저온활성촉매 변환기의 체적변화가 활성화 성능에 미치는 영향에 관한 수치적 연구

Abstract

HC and CO emissions during the cold start contribute the majority of the total emissions in the legislated driving cycles. Therefore, in order to minimize the cold-start emissions, the fast light-off techniques have been developed and presented in the literature. One of the most encouraging strategies for reducing start-up emissions is to place the light-off catalyst, in addition to the main under-body catalyst, near the engine exhaust manifold. This study numerically considers three-dimensional, unsteady compressible reacting flow in the light-off and under body catalyst to examine the impact of a light-off catalyst on thermal response of the under body catalyst and tail pipe emission. The effects of flow distribution on the temperature distribution and emission performance have also been examined. The present results show that flow distribution has a great influence on the temperature distribution in the monolith at the early stage of warm-up process and the ultimate conversion efficiency of light-ofT catalyst is severely deteriorated when the space velocity is above 100,000 h fl.