基于CFD分析改进三旋流燃烧室头部设计

Dome structure modification of a high temperature rise combustor based on CFD simulation

关键词:  航空发动机  燃烧室  贫油熄火  冒烟  数值仿真

Key words:  Aero engine  Combustor  Lean blow out  Smoke  Numerical simulation

摘要:

利用FLUENT,对一多级旋流燃烧室的冷态单相流场进行了数值模拟,基于该流场结果,对该燃烧室头部控制油雾混合的三级涡流器唇口处进行了改进设计。并对两种方案的燃烧室在相同试验条件下进行了贫油熄火油气比、大功率工作时的冒烟指数进行了实验研究。对方案1燃烧室单相冷态流场的结果表明,该燃烧室内部流场和预想的流动组织有较大差别,三级旋流器出口的气流,迅速向径向流去,主燃区的回流区结构不明显,且二级旋流出口和三级旋流出口之间有小回流区。该流场结构解释了方案1燃烧室有很好的贫油熄火性能,但是冒烟指数较高。方案2燃烧室的流场结构,改变了三级旋流出口气流方向,消除了与二级旋流器之间的小回流区。方案2燃烧室在与方案1燃烧室相同试验条件下的实验结果表明,贫油熄火油气比性能下降了7.3%,但发动机大功率时冒烟排放指数改善了29.4%。基于数值分析的燃烧室设计,使燃烧室扩大稳定工作范围的研究取得了进展。

Abstract:

FLUENT was used to numerically simulate the cold,single phase flow field of a combustor featured with multi-swirler.Based on the numerical results of the origin structure of this combustor,modification was made at the lip of the outer swirler which controls the mixture of oil and air.The Lean-Blow-out(LBO)and smoke features of both the scheme 1 and the scheme 2 combustor were tested on the same rig under same condition.The flow field of the scheme 1 shows that there are huge difference between the numerical result and the expected flow field inside the combustor,especially in the regions near the dome.The air flows radically at the outlet of outer swirler.The recirculation zone in the dome is not obvious,and there is a small recirculation between the outlet of the middle swirler and outer swirler.This flow field structures explain the experiment results of this scheme 1 combustor which has good Lean-Blow-out limit,but poor smoke feature.As for the scheme 2 combustor,the numerical results show that the flow direction near the outlet of the third swirlers changes and there is no longer recirculation zone between the two swirlers.Results of experiment on the two combustors about Lean-Blow-out and smoke features showed that the smoke number was greatly reduced(decreased by 29.4%),with Lean-Blow-Out decrease by 7.3%.