Gasdynamical detectors of driver gas contamination in a high-enthalpy shock tunnel

Simple gasdynamical devices consisting of a duct and a wedge have been applied to the detection of driver gas arrival in the test section of a high-enthalpy shock tunnel. Static pressure in the duct has been measured during a shot, and the time of driver gas arrival has been determined by the onset of the pressure rise, which indicates duct flow choking. The ability to detect driver gas in small concentrations is critical to the satisfactory performance of the device. Duct internal flows for various wedge angles have been numerically simulated to clarify the flow choking mechanism. The simulations give an idea of the improvement of detector sensitivity, and modified configurations of the detector are proposed. Flow visualization in the duct leads to a better understanding of pressure traces obtained, and pressure measurement data show a satisfactory degree of sensitivity