单边膨胀喷管几何参数对内特性和流场的影响

Effects of Geometric Parameters on Internal Performance and Flowfield of Single Expansion Ramp Nozzles

关键词:  单边膨胀喷管  几何参数  内特性  数值模拟

Key words:  Single expansion ramp nozzle  Geometric parameters  Internal performance  Numerical simulation

摘要:

采用三维数值模拟方法研究了单边膨胀喷管(SERN)主要几何参数对其内特性和流场的影响,计算结果表明:侧壁的延伸对SERN的轴向推力系数Cfa是有益的,但过大的侧壁浸湿面积会产生大的摩擦损失从而使推力性能下降；其中部分封闭侧壁的性能要略微高于全封闭式侧壁,而相比于短侧壁,其Cfa的优势在2%左右；此外,侧壁的延伸可以有效降低设计点的推力矢量角δp；长的曲壁模型拥有高Cfa的同时其δp处于较低的水平,在设计点条件下,最高Cfa可达0.983,这与传统的轴对称喷管和二元收扩喷管相差不大；在高落压比条件下,大的喷管喉道宽高比可以有效降低气流展向膨胀损失从而具有高的Cfa和低的δp,而且其优势随NPR的增大而增加。 

Abstract:

D Navier-Stokes calculations were carried out to investigate the effects of geometric parameters on internal performance and flowfield of single expansion ramp nozzles (SERNs). The results show that, in general, the nozzle sidewall extension has a beneficial effect on nozzle thrust. However, excessive large wetted surface area of sidewall results in great friction loss, which is already prevailing over the pressure gain by sidewall extension. The partial sidewalls perform slightly better than full sidewalls, and the axial thrust ratio C_fa is 2% larger than short sidewalls. Moreover, the extended sidewall reduces the pitch thrust vector angle δ_p effectively at the design point. The long curved ramp obtains higher C_fa and smaller δ_p than the short curved ramp, and the C_fa reaches 0.983 at design point, which is comparable with the conventional axisymmetric and two-dimensional convergent-divergent (2DCD) nozzles. Under the conditions of relatively high nozzle pressure ratios (NPRs), large throat aspect ratio reduces the spanwise expansion losses effectively,with higher C_fa and smaller δ_p, and the margin increases with increasing NPR.