Aerodynamic performances of a combined cycle inlet

Ramp-compression-type inlets for the combined cycle engine were investigated in a Mach 4 wind tunnel. Geometries of the inlet models were changed to investigate their effects on the aerodynamic performances and the starting characteristics. A bent cowl improved the starting characteristic by weakening the shock from the cowl leading edge to suppress the shock-induced separation and by reducing the internal contraction ratio of the cowl duct, thus, avoiding choking at the inlet throat. With the current geometries, the inlet started with a slightly larger internal contraction ratio than that restricted by the Kantrowitz-Donaldson limit. The ratio of the height of the cowl duct of the inlet to the incoming boundary layer was found to affect the starting characteristic. The model with a higher capture ratio showed better total pressure recovery performance.