Post-combustion devices for internal combustion engines

Claim 1

Post-combustion device for burning combustible gases contained in the exhaust gases of an internal combustion engine, comprising a post-combustion chamber devoid of a spark producing means and bounded by a casing, means for introducing additional air into the post-combustion chamber, a heat-exhanger adapted to pre-heat the additional air by exhaust gases from the post-combustion chamber, the heatexchanger surrounding the said post-combustion chamber and being such that the circulation of additional air is effected in a peripheral zone in countercurrent to the exhaust gases which flow in an intermediate zone comprised between the said peripheral zone and the casing of the combustion chamber, the means for introducing the additional air comprising a blower adapted to be driven by the engine and to deliver a flow of additional air in excess, and the assembly of the postcombustion chamber and the heat-exchanger being constituted by three coaxial cylinders namely an inner cylinder forming the casing of the post-combustion chamber and adapted to be connected to the exhaust pipe of the engine in such a way that the exhaust gases of the latter are introduced at the center and in the axis of said inner cylinder, an intermediate cylinder forming with the inner cylinder an annular space which constitutes said intermediate zone and communicates, at an end situated at the side of the engine exhaust pipe, with the postcombustion chamber by openings provided in the inner cylinder and, at its other end, with a pipe for the escape of the burnt gases from the post-combustion chamber, an outer cylinder defining with the intermediate cylinder the abovesaid peripheral zone, which communicates, on one hand, with an inlet pipe for additional air and, on the other hand, with the exhaust pipe of the engine through holes provided in the latter and situated axially between two end-enclosing covers substantially flat and at right angles to the common axis of the cylinders, said covers being traversed by the exhaust pipe of the engine and being adapted to shut, at one end, on one hand the intermediate cylinder and the inner cylinder and, on the other hand, the outer cylinder, the axial distance between the covers being just sufficient for the holes to open between the said covers, said peripheral zone including a partition rolled in a helix, adapted to increase the path traversed by the additional air in said peripheral zone, the assembly being arranged in such a way that said intermediate zone separates the peripheral zone from the combustion chamber over the whole of the axial length of the latter, and sensing means sensitive to at least one of (a) the speed and (b) the load of the engine comprising by-pass means located between the heat exchanger and the atmosphere to prevent the air delivered by the blower, which has cooled the exhaust gases from the post combustion chamber from being introduced into said post-combustion chamber when at least one of (a) and (b) has a value higher than a given limit to which corresponds a chosen power limit, in such a way that the post-combustion ceases when the engine delivers a power higher than said chosen power limit.