Scramjet Isolator Shock Train Location Techniques

Abstract

Within a scramjet, the isolator can contain a shock train in which the static pressure increases from the inlet to the combustor. In order to control the location of the shock train, the shock train leading edge location must be detectable. The purpose of this research is to compare the accuracy of several shock train leading edge detection techniques to measurements made using high-speed shadowgraph photography. A cold-ow, direct-connect high-speed wind tunnel was used to collect all the data, which was then post-processed, for this research. Six methods were considered to locate the shock train leading edge. The rst four use linear interpolation along with pressure transducer measurements and locations. The measurements used include the ratio of static pressures, static pressure increase, static pressure standard deviation, and static pressure power spectral density. Additionally, two static polynomial models were developed which related the sum of the static pressures to the shock train location and the back pressure to the shock train location. The research validates that the spectral content and the pressure rise along the test section can accurately detect shock train leading edge locations. Further, the sum of the pressure transducers method provides a highly accurate leading edge location measurement that is computationally ecient.