氢气添加对乙醇/空气预混火焰燃烧特性影响的数值模拟研究

Numerical study on effects of hydrogen addition on combustion characteristics of ethanol/air premixed flames

通过对不同混合比率的乙醇/氢气/空气燃烧特性进行数值模拟,研究氢气添加量对点火延迟时间、层流燃烧速度、火焰厚度、化学反应滞留时间及组分分布情况的影响。研究发现一定程度上氢气添加量的增加能够缩短混合气体的点火延迟时间,并且氢气对点火延迟时间的影响随着温度的升高而逐渐减小。随着混合比率的增大,层流燃烧速度增大,并且在混合比率大于0.4时显著增大。火焰厚度及化学反应滞留时间随氢气增加而逐渐减小。此外,进一步分析组分分布情况得知氢气添加使火焰中H*、O*、OH*自由基摩尔分数峰值增大,并且H+O+OH摩尔分数峰值与层流燃烧速度存在线性关系。

A numerical study on ethanol/hydrogen/air premixed flames with various hydrogen fractions is carried out to investigate the effects of hydrogen addition on the ignition delay time, laminar burning velocity as well as flame structure. When more hydrogen is added to the fuel, the ignition delay time is shortened to some extent, and the effects of hydrogen addition on ignition delay time are weakened with increasing temperature. The laminar burning velocity increases with the increase of the mixing ratio, particularly when the mixing ratio is greater than 0. 4. Flame thickness and characteristic residence time gradually decrease with the increase of hydrogen fraction. In addition, further analysis of the distribution of different species shows that hydrogen addition causes higher H^＋, O^＋ , OH^＋ peak concentrations, and there is a linear correlation between the peak concentration of H＋O＋OH and the laminar burning velocity.