FR2938294A1 - EXHAUST LINE OF COMBUSTION ENGINE - Google Patents

Abstract

The invention relates to a combustion engine exhaust line comprising an exhaust duct (1), in which exhaust gases circulate, a gear reducer injector (2) disposed on a bend of the pipe, substantially on the line of greater radius of curvature of the pipe in the bending plane of this bend, and means for treating the exhaust gas downstream of said injector. According to the invention, said exhaust pipe (1) has an exhaust gas recirculation arrangement, close to said injector (2), substantially aligned with the direction of flow (F) of the gases upstream of said bend.

Description

FIELD OF THE INVENTION The invention relates to a combustion engine exhaust line.

The exhaust lines of an internal combustion engine are generally provided with means of depollution and filtering of the exhaust gas through which the exhaust pipe passes, with the aim in particular of reducing the emissions of particles and oxides of nitrogen, as well as carbon monoxide and unburned hydrocarbons. These means of depollution and filtering usually comprise a catalytic converter and a particulate filter. The particulate filter is used to recover the polluting particles emitted by the combustion of the fresh gas mixture in the combustion chamber of the engine. Such a line comprises upstream of the catalyst pot a regeneration injector disposed in the pipe and which projects a jet of reducer, usually fuel, in the form of sprayed droplets or steam. A regeneration phase consists of injecting fuel into the exhaust line, resulting in an exothermic oxidation phase in the catalytic converter. The exhaust gases then exit the catalytic converter with a high temperature and enter the particulate filter by burning the polluting particles that fill the particulate filter. The invention relates in particular to the case where this injector is installed, following architectural requirements of the line, on a bend of the exhaust pipe, substantially in the curvature plane of the pipe at this point, on the line of greater radius of curvature of the pipe in this plane. The injection nozzle or injector is then mounted on the duct, generally made of cast iron, over the thicknesses of the wall of the bearing pipe, via an injector support, with its head arranged opposite the an orifice arranged in the pipe for the passage of a jet of fuel. Given the requirements of the foundry, the size of this orifice is relatively large and, taking into account more thicknesses of the wall, it is formed in front of the nozzle head a recirculation zone in which are circulated the gases of exhaust following their direction of arrival upstream of the elbow. This recirculation causes too high a temperature at the nozzle head and is therefore harmful for this injection nozzle in terms of service life.

The invention solves this technical problem with a particularly simple manufacturing means. To do this, the invention proposes a combustion engine exhaust line comprising an exhaust pipe, in which exhaust gases circulate, a gear injector disposed on a bend of the pipe, substantially on the line of combustion. greater radius of curvature of the pipe in the plane of curvature of this bend, and exhaust gas treatment means downstream of said injector, line characterized in that said exhaust pipe has a recirculation arrangement of the gas exhaust, near said injector, substantially aligned with the flow direction of the gas upstream of said bend. According to a preferred embodiment, said recirculation arrangement is downstream of said injector. Preferably, said recirculation arrangement is a cavity in the wall of the pipe. Advantageously, said cavity is a groove of semi-circular section. Said groove may have a length of about 15mm and its section a radius of about 12mm.

Advantageously, said recirculation arrangement is arranged in an excess thickness of the wall of the pipe. The invention is described below in more detail with the aid of figures representing only a preferred embodiment of the invention. The figure is a partial sectional view of an exhaust line according to the invention. A combustion engine exhaust line conventionally comprises an exhaust pipe 1, made of cast iron, in which exhaust gases circulate, a gearbox injector 2 disposed on a bend of the pipe, substantially on the line of larger bending radius of the pipe in the curvature plane of this bend, and unrepresented exhaust gas treatment means downstream of the injector. This injector or injection nozzle 2 is mounted on the pipe 1 by means of a nozzle support 3 fixed on an excess thickness 1A 15 of the bearing pipe. The exhaust pipe 1 has an exhaust gas recirculation arrangement, near and downstream of the injector, substantially aligned with the flow direction F of the gas upstream of the bend.

This recirculation arrangement is a cavity in the pipe wall, and more specifically a substantially rectilinear groove 4, of semicircular section, of a length of about 15 mm and whose section has a radius of about 12 mm. This groove is arranged in the excess thickness 1A of the wall of the pipe.

The exhaust gas entering the bend of the exhaust pipe 1 in the indicated direction F, penetrate near the injector 2 directly into the groove 4, where they recirculate and are slowed down, before heading into the zone directly facing the head of the injector at a lower speed or almost zero. During their rotation in the groove 4, there is heat exchange of the gases with the cast iron wall of the groove and therefore decrease in their temperature. The gases arriving in the zone of the injector head are therefore at a very low speed and at a relatively low temperature, which makes it possible to avoid damage to this injector head.

Claims (6)

REVENDICATIONS1. Combustion engine exhaust line having an exhaust duct (1), in which exhaust gas flows, a gear reducer injector (2) disposed on a bend of the duct, substantially on the line of larger radius of curvature of the pipe in the plane of curvature of this bend, and exhaust gas treatment means downstream of said injector, line characterized in that said exhaust pipe (1) has a recirculation arrangement of the gas exhaust, near said injector (2), substantially aligned with the flow direction (F) of the gas upstream of said bend. 2. Line according to the preceding claim, characterized in that said recirculation arrangement is downstream of said injector (2). 3. Line according to one of the preceding claims, characterized in that said recirculation arrangement is a cavity (4) in the wall of the pipe. 4. Line according to the preceding claim, characterized in that said cavity is a groove (4) of semicircular section. 5. Line according to the preceding claim, characterized in that said groove (4) has a length of about 15mm and its section a radius of about 12mm. 6. Line according to one of the preceding claims, characterized in that said recirculation arrangement is arranged in an extra thickness (1A) of the wall of the pipe.