FR2900439A3 - Reducing agent e.g. hydrocarbon, injecting device for e.g. oil engine, of vehicle, has injector placed close to catalyst, and injection channel with axis oriented opposite to mixer obstacle - Google Patents

Abstract

The device has an injector (2) connected to a reducing agent source and formed by a reducing agent injection channel (3) emerging into an exhaust duct (1). The injector is placed close to a catalyst (T). The channel has a privileged axis (CD) inclined of an angle (theta) with respect to a privileged axis (AB) of the duct. An activation unit activates a jet of reducing agent from the source via the channel. The axis of the channel is oriented opposite to a mixer obstacle (5) e.g. turbine`s vane, and is inclined of a specific angle (alpha) with respect to a privileged plane of the obstacle.

Description

Injection device with a mixing obstacle in the duct

  TECHNICAL FIELD OF THE INVENTION The present invention relates, in the field of internal combustion engines, in particular of the Diesel type, to a device for injecting a reducing agent (for example, hydrocarbon) into an exhaust duct forming part of an antipollution device for flue gases. The invention relates more particularly to an injection device disposed in an exhaust duct making it possible to promote the heat exchange between the burnt gases and the injected reducing agent and to improve the homogeneity of their mixture, while reducing the necessary time to achieve this, especially during cold start. BACKGROUND OF THE INVENTION The constraints due to the standards relating to the levels of pollutant emissions related to the operation of internal combustion engines, in particular Diesel engines, are becoming more and more severe, in particular as regards the emissions of particles, of nitrogen oxide, NO, sulfur oxide, SOx, etc. In a known manner, to reduce the level of pollutant emissions, vehicle manufacturers use pollution control devices comprising filtering elements, for example particulate filters, NO traps, installed downstream of the engine output in the line of pollution. exhaust. The main difficulty relating to the proper functioning of these filter elements lies in the need to periodically regenerate the pollution that is deposited therein. In order to solve this problem, catalysts, for example oxidation catalysts, placed in the exhaust duct downstream of the filter element with respect to the flow direction of the burnt gases are generally used. The idea is to cause chemical reactions on the catalyst (eg, oxidation) using the hydrocarbons present in the flue gases. These chemical reactions have the effect of regenerating the filter element (for example, by providing the heat necessary to burn the particles).

  However, the low level of hydrocarbons present in the flue gases during normal operation of the internal combustion engine, in particular Diesel, does not make it possible to obtain on the catalyst the chemical reaction yield necessary to produce a satisfactory regeneration of the filter element. .

  To circumvent this difficulty, the burned gases are enriched with hydrocarbon by modifying the engine settings, for example: by reducing the air flow at the intake, by staggering the phases and / or the duration of the injections of the fuel into the chambers of combustion, by reducing the rate of recirculation of the exhaust gas at the intake, said EGR (English Exhaust Gas Recirculation) etc. These known solutions, however, are unsatisfactory because they cause many problems, for example, a dilution of the fuel in the engine oil thereby reducing the reliability of the latter. In addition, these solutions generate overconsumption of fuel, which ultimately reduces engine performance. Furthermore, the engine settings are delicate and long to perform without guaranteeing optimal variations in the richness of burnt gas / hydrocarbon mixture depending on the actual fouling state of the pollution control devices.

  To circumvent these difficulties, another known approach consists in injecting a reducing agent (for example, a hydrocarbon such as the fuel used by the engine, the alcohol, etc.) directly into the exhaust duct using an injector specifically dedicated to this task and placed upstream of the catalyst with respect to the direction of the flue gas flow.

  As a complementarity note that the reducing agent may be of a different chemical nature from that of a hydrocarbon. This is the case, for example, antipollution devices using the technology of catalytic reduction of nitrogen oxides known as SCR (English Selective Catalytic Reduction) which require the injection of urea in the exhaust pipe upstream catalyst. In this case, the presence of the injector in the exhaust pipe then becomes unavoidable because the urea is incompatible with the fuel and can not therefore pass through the engine.

  In known manner, the injection of the reducing agent, for example, in a liquid or atomized state, operates perpendicularly to the preferred axis (for example, the axis of symmetry) of the exhaust duct. The penetrating liquid or atomized jet, for example under pressure, inside the exhaust duct does not have sufficient time to mix with the flue gases. While passing through the exhaust duct, the jet then touches the internal wall of the exhaust duct which is opposite the injector by creating a liquid film which flows towards the catalyst. The burned gas / reducing agent mixture downstream of the injector and upstream of the catalyst is therefore not homogeneous. The intensity of the chemical reaction then differs from one part to another of the catalyst. This results in a very heterogeneous distribution of the gradient, for example thermal, within the catalyst. This causes insufficient regeneration of the filter element and overconsumption of the reducing agent. Similarly, the stresses due to the heterogeneous thermal gradient cause accelerated aging of the catalyst and / or the filter element, or even their disintegration, for example, by cracking. Other injection geometries treating the blast gas / reducing agent mixing problem are described in the European patent application EP 1 314 864 A1. The injector has at its end a nozzle for generating the reducing agent jet. in the exhaust duct. This end is extended towards the inside of the exhaust duct by a diffuser. The latter is provided with an injection channel whose preferred axis, for example, the axis of symmetry, is inclined or even parallel with respect to the preferred axis of the exhaust duct, which improves the gas mixture. burned / reducing agent (column 8, lines 26-28, column 10, lines 2-4). In addition, the diffuser may be equipped with means increasing the speed and / or the swirling of the outgoing jet thus further promoting the mixing of the reducing agent with the flue gases (column 9, lines 5-6). In all the embodiments disclosed in EP 1 314 864 A1 the injection takes place in the exhaust duct downstream of the injector with respect to the direction of flow of the flue gases (column 7, lines 56). -58, column 8, lines 13-15, 23-25, 53-56, column 9, lines 37-43). The device according to EP 1 314 864 A1 has several disadvantages. For example, the projection of the vector of the flow velocity of the burned gases on the preferred axis of the exhaust duct and the projection of the jet velocity vector on this preferred axis are collinear, which reduces correspondingly their resultant. Clearly, the impact of the injected jet in the direction of flow is damped at least partially by the flow velocity. Gas burned / reducing agent exchanges are reduced accordingly. All the other parameters remaining constant, this: decreases the homogeneity of the mixture at comparable time (which means that the technical problem posed is not really solved) or requires a longer time to mix the flue gas with the agent reducing agent with comparable homogeneity of mixing. However, for reasons of space, any elongation of the exhaust line or any distance from the catalyst injector to increase the distance traveled by the mixture (and therefore the flue gas / reducing agent exchange time) n ' is not possible. In addition, the device according to EP 1 314 864 A1 does not completely eliminate the risk of impact by the jet of the inner wall of the exhaust duct. The device according to EP 1 314 864 A1 does not exclude, a priori, the problems detailed above following the creation of a liquid film on the inner wall of the exhaust duct flowing towards the catalyst.

  Another injection geometry that addresses the problem of blast gas / reducing agent mixing is described in Japanese Patent JP 2005 214100. The reducing agent injector is implanted in an elbow of the exhaust line. The injector has at its end a diffuser to generate the reducing agent stream. This diffuser is extended towards the inside of the elbow. The diffuser is provided with an injection channel whose preferred axis, for example, the axis of symmetry of the diffuser, coincides with the preferred axis of the exhaust duct downstream of the elbow with respect to the direction of the flue gas flow.

  As in the case of the device according to EP 1 314 864 A1 mentioned above, the injection of the reducing agent takes place in the exhaust duct towards the laval of the injector with respect to the direction of flow of the flue gases. To improve the mixing of the reducing agent with the flue gases, the device according to JP 2005 214100 has a grid in the exhaust duct downstream of the elbow with the injector relative to the direction of the gas flow. burned. The grid is oriented perpendicular to the preferred axis of the exhaust duct downstream of the bend with the injector and closes it completely, so as to direct the flow of the flue gases in the direction of injection of reducing agent by the injector. The gate is disposed in the exhaust duct downstream of the injector and is oriented perpendicularly to the preferred axis of the injector. As a result, the reducing agent jet is oriented perpendicularly to the grid. As a result, the actual area of contact between the gate and the liquid phase of the jet (HC) used to catch drops of the liquid phase of the jet (HC), is reduced to only connection nodes of the grid. In other words, the grid appears as a substantially two-dimensional object whose ability to trap the reducing agent is limited. Therefore, at least a portion of the liquid phase of the reducing agent stream passes through the grid without mixing with the flue gases. Improvement of the mixture of the reducing agent with the flue gases obtained with the aid of the device according to JP 2005 214100, therefore remains insufficient. In addition, the gate can not a priori not capture all the reducing agent diffused by the jet, it is not excluded that at least a portion of the liquid phase of the jet touches a wall of the exhaust duct (especially if the exhaust duct has a bend downstream of the grate with respect to the direction of flow of the flue gases) by creating a liquid film of reducing agent detrimental to the proper operation of the catalyst. Finally, most of the polluting emissions are formed during a relatively short period, called the cold operating period, from the start of the engine until the temperature of the engine exceeds a predetermined temperature threshold, for example 90 C, to reach the so-called normal operating temperature of the engine. However, the antipollution devices become operational only from a certain predetermined temperature, for example about 300 C. Thus, during the period of operation of the cold engine, with an air / fuel mixture, at the intake of the engine, rich in fuel generating a massive rejection of pollutant emissions, the antipollution devices of the exhaust line are inefficient or even completely inoperative. The devices according to EP 1 314 864 A1 and JP 2005 214100 do not meet the particular needs of the antipollution device installed in the exhaust duct during cold start. They do not provide any relevant education that could reduce pollutant emissions in the exhaust line during the cold engine operating period and suggest no solution to this effect. The problem of reducing polluting emissions during the period of operation of the cold engine is dealt with in European patent EP 0 594 794 B1. The proposed solution concerns an internal combustion engine with injection and spark ignition. The idea is to reduce the richness of the air / fuel mixture at the intake of the engine by preheating the fuel using a heating element arranged in an intake duct upstream of an intake valve (column 1, lines 26-40, column 2, lines 44-46). The heating element is in the form of an enamelled metal plate, on which is printed a current-conducting material (column 2, lines 56-58, column 3, lines 1-2). This solution has several disadvantages. Indeed, the device according to EP 0 594 794 B1 acts upstream of the engine and provides no relevant teaching with respect to antipollution devices installed in the exhaust line downstream of the engine that can reduce the pollutant emissions in the flue gases . In addition, the case of a diesel engine is not treated or even mentioned in EP 0 594 794 B1. GENERAL DESCRIPTION OF THE INVENTION The invention relates more particularly to an injection device arranged in an exhaust duct making it possible to promote the heat exchange between the burnt gases and the injected reducing agent and to improve the homogeneity of their mixing, while reducing the time required to achieve this, especially during cold start.

  For this purpose, the invention relates to an injection device for injecting a reducing agent into a flue gas flow, on the one hand, formed in an exhaust duct downstream of an internal combustion engine and, on the other hand, on the other hand, directed from the output of the engine to the outlet of the exhaust line, comprising at least one reducing agent source, at least one injector connected to the reducing agent source and formed by at least one channel of injection of the reducing agent opening into the exhaust duct, the preferred axis of the injection channel being inclined at an angle θ relative to the preferred axis of the exhaust duct, at least one activation means a reducing agent jet from the reducing agent source via the injection channel, characterized in that the injection device comprises a mixing obstacle disposed in the exhaust duct downstream of the injector by ratio to the flow direction of the flue gas at a temperature of predetermined istance of the injection channel e1: in that the preferred axis of the injection channel is oriented towards the mixing obstacle and is inclined at an angle with respect to the preferred plane of the mixing obstacle such that 0 < at. <90 or 90 <a <180. According to another feature, the preferred plane of the mixing obstacle is inclined or perpendicular with respect to the preferred axis of the exhaust duct. According to another feature, the mixing obstacle is formed by at least one body permeable to the flow of the burnt gases in the exhaust duct.

  According to another feature, the exhaust duct is closed by the body forming the mixing obstacle. According to another particularity, the jet of reducing agent leaving the injection channel forms a single fluid connection between the injector and the mixing obstacle, and the mixing obstacle forms at least one reducing agent trap means. According to another particularity, the mixing obstacle comprises one or more of the following means cooperating or not between them and / or with other means of the injection device: (a) heating means of the mixing obstacle; (b) means for activating the heating means of the mixing obstacle; (c) means for assessing the temperature of the mixing obstacle. According to a first embodiment, the mixing obstacle is formed by at least one grid.

  According to a variant of this first embodiment, at least a portion of the grid is made of conductive material of an electric current. According to a second embodiment, the mixing obstacle is formed by at least a portion of a turbine arranged in the exhaust duct.

  According to another particularity, the gate and the turbine are merged.

  According to a third embodiment, the mixing obstacle is formed by at least two distinct bodies, the preferred planes of the first body and the second body being parallel or inclined with respect to one another.

  According to a variant of this third embodiment, the first body is arranged in a manner connected or not to the second body on the side of the second body facing the injector (2). According to another variant of this third embodiment, the first body is formed by the grid.

  According to another variant of this third embodiment, the second body is formed by at least the part of the turbine. According to another particular feature, downstream of the engine outlet, the exhaust line comprises at least one exhaust emission control device, the injection channel opening into the exhaust duct is arranged in the exhaust line. at a further predetermined distance from the exhaust gas control device upstream from the direction of the flue gas flow in the exhaust duct, and the mixing obstacle is disposed in the exhaust duct between the duct Injection and the antipollution device. According to another particular feature, the antipollution device of the exhaust gas comprises means for assessing its fouling state communicating with the means for activating the reducing agent jet, and the moment and / or the duration of the Injection of reducing agent is controlled by the means for activating the reducing agent jet as a function of the fouling state of the exhaust gas control device. According to another particularity, the means for activating the heating means of the mixing obstacle regulates one or more following parameters as a function of the state of fouling of the exhaust emission control device (a) heating activation moment. the mixing obstacle; (b) temperature of the mixing obstacle; (c) heating time of the mixing obstacle; (d) flow of flue gases in the exhaust duct; (e) reducing agent flow via the injector; (f) quantity of pollution in the exhaust line.

  The invention with its features and advantages will emerge more clearly on reading the description made with reference to a single figure which shows schematically a variant of the device according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION As is illustrated in the figure, the device according to the invention comprises an exhaust duct (1) carrying burnt gases (G) between an outlet (Si) of an internal combustion engine (M), for example a diesel engine, and an outlet (S2) of the exhaust line. The direction of flow of the flue gases is indicated by a double line transparent arrow and operates from left to right in the figure.

  The exhaust duct (1) has a privileged axis (AB). In the example illustrated in the figure, the preferred axis (AB) of the exhaust duct (1) coincides with its axis of symmetry.

  In known manner, the exhaust duct (1) is in the form of a tubular body, the section in the plane perpendicular to the preferred axis (Al3) of the duct (1) may have any profiles compatible with the flow of a fluid such as an exhaust gas.

  An injector (2) for injecting a reducing agent (for example, hydrocarbon, urea) into the exhaust duct (1) directly into the flue gas flow (G) is arranged in the exhaust duct ( 1).

  The injector (2) is connected to at least one source of reducing agent (not shown in the figure).

  The injector (2) comprises at least one injection channel (3) of the reducing agent opening into the exhaust duct (1). The jet of the reducing agent penetrating into the exhaust duct (1) via the injection channel (3) is shown diagrammatically in the figure by means of two double dashed lines referenced (HC). The angle of the opening of the jet (HO) is illustrated using the reference (y). The injection channel (3) has a privileged axis (CD). In the example illustrated in the figure, the preferred axis (CD) of the injection channel (3) merges: - with its axis of symmetry, and - with the preferred axis of the injector (2). The injector (2) comprises at least one activation means (not shown in the figure) of a jet (HO) of reducing agent from the source of reducing agent via the injection channel (3) in the exhaust duct (1). In an alternative embodiment of the invention, the injection channel (3) opening into the exhaust duct (1) is disposed at the end (4) of the injector (2), this end (4) forming a protruding body inside the exhaust duct (1). This end (4) can be formed, for example, using a diffuser of the type described in the state of the art of the European patent application EP 1 314 864 A1. In another variant embodiment of FIG. the invention, the architecture of the injector (2) corresponds to that detailed, for example, in the European patent application EP 1 314 864 A1 cited above. Similarly, the injector and / or the diffuser at the end (4) of the injector (2) can be equipped with means that can change an angle (y) of the opening of the jet (HC) of reducing agent leaving the injection channel (3).

  An antipollution device comprising, for example, at least two modules, is installed in the exhaust duct downstream of the injector (2) relative to the flow direction of the flue gas (G). The first module of the antipollution device disposed at the inlet of the pollution control device with respect to the direction of flow of the flue gases (G) in the exhaust pipe (1), comprises at least one catalyst (T) for regeneration of the antipollution device for example, an oxidation catalyst (T). The second module (not shown in the figure) of the antipollution device is disposed downstream of the catalyst (T). The second module comprises at least one particulate filter and / or at least one NOx trap and / or at least one SCR module (English Selective Catalytic Reduction) and / or at least one other similar device.

  These are anti-pollution means known to those skilled in the art for reducing the pollutant emissions (NOx, SOx, particles, etc.) during the passage of the exhaust duct by the exhaust gases leaving the internal combustion engine (M). . The injection channel (3) of the injector (2) opening into the exhaust duct (1) is arranged at a predetermined distance (X) from the catalyst (T), as shown in the figure. This predetermined distance (X) is measured along the preferred axis (AB) of the exhaust duct (1) from the jet source (HC) formed by the exit or opening of the injection channel ( 3) to the catalyst inlet (T). In the example of the figure, the jet source (HC) is located at the end (4) of the injector (2) forming the projecting body inside the exhaust duct (1). The antipollution device of the exhaust gas comprises means for assessing its state of fouling (not shown in the figure). In another embodiment of the invention, the latter communicate with the means for activating the jet (HO) of reducing agent. Thus, the moment and / or the duration of the injection of reducing agent may advantageously be regulated by the means for activating the reducing agent jet (HC) as a function of the state of fouling of the device. exhaust pollution control.

  In another variant embodiment of the invention, the communication between the means for activating the jet (HO) of reducing agent and the means for assessing the state of fouling of the antipollution device of the exhaust gases operates via management equipment (not shown in the figure) of the vehicle. This management equipment conventionally comprises a computer equipped with a microprocessor processing unit Type CPU (English Computer Processing Unit). The calculator has a layered architecture. It is associated with the various sensors measuring physical quantities, for example, sensors directly or indirectly measuring the fouling state of the exhaust emission control device. In addition, the computer is coupled to the control and control means. The latter can therefore be activated by the computer and can drive various systems and circuits of the vehicle, for example, control the activation of the jet (HC) of the reducing agent of the injector (2), the latter being part of the system. vehicle exhaust. The sensors, the computer as well as the control and control means may comprise essentially electronic objects with microcircuit and memory having or not a multi-layer architecture and / or acquisition cards and / or transmission-reception of data which can communicate with each other and / or with other elements of the vehicle by means of a network, for example, a network compatible with the so-called CAN protocol, a wireless network compatible with short-range technology, and that is to say, essentially a few tens of meters, for example, a radio technology of Bluetooth type or another technology of transmission of cloned waves based on a part of the frequency spectrum (and wavelengths) other than the part of the so-called radio spectrum. The injector (2) is arranged in the exhaust duct (1) so that the preferred axis (CD) of the injection channel (3) is oriented, for example, in the direction of the gas flow. burned (G) in the exhaust duct (1), and forms an angle 0, for example, acute (0 <e <90), with the preferred axis (AB) of the exhaust duct (1). In another variant embodiment of the invention, the opening of the injection channel (3) is arranged at the end (4) of the injector (2) opening into the exhaust duct (1) so as to that the jet (HC) from the injection channel (3) is oriented in the direction of the flue gas flow (G) in the exhaust duct (1). In this configuration the relative positioning of the injector (2) with respect to the exhaust duct (1) can be arbitrary (for example, perpendicular to the exhaust duct (1)), the precise orientation of the opening of the injection channel (3) being provided by the end (4) of the injector (2). Similarly, at least a portion of the injector (2) can be placed outside the wall of the exhaust duct (1) outside of the latter.

  In another embodiment of the invention, the injector (2) is connected with a deflected wall (not shown in the figure) of the exhaust duct (1). The plane formed by this deviated wall is oriented in the direction of the flue gas flow (G) and is inclined relative to the preferred axis (AB) of the exhaust duct (1).

  In another embodiment of the invention, the preferred axis (CD) of the injection channel (3) of the reducing agent is substantially perpendicular to the plane formed by the deflected wall of the exhaust duct (1). The injection device advantageously comprises an obstaclemangler (5) separate from the injector (2). The mixing obstacle (5) is arranged in the exhaust pipe, for example, downstream of the injector (2) with respect to the flow direction of the flue gases (G), and cooperates with the injector (2). ) and the flue gas flow (G). Indeed, the preferred axis (CD) of the injection channel (3) is oriented towards the mixing obstacle (5) as illustrated in the figure. The mixing obstacle (5) is formed by at least one body, for example, substantially two-dimensional or three-dimensional, with a preferred plane (OP), as illustrated in the figure. The body forming the mixing obstacle (5) is permeable (for example, porous) or not to the flue gas flow (G). In another alternative embodiment of the invention, this body may have shaped portions, for example, corrugated or the like, favoring the formation of vortices (and / or turbulence level) in the flow of the flue gases downstream. of the mixing obstacle (5).

  The exhaust duct (1) is closed at least partially by the body forming the mixing obstacle (5). In the example illustrated in the figure, the exhaust duct (1) is closed completely by the mixing obstacle (5). As shown in the figure, the mixing obstacle (5) is arranged in the exhaust duct (1) between the injection channel (3) (or the injector (2)) and the pollution control device (catalyst (T ) on the face). The mixing obstacle (5) is arranged at another predetermined distance (Z) from the injector (2) downstream of the injector (2) in the direction of the flue gas flow (G). This predetermined distance (Z) is measured along the preferred axis (AB) of the exhaust duct (1) between the jet source (HC) formed by the exit or the opening of the injection channel (3) and the point of intersection of the privileged plane (OP) of the mixing obstacle (5) with the privileged axis (AB) of the exhaust duct (1). The predetermined distance (Z) between the injector (2) and the mixing obstacle (5) is chosen so that the jet (HC) of reducing agent leaving the injection channel and oriented towards the mixing obstacle (5). ) forms a single fluid connection between the injector (2) and the mixing obstacle (5). Similarly, the predetermined distance (Z) between the injector (2) and the mixing obstacle (5) is chosen as a function of the parameters such as, for example, the flow rate of the flue gases (G) in the exhaust duct (1), the flow rate of reducing agent via the injection channel (2), the angle (y) of the opening of the jet (HC) etc., so that the mixing obstacle (5) forms the less a means of trapping the reducing agent. This means that the totality of the reducing agent dispersed by the injector (2) in the jet (HC) is deposited on the mixing obstacle (5) before reaching an internal wall of the exhaust duct (1) in vis-à-vis the injector (2). Thus, no liquid film that can disrupt the proper operation of the catalyst (T) is created on the inner wall of the exhaust duct (1) vis-à-vis the injector (2). The mixing obstacle (5) is arranged at a predetermined distance (Y) from the catalyst (T) in the direction of the flue gas flow (G). This predetermined distance (Y) is measured along the preferred axis (AB) of the exhaust duct (1) between the point of intersection of the preferred plane (OP) of the mixing obstacle (5) with the axis (AB) of the exhaust duct (1) and the inlet of the catalyst (T), as shown in the figure. The predetermined distance (Y) between the mixing obstacle (5) and the catalyst (T) is chosen as a function of parameters such as, for example, the flow rate of the flue gases in the exhaust duct (1), the flow rate reducing agent via the injector (2), the temperature of the mixing obstacle (5), etc., so as to guarantee a homogeneous mixture (GHC) of burnt gas / reducing agent at the inlet of the catalyst (T). The mixing obstacle (5) comprises one or more of the following means cooperating or not between them and / or with other means of the injection device: (a) heating means of the mixing obstacle (5), for example similar those described in European Patent EP 0 594 794 B1 cited above; (b) means for activating the heating means of the mixing obstacle (5); (c) means for assessing the temperature of the mixing obstacle (5).

  In another embodiment of the invention, the mixing obstacle (5) is formed by at least one grid. At least a portion of the grid may be made of conductive material or not of an electric current. In another variant embodiment of the invention, the means for activating the heating means of the mixing obstacle (5) regulates one or more following parameters depending on the fouling state of the exhaust gas pollution control device. (a) heating activation moment of the mixing obstacle; (b) temperature of the mixing obstacle (5); (c) heating time of the mixing obstacle (5); (d) flue gas flow (G) in the exhaust duct (1); (e) reducing agent flow via the injector (2); (f) quantity of pollution in the exhaust line (eg, upstream or downstream of the pollution control device). Note that the advantageous presence of the heating means of the mixing obstacle (5) constitutes a first major difference of the device according to the invention and the state of the art JP 2005 214100 cited above. Indeed, thanks to these heating means, it is possible to increase the heat exchange between: the flue gas flow (G) and the liquid phase of the reducing agent present in the jet (HC), so as to evaporating the reducing agent deposited on the mixing obstacle (5) more rapidly. the mixing obstacle (5) and the flue gas flow (G) passing through the mixing obstacle. Therefore, the temperature of the mixture (GHC) can be regulated (increased) downstream of the mixing obstacle. This favors the faster operation of the antipollution device downstream of the mixing obstacle (5), especially during the cold start. It is therefore possible to reduce the amount of reducing agent injected into the conduit (1) via the injector (2) by ultimately reducing the consumption of reducing agent. The axis (privileged (CD) of the injection channel (3) is advantageously inclined by an angle α with respect to the preferred plane (OP) of the mixing obstacle (5) such that 0 <c <90 (case shown in the figure) or 90 <a <180 (case not shown in the figure) This characteristic represents a second major difference between the device according to the invention and the state of the art JP 2005 214100 cited above. shows the example in the figure, when the preferred axis (CD) of the injection channel (3) is inclined relative to the preferred plane (OP) of the mixing obstacle (5), the jet (HC) of the reducing agent is also inclined with respect to the preferred plane (OP) of the mixing obstacle (5) In the variant where the mixing obstacle (5) is represented by a substantially two-dimensional object such as the grid, this inclination further reinforces the ability of the grid to catch drops of the liquid phase of the reducing agent jet (HC). Indeed, because of the inclination, the thickness of the grid contributes to increasing the actual contact area between the gate and the liquid phase of the jet (HC). In other words, when the jet (HC) is inclined with respect to the grid, the substantially two-dimensional structure of the grid is completed by the third dimension, namely, the thickness of the grid. This means that the actual area of contact between the grid and the liquid phase of the jet (HO) is formed by both the connection nodes of the grid and the thickness of the grid (contrary to the case described in JF '2005 214100 where the jet is perpendicular to the grid and, therefore, the actual area of contact between the grid and the liquid phase of the jet (HC) is formed exclusively by the connection nodes of the grid). As a result, the device according to the invention, which captures almost all the reducing agent diffused by the jet (HC), further protects (compared with the state of the art) the internal walls of the exhaust duct (1) against forming the liquid reducing agent film which causes accelerated aging of the catalyst and / or the filter element. In another embodiment, the preferred plane (OP) of the mixing obstacle (5) is inclined (case not shown in the figure) or perpendicular (case shown in the figure) with respect to the privileged axis (AB) exhaust duct (1). The mixing obstacle (5) is therefore arranged in the exhaust duct (1) at least partially through the flue gas flow (G). In a variant of this embodiment, because of the inclination of the privileged plane (OP) of the mixing obstacle (5) relative to the privileged axis (AB) of the exhaust duct (1), the preferred axis (CD) of the injection channel (3) may be perpendicular to the preferred plane (OP) of the mixing obstacle (5). However, this architecture remains significantly different compared to the state of the art through JP 2005 214100 because the mixing obstacle (5) represented, for example, by the grid, in no way directs the flow of flue gases in the direction of injection of reducing agent by the injector (the preferred plane of the grid being inclined with respect to the preferred axis (AB) of the exhaust duct (1)). In another variant embodiment (not shown in the figure), the preferred plane (OP) of the mixing obstacle (5) coincides with the privileged axis (AB) of the exhaust duct (1). In another variant embodiment (not shown in the figure), the preferred plane (OP) of the mixing obstacle (5) is parallel with respect to the preferred axis (AB) of the exhaust duct (1). In summary, the device according to the invention makes it possible to promote the heat exchange between the flue gases and the reducing agent injected into the exhaust duct and to improve the homogeneity of their mixture (GHC), while reducing the necessary time to achieve this, especially during cold start. Similarly, thanks to the injector according to the invention it is possible to install the injector (2) of reducing agent closer to the catalyst (T). This makes it possible to free up the available space along the exhaust duct to, for example: reduce the size of the exhaust line, and / or increase the linear sizes of the pollution control device along the exhaust duct, and and / or installing other equipment in the exhaust duct (for example, temperature sensors, speed sensors and / or flue gas analyzers, etc.). It should be obvious to those skilled in the art that The present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered by way of illustration, but may be modified within the scope defined by the scope of the appended claims, and the invention should not be limited to the details given above.

  Finally, although the invention has been illustrated by an example of a device on a mixing obstacle (5) represented by the grid in the figure, it will be understood that the invention also relates to a mixing obstacle that can be formed by other body (s) arranged in the exhaust duct downstream of the injector (2) and upstream of the catalyst (T) to improve the mixing of the flue gases with the reducing agent. By way of illustration, the mixing obstacle (5) may be formed by at least a part of a turbine (for example, its wheel, its blades) arranged in the exhaust pipe (1) downstream of the turbine. injector (2) and upstream of the catalyst (T). In other words, the injector (2) is installed between the output (Si) of the motor (M) and the mixing obstacle (5) formed by the turbine. Note that the vanes of the impeller wheel are heated by the flue gas from the first moments following the cold start of the engine (M). As a result, the temperature of the mixture (GHC) burned gas / reducing agent downstream of the turbine increases more rapidly, which promotes the faster operation of the pollution control device downstream of the mixing obstacle (5), especially during cold start of the engine (M). Similarly, the reducing agent from the jet (HC) and landing directly on the hot parts of the wheel (blades) of the turbine evaporates very quickly, especially during: the period of operation of the engine cold. The mixture of the flue gas is therefore advantageously used with the reducing agent in the gas phase. Similarly, the rotation of the wheel of the turbine driven by the flow of the burned gases makes it possible to act as a mixer swirling the burnt gases so as to increase the turbulence of the flow at the outlet of the turbine. Similarly, the rotation of the turbine wheel makes it possible to centrifuge the liquid film of reducing agent poured by the jet (HO) of the injector (2) onto at least some elements of the wheel of the turbine (T), for example on his blades. This results in high homogeneity of this mixture (GHC) downstream of the turbine. In another variant of this embodiment, the mixing obstacle (5) may be formed by at least two separate bodies. The first body may or may not be connected to the second body on the side of the second body facing the injector (2). Indeed, the first body may, for example, be connected to the inner wall of the exhaust duct (1). The first body can be formed, for example, by the grid. Similarly, the second body may also be connected to the inner wall of the exhaust duct (1). The preferred planes of the first body and the second body may, for example, be parallel or inclined relative to each other. The second body may be formed, for example, by at least a portion of the turbine, for example, by the impeller of the turbine. The latter can therefore have in its portion facing the injector (2) of the grid connected to the body of the turbine and / or the inner wall of the exhaust duct (1). In this configuration, the grid, whether or not part of the turbine, forms a shield protecting, for example, the vanes of the jet turbine wheel (HC), so that the liquid film of reducing agent discharged by the jet ( HC) of the injector (2) is formed on the grid instead of forming on the wheel of the turbine. This advantageously avoids aggression, for example of chemical or mechanical nature, the sensitive elements of the turbine, for example, its wheel, its blades, by the reducing agent and / or the uncontrollable formation of the rigid deposit (oxidation cluster) reducing agent on the vanes of the wheel can disrupt the balance of the wheel at high rotational speeds. As mentioned above at least a portion of the grid may be made of conductive material or not an electric current. Thus, it can be heated, for example continuously, to promote faster evaporation of the liquid reducing agent film present on the grid. In another variant of this embodiment, the grid may be heated, for example in a punctual manner to promote faster evaporation of the liquid reducing agent film present on the grid only during operation of the engine (M) when cold. . Another advantage of this embodiment is that it excludes a priori any formation of the liquid reducing agent film on the internal walls of the exhaust duct (1) which causes accelerated aging of the catalyst and / or the filter element. Indeed, even if part of the liquid phase of the reducing agent passes through the grid, it is immediately captured by the turbine whose blades centrifuge and evaporate. In another variant embodiment, the two bodies forming the mixing obstacle (5), for example the grid and the turbine, may be merged. In this configuration, the grid connected to the turbine may be disposed on the side of the turbine opposite to that directed towards the injector, that is to say, downstream of the turbine with respect to the direction of flow of the burned gases. (BOY WUT).

Claims (17)

  An injection device for injecting a reducing agent into a flue gas flow (G), formed on an exhaust duct (1) downstream of an internal combustion engine (M), and on the other hand, oriented from the output (Si) of the motor (M) to the outlet (S2) of the exhaust line, comprising - at least one source of reducing agent, - at least one injector (2) connected at the source of reducing agent and formed by at least one injection channel (3) of the reducing agent opening into the exhaust duct (1), the preferred axis (CD) of the injection channel (3) ) being inclined at an angle θ relative to the preferred axis (AB) of the exhaust duct (1), at least one means for activating a reducing agent jet (HC) coming from the source of reducing agent via the injection channel (2), characterized in that the injection device comprises a mixing obstacle (5) arranged in the exhaust duct (1) downstream of the injector (2) relative to at u flow direction of the flue gases (G) at a predetermined distance (Z) from the injection channel (3) and in that the preferred axis (CD) of the injection channel (3) is directed towards the mixing obstacle (5), opposite this obstacle (5) to avoid an injection on the walls of the exhaust duct (1), and is inclined at an angle with respect to the preferred plane (OP) of the mixing obstacle (5) such that 0 <a <90 or 90 <a <180.   2. Injection device according to claim 1, characterized in that the preferred plane (OP) of the mixing obstacle (5) is inclined or perpendicular with respect to the preferred axis (AB) of the exhaust duct (1). ), the injection point of the injector (2) being located near a first lateral side of the exhaust duct (1) and the injection orientation being directed towards a second lateral side of the duct; exhaust (1) opposite said first lateral side.   3. Injection device according to claim 1 or 2, characterized in that the mixing obstacle (5) is formed by at least one body permeable to the flow of the flue gases (G) in the exhaust duct ( 1).   4. Injection device according to one of claims 1 to 3, characterized in that the exhaust duct (1) is closed by the body forming the mixing obstacle (5).   5. Injection device according to one of claims 1 to 4, characterized in that the jet (HC) of reducing agent leaving the injection channel (3) forms a single fluid connection between the injector (2) and the mixing obstacle (5), and in that the mixing obstacle (5) forms at least one reducing agent trap means.   6. Injection device according to one of claims 1 to 5, characterized in that the mixing obstacle (5) comprises one or more of the following means cooperating or not between them and / or with other means of the device d injection: (a) heating means of the mixing obstacle (5); (b) means for activating the heating means of the mixing obstacle (5); (c) means for assessing the temperature of the mixing obstacle (5).   7. Injection device according to one of claims 1 to 6, characterized in that the mixing obstacle (5) is formed by at least one gate.   8. Injection device according to claim 7, characterized in that at least a portion of the gate is made of conductive material of an electric current.   9. Injection device according to one of claims 1 to 6, characterized in that the mixing obstacle (5) is formed by at least a portion of a turbine arranged in the exhaust duct (1).   10. Injection device according to claims 7 and 9, characterized in that the gate and the turbine are merged.   11. Injection device according to one of claims 1 to 6, characterized in that the mixing obstacle (5) is formed by at least two separate bodies, the preferred planes of the first body and the second body being parallel or inclined relative to each other.   12. Injection device according to claim 11, characterized in that the first body is arranged in a manner connected or not to the second body on the side of the second body facing the injector (2).   13. Injection device according to claim 7 and according to one of claims 11 to 12, characterized in that the first body is formed by the grid.   14. Injection device according to claim 9 and according to one of claims 11 to 13, characterized in that the second body is formed by at least the part of the turbine.   15. Injection device according to one of claims 1 to 14, characterized in that downstream of the output (SI) of the engine (M), the exhaust line comprises at least one antipollution device of the exhaust gases. exhaust, in that the injection channel (3) opening into the exhaust duct (1) is arranged in the exhaust line at another predetermined distance (X) from the exhaust emission control device at its exhaust upstream with respect to the direction of the flue gas flow (G) in the exhaust duct (G), and in that the mixing obstacle (5) is arranged in the exhaust duct (1) between the injection channel (3) and the antipollution device.   16. Injection device according to claim 15, characterized in that the antipollution device of the exhaust gas comprises means 15 for assessing its fouling state communicating with the jet activation means (HC). reducing agent, and in that the moment and / or duration of the reducing agent injection is regulated by the means for activating the reducing agent jet (HC) as a function of the fouling state of the device exhaust pollution control. 20   17. An injection device according to claim 6 and claim 16, characterized in that the means for activating the heating means of the mixing obstacle (5) regulates one or more following parameters depending on the state of fouling of the exhaust emission control device: (a) heating activation moment of the mixing obstacle (5); (b) temperature of the mixing obstacle (5); (c) heating time of the mixing obstacle (5); (d) flue gas flow (G) in the exhaust duct (1); (e) reducing agent flow via the injector (2); (f) quantity of pollution in the exhaust line.