后甲板对S弯激波矢量喷管流动特性的影响

Influence of Aft Deck on the Flow Characteristics of a Serpentine Shock Vector Control Nozzle

收-扩型S弯激波矢量控制喷管不仅可以显著降低发动机尾部的红外和电磁辐射强度,还可以实现超声速飞机俯仰方向的推力矢量控制,极大地增强了飞机的隐身性和机动性。由于矩形出口需要与后机身融合,通常将下壁面延长作为后甲板,此时喷流的偏转规律与对称出口喷流的偏转规律不同。本文采用数值模拟的方法,比较了有后甲板和无后甲板S弯激波矢量控制喷管的流动特性,分别研究了有后甲板S弯激波矢量控制喷管的长度和角度对其性能的影响。结果表明:在某些工况下,上壁面二次流注入所诱导产生的斜激波会被后甲板反射,不利于向下推力矢量角的产生;当后甲板表面没有发生开式分离时,下壁面出口喷流会沿后甲板表面附壁流动,因此后甲板长度或角度的增加会使喷流速度轴线向下偏转。

A convergent-divergent serpentine shock vector controlling nozzle can significantly reduce the infrared and electromagnetic radiation intensity of the engine tail,and realize the thrust vector control in the pitch direction of supersonic aircraft,which greatly enhances the stealth and maneuverability of the aircraft.As the nozzle with a rectangular outlet needs to be integrated with the rear fuselage,one side wall is usually extended as an aft deck,so that the deflection rule of the tail jet is different from that under the symmetrical nozzle outlet.In this paper,numerical simulation is used to compare the flow characteristics of serpentine shock vector controlling nozzle with and without an aft deck,and then the influences of the aft deck length and angle on the performance of serpentine shock vector controlling nozzle with an aft deck are studied respectively.The results show that under certain working conditions,the oblique shock wave induced by secondary flow injection from the upper wall will be reflected from the aft deck,which is not conducive to the generation of downward thrust vector angle.When there is no open separation of the aft deck surface,the outflow from the lower wall will flow along the aft deck surface,so the increase of the length or angle of the aft deck will deflect the jet velocity axis downward.