氢气-乙醇-空气预混层流燃烧特性仿真研究

Simulation Study on Laminar Combustion Characteristics of Hydrogen-Ethanol-Air Premix

利用数值模拟方法,采用Chemkin软件分析计算得到氢气-乙醇-空气预混燃料的层流燃烧速度、密度比、绝热火焰温度、火焰厚度、敏感性系数和主要自由基的摩尔分数等数据。结果表明,预混火焰的层流燃烧速度与初始压力呈负相关,在所有初始条件下,其峰值出现在当量比Φ为1.2左右,并且随着氢气含量的增加,峰值向富燃侧移动。密度比和绝热火焰温度都随着当量比的增大而呈现先升后降的变化趋势,而火焰厚度则表现出相反的规律。绝热火焰温度在Φ=1.1时达到最高,比层流燃烧速度达到最高值的当量比小,这是由于实验中存在较大的热损失。此外,初始压力的升高会使得火焰厚度变薄,导致火焰表现出不稳定的趋势。在任何工况下,H+O_(2)=O+OH均为敏感性系数最高的基元反应,该基元反应的敏感性系数与H摩尔分数均在Φ=1.2时达到最大值。

The laminar burning velocity,density ratio,adiabatic flame temperature,flame thickness,sensitivity coefficient,and molar fraction of main free radicals of the hydrogen-ethanol-air premixed fuel were analyzed and calculated by using numerical simulation with Chemkin software.The results showed that the laminar burning velocity of the premixed flame was negatively correlated with the initial pressure,and the peak occurred around the equivalence ratioΦof 1.2 for all initial conditions,and the peak shifted toward the rich combustion side with the increase of hydrogen content.Both the density ratio and adiabatic flame temperature showed a tendency to increase first and then decrease with the increase of the equivalence ratio,while the flame thickness exhibited the opposite trend.The adiabatic flame temperature reached its highest value atΦ=1.1,which was smaller than the equivalence ratio at which the laminar burning velocity peaked.This discrepancy could be attributed to the presence of substantial heat losses in the experimental setup.In addition,the increase in initial pressure made the flame thickness thinner,causing the flame to exhibit an unstable tendency.The H+O_(2)=O+OH was the elementary reaction with the highest sensitivity coefficient at all operating conditions,and the sensitivity coefficient for this radical reaction with respect to the H molar fraction reached its highest value atΦ=1.2.