水蒸气对火焰特性和碳烟生成影响的数值模拟

在协流空气中添加不同的虚拟组分,基于完全解耦法数值模拟研究常压条件下乙醇/空气同轴层流扩散火焰中水蒸气对火焰特性和碳烟生成的影响。研究结果显示:加入水蒸气后,火焰的最高温度和最大碳烟体积分数均降低;水蒸气通过稀释效应、化学效应、热力学效应和辐射效应影响火焰特性和碳烟生成,其中化学效应和稀释效应占主导地位;水蒸气的化学效应会改变O、H、H2和OH等组分的摩尔分数,OH浓度的增加促进了碳烟的氧化。水蒸气的化学效应也会影响苯(A1)、苾(A4)、炔丙基(C3H3)和乙炔(C2H2)等碳烟生成中间产物的摩尔分数,降低碳烟核心的成核速率和表面增长速率。

Numerical analysis of effects of water vapor addition on the flame properties and soot formation in ethanol coflow flame

Based on the complete decoupling method,different virtual components are added to the coflow air,the effects of water vapor on the flame properties and soot formation characteristics in an ethanol/air coflow laminar diffusion flame at atmospheric pressure are investigated with numerical simulation.The results show that,with the blending of water vapor,the peak temperature of the flame and the maximum soot volume fraction are reduced.The water vapor influence flame properties and soot formation through dilution effect,chemical effect,thermal effect and radiation effect.The chemical effect and dilution effect play dominate roles.The chemical effect affects the O,H,H 2 and OH radicals mole fraction,and the increase of OH radical enhance the oxidation of soot.The chemical effect also influences the intermediates of soot formation,such as benzene(A 1),pyrene(A 4),C 3H 3 and acetylene(C 2H 2),then reduce the rate of soot nucleation and surface growth.