Comparison of Intrusive and Non-Intrusive Mixture Composition Measurements in Supersonic Flow

Abstract

Accurately quantifying mixture composition in supersonic flows is vital to the experimental development of fuel–air mixing enhancement strategies for scramjet propulsion applications. Mixture composition can be experimentally quantified by using either intrusive probe-based techniques or nonintrusive laser-based optical diagnostic techniques, with the different methods each offering unique advantages and disadvantages. To this end, the work presented herein provides a comparison of mixture composition measurements made with an intrusive gas-sampling probe to measurements of the same quantity made with the nonintrusive filtered Rayleigh scattering technique. The measurements are made downstream of a strut injector, which sonically injects helium parallel to a Mach 2.5 airflow, creating a two-dimensional planar shear layer composed of a binary mixture of helium and air. The experimental results show that the helium mole fraction measurements obtained using these two different techniques compare quite favorably. Specifically, at the primary downstream station of interest, all of the points surveyed with the gas-sampling probe lie within the 95% uncertainty bands of the filtered Rayleigh scattering measurements, with an average absolute difference in helium mole fraction of between the two techniques.