基于可视化快速压缩机的正庚烷末端自燃行为研究

doi:10.3969/j.issn.1674-8484.2026.04.004

摘要/Abstract

摘要：

为揭示高反应活性燃料末端自燃诱发爆震的演化特征及其爆震强度影响因素，该文基于可视化快速压缩机（RCM）研究了化学计量比正庚烷/空气混合气在点燃条件下的自燃和爆震行为。采用高速摄影同步高频压力采集识别了正庚烷自燃及爆震传播特征，并结合0维化学反应计算工具分析末端混合气自燃过程的热力学路径。结果表明：正庚烷爆震强度与初始能量密度呈正相关。相同初始温度下，初始压力升高使爆震强度增大；正庚烷爆震强度随点燃-自燃消耗比例增加而降低，且初始温度越高，爆震强度对该比例的敏感性越强。相同初始压力下，初始温度升高使自燃提前但压力震荡减弱；当初始温度由 615 K 升高至 685 K 时，正庚烷末端混合气自燃前经历的温升由约 135 K 降低至约 55 K，燃烧过程由受火焰传播显著影响转变为自燃主导。研究表明，较高的反应活性会使得正庚烷在进一步受到火焰压缩前提前发生自燃，导致自燃时刻末端混合气的热力学路径难以进入负温度系数（NTC）区域；高反应活性燃料的爆震分析需结合能量密度、火焰/自燃消耗比例等因素综合评价。

关键词: 快速压缩机（RCM）, 爆轰, 爆震强度, 正庚烷, 混合气自燃

Abstract:

This study investigated the auto-ignition and knock behavior of stoichiometric n-heptane/air mixtures under spark-ignition conditions using an optical rapid compression machine (RCM) to reveal the evolution characteristics of knock induced by end-gas auto-ignition of highly reactive fuels and the factors that affect knock intensity. High-speed photography synchronized with high-frequency pressure acquisition was employed to identify the knock characteristics of n-heptane. In addition, zero-dimensional chemical kinetic calculations were conducted to analyze the thermodynamic trajectory of the end-gas during auto-ignition. The results show that the knock intensity of n-heptane is positively correlated with the initial energy density. At the same initial temperature, increasing the initial pressure enhances the knock intensity; the knock intensity decreases with increasing spark-ignited/auto-ignited consumption ratio, and the sensitivity of knock intensity to this ratio becomes stronger at higher initial temperatures. At the same initial pressure, increasing the initial temperature advances auto-ignition but weakens the pressure oscillation; as the initial temperature increases from 615 K to 685 K, the temperature rise experienced by the end-gas before auto-ignition decreases from approximately 135 K to 55 K, and the combustion process shifts from being significantly affected by flame propagation to being dominated by auto-ignition. The results indicate that the high reactivity of n-heptane causes the end-gas to auto-ignite before further compression by flame propagation, making its thermodynamic trajectory at the auto-ignition timing difficult to enter the negative temperature coefficient (NTC) region. Therefore, knock analysis of highly reactive fuels should comprehensively consider energy density and the relative contribution of flame propagation and auto-ignition.

Key words: rapid compression machine (RCM), detonation, knock intensity, n-heptane, mixture auto-ignition

中图分类号:

TK407.9

刘伟, 齐运亮, 曹曦, 王志. 基于可视化快速压缩机的正庚烷末端自燃行为研究[J]. 汽车安全与节能学报, 2026, 17(4): 459-466.

LIU Wei, QI Yunliang, CAO Xi, WANG Zhi. Investigation of n-heptane end-gas auto-ignition behaviors using an optical rapid compression machine[J]. Journal of Automotive Safety and Energy, 2026, 17(4): 459-466.

图/表 12

图1 实验台架示意图

序号	当量比	空气/ X气体			上止点		压缩比
序号	当量比	X为正庚烷	X为氧气	X为氮气	T₀ / K	p₀/ MPa	压缩比
1	1	1.87	20.61	77.52	615	1.0~1.3	9.2
2					650		11.0
3					685		13.3

表1 实验工况及混合气配比

图2 机理验证

图3 不同初始热力学条件下正庚烷爆震燃烧的压力曲线对比

图4 不同初始热力学条件下正庚烷的爆震强度

图5 不同初始温度条件下正庚烷的爆震燃烧图像

图6 正庚烷爆震燃烧原始图像与处理后图像对比

图7 不同初始热力学条件下正庚烷自燃时末端混合气压力

图8 爆震强度与点燃-自燃比例之间的关系

图9 BMF与SICI之间关系

图10 正庚烷末端混合气在不同实验条件下的热力学状态演化

图11 异辛烷末端混合气在不同实验条件下的热力学状态演化[30]

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