1 design of the inlet compression system decides

1              
Introduction

The future of the high speed flight will be depends on the
development of air breathing propulsion system without rotating components. The
major advantage of air breathing propulsion system is the ability to generate
high specific impulse compare to rockets. The design of the inlet compression
system decides the performance of the hypersonic space propulsion system and
the optimized inlet able increase the payload capacity of the whole system. The
scramjet engine employs dual mode compression system to achieve the effective
pressure recovery 1. The problems associated with the supersonic compression
using oblique shock wave are the shock wave boundary layer interaction and
shockwave reflection 2-3. The oblique shock generated by the ramp interacts
with the turbulent boundary layer on the cowl surface and produces subsonic
separation bobble, further the unsteady subsonic bubble is grow at faster and faster
and reduce the mass flow rate in the outlet 4.the number of studies were conducted
experimentally as well as computational fluid dynamics 5-8 to control the shockwave
boundary layer interaction and controlling the subsonic bubble formation in the
inlet. The characteristics of a single ramp inlet both steady and unsteady conditions
are studied in this paper.   

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2               
Inlet Model and computational method

2.1 Inlet model

 

The 2D inlet model used for the
computational study as shown in figure with 36.9 degree ramp angle to generate
the shock at the Mach number of 5.96the produce shock wave had a wave angle of 51.24
degrees, the distance between the ramp and the cowl is maintained as 115 mm.

 

2.2 computational method

The flow field properties are
calculated by solving Navier–Stokes equations. An implicit scheme with second-order
accuracy used for both steady and unsteady flow field computation. The flow
field is treated as ideal gas and for turbulence modeling the shear-stress
transport (SST) Reynolds averaged Navier–Stokes (RANS) model is used. To capture
the boundary layer behavior the y plus maintained below 1.the inlet are assumed
to be pressure far-field and outlet of the computational model as pressure
outlet. The computational model solved for continuity, momentum and energy and
the corresponding residuals are monitored up to the convergence criterion for
these residuals to drop below 103.