Pressure Characteristics of a Diffuser in a Ram RDE Propulsive Device
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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This report focuses on dynamic simulations of a representative ram RDE subsonic diffuser to study ram RDE compatibility with a supersonic inlet. Of particular interest is the propagation of pressure perturbations due to the detonation waves in the RDE combustion chamber. Simulations were completed using a notional diffuser for a ram RDE device operating at 42,000 ft and Mach 2.5. A previous RDE code was used to provide an exhaust forcing function assuming a slot injector plate. A total of 8 different exhaust forcing functions were used, representing RDE air-valvearea ratios between 0.3 and 0.6 in single and dual shock operation. Simulations were then completed for the diffuser with the Propel code for each of these exhaust forcing functions. Analysis indicates that the amount of pressure variation seen near the inlet is very sensitive to the shape of the forcing function. The broad pressure rise of the lower area ratios tend to remain intact through the diffuser to the intake with minimal dissipation, while the sharper pressure peak of the higher area ratios tend to be dissipated to a larger degree. For single-shock operation, the amount of pressure variation at the intake varies from 20.5 area ratio of 0.3 to 39.1 a0.6. Dual-shock operation further sharpens the peak of the forcing function. For dual-shock operation, the amount of pressure variation at the intake varies from 21.0 a0.3 to 21.9 a0.6 for the different area ratios.
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