点火位置对汽油转子发动机燃烧过程的影响

以点燃式汽油转子发动机为研究对象,建立了相应的湍流和燃烧模型,实现了发动机工作过程的三维动态模拟,并利用试验结果进行对比验证。在此模型基础上,模拟计算和分析了4种不同点火位置对缸内压力、温度、火焰传播及NO_x生成的影响。结果表明:点火位置选择在燃烧室中轴线上,与转子凹坑中心位置重合,能优化燃烧,获取较大的功率;在燃烧室后部点火时,燃烧初期火焰传播速度快,压力升高率大,但是受限于燃烧室后部燃料少,压力峰值不高,且NO_x的生成量偏高;在燃烧室前部点火时,在补燃期阶段燃烧速度最快,但是点燃后压力升高阶段的燃烧效率一般;点火位置位于燃烧中轴线两侧错位排布时,燃烧效率低下导致压力峰值最低,同时NO_x的生成量稍高;一定工况下,双点火位置的坐标分别为(10 mm,-56 mm,-37.2 mm)和(-10 mm,-56 mm,-37.2mm)时,该发动机能获得最大的功率且NO_x生成量较少。

Influence of Ignition Position on Combustion Process of Gasoline Rotor Engine

The turbulence and combustion models of gasoline rotor engine were established and 3D dynamic simulation on working process was conducted and verified with the experimental results.With the model, the influences of four kinds of ignition positions on in-cylinder pressure, temperature, flame propagation and NOx generation were calculated and analyzed.The results show that the ignition position on the chamber axis coinciding with rotor pit center can optimize the combustion and improve the power output.At the rear of the combustion chamber, the flame propagation speed and the pressure rise rate are higher, but less fuel injection leads to low pressure peak and high NOx emission.At the front of the combustion chamber, the combustion runs fast during the afterburning period, but the combustion efficiency cannot reach the optimal during the pressure rise period.When two spark plugs locate on both sides of the chamber axis, low combustion efficiency leads to the lowest pressure peak and higher NOx production.Generally, engine can output the highest power and produce relatively less NOx emission when conducting the ignition at the coordinates of (10 mm, -56 mm, -37.2 mm) and (-10 mm, -56 mm, -37.2 mm).