贫油直喷燃烧室回火的数值研究

Numerical investigation of flame flashback in LDI combustor

针对燃烧稳定性中的回火问题,对贫油直喷燃烧室的回火特性进行了研究。燃烧中的回火指的是火焰从燃烧室传入到了预混区中的这样一种现象,它包含了声波、湍流、燃烧之间的复杂的相互作用,是燃烧研究中的关键问题之一。利用Fluent中的混合分数/PDF平衡化学反应模型对贫油直喷燃烧室进行了大涡模拟,分别计算了冷态和热态下的流场,捕捉了贫油直喷燃烧室内回火的动态过程,其中亚格子模型采用WALE模型,燃油射流采用离散相模型。研究结果表明,大涡模拟能够较好地反映流场分布情况,贫油直喷燃烧室内存在中心回流区,模拟结果与实验结果吻合较好;贫油直喷燃烧室中的回火发生在中心流区域,回火时,中心回流区向上游移动,这促使了火焰的向上游传播,并最终导致了回火的发生。

Aiming at the problem of flashback in combustion stability,a large eddy simulation was used to investigate the flashback characteristic of lean direct injection combustor.The flashback here was refered to a phenomenon that the flame propagates from the combustor into the premixed zone,which contains complex interaction among the sound waves,turbulence and reactions.It is one of the key issues in the combustion research.The mixture fraction/PDF equilibrium chemistry model and discrete phase model with software Fluent were adopted to simulate the cold flow and hot flow,and the flashback was observed.WALE model was used as the sub-grid model.The results indicate that large eddy simulation can predict the flow field well,there exists a centeral recirculation zone in the LDI combustor,numerical results are in good agreement with experimental data,flame flashback in LDI combustor occurs around the centerline and during flashback,the central recirculation zone moves upstream,which pulls the flame upstream propagation,and finally leads to flashback.