下腹板长度对单边膨胀喷管性能的影响

在落压比为4~60范围内,对两个不同下腹板长度的单边膨胀喷管模型进行了试验研究,得到了其壁面静压分布,并对4种不同下腹板长度的喷管模型进行了数值模拟研究,获得了总体性能参数.结果表明:在整个落压比范围内,喷管流动都呈现很强的三维特征,而且在高落压比条件下上膨胀面两侧边气流出现了横向分离.喷管轴向推力系数峰值随下腹板长度增大而增加,峰值对应的落压比也逐渐增大并趋近设计点.在落压比为30~80范围内,轴向推力系数随着下腹板长度增大而增加,在设计点轴向推力系数的最大值和最小值相差约1.8%;在特定低落压比条件下,较短下腹板长度的喷管具有高的轴向推力系数.气流矢量角随下腹板长度增加而增大,在设计点最大值和最小值分别为6.03°和-1.83°.

Effect of flap length on the performance of single-expansion-ramp-nozzle

An experimental study of single-expansion-ramp-nozzle (SERN) models has been conducted to investigate how the nozzle flow was affected by the flap length variation at nozzle pressure ratios (NPR) from 4 to 60 under wind off condition.Wall static pressure distributions were obtained.A three-dimensional numerical simulation was also conducted to predict the performance which was unattainable in the test facility of four models with different flap lengths.The results show that the flow exhibits strong three-dimensionality and crossflow separation of the exhaust flow is apparent in the ramp side regions at high NPR.The peak value of the axial thrust coefficient (ATC) increases with the increase of the length of flap;moreover,the corresponding NPR becomes larger and approaches to design NPR.The ATC increases with increasing flap length at NPR between 30 and 80 and the gap between maximum and minimum reaches 1.8% at the design NPR,whereas the model with shorter flap has higher ATC at certain low NPR.The thrust vector angle increases along with the flap length increase,and the maximal and minimal values of the thrust vector reaches 6.03° and -1.83° at the design point respectively.