Abstract
Understanding the physical mechanisms and having insight to the complex flowfield involving unstart phenomena in supersonic inlets has gained considerable attention especially in the area of scramjet inlet/isolator aerothermodynamics. In this study, Schlieren visualization and computational analysis of shock wave structures in ramjet/scramjet inlet/isolator models in supersonic flow have been performed. Experiments were performed in the supersonic wind tunnel at the Trisonic Research Laboratory in Istanbul Technical University. The test section floor and the existing mechanism underneath have been modified to be able to mount the designed inlet/isolator model on the floor of the test section. The inlet/isolator model with a 12- degree compression ramp is investigated at Mach 2 both computationally and experimentally. Computations were performed using Star-CCM+ software to investigate shock wave structures in and around the three dimensional inlet/isolator model as mounted on the test section floor as a guide for designing the experimental model. In the results, the effects of shock wave – boundary layer interactions with flow separations with were observed. Ensemble average of the density distributions on a series of planes from one side wall to the other from the CFD results agreed well with the Schlieren images obtained experimentally. The structure of the shock waves and angles obtained from the Schlieren images agree quite well with those obtained from the CFD results. The effects of lambda-shock formations which indicate possible boundary layer separations, reflections of shock waves, and shock wave – boundary layer interactions on inlet unstart phenomena have been discussed. In order to investigate inlet unstart mechanism further, different experimental setups have been suggested for future work.
Highlights
Developing reliable and affordable ramjet and scramjet propulsion technologies is vital for realizing routine supersonic and hypersonic transport
The structure of the shock waves and angles obtained from the Schlieren images agree quite well with those obtained from the Computational Fluid Dynamics (CFD) results
In order to investigate inlet unstart mechanism further, different experimental setups have been suggested for future work
Summary
Developing reliable and affordable ramjet and scramjet propulsion technologies is vital for realizing routine supersonic and hypersonic transport. Ramjet/Scramjet uses forward motion of the vehicle to compress incoming air at the inlet instead of a rotary compressor in conventional jet engines. Air is slowed down to subsonic speeds by a system of shock waves in the inlet/isolator. Thermal and mechanical loads increase on the combustion chamber walls Because of these performance limitations, ramjet propulsion is not suitable speeds above Mach 5 [1]. Shock waves in the inlet/isolator convert the dynamic pressure due to the velocity of incoming air into higher. This study summarizes some of the efforts made in that direction including shock wave visualization by schlieren method and the computational analysis which are performed to improve the process of designing and manufacturing the experimental model to be used in the wind tunnel
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