Reservoir Enthalpy Research Articles

Reactive and viscous flow in hypersonic nozzles

In high-enthalpy hypersonic facilities, the airflow at the exit of a convergent-divergent nozzle is affected by the high reservoir enthalpy level because chemical and vibrational nonequilibrium processes take place in the nozzle. The models in the test section are generally located at the nozzle exit, and so the knowledge of the nozzle flowfield is of upmost importance to obtain the upstream conditions for the flow around the model. This flowfield is studied numerically by solving the unsteady laminar axisymmetric Navier-Stokes equations, coupled with those describing the chemical and thermal nonequilibrium processes in the real-air gas mixture

Hypersonic flow diagnostic studies in a large arc-heated wind tunnel

This study consisted of the experimental investigation of test flow in an arc-heated hypersonic wind tunnel. These tests utilized a high-voltage d.c. arc heater which operated at input powers in excess of 50 Mw and provided reservoir pressures ranging from 100 to 1500 psi and bulk enthalpies from 1500 to 4000 Btu/lb. Local freestream measurements of Pitot pressure, mass flux, stagnation point heat-transfer rate, and wall static pressures were obtained at the exit of a nominal 2-ft-diam conical nozzle. Stagnation enthalpy profiles at the nozzle exit became peaked at high stagnation pressures. From these data, center line enthalpies as high as 6500 Btu/lb were indicated in the flow. Selective comparisons between theory and experiment are presented. At a reservoir enthalpy of approximately 2500 Btu/lb and for stagnation pressures in excess of 500 psi, the expanded flow data were in good agreement with equilibrium expansion theory. However, below 500 psi, the data compared more closely with nonequilibrium theory with the flow frozen downstream of the nozzle throat.

Experimental Investigation of the Equilibrium Interface Technique

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.