Abstract Diluent gases are used in practical industrial applications that involve flame propagation and detonation. In this study, we investigated the effect of diluent gases on end-gas autoignition and detonation development in a constant volume combustion chamber. High-speed Schlieren photography was employed to capture the flame–shock wave interaction and detonation evolution. Two reactants (hydrogen and methane) and three diluent gases (argon, nitrogen, and carbon dioxide) were used for the process. In this study, statistical analysis confirmed that the ratio of maximum pressure to equilibrium pressure (Pmax/Pequ) can be a criterion to determine the occurrence of end-gas autoignition. In addition, it was observed that the mechanism of end-gas autoignition with detonation development was dominated by the flame propagation velocity and associated shock wave intensity in the present experimental conditions. With an increase in the flame propagation velocity, the combustion mode transitioned from normal combustion to autoignition Mode 1 (the end gas suffers two compressions by shock wave before autoignition), and to autoignition Mode 2 (the end gas suffers one compression by shock wave before autoignition), which was observed for different reactants and diluent gases. The diluent acted as an inhibitor for the chemical reaction and moderated the flame acceleration, and thus, restrained the end-gas autoignition and detonation intensity. CO2 is a better inhibitor of end-gas autoignition with high-pressure oscillation and detonation than N2 and Ar; CO2 can be employed to prevent knock or super-knock in boosted gasoline engine. Further, we discussed the basis of random location of the autoignition kernel, and the influence of the location on measuring the intensity and destructive capability of the detonation. Moreover, owing to the addition of carbon to the combustion, a blue–white light was observed after the propagation of the shock wave.

中文翻译：

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稀释气体对密闭空间内尾气自燃和燃烧模式的影响

摘要 稀释气体用于涉及火焰传播和爆炸的实际工业应用中。在这项研究中，我们研究了稀释气体对恒容燃烧室中尾气自燃和爆震发展的影响。采用高速纹影摄影来捕捉火焰-冲击波相互作用和爆轰演变。该过程使用两种反应物（氢气和甲烷）和三种稀释气体（氩气、氮气和二氧化碳）。在本研究中，统计分析证实，最大压力与平衡压力之比（Pmax/Pequ）可以作为判断尾气自燃发生的标准。此外，据观察，在目前的实验条件下，伴随爆炸发展的尾气自燃机制受火焰传播速度和相关冲击波强度的支配。随着火焰传播速度的增加，燃烧模式从正常燃烧过渡到自燃模式1（自燃前尾气受到冲击波压缩两次），再过渡到自燃模式2（自燃前尾气受到冲击波压缩一次）。自燃），观察到不同的反应物和稀释气体。稀释剂作为化学反应的抑制剂，缓和了火焰的加速，从而抑制了尾气自燃和爆轰强度。CO2 是比 N2 和 Ar 更好的具有高压振荡和爆轰的尾气自燃抑制剂；CO2 可用于防止增压汽油发动机中的爆震或超级爆震。进一步讨论了自燃核随机定位的依据，以及定位对测量爆轰强度和破坏能力的影响。此外，由于在燃烧中添加了碳，在冲击波传播后观察到蓝白光。