Emission reduction during cold start via catalyst surface control

Abstract

The present paper is a preliminary investigation of a new approach to the reduction of pollutant emissions during a cold start. During a cold start the volume of the exhaust gases is considerably smaller than those under full load. Therefore, only a small portion of the catalyst active surface is required to process the gases. As the exhaust gases flow from the upstream surface to the downstream surface, they meet with the cold surface of the catalyst, which they should warm up first, before light-off. The larger that surface, the more time will be needed for its warm-up, which will increase the time required for a light-off. The experimental results presented here indicate that there can be a significant reduction of the pollutant emissions during the cold start of an engine, if a system can be devised that could adjust the catalyst active surface during start-up proportionally to the exhaust gas volume. There are strong indications that a quicker warm-up of the catalyst and a faster initiation of catalysis can be achieved by focusing the gas flow towards the centre core of the monolith. In this way the remaining ceramic body of the catalytic converter operates as a heat insulator. This idea may be utilized in the design of catalyst system with variable active surface.