Numerical and Experimental Investigation of Entropy Generation in a Supersonic Air Intake at Design Mach number

The flow quality inside a supersonic axisymmetric mixed compression air intake designed for the freestream Mach number of 2.0 has been investigated experimentally and numerically in this study. The numerical study was used to analyze the shock configurations inside the intake. The flow in a supersonic intake is always irreversible due to the shock waves and boundary layers. A useful tool for studing flow quality entering the engine is the investigation of entropy generation due to various factors. In this study, the accuracy of the numerical results is evaluated by the experimental data at first and then the entropy generation inside intake is studied for different back pressures. Results indicated that reduction of the pseudo-shock length results in the significant decrease of entropy generation. Furthermore, role of the pressure fluctuations in the entropy generation was examined and it is observed that pressure fluctuations could have a significant effect on the irreversibility of the flow. According to the results, by increasing the exit blockage ratio from 55% to 62.5%, the rate of entropy generation will be reduced by 33% due to the reduction of peuso-shock length, reduction in the flow separation at the end of diffuser and reduction of pressure fluctuations.