波瓣尾缘切角对涡扇发动机混合排气系统气动热力性能影响

Effects of Cut Angles at Trailing Edge of Lobe on Aerothermodynamic Performance of Forced Mixing Exhaust System in Turbofan Engine

关键词:  涡扇发动机  波瓣  尾缘切角  混合排气系统  热混合效率  总压恢复系数  推力系数 

Key words:  Turbofan engine  Lobe  Cut angle at trailing edge  Mixer exhaust system  Thermal mixing efficiency  Total-pressure recovery coefficient  Thrust coefficient

摘要:

为了获得尾缘切角对涡扇发动机波瓣强迫混合排气系统的流场、热混合效率、总压恢复系数以及推力系数的影响,以涡扇发动机波瓣强迫混合排气系统为研究对象,采用基于Navier-Stokes方程的三维数值模拟方法对不同波瓣尾缘切角模型进行了计算并得到了气动热力性能的影响规律。结果表明:较大的尾缘切角造成在尾缘截面前主次流更早的提前混合,使流向涡的产生和发展在位置上向上游提前,以至于在尾缘截面之后的一定范围内混合效率更高。但大尾缘切角同时也造成较大的能量损失,以至于总压恢复系数较小,总的混合效率偏低:相比0°切角,25°切角的总压恢复系数减小了0.34%,热混合效率减小了11%。适当的尾缘切角修形可以增大推力系数。 

Abstract:

To obtain the effects of cut angles at trailing edge of lobed mixer in turbofan engine on flow field, thermal efficiency, total-pressure recovery coefficient and thrust coefficient, a series of 3D numerical simulation based on Navier-Stokes equations were conducted based on a lobed mixer in the forced mixing exhaust system of a turbofan engine and the principle of effects on aerothermodynamic performance was obtained. Larger cut angle causes earlier mix of primary and secondary flow and earlier development of streamwise vortices in the direction of flow, so that mixing efficiency is higher within a certain distance after trailing edge. But it also causes more energy loss, so that total-pressure recovery coefficient and overall mixing efficiency are low. Total pressure recovery coefficient is decreased by 0.34% and mixing efficiency is decreased by 11% when cut angle is increased from 0° to 25°. Thrust coefficient could be increased with an appropriate cut angle at trailing edge. 