过膨胀单边膨胀喷管试验和数值模拟

Experimental and computational investigation of a over-expanded single-expansion-ramp-nozzle

关键词:  单边膨胀喷管  过膨胀  壁面静压分布

Key words:  Single-expansion-ramp-nozzle  Over-expand  Wall static pressure distribution

摘要:

在低落压比4~10下,对高速二维单边膨胀喷管模型试验件的壁面静压分布进行了试验研究,模拟气体为高压空气;用三维数值计算得到了喷管性能参数,丰富了流场信息。试验和数值模拟结果表明,处于深度过膨胀状态下的单边膨胀喷管内部出现了自由激波、分离激波、两种激波相交及相互影响、自由激波分离和激波诱导分离等复杂现象;上膨胀面大面积的气流分离而形成的低压区使喷管轴向推力系数Cfa仅为0.78~0.87;此外,推力矢量角pδ为18°~25°,这对飞行器的配平和控制面操作带来一定的困难。

Abstract:

An experimental study was conducted at low nozzle pressure ratios(NPRs) between 4～10 to determine the wall static pressure distributions of a high-speed 2-D single-expansion-ramp-nozzle(SERN) under wind-off condition.The jet exhaust was simulated with high-pressure air.A computational investigation was conducted to determine the performance of the nozzle and enrich the information of flowfield.The results indicate that under the highly overexpanded conditions,the inner plume shock wave,the boundary layer separation shock wave,free shock separation(FSS),shock-induced separation(SIS),the cross and the interaction of two aforementioned shock waves could be identified and discerned clearly.The axial thrust coefficient Cfa is as low as 0.78～0.87 due to low pressures acting on the expansion ramp surface.In addition,the thrust vector angle δp is up to 18°～25°,which must be overcome by shifting the vehicle center-of-gravity or by using the vehicle control surface.