Micronozzles represent a unique flow regime defined by low Reynolds numbers ( R e < 1000 ) and supersonic Mach numbers. Currently, the classic method of calculating thrust is used by the micropropulsion community to determine nozzle performance from simulation data. This approach accounts for momentum flux and pressure imbalance at the nozzle exit, and it assumes that the viscous stress tensor’s contribution to thrust is negligible. This assumption, however, can break down at low Reynolds numbers, where viscous forces play a significant role in the flow dynamics. In this paper, an extended method of calculating thrust, which accounts for the force due to the viscous stress tensor, is derived from the Navier–Stokes equation. Computational fluid dynamic simulations are then used to assess and quantify the error produced by the classic method at low Reynolds numbers ( 80 < R e < 800 ). Two micronozzle geometries are used as test cases: 1) an 80 % truncated planar plug nozzle, and 2) a 30 deg linear-walled planar de Laval nozzle. Results indicate that the accuracy of the classic method begins to break down at R e 1000 , below which there is a significant risk that the classic method will produce erroneous results. Moreover, for R e < 100 , the classic method has the potential to misrepresent the thrust of a simulated micronozzle by 50%.


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    Title :

    Thrust Calculation for Low-Reynolds-Number Micronozzles


    Contributors:
    Pearl, J. M. (author) / Louisos, W. F. (author) / Hitt, D. L. (author)

    Published in:

    Publication date :

    2016-12-28


    Size :

    12 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English







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