不同过量空气系数下天然气发动机循环变动特性研究

Study on Cycle Variation of Natural Gas Engine under Different Excess Air Ratio

试验研究了过量空气系数对天然气发动机循环变动特性的影响，研究结果表明，当过量空气系数从1逐渐增大到1.8时，发动机的循环变动增大。最高燃烧压力（Pmax）与平均指示压力（Pmi）有一定的相关性，高的Pmax循环对应着高的Pmi，循环。高的Pmi和Pmax对应着短的火焰发展期（θd），短的50％质量已燃持续期（θx=0～0.5）和短的燃烧持续期（θd）。而且，Pmax与其对应的曲轴转角（θpmax），最大压力升高率（λpmax）与Pmi，Pmi与θx=0～0.5，θd与θb都存在很好的对应关系。

The effect of excess air ratio on natural gas engine cycle variation was researched. The results show that the cycle variation becomes serious when the excess air ratio was increased from 1 to 1.8. The maximum cylinder pressure Pmax has a certain relation to the indicated mean effective pressure Pmi, and the high Pmax cycle usually corresponds to the high Pmi cycle. Furthermore, the high Pmi and Pmax cycle corresponds to the short developing period θd, which are 50 percent mass burned duration θx=0～0.5 and short combustion duration. Besides these, there are good corresponding relations between Pmax and crank angle φpmax pressure rise rate （λpmax） and Pmi, θd and θx=0～0.5, θd and θb .