A numerical investigation of transient supersonic flow through a two-dimensional linear micronozzle has beennperformed. The baseline model for the study is derived from the NASA Goddard Space Flight Centernmicroelectromechanical-systems-based hydrogen peroxide prototype microthruster. A hyperbolic-tangentnactuation profile is used to simulate the opening and closing of a microvalve with a maximum inlet stagnationnpressure of 250 kPa, which generates a maximum throat Reynolds number of Re u0001 800. The complete duty cyclenoccurs over 1.7ms.Numerical simulations have been conducted for expander half-angles of 10–50u0002n, and both slip andnno-slip wall boundary conditions have been examined. The propulsion scheme employs 85%-pure hydrogennperoxide as the monopropellant fuel. Simulation results have been analyzed, and thrust production as a function ofntime has been quantified, along with the total impulse delivered. Micronozzle impulse efficiency has also beenndetermined based on a theoretical maximum impulse achieved by a quasi-1-D inviscid flow respondingninstantaneously to the actuation profile. It is found that both the flow and thrust exhibit a response lag to the time-nvarying inlet pressure profile. Simulations indicate that a maximum efficiency and impulse occur for an expandernhalf-angle of 30u0002nfor the no-slip wall boundaries, and the slip simulations demonstrate a maximum plateau in thenrange of 20–30u0002n; these angles are significantly larger than with traditional conical nozzle designs.
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