基于网格化Damk?hler数的燃烧室贫熄边界预测方法探究

Study on Lean Blow-off Prediction Method for Combustor Based on Meshed Damk?hler Number

发展了一种基于网格化Damkohler(Da)数的贫熄预测方法.将基于OH基浓度定义的反应区均匀划分为尺度一致的子区域,以降低反应区组分、温度不均匀对预测精度的影响.针对整个反应区及反应区内的每个子区域分别计算Da数.分别采用新鲜混气在反应区(或子区域)的实际停留时间和能够触发反应的最短停留时间定义流动时间和化学反应时间.局部Da数计算结果表明,不同流量下的近贫熄工况,燃烧核心集中在回流区上游滞止点附近,设计工况下的燃烧核心却集中在回流区下游滞止点附近.整体Da数计算结果表明,对于空气来流流量从0.6 kg/s增加到1.2 kg/s的贫熄工况,整体Da数维持在7.9上下波动,平均波动范围在5%左右,证明网格化Damk hler方法能够在不同来流工况下捕捉贫熄特征,为解决实际工程问题奠定了理论基础.

A lean blow-off(LBO)prediction method based on meshed Damk?hler(Da)number is developed in this paper.Reaction zone is defined based on the concentration of OH radical,and it is equally divided into a number of blocks that have identical length scales,thus reducing the effects of non-uniform species and temperature distributions in the reaction zone on the prediction accuracy.Da numbers are calculated for the whole reaction zone and each block therein.Flow time scale and chemical reaction time scale are defined as the residence time of fresh mixed gas in the reaction zone(or a block)and the shortest residence time needed to trigger the reactions,respectively.The calculation results of local Da fields show that drastic combustion occurs near the upper end of the recirculation zone under LBO conditions;however,under the design condition,it occurs at the rear part of the recirculation zone.The calculation results of global Da fields show that when the inlet mass flow rate increases from 0.6 to 1.2 kg/s under LBO conditions,the global Da number will fluctuate around 7.9(i.e.,an average fluctuation range of about 5%),showing that the proposed method can capture the LBO characteristics under different inlet conditions and thereby provide a theoretical basis for solving practical engineering problems.