FR3032230A1 - EXHAUST GAS DEFLECTOR ASSEMBLY LOCATED OUT OF TURBOCOMPRESSOR TURBINE - Google Patents

Abstract

The invention relates mainly to an assembly (10) intended to be installed at the exhaust outlet of a motor vehicle engine comprising: - a discharge duct (15) associated with a discharge valve (16), and - a catalyst (25) comprising a body (26) and a catalytic bread (27) installed inside said body (26), characterized in that said assembly further comprises a deflector (30) of exhaust gas located in upstream of said catalytic bread (27), and in that said body (26) of said catalyst (25) and said baffle (30) are configured so as to be able to direct the exhaust gases from said discharge duct (15) into a zone (31) full restricted an outer surface of said catalytic bread (27).

Description

The present invention relates to an exhaust gas deflector assembly located at the outlet of a turbocharger turbine. SUMMARY OF THE INVENTION The present invention relates to an exhaust gas deflector assembly located at the outlet of a turbocharger turbine. SUMMARY OF THE INVENTION The invention finds a particularly advantageous application with automotive engine heat engines equipped with a turbocharger for their supercharging. To promote energy savings and minimize emissions of carbon dioxide and particulate pollutants, it tends to reduce the engine displacement while seeking to maintain a power at least identical to that of higher displacement engines ( principle of "downsizing" in English). In order to compensate for the loss of displacement, the reduced-displacement engines are generally supercharged by means of a turbocharger. In a conventional supercharged engine architecture, a turbocharger includes a compressor and a turbine. The compressor compresses the intake air to optimize the filling of the engine cylinders. For this purpose, the compressor is disposed on the intake duct upstream of the engine. The flow of the exhaust gas rotates the turbine disposed on the exhaust pipe, which then rotates the compressor through a coupling shaft. In normal operation of the turbocharger, it regulates the flow of exhaust gas passing through the turbine and therefore the power of the compressor via a discharge valve. This discharge valve allows a part of the exhaust gas to be deflected in a corresponding discharge duct which bypasses the turbine. EP1612385 teaches the use of a diffuser connected to the outlet of the turbine. An opening is arranged to allow the exhaust gas from the discharge conduit to mix with the exhaust gas from the turbocharger turbine. For this purpose, the wall of the diffuser located opposite the discharge valve forms a deflector, so that the gases from the discharge duct are distributed in an annular zone at a catalyst. Such a configuration however has the disadvantage of not allowing a rapid rise of the catalyst in idling operation of the engine when the majority of the exhaust gas is from the discharge duct. The invention aims to effectively remedy this disadvantage by proposing an assembly to be installed at the exhaust outlet of a motor vehicle engine comprising: - a wheel outlet of the turbocharger turbine, - a conduit discharge device associated with a discharge valve, and - a catalyst comprising a body and a catalytic bread installed inside said body, characterized in that said assembly further comprises an exhaust gas deflector located upstream of said catalytic bread , and in that said body of said catalyst and said baffle are configured to be able to direct the exhaust gases from said discharge duct into a narrow solid zone of an outer surface of said catalytic bread. [0007] Thus, in an idling operation of the heat engine, when the exhaust gases come mainly from the discharge duct, the invention makes it possible, by concentrating the heat flow of the exhaust gases in a reduced zone, to initiate quickly the chemical reaction of the catalyst especially during cold starts. In other words, the invention makes it possible to accelerate as far as possible the initiation of the chemical reaction by limiting the heat losses before the exhaust gases impact the catalytic bread. In one embodiment, said deflector is constituted by a thin sheet. According to one embodiment, the thickness of the sheet is between 4/10 and 8/10 "of millimeter. [0010] In one embodiment, said deflector is made of austenitic stainless steel material. to limit its thickness and thus its thermal inertia to a maximum [0011] According to one embodiment, said deflector is at least partially decoupled from said body of said catalyst so as to limit the transfer by thermal conduction between these two elements. welding areas between said baffle and said body of said catalyst are limited. [0013] In one embodiment, said body of said catalyst has a bent shape and has a recess located on the inner side of the bent shape. said deflector and said body of said catalyst are configured such that as the exhaust gas flow rate increases with the engine load, the exhaust az mainly from said outlet of said turbine wheel are distributed homogeneously on said outer surface of said catalytic bread. According to one embodiment, said discharge valve and said wheel outlet of the turbocharger turbine are positioned inside a housing of said turbine connected to said body of said catalyst. According to one embodiment, said baffle is controllable so as to adapt its curvature according to the operating conditions of the heat engine. The invention will be better understood from reading the following description and examining the figures that accompany it. These figures are given for illustrative purposes but not limited to the invention. Figure 1 is a longitudinal sectional view of an exhaust gas baffle assembly according to the present invention during idling operation of the engine; Figure 2 is a longitudinal sectional view of an exhaust gas baffle assembly according to the present invention during a full load operation of the engine. Identical elements, similar, or the like retain the same reference from one figure to another. FIG. 1 shows an assembly 10 according to the invention intended to be installed at the exhaust outlet comprising a wheel of the turbocharger turbine 11 located in a turbine casing 22 intended to be driven by the flow of the gas turbines. 'exhaust. This turbine wheel 11 then rotates the compressor (not shown) via a coupling shaft. In addition, a discharge duct 15 is associated with a discharge valve 16. The outlet 19 of the turbine wheel 11 and the discharge valve 16 are positioned inside the turbine casing 22 connected on the one hand to a central casing 12 of the turbocharger and secondly to a body 26 of a catalyst 25. The connection between the turbine casing 22 and the central casing 12 may for example be achieved by means of a clamping collar 23. enclosing two conical ends respectively belonging to the turbine casing 22 and the central casing 12. The connection between the turbine casing 22 and the body 26 may for example be achieved by means of a seal and a set of corresponding screws. In the turbine casing 22, the space 221 in which is positioned the wheel of the turbine 11 and the space 222 into which the outlet of the wheel of the turbine 11 and the discharge duct 15 are machined spaces in the mass of the housing 22. In normal operation of the turbocharger, the flow rate of the exhaust gas passing through the turbine and thus the power of the compressor by means of the discharge valve 16 is regulated. allows to deflect, when open, a portion of the exhaust gas in the corresponding discharge duct 15 which bypasses the turbine. The discharge valve 16 located inside the space 222 is pivotally mounted so as to be movable between a closed position closing the outlet of the discharge duct 15 and an open position clearing the outlet of the discharge duct 15, in order to allow the passage of the exhaust gases from the discharge duct 15. Furthermore, the catalyst 25 comprises the body 26 connected to the turbine casing 22 and a catalytic bread 27 installed inside the body 26. In addition, an exhaust gas baffle 30 is located upstream of catalytic bread 27. The terms "upstream" and "downstream" refer to the direction of flow of the exhaust gases from the wheel of the turbine 11 to catalytic bread 27. The body 26 of the catalyst 25 and the deflector 30 are configured so as to direct the exhaust gases from the discharge duct 15 into a narrow full area 31 of the catalytic bread 27, and this without l The exhaust gases from the discharge duct 15 lick the wall of the body 26 of the catalyst 25 at a junction between this wall and an outer periphery of the catalytic bread 27. For a restricted solid zone, a solid zone 31 is meant. a few square centimeters, preferably between 2 and 5 square centimeters, which has the overall shape of a closed disc. This zone is preferably located near the center of the outer surface of catalytic bread 27 facing the inlet of the exhaust gases inside the body 26. [0026] For this purpose, the body 26 of the catalyst 25 presents a bent shape and has a recess 34 located on the inner side of the bent shape, that is to say on the side facing the center of the radii or radii of curvature defining the bent shape of the body 26 in the portion at the level of the junction between the body 26 and the turbine casing 22. This recess 34 prevents the exhaust gas from the discharge duct 15 to impact a zone 41 in the form of ring portion located at the inner side of the bent shape (on the left in Figure 1). Furthermore, the deflector 30 is curved in the same direction as the body 26 of bent shape. The curvature is such that it prevents the gases coming from the discharge duct 15 from impacting the catalytic bread 27 in the zone 42 in the form of a ring portion situated on the external side of the bent shape (on the right in FIG. 1). orienting these gases towards the restricted zone 31. Thus, in an idling operation of the heat engine, when the exhaust gas mainly come from the discharge duct 15 due to the opening of the discharge valve 16 (see arrow F1) and that the flow of gas from the outlet 19 of the wheel of the turbine 11 is limited (see arrow F2), the gases shown are concentrated in the restricted area 31 of the outer surface of the catalytic bread 27. This allows to initiate quickly the chemical reaction catalyst 25 especially during cold starts, by limiting the heat losses before the exhaust gases impact the catalytic bread 27. The deflector 30 is constituted for example by a thin sheet of stainless steel.

By fine, is meant a sheet of thickness between 4/10 and 8 / 10th of a millimeter, preferably the deflector 30 is made of a stainless steel material of the austenitic type, which makes it possible to limit its thickness and thus its maximum thermal inertia [0030] In addition, the deflector 30 is advantageously at least partially decoupled from the body 26 of the catalyst 25 so as to limit heat transfer by conduction as much as possible.For this purpose, the welding zones between the deflector 30 and the body 26 of the catalyst 25 are limited, so that two consecutive welds are separated from each other by a free space, thus limiting the contact area between the baffle 30 and the body 26 of the catalyst 25. [0031] Moreover, , as shown in FIG. 2, in a full load operation of the heat engine, the exhaust gas flow rate increases with the engine load and generates turbulence (see F2 arrows). The configuration of the deflector 30 and of the body 26 of the catalyst 25 then makes it possible to distribute the exhaust gases coming mainly from the outlet 19 of the turbine wheel 11 of the turbocharger homogeneously on the surface of the catalytic bread 27 in a extended zone 36. In this case, the flow of exhaust gas leaving the discharge duct 15 is moderate because of the partially open position of the discharge valve 16 (cf. arrows F1). Thus, the temperature field upstream of catalytic bread 27 becomes more homogeneous, which avoids generating hot spots that would be detrimental to the holding of catalytic bread 27. [0033] In other words, the deflector 30 and the body 26 of the catalyst 25 are configured so as to evenly distribute the exhaust gas over an extended area 36 to obtain a homogeneity of the temperature field of the catalytic bread 27 in full load operating phase, and contrary to in order to concentrate the exhaust gases in the restricted zone 31 in idle phase to accelerate the chemical reactions in the catalyst 25. In this embodiment, the fixed curvature of the deflector 30 is a curvature determined so as to allow the concentration of the gas in the restricted area 31 of the low-load catalytic bread, while avoiding the disturbance of the flow of exhaust gas at full load. In an alternative embodiment, the deflector 30 is controllable so as to adapt its curvature depending on the operating conditions of the engine. In this case, it is possible to increase the curvature of the deflector 30 inward, along the arrow F3, so as to further reduce the area of the zone 31 during a phase of operation at idle. During operation at full load, the curvature is increased so that the deflector 30 returns to its initial position to avoid the pressure losses of the exhaust gas.

Claims (7)

1. An assembly (10) intended to be installed at the exhaust outlet of a motor vehicle engine comprising: - a wheel outlet (19) of the turbocharger turbine (11), - a discharge duct ( 15) associated with a discharge valve (16), and - a catalyst (25) comprising a body (26) and a catalytic bread (27) installed inside said body (26), characterized in that said assembly comprises in addition, an exhaust gas deflector (30) upstream of said catalytic bread (27), and in that said body (26) of said catalyst (25) and said deflector (30) are configured so as to be able to orient the exhaust gas from said discharge duct (15) in a narrow zone (31) constrained by an outer surface of said catalytic bread (27). 2. An assembly according to claim 1, characterized in that said deflector (30) is constituted by a thin sheet. 3 assembly according to claim 2, characterized in that the thickness of the sheet is between 4/10 and 8/10 "mm. 4. An assembly according to any one of claims 1 to 3, characterized in that said baffle (30) is made of an austenitic stainless steel material. 5. An assembly according to any one of claims 1 to 4, characterized in that said baffle (30) is at least partially decoupled from said body (26) of said catalyst (25) so as to limit heat transfer by thermal conduction between these two elements (26, 30). 6. The assembly of claim 5, characterized in that welded areas between said baffle (30) and said body (26) of said catalyst (25) are limited. 7. An assembly according to any one of claims 1 to 6, characterized in that said body (26) of said catalyst (25) has a bent shape and comprises a recess (34) located on the inner side of the bent form.8. An assembly according to any one of claims 1 to 7, characterized in that said deflector (30) and said body (26) of said catalyst (25) are configured such that when a flow of exhaust gas increases with a load of engine, the exhaust gases mainly from said outlet (19) of said turbine wheel (11) are distributed homogeneously on said outer surface of said catalytic bread (27). 9. An assembly according to any one of claims 1 to 8, characterized in that said discharge valve (16) and said wheel outlet (19) of the turbine (11) turbocharger are positioned within a casing (22) of said turbine connected to said body (26) of said catalyst (25). 10. An assembly according to any one of claims 1 to 9, characterized in that said deflector (30) is controllable so as to adapt its curvature according to operating conditions of the engine.