The advancement of highly boosted internal combustion engines (ICEs) with high thermal efficiency is mainly constrained by knock and super-knock, respectively, due to the end gas autoignition and detonation development. The pressure wave propagation and reflection in a small confined space may strongly interact with local end gas autoignition, leading to combustion characteristics different from those in a large chamber or open space. The present study investigates the transient autoignition process in an iso-octane/air mixture inside a closed chamber under engine-relevant conditions. The emphasis is given to the assessment of effects of the pressure wave-wall reflection and the mechanism of extremely strong pressure oscillation typical for super-knock. It is found that the hot spot induced autoignition in a closed chamber can be greatly affected by shock/pressure wave reflection from the end wall. Different autoignition modes respectively from the hot spot and the end wall reflection are identified. A non-dimensional parameter quantifying the interplay between different length and time scales is introduced, which helps to identify different autoignition regimes including detonation development near the end wall. It is shown that detonation development from the hot spot may cause super-knock with devastating pressure oscillation. However, the detonation development from the end wall can hardly produce pressure oscillation strong enough for the super-knock. The obtained results provide a fundamental insight into the knocking mechanism in engines under highly boosted conditions.

由于末端气体自燃和爆炸的发展，具有高热效率的高增压内燃机（ICE）的发展主要受到爆震和超级爆震的限制。在狭窄的密闭空间中，压力波的传播和反射可能会与局部终端气体的自燃强烈相互作用，从而导致燃烧特性不同于大腔室或开放空间中的燃烧特性。本研究研究了在与发动机相关的条件下，密闭室内的异辛烷/空气混合物中的瞬态自燃过程。重点是评估压力波壁反射的影响以及超级爆震中典型的极强压力振荡的机理。发现在封闭室内热点引起的自燃会受到来自端壁的冲击/压力波反射的极大影响。分别从热点和端壁反射中识别出不同的自燃模式。引入了量化不同长度和时间尺度之间相互作用的无量纲参数，该参数有助于识别不同的自燃机制，包括端壁附近的爆炸发展。结果表明，从热点处引爆可能会导致超爆震，并产生破坏性的压力振荡。然而，从端壁的爆震发展几乎不会产生对于超级爆震足够强的压力振荡。获得的结果提供了对发动机在高增压条件下的爆震机理的基本认识。