EP2076659B1 - Exhaust line fitted with a fuel injector and means for homogenizing burnt gases - Google Patents

Abstract

The invention relates to an exhaust line (40) of an internal combustion engine comprising an exhaust duct (43) for the burnt gases and a fuel injector (53) giving into said exhaust duct. According to the invention, a plurality of flat vanes (101, 102, 103, 104) are provided in the exhaust duct (43) so that one face of each vane (101, 102, 103, 104) receives a portion of the fuel (54) jet from said fuel injector (53).

Description

TECHNICAL FIELD TO WHICH THE INVENTION REFERS

The present invention generally relates to internal combustion engines provided with means for filtering flue gases.

It relates more particularly to an exhaust line of an internal combustion engine having a burnt gas exhaust pipe and a fuel injector opening into said exhaust pipe.

The invention finds a particularly advantageous application in the production of diesel engines and spark ignition engines operating at low richness.

BACKGROUND

The exhaust pipes of internal combustion engines are generally provided with an oxidation catalyst followed, in the flow direction of the flue gases, with a particulate filter.

The oxidation catalyst is designed to oxidize hydrocarbons and carbon monoxide from the combustion of fuel and fresh air into the combustion chamber to prevent their being released into the atmosphere. The particulate filter allows to filter and store a large part of the polluting particles (soot) rejected by the engine.

From a certain degree of filling of the particulate filter, the flue gas evacuates with difficulty from the exhaust pipe, which generates an overpressure of the flue gas which is detrimental to the operation of the internal combustion engine.

During a phase of regeneration of the particulate filter, it is then necessary to eliminate the polluting particles which fill the filter without, however, rejecting them as such in the atmosphere, but rather by burning them beforehand.

For this, fuel is injected into the exhaust line, resulting in a highly exothermic oxidation reaction of the fuel in the oxidation catalyst. The flue gases therefore exit the oxidation catalyst with a high temperature and enter the particulate filter by burning the pollutant particles that fill the particulate filter.

It is known, for performing this regeneration phase of the filter, to have a fuel injector so that it opens into the exhaust pipe, perpendicularly to the average line along which the latter extends. The fuel thus injected is then sprayed on the inner face of the exhaust pipe, then flows along the pipe partially evaporating before entering the oxidation catalyst. The mixture of flue gas and fuel is therefore not homogeneous. As a result, the oxidation reactions mainly take place near the walls of the oxidation catalyst, which risks damaging it and reducing its performance prematurely. The difficulty therefore consists in controlling the evaporation of the fuel and its homogenization in the flue gases in order to optimize the combustion of the polluting particles and not to discharge hydrocarbons into the atmosphere.

The document JP 61164017 proposes a fuel injector positioned in an exhaust pipe, which is adapted to modify the direction of the jet of fuel that it projects into the pipe. Thus, the fuel injector can optimize the distribution of fuel in the flue gas stream according to the speed of the latter. However, this device requires the expensive use of an ad hoc fuel injector and does not accelerate the evaporation rate of the fuel in the flue gas.

The documents JP 09317440 and US 6539708 also provide a fuel injector positioned in an exhaust pipe. According to the document US 6539708 , it is expected to have in the exhaust pipe, facing the fuel injector, a plate on which the fuel is injected so that it bounces on and disperses in the flue gas stream. However, some of the fuel remains on the plate and flows to the oxidation catalyst without evaporating. Furthermore, the plate is inclined relative to the direction of the flue gas flow, so that it obstructs a portion of the passage section of the exhaust pipe. This obstacle causes pressure losses in the exhaust pipe, which causes a decrease in engine performance.

OBJECT OF THE INVENTION

The invention proposes a new exhaust line in which the fuel injected evaporates and rapidly homogenizes in the flue gas stream, without creating a significant increase in pressure losses in the exhaust pipe.

More particularly, it is proposed according to the invention an exhaust line as defined in the introduction, wherein there is provided a plurality of planar fins disposed in the exhaust pipe for one of the faces of each fin to receive a portion of a fuel jet from said fuel injector.

The impact of the fuel jet on the fins allows the fuel jet to be broken up and dispersed over a number of different surfaces, which increases the fuel exchange surface with the hot flue gases. The evaporation rate of the fuel in the exhaust pipe is therefore higher. In addition, the impact of the jet of fuel on the fins makes it possible to bounce the fuel droplets and thus to disperse them in the flue gases. The dispersion of the fuel injected into the exhaust pipe thus promotes the evaporation and homogenization of the fuel in the flue gases.

In addition, the fins being entirely disposed in the exhaust pipe, they have a temperature greater than that of the walls of the exhaust pipe; the evaporation of the fuel is thus faster than when the fuel is thrown against the walls of this pipe.

According to a first advantageous characteristic of the invention, the fins are parallel to each other.

According to another advantageous characteristic of the invention, the fins each extend in a general plane which is substantially parallel to the average line of the exhaust pipe.

The general plane of the fin means the mean plane in which the fin extends, that is to say the virtual plane whose mean distance to the fin is the lowest. In particular, when the fin is flat, the general plane corresponds to the plane of the fin.

Thus, only the slices of the fins face the flue gas flow, which limits the pressure losses of this flow.

• les ailettes sont régulièrement espacées les unes des autres ;
• le jet de carburant est injecté suivant un axe central d'injection incliné par rapport à la ligne moyenne de la conduite d'échappement ;
• les ailettes possèdent des bords d'attaque qui s'étendent tous dans un même plan d'attaque incliné par rapport à la ligne moyenne de la conduite d'échappement ;
• le plan d'attaque et l'axe central d'injection sont séparés angulairement d'un angle compris entre 10 et 40 degrés ;
• il est prévu des moyens de maintien des ailettes constitués par des plaques-support qui s'étendent transversalement auxdites ailettes, dans des plans sensiblement parallèles à la ligne moyenne de la conduite d'échappement ;
• lesdites ailettes et les plaques-support comportent des rainures adaptées à s'insérer les unes dans les autres pour l'assemblage par emboîtement desdites ailettes et desdites plaques-support ;
• il est prévu une bague de maintien qui assure l'assemblage des ailettes avec les plaques-support et qui est sertie dans la conduite d'échappement ; et
• il est prévu, en aval desdites ailettes et de l'injecteur de carburant par référence au sens d'écoulement des gaz brûlés, un catalyseur d'oxydation suivi d'un filtre à particules.

Other advantageous and non-limiting features of the exhaust line according to the invention are the following:

• the fins are evenly spaced from each other;
• the fuel jet is injected along a central injection axis inclined relative to the average line of the exhaust pipe;
• the fins have leading edges which all extend in the same inclined plane of attack relative to the average line of the exhaust pipe;
• the plane of attack and the central injection axis are angularly separated by an angle of between 10 and 40 degrees;
• there are provided means for holding the fins constituted by support plates which extend transversely to said fins, in planes substantially parallel to the average line of the exhaust pipe;
• said fins and the support plates have grooves adapted to be inserted into each other for the interlocking assembly of said fins and said support plates;
• there is provided a retaining ring which assures the assembly of the fins with the support plates and which is crimped in the exhaust pipe; and
• there is provided, downstream of said fins and the fuel injector by reference to the flow direction of the flue gases, an oxidation catalyst followed by a particulate filter.

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.

• la figure 1 est une vue schématique d'ensemble d'un moteur à combustion interne comportant une ligne d'échappement selon l'invention ;
• la figure 2 est une vue partielle en coupe d'une conduite d'échappement de la ligne d'échappement de la figure 1 dans laquelle est serti un dispositif d'homogénéisation ; et
• la figure 3 est une vue éclatée du dispositif d'homogénéisation de la figure 2.

In the accompanying drawings:

• the figure 1 is a schematic overview of an internal combustion engine having an exhaust line according to the invention;
• the figure 2 is a partial sectional view of an exhaust pipe of the exhaust line of the figure 1 in which is crimped a homogenizer; and
• the figure 3 is an exploded view of the homogenization device of the figure 2 .

In the description, the terms "downstream" and "upstream" are used in the direction of the flow of air, from the point of sampling the fresh air into the atmosphere until it leaves a catalytic converter. .

On the figure 1 , there is shown a diesel-type 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 of fresh air. This intake line 20 draws fresh air directly into the atmosphere and the filter by means of an air filter 21. It extends to an air distributor 22 which opens onto four intake channels 23 each connected to one of the cylinders 12 of the combustion chamber 11.

The intake line 20 further comprises a compressor 31 of a turbocharger 30 which compresses the fresh air filtered by the air filter 21 to inject it under pressure into the air distributor 22.

Downstream of the combustion chamber 11, the internal combustion engine 10 comprises an exhaust line 40 of burnt gases extending from an exhaust manifold 41, connected by four exhaust channels 42 to each of the cylinders 12 of the engine. the combustion chamber 11, up to the catalytic converter 45. This catalytic converter 45 here comprises internally an oxidation catalyst 46 followed, in the flow direction of the flue gas, of a particulate filter 47.

The oxidation catalyst 46 is in particular adapted to oxidize the HC hydrocarbons and CO carbon monoxide contained in the flue gases circulating in the exhaust line 40.

The particulate filter 47 is in turn adapted to filter and store the polluting particles (also called soot) produced by the combustion of fuel and fresh air in the combustion chamber 11, so as to prevent them from being released into the atmosphere. This filter must be regularly regenerated so as not to be clogged by too much of the polluting particles.

The particulate filter 47 may optionally be lined internally with a catalytic material, such as platinum, adapted to oxidize the HC hydrocarbons and carbon monoxide CO contained in the flue gas.

Anyway, the exhaust line 40 comprises an auxiliary oxidation catalyst 44 disposed upstream of the catalytic converter 45 and connected thereto by an exhaust pipe 43 of circular section. This auxiliary oxidation catalyst 44 is intended to fractionate the heavy HC hydrocarbons, so that they are treated more easily and more rapidly by the oxidation catalyst 46 of the catalytic converter 45.

The exhaust line 40 further comprises, upstream of the auxiliary oxidation catalyst 44, a turbine 32 which is driven by the flue gas stream to actuate the compressor 31.

As shown in figure 1 the internal combustion engine 10 also comprises a flue gas recirculation line 60 which originates in the exhaust line 40, between the exhaust manifold 41 and the turbine 32, and which opens into the intake line 20 between the compressor 31 and the air distributor 22. The recirculation line 60 comprises, at its junction with the inlet line 20, a valve 61 for regulating the flow rate of the burnt gases reinjected into the combustion chamber 11 of the internal combustion engine 10. This recirculation line 60 reduces the volume of pollutant emissions released by the internal combustion engine 10.

The internal combustion engine 10 also comprises fuel injection means 50 for introducing fuel directly into the exhaust pipe 43.

These injection means 50 comprise in a known manner a fuel tank 51 connected to a pump 52 which draws fuel into the tank to bring it under pressure into a fuel injector 53. The latter opens into the interior of the tank. exhaust pipe 43. The injector 53 makes it possible to send the desired quantity of fuel into this pipe, at the desired moment. For this purpose, the opening and closing of the fuel injector 53 is controlled by electronic control means 75 of the internal combustion engine 10.

As shown in figure 2 , this fuel injector 53 is adapted to send a jet of fuel 54 in an injection cone C of injection central axis W. The fuel injector 53 is more particularly positioned in the exhaust pipe 43 of such so that the central injection axis W intersects the average line V of the exhaust pipe 43 and is inclined with respect to this average line V (the central injection axis W is therefore neither confused nor perpendicular at the mean line V). As illustrated by figure 2 , the jet of fuel 54 is here directed obliquely towards the outlet of the exhaust pipe 43, in the direction of flow of the burnt gases, so that the central injection axis W is inclined by an angle of about 45 degrees from the average line V of the exhaust pipe 43.

As shown in figure 1 , the electronic control means 75 of the internal combustion engine 10 are connected to two pressure sensors 71, 74 adapted to measure the pressure difference between the inlet and the outlet of the catalytic converter 45. This pressure difference is a function of the filling the particle filter 47 with the polluting particles. The pressure sensors 71, 74 thus make it possible to determine the degree of fouling of this filter.

The control means 75 are also connected to two temperature sensors 72, 73, one disposed in the exhaust pipe 43, just upstream of the injector 53, and the other disposed in the catalytic converter 45, between the oxidation catalyst 46 and the particulate filter 47. These temperature sensors provide continuously to the control means 75 two signals representative of the temperature of the flue gases. One is representative of the temperature of these gases before they enter the catalytic converter 45, and the other is representative of the temperature of these gases when they were treated by the oxidation catalyst. The control means can thus control the amount of fuel injected by the fuel injector 53 as a function of these measured temperatures, so that the flue gases have a desired temperature.

Advantageously, as shown by figures 1 and 2 , the exhaust pipe 43 internally comprises a homogenization device 100 for promoting the evaporation of the fuel in the flue gases and their homogenization.

As illustrated particularly figure 2 this homogenizing device 100 comprises four rectangular fins 101, 102, 103, 104 which are positioned parallel to one another in the exhaust pipe 43, downstream of the fuel injector 53. These fins 101, 102, 103, 104 are disposed in general planes parallel to the average line V of the exhaust pipe 43, so that one of their two faces is exposed to the jet of fuel 54 contained in the injection cone C of the fuel injector 53. More specifically, the general planes of these fins are orthogonal to the plane comprising the central injection axis W and the average line V of the exhaust pipe 43. The fins 101, 102, 103 , 104 are regularly spaced from each other.

As shown by figures 2 and 3 each fin 101, 102, 103, 104 has a leading edge 101A, 102A, 103A, 104A, which faces the flow of gas burned, and a trailing edge 101 B, 102B, 103B, 104B opposite. The other two edges of each fin extend parallel to the inner wall of the exhaust pipe 43, at a very weak distance from the latter.

The exhaust pipe 43 having a circular section, the four fins have different widths from each other. These four fins are here made of sheet metal one millimeter thick.

The trailing edges 101 B, 102B, 103B, 104B of the fins all extend in the same plane of leakage T which is here inclined with respect to the planes orthogonal to the average line V of the exhaust pipe 43.

The leading edges 101A, 102A, 103A, 104A of the fins extend in the same plane of attack P inclined with respect to the planes orthogonal to the average line V of the exhaust pipe 43.

The fins 101, 102, 103, 104 here have different lengths from each other. These lengths are between 30 and 60 millimeters.

The plane of attack P is here inclined with respect to the central injection axis W of an angle A preferably between 10 and 40 degrees. It is positioned relative to the fuel injector 53 so that a portion of each jet of fuel 54 from the fuel injector 53 is projected onto each of the four fins 101, 102, 103, 104 of the fuel injection device 53. homogenization 100. All fuel injected is distributed on the various fins 101, 102, 103, 104 of the device.

One could of course provide a different arrangement of the fins relative to the fuel injector, provided that a portion of each jet of fuel impacts each of said fins of the homogenizer 100.

The exhaust line 40 further comprises means for holding the fins 101, 102, 103, 104 constituted here by two support plates 105, 106. These two support plates 105, 106 are positioned orthogonally to the fins 101, 102, 103, 104, parallel to the average line V of the exhaust pipe 43. They are more precisely nested in the fins 101, 102, 103, 104.

For this purpose, each fin 101, 102, 103, 104 is pierced over half of its length with two parallel grooves 107 extending from its leading edge 102A, 104A for two of the fins 102, 104 and from its edge. 101A, 103A for the other two fins 101, 103. The two grooves of each fin 101, 102, 103, 104 are spaced a certain distance which is identical for all the fins 101, 102, 103, 104.

In correspondence, the support plates 105, 106 are drilled halfway along their length with four parallel grooves. Two of these grooves extend from the trailing edge 105B, 106B of each support plate, while the other two extend from the leading edge 105A, 106A of these support plates. These grooves are offset relative to each other and are intended to be inserted into the grooves of the fins 101, 102, 103, 104 so that these fins can fit into the support plates 105, 106.

The two support plates are identical. They each comprise a leading edge 105A, 106A, disposed in the plane of attack P, and a trailing edge 105B, 106B arranged in the leakage plane T. The other two edges of each support plate extend in parallel. at the inner wall of the exhaust pipe 43. They each have a shoulder 109, so that the trailing edges 105B, 106B of the support plates have lengths greater than those of their leading edges 105A, 106A.

In order to hold the fins and the support plates in assembled position, the exhaust line 40 comprises a retaining ring 110. This retaining ring 110 is fitted around the fins and the support plates, by their leading edge, up to abut against the shoulders 109 of the support plates 105, 106. The retaining ring 110 is crimped on all of these fins.

The retaining ring 110 is also crimped into the exhaust pipe 43. For this, the latter comprises two parts connected to each other by clamps 48, 49. The retaining ring 110 can thus be easily inserted into the exhaust pipe 43 to be crimped.

With reference to the figure 1 during a normal operating phase of the internal combustion engine 10, the flow of fresh air taken upstream of the air filter 21 follows the intake line 20 and opens into the air distributor 22 to be burned in the combustion chamber 11.

The flue gases from this combustion open into the exhaust line 40. Part of these burnt gases is captured by the recirculation line 60 to be reinjected into the combustion chamber 11. The other part of these flue gases loaded with polluting particles, carbon monoxide CO and HC hydrocarbons, opens into the auxiliary oxidation catalyst 44 and then into the catalytic converter 45. The CO carbon monoxide and the HC hydrocarbons are mainly oxidized from exothermically in the auxiliary oxidation catalyst 44 and in the oxidation catalyst 46 of the catalytic converter 45, while the polluting particles pass through these catalysts and are then captured by the particulate filter 47.

When the pressure sensors 71, 74 measure a difference in pressures between the inlet and the outlet of the catalytic converter 45 greater than a predetermined threshold value (which means that the particulate filter 47 is substantially fouled), the control means 75 of the engine initiate a regeneration step of the particulate filter 47.

For this purpose, the fuel injector 53 projects, at intervals or continuously, a jet of fuel 54 which impacts the fins 101, 102, 103, 104 of the homogenizer device 100.

Part of the impacted fuel bounces against the fins and evaporates directly into the flue gases, while the other part flows along the hot fins 101, 102, 103, 104 and evaporates in turn entering the catalytic converter 45. The fuel is thus quickly and correctly homogenized to the flue gas when it enters the pot.

The mixture of flue gases and fuel is heavily loaded with carbon monoxide CO and HC hydrocarbons. These two components are then very exothermically oxidized within the oxidation catalyst 46, which greatly increases the temperature of the mixture.

The control means 75 simultaneously regulate, in real time, the fuel flow injected into the exhaust pipe 43 as a function of the temperatures of the flue gases measured by the temperature sensors 72, 73 and as a function of the engine speed. The fuel flow rate is regulated so that the temperature of the flue gases entering the particulate filter 47 is constantly between 570 and 650 ° C.

When the pressure sensors 71, 74 measure a difference in pressures between the inlet and the outlet of the catalytic converter 45 lower than another predetermined threshold value (which means that the particulate filter 47 is sufficiently regenerated), the control means 75 of the motor command stop fuel injections into the exhaust pipe 43. The internal combustion engine 10 then enters again into a normal operating phase.

Claims (11)

1. Exhaust line (40) of an internal combustion engine (10) comprising an exhaust pipe (43) for burnt gases and at least one fuel injector (53) terminating in the said exhaust pipe (43), characterized in that it comprises a plurality of planar fins (101, 102, 103, 104) arranged in the exhaust pipe (43) so that one of the faces of each fin (101, 102, 103, 104) receives part of a fuel jet (54) issuing from the said fuel injector (53).
2. Exhaust line (40) according to the preceding claim, characterized in that the fins (101, 102, 103, 104) are parallel to one another.
3. Exhaust line (40) according to the preceding claim, characterized in that the fins (101, 102, 103, 104) each extend in a general plane which is substantially parallel to the median line (V) of the exhaust pipe (43).
4. Exhaust line (40) according to one of the preceding claims, characterized in that the fins (101, 102, 103, 104) are uniformly spaced from one another.
5. Exhaust line (40) according to one of the preceding claims, characterized in that the fuel jet (54) is injected along a central injection axis (W) inclined to the median line (V) of the exhaust pipe (43).
6. Exhaust line (40) according to one of the preceding claims, characterized in that the fins (101, 102, 103, 104) have leading edges (101A, 102A, 103A, 104A) which all extend in the same leading plane (P) inclined to the median line (V) of the exhaust pipe (43).
7. Exhaust line (40) according to the two preceding claims, characterized in that the leading plane (P) and the central injection axis (W) are angularly spaced by an angle (A) of between 10 and 40 degrees.
8. Exhaust line (40) according to one of the preceding claims, characterized in that it comprises means for holding the fins (101, 102, 103, 104) consisting of support plates (105, 106) which extend transversally to the said fins (101, 102, 103, 104) in planes that are substantially parallel to the median line (V) of the exhaust pipe (43).
9. Exhaust line (40) according to the preceding claim, characterized in that the said fins (101, 102, 103, 104) and the support plates (105, 106) comprise grooves (107, 108) adapted for being inserted into one another for the socketed assembly of the said fins (101, 102, 103, 104) and the said support plates (105, 106).
10. Exhaust line (40) according to one of the two preceding claims, characterized in that it comprises a holding ring (110) for joining the fins (101, 102, 103, 104) to the support plates (105, 106) and which is swaged in the exhaust pipe (43).
11. Exhaust line (40) according to one of the preceding claims, characterized in that, downstream of the said fins (101, 102, 103, 104) and of the fuel injector (53), with regard to the burnt gas flow direction, it comprises an oxidation catalyst (46) followed by a particulate filter (47).

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