FR2941490A1 - Combustion gas exhaust line for diesel engine of vehicle, has isolation sleeve for surrounding envelope, and connected to connection pipe and to evacuation pipe for permitting passage of combustion gas around envelope - Google Patents

Abstract

The line (30) has an exhaust manifold (31) for collecting combustion gas emitted by an engine, and a main particle filter (36) housed in a protection envelope (36A). The envelope has an end connected to the manifold by a connection pipe (34), and another end communicating with a combustion gas evacuation pipe (35). An isolation sleeve (50) surrounds the envelope, while letting a space around the envelope. The sleeve is connected to the connection pipe and to the evacuation pipe for permitting passage of the combustion gas around the envelope. An independent claim is also included for an internal combustion engine comprising a combustion gas exhaust line.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention relates generally to the treatment of burnt gases emitted by internal combustion engines. It relates more particularly to an exhaust line of an internal combustion engine, comprising, according to the flow direction of the flue gases, an exhaust manifold for collecting the burnt gases emitted by the engine, and a particulate filter housed in a combustion chamber. protection casing, one end of which is connected to the exhaust manifold by a connecting duct, and the other end of which communicates with a flue gas discharge duct into the atmosphere. It also relates to an internal combustion engine comprising an engine block equipped with cylinders, a fresh air intake line in the cylinders of the engine block, and such a line of exhaust gases burned out of the cylinders of the block. engine.

TECHNOLOGICAL BACKGROUND The flue gases of internal combustion engines contain various pollutants that must be treated or filtered before discharging these gases into the atmosphere. For this purpose, the exhaust line of an engine usually comprises a catalytic converter followed, according to the flow direction of the flue gas, a particulate filter. The catalytic converter is coated with a catalytic material to oxidize, in the presence of oxygen, the unburnt hydrocarbons contained in the flue gases.

The particulate filter makes it possible to filter and store the pollutant particles suspended in the flue gases. The accumulation of pollutant particles in the filter, however, hampers the evacuation of the flue gases, which, over time, generates an overpressure of the flue gases upstream of the filter, which is detrimental to the proper functioning of the internal combustion engine.

It is then known to regenerate the particulate filter by injecting fuel (or any other reducing agent) into the exhaust line, so as to cause a very exothermic oxidation reaction of the hydrocarbons in the catalytic converter. The flue gases therefore exit the catalytic converter at a high temperature (of the order of 630 ° C) and enter the particulate filter by burning the polluting particles that fill the latter. However, in the exhaust lines of the aforementioned type, the temperature of the protective envelope of the particulate filter is not homogeneous. Indeed, when the vehicle that is equipped with this filter advances, the cool air that passes under the vehicle cools only parts of the filter protection envelope. In normal operation, the temperature difference between the hot and cold parts of the enclosure is not sufficient to cause damage to the filter. On the other hand, during the phases of active regeneration of the filter, the differences of temperatures within the filter can be very important. The first risk is that a part of the particulate filter does not reach a temperature sufficient to burn the pollutant particles stored in this part of the filter, to the detriment of the efficiency of the regeneration. The second risk is that, due to these differences in temperature, the filter does not deform homogeneously, the risk of cracking and seeing its performance prematurely reduced.

OBJECT OF THE INVENTION In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a new exhaust line in which the temperature of the particulate filter is controlled to be homogeneous. More particularly, the invention proposes an exhaust line as defined in the introduction, comprising an insulation sleeve which surrounds said protective envelope, leaving a space around the latter, and which connects, on the one hand, to the connecting duct, and, on the other hand, to the evacuation duct, to allow the passage of burnt gases around the protective envelope.

Thus, thanks to the invention, the insulation sleeve defines a volume around the protective envelope of the particulate filter, in which it is possible to circulate hot burnt gases to cause a homogeneous temperature rise of the whole of the protective envelope, and therefore of the whole of the main particle filter.

Other advantageous and non-limiting features of the exhaust line according to the invention are the following: - there is provided an auxiliary particle filter, separate from said main particle filter, for filtering the flue gases passing around the protective envelope; the auxiliary particle filter has an inlet section whose area is greater than that of the inlet section of the main particle filter; said protective envelope and said insulation sleeve are arranged co-axially; the junction conduit comprises a bypass valve for regulating the flow rate of burnt gases that circulates between said insulating sleeve and said protective envelope; the bypass valve has two stable states, including a closed state in which all the flue gases pass through the main particle filter, and an open state in which the majority of the flue gases circulate between said insulation sleeve and said envelope; protection ; - The bypass valve comprises a sleeve which is mounted in translation on the connecting duct to seal or leave free an opening provided in correspondence in the wall of the connecting duct; - The connecting pipe is equipped with a catalytic converter which is located between the exhaust manifold and the inlet of the insulation sleeve; said protective envelope houses a catalytic converter situated directly upstream of the main particulate filter. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description, with reference to the appended drawings, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: - Figure 1 is a schematic view of an exhaust line according to the invention, equipped with a bypass valve shown in a closed state; - Figure 2 is a schematic view of the exhaust line of Figure 1, wherein the bypass valve is shown in the open state; - Figure 3 is a schematic view of a first embodiment of the exhaust line of Figure 1; and FIG. 4 is a schematic view of a second variant embodiment of the exhaust line of FIG.

As a preliminary, it will be noted that the identical or similar elements of the different embodiments of the invention shown in the different figures will, as far as possible, be referenced by the same reference signs and will not be described each time. In the description, the terms upstream and downstream will be used in the direction of gas flow, from the point of sampling fresh gases in the atmosphere to the exit of the burned gases out of the engine. The invention applies to any type of internal combustion engine rejecting polluting particles to be filtered, and more specifically to any type of internal combustion engines with compression ignition (Diesel). As shown in FIGS. 1 and 2, such an internal combustion engine 1 typically comprises an engine block 10 provided with four cylinders 11.

Upstream of the cylinders 11, the internal combustion engine comprises an intake line 20 which takes fresh air into the atmosphere and which brings and distributes this fresh air in each of the cylinders 11 of the engine block 10. Downstream of the 11, the internal combustion engine 1 comprises a burnt gas exhaust line 30 which collects the burnt gases leaving each of the cylinders 11 and which discharges them into the atmosphere after being treated and filtered. This exhaust line 30 is for this purpose equipped with an exhaust manifold 31, a turbocharger turbine 32, a catalytic converter 33 and a main particulate filter 36. The internal combustion engine comprises Moreover, an EGR line for recirculating burnt gases (not visible in the figures) which originates in the exhaust line 30 and which opens into the intake line 20. It also has fuel injectors which open into the cylinders. 11 of the engine block 10 or, alternatively, upstream of the cylinders 11, in the intake line 20.

Finally, it comprises a control unit adapted to control the various engine components, in particular here its fuel injectors. As represented in FIGS. 1 and 2, the catalytic converter 33 which equips the exhaust line 30 is a three-way catalyst suitable for treating the unburned hydrocarbons HC, the nitrogen oxides NOX and the carbon monoxide CO contained in the burnt gases that pass through it. The main particle filter 36 comprises meanwhile a conventional architecture, with a beam of parallel porous tubes, alternately closed at the inlet and at the outlet of the filter. This architecture makes it possible to force the passage of the flue gases through the porous walls of the tubes in order to retain the polluting particles contained in the flue gases. This bundle of tubes is housed in a cylindrical protective envelope 36A, made of metallic material. This protective envelope 36A has two ends, including a burnt gas inlet end and an outlet end which communicates with a flue gas exhaust duct 35 into the atmosphere. To guide the flue gases from the catalytic converter 33 to the inlet end of the protective casing 36A, the exhaust line 30 comprises a connecting duct 34 and a diverging 38 (also called watering cone). The junction duct 34, here cylindrical, originates at the output of the catalytic converter 33 and extends to the inlet of the divergent 38. The outlet of the divergent 38 is connected to the inlet end of the envelope 36. The divergent 38 thus makes it possible to uniformly distribute the burnt gases over the entire inlet section S6 of this main particle filter 36. According to a particularly advantageous characteristic of the invention, the exhaust line 30 comprises an insulation sleeve 50 which extends around said protective envelope 36A, at a distance from the latter, and which has an inlet 51 of burnt gases stitched on the connecting duct 34 and an outlet 52 The insulation sleeve 50 and the protective envelope 36A therefore define between them an isolation volume 55 for the passage of the burnt gases. The insulation sleeve 50 has a function of mechanical and thermal protection of the protective envelope 36A and the divergent 38. The walls of the latter may therefore have reduced thicknesses, having the ability to rise in temperature very quickly, without risk premature degradation.

The insulating sheath 50 here has a tubular shape, of inside diameter strictly greater than the outside diameter of the protective casing 36A of the main particle filter 36. It is advantageously arranged coaxially with respect to this protective casing 36A, so that that the volume of insulation 55 is regularly distributed around this envelope.

The isolation sleeve 50 is also equipped, at one of its ends, with an inlet cone 53 whose free end connects to the connecting duct 34, between the catalytic converter 33 and the divergent 38, and at the other of its ends, an outlet cone 54 whose free end connects to the inlet of the exhaust duct 35.

In this way, the inlet cone 53 of the insulating sheath 50 envelops part of the connecting duct 34. The wall of this part of the connecting duct 34 is provided with an opening of the flue gas inlet opening 34A. Isolation volume 55. This opening 34A is in this case formed by cutting a short length section of the connecting duct 34.

Advantageously, the connecting duct 34 comprises a bypass valve 39 which makes it possible to regulate the flow rate of burnt gases passing through this opening 34A, in order to distribute the flue gases to the main particulate filter 36 and / or to the volume of the flue gas. 55. This bypass valve 39 comprises here a sleeve which is mounted in translation on the connecting duct 34 to close or leave free the opening 34A provided in the wall of the connecting duct 34, and an actuator for controlling in position the sleeve 39. Here, the actuator is controlled by the control unit between two stable states, including a closed state in which the opening 34A is closed by the sleeve 39 so that all the burnt gases from the cylinders 11 passes through the main particle filter 36, and an open state in which the opening 34A is left open so that the vast majority of the flue gas circulates in the isolation volume 55, e the insulation sleeve 50 and the protective envelope 36A, bypassing the main particle filter 36. Preferably, the insulation sleeve 50 or the exhaust duct 35 houses an auxiliary particle filter 37 for filtering the flue gases circulating in the isolation volume 55 and which, therefore, are not filtered by the main particle filter 36. Here, this auxiliary particle filter 37 is housed in the insulation sleeve 50, directly downstream of the main particulate filter 36, so that the flue gases do not have time to cool as they pass from one filter to another. This auxiliary particle filter 37 is in the form of a bundle of tubes housed in a protective casing of diameter equal to the diameter of the insulating sheath 50. This bundle of tubes here has a length less than that of the bundle of tubes. of the main particle filter 36, in favor of the axial compactness of the exhaust line 30. It has instead an inlet section S7 whose area is greater than that of the inlet section S6 of the particulate filter 36, so as not to generate too much back-pressure of the burnt gases in the isolation volume 55.

The control method of the internal combustion engine 1 by the control unit is as follows. In normal operating mode, the bypass valve 39 is controlled to remain in a closed state (FIG. 1). The flue gases leaving the cylinders 11 of the engine block are thus oxidized in the catalytic converter 33 and then filtered by the main particulate filter 36. At their output from the main filter 36, they pass through the auxiliary particulate filter 37 and in this mode of operation, the control unit acquires the loading rate of the two particulate filters 36, 37. Normally, if the main particulate filter 36 is filled correctly its office, the loading rate of the main particle filter 36 evolves while that of the auxiliary particle filter 37 remains constant. When the loading rate of the main particulate filter 36 exceeds a critical threshold and the filter regeneration conditions (inherent to the operation of the vehicle) are met, the control unit controls the opening of the bypass valve 39 (FIG. 2). The flue gases then exit the connecting duct 34 through its opening 34A, and circulate in the isolation volume 55, thereby heating the protective envelope 36A of the main particulate filter 36. They are then filtered by the particulate filter Auxiliary 37, which then only begin to charge in polluting particles. Finally, the flue gases are discharged into the atmosphere. The pilot unit then drives the fuel injectors, so that they inject a surplus of fuel into the cylinders. The richness of the mixture of fresh air and fuel in the cylinders 11 then increases so that a surplus of fuel comes out of the cylinders 11 without having been burned. This excess fuel then enters the catalytic converter 33, which causes a very exothermic oxidation reaction of the fuel. The flue gas therefore leaves the catalytic converter at a very high temperature, of the order of 650 ° C. Then, the entire exhaust line rising in temperature, the temperature of the flue gas circulating in the isolation volume 55 increases until a threshold temperature, for example equal to 630 ° C. Then, the control unit controls the closing of the bypass valve 39. The flue gas then passes again through the main particle filter 36 and then through the auxiliary particle filter 37, by burning the pollutant particles that fill these parts. two filters. Thus, thanks to the volume of insulation 55 in which stagnant gases burned at high temperature, the protective envelope 36A has a homogeneous temperature at any point, so that the deformations of the filter under the effect of the increase in temperature occur in a homogeneous and controlled manner, without risk of cracking. The present invention is not limited to the embodiment described and shown, but the art can apply any variant within his mind. In particular, according to a first variant embodiment shown in FIG. 3, it will be possible for the catalytic converter 40 to be situated, not directly upstream of the protective envelope 36A of the main particle filter 36, but directly therein. . In this variant, the heat losses between the catalytic converter 40 and the main particulate filter 36 are reduced. In this way, the temperature from which the filter regenerates is more quickly achieved, to the benefit of the engine fuel consumption and the reduction of its carbon dioxide emissions. It will be understood, however, that when the bypass valve is in an open state, the flue gases circulating in the isolation volume 55 are not heated by the catalytic converter 40. When the excess fuel is injected, they can however, reach a temperature of the order of 500 ° C, which is sufficient to heat the shroud 36A so as to prevent the main particle filter 36 does not crack. According to a second variant embodiment shown in FIG. 4, the exhaust line 30 may comprise two catalytic converters, including a first catalytic converter 33 located between the exhaust manifold 31 and the inlet 51 of the quill. isolation 50, and a second catalytic converter 40 located in the protective envelope 36A, directly upstream of the main particle filter 36. This variant allows to combine the advantages of the exhaust lines shown in Figures 1 and 3. More precisely , thanks to the first catalytic converter 33, the flue gases passing through the insulating volume 55 are first heated to reach a temperature of about 650 ° C. Moreover, thanks to the second catalytic converter 40, the heat losses between the catalytic converter 40 and the main particulate filter 36 are reduced. As shown in FIGS. 3 and 4, it is also possible to provide that the motor comprises a gear injector 41 located in the exhaust line 30, upstream of the catalytic converter 40. Thanks to this injector 41, it will no longer be necessary to control the fuel injectors so that they inject into the cylinders 11 a surplus of fuel. The rate of fuel diluting in the oil of the engine block will be reduced.

Claims (10)

REVENDICATIONS1. Exhaust line (30) of an internal combustion engine (1), comprising, according to the direction of flow of the flue gases: - an exhaust manifold (31) for collecting the burnt gases emitted by the engine, and - a main particle filter (36) housed in a protective casing (36A), one end of which is connected to the exhaust manifold (31) by a connecting duct (34), and the other of which communicates with a duct; discharge (35) of the flue gas into the atmosphere, characterized in that it comprises an insulation sleeve (50) which surrounds said protective envelope (36A), leaving a space around the latter, and which is connected on the one hand, to the connecting duct (34), and on the other hand, to the exhaust duct (35), to allow the passage of burnt gases around the protective envelope (36A). 2. Exhaust line (30) according to the preceding claim, wherein there is provided an auxiliary particle filter (37), separate from said main particle filter (36), for filtering the flue gases that pass around the envelope protection device (36A). 3. Exhaust line (30) according to the preceding claim, wherein the auxiliary particle filter (37) has an inlet section (S7) whose area is greater than that of the inlet section (S6) the main particulate filter (36). 4. Exhaust line (30) according to one of the preceding claims, wherein said protective casing (36A) and said insulating sleeve (50) are arranged co-axially. 5. Exhaust line (30) according to one of the preceding claims, wherein the connecting duct (34) comprises a bypass valve (39) for regulating the flow of burnt gas flowing between said insulating sleeve ( 50) and said protective envelope (36A). 6. Exhaust line (30) according to the preceding claim, wherein the bypass valve (39) has two stable states, including a closed state in which all the flue gas passes through the main particulate filter (36), and an open state in which the majority of the flue gas flows between said insulating sheath (50) and said shroud (36A). 7. Exhaust line (30) according to one of the two preceding claims, wherein the bypass valve comprises a sleeve (39) which is mounted in translation on the connecting duct (34) to seal or leave open an opening ( 34A) provided in correspondence in the wall of the connecting duct (34). 8. Exhaust line (30) according to one of the preceding claims, wherein the connecting duct (34) is equipped with a catalytic converter (33) which is located between the exhaust manifold (31) and the inlet (51) of the insulation sleeve (50). 9. Exhaust line (30) according to one of the preceding claims, wherein said protective casing (36A) houses a catalytic converter (40) located directly upstream of the main particulate filter (36). 10. Internal combustion engine (1) comprising an engine block (10) equipped with cylinders (11), a fresh air intake line (20) in the cylinders (11) of the engine block (10), characterized in that it comprises an exhaust line (30) of the burnt gases according to one of the preceding claims.