The Study of the Control on The First Firing Cycle for Reducing the Cold Start Emissions in a Liquid Petrol Gas Spark Ignition Engine

The first firing cycle is very important for cold-start. Well-managed combustion of the first firing cycle can create high temperatures in the cylinder, which are beneficial for combustion on the following cycles, leading to an overall decrease the hydrocarbon (HC) and carbon monoxide (CO) emissions. The quantity of HC emissions is the criterion of optimal excess air factor judgment, however it does not give complete understanding of fuel-air mixing, combustion and emissions generation within the cylinder of a Spark Ignition (SI) engine during cold start. Transient nitric oxide (NO) emissions, which can give information about combustion, can be an additional criterion for judging the optimal excess air factor. The present paper investigated the characteristic of the transient NO emissions of the first firing cycle during cold start in an electronic fuel injected SI engine fuelled with Liquid Petrol Gas (LPG). The transient NO emissions combining with the HC and CO emissions during cold start were used to identify the combustion in the cylinder, and found the optimal spark angle and excess air factor of the first firing cycle finally. In present paper, for the first firing cycle, the optimal spark angle was 10degCA BTDC, and the excess air factor was 0.53. The method and results in this paper are helpful for adjusting the control strategy to reduce total cold start emissions.