Previous work shows that auto-ignition propagation modes for strong knocking in engines are dominated by both chemical reactivity and energy density. To clarify the unique role of energy density and chemical reactivity, hotspot auto-ignition induced reaction wave propagation was investigated using direct numerical simulations, addressing the detonation regime in the detonation peninsula. Different operating conditions and mixture components were employed to design specific chemical reactivity and energy density under engine-relevant conditions. Various auto-ignition propagation modes were quantitatively investigated. The results show that unified standards for detonation development and high-accuracy excitation time are necessary for constructing a detonation peninsula. Energy density promotes detonation development and broadens the detonation regime, especially at large hotspot sizes. Meanwhile, there are positive correlations between peak pressure and energy density during detonation development, and the pressure peak can reach an amplitude beyond detonation equilibrium pressure. Furthermore, the improvement in chemical reactivity suppresses detonation development at small hotspot sizes while promoting detonation development at large hotspot sizes. But the variations in chemical reactivity caused by thermal effects show a greater significance than by fuel properties. Besides, obvious distinctions in peak pressure can be identified with the variations of reactivity gradient, and the amplitude always attains the maximum level just when detonation occurs at the edge of the hotspot. Underlying reasons are ascribed to the initial non-uniform distribution of energy density within the hotspot. Meanwhile, the reactivity progress of the remaining mixtures also affects energy density outside the hotspot.

先前的工作表明，发动机强爆震的自燃传播模式受化学反应性和能量密度的支配。为了阐明能量密度和化学反应性的独特作用，使用直接数值模拟研究了热点自燃诱导的反应波传播，解决了爆轰半岛的爆轰机制。采用不同的操作条件和混合物成分来设计发动机相关条件下的特定化学反应性和能量密度。定量研究了各种自燃传播模式。结果表明，要建立起爆半岛，需要统一的爆轰发展标准和高精度的激发时间。能量密度促进了爆轰的发展并扩大了爆轰范围，特别是在大的热点尺寸下。同时，爆轰发展过程中的峰值压力与能量密度呈正相关，压力峰值可以达到超过爆轰平衡压力的幅度。此外，化学反应性的提高抑制了小热点尺寸的爆轰发展，同时促进了大热点尺寸的爆轰发展。但是由热效应引起的化学反应性变化比燃料特性更重要。此外，随着反应性梯度的变化，峰值压力有明显的区别，并且在热点边缘发生爆轰时，振幅总是达到最大水平。根本原因是热点内能量密度的初始分布不均匀。同时，剩余混合物的反应进程也会影响热点外的能量密度。