Repetitively Pulsed Hypersonic Flow Apparatus for Diagnostic Development

Arepetitively pulsed hypersonic test facility has been constructed and characterized. This apparatuswas designed to enable advanced laser diagnostic development. The underlying principle is to synchronize the intermittent tunnel operation with the laser pulses to achieve effectively continuous operation. Repetitively pulsed (2–20 ms pulse lengths) uniform supersonic flow at Mach 4.6 and hypersonic flow at Mach 6.2 were demonstrated for extended operation. The nozzle flows were characterized using fast-response pressure sensors and NO planar laser-induced fluorescence imaging for two-dimensional temperature and velocity measurements. The pulse-to-pulse impact pressure repeatability was within 1.0%, corresponding to exit flow velocity and temperature fluctuations of 0.7 and 1.0%, respectively. The apparatus can operate over a unit Reynolds number range of 6:0 104 to 3:0 106 m1. Nomenclature Cp = heat capacity at constant pressure Cv = heat capacity at constant volume C12 = experimentally determined calibration constant De = exit diameter of nozzle Ds = diameter of subsonic section of nozzle Dt = throat diameter of nozzle k = Boltzmann constant M = Mach number m = mass Pi = impact pressure P0 = stagnation pressure P02 = pitot pressure Sf = fluorescence signal intensity Trot = rotational temperature Tw = wall temperature T0 = stagnation temperature = ratio of heat capacities, Cp=Cv E21 = energy difference between rotational states I.