异形进气道可以提高飞行器的隐身能力，但由于其型面与机翼高度融合且三维弯曲，存在复杂的流动结构，在小流量状态下极可能发生流动失稳从而影响发动机的正常工作。针对异形进气道开展了仿真计算，获得了进气道的流动特性和性能规律，揭示了小流量状态下进气道失稳机理。结果表明：在大流量状态下，出口马赫数升高引发的摩擦损失占主导，造成总压恢复系数下降；而在小流量状态下，进口回流区和喉道强逆压力梯度引发入口的边界层分离，伴随二次流与主流之间的掺混效应，内道截面内多涡结构逐步融合为整涡结构，显著加剧了总压损失程度，对发动机匹配构成挑战。此外，攻角变化对进气道稳定边界有显著影响，正攻角状态下，进口一弯下壁面及鼓包后的上壁面更易发生分离，导致失稳流量点提前，进气道性能对流量扰动更为敏感。本研究明确了进气道小流量失稳的核心物理机制，并为复杂工况下进气系统的稳态设计与稳定性提供了理论支撑。

Irregular inlets can enhance the stealth capability of aircraft, but their complex flow structures may lead to instability under low flow rate conditions, thus affecting the normal operation of the engine. Numerical simulations are conducted to investigate the flow characteristics and performance behavior of an irregular inlet, with particular focus on its instability mechanism under throttled (low-mass) conditions. The results show that under high-mass conditions, the increased exit Mach number leads to dominant frictional losses, resulting in a decrease in total pressure recovery. In contrast, the boundary layer separation at the inlet, caused by the recirculation zone and strong adverse pressure gradients in the throat, is accompanied by the mixing effects between secondary flows and the main flow. The multiple vortex structures within the internal duct cross-section gradually merge into a single vortex structure, significantly increasing the total pressure loss and posing challenges for engine matching. Furthermore, the angle of attack has a pronounced impact on the inlet’s stability boundary. At high positive angles of attack, separation is more likely to occur on the lower wall of the first bend and the upper wall downstream of the bulge, leading to an earlier onset of flow instability and increased sensitivity of inlet performance to flow disturbances. This study clarifies the core physical mechanisms responsible for low-flow instability in shaped inlets and provides theoretical guidance for robust inlet design and stability management under complex operating conditions.