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本文对汽油机燃烧过程的热力模型进行了改进,在质量燃烧率的计算中直接反映紊流对燃烧过程的影响。假定压缩上止点前后的紊流场基本稳定,紊流强度是发动机转速的线性函数。以倒拖紊流场中紊流强度的实验值为基础,分别对解放CA30型汽油机和东风EQ6100型汽油机的标定工况燃烧过程进行模拟计算,并与实测示功图拟合。发现当转速一定时,对不同的燃烧室结构,燃烧过程的紊流强度值约为倒拖时的2～3倍。由此建立了相应的燃烧过程紊流强度计算公式。把该公式推广应用到上述两种机型其它工况的燃烧过程,计算结果与实测值基本一致。在热力模型中直接应用该公式预测紊流燃烧速度和质量燃烧率,不但可以提高热力模型的计算精度,而且使模型的应用更加方便,适于工程实际需要。此外还预测了点火正时和燃料当量比的变化对紊流燃烧速度、燃烧压力及燃气温度的影响。
In this paper, the thermal model of the gasoline engine combustion process is improved. The calculation of the mass combustion rate directly reflects the influence of the turbulence on the combustion process. It is assumed that the turbulent flow before and after the compression top dead center is basically stable, and the turbulence intensity is a linear function of the engine speed. Based on the experimental data of the turbulence intensity in the turbulence field, the combustion process of the CA30 gasoline engine and the Dongfeng EQ6100 gasoline engine in the calibration condition are simulated and compared with the measured dynamometer. It is found that the turbulence intensity of the combustion process is about 2 ~ 3 times higher than that of the inverted one when the rotational speed is constant for different combustion chamber structures. The corresponding calculation formula of turbulence intensity in combustion process is established. The formula is extended to the combustion of the other two operating conditions of the above two models, the calculated results and the measured values are basically the same. Applying this formula directly in the thermodynamic model to predict the turbulent combustion rate and mass burning rate can not only improve the calculation accuracy of the thermodynamic model but also make the model more convenient and suitable for the actual engineering needs. In addition, the influence of the ignition timing and the fuel equivalence ratio on the turbulent combustion speed, the combustion pressure and the gas temperature is also predicted.