The various parametric curves in reference 6 were found to be very difficult to read accurately, Therefore, a set of more convenient curves of the various quantities and parameters for the lower range of Mach numbers has been plotted and is included for the reader's ready reference. / Master of Science

An investigation has been conducted to determine the effects of jet-to-free-stream dynamic pressure ratio on the penetration and mixing of a sonic hydrogen jet injected normal to a Mach 4 airstream. The hydrogen gas was injected from a circular nozzle flush mounted in a flat plate with a turbulent boundary-layer thickness of 2.70 injector exit diameters at the injector station. The investigation was conducted for values of the dynamic pressure ratio ranging from 0.5 to 1.5. At five downstream stations between 7 and 200 injector diameters the mixing region was surveyed to obtain hydrogen volume concentration and pressure profiles. Results of the investigation indicate that the thick boundary layer had significant effects on the penetration and maximum concentration trajectories when compared to data correlations from other sources. The penetration trajectory was found to be proportional to the dynamic pressure ratio raised to the 0.3 power. The decay of the maximum concentration was very rapid in the near field and inversely proportional to (x/dj)^0.8 at downstream distances greater than 30 jet diameters. At a particular value of x/d the maximum concentration was proportional to q_r^½. Nondimensional concentration profiles, represented by Gaussian-type functions, on the vertical centerline showed similarity at values of x/d equal to or greater than 60. / Master of Science

The design of the VPI plasma torch, which has been used as an ignitor and flameholder in supersonic combustion studies, has been modified in order to decrease the electrode wear and to increase stability. The plasma torch can be used as a source of hydrogen or nitrogen radicals which initiate and stabilize combustion. During previous testing of the unmodified torch, electrode erosion limited operation of the torch to about two hours. The improved torch features a flow swirler in the gas inlet, which adds vortex stabilization to the arc. The vortex stabilization causes the anode attachment point of the arc to be anchored in the low pressure region, downstream of the constrictor. This lowers the heat flux to the anode, so that erosion is decreased. The torch body was redesigned with an emphasis on the alignment of the electrodes. Also, the electrode gap in the improved torch was made continuously adjustable, allowing fine adjustment of the electrode gap during operation of the torch. The operational characteristics of the improved torch were monitored by a microcomputer-based data acquisition system. Stable operation of the improved torch with pure nitrogen was demonstrated, thus eliminating the requirement for argon to stabilize the arc. Operational characteristics of the improved torch running on argon, nitrogen, argon/hydrogen and argon/nitrogen mixtures as feedstocks, are reported. The electrode wear was studied between tests by observation with a microscope, and by measuring the mass change of the electrodes. The electrode erosion of the improved torch was reduced significantly. Anode lifetimes of greater than 20 hours have been demonstrated with operation on mixtures of nitrogen and argon. / Master of Science

A method is developed to solve the conical flow equations in spherical coordinates using a rectangular finite volume approach. The only mapping done is the mapping of the spherical solution surface to that of a flat plane using a stereographic projection. The mapped plane is then discretised into rectangular finite volumes. The rectangular volumes are allowed to intersect the body surface in an arbitrary manner. A full potential formulation is used to represent the flow-field velocities. The full potential formulation prevents the formation of vortices in the flow-field but all other essential features of the supersonic conical flow are resolved. An upwind density shift is used to introduce an artificial viscosity in a conservative manner to eliminate non-physical expansion shocks and add numerical damping. The rectangular finite volume method is then extended to deal with infinitely thin conical fins. Numerical tests of cones, elliptical cones, conical wing-bodies and waveriders (with very thin winglets) have been done. Very good agreement with experimental results is found. / M.S.

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Thesis (Ph. D.)--California Institute of Technology, 1995. / "UMI number: 9539115"--P. [i]. Includes bibliographical references. Available on microfilm and online via the World Wide Web.

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