两级入轨 (Two Stage To Orbit, TSTO) 飞行器在高超声速来流条件下级间分离, 会在两级之间产生复杂的非定常气动干扰, 直接增加 TSTO 级间分离失败风险. 级间分离过程中的这种复杂气动干扰伴随着两级之间的激波与边界层干扰、马蹄涡、激波与尾流干扰的综合作用。本研究将 TSTO 助推级和轨道级的复杂模型简化为两个三维楔, 采用重叠动网格技术, 耦合求解流动控制方程及六自由度刚体动力学方程组对级间分离过程开展模拟分析, 探究级间分离流动特性及其物理机制. 在数值分析过程中, 针对不同抬升角度下的 TSTO 三维流场进行了CFD(computational fluid dynamics) 静态和动态数值模拟, 给出了不同抬升角度下的干扰流场流动规律和特性, 结合流场结构和壁面压力分布以及分离流动模式阐明了两级之间这种气动干扰对 TSTO 气动分离的影响机制, 并探讨了轨道级抬升角对 TSTO 安全分离的影响. 结果表明两级间的气动干扰强度随着轨道级抬升角的增大而增强, 并且在动态分离过程中随着两级间隙的增加而减弱; 在轨道级释放前两级间气动干扰和三维分离拓扑结构随着抬升角的增大变得更加复杂, 流动分离区域增大, 临界点数量增加; 在级间分离过程中, 两级气动特性变化幅度随着轨道级抬升角增大而增大, 分离时间则随之减小. 另外, 当轨道级抬升角度在 6 ~ 8°时可实现该 TSTO 更加安全可靠的分离.

Stage separation of two-stage-to-orbit (TSTO) vehicle under hypersonic inflow conditions will produce complex unsteady aerodynamic interference between the two stages, which directly increases the risk of TSTO separation. This complex aerodynamic interference is accompanied by the combined action of shock wave and boundary layer interaction, horseshoe vortex, shock wave, and wake interference between the two stages. In the current study, the complex models of the TSTO booster and orbiter are simplified into two three-dimensional (3-D) wedges. Based on the overset dynamic grid technology, the Navier-Stokes equations coupled with six-degree-of-freedom rigid body dynamic equations are solved to simulate and analyze the stage separation process, to explore the flow characteristics and physical mechanism of stage separation. In the numerical analysis, static and dynamic numerical simulations were carried out for the three-dimensional flowfield of TSTO under different orbiter's lifting angles (β), and the flow patterns and interference characteristics with varying β were analyzed and discussed in detail. Combined with the flowfield structure and wall pressure distribution, as well as separated flow, the mechanism of the aerodynamic interference between the two stages during the TSTO separation, were clarified, and the effects of the lifting angle condition of the orbiter on the safe separation for the current TSTO model was discussed. The numerical results show that the interstage aerodynamic interference increases with the increase of the lifting angle of the orbiter, and decreases with the increase of the interstage clearance during stage separation. Before the release of the orbiter, the interstage aerodynamic interference and 3-D separated flow topology become more complex with the increase of β, and separation area increases, as well as the number of critical points. In the process of stage separation, the variation amplitude of the aerodynamic characteristics of both stages increases with the increase of β, and the separation time decreases. Moreover, the lifting angle of the orbiter is 6 ~ 8° would be conducive to the safe stage separation for the current TSTO model.