微尺度扩散火焰特性的数值解析

NUMERICAL ANALYSIS OF MICRO DIFFUSION FLAMES

本文以均匀空气流中圆管形成的甲烷射流扩散火焰为对象,用数值解析的方法研究了微尺度扩散火焰的火焰结构和燃烧特性。燃烧反应采用甲烷/空气一步总包反应,喷管壁面采用绝热条件。在Re一定情况下,改变喷口尺寸和喷口流速考察了微扩散火焰的结构和火焰熄灭的尺度效应。数值结果表明,随着喷口直径的增大,微火焰的上方出现回流; Re=12条件下,在喷口直径=0.07 mm时存在熄灭极限;稳定燃烧区的最小发热率约为0.5 W;微尺度条件下,Da数对火焰结构和火焰的熄灭有一定的影响。

Circular jet methane-air diffusion micro-flames in homogenous air are investigated numerically with one-step reaction model and adiabatic wall boundary condition. To discuss the effects of flame structure and size on flames extinction, the burner diameter and inlet velocity are changed under the condition of constant Reynolds number. Calculation results show that, back flow appears above the micro-flames with the increase of the nozzle diameter; extinction behavior takes place when burner diameter is about 0.07 mm; the minimal total heat release rate is about 0.5 W in the stable flame zone; the flame structure and extinction limitation are obviously effected by Damkohler number.