State space modeling of fluid flow for thrust control in mems-based micropropulsion

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This paper presents a dynamic system approach for the modeling of fluid flow in microchannels to be used in thrust control applications. A micro-resistojet fabricated using MEMS (Microelectromechanical Systems) technology has been selected for the analysis. The device operates by vaporizing a liquid propellant, in this case water, and expelling it as gas that is accelerated by a micro-nozzle. The pressure variation due to boiling in the chamber might lead to unwanted behavior of the feed system and the frequency analysis in this case can indicate whether or not instabilities will be present. To handle this complex problem, the incompressible Navier-Stokes equations are linearized in the steady-state flow regime and then formulated in state space form to provide the necessary means for control analysis. Controllability and observability of the system are investigated considering low values of Reynolds numbers present in micro fluidics applications. Results from the analytical treatment are compared with CFD (Computational Fluid Dynamics) simulations of the microchannel to demonstrate the validity of the approach investigated