边界条件对正庚烷均质压燃燃烧过程的影响

应用零维详细化学反应动力学模型，对不同边界条件下正庚烷（n—heptane）均质压燃燃烧反应的化学反应动力学过程进行了数值模拟研究，得出了以初始温度和燃料当量空燃比这两类边界条件为函数，压缩比为17，转速为1400r／min的HCCI全工况解。结果表明：HCCI燃烧分为完全燃烧区域、低温反应和蓝焰反应区域、仅发生低温反应区域和失火区域；不发生热焰反应的关键是反应H＋O2=O＋OH进行程度浅，不能生成足够的OH自由基使CO氧化成CO2；蓝焰反应也不发生而仅发生低温反应的关键是H2O2分解反应的进行程度浅，H2O2只有在缸内温度达到1000K时才能快速分解，这就不能生成足够的OH自由基使甲醛转化成CO2低温反应和蓝焰反应区域是高CO排放区，仅发生低温反应的区域是高甲醛排放区。

Effect of Boundary Condition on HCCI Combustion Process of N-heptane

The auto-ignition and combustion mechanism of n-heptane was investigated by using a zero-dimensional thermodynamic model coupled with a detailed kinetic model under different boundary conditions. The HCCI region at compression ratio of 17 and engine speed of 1 400 r/min was summarized as the function of the initial temperature and excess air ratio. Four regions are existed, and they are the complete combustion region, the low temperature reaction and blue-flame reaction region, the sole low temperature reaction region and the non-reaction region ( misfire). The reason without hot-flame reaction is that the absence of reaction 8 ( H + O2 = O + OH) results in lacking of OH radical to oxidize CO; The key factor for sole low temperature reaction is the absence of H2O2 decomposition, and H2O2 can decompose rapidly when cylinder temperature exceeds over 1 000 K. Thus, the low temperature can not produce enough OH radical to oxidize CH2O. CO is mainly formed in low temperature reaction and blue-flame reaction region and CH2O is formed in the sole low temperature reaction region.