a low pressure recirculated burnt gas circuit of a motor vehicle heat engine comprising: a pollution control device connected aeraulically downstream to an exhaust outlet pipe and to a burnt gas cooler connected to a burnt gas recirculation circuit, ,said cooler comprising a condensate removal circuit opening at a first end into a downstream end of the cooler and at a second end into the exhaust outlet pipe, said removal circuit further comprising a condensate retention tank and a condensate ejection conduit connected to the retention tank and opening into the exhaust outlet pipe.

[0014] The main characteristic of the circuit according to the invention is that the condensate retention tank comprises a means for controlling the opening of the ejection duct, said control means comprising two successive circulation branches with a vertical axis and opposite direction.

[0015] Advantageously, a circuit for managing and removing the generated condensates opens through a first end into a downstream end of the cooler which is the zone of formation of said condensates, to allow the collection, removal and then routing of the condensates contained in the recirculated gases towards a second end opening into the exhaust outlet pipe to be discharged to the outside and thus avoid pollution of a compressor wheel towards which the recirculated gases are directed after their passage through the cooler. The condensates are thus removed without access to the engine, in particular to an air compressor wheel of the engine.

[0016] According to other characteristics of the invention, the condensate removal circuit comprises condensate collection means arranged in the cooler casing at the downstream end of said casing.

[0017] Advantageously, the suppression circuit comprises means for collecting condensates from the recirculated gases. Said means are arranged in the cooler casing and at a downstream end of said cooler to allow optimal collection of said condensates and reduced bulk. the collection means comprise a collection wall arranged at a downstream end of the cooling device and towards which the recirculated gases are directed, and a collection pocket arranged at the foot of said collection wall.

[0018] Advantageously, the condensate collection means comprise at least one collection wall arranged at a downstream end of the cooling device and towards which the recirculated gases are directed. Said recirculated gases abut against the collection wall to allow separation and collection of the pollutants, the condensates are able to flow by gravity along the collection wall towards the collection pocket arranged at the foot of said wall. the collection means comprise a deflector arranged at the downstream end of said cooler to conceal the outlet of the suppression circuit in the cooler casing.

[0019] Advantageously, the condensate collection means comprise a deflector intended to hide the outlet of the suppression circuit in the cooler casing and more particularly the recirculated gas collection pocket so as not to disturb the operation of the cooler and the passage of burnt gases. the collection means comprise an impactor arranged in the cooler housing.

[0020] Advantageously, an impactor in the cooler housing, particularly at the outlet, makes it possible to capture the maximum amount of liquid present in the cooled exhaust gas. The condensate removal circuit includes a condensate retention tank.

[0021] Advantageously, the control circuit includes a retention tank to retain the condensates, particularly in the event of engine shutdown, and to prevent condensates from rising into the cooler housing. The condensate tank is located below the cooler housing.

[0022] Advantageously, the retention tank is arranged below the cooler casing, i.e. at a lower level of said casing along a vertical axis Z, to allow simple evacuation by gravity of the condensates collected in said casing. the suppression circuit comprises a condensate ejection conduit connected to the retention tank opening into the exhaust outlet pipe.

[0023] Advantageously, the condensate tank is connected to the exhaust outlet pipe by an ejection duct, which allows the tank to be optimally arranged and the condensate path to be reduced. the retention tank includes a means for controlling the opening of the ejection duct.

[0024] Advantageously, the retention tank comprises a means for controlling the opening of the condensate ejection duct to prevent continuous discharge of said condensates which could cause the gases recirculated by the control circuit and therefore short-circuit the EGR burnt gas recirculation circuit. the control means comprises a condensate circulation conduit comprising two successive circulation branches with a vertical axis and opposite direction.

[0025] Advantageously, the control means can be formed of two successive circulation branches of parallel axes, in particular vertical, and of opposite directions capable of preventing the passage of recirculated gases through the suppression circuit. the circulation duct has a permanently submerged part capable of preventing the passage of gases.

[0026] Advantageously, the circulation duct has a part permanently submerged and filled with condensates preventing the passage of recirculated burnt gases through said duct. The control means is designed to have gas flow resistances greater than the gas flow resistances through the burnt gas outlet of the cooler casing.

[0027] Advantageously, the control means has dimensional characteristics generating resistances to the circulation of gases, here the recirculated burnt gases, greater than those of the burnt gas recirculation circuit, to favor the recirculated burnt gases passing through the burnt gas recirculation circuit known as the EGR circuit instead of the condensate removal circuit. the control means comprises a piloted opening valve capable of closing / opening the outlet condensate in the exhaust outlet pipe.

[0028] Advantageously, the control means comprises an opening valve which can be controlled by a control actuator, to control the passage of condensates in the exhaust outlet pipe and to prevent said condensates from flowing back into the tank. The valve is a backpressure valve. Brief description of the figures

[0029] Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments of the invention given as non-limiting examples and represented in the appended drawings, in which: [ Fig. 1 ] is a schematic view of the engine with the elements of the gas circuit. [ Fig. 2 ] is a schematic sectional view of the low-pressure recirculated gas circuit successively comprising a pollution control device and a recirculated gas cooler with the direction of circulation of said gases. [ Fig. 3 ] is a schematic sectional view of the low-pressure recirculated gas circuit successively comprising a pollution control device and a recirculated gas cooler with a condensate removal circuit according to one embodiment. [ Fig. 4 ] is a schematic sectional view of the low-pressure recirculated gas circuit successively comprising a pollution control device and a recirculated gas cooler with a condensate removal circuit according to another embodiment.

[0030] In the following description, like reference numerals designate like parts or parts having similar functions.

[0031] The terms up / down relate to a vertical axis orthogonal to a horizontal plane which may be the plane of the vehicle (not shown) passing through the axles of the vehicle wheels.

[0032] Similarly, the terms upstream / downstream relate to the direction of flow of burnt gases in the gas recirculation circuit.

[0033] In a known manner, a motor vehicle powertrain such as for the invention may comprise a heat engine with accessories intended to improve the performance of said heat engine or to ensure the operation of the engine; said accessories comprise for example a turbocharger with a turbine stage and a compressor stage, a gas cooler, a water / gas heat exchanger.

[0034] According to the figure 1 , the thermal engine 10 of the motor vehicle (not shown) comprises a circuit of recirculated burnt gases 11 taken from the exhaust 14 of the engine to return them to the intake 13 of the engine 10 in order to reduce the discharge of pollutants. Two recirculated gas circuits can be seen: a first circuit of burnt gases 15 called high pressure which are taken from the exhaust manifold of the engine and brought directly to the intake of said engine, a second circuit of recirculated gases 16 called low pressure which are taken from or downstream of a pollution control device 12. Said pollution control device may be a particulate filter or a catalyst or a Nox trap for nitrogen oxide. The burnt gases then pass through a gas cooler which may be a water / gas heat exchanger to then be directed successively towards a fresh air intake duct 17 in which they are mixed with fresh air from a capture generally from the front of the vehicle, a compressor 18, a water charge air cooler 19 known as Water CAC in English, before reaching the intake face of the engine and the intake ducts (not shown) leading to the cylinders of said engine.

[0035] According to the figure 2 , the pollution control device 12 comprises a pollution control casing 20 surrounding a pollution control block 21. The pollution control device comprises two downstream connections: a first connection with a cooler 22 of the burnt gases which will then be directed into the burnt gas recirculation circuit, and a second connection with an exhaust outlet pipe 30 through which the burnt gases are discharged from the engine.

[0036] The recirculated gases are at high temperature. They pass through the depollution cake to remove their toxicity and then enter the cooler 22 to lower their temperature before mixing with fresh air. The cooler 22 is generally a water / gas heat exchanger and comprises a cooler casing 23 surrounding cylindrical tubes 24 immersed in a volume of water 25 supplied by an inlet nozzle 26 and an outlet nozzle 27, said two nozzles being connected to a water-based cooling circuit (not shown) of the engine.

[0037] The recirculated gases pass through the cylindrical tubes 24 to give part of their heat to the water. The gases strike at a downstream end 31 a wall 28 of a funnel leading to the outlet mouth 29 of the cooler 22.

[0038] When the engine is stopped and while it is stopped, essentially liquid condensates composed of water with possibly corrosive components and oil can be deposited in the casing 23 of the cooler 22 essentially at its downstream end 31. Said condensates can then, when the engine is started, be carried towards the compressor and pollute the compressor wheel with harmful and corrosive components, which can lead to engine failures.

[0039] According to a preferred embodiment of the invention shown in figures 3 And 4, the cooler 22 comprises a condensate control and removal circuit 40 40c for collecting, storing, and removing said condensates. The control circuit 40 comprises means for collecting the condensates. Said means comprise the wall 28 at the downstream end which has an inclined surface and a collection pocket 33 arranged at the bottom of the collection wall 28. Said collection pocket may be for example a recess hollowed out in the lower wall 34 of the cooler casing 23.

[0040] As represented in figures 3 And 4 , said collection means may comprise an impactor 22 i formed by a grid, arranged inside the casing 23 of the cooler and covering the outlet 22 av of the cooler 22. Said impactor makes it possible to capture the maximum amount of liquid present in the cooled exhaust gas.

[0041] According to the figure 3 , the collection means may comprise a deflector 35. Preferably, the deflector 35 extends from the lower wall 34. It may be formed by a sheet made of the same material as the cooler casing 22. Said deflector 35 makes it possible to hide the collection pocket 33 for the recirculated gases and in particular the outlet 40 d of the condensate removal circuit in the casing 23. Said recirculated gases are thus directed at the outlet of the cylindrical tubes towards the collection wall at the downstream end, and above the collection pocket 33.

[0042] The control circuit 40 also comprises a condensate retention tank 41. Said tank is preferably arranged to bear against the wall of the casing 20 of the decontamination device 12 and below the casing 23 of the cooler 22, that is to say at a lower level of said casing 23 along a vertical axis Z, to allow simple evacuation by gravity of the condensates collected in the casing of the cooler.

[0043] A storage conduit 42 connects the casing 23 of the cooler 22 to the retention tank 41. More precisely, the storage conduit opens at a first end into the collection pocket 33 of the casing 23 and at the second opposite end into the tank 41. The axis of the storage conduit 42 is substantially vertical or oblique relative to the vertical axis Z and the retention tank 41 is thus arranged at the lowest point of the casing 23 and of the storage conduit 42. The condensates can thus flow by gravity from the collection pocket 33 to the retention tank 41.

[0044] According to the figures 3 And 4 , the suppression circuit 40 comprises a condensate ejection conduit 43 connected to the retention tank 41 and opening into the exhaust outlet conduit 30.

[0045] Advantageously, the condensate removal circuit 40 comprises a means 50 for controlling the opening of the ejection duct 43.

[0046] Said control means 50 is capable of allowing the liquid condensates to pass into the exhaust outlet pipe 30 while preventing the circulation of burnt gases downstream of the cooler towards said same outlet pipe.

[0047] The control means 50 comprises a condensate circulation conduit 44 comprising two successive branches 45, 46 connected to each other with a substantially vertical axis and opposite direction. The two branches 45, 46 form a U-shaped circulation. The two branches 45, 46 form a siphon 47.

[0048] In operation, the circulation duct 44 has a lower part, in particular the hollow of the U, permanently immersed in the condensates and capable of preventing the passage of recirculated burnt gases.

[0049] The control means 50 is shaped to have resistances to the circulation of gases greater than the resistances to the circulation of gases through the burnt gas recirculation circuit. The control means has dimensional characteristics generating resistances to the circulation of gases, here the recirculated burnt gases, greater than those of the burnt gas recirculation circuit, to favor the recirculated burnt gases passing through the burnt gas recirculation circuit called the EGR circuit instead of the condensate removal circuit.

[0050] According to an exemplary embodiment in figure 3 , the ejection or overflow conduit 43 passes through the retention tank 41 from a first lower end and overflows from said tank at the opposite end by an overflow height 48 which is defined according to the environment and the installation of the system. The control means 50 comprises a cylindrical cap 49 which also overflows from the retention tank 41 and covers the ejection conduit 43. The cap has a larger diameter and is pushed into the same retention tank. The ejection conduit 43 and the cap 49 are substantially coaxial. The cap 49 surrounds the ejection conduit 43 over a determined length in the tank. The cap does not extend over the entire height 41 h of the tank and reveals a liquid passage with a height defining the siphon height 47.The first circulation branch 45 is delimited between the reservoir and the cap, the second circulation branch 46 is delimited between the cap and the ejection duct and has a thickness 46 e. The cap delimits a gas flow control chamber whose height is defined between the upper end of the ejection duct and the cap. Said chamber height may be of the order of a few mm, between 2 and 10 mm.

[0051] The siphon height can be less than 5 mm. The thickness between the ejection tube and the cap can be between 3 and 10 mm. The dimensions of siphon height 47 and second branch thickness 46 e allow the flow of liquid condensates to be regulated.

[0052] Preferably, the ejection duct 43 is made of stainless steel of the same type as the EGR gas circulation ducts.

[0053] The dimensional characteristics of the siphon 47 are defined according to the engines so that the counter pressure generated in the gas phase is higher than the pressure in the cooler.

[0054] According to another embodiment shown in figure 4, the control means 50 is formed by the storage tube 42 which plunges into the retention tank in such a way that the axis of the storage tube is substantially parallel to a vertical edge of the tank. In simple terms, the tank is cylindrical and the storage tube is arranged so that the retention tank 43 and the storage tube 42 are coaxial. The height of the storage tube 42 inside the tank is inside the height of said retention tank leaving a space at the bottom of the tank 43. The two branches for circulation of the liquid condensates are therefore formed by the storage tube then the space between the retention tank and the storage tube. The characteristics of the siphon will be determined in a manner analogous to the first embodiment described above. Preferably, the retention tank comprises a radial opening connected with the ejection tube for the passage of overflow condensates.

[0055] Preferably, a controlled opening valve 51 is arranged in the ejection tube, and is capable of closing / opening the condensate outlet in the exhaust outlet pipe. The valve is a back pressure valve and is added at the outlet of the tank.

[0056] This valve can be controlled via an actuator 52 to control the passage of condensates in the exhaust outlet pipe and prevent said condensates from flowing back into the tank.

[0057] The operation of the control circuit is carried out as follows: During shutdown and also during engine shutdown, the recirculated gases generate condensates which are collected on the inclined wall 28 at the downstream end of the cooler 22. The condensates in liquid form flow down this inclined wall to the collection pocket 33 passing below the deflector 35. The condensates enter the storage conduit 42 to be directed to the retention tank 41 by gravity.

[0058] In the event of overflow in the retention tank, the liquid condensates are ejected through the ejection pipe 43.

[0059] The control means 50 comprising the siphon 47 allows the evacuation of liquid condensates while preserving the circulation of the burnt gases recirculated towards the engine intake.

[0060] The objective has been achieved: the low-pressure recirculated burnt gas circuit includes a circuit for removing condensates formed in the cooler housing when the engine is stopped.

[0061] The said control circuit makes it easy to store condensates when the engine is stopped and to remove them easily.

Claims

1. Low-pressure recirculated flue gas circuit (16) for an internal combustion engine of a motor vehicle, comprising: - a pollution control device (12) connected downstream by means of aeraulics to an exhaust outlet pipe (30) and to - a flue gas cooler (22) connected to a flue gas recirculation circuit, the cooler (22) comprising a condensate removal circuit (40) opening at a first end into a downstream end (31) of the cooler and at a second end into the exhaust outlet pipe (30), the removal circuit (40) further comprising a condensate retention reservoir (41) and a condensate ejection pipe connected to the retention reservoir (41) and opening into the exhaust outlet pipe, CHARACTERIZED IN THAT the condensate retention reservoir (41) comprises a means (50) for controlling the opening of the ejection pipe, the control means (50) comprising a condensate circulation pipe (44) comprising two successive circulation arms (45, 46) having a vertical axis and opposite directions.

2. Flue gas circuit (16) according to claim 1, characterized in that the condensate removal circuit (40) comprises condensate collection means arranged in the casing (23) of the cooler (22) at the downstream end (31) of the casing.

3. Flue gas circuit (16) according to claim 2, characterized in that the collection means comprise a collection wall (28) arranged at a downstream end (31) of the cooler (22) and toward which the recirculated gases are directed, and a collection pocket (33) arranged at the foot of the collection wall.

4. Flue gas circuit (16) according to claim 2, characterized in that the collection means comprise a deflector (35) arranged at the downstream end (31) of the cooler to conceal the outlet (40d) of the removal circuit in the cooler casing (23).

5. Flue gas circuit (16) according to any of claims 2 to 4, characterized in that the collection means comprise an impactor (22i) arranged in the cooler casing (23).

6. Flue gas circuit (16) according to any of the preceding claims, characterized in that the condensate retention reservoir (41) is arranged below the cooler casing (23) along a vertical Z axis.

7. Flue gas circuit (16) according to any of the preceding claims, characterized in that the condensate circulation pipe (44) has a permanently immersed portion capable of preventing the passage of recirculated flue gases.

8. Flue gas circuit (16) according to any of the preceding claims, characterized in that the control means (50) comprises an operated opening valve (51) capable of closing / opening the condensate outlet in the exhaust outlet pipe (30).