FR2904361A1 - Fuel vaporization device for road vehicle`s oil engine exhaust line, has vaporizer supplied with fuel by low pressure stage, where fuel is removed from sector of injection circuit and contacts, at pulverized liquid state, heating element - Google Patents

Abstract

The device (1) has a vaporizer (9) supplied with fuel by a low pressure stage of a common injection pump (3) of a common rail high-pressure injection engine. The vaporizer has an outlet tube (10) emerging into an exhaust line (2) of the engine. The fuel is removed from a pressurized sector (8) of a fuel injection circuit of the engine and contacts, at pulverized liquid state, a heating element e.g. heater plug, of the vaporizer.

Description

- 1 - DEVICE FOR VAPORIZING FUEL IN AN EXHAUST LINE

  The invention is in the field of the depollution of combustion engines internal combustion equipping road vehicles, including diesel engines. More specifically, this invention relates to a fuel vaporization device in a common rail injection line of pressure injection, comprising a vaporizer fueled, the vapor outlet of which opens into the exhaust line of the engine . Such a device makes it possible in particular to vaporize fuel in a heat engine exhaust line with or without a particulate filter (FàP). The invention aims in particular to improve the regeneration of particulate filters by the introduction of reducers in the exhaust line, and finds an application possible on any vehicle equipped with a diesel after-treatment system FàP or NOx-trap. Particle filters are generally preceded or associated with a catalyst, making it possible to oxidize the reducing agents, such as HC and CO present in the exhaust gases. The initialization and the maintenance of the regeneration of the filter, are obtained by raising the internal temperature of this one. In order to obtain the necessary heat, it is possible to use the catalyst generally placed upstream of the FAP to reduce hydrocarbons and nitric oxide. A first method to trigger or facilitate the regeneration of particulate filters is to make late fuel injections into the cylinder. The late injected fuel does not burn in the cylinder, but is oxidized in the catalyst, and this exothermic reaction promotes the regeneration of the APF. However, some of the late injected fuel mixes with the oil on the barrels of the cylinders, and causes significant dilution of the gas oil in the oil, with a very detrimental effect on the reliability of the engine. To avoid this drawback, a second method consists in placing a fuel injector in the exhaust line, and injecting liquid fuel into the exhaust line upstream of the oxidation catalyst, to obtain the same exothermic reaction that with late injections.

  The fuel injected at the exhaust vaporizes, and is driven by the exhaust gas to the oxidation catalyst, while mixing with them: the more the mixture of fuel in the exhaust gas is homogeneous before the catalyst entry, the more the oxidation reaction within it is homogeneous, and the temperature of the gas input filter is homogeneous. In practice, the injection of liquid fuel into the exhaust line, results in the creation of a film on the wall thereof. The fuel then vaporizes due to the temperature of the gases. But the distance between the vaporization zone and the inlet of the catalyst is sometimes insufficient to have a homogeneous mixture at the catalyst inlet, in particular due to the agitation of the exhaust gas.

  It was thus possible to highlight, by simulation, areas of higher richness propagating along the exhaust line. Such areas, which are richer in fuel, locally cause higher temperatures in the catalyst, which can lead to premature wear of the catalyst.

A third method, illustrated by the publication EP 1 643 092 is to introduce the fuel in the form of steam in the exhaust line, to improve its mixing with the gases. According to this publication, the fuel 5 is heated to its vaporization temperature prior to introduction into the exhaust gas. The fuel spraying system comprises a hydraulic pump collecting liquid fuel in the fuel tank of the vehicle, and an electric heating plug, which vaporizes the fuel, before it is introduced into the exhaust line. The present invention aims to simplify such a system, in particular by removing its hydraulic pump. For this purpose, it proposes that the fuel be taken from a pressurized sector of the engine fuel injection circuit, and that it comes into contact in the liquid state sprayed with a heating element of the vaporizer. According to one embodiment of the invention, the vaporizer is fed from the common injection pump 20 of the engine, preferably by a low pressure stage thereof. Other features and advantages of the present invention will become apparent from the following description of a non-limiting embodiment thereof, with reference to the accompanying drawings, in which: - Figure 1 is a diagram overall of the proposed device, and - Figure 2 illustrates a non-limiting embodiment of the vaporizer used. FIG. 1 shows a fuel vaporization system 1, in the exhaust line 2 of a vehicle, equipped with a common rail high-pressure common-rail injection engine (not shown). The injection pump 3 feeding the common ramp comprises a high pressure stage 4 (HP pump) and a low pressure stage 6 (BP pump). A supply line 7, connected to the pump 3 by a connector with nozzle 8 connects it to a vaporizer 9 (detailed in Figure 2) 5 which opens into the exhaust line 2 through an outlet cannula 10. FIG. 1 also shows a solenoid valve 12 controlling the supply of fuel to a fuel injector 11 in the vaporizer 9. The solenoid valve 12 is a shutoff solenoid valve 10 (operating safety) and no dosage , this last function being integrated in the injector 11. FIG. 2 shows a nonlimiting example of implantation of the injector 11 on the housing 12 of the vaporizer 9. The injector 11 is fed by the line 7 of FIG. 1, resulting from the output passes pressure of the pump 3. The fuel sprayed in the spray chamber 16, meets the heating element 14. The fuel jet preferably has a conical shape. The candle has a superficial temperature sufficiently high to vaporize the fuel. It is powered for example by a controlled voltage of 12 Volt, and is engaged during the regeneration phases of FàP. The amount of fuel injected is controlled in a closed loop to achieve a temperature target at the input of the FAP. The vaporized fuel is introduced through the outlet cannula 16 of the housing 11 into the exhaust line 2, where it mixes rapidly with the exhaust gas. The injector 11 may be of any type, for example an injector of the type used on direct injection gasoline engines, or of a particular type. A diesel engine glow plug is suitable for vaporizing the fuel in the vaporizer 9, but without departing from the scope of the invention, it is possible to use other types of heating elements 12 of less expensive technology because the desired temperature level is relatively low. Finally, the housing 12 and the cannula 10 of the vaporizer, can be made in mechano-welding. In summary, the invention provides for integrating the functions of metering and vaporizing the fuel in the same component, such as the vaporizer described above. The preferred solution of using a gasoline type injector to bring fuel to the spark plug has many advantages. First, the injector 10 can operate with sufficiently high pressure levels (of the order of seven bar) and can use the fuel from the low pressure stage of the common rail pump. In addition, it is he who assures the dosage of the fuel, without other metering element on the supply line of the vaporizer. Finally, the arrival of the fuel in spray form on the surface of the candle, allows to lower the surface temperature thereof, which reduces its power consumption or use candles 20 cheaper than glow plugs Diesel.

Claims (10)

  A fuel-spraying device in a common-rail pressure-injection engine exhaust line comprising a fuel-fed vaporizer (9), the vapor outlet (14) of which discharges into the exhaust line (2). ) of the engine, characterized in that the fuel is taken from a pressurized sector (8) of the engine fuel injection circuit, and that it comes into contact in the pulverized liquid state with a heating element ( 14) of the vaporizer (9).   2. Spray device according to claim 1 or 2, characterized in that the vaporizer (11) is fed from the common injection pump (7) of the engine.   3. Spraying device according to claim 2, characterized in that the vaporizer (9) is fed by a low pressure stage of the common injection pump (8) of the engine.   4. Spray device according to claim 1, 2 or 3, characterized in that the fuel is sprayed into the vaporization chamber (16) of the vaporizer (9) by a fuel injector (11).   5. Spray device according to claim 4, characterized in that the supply of the injector (11) is controlled by a shutoff solenoid valve (12).   6. Spray device according to claim 4 or 5, characterized in that the injector (11) directly sprays the fuel on the heating element (14) of the vaporizer (9).   7. Spraying device according to one of the preceding claims, characterized in that the heating element (14) is activated during the regeneration phases 2904361 7 of a particulate filter disposed in the exhaust line of the engine.   8. Spray device according to one of claims 4 to 7, characterized in that the amount of fuel injected into the vaporization chamber (16) is adjusted in a closed loop to reach the desired temperature at the inlet of the filter. particles.   9. Spraying device according to one of the preceding claims, characterized in that the vaporized fuel is introduced into the exhaust line (2) through an outlet cannula (10) of the vaporizer (9). Spraying device according to one of the preceding claims, characterized in that the heating element (14) is a spark plug of the type of preheating of diesel engines.