航空发动机两级反向旋流燃烧室燃烧流场大涡模拟研究

LESof Combustion Flow Fieldina Practical Aeroengine Combustorwith Two-Stage Counter-Rotating Swirler

关键词:  航空发动机燃烧室  反向双旋流  大涡模拟  动态亚网格模型  快速化学反应模型  火焰面模型  反应进度变量模型

Key words:  Aeroengine combustor  Counter-rotating swirler  Large eddy simulation  Dynamic Smago. rinsky model  Fast chemistry model  Flamelet model  Progress variable model

摘要:

为深入了解真实航空发动机内燃烧流场，采用动态亚网格模型结合单步快速化学反应(FC)、火焰面( FLM)及反应进度变量( FPV)等三种燃烧模型对径向两级反向旋流燃烧室单头部构型进行了大涡模拟。为避免模型简化误差，对燃烧室包括全部气膜冷却孔在内的精细结构进行了完全仿真。在已达到统计定常状态的冷态流场基础上首先模拟了燃料喷注和掺混过程，约2.6ms后燃料到达真实的点火位置，随后采用FPV模型在半径3mm的球形区域数值模拟了点火，展示了在主燃孔横向射流作用下初始火焰沿化学恰当比混合分数等值线传播并充满整个火焰筒的发展过程，结果显示火焰到达燃烧室出口的耗时约为6～7ms。不同模型算法预测的平均温度场与CARS测量结果作了对比，LES-FPV，RANS-FPV，LES-FLM 以及参考文献中RANS-FLM 计算平均误差分别为3.47%，4.17%，7.76% 和11.22%，表明LES改进了模拟精度，且FPV模型显著优于FLM模型。RANS-FPV预测的出口存在严重热斑，导致其给出的出口温度分布因子(OTDF) 及最大径向温度分布因子(RTDF) 值分别达到0.593和0.313；LES-FPV结果均匀性最好，其预测值分别为0.284和0.193。

Abstract:

To improve knowledge of the reacting flow in real aeroengines，large eddy simulation(LES) with dynamic Smagorinsky subgrid model is used to explore the complex unsteady flowfield in a single burner of atypical aeroengine combustor with radial two-stage counter-rotating swirler. Three combustion models namelyfast chemistry model(FC)，flamelet model(FLM)and progress-variable model(FPV)are applied. The com.plex geometric configuration including all film cooling holes is fully simulated without any conventional simplifica.tion in order to essentially reduce the modeling errors. Based on the non-reacting flowfield which has been ad.vanced to the statistically stationary state in early work，unsteady process of fuel injection is first simulated with.out reaction. It cost about 2.6ms for adequate fuel reaching the real ignition location，then pseudo ignition is nu.merically conducted using FPV model in the given sphere region with a radius of 3mm. The process that initialflame propagates along the isoline of stoichiometric mixture and fills the whole chamber under the effect of trans.verse flow is simulated. It costs about 6～7ms for the flame arriving at the outlet. Compared to coherent anti-Stokes Raman scattering(CARS)measurement of mean temperature on central profile，mean error of LES-FPV， RANS-FPV，LES-FLM and RANS-FLM in the reference are 3.47%，4.17%，7.76% and 11.22% respectively， indicating that LES improves the accuracy and FPV performs better than FLM. Due to the severe hot spot at theoutlet，RANS-FPV gives the poorest outlet temperature distribution factor(OTDF)and maximum radial tempera. ture distribution factor(RTDF)as 0.593 and 0.313 respectively. Corresponding values predicted by LES-FPV are 0.284 and 0.193，presenting the best uniformity among all cases.