Knock formation and its intensity for a stoichiometric ethanol/air mixture under a representative end-gas auto-ignition condition in IC engines with temperature inhomogeneities are investigated using multi-dimensional direct numerical simulations (DNS) with a 40-species skeletal mechanism of ethanol. Two- and three-dimensional simulations are performed by systematically varying temperature fluctuations and its most energetic length scale, l_T. The volumetric fraction of the mixture regions that have the propensity to detonation development, F_D, is proposed as a metric to predict the amplitude of knock intensity. It is found that with increasing l_T, F_D shows a good agreement with the heat release fraction of the mixture regions with pressure greater than equilibrium pressure, F_H. The detonation peninsula is well captured by F_D and F_H when plotting them as a function of the volume-averaged ξ, $\overline{\xi },$ ($\xi =a/S_{sp}$ is the ratio of the acoustic speed, a to the ignition front speed, S_sp). Decreasing l_T is found to significantly reduce the super-knock intensity. The results suggest that decreasing l_T, as in engines with tumble designs resulting in a smaller turbulence scale, will be effective in mitigating the the super-knock development.

使用具有40种骨骼机理的多维直接数值模拟（DNS），研究了具有代表性的终端燃气自燃条件下具有温度不均匀性的IC发动机中化学计量的乙醇/空气混合物的爆震形成及其强度。二维和三维模拟是通过系统地改变温度波动及其最有效的长度尺度L _{T来进行的}。具有爆轰发展倾向的混合区域的体积分数F _D被提议为预测爆震强度幅度的度量。发现随着l _T，F _D的增加与压力大于平衡压力F _H的混合区域的放热分数显示出良好的一致性。将F _D和F _H绘制为体积平均ξ的函数时，F _D和F _H可以很好地捕获爆炸半岛。$\overline{\xi }，$ （$\xi =\mathrm{一种}/{\mathrm{小号}}_{sp}$是声速a与点火前速度S _sp的比。发现降低l _T会显着降低超级爆震强度。结果表明，降低l _T（如采用滚珠设计的发动机，从而减小湍流范围）将有效减轻超级爆震的发展。