Relocation of the Double-Bump on the Ramp of a Supersonic Air-intake for its Improved Performance

Abstract

The performance of a supersonic air-intake is important for efficient combustion in an air-breathing engine. Recent literature shows study of the design of a supersonic air-intake, with bumps located on its ramp surface. The bumps generate oblique shocks which should result in pressure jump downstream of the shocks. This would result in compressed and decelerated flow at the exit of the intake, for efficient combustion downstream. However, some recent studies found that a double-bump degrades the performance of the air-intake compared to a single bump. This sounds counter-intuitive. In this work, this problem is investigated and an improved location for the double-bump is proposed based on physics of high-speed gas dynamics. Computational analysis is then done to analyze the performance of the supersonic air-intake with an incoming freestream flow of Mach 2.2, using CFD package ANSYS Fluent. The computational methodology is first validated using results of surface pressure distribution on the wall of the intake, for a standard test case available in literature. The methodology is then applied for the supersonic air-intake with the proposed location of the double-bump. The resulting Mach contours and pressure contours are discussed in relation to the compression and Mach number obtained at the exit of the intake. The results show that with the location proposed in this work, the double-bump results in a system of shocks and reflected shocks which are contained well within the air-intake. This results in higher pressure recovery and lower Mach number at the exit of the intake, compared to a single-bump intake. As the air with higher static pressure and lower speed enters the combustion chamber downstream, both these favourable features should help in more efficient combustion.