关键词: 超声速射流;动压;推力

Abstract: Impact pressure distribution measurements in free and impacting cold nitrogen thruster jets operated in atmospheric and low-pressure environments, and N₂-H₂ arc-heated jets generated in low-pressure environment have been made by using a self-designed impact pressure probe. The integrated sums of the impact pressure have been compared with the thrust force measured by the impulse method. Results show that the measured impact pressure of the cold nitrogen free/impacted jets operated at atmospheric pressure exhibits subsonic flow characteristics, while that of the cold nitrogen thruster jet under low pressure environment clearly shows typical continuum under-expanded supersonic jet flow with shock wave reflections. However, the impact pressure measurements do not show clear supersonic wave structures in an N₂-H₂ arcjet operated at low pressure environment. The integrated sum over the jet cross-section of the impact pressure can be considered approximately equal to the thrust generated by the arcjet thruster if certain conditions are satisfied, i.e., the jet flow has relatively high Mach numbers.The existence of the pressure probe does not influence the jet expansion within the nozzle, and the measurements are made at a distance not too far from the jet exit where the jet velocity and density are not greatly reduced.

Key words: Supersonic jet; Impact pressure; Thrust