This study directly measures the performance of a thruster nozzle using water vapor as propellant in the Reynolds number below 1000. Because of its properties, water is suitable as a propellant for small satellites, often with a low-Reynolds-number flow using a micronozzle. The low Reynolds number of the flow and the phase changes in supersonic vapor flow should affect nozzle performance. It is essential to measure thrust performance and consider the flow dynamics inside the nozzle, but to date there have been few direct thrust measurements at low Reynolds numbers from 100 to 600 and different temperatures of the vapor from 290 to 400 K. In this study, nozzle performance is evaluated using two dimensionless numbers: the discharge coefficient and the specific impulse efficiency. The results presented here are specific to water vapor. The discharge coefficient remains almost the same under these conditions and higher than those of argon and nitrogen. The specific impulse efficiency depends on the degree of superheating above Reynolds numbers of about 250, but shows little dependence below Reynolds numbers of about 250 owing to the combined effects of viscosity and phase change.

这项研究直接测量了在雷诺数小于1000时使用水蒸气作为推进剂的推进器喷嘴的性能。由于其特性，水适合用作小型卫星的推进剂，通常使用微喷嘴时雷诺数较低。较低的雷诺数和超音速蒸气流的相变会影响喷嘴的性能。测量推力性能并考虑喷嘴内部的流动动力学非常重要，但是迄今为止，在低雷诺数（100至600）和不同温度的蒸汽（290至400 K）下，几乎没有直接推力测量。在这项研究中，使用两个无因次数评估喷嘴性能：排放系数和比冲效率。此处显示的结果特定于水蒸气。在这些条件下，放电系数几乎保持不变，并且高于氩气和氮气。比脉冲效率取决于雷诺数大于约250的过热程度，但是由于粘度和相变的综合作用，显示低于雷诺数约250的几乎没有依赖性。