基于冷态数值模拟的航空发动机燃烧室贫油熄火预测

Lean Blow-Out Prediction of Aero-Engine Combustor Based on Cold Flow Field Numerical Simulation

关键词:  贫熄边界预测  燃烧负荷参数  冷态流场  数值仿真  燃烧室

Key words:  Prediction of LBO limits  Combustion load parameter  Cold flow  Numerical simulation  Combustion chamber

摘要:

在经典均匀搅拌反应器理论(Perfect Stirred Reactor)的基础上,对Lefebvre贫熄模型中的燃烧体积和燃烧空气量进行改进,建立起燃烧室冷态流场与热态贫熄性能的对应关系,进而达到从冷态流场预测热态贫熄性能的目的。采用商业软件Fluent对燃烧室的冷态速度场和燃料浓度场进行数值模拟,通过燃料的可燃边界定义出理论的可燃区体积(Vf)和进入可燃区的回流空气量(mr)两项关键参数组成燃烧负荷参数Vf·mr,并通过油量迭代逼近(Fuel Iterative Approximation)的方法达到对燃烧室贫熄边界的预测。通过与实验结果的对比表明:燃烧室的冷态流场与其热态贫熄性能是相互关联的,燃烧负荷参数与熄火油气比近似成线性关系；采用油量迭代逼近的方法对燃烧室的贫熄边界进行预测,预测精度控制在±8.4％。

Abstract:

The purpose of this paper is to predict the lean blow-out (LBO) fuel/air ratio based on the numerical simulation of the cold flow field of aero-engine combustors. The paper improves the combustion volume and combustion air contained in Lefebvre’s LBO model, and then correlates the cold flow field to the LBO performance of the combustor through the combustion load parameter (Vf·mr) obtained from the flammable limits. Commercial soft Fluent is used to solve the velocity and concentration field of the combustor. The method of Fuel Iterative Approximation (FIA) is proposed to predict the LBO performance of the combustor. Comparing with the experiment data, it is found that the LBO performance is related to the cold flow field of the combustor and Vf·mr fits linearly with the LBO fuel/air ratio. The LBO prediction accuracy using Fuel Iterative Approximation is within ±8.4％.