Long stroke isentropic free piston hypersonic wind tunnel

Abstract

The application of a long stroke isentropic free piston compressor as the energy source for an intermittent M = 6.85 hypersonic wind tunnel is described. The advantages of comparatively long running times of up to 0.5 s and uniform reservoir conditions at up to 90 bar and 600 K are discussed. Particular problems arising from the long stroke compression associated with both viscous flow effects and non-steady wave propagation are discussed and solutions suggested. The theoretical operating principles of long stroke compression tubes are presented and experimental results are given for a pilot facility with com- pression tube diameter of 0.032 m and length to diameter ratio of 120 and for a full scale facility with corresponding values of 0.11 m and 114.