No description available.

No description available.

No description available.

No description available.

No description available.

An inverse method for the design of exhaust nozzles with a specified transonic pressure distribution is presented. A problem of mixed Neumann and Dirichlet boundary condition is solved. A successive line relaxation process is used to solve the array of velocity potentials in the entire flow field. The streamlines are then displaced to produce boundaries which match a desired pressure distribution. Various cases are tested to verify the reliability of the method. The design calculation proves to be efficient and accurate. / M.S.

Ph. D.

An experimental evaluation of normal, sonic, helium injection from a wedgeshaped nozzle and a circular nozzle into a Mach 3 free stream with a total pressure of 6.5 atm and a total temperature of 294 K was conducted. The expansion ratio and the mass rate of flow of both nozzles were matched in order to determine the effect of the geometric difference only. 'Decay rate, penetration, and jet area growth rate were used to compare the mixing performance of the nozzles. Oil flow photography was used to determine the size of the three-dimensional boundary layer separation zone in front of each nozzle, and nanoshadowgraph photography was used to visualize the system of shocks and the flow field of each nozzle. Mean flow quantity profiles at several lateral stations were made at three downstream locations. The profiles were used to calculate helium concentration, Mach number, static temperature, static pressure, density, flow velocity, local speed of sound, mass flux, and total pressure. The two nozzles were then compared on the basis of maximum helium concentration decay, core center and overall penetration, and the growth rate and centroid penetration of a defined jet area. Although the decay rate of the jet from the circular nozzle was slightly higher than the decay rate of the jet from the wedge-shaped nozzle, the mixing performance of the wedge-shaped nozzle exceeded that of the circular nozzle in all other comparison parameters. The jet from the wedge-shaped nozzle penetrated further and its area grew more rapidly than the same parameters for the jet from the circular nozzle. The oil flow photography showed that the wedge-shaped nozzle also had no separation zone in front of it, whereas the circular nozzle had a large separation zone. A separation zone in front of a fuel injector in a scramjet engine can result in damage to the combustor from the extreme heat fluxes to the wall. Also, the total pressure loss in the combustor should be lower for fuel injection through a wedge-shaped nozzle due to the elimination of the normal shock. It was concluded that wedge-shaped fuel injectors should perform better than circular fuel injectors in supersonic combustors. / Master of Science

M. S.

This work discusses the development of a compact Tunable Diode Laser Absorption Spectrometer (TDLAS) for gas phase mixing ratio and temperature measurements of condensible vapors, in particular H2O and D2O, in supersonic flows. Through extensive pressure trace measurements and mass balances on the incoming species, the expected mixing ratio and temperature profiles of the condensible species along the supersonic nozzle have been characterized. Using a Tunable Diode Infrared laser operating in the 8 microns region, the possibility of nonintrusively measuring the gas phase mixing ratio and the temperature (even simultaneously) in a supersonic nozzle is demonstrated. The acquired spectroscopic data and the pressure trace measurements are compared and the results suggest the possibility to improve the instrument set-up and to improve the quality of the measurements. Also, the interpretation of our initial experimental results and the comparison with the pressure traces measurements suggest reasons to further investigate the condensation behavior of D2O and H2O.