应用多区模型预测HCCI发动机的运行范围

Prediction of Operating Range for HCCI Engine Based on Multi-Zone Model

应用多区模型预测了均质压燃(HCCI)发动机的运行范围。运行范围的边界由敲缸(由声响强度计算)、部分燃烧(由燃烧效率计算)和循环变动(由平均有效压力对进气温度的敏感度计算)确定。通过模拟一台以异辛烷为燃料的HCCI发动机发现,在不同当量比和进气温度下,计算得到的敲缸极限和循环变动极限均与试验相当吻合,从而很好地再现了HCCI发动机的运行范围。进一步研究运行范围随转速的变化,讨论了通过调节进气温度和当量比,在不同转速下HCCI发动机的最大可运行范围。最后考察了通过使用变压缩比和增压两种策略扩展HCCI发动机运行范围的潜力。结果表明:通过调节压缩比可以有效地控制着火点,在向低负荷扩展方面,使用高的进气温度和较低的压缩比显得更为有利;在向高负荷扩展方面,使用高压缩比更好;而增压有利于HCCI发动机的控制,同时增加了向高负荷扩展的范围。

By using multi-zone model,the operating range of homogeneous charge compression ignition（HCCI） engine was predicted,the boundaries of its operating range were determined by knocking limit,partial combustion,and cycle-to-cycle variation（represented respectively by the sound intensity,combustion efficiency and sensitivity of mean effective pressure to intake temperature）.A HCCI engine fueled with iso-octane was simulated,and it is found that the knocking limit and the cycle-to-cycle variation predicted by this model show a satisfactory agreement with the measured under different intake temperature and equivalence ratio,and the model reproduces the engine operating range well.The model was applied to examine the operating range at different speeds by varying intake temperature and equivalence ratio.The potentials to extend the operating range of HCCI engines through two strategies,i.e.variable compression ratio and boost,were investigated.The results indicate that ignition point can be efficiently controlled by adjusting compression ratio.The low load range can be extended with intake temperature increasing and compression ratio decreasing,and higher compression ratio is beneficial to extend the high load range.Boosting is helpful to control of the engine combustion,meanwhile further extension of high load range can be realized.