Wind Tunnel Verification of a Translating Cowl-Lip Method for Axisymmetric Inlet Starting

Whether the inlet can start successfully is a prerequisite for the propulsion system to provide normal power to an aircraft. To address the starting difficulty of a high-contraction-ratio TBCC inlet lacking self-starting capability, this study proposes a forced-starting strategy via cowl-lip axial translation and validates its feasibility through wind tunnel tests. This research focuses on an axisymmetric mixed-compression inlet designed for a cruise Mach number of 4.0, operating across a Mach number range of 0–4. To overcome the starting challenges induced by a high internal contraction ratio, cowl-lip translation was employed as the primary geometric adjustment mechanism, enabling the inlet to start at a lower contraction ratio before transitioning to its high-performance design configuration. Experiments were conducted in the FL-23 wind tunnel at inflow conditions of Mach 3.5 and Mach 4.0, comparing the inlet’s starting characteristics with and without the cowl-lip adjustment. The experimental results indicate that without active regulation, the inlet failed to self-start under both test conditions. However, with the implementation of the cowl-lip translation strategy, the inlet successfully achieved a started flow field. Furthermore, the inlet maintained a stable started state even after the cowl was translated back to its high-contraction-ratio design position. This study validates the effectiveness of using cowl-lip geometric translation as a forced-starting method for inlets. In summary, this approach resolves the starting issues of high-contraction-ratio inlets at critical Mach numbers and provides a valuable technical reference for variable-geometry inlets aiming to achieve both high performance and reliable starting across a wide Mach number range.