张宁，张帆，钟生辉，于江飞，彭志军，刘海峰.乙醇预混火焰胞状不稳定性的数值模拟和理论研究[J].内燃机工程,2020,41(2):25-31.
乙醇预混火焰胞状不稳定性的数值模拟和理论研究
Numerical and Theoretical Investigation of Cellular Instability of Premixed Ethanol/Air Flames
DOI：10.13949/j.cnki.nrjgc.2020.02.004
关键词:乙醇  流体动力学不稳定性  热扩散不稳定性  数值模拟  内燃机
Key Words:ethanol  hydrodynamic instability  thermal-diffusion instability  numerical simulation  internal combustion engine
基金项目:国家自然科学基金项目(51876139,51506146）
作者单位
张宁，张帆，钟生辉，于江飞，彭志军，刘海峰 1.天津大学 内燃机燃烧学国家重点实验室，天津 300072； 2.国防科学技术大学 超燃冲压发动机科学与技术实验室，长沙 410073 
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摘要:在一个恒定体积的密闭容器中开展了一系列圆柱形膨胀乙醇预混火焰胞状不稳定性的数值模拟研究，并通过临界贝克莱数、扰动对数增长率和临界火焰半径等理论分析研究了乙醇预混火焰胞状不稳定性。结果表明，在初始压力1 MPa、初始温度358 K、当量比0.8~1.6条件下，乙醇预混火焰胞状不稳定性非单调性增加，在当量比为1.2时不稳定性最为强烈。原因是热扩散（thermal diffusion, TD）不稳定性分子扩散影响明显，随着当量比的变化而急剧变化，当量比增加，扰动对数增长率先增大后减小；相反，流体动力学不稳定性对当量比并不敏感。此外，在当量比低于1.2时，几乎保持恒定的临界贝克莱数和急剧减小的火焰厚度导致临界火焰半径大幅下降，并在1.2处达到最小值。数值模拟和理论研究显示出一致的结果。
Abstract:A series of numerical simulations of premixed cylindrical expanding ethanol/air flames in a constant volume were performed to investigate the cellular instability. Then a theoretical analysis in terms of critical Peclet number, logarithmic growth rate and critical flame radius was carried out to explore the flame instability. The results demonstrate that at pressure of 1 MPa and temperature of 358 K, ethanol/air flame cellular instability increases non-monotonically with the equivalence ratio changing from 0.8 to 1.6 and has the most intense instability when the equivalence ratio is 1.2. It is found that thermal-diffusion instability changes dramatically with increased equivalence ratio mainly due to molecular diffusion, and logarithm growth rate increases first and then decreases. On the contrary, hydrodynamic instability is insensitive to the equivalence ratio. Finally, the almost constant critical Peclet number and remarkably reduced flame thickness lead to a great decrease in critical flame radius when the equivalence ratio is less than 1.2, and critical flame radius reaches the minimum when the equivalence ratio is 1.2. Both numerical and theoretical investigations showed a consistent result.
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