\r刘昌文，马国斌，潘家营，卫海桥，胡 祯\r
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AuthorsHTML:\r刘昌文，马国斌，潘家营，卫海桥，胡 祯\r
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AuthorsListE:\rLiu Changwen，Ma Guobin，Pan Jiaying，Wei Haiqiao，Hu Zhen\r
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AuthorsHTMLE:\rLiu Changwen，Ma Guobin，Pan Jiaying，Wei Haiqiao，Hu Zhen\r
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Unit:\r天津大学机械工程学院，天津 300072\r
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Unit_EngLish:\rSchool of Mechanical Engineering，Tianjin University，Tianjin 300072，China\r
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Abstract_Chinese:\r爆震现象是限制现代高强化内燃机热效率大幅度提高的关键技术瓶颈，而目前其机理尚不完全清楚．针对高强化内燃机在低速大负荷条件下存在的爆震及超级爆震异常燃烧现象，基于一台重复性良好的可视化快速压缩机，以自燃理论与现有爆震机理为理论基础，以测量燃烧室内瞬态压力以及分析高速摄影燃烧图像为主要研究手段，开展了燃烧边界条件对异辛烷-空气混合气自燃及爆震影响的试验研究，量化研究了有效能量密度、自燃模式与爆震强度之间的影响关系，初步探索了壁面温度对爆震强度的作用机理．结果表明：在当前试验工况下，随着初始温度的提高，异辛烷自燃时刻逐渐提前，爆震强度逐渐增强并出现了超级爆震；与初始温度对自燃时刻及爆震的影响规律类似，自燃时刻、爆震特性与初始压力呈正相关性；在当量比趋近于1 时，异辛烷爆震强度显著增强并出现了超级爆震，而在当量比稍浓时有所减弱；但是综合而言，相较于初始温度，爆震强度对初始压力和当量比更加敏感；同时，爆震强度与可燃混合气有效能量密度密切相关，随着有效能量密度提高，正常燃烧逐渐向强烈爆震和超级爆震转移；另外，壁面温度对爆震强度也具有重要影响，相同有效能量密度条件下，壁面温度越高，爆震强度越强，甚至会诱发超级爆震．\r
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Abstract_English:\rEngine knock is a major technical obstacle to achieving significant improvements in thermal efficiency in modern downsized internal combustion engines. As yet，we lack a thorough understanding of its mechanism. In this study，we investigated abnormal combustion phenomena involving knock and super-knock in downsized internal combustion engines under low speed and high load conditions. Specifically，we conducted experiments on the effects of the combustion boundary conditions of iso-octane air mixtures on auto-ignition and knock. In the experiments，we measured the transient pressure in the combustion chamber of a rapid compression machine and then analyzed highspeed photographic combustion images，based on the auto-ignition theory and our current understanding of the knock mechanism. In addition，we quantitatively studied the mutual influences of the effective energy density，autoignition mode，and knock intensity，and explored the operating mechanism involved in the effect of wall temperature on knock intensity. The results show that with increases in the initial temperature，the iso-octane’s auto-ignition timing gradually advances and knock intensity is gradually enhanced with super-knock occurring under these experimental conditions. The effect of initial temperature on the auto-ignition timing and knock are similar，with both being positively correlated with the initial pressure. As the tendency of the equivalence ratio moves to 1，the iso-octane knock intensity is significantly increased and super-knock occurs，and is conversely weakened when the equivalence ratio is slightly rich. However，knock intensity is generally more sensitive to the initial pressure and equivalence ratio than the initial temperature. Engine knock is closely associated with the effective energy density of the mixture，i.e.，as the effective energy density is increased，a transition occurs from normal combustion to conventional knock and super-knock. In addition，wall temperature has a significant influence on knock intensity，i.e.，under the same effective energy density conditions，a higher wall temperature leads to stronger knock intensity and can even induce superknock.\r
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Keyword_Chinese:快速压缩机；超级爆震；当量比；能量密度；壁面温度\r

Keywords_English:rapid compression machine；super-knock；equivalence ratio；energy density；wall temperature\r


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