高空来流条件下航空发动机双旋流燃烧室点火特性数值模拟

Numerical Simulation of Ignition Characteristics of Aeroengine Combustor with Two-Stage Swirler under High-Altitude Inflow Conditions

关键词:  航空发动机  燃烧室  极端条件  点火  数值模拟

Key words:  Aeroengine  Combustor  Extreme condition  Ignition  Numerical simulation

摘要:

为深入了解真实航空发动机燃烧室极端条件下点火性能，在自有CFD平台上对不同高空来流条件下典型航空发动机双旋流燃烧室点火过程进行了数值模拟。为保证模拟精度，对模型包括全部气膜冷却小孔在内的所有精细结构均进行了完全仿真，并完整再现了燃烧室内从燃油雾化到点火燃烧全过程。结果表明3种高空来流条件下单次点火均失败。点火过程显示高温燃气越过旋流杯中心向上回流区扩张是点火的关键时空区域，在此时补充点火可推动火焰顺利传播到整个主燃区。对8km和6km两种状态分别增加点火次数到3次和5次后最终点火成功，结果表明前者着火极限油气比约为0.057，后者为0.038~0.042。

Abstract:

To gain an improved understanding of the ignition property in practical aeroengine combustor under extreme conditions， numerical simulation of ignition process in a typical aeroengine combustor with two-stage swirler was carried out on our own CFD platform under different high-altitude inflow conditions. The complex geometric configuration including all film cooling holes was fully simulated without any conventional simplification in order to ensure the modeling accuracy， and the unsteady process from fuel atomization to ignition and combustion was totally reproduced.Simulation results show ignition failure when igniting only once. Ignition process reveals the crucial moment that hot gas is spreading over the center of the swirler cup， at which time the supplementary ignition can promote the flame and make it successfully propagate to the whole primary zone. For the two cases of 8km and 6km， it finally catches fire when increasing the ignition to 3 and 5 times respectively， with corresponding limitation of fuel-air-ratio about 0.057 and 0.038~0.042.