Experimental Investigation of the Equilibrium Interface Technique

Abstract

The equilibrium‐interface technique has been suggested as a possible shock‐tunnel driver method. If this technique is workable, reservoir enthalpy levels can be increased substantially over those obtainable with the tailored‐interface technique without any physical modification of the shock tube. In order to determine the feasibility of the equilibrium‐interface technique as a shock‐tunnel driver method, experiments were performed in a shock tube, utilizing a cold helium driver over the shock Mach number range 3.29 to 7.26. Pressure histories were measured at the end of the driven tube; this pressure was found to reach an equilibrium condition for the complete shock Mach number range investigated. From the pressure histories the equilibrium pressure, time to reach equilibrium, and test time were determined. Measured equilibrium pressures were compared with those predicted from the measured shock Mach number. From the measured equilibrium pressure the equilibrium enthalpy level was computed. The maximum equilibrium enthalpy was more than six times the reservoir enthalpy produced using the tailored‐interface technique.