Experimental Evaluation of Isolated Intake for Hypersonic Air- Breathing Vehicle

Abstract

Isolated intake of an air-breathing conceptual hypersonic demonstrator vehicle has been experimentally characterized simulating the entry Mach number and the entry flow direction. A 1:8 scale intake model having provision to vary the entry area of the internal compression portion by means of actuating the intake cowl has been tested in the supersonic freestream Mach numbers 3, 3.44 and 3.9. Tests were carried out in the 0.3 m x 0.3 m trisonic wind tunnel at National Aerospace Laboratories, Bangalore. The result pertaining to M¥ = 3.44 is discussed in this paper. The effect of cowl position on the intake starting characteristics and performance are analyzed using wall pressure measurements, schlieren and oil flow visualization. Intake unstart occurred before the cowl reaching to its fully open position with the original hinge location. Essentially the strength of cowl leading edge shock increases as the cowl opening angle increases. The strong shock-boundary layer interaction in the convergent portion of intake aids the growth of the separation bubble in the flow path and that cause the intake to unstart. Improvement of intake starting by means of shifting the cowl hinge location downstream was attempted. Shifting the cowl hinge location downstream has improved the intake starting characteristics. On the improved configuration, the effect of combustion induced back pressure and the effect of cowl opening speed on intake unstart have been analyzed and quantified.