Numerical Investigations on Development of Scramjet Propulsion System

P, Nithish Reddy (2013) Numerical Investigations on Development of Scramjet Propulsion System. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

In the present study various investigations are done on different components of scramjet propulsion system. In first part numerical investigations are carried out on transverse injection of fuel into the supersonic stream. Investigations includes the study of formation of recirculation regions , shock waves and wall pressure at different injection angles, free stream conditions and injection pressure ratio. Various turbulence models have been tested and the obtained results are well validated with the experimental. Formation of various structures due to sonic jet and supersonic stream interactions are analyzed. With increase in flow Mach number the size of auto ignition regions got minimized and jet injection angle shown the significant effect on the shock structure and peak pressure rise. Degree of boundary layer separation has increased with increase in pressure ratio. In the later part, investigations are done on DLR scramjet combustor where the fuel is injected parallel to the free stream using strut. Numerical investigation on flow phenomena in a scramjet combustor has been performed for different geometric and operating parameters. The present investigations aim to find the optimal geometric parameters and better fuel injection system which has maximum combustion efficiency. A combination of Eddy Dissipation (ED) and Finite Rate Chemistry (FRC) models are used to model the combustion. The effects of divergence angle on the performance of scramjet combustor are reported here. The effects of scaling on DLR combustor performance are reported. The effects of shocks created by strut and inlet conditions of scramjet combustor on combustion efficiency have been reported. A multiple struts combustor has been developed to improve the performance of combustor. Present results show that divergence angle and inlet conditions of combustor are significant on performance of scramjet combustor. Multiple struts combustor has shown higher efficiency than single strut combustor. In the final part the exit conditions of combustor used to evaluate the performance of scramjet nozzle. Numerical simulation of Single expansion ramp nozzle is carried out to investigate the effect of different geometric and operating conditions on performance parameters. Domain of investigation is chosen in such a way to capture the interaction between nozzle exit and hypersonic external flow. While evaluating the Thrust force both the internal and external surface of the ramp is taken in to consideration at various operating conditions. Based on this study, an optimum ramp angle at which the SERN generates maximum axial thrust is obtained for various operating conditions and behavior of the thrust and lift profile with various geometric changes at various operating conditions are predicted. Optimum angle for maximum thrust has shifted to left when simulated at higher operating conditions. Lower cowl angle, larger cowl and ramp length gave increased thrust and rate of increase varied from one operating condition to another.

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