FR2938604A1 - FUEL VAPORIZATION DEVICE, POST-PROCESSING SYSTEM AND CONTROL METHOD THEREOF - Google Patents

Abstract

The invention relates to a device (1) for fuel vaporization receiving liquid fuel and having an outlet orifice (33) opening directly into an exhaust line of a vehicle, for delivering vaporized fuel. According to the invention, the device comprises: a main body (10) comprising at least two housings (11) for each receiving a heating rod (2) extending parallel to the longitudinal axis (XX '), a channel (14) ) inlet for receiving liquid fuel, and a central channel (15) extending along the longitudinal axis (XX ') for conveying liquid fuel received by the inlet channel (14); two chambers (13) of vaporization each extending one of the two housings (11), and receiving the active portion (20) of the heating rod; means (4, 18, 18 ') for simultaneously distributing the liquid fuel conveyed through the central channel (15) to each of the two chambers; and means (3, 12) for conveying vaporized fuel from the chambers to the outlet port (33).

Description

The present invention relates to post-treatment of nitrogen oxides (NOX) and soot particles (PM) generated in a vehicle exhaust line. with thermal engine. The evolution of the regulations on the pollutant emissions of vehicles with a heat engine leads, particularly for vehicles with so-called "lean burn" engines, to the setting up of such post-treatments. A first type of known post-processing system is to make traps accumulating within them the species to be treated. These traps need to be cleaned periodically throughout their use (driving the vehicle). The so-called regeneration operation is carried out by operating the engine in a "rich mixture" condition by modifying its settings, so as to increase the temperature of the exhaust gases to a value favorable to combustion. particles of soot contained in the particulate filter, either to increase the amount of "reducing agents" (unburned hydrocarbons, carbon monoxide, hydrogen) in order to convert the nitrogen oxide molecules retained in the trap into inert molecules of 'nitrogen. With this type of system, however, the driver may experience driving discomfort due to changes in engine speed. In addition, increasing the amount of fuel injected into the cylinders increases the risk that droplets will mix in the engine oil, thus degrading the engine lubrication performance. To avoid these disadvantages, a second type of post-treatment system has been proposed in which the fuel is injected directly into the exhaust line in liquid or vapor form.

This operation makes it possible to introduce reducing species as close as possible to particulate filters and traps to facilitate the rise in temperature or reduction of the species stored therein. One solution for improving the regeneration efficiencies is to select or introduce more reactive species, that is to say molecules with higher reductive potential. This is done when introducing hydrocarbons (HC) to convert them to carbon monoxide (CO) and hydrogen (H2) by a reforming action.

In the following, more particularly, the aftertreatment systems in which the fuel is injected directly into the exhaust line in vaporized form are of interest. Document EP 1 643 092 A1 describes such a system in which a hydraulic pump takes the liquid fuel in the vehicle tank to deliver it inside an enclosure of a vaporizer comprising a heating pencil, typically a candle. electric heating, to ensure the vaporization of the liquid. The vaporized fuel is then delivered directly into the exhaust line, upstream of the traps and particulate filters in the direction of the exhaust, to allow the regeneration of the latter. Document FR 2 904 362 also describes a similar system in which the fuel is injected in liquid form into the vaporizer, not by means of a hydraulic pump, but by using a pressurized sector of the fuel injection circuit of the fuel injection system. engine. In both cases, the vaporizer geometries have the disadvantage of having a large volume around the heating rod. The vaporization of the hydrocarbons is thus delayed because of the greater mass of fuel to be evaporated. In this case, the liquid fuel can also lead to the formation of coke due to the long duration of contact of the liquid fuel with the surface of the red-raised pencil. The carbon deposit that forms on the surface can then lead to problems of deterioration of the heating rod. The present invention aims to overcome the above disadvantages by providing a vaporization device in which the response time is reduced, so as to improve the durability of the system. For this purpose, the invention firstly relates to a fuel vaporization device for equipping a system for post-treatment of pollutant emissions in an exhaust line of a heat engine vehicle, the device being able to receive fuel liquid and having an outlet opening opening directly into said exhaust line, capable of delivering vaporized fuel, characterized in that it comprises: a main body comprising at least two housings each intended to receive and hold a heating rod; extending parallel to the longitudinal axis of said main body, an inlet channel for receiving liquid fuel, and a central channel extending along the longitudinal axis for conveying liquid fuel received through the inlet channel of the device; - Two vaporization chambers each extending one of the two housing, each vaporization chamber being adapted to receive the active portion of the corresponding heating rod; first means for simultaneously distributing the liquid fuel conveyed by the central channel to each of the two vaporization chambers; and second means for conveying the vaporized fuel from the vaporization chambers to the outlet port.

The device may comprise more than two housings, each being able to receive and maintain a heating rod extending parallel to the longitudinal axis of said main body, and a corresponding number of vaporization chambers each extending a housing to receive the active part of the housing. a corresponding heating pencil. In this case, said first means are adapted to simultaneously distribute the liquid fuel conveyed by the central channel to each of the vaporization chambers. In a particularly advantageous embodiment, said first means comprise, firstly, a screw having a screw head and a rod placed along the longitudinal axis of the main body in the extension of the central channel, said rod being pierced axially in its center and radially by at least one opening below the screw head, and secondly, an annular surface of the main body concentric with the longitudinal axis, said annular surface comprising radial grooves each opening on one of the spray chambers closest to the head of the heating rod, the lower part of the screw head cooperating with the annular surface and said grooves to form a sealed cavity in communication with the vaporization chambers, said cavity receiving liquid fuel delivered by the central channel through said rod, and distributing this liquid fuel simultaneously in said chamber s vaporization. Preferably, the main body comprises an axial shaft placed in the extension of the inlet channel, receiving said rod of the screw, and an axial housing whose bottom is defined by said annular surface, said axial housing receiving the screw head. The second means preferably comprise a vaporized fuel injector, said injector comprising an annular base fixed axially to an end portion of the main body enclosing said vaporization chambers, and sealingly covering said end portion, and an axially overlying injection tube. said annular base, said tube comprising at least one radial orifice forming the outlet of the device.

The subject of the present invention is also the system for post-treatment of pollutant emissions in an exhaust line of a heat engine vehicle, comprising such a fuel vaporization device able to receive liquid fuel and to deliver vaporized fuel directly. in said exhaust line. The present invention also relates to the control method of a post-treatment system equipped with the spraying device. The present invention and the advantages it affords will be better understood from the following description of a vaporization device according to the invention equipping a system for post-treatment of pollutant emissions of a motor vehicle, made with reference to the appended figures. , in which: - Figures la and lb are exploded perspectives, respectively in top view and from below of a vaporization device according to a preferred embodiment of the invention; - Figure 2 is a partial sectional elevation of the device of Figures la and lb in the assembled position showing in detail the liquid fuel circuit inside the device; - Figure 3 is a top view in perspective of the main body of the spray device; - Figure 4 is a partial sectional elevation of the device in the assembled position showing in detail the vaporized fuel circuit inside the device; - Figure 5 illustrates an example of positioning of the spray device relative to the exhaust line. In the description which follows, we will focus on first describing the liquid fuel circuit of the vaporization device, that is to say the part of the device for conveying liquid fuel to the place vaporization, then, the vaporized fuel system, that is to say the part of the device for conveying the vaporized fuel to the exhaust line of the motor vehicle.

With reference to FIGS. 1a to 3, the vaporization device 1 according to the invention comprises a main body 10 comprising a plurality of housings 11, each housing 11 being intended to receive and hold a heating pencil 2 extending parallel to the axis longitudinal axis XX 'of the main body 10. In the preferred embodiment, these housings are three in number, preferably uniformly distributed around the longitudinal axis XX'. Nevertheless, the principle of the invention applies from two housings intended to receive two heating rods, these two housings being in this case preferably placed symmetrically with respect to the longitudinal axis XX '. The end portion 12 of the main body 10 intended to receive the active portion 20, that is to say heating, heating rods 2, comprises three cavities each extending a housing 11 along the longitudinal axis XX 'and intended to form, cooperation with the base 30 of a piece 3 forming a vaporized fuel injector which will be detailed later, three chambers 13 of vaporization. These three chambers 13 are intended to be fed simultaneously with liquid fuel. To do this, the main body 10 is supplied with liquid fuel at an inlet channel 14 extending preferably transversely, in particular orthogonally, to the longitudinal axis XX 'of the main body 10. As visible particularly in Figures 2 and 3, the main body 10 also has a central channel 15 extending along the longitudinal axis XX '. A first end of this central channel 15 is connected to one end of the inlet tube 14, and has a second end 15b opening at an axial shaft 16 of the end portion 12, located in the extension of the central channel 15. The end portion 12 comprises, at this level and above the axial shaft 16, an axial housing 17 of substantially cylindrical shape and of radial dimension greater than that of the axial shaft 16 (see more particularly Figure la and Figure 3). This axial housing 17 has a bottom defined by an annular surface 18 concentric with the axis XX '. The axial housing 17 and the axial shaft 16 are intended to receive respectively the head 40 and the rod 41 of a screw 4. More specifically, when the screw 4 is put in place in the spray device 1, the lower surface of the head 40 of the screw comes into contact with the annular surface 18, and the rod 41 is located in the axial shaft 16, in the extension of the central channel 15. The screw 4 can be fixed by screwing. In this case, the wall of the axial shaft 16 must be threaded to receive a corresponding thread present on the rod 41.

The rod 41 is further axially pierced at its center, and radially by at least one opening 42 formed just below the head 40 of screws. The opening 42 thus opens into a sealed annular cavity 19 formed by the axial housing 17, and more precisely by the annular surface 18, and the lower part of the screw head 40. The annular surface 18 finally comprises three radial grooves 18 'which have been machined to connect the second end 15b of the central pipe 15 to each of the chambers 13 of vaporization. Thus, the annular sealed cavity 19 is in communication with each of the vaporization chambers 13 via these three grooves. The operation of the device for the part corresponding to the liquid fuel circuit is therefore as follows: The vaporization device is first supplied with liquid fuel under pressure via the inlet channel 14. This can be done by means of a pump and a valve placed between the fuel tank and the inlet of the vaporization device, or via a dedicated injector. The liquid fuel then rises in the main body 10 through the central channel 15, passes through the inside of the rod 41 of the screw 4 to be directed towards the annular cavity 19 by means of the opening 42 or radially drilled openings in the rod 41. The annular cavity 19, formed between the base of the screw head 40 and the annular surface 18, supplies liquid fuel with the three grooves 18 'which in turn feed the three spray chambers 13 in which the heads are immersed. 2. The liquid fuel emerging from the grooves is then projected onto the heating heads 20 of the three rods 2 on which it comes to vaporize.

Thus, from a central body 10 for receiving a plurality of heating rods arranged parallel to the longitudinal axis XX 'of the body, different vaporization chambers can be simultaneously supplied with liquid fuel through the cooperation of various means allowing conveying the liquid fuel from the central channel 15 to each of the chambers, and more specifically: by the use of the screw 4 pierced axially at its stem 41 to extend the central channel 15; by the cooperation of the lower part of the screw head with the annular surface provided with its grooves for producing a sealed annular cavity in communication with the vaporization chambers, in which the liquid fuel coming from the central channel 15 and passing through the screw can spread, and consequently, be distributed uniformly and simultaneously in the spray chambers, closer to the heads of the heating rods. The inlet channel 14, the central channel 15, the housing 11, the cavities extending the housing 11 to form the vaporization chambers, the axial shaft 16, the axial housing 17, and the annular surface 18 provided with its grooves 18 are preferably all integral parts of the central body 10, in that it is a single piece. The design of the liquid fuel circuit in the vaporization device as just described makes it possible to obtain the seal at each groove 18 'by approaching the screw head on the annular surface 18. , the liquid fuel flow is defined by the distance separating the lower part of the screw head and the bottom of the grooves 18 '. Thus, it is possible to use the same spray device for different types of vehicles, simply by adapting this distance.

This can be done by simple reworking of the central body 10 of removing material. Thus, it is possible to machine the annular surface 18, which will have the effect of reducing the depth of the grooves, and consequently of reducing the flow rate. It is also possible to machine the grooves 18 'which will have the effect of increasing the depth of these grooves, and therefore of increasing the flow rate. The hydraulic diameter of the groove may be included as an example between 0.25 and 3 mm. The device is also very simple to manufacture: two parts (the central body 10 and the screw 4) are sufficient for the distribution of fuel in all vaporization chambers hosting the heads 20 of heating rods 2. The assembly s' By simply screwing the screw 4 into the body 10, the central body 10 can be easily adapted by multiplying the number of grooves according to the number of vaporization chambers to be fed. The part of the steam circuit of the vaporization device according to the preferred embodiment will now be described: This vapor circuit is intended to convey the vaporized fuel from the various previously described vaporization chambers 13 directly into the exhaust line 5 (FIG. see Figure 5). In the preferred embodiment, the vapor circuit is formed by the cooperation of the vaporized fuel injector part 3 with the main body 10 of the vaporization device, and more precisely with the end portion 12 of the body enclosing the chambers 13 of the vaporization. As can be seen in FIGS. 1a, 1b, 4 and 5, the vaporized fuel injector 3 comprises an annular base 30 of suitable shape for sealingly fixing and covering the end portion 12. In the example shown, the end portion 12 has a cylindrical outer casing, so that the annular base 30 also has a cylindrical outer casing adapted to be fitted axially on the end portion 12. An annular seal 6 preferably reinforces the seal of the together. The annular base 30 is fixed on the end portion 12 so as to leave a certain space between the inner wall 31 of the upper surface of the base 30 and the top of the vaporization chambers so as to allow the vaporized fuel in the chambers to invade the internal space of this base. The annular base 30 is surmounted by an injection tube 32 extending along the axis XX ', this tube being provided with at least one radial orifice 33 for the escape of the vaporized fuel into the line exhaust 5.

The internal space of the base 30 and the internal space of the tube 32 are in communication, so that the fuel vapor from the different chambers 13 progresses in the injector 3 via its base 30 and then opens into the line exhaust 5 by means of the orifices 33. As can be seen more particularly in FIG. 4, the passage section between the base 30 and the tube 32 advantageously has a trumpet-shaped profile 34 for limiting the pressure losses and promote the circulation of vaporized fuel. As can be seen in FIG. 5, the injection tube 32 advantageously also serves for fixing the device 1 for vaporizing fuel on the exhaust line 5. The number, the section and the position of the orifices 33 on the wall of the tube 32 depend on the targeted injection conditions. However, it will be preferred to direct the orifice 33 so that the fuel is vaporized against the current relative to the direction of exhaust gas in the exhaust line 5 (see Figure 5). An example of a control procedure of a post-treatment system comprising the fuel vaporization device 1, allowing very rapid fuel vaporization and increased durability, in particular for heating rods, will now be described: The control sequence begins preferably by preheating the heating rods for a predetermined time, for example of the order of 10 seconds.

The members (pump, valve, injector ...) of the system for delivering the liquid fuel to the inlet channel 14 of the device are then controlled to allow distribution of the liquid fuel at a nominal flow rate. In this way, the liquid fuel circuit of the vaporization device fills up very rapidly, typically in 2 or 3 seconds for a flow rate set at 0.25 g / s.

The fuel vaporization that follows results in a rise in richness in the exhaust line 5. It can be observed by the introduction into the system of a wealth probe (not shown) in the line 5. The measurement of this probe can thus be used to regulate the liquid fuel flow of the vaporization device, by controlling the pump or the aforementioned valve or injector, so as to achieve the desired richness in the line of exhaust. Thanks to the vaporization device according to the invention, very fast response times of the order of 2 or 3 seconds are obtained, and vaporisation cycles of much shorter duration than the times generally obtained with the devices of the invention. prior art (typically between 30 and 60 seconds). It should be noted that the preheating step of the heating elements advantageously allows rapid vaporization of the fuel remaining in each chamber 13 of vaporization at the time of heating of the heating rod by the limitation of its volume. In the case of this invention and for the intended application, the volume may be between 0.6 and 1.5 cm 3 and advantageously 0.95 cm 3. These values will be attained by varying the diameter, the depth and / or the shape of each chamber 13. However, the operation of heating the residual liquid fuel will preferably be avoided in order to limit the coking effects of the liquid fuel. To do this, just before stopping the spray device, it can be provided that each chamber 13 is emptied of its contents by maintaining the heating rods temperature for a few seconds while the liquid fuel supply is cut. In addition to the optimized response time, the fuel vaporization device 30 according to the invention makes it possible to deliver a fuel vapor flow rate adapted to the targeted applications. Indeed, the number of vaporization chambers and corresponding heating rods can be increased. This operation is possible thanks to the circular design of the vaporizer. In the case where it is desired to increase the number of vaporization chambers, it is sufficient to increase the diameter of the vaporization device. In addition, the design of the vaporizer device allows the mounting of heat rods from the trade. Indeed the spray device does not require heating rods of particular design. Advantageously, it will be preferable to choose short heating rods in order to reduce the bulk of the vaporizer. However, care should be taken to protect their electrical connections from strong temperature rises. Other improvements in the fuel spraying device, in the system comprising such a device and in its control method can be made further: Thus, to optimize the cooling of the heating rods during the use of the device, lights 7 (see FIGS. 1a and 5) are advantageously made in the main body 10, along the housings 11 receiving the heating rods 2. These lights 7 indeed allow air to circulate around the heating rods and limit the points of contact With the body 10. Advantageously, once mounted on the exhaust line, the air flowing under the vehicle will accentuate the cooling of the device. The lights 25 also make it possible to optimize the weight and the thermal mass of the device. In addition, as sized, the vaporizer can provide a fuel vapor flow rate of between 0.05 and 0.35 g / s. This flow rate is controlled by the control of the liquid fuel, as seen above, and by regulating the temperature of the vaporization chamber 13 by means of a thermocouple or other temperature measuring means (not shown) implanted into an orifice 8 practiced in the main body (see Figures lb and 4), and opening closer to the active portion of the heating rods. The regulation by the thermocouple makes it possible to guarantee the temperature necessary for the vaporization of the liquid fuel but also to control the power supply of the heating rods and to inject the electric power just necessary. The energy management law can be defined to cut the power supply of the heating rods when the temperature is above a set temperature. This regulation also has the advantage of preserving the integrity of the system by prohibiting an excessive rise in temperature. This temperature can be between 270 and 400 ° C and for example be fixed at 320 ° C. This setpoint temperature ensures complete fuel vaporization at around 240 ° C. At the end of each vaporization, the heating rods can be kept warm for 10 seconds or until reaching 320 ° C (T set point) so as to empty the liquid fuel from the vaporization chambers. This operation therefore contributes to the durability of the device since it avoids the coking phenomena of the liquid fuel during the heating of the heating rods.

Claims (16)

REVENDICATIONS1. Device (1) for fuel vaporization intended to equip a system for post-treatment of pollutant emissions in an exhaust line (5) of a motor vehicle with a heat engine, the device being able to receive liquid fuel and having an orifice of outlet (33) opening directly into said exhaust line (5), capable of delivering vaporized fuel, characterized in that it comprises: - a main body (10) comprising at least two housings (11) each intended to receive and maintaining a heating rod (2) extending parallel to the longitudinal axis (XX ') of said main body (10), an inlet channel (14) for receiving liquid fuel, and a central channel (15) extending along the longitudinal axis (XX ') for conveying the liquid fuel received by the inlet channel (14) of the device; two vaporization chambers (13) each extending one of the two housings (11), each vaporization chamber being able to receive the active part (20) of the corresponding heating rod; first means (4, 18, 18 ') for simultaneously distributing the liquid fuel conveyed via the central channel (15) to each of the two vaporization chambers; and second means (3, 12) for conveying the vaporized fuel from the vaporization chambers to the outlet orifice (33). 2. Device (1) according to claim 1, characterized in that it comprises more than two housings (11), each being adapted to receive and maintain a heating rod (2) extending parallel to the longitudinal axis (XX). ') of said main body (10), and a corresponding number of vaporization chambers (13) each extending a housing for receiving the active part (20) of a corresponding heating rod (2), and in that said first means are adapted to simultaneously distribute the liquid fuel conveyed through the central channel (15) to each of the vaporization chambers. 3. Device according to claim 2, characterized in that the housing and the evaporation chambers which extend are distributed uniformly about the longitudinal axis of the main body. 4. Device according to any one of the preceding claims, characterized in that said first means (4, 18, 18 ') comprise firstly, a screw (4) having a head (40) of screw and a rod ( 41) placed along the longitudinal axis (XX ') of the main body (10) in the extension of the central channel (15), said rod (41) being pierced axially at its center and radially by at least one opening (42) in below the screw head, and on the other hand, an annular surface (18) of the main body (10) concentric with the longitudinal axis (XX '), said annular surface (18) comprising radial grooves (18') each opening on one of the chambers (13) of vaporization closer to the head of the heating rod, the lower portion of the head (40) of the screw cooperating with the annular surface (18) and said grooves (18 ') to form a sealed cavity in communication with the vaporization chambers (13), said cavity receiving liquid fuel delivered through the central channel (15) via said rod (41), and distributing this liquid fuel simultaneously in said vaporization chambers (13). 5. Device according to claim 4, characterized in that the main body (10) comprises an axial shaft (16) located in the extension of the inlet channel, receiving said rod (41) of the screw (4), and a axial housing (17) whose bottom is defined by said annular surface (18), said axial housing (17) receiving the head (40) of screws. 6. Device according to any one of the preceding claims, characterized in that the main body (10) comprises slots (7) along the housings (11) receiving the heating rods (2), to allow air circulation around said heating rods (2). 7. Device according to any one of the preceding claims, characterized in that the main body (10) comprises an orifice (8) opening as close as possible to the active portion (20) of the heating rods to allow the passage of a means. temperature measurement. 8. Device according to any one of the preceding claims, characterized in that said second means (3, 12) comprise an injector (3) of vaporized fuel, said injector comprising an annular base (30) axially fixed to an end portion ( 12) of the main body (10) enclosing said vaporization chambers (13), and sealingly covering said end portion (12), and an injection tube (32) axially overlying said annular base (30), said tube comprising at least one radial orifice forming the outlet orifice (33) of the device. 9. Device according to claim 8, characterized in that the passage section between the annular base (30) and the injection tube (32) has a trumpet-shaped profile. 10. Device according to any one of claims 8 or 9, characterized in that the tube (32) of injection is adapted to serve as means for fixing the device on said line (5) exhaust. 11. A system for post-treatment of pollutant emissions in an exhaust line (5) of a heat engine vehicle, comprising a device (1) for vaporizing fuel capable of receiving liquid fuel and delivering vaporized fuel directly into the engine said exhaust line (5), characterized in that the fuel vaporization device (1) is according to any one of the preceding claims. 12. System according to claim 11, characterized in that it comprises a pump-type organ and valve or injector capable of being controlled to deliver liquid fuel under pressure on the inlet channel (14) of the device (1). fuel vaporization. 13. System according to claim 12, characterized in that it comprises a richness sensor in the line (5) exhaust, the measurement of this probe for controlling said member to regulate the flow of liquid fuel. 14. System according to any one of claims 11 to 13, characterized in that it comprises a temperature measuring means for controlling the power supply of the heating rods (2). 15. The method of controlling a post-treatment system according to claim 14, characterized in that it comprises: a step of heating the heating rods (2); a step of controlling said member to allow a distribution of liquid fuel at a nominal flow rate. 16. Control method according to claim 17, characterized in that it further comprises a step in which the heating rods are maintained in temperature while the liquid fuel supply is cut.