Continuum modeling on nozzle flows has been conducted and validated by available experimental data. The simulated nozzle exit thrust is in good agreement with the experimental data except at very low Reynolds number, which could possibly be due to the effects of backpressure and the boundary layer growth. Velocity profiles at the throat and the exit demonstrate a regular parabolic nature for throat Reynolds number ranging from 0.15 to 23.2. Extended simulations for throat Reynolds number up to 2000 reveal that helium could produce the highest specific impulse, followed by nitrogen and argon. Parametric study indicates that in slip flow regime, slip and no-slip flow simulations could generate similar results. When the flow is switching from slip to transition and continuum regime, no-slip condition would always predict a larger thrust value than slip flow condition. In continuum regime, no-slip condition would predict a thrust value much closer to the experimental data. At Rethroat = 18.5 and P(Ind 0) = 17 Torr, when the nozzle throat diameter is decreasing from D = 1 mm to 0.2 mm, the flow switches from continuum to slip flow regimes and the maximum exit thrust is generated at D = 0.8 mm, where the flow regime transition starts. The velocity profiles change dramatically at throat diameter of D = 0.4 mm and below, which might draw concerns on the validity of continuum modeling at this dimension,
Continuum modeling of gas flows in micronozzles
Kontinuumsmechanische Modellierung von Gasströmungen in Mikrodüsen
2005
6 Seiten, 10 Bilder, 11 Quellen
Conference paper
English
Flow characteristics of micronozzles
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