瓦斯爆燃火焰在波纹阻火器内淬熄特性分析

Quenching characteristics of gas deflagration flame in crimped ribbon flame arrester

  • 摘要: 研究瓦斯爆燃火焰淬熄规律是开发防爆抑爆技术的基础。为有效抑制井下爆燃事故,探究瓦斯爆燃火焰在微细孔道内部的发展规律,以波纹型阻火器为研究对象,采用大涡模拟耦合有限速率/涡耗散模型的方法对波纹型阻火器阻火单元内甲烷/空气预混火焰的淬熄过程进行三维模拟。研究基于阻火单元内部温度和化学反应速率的瞬态特征,分析了火焰淬熄机理以及入口火焰速度和壁面温度对淬熄过程的影响。结果表明,火焰在波纹型阻火器内的传播受入口处火焰和内部燃烧化学反应的共同影响;火焰速度和内部燃烧化学反应速率都随着火焰传播距离的增长逐渐降低,但内部燃烧化学反应对火焰传播的影响逐渐占据主导。阻火器壁面对燃烧化学反应有重要影响,减小燃烧化学反应区域有利于火焰的淬熄。火焰速度和燃烧化学反应速率间存在相互促进关系。入口火焰速度越大,淬熄距离越远;随着入口火焰速度增大,影响逐渐减小,火焰淬熄距离增速减小。壁面温度的改变对化学反应速率影响较小;提高壁面温度将阻碍壁面散热,使熄灭层厚度减小。壁面温度越高,火焰淬熄距离越远;入口火焰速度越大,淬熄距离增长越明显。当壁面温度足够大时,火焰将穿过阻火器,造成阻火器失效。

     

    Abstract: The research on gas deflagration flame quenching is the basis of explosion-proof and explosion suppression technology. Large eddy simulation (LES) coupled with Finite Rate/EDM was used for three-dimensional simulation on the quenching process of methane air premixed flame in the Flame-Resistant element of crimped ribbon flame arrester in order to suppress gas deflagration effectively and reveal the rule of gas deflagration flame development in the micro channel. Based on the transient characteristics of temperature and reaction rate, the mechanism of flame quenching and the effects of inlet flame velocity and wall temperature were analyzed. It has been found that the flame propagation is mainly affected by the entrance flame and the internal combustion reaction. The flame velocity and internal combustion reaction rate decrease with the development of flame. At the later stage, the influence of internal combustion reaction on flame propagation is dominant. The wall of flame arrester has an important effect on the reaction rate. Reducing the combustion reaction area is conducive to the quenching of flame. There is a positive feedback relationship between flame velocity and combustion chemical reaction rate. The quenching distance will extend with the increase of inlet flame velocity, and the growth rate will slow down. The change of wall temperature has little effect on the chemical reaction rate. Increasing wall temperature will hinder the wall heat dissipation and extend the quenching distance. The growth rate of quenching distance will be enhanced with the increase of inlet flame velocity. The flame will pass through the flame arrester when the wall temperature is high enough, resulting in the failure of the flame arrester.

     

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