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

摘要： 采用自行设计的动压探针,测量了大气压和真空环境下冷态氮气自由/冲击射流动压分布,以及真空环境下氮/氢混合气电弧加热推力器羽流的动压分布。将动压径向分布积分所得结果与冲击平板法间接测得的推力值做了比较。结果表明,大气压环境下测得的冷态氮气自由/冲击射流动压分布呈现明显的亚声速流动的特点,真空环境下测得的冷态射流动压显示有波系存在的超声速流动状态；而氮/氢混合气电弧加热推力器羽流的动压分布中看不出羽流中明显的激波存在。在一定条件下,即在较高马赫数的超声速射流中,探针不影响气流在喷管内的膨胀过程,以及羽流速度和密度没有过分降低的区间内,动压探针测量数据径向积分的结果可以代表电弧加热推力器的推力。

关键词: 超声速射流;动压;推力