Proposed Vertical Expansion Tunnel
It is proposed that the adverse effects from secondary diaphragm rupture in an expansion tunnel may be reduced or eliminated by orienting the tunnel vertically, matching the test gas pressure and the accelerator gas pressure, and initially separating the test gas from the accelerator gas by density stratification. This proposed configuration is termed the vertical expansion tunnel. Two benefits are 1) the removal of the diaphragm particulates in the test gas after its rupture, and 2) the elimination of the wave system that is a result of a real secondary diaphragm having a finite mass and thickness. An inviscid perfect-gas analysis and quasi-one-dimensional Euler computations are performed to find the available effective reservoir conditions (pressure and mass specific enthalpy) and useful test time in a vertical expansion tunnel for comparison to a conventional expansion tunnel and a reflected-shock tunnel. The maximum effective reservoir conditions of the vertical expansion tunnel are higher than the reflected-shock tunnel but lower than the expansion tunnel. The useful test time in the vertical expansion tunnel is slightly longer than the expansion tunnel but shorter than the reflected-shock tunnel. If some sacrifice of the effective reservoir conditions can be made, the vertical expansion tunnel could be used in hypervelocity ground testing without the problems associated with secondary diaphragm rupture.
© 2013 by Nick Parziale. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Received 13 October 2012; revision received 19 April 2013; accepted for publication 16 June 2013; published online 16 October 2013. Presented as Paper 2012-3263 at the 42nd AIAA Fluid Dynamics Conference and Exhibit, New Orleans, LA, 25–28 June 2012. The authors would also like to thank Siddhartha Verma for his contribution to the work. This work was an activity that was part of National Center for Hypersonic Laminar-Turbulent Research, sponsored by the "Integrated Theoretical, Computational, and Experimental Studies for Transition Estimation and Control" project supported by the U.S. Air Force Office of Scientific Research and the National Aeronautics and Space Administration (FA9552-09-1-0341). The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the U.S. Air Force Office of Scientific Research or the U.S. Government.
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