Oxygen-enriched combustion of the first cycle during cold start in a liquefied petroleum gas spark-ignition engine

The first firing cycle is very important for cold-start. Misfire of the first firing cycle can lead to significant hydrocarbon (HQ emissions and affect the subsequent cycles. Research has proved that the oxygen-enriched intake air (OEA) method is a useful technique to reduce cold-phase HC and carbon monoxide (CO) emissions from automotive gasoline engines. However, few researchers have studied oxygen-enriched combustion characteristics based on the first firing cycle analysis during cold-start. The present paper presents a comparison of atmospheric air with OEA in the combustion of the first cycle during cold-start in a liquefied petroleum gas spark-ignition engine. Cylinder pressure, engine speed, HC, CO, and nitric oxide (NO) emissions were collected. The heat release rate of atmospheric air and OEA combustion are calculated. Test results show that atmospheric air and OEA have similar high transients in HC emissions at cold-start. However, OEA reduces CO emissions and increases NO emissions. Comparing the heat release rate curves, oxygen-enriched combustion can lead to heat release earlier and higher than normal air combustion.