FR2913069A3 - Reagent injection device for use in internal combustion engine, has thermal protection ring comprising middle body between support face and end including orifice, where body forms heat conducting interface between tip and cooling support - Google Patents

Abstract

The device has an injector (2) connected to a reagent source and comprising a free end forming a nozzle tip (4). A reagent injection channel (20) emerges in a gas sending line through an end of the tip. A monoblock thermal protection ring (3) of the tip supports on a shoulder (E) of the injector on one side by a support face and provided with an orifice (32) on another side for passing a jet of reagent. The ring has a middle body (C) between the support face and an end including an orifice (32), where the body forms a thermal conducting interface between the tip and a cooling support.

Description

Injection device with thermal protection of the injector nose

  TECHNICAL FIELD OF THE INVENTION The present invention relates, in the field of internal combustion engines, to a device for injecting a reaction agent.

  The invention relates more particularly to an injection device with thermal protection of the injector nose. BACKGROUND OF THE INVENTION Known injectors generally have a protruding end in a pipe or chamber where a reaction is to occur. The injectors are more particularly located in the cylinder head or in the exhaust line, to provide a reactive agent from their projecting end, in the form of a jet. Thus, the reagent can be mixed quickly and homogeneously and the reaction can be satisfactorily performed.

  However, the injectors suffer from difficult conditions, in particular in terms of heat (problem of resistance of the materials) and in terms of fouling. This limits the allowable temperature level for an injector. It is understood that exceeding the thermal specifications raises reliability problems: - fouling of the nose by coking (injection problem); reliability of the mechanism of the needle for the holding of the materials (risk of fire due to a leakage in the injector). In these very severe conditions of implantation in the cylinder head or the exhaust line, the injectors are particularly weakened at their free end (the nose of the injector is the most exposed and therefore the most fragile part). For injection injectors in the cylinder head, the nose is largely cooled by the circulation of diesel, so that the reliability is not too reduced. On the other hand, the problem is more acute for injectors that operate intermittently, for example to trigger a phase of particle filter regeneration (FAP). It is known in the prior art, from document JP 2002 151734 or its equivalent EP 1 138 891, an injection system in which the injector is embedded in a retracted position inside an internal wall of the exhaust duct, so as not to suffer certain detrimental effects of heat. A bypass passage to this recessed injector is provided to guide the jet of fuel to the exhaust duct. The disadvantage of this system is that the jet delivered from the narrow bypass passage can not allow a homogeneous mixture between the injected agent and the gases flowing in the pipe. The walls of the narrow passage receive a portion of the jet and a liquid film is formed. In the case of an injection in the exhaust pipe, upstream of an antipollution device, this liquid will flow to the pollution control device. The performance of a catalyst of this pollution control device can not be optimal and there will in any case an overconsumption of the injected agent.

  It is also known, according to a conventional arrangement of an injector, to place the injection end in a slight recess or at a level flush with the internal walls of the exhaust duct. However, the hot gases still bring heat to this end and the injector concentrates a large amount of heat that causes reliability problems. GENERAL DESCRIPTION OF THE INVENTION

  The object of the present invention is to overcome one or more disadvantages of the prior art by proposing a sufficiently resistant and reliable injection device to be implanted in the cylinder head or in an exhaust duct subjected to very severe conditions (heat residual particles).

  This object is achieved by an injection device for injecting a reaction agent into a gas circulation line of an internal combustion engine, the device comprising at least one injector connected to a source of reaction agent and including a free end forming an injector nose, an injection channel of the reaction agent opening into the circulation line through a first zone of the tip of the injector nose, characterized in that it comprises a protective ring thermal nozzle of the injector leaning on one side on a shoulder of the injector by at least one bearing face and provided on the opposite side of an orifice for passing a jet of reaction agent, the ring comprising at least one intermediate body between the bearing face and the end including the orifice, the intermediate body forming a thermally conductive interface between the nozzle nose and a cooling support. Thus, it is advantageously allowed to dissipate the heat provided by the hot gases by the ring which protects the nozzle nose, this ring may be in contact with a large exchange surface.

  According to another feature, the ring is a one-piece thermally conductive piece and fitted on the nose of the injector, the ring being interposed between a cylindrical portion of the nozzle nose and the support cooled by a cooling fluid. In another feature, the injector diffuses the jet from the first zone, the orifice being delimited by at least one edge remote from the injector nose and covering a second zone of the end of the injector nose surrounding the first zone. According to another feature, said edge is formed in a narrowing section of the ring.

  According to another feature, the second zone and the first zone of the tip of the nose are concentric and oriented in the same direction. According to another feature, the distance between the shoulder of the injector and the free end of the injector including a nozzle is slightly greater than the length covered by the ring, so that the nozzle nose cuts at its end. an outcrop plan located at the edge.

  According to another feature, the ring comprises a flange to bear on the shoulder of the injector and, opposite the flange, a frustoconical portion. According to another feature, the smallest section of the frustoconical portion is extended inwardly by a protective disc forming a face opposite to the bearing face. According to another feature, the collar forms a seal. In another feature, the thermal protection ring is essentially made of copper, while the nozzle nose is made of stainless steel. The injection device may advantageously be implanted in a cylinder head of a heat engine, at a combustion chamber or alternatively in an exhaust line of a heat engine. The invention with its features and advantages will emerge more clearly on reading the description given with reference to the appended drawings in which: FIG. 1 shows a sectional view of an injection device according to an embodiment of the invention. invention; FIG. 2 illustrates an exemplary implantation of an injection device according to the invention; FIGS. 3A and 3B show the fitting of a thermal protection ring on an injector nose to form a device for injection according to the invention Figure 4 illustrates an injection device of the prior art; FIG. 5 shows an embodiment of an injection device according to the invention; FIG. 6 illustrates a bottom view and a longitudinal sectional view of a protective ring that can be inserted between an injector nose; and a cooled support; - Figure 7 shows an exploded view for the implementation of an injection device according to the invention in an exhaust line.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The injection device makes it possible to inject a reaction agent into a gas circulation line (G) of a heat engine (M). It comprises at least one injector (2) connected to a source of reaction agent. The free end of the injector forms an injector nose (4). As illustrated in FIG. 1, an injection channel (20) of the reaction agent opens into the gas circulation circulation line (G) through the end of the injector nose (4). Depending on the implantation of the injection device, the heat to which the device must face may come from hot gases flowing at the inlet of a combustion chamber or exhaust gas. The injection device according to the invention provides a ring (3) thermally conductive fitted on the nose (4) of the injector (2) to dissipate heat (by conduction) to a support (S) which is cooled by a cooling fluid. The ring (3) is for example inserted between a cylindrical portion of the nozzle nose (4) and the support (S) cooled, as shown in Figure 5. This ring (3) provides thermal protection for the nose (4). ) of the injector (2) since it dissipates the heat from the hot gas flow line and almost completely covers the injector nozzle (4), with the exception of an orifice (32) allowing let a jet of reaction agent pass. Without limitation, the ring (3) is preferably a single piece. The comparison between FIGS. 4 and 5 illustrates the thermal protection provided according to the invention (FIG. 5) for the injector nose. Referring to Figure 4 relating to a known embodiment, it is found that it is through a sealing washer (Re) that the support having a yoke function can cool the injector. When there is no continuous flow of diesel in the injector (2), it is cooled only through this medium, whose cooling is provided by water or by air. Therefore the heat (Q) provided by the hot gases is transmitted throughout the injection nose, as indicated by the succession of arrows, and dissipated via the sealing washer by a small exchange surface (SE). This exchange surface (SE) corresponds to a shoulder of the support on which abuts the sealing washer, the injector being furthermore positioned by a guide wall (GI) of the support. The direct heat exchange between the nose of the injector and the support forming the cylinder head is not feasible because the centering of the injector in the support takes place by a diameter located at the top of the injector, at the level of the guiding wall (GI) shown in Figure 4. A clearance is necessary in this case between the nose of the injector and its housing to avoid a hyperstatic mounting and a risk of blockage of the internal needle of the system d 'injection. With reference to FIG. 4, the path of evacuation of the heat stored by the nose of the injector is complex. To reach the cylinder head, the heat rises through the nose of the injector and passes through the sealing washer (Re). The conduction of heat is impeded by a section restriction at the sealing washer. As the road ahead is important, the conductivity of the nose is not good. Referring to the other figures that Figure 4, it is proposed according to the invention to establish a more direct contact between the nose (4) of the injector (2) and the cooled cylinder head or support (S) cooling. With this type of solution, the path taken by the heat is shorter (to reach the support (S) and the exchange surface (SE ') is larger, as shown in Figures 5 and 7. The path of heat exchange is more direct in that the heat passes from the nose (4) of the injector (2) to the support (S) cooled cylinder head via the conductive ring which is in contact at a time with the support (S) and with the nose (4) In other words, the thermal resistance of the nose (4) of the injector (2) is short-circuited The example of injection device illustrated in FIGS. , 2 and 5 allows better dissipation of heat and considerably reduces the direct contact between the injector nozzle (4) and the hot gases The ring (3) covers the entire injector nozzle (4) with the exception a first zone (41) of the tip of the injector nose (4) through which the injection channel (20) opens out, With reference to FIGS. 3A, 3B and 6, this first zone ne (41) is discovered through an orifice (32), preferably central, located at the narrower end of the ring (3). A second zone (42) of the tip of the injector nose (4) surrounding the first zone (41) is covered by a protective disk (35). On the side of its end of greater section, the ring (3) for thermal protection of the injector nose (4) rests on a shoulder (E) of the injector (2) by at least one bearing face . In the example of the figures, the outlet orifice (32) allowing the nozzle to inject the jet (J) has a smaller diameter than the orifice formed at the bearing face. The ring (3) comprises at least one body (C) intermediate between the bearing face and the end including the orifice (32) output. This intermediate body (C) forms a thermally conductive interface between the injector nose (4) and the cooling support (S). In a preferred embodiment of the invention, the ring (3) of thermal protection consists essentially of copper, while the nozzle nose (4) is made of stainless steel. It is understood that the ring (3) must be made of a material with high thermal conductivity. The protective disc (35) forms a face opposite to the bearing face to cover and protect the nose (4) of the injector (2). The edge (33) delimiting the outlet orifice (32) may be of frustoconical type and covers the second zone (42) of the end of the injector nose (4), peripheral to the first (41) central zone. This second zone (42) and the first zone (41) of the end of the nose are for example concentric and oriented in the same direction. The edge (33) is remote from the end of the injector nose (4) and thus remotely covers the periphery of the injection zone (41). This edge (33) formed in the narrowing section of the ring (3) does not touch the tip of the nose (4), so as not to constrain it to mounting. As illustrated in particular in Figures 1, 5 and 6, the ring (3) comprises a flange (30) for pressing on the shoulder (E) of the injector (2). Opposite this flange (30), the ring (3) comprises a frustoconical portion (tc) to fit the end of the nose (4) of the injector (2). The smallest section of the tapered portion (tc) can be extended inwardly by the protective disc (35). With reference to FIG. 1, there is a clearance (e) between the protective disk (35) which radially extends the frustoconical portion (tc) and the zone (42) vis-à-vis the end of the nose (4). With reference to FIGS. 3A and 3B, the distance (L1) between the shoulder (E) of the injector (2) and the free end of the injector (2) where the nozzle is placed is, for example, slightly greater than the length (L2) covered by the ring (3). In this case, the tip of the nose (4) may protrude slightly from the ring (3). With reference to FIGS. 3A, 3B and 6, the ring (3) can be mounted by the injection end on the nose (4) of the injector (2). It comprises a bore (34) which forms a housing for the nose (4) of the injector (2), a flange (30) in the upper part in contact with the support (S) and with a shoulder (E) of the injector (2) delimiting the base of the nose (4). The ring (3) can not slip towards the gas flow line (G) since the flange (30) is retained by stops of the support (S). The flange (30) also provides a sealing function. Referring to Figures 5 and 7, the seal (s) (s) (s) placed (s) against the support (S) comprise an opening (0) to let the jet. The restriction side nose (4) in the ring (3), with the tapered type portion (tc) extended by the protective disc (35), allows to protect the end of the nose (4) of the thermal generated by the gases (in particularly the exhaust gases, as illustrated in the example of Figure 2). Other forms of restriction can naturally be provided to better protect the tip of the nose (4). This restriction also provides a keying (making the error impossible for the connection) at the time of installation of the ring (3) on the nose (4) of the injector (2). Indeed, the tip of the nose (4) is conical type. The ring (3) comprises an outer diameter to the maximum material (principle of maximum material) to ensure a mounting without constraint in the cylinder head or support (S) cooled. In the type of implantation illustrated in FIG. 2, 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 output (S2) of the exhaust line. The direction of flow of the flue gas (G) is indicated by a double line transparent arrow and operates from left to right in Figure 2. The exhaust pipe (1) has a preferred axis (AB) which may or may not coincide with its axis of symmetry. In known manner, the exhaust duct (1) is in the form of a tubular body whose section in the plane perpendicular to the preferred axis (AB) of the duct (1) may have any profiles compatible with the flow of a fluid such as an exhaust gas. In this case, the injector (2) is used to inject a reducing agent (for example, hydrocarbon, urea) into the exhaust duct (1) directly into the flue gas flow (G). . The injector (2) is naturally connected to at least one source of reducing agent (not shown). The reaction mixture (Z) is all the more homogeneous as the injector (2) is well placed and functions properly. The ring (3) of thermal protection improves the holding of the injector and prevents the formation of coking on the nose (4) of the injector (2). The jet of the reducing agent (J) enters the exhaust pipe (1) via the injection channel (20), passing through the end orifice (32) of the ring (3). The injection channel (20) has a preferred axis which can merge with its axis of symmetry, and with the preferred axis of the injector (2).

  With reference to FIG. 2, an antipollution device comprising, for example, one or more modules, can be installed in the exhaust duct downstream of the injector (2) with respect to the direction of flow of the flue gases (G ). A 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 gas (G) in the exhaust pipe (1), comprises at least one catalyst (T) for regeneration of the pollution control device. for example, an oxidation catalyst (T). A second module (not shown in the figure) of the antipollution device may be disposed downstream of the catalyst (T). This 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 (1) by the flue gases (G) leaving the engine (M) internal combustion. The injection device according to the invention, with the ring (3) of thermal protection allows to place the injector against the current relative to the flow of gas. The device can be placed in a cavity of the duct (1), as illustrated in the example of Figure 2 (implantation of the nose in a reduced gas velocity zone). Whatever the orientation of the injector (2), the ring may be interposed between a cylindrical portion of the injector nose (4) and the support (S) cooled by a cooling fluid (water, air for example) . This support (S) may be the yoke part into which the injector (2) is introduced. In summary, the device according to the invention makes it possible to promote heat exchange with a ring (3) of relatively easy design, without requiring any particular modification in the implantation mode of the injector (2). This type of device therefore allows a great flexibility of implantation of the injector (2) and the life of the injector is considerably increased. 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.

Claims (12)

  1. Injection device for injecting a reaction agent into a gas circulation line (G) of an internal combustion engine (M), the device comprising at least one injector (2) connected to an agent source of reaction and including a free end forming an injector nose (4), an injection channel (20) of the reaction agent opening into the circulation line through a first zone (41) of the tip of the nose of injector (4), characterized in that it comprises a ring (3) for thermal protection of the injector nose (4) supported on one side on a shoulder (E) of the injector (2) by least one bearing face and provided on the opposite side of an orifice (32) for passing a jet of reaction agent, the ring (3) comprising at least one body (C) intermediate between the face of support and the end including the orifice (32), this body (C) intermediate forming a thermally conductive interface between the nozzle nose (4) and a support (S) d e cooling.   2. Device according to claim 1, wherein the ring (3) is a one-piece thermally conductive piece and fitted on the nose (4) of the injector (2), the ring (3) being interposed between a cylindrical portion of the nose injector (4) and the support (S) cooled by a cooling fluid.   3. Device according to claim 1 or 2, wherein the injector (2) diffuses the jet from the first zone (41), the orifice (32) being delimited by at least one edge (33) remote from the nose of injector (4) and covering a second zone (42) of the tip of the injector nose (4) surrounding the first zone (41).   4. Device according to claim 3, wherein said edge (33) is formed in a narrowing section of the ring (3).   5. Device according to claim 3 or 4, wherein the second zone (42) and the first zone (41) of the tip of the nose are concentric and oriented in the same direction.   6. Device according to one of claims 1 to 5, wherein the distance (L1) between the shoulder (E) of the injector (2) and the free end of the injector (2) including a nozzle is slightly greater to the length (L2) covered by the ring (3).   7. Device according to one of claims 1 to 6, wherein the ring (3) comprises a flange (30) for resting on the shoulder (E) of the injector (2) and, opposite the flange (30), a frustoconical portion (tc).   8. Device according to claim 7, wherein the smallest section of the frustoconical portion (tc) is extended inwardly by a protective disc (35) forming a face opposite to the bearing face.   9. Device according to claim 7 or 8, wherein the flange (30) forms a seal.   10. Device according to one of claims 1 to 9, wherein the ring (3) of thermal protection consists essentially of copper, while 15 the injector nozzle (4) is made of stainless steel.   11. Use of the device according to one of claims 1 to 10, characterized in that the injection device is located in a cylinder head of a heat engine, at a combustion chamber.   12. Use of the device according to one of claims 1 to 10, characterized in that the injection device is located in an exhaust line of a heat engine.