LPG点燃式发动机冷起动首循环进气富氧试验研究

基于循环控制,详细研究了LPG点燃式发动机冷起动首循环进气富氧的燃烧及排放特性。试验在一台电控LPG进气喷射单缸风冷四冲程125 mL发动机上进行,采用膜式富氧方法实现富氧进气燃烧。研究表明:当过量空气系数大于0．7时,富氧进气燃烧缸压峰值与空气相比增加不显著,此后随混合气加浓,富氧进气燃烧缸压峰值开始明显大于常规空气进气燃烧;过量空气系数在0．4～0．876时,富氧进气燃烧与常规空气进气燃烧相比,HC排放没有较大降低,在此范围之外,富氧显著降低HC排放;过量空气系数在0．4～0．7,富氧与空气相比CO显著降低;富氧进气燃烧,使得首循环NO排放大幅增加;计算放热率发现,富氧燃烧速度比常规空气进气燃烧更快,放热更集中。

Experimental Study of Oxygen-Enriched Combustion in the First Cycle of Cold Start in a LPG SI Engine

The First Firing Cycle (FFC) is very important for cold-start. Misfire of the first firing cycle can lead to significant HC emissions and affect the subsequent cycles. Researches have showed that Oxygen-Enriched intake Air (OEA) method is a useful technique to reduce cold-phase HC and CO emissions from automotive gasoline engines. But few researches have studied oxygen-enriched combustion characteristics based on the first firing cycle analysis during cold start. The present paper presents the oxygen-enriched combustion of the first cycle during cold start in a LPG SI engine, and cylinder pressure, engine speed, HC, CO and NO emissions were measured, and heat release rate of oxygen-enriched combustion was calculated. The studying results show that OEA has the same HC emission level comparing to that fed with air over a wide range, but OEA reduces CO emissions and increases NO emissions. Heat release analysis shows that oxygen-enriched combustion has fast burning speed and high heat release rate.