Masahiro TAKAHASHI, Tatsushi ISONO, Koichiro TANI, Sadatake TOMIOKA

DOI Number: N/A

Conference number: HiSST-2025-229

In developing a turbine-based combined cycle engine for a hypersonic cruise transport aircraft, the technical challenge is to extend the operating range of the scramjet engine (SCRJ) to low speeds (expected to be between Mach 3 and 4), enabling switching with the turbo-ramjet engine (TRJ). This study aimed to develop a design method for scramjet inlets that can maintain a suitable flow field for startup conditions down to the low-speed transition point with the TRJ while achieving high inlet performance during high-speed cruising. This involved optimizing the pressure ratio distribution of a two-dimensional, multi-stage ramp mixed-compression inlet, as well as a CFD-based startability evaluation. Optimizing the pressure ratio distribution using the inlet’s total pressure recovery (which accounts for viscous losses) as the objective function resulted in a nearly uniform distribution, similar to the inviscid flow case. This occurs because the total pressure loss due to oblique shock waves is dominant while the contribution of viscous losses is small. Next, an inlet designed for an overall pressure ratio of 30 under cruise conditions, assuming a flight Mach number of 6, failed to obtain a start-state flow field under switching conditions from the TRJ, assuming a Mach number of 3.5. Reducing the internal compression ratio while maintaining the same overall pressure ratio allowed the inlet to achieve
a start-state flow field. However, reducing the internal compression ratio caused the inlet flow-path to tilt downward, which significantly increased drag, particularly on the outer surface of the cowl.

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In Categories: 1.Events, 1.HiSST 2025, Propulsion Systems & Components
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