平面膨胀偏流喷管流场特性和推力性能研究

Numerical study on flow and thrust characteristics of a planar expansion-deflection nozzle

采用数值模拟方法研究了平面膨胀偏流喷管在压力比10~150之间的流场特性和推力性能,并与同扩张比传统收敛-发散喷管进行比较。随着压力比不断增大,ED喷管内超声速流动区域面积增大,剪切层向轴线靠近,产生再附着激波,粘性再循环区逐渐与外界大气隔离,流动模式由“开尾流”转变为“闭尾流”。2种流动模式发生转换的标志是基底压力发生突降。所设计的ED喷管在所有计算条件下性能均优于CD喷管,在较低压力比下性能优势更为明显。ED喷管性能提升的原因主要有2点:①不发生壁面流动分离,减少了过膨胀损失;②在压力比较低的条件下,从中心体发出的第一道激波到达喷管壁面时,大量流动发生压缩转向,导致内壁面压力升高,进而导致性能提升。

Compared the flow field characteristics and thrust performance of an expansion deflection nozzle(ED)with a conventional convergent-divergent nozzle(CD)with the same expansion ratio at a pressure ratio between 10 and 150 by numerical simulation,with the increasing pressure ratio,the supersonic flow area in the ED nozzle increases,the shear layer is close to the axis,and the reattached shock wave is generated.The viscous recirculation area is gradually isolated from the outside atmosphere,and the flow mode changes from‘open wake’to‘closed wake’.The transition between the two flow modes is marked by a sudden drop in basement pressure.The performance of the designed ED nozzle is better than that of the CD nozzle under all calculation conditions,and the performance advantage is more obvious at lower pressure ratio.There are two main reasons for the improvement of ED nozzle performance:1)no wall flow separation occurs,reducing the over-expansion loss;2)Under the condition of relatively low pressure,when the first shock wave from the pintle reaches nozzle shroud,a large amount of flow encounter compressive turning,resulting in increased wall pressure,which leads to improved performance.