电控LPG发动机稀限判据的研究

Study on the Criterions of Lean Burn Limit for an LPG EFI Engine

分析了电控低压气体喷射的LPG在小型点燃式发动机上应用时,有关稀限判据参数的选取和依据。试验在一台四冲程、水冷125 mL单缸电喷发动机上进行。通过研究的缸内外多种参数的分析发现,可作为LPG燃烧稀限判据的参数有平均指示压力变动系数—经典的稀限判据,HC排放值,HC排放升高率,失火率及最高燃烧压力曲轴转角位置变动系数。试验发动机可以取平均指示压力变动系数15%、HC排放500×10-6和HC排放升高率2 000×10-6以及失火率1%及最高燃烧压力曲轴转角位置变动系数50%作为LPG燃烧稀限的判据。

Based on electronic low-pressure gaseous injection, the comparing analysis of several methods for the criterions of lean burn limit in an LPG engine is presented. Experiments were carried out in a single cylinder, four-stroke, water-cooled, 125 mL engine with electronically controlled LPG injection. Through analyzing the multi-parameters inside and outside the cylinder, it was found that the variation coefficient of indicated pressure which is the classical judgment of lean burn limit, the HC emission, HC emission increasing gradient, the misfiring ratio and the variation coefficient of the crank angle of the maximum cylinder pressure can be used as the criterions for lean burn limit determination. For the test engine, 15% of the variation coefficient of indicative mean pressure, 500×10^-6 of HC emission, 2000 × 10^-6 of HC emission increasing ratio, 1% of misfiring ratio and 50% of the variation coefficient of the crank angle of the maximum cylinder pressure can be used as the judgment criterions of LPG lean burn limits.