风兜面积对气冷喷油杆性能影响的数值研究

以某型涡扇发动机加力燃烧室气冷喷油杆为研究对象,在梯形截面的风兜下底和高度不变的情况下,通过改变上底长度得到一系列不同风兜面积的几何模型,综合考虑外流场对气冷喷油杆内部流动和换热特性的影响,对其在巡航状态下进行了流/热/固耦合三维数值模拟研究,获得了不同风兜面积对气冷喷油杆引气率、冷却空气喷口流量分布、壁面平均冷却效果、壁面最高温度的影响规律.结果表明:引气率随风兜面积增大线性增大;喷油嘴凸台周围冷却空气喷口的流量沿气冷喷油杆内冷却空气流向呈二次曲线规律变化,且随风兜面积增大分布趋于均匀;随风兜面积增大,喷油杆、隔热套壁面平均冷却效果线性增大,壁面最高温度降低;有效抑制内涵高温燃气倒灌进入隔热套是避免喷油杆局部高温的关键. 

Numerical analysis on effect of cooling air pocket area on performance of air-cooled fuel injector

Based on an air-cooled fuel injector in an afterburner of turbofan engine,geometric models cooling air pocket areas with different were obtained by changing the the upper bottom length of trapezoidal section cooling air pocket,but with the constant down bottom and height.Considering the effect of the external flow field on the internal flow and heat transfer characteristics of air-cooled fuel injector comprehensively, its conjugate heat transfer three-dimensional numerical simulation was conducted on the cruise flying state, so as to get an effect laws of different cooling air pocket areas on the entraining rate of air-cooled fuel injector,the mass flow rate of cooling air nozzle, the average cooling effectiveness and the maximum wall temperature. Results shows that, the entraining rate increases linearly with the increasing of cooling air pocket area; the mass flow rate of cooling air nozzle around the fuel nozzle convex platform changes by conic rule along the air-cooled fuel injector axis, firstly increases and then decreases; the mass flow rate tends to be uniform with increasing of cooling air pocket area; the fuel injector's and insulated jacket's average cooling effectiveness increases linearly and the maximum wall temperature decreases with the increasing of cooling air pocket area; inhibiting effectively the backflow of the hot gas into the insulated jacket is the key to avoid a partial high wall temperature.