基于Damköhler数的蒸发式值班火焰稳定器贫熄边界分析方法研究

Analysis method research on lean blowout limit of evaporative pilot flameholder based on Damköhler number

为探究蒸发式火焰稳定器的贫油熄火性能的分析方法,在来流温度为400~640 K,尾流速度为85~153 m/s条件下,以蒸发式火焰稳定器为研究对象,开展了贫油熄火试验与数值模拟计算,得出了蒸发式火焰稳定器不同工况下的全局和局部Damköhler数(Da)分布特性。研究结果表明:(1)随着火焰稳定器尾缘速度增加,熄火油气比在高来流温度时呈现单调递增的趋势,而低来流温度时则呈现先减小再增加的趋势;随着来流温度的升高,熄火油气比减小。(2)随着燃油流量的增加,高局部流动时间和低局部化学时间区域均沿轴向变长。高Da区域主要集中在火焰稳定器剪切层附近,随着燃油流量的增加,高Da区域逐渐合并。(3)关键反应区内的全局流动时间随尾缘速度增加而缩短,随温度的升高而延长;关键反应区内的全局化学时间随尾缘速度增加而呈现先缩短后延长的趋势,随着来流温度升高呈现单调缩短的趋势。(4)不同熄火点工况下关键反应区内的Da在1左右,表明该方法可以对蒸发式火焰稳定器贫油熄火进行预测,并在不同来流工况具有一定的普适性。

To investigate the analysis method of the lean-blowout performance of the evaporation flamehold⁃er,under the conditions of the inlet temperature of 400~640 K and the tailing velocity of 85~153 m/s,the leanblowout experiment and numerical simulation were carried out with the evaporation flameholder as the research object to get the distribution characteristics of the global and local Damköhler number(Da)under different work⁃ing conditions.The research results show that:(1)As the trailing-edge velocity of the flameholder increases,a monotonically increasing trend in the lean blowout fuel/air ratio is observed at high inlet temperatures,while a trend of decreasing before increasing is observed at low inlet temperatures.As the inlet temperature rises,a de⁃crease in the lean blowout fuel/air ratio is observed.(2)With an increase in fuel flow,both the high local flow time and the low local chemical time regions are extended along the axial direction.The high Da region primarily concentrates near the flameholder’s shear layer,and as fuel flowrate increases,the high Da regions gradually merge.(3)The global flow time within the key reaction zone decreases with an increase in the trailing-edge ve⁃locity and increases with rising inlet temperatures.The global chemical time within the key reaction zone exhibits an initial decrease followed by an increase as velocity increases,while it decreases monotonically with inlet tem⁃perature increasing.(4)Under various inlet conditions,the Da in the key reaction zone at the blowout limit is ap⁃proximately around 1,signifying that the prediction of lean blowout for the evaporative flameholder can be achieved by this method.A certain degree of universality for different inflow conditions is demonstrated.