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首页> 外文期刊>Combustion and Flame >Differential diffusion effect on the stabilization characteristics of autoignited laminar lifted methane/hydrogen jet flames in heated coflow air
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Differential diffusion effect on the stabilization characteristics of autoignited laminar lifted methane/hydrogen jet flames in heated coflow air

机译：差异扩散对加热的同流空气中自燃层流提升的甲烷/氢气喷射火焰稳定特性的影响

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The characteristics of autoignited laminar lifted methane/hydrogen jet flames in heated coflow air are numerically investigated using laminarSMOKE code with a 57-species detailed methane/air chemical kinetic mechanism. Detailed numerical simulations are performed for various fuel jet velocities, U-0, with different hydrogen ratio of the fuel jet, R-H, and the inlet temperature, T-0. Based on the flame characteristics, the autoignited laminar lifted jet flames can be categorized into three regimes of combustion mode: the tribrachial edge flame regime, the Moderate or Intense Low-oxygen Dilution (MILD) combustion regime, and the transition regime in between. Under relatively low temperature and high hydrogen ratio (LTHH) conditions, an unusual decreasing liftoff height, H-L, behavior with increasing U-0 is observed, qualitatively similar to those of previous experimental observations. From additional simulations with modified hydrogen mass diffusivity, it is substantiated that the unusual decreasing H-L behavior is primarily attributed to the high diffusive nature of hydrogen molecules. The species transport budget, autoignition index, and displacement speed analyses verify that the autoignited lifted jet flames are stabilized by autoignition-assisted flame propagation or autoignition depending on the combustion regime. Chemical explosive mode analysis (CEMA) identifies important variables and reaction steps for the MILD combustion and tribrachial edge flame regimes. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：使用具有57种详细甲烷/空气化学动力学机理的laminarSMOKE代码，对在加热的同流空气中自动点燃的层流提升的甲烷/氢气喷射火焰的特性进行了数值研究。针对各种燃料喷射速度U-0（具有不同的燃料喷射氢比R-H和进口温度T-0）执行了详细的数值模拟。根据火焰特性，可将自燃层状举升火焰分为三种燃烧模式：三臂边缘火焰模式，中度或强烈低氧稀释（MILD）燃烧模式，以及两者之间的过渡模式。在相对较低的温度和高氢比（LTHH）条件下，观察到了异常升高的上升高度H-L，随U-0的增加而发生的行为，在质量上与以前的实验观察到的相似。从具有改进的氢质量扩散率的其他模拟中，可以证实异常降低的H-L行为主要归因于氢分子的高扩散性质。物质运输预算，自燃指数和位移速度分析证明，根据燃烧方式，自燃辅助的火焰传播或自燃可稳定自燃的喷射火焰。化学爆炸模式分析（CEMA）确定了MILD燃烧和三臂边缘火焰状态的重要变量和反应步骤。 （C）2018年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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