LPG转子发动机缸内燃烧影响因素研究

建立了转子发动机的计算模型,结合自编程序在CFD软件上对转子发动机的燃烧过程进行了二维动态数值模拟,并利用实验结果进行了验证。在此基础上,计算得出缸内直喷LPG转子发动机燃烧演变过程,分析了喷嘴在3个不同位置时发动机的燃烧特性,由此确定了喷嘴安装的最佳位置,并进一步研究了该情况下喷油时刻和喷油持续期对转子发动机燃烧过程的影响。研究结果表明:在转速一定,给定喷射方向、喷射持续期和喷雾锥角时,发动机存在一个最佳喷射提前角,能使燃烧室内混合气分布合理,气缸压力峰值高,最大放热率和最大压力升高率高,燃烧持续时间短,发动机热效率高。当喷嘴位于长轴顶点时,燃烧稳定性和持续性都比其他两个位置更好,最佳喷射提前角对应的燃烧压力峰值最高;若在此最佳喷射提前角下,保持其他条件不变,改变其喷射持续期,会使最高燃烧压力和最大放热率出现一定的降低,但影响不大,其燃烧特性仍然比较理想,气缸压力峰值能达到6 MPa以上。

Affecting Factors on Combustion Progress in LPG Rotary Engine

The calculation model of rotary engine was established. Combined with the self-made program in CFD software, a 2-D dynamic simulation of the combustion process of the rotary engine was made and verified by using the experiment results. On this basis, the evolution process of combustion in direct injection LPG engine was obtained, the combustion characteristic of the engine with the three representative positions of nozzle were analyzed and the best installation position of nozzle was determined. Then a further study was conducted on the effect of the injection time and injection duration on combustion process in the rotary engine with the optimal installation position of the nozzle. The results showed that in a given speed, fuel injection direction, injection speed, injection duration and spray cone angle, the engine had a best injection advance angle that could lead to a reasonable distribution of mixture gas in the combustion chamber, a high maximum combustion pressure, maximum heat release rate and maximum pressure rise rate, a short combustion duration, and a high thermal efficiency. When the nozzle located in long axis vertex, the stability and continuity of combustion was better than the other two positions. The peak combustion pressure of the best injection advance angle was the highest. Under the optimal injection advance angle and with the other conditions unchanged, the maximum combustion pressure and maximum heat release rate appeared to reduce when changed the injection duration, but the impact was not significant. The combustion characteristics were still satisfactory, and the peak combustion pressure could reach to 6MPa above.