Catalytic converter

Details Catalytic converter Catalytic converter

1994-04-11

1995-11-14

Hart, Douglas

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

60284, 60303, 422174, F01N 328

Patent

active

054655749

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a rapid light-off catalytic converter.


BACKGROUND OF THE INVENTION

It is known to incorporate an afterburner in the exhaust system of an internal combustion engine in order to heat a catalytic converter so as to reduce the time it takes to reach its light-off temperature. The flame in the afterburner heats up the front face of the matrix in the converter but the heat is localised to this area for some time. As this portion of the matrix is subjected to the most severe conditions, its catalyst is the most prone to contamination and therefore when the catalytic converter ages, raising the temperature of its front face does not have the desired effect of reducing the time taken for it to become effective.


SUMMARY OF THE INVENTION

According to the present invention, there is provided a catalytic converter for an internal combustion engine exhaust system, having an outer housing, two or more matrices each defining passages for the exhaust gases and carrying particles of a catalyst, the matrices being arranged in series with one another in the direction of flow of engine exhaust gases through the converter, a chamber disposed between the two matrices, and an igniter arranged within the chamber to ignite the gaseous mixture that comprises only the gases that have passed through the first of the two matrices, the mixture being caused to burn as a flame within the chamber so as to form an afterburner for heating the second of the matrices and thereby reducing the time taken for the second of the two matrices to reach its light-off temperature.
It is well known to form a catalytic converter of two separate matrices, or bricks as they are sometimes called. These bricks have the form of a ceramic honeycomb which is coated with a washcoat. Particles of a catalyst, usually platinum, are embedded in the surface of the matrix, the design of the matrix being intended to maximise the surface area over which the catalytic reaction takes place.
By placing the afterburner between two bricks of a catalytic converter, the invention offers several advantages. First, the afterburner heats the second brick instead of the first and therefore takes advantage of the fact that the catalyst in the second brick is less prone to contamination.
In an exhaust afterburner, a flame is ignited which requires control in the same way as any other flame. In the absence of proper control, the flame can burn erratically or it can be extinguished by the exhaust gases passing over it. There is also a risk of the flame blowing back from the afterburner chamber towards the combustion chambers of tile engine.
In the present invention, however, the presence of the first brick upstream of the afterburner chamber helps to stabilise the flame. The brick diffuses and reduces the speed of the stream of exhaust gases from the engine to prevent the flame from being blown out. The first brick also acts as a flame holder to stabilise combustion within the flame and prevent it from flaring.
In a preferred embodiment of the invention, a flame guard is arranged upstream of and in close proximity to the igniter, the flame guard comprising at least one elongate narrow strip spanning the width if the chamber between the bricks.
Preferably, the strip is in the form of a V-shaped channel with the vertex of the V pointing upstream.
Advantageously, the flame guard is formed of a plurality of strips which intersect one another.
The flame guard acts as a shield against the flow of gases through the afterburner creating in its wake regions of low velocity but high turbulence which are easily ignitable and which are not blown out by the main flow. The flame initiated at the igniter easily spreads across the regions behind the flame guard and passes from one strip to another at any intersection between flame guard strips. Thus, when the main gas stream burns as a flame, the base of the flame is not localised to the igniter but it stretches instead over the entire length of the strips of the flame guard.
Because the

REFERENCES:
patent: 3854288 (1974-12-01), Heitland
patent: 3952507 (1976-04-01), Bonarski

Affiliated with

Also associated with

Rating

Catalytic converter does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Catalytic converter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Catalytic converter will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1213832