FR2900964A3 - EXHAUST LINE COMPRISING A FUEL INJECTION LINE AND A LINE FOR BLOWING AIR OR BURNING GASES - Google Patents

Abstract

The invention generally relates to an internal combustion engine (10) comprising an exhaust line (30) for burnt gases provided with means for decontaminating (50) and filtering (51) said gases, and an injection line (60) of fuel emerging in the exhaust line upstream of the pollution control and filtering means of the burnt gases.According to the invention, the internal combustion engine comprises means for blowing (70, 71) air or flue gas in the exhaust line upstream of said pollution control and filtering means.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention

  generally relates to internal combustion engines. It relates more particularly to an internal combustion engine comprising a burnt gas exhaust line provided with means of depollution and filtering of said gases, and a fuel injection line opening into the exhaust line upstream of the depollution means. and filtering the flue gases. TECHNOLOGICAL BACKGROUND The exhaust lines of internal combustion engines are generally provided with means for depollution and filtering of flue gases. These depollution and filtering means usually comprise a catalyst and a particulate filter. The particulate filter in particular makes it possible to recover a large part of the pollutant particles emitted by the combustion of the mixture of fresh air and fuel in the combustion chamber of the engine. From a certain degree of filling of the particulate filter, its efficiency decreases sharply. It is then necessary to eliminate the particles that fill the particulate filter without rejecting them as such in the atmosphere. For this, we proceed to a regeneration phase of the particulate filter which is to inject fuel into the exhaust line, resulting in an exothermic oxidation phase in the catalyst. The exhaust gases then leave the catalyst with a very high temperature and enter the particulate filter by burning the polluting particles that fill the latter.

  Generally, in order to be able to implement this regeneration phase, a fuel injection line is opened in the exhaust line upstream of the catalyst, which makes it possible to inject the fuel into the flue gas stream. It is understood that the mixture of burnt gases and fuel must be homogeneous so that the oxidation and combustion of the polluting particles are carried out correctly. However, with such a fuel injection line, only a portion of the fuel disperses directly into the flue gas stream. The remaining portion of the fuel impacts the inner wall of the exhaust line and creates a layer of fuel flowing along the wall partially evaporating. The evaporated portion of the fuel furthermore does not mix well with the flue gas stream, but remains concentrated near the inner wall of the exhaust line, which decreases the efficiency of the regeneration of the particulate filter.

  To prevent such a layer of fuel from forming on the inner wall of the exhaust line, US 6 843 966 proposes an internal combustion engine comprising a bypass line originating in the exhaust manifold and opening into the exhaust manifold. the exhaust line, upstream of the particulate filter. According to this document, the fuel injection line opens into this bypass line so that the fuel and the flue gases are mixed more homogeneously when they enter the particulate filter. However, such a device does not prevent the formation of a fuel layer in the bypass line, which poses problems equivalent to those previously mentioned. The document WO 2005 071235 proposes an internal combustion engine for reducing the amount of fuel impacting the inner wall of the exhaust line. It comprises for that two fuel injectors positioned in the exhaust line vis-à-vis one another. Thus, the two fuel streams coming out of the fuel injectors impinge on each other, which promotes the dispersion of the fuel in the flue gases and prevents the formation of a layer of fuel on the inner wall of the fuel. the exhaust line. The main disadvantage of such an internal combustion engine is that it requires the expensive use of two fuel injectors and two bulky fuel injection lines bringing the fuel into the exhaust line at pressures substantially equal. OBJECT OF THE INVENTION In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a less expensive internal combustion engine that promotes the vaporization of the fuel and its homogenization with the flue gases. More particularly, it is proposed according to the invention an internal combustion engine as defined in the introduction, wherein there is provided air blowing means in the exhaust line upstream of said pollution control and filtering means. Thus, thanks to the invention, the blown air creates swirling movements in the exhaust line which homogenize the fuel and the flue gases before they enter the catalyst and the particulate filter. If the blowing means blow the air in the exhaust line upstream of the mouth of the injection line, these swirling movements promote the dispersion of the fuel droplets in the flue gas stream, which avoids that too much fuel impacts the inner wall of the exhaust line. On the other hand, if the blowing means blow the air in the exhaust line downstream of the mouth of the injection line, these swirling movements allow the layer of fuel to be spread over a larger surface area, which increases the evaporation rate of the fuel.

  According to a first advantageous characteristic of the internal combustion engine according to the invention, the blowing means comprise means for regulating the flow of air blown into the exhaust line. Thus, the blowing means can be activated only during the regeneration phase of the particulate filter, so that they do not influence the operation of the internal combustion engine during its other operating phases. Advantageously, the blowing means blow the air in the exhaust line downstream of the mouth of the injection line in the exhaust line.

  According to a first embodiment of the invention, the internal combustion engine comprising a combustion chamber in which open the exhaust line and a fresh air intake line, the blowing means comprise a blowing line which takes birth in the admission line.

  Advantageously then, the intake line comprises a compressor, the exhaust line comprises a turbine, and the blowing line originates in the intake line downstream of the compressor and opens into the exhaust line downstream of the engine. turbine.

  Thus, the blown air consists of compressed fresh gases at a pressure greater than the pressure of the flue gases circulating in the exhaust line, so that the vortex movements have an intensity sufficient to substantially improve the homogenization and vaporization fuel in the flue gases. According to a second embodiment of the invention, the exhaust line comprises a turbine, and the blowing means comprise a blowing line which originates in the exhaust line upstream of the turbine and which opens into the line exhaust outlet downstream of said turbine.

  Thus, since the pressure of the flue gases flowing in the exhaust line upstream of the turbine is greater than that of the flue gases circulating in the exhaust line downstream of the same turbine, the vortex movements generated by the blown air present here also an intensity sufficient to significantly improve the homogenization and vaporization of the fuel in the flue gas. According to a third embodiment of the invention, the blowing means comprise a compressor compressing the air at a pressure greater than the pressure of the flue gases. According to another advantageous characteristic of the internal combustion engine according to the invention, the blowing means blow the air in the exhaust line along an inclined axis, on the one hand, with respect to the axis of the line d exhaust, and, secondly, with respect to the normal to the exhaust line in the plane transverse to the axis of said exhaust line. Thus, the air being blown along an axis inclined relative to the axis of the exhaust line, it does not cause losses of burner gas that would be detrimental to engine performance. Moreover, the air being blown along an axis inclined relative to the normal to the exhaust line, the air is blown tangentially to the inner wall of the exhaust line which causes the formation of vortices axis confused with the axis of the exhaust line. Advantageously, the blowing means comprise means for heating the air.

  Thus, the fuel that has settled on the inner wall of the exhaust line vaporizes more rapidly, so that the mixture of fuel and flue gas is perfectly homogeneous as it enters the catalyst. According to another advantageous characteristic of the internal combustion engine according to the invention, the blowing means comprise a blowing line divided, at least in part, into separate channels opening into the exhaust line. Advantageously then, the channels open into the exhaust line along inclined axes relative to each other.

  Thus, each channel is adapted to generate a type of vortices having characteristics different from those of vortices generated by the other channels, which promotes the overall homogenization of the flue gas and fuel flow. Advantageously, the injection line comprises a compressor and, at its mouth in the exhaust line, a fuel injector. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description with reference to the accompanying drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: - Figure 1 is a schematic overview of a first embodiment of an internal combustion engine according to the invention; FIG. 2 is a cross-sectional view of the exhaust line and the blowing line of the internal combustion engine of FIG. 1; - Figure 3A is a longitudinal sectional view of the exhaust line and the blow line of the internal combustion engine of Figure 1; - Figure 3B is a longitudinal sectional view of an alternative embodiment of the exhaust line and the blow line of the internal combustion engine of Figure 1; - Figure 3C is a cross-sectional view of an alternative embodiment of the exhaust line and the blow line of the internal combustion engine of Figure 1; FIG. 4 is a schematic overview of a second embodiment of the internal combustion engine according to the invention; and FIG. 5 is a schematic overview of a third embodiment of the internal combustion engine according to the invention.

  As a preliminary, it will be noted that, from one figure to another, the identical or similar elements of the different embodiments of the invention will, as far as possible, be referenced by the same reference signs and will not be described. Everytime. In the description, the terms downstream and upstream are used in the direction of the flow of air from the point of sampling of fresh air into the atmosphere until it is discharged by means of depollution and filtering. FIG. 1 shows an internal combustion engine 10 which comprises a combustion chamber 11 defined by four cylinders 12. Upstream of the combustion chamber 11, the internal combustion engine 10 comprises an intake line 20 'fresh air. This intake line 20 draws fresh air directly into the atmosphere and the filter by means of an air filter 22. It extends to an air distributor 21 which opens onto four intake channels 21A each connected to one of the cylinders 12 of the combustion chamber 11.

  Of course, alternatively, the air distributor could be connected to each cylinder by two intake channels, in the case of a sixteen-valve engine. The intake line 20 further comprises a compressor 42 of a turbocharger 40 compressing the fresh air. This compressed fresh air, and thus heated, is then injected under pressure into the air distributor 21. Downstream of the combustion chamber 11, the internal combustion engine 10 comprises an exhaust line 30 of burnt gases extending an exhaust manifold 31, connected by four exhaust channels 31A to each of the cylinders 12 of the combustion chamber 11, to depollution and filtering means 50, 51 constituted by a catalyst 50 and a filter In the case of a sixteen-valve engine, the exhaust manifold is connected to each cylinder by two exhaust channels.

  The exhaust line 30 further comprises, upstream of the catalyst 50, a turbine 41 of the turbocharger 40 intended to actuate the compressor 42. In a manner known per se, the flow rates of fresh air and flue gas entering and leaving the combustion chamber 11 are regulated by intake and exhaust valves. Here, the internal combustion engine 10 comprises an intake valve and an exhaust valve per cylinder 12 respectively disposed in the intake channel 21A of said cylinder and in its exhaust channel 31A.

  In the case of a sixteen valve engine, the internal combustion engine comprises two intake valves and two exhaust valves per cylinder. The opening of the intake valves makes it possible to inject fresh air into the cylinders 12 and the opening of the exhaust valves makes it possible to evacuate towards the exhaust line 30 the burnt gases resulting from the combustion of the fuel. Fresh air and fuel contained in the cylinders 12. As shown in FIG. 1, the internal combustion engine 10 also comprises a fuel injection line 60 opening into the exhaust line 30, between the turbine 41 of the turbocharger 40 and the catalyst 50. This injection line 60 comprises a compressor 62 adapted to take fuel from a tank 61 to inject it under pressure into the exhaust line 30. The compressor 62 may for example be that used to injecting the fuel into the cylinders 12 of the combustion chamber 11 under pressure.

  As shown in Figures 3A and 3B, the injection line 60 further comprises a fuel injector 63 disposed at the mouth of the injection line 60 in the exhaust line 30 along an axis inclined relative to the W axis of the latter, so that the fuel is injected in the direction of the flow of flue gases to better disperse in the gas flow.

  This fuel injector 63 is controlled by control means (not shown) of the internal combustion engine 10 for injecting at the desired time the desired amount of fuel in the exhaust line 30. The fuel injector 63 is here of a type identical to that of the injectors commonly used for the combustion of the mixture of fuel and fresh air in the combustion chamber 11. According to a particularly advantageous characteristic of the invention, the internal combustion engine 10 comprises means of blowing 70 adapted to inject the air blown into the exhaust line 30 at a pressure greater than the pressure of the gases flowing in the latter. As shown more particularly in FIG. 1, these blowing means here consist of a blowing line 70 which originates in the intake line 20, between the compressor 42 of the turbocompressor 40 and the air distributor 21, and which opens into the exhaust line 30, between the mouth of the injection line 60 in the exhaust line 30 and the catalyst 50. The blowing line 70 comprises means for regulating the flow of blown air such that a valve 71 disposed at the junction between the air intake line 20 and the blowing line 70. This valve 71 may for example be a butterfly valve. Anyway it is controlled by the motor control means and is adapted to modulate the flow of air blown through the blowing line 70 and opening into the exhaust line 30. regulation of the blown air flow may comprise an air injector disposed at the mouth of the blowing line 70 in the exhaust line 30. This air injector may for example have an architecture identical to that of a fuel injector, well known to those skilled in the art. The blowing line may also comprise heating means (not shown) for the blown air comprising, for example, a winding of a part of the blowing line 70 around the exhaust line 30. This winding thus makes it possible to reheat the fresh air taken from the intake line 20 before injecting it into the exhaust line 30. As shown more particularly in FIGS. 2 and 3A, the blowing line 70 opens into the exhaust line 30 along an axis V having a double inclination with respect to the axis W of the exhaust line 30. As shown in Figure 3A, the axis V of the blowing line 70 is first inclined relative to the W axis of the exhaust line 30 in the longitudinal plane having the axis W and the junction point between the blowing line 70 and the exhaust line 30. It is more particularly inclined with a longitudinal angle Al included between -10 and +170 degrees. As shown in FIG. 2, the axis V of the blowing line 70 is further inclined relative to the normal N to the outer wall of the exhaust line 30, in the transverse plane which is orthogonal to the axis W and which passes through the junction point between the blowing line 70 and the exhaust line 30. It is more particularly inclined by an angle A2 called tangency angle between -80 and +80 degrees. Thus, the air blowing into the exhaust line 30 is directed tangentially against the inner wall of this line, in the direction of the flue gas flow, so that it has a helical movement favoring the homogenization of the flue gas and fuel injected into the exhaust line 30 through the injection line 60. In a variant and as shown in FIGS. 3B and 3C, the blowing line 70 may have an end divided into several channels, here two channels 70A, 70B, opening into the exhaust line 30 at different points. These different channels 70A, 70B are, as shown in Figure 3B, arranged next to each other.

  These two channels 70A, 70B are adapted to inject the blown air along axes V1, V2 having different longitudinal angles B1, B2, so as to generate helical movements having different characteristics. As illustrated in FIG. 3C, the channels 70A, 70B may also open into the exhaust line 30 at points having different angular positions around the W axis. These angular positions can be separated by an angle D between 0 and 360 degrees. The channels 70A, 70B may further open along axes V1, V2 with different tangency angles C1, C2, in order to generate in the exhaust line 30 a vortex movement commonly called swirl. When the internal combustion engine 10 is running, the fresh air is drawn into the atmosphere through the intake line 20 and then compressed into the compressor 42 of the turbocharger 40.

  During a normal engine operation phase, the valve 71 of the blower line 70 remains in the closed position, and the entire flow of fresh air drawn and compressed follows the intake line 20 and opens into the distributor of air 21 to be burned in the combustion chamber 11.

  On the other hand, during a regeneration phase of the particulate filter 51, the engine control means control the opening of the valve 71 and the injector 63. Only a part of the fresh air taken and compressed follows the intake line 20 and opens into the air distributor 21. The other part of this fresh air, the air blown, is captured by the blower line 70 downstream of the compressor 42. This blown air, whose temperature has increased due to the compression that it has undergone and thanks to the heating means of the blowing line 70, opens into the exhaust line 30. Moreover, the injection line 60 projects fuel particles into the burned gases circulating in the exhaust line 30. Part of these particles mix directly with the flow of flue gas while another part is deposited on the inner wall of the exhaust line 30 and flows along this wall towards the catalyst 50. A port This fuel flowing on the hot walls of the exhaust line 30 vaporizes in the flue gas stream.

  When the remaining portion of the fuel flowing on the wall arrives at the mouth of the blast line 70, the hot swirling air flow created by the blown air causes the fuel to spread on the wall interior of the exhaust line 30, which accelerates the vaporization of the fuel.

  In addition, these air vortices homogenize the mixture of fuel and flue gases so that they can effectively treat the pollutant particles that fill the particulate filter 51 by burning and ejecting them to the atmosphere. When the regeneration is complete, the control means of the internal combustion engine 10 control the obstruction of the injector 63 of the injection line 60 and the closing of the valve 71 of the blowing line 70. According to a second embodiment embodiment of the internal combustion engine 10 according to the invention shown in Figure 4, the blowing line 72 originates in the exhaust line 30, between the exhaust manifold 31 and the turbine 41 of the turbocharger 40. Thus, the pressure of the blown air is equal to the pressure of the flue gases circulating upstream of the turbine 41, so that the pressure of the blown air is greater than the pressure of the flue gases flowing downstream of the turbine 41.

  According to this embodiment, the blowing line 72 also comprises means for regulating the flow of blown air constituted here by a throttle valve 73 controlled by the engine control means. According to a third embodiment of the internal combustion engine 10 according to the invention shown in FIG. 5, the blast line 74 draws fresh air directly into the atmosphere and compresses it to a pressure greater than the pressure of the flue gases. circulating in the exhaust line 30 by means of a compressor 75, and injected into this exhaust line. According to this embodiment, the compressor 75 is here coupled to an electric motor driven by the motor control means, so that this assembly formed by the motor and the compressor 75 constitutes the means for regulating the flow of circulating air. In the blowing line 74. The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind.20

Claims (12)

  An internal combustion engine (10) comprising a burnt gas exhaust line (30) provided with means for the depollution (50) and filtering (51) of said gases, and a fuel injection line (60) opening in the exhaust line (30) upstream of the pollution control (50) and filtering means (51) of the flue gas, characterized in that it comprises blowing means (70, 71 72, 73; ) air or flue gas in the exhaust line (30) upstream of said pollution control means (50) and filtering means (51).   2. Internal combustion engine (10) according to the preceding claim, characterized in that the blowing means (70, 71; 72, 73; 74, 75) comprise regulating means (71; 73; blown air or flue gas blown into the exhaust line (30).   3. Internal combustion engine (10) according to one of the preceding claims, characterized in that the blowing means (70, 71; 72, 73; 74, 75) blow the air or the flue gases in the line of combustion. exhaust (30) downstream of the mouth of the injection line (60) in the exhaust line (30).   Internal combustion engine (10) according to one of the preceding claims, characterized in that the internal combustion engine (10) comprises a combustion chamber (11) into which the exhaust line (30) and an intake line (20) of fresh air, the blowing means (70, 71) comprise a blowing line (70) which originates in the intake line (20).   5. Internal combustion engine (10) according to the preceding claim, characterized in that the intake line (20) comprises a compressor (42), the exhaust line (30) comprises a turbine (41), and the blow line (70) originates in the intake line (20) downstream of the compressor (42) and opens into the exhaust line (30) downstream of the turbine (41).   6. Internal combustion engine (10) according to one of claims 1 to 3, characterized in that the exhaust line (30) comprises a turbine (41), and the blowing means (72, 73) comprise a blow line (72) which originates in the exhaust line (30) upstream of the turbine (41) and which opens into the exhaust line (30) downstream of said turbine (41).   7. Internal combustion engine (10) according to one of claims 1 to 3, characterized in that the blowing means (74, 75) comprise a compressor (75) compressing the air at a pressure greater than the pressure of the burnt gas.   8. Internal combustion engine (10) according to one of the preceding claims, characterized in that the blowing means (70, 71; 72, 73; 74, 75) blow the air or the flue gases in the line d exhaust (30) along an axis (V) inclined, on the one hand, with respect to the axis (W) of the exhaust line (30), and, on the other hand, with respect to the normal ( N) to the exhaust line (30) in the plane transverse to the axis (W) of said exhaust line (30).   9. Internal combustion engine (10) according to one of the preceding claims when the latter is not related to claim 6, characterized in that the blowing means (70, 71; 72, 73; 74, 75). include means for heating the air.   10. Internal combustion engine (10) according to one of the preceding claims, characterized in that the blowing means (70, 71) comprise a blowing line (70) divided, at least in part, into channels (70A , 70B) opening into the exhaust line (30).   11. Internal combustion engine (10) according to the preceding claim, characterized in that the channels (70A, 70B) open into the exhaust line (30) along axes (VI, V2) inclined relative to each other .   12. Internal combustion engine (10) according to one of the preceding claims, characterized in that the injection line (60) comprises a compressor (62) and, at its mouth in the exhaust line (30). ), a fuel injector (63).