Measurement of Flow Properties and Thrust on Scramjet Nozzle Using Pressure-Sensitive Paint

An experimental study of flows over a single expansion ramp nozzle with flush-mounted side walls was carried out at the DLR, German Aerospace Center. The tests were performed at a freestream Mach number of 7 in the hypersonic wind tunnel H2K in Cologne. The Reynolds number and nozzle pressure ratios in the wind-tunnel flow were varied to study the performance of the scramjet nozzle at different flight altitudes and run conditions. The static pressure distribution on the single expansion ramp was measured by both the pressure-sensitive paint method and by using pressure transducer taps located at discrete points on the surface. These two methods showed that the nozzle pressure ratio and the freestream Reynolds number do not substantially influence the static pressure ratio on the expansion ramp. A pitot rake was also used to measure the pressure distribution in the nozzle wake. Using this technique the nozzle flow in the wake could be visualized and the strong influence of the nozzle pressure ratio on the interaction between nozzle and external flows was revealed. The data obtained by the different measurement techniques permitted a characterization of the nozzle flow and gave insight into the properties of single expansion ramp nozzle flows. The thrust generated by the nozzle, the thrust efficiency coefficient, and the thrust vector angle were calculated by using the pressure data obtained by both pressure measurement techniques and the results compared. It was shown that thrust values obtained from pressure tap measurements were overestimated. Criteria were developed to aid in the design and optimization of the thrust-related performance criteria for this single ramp nozzle.

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