Wallace Chinitz

Hypersonic mixing and combustion studies in the hypulse facility

Hydrogen-air mixing and combustion experiments at air velocities approaching 17,000 ft/s have been conducted in the HYPULSE facility expansion tube. The results proved to be repeatable and indicated increasing extent of reaction as the fuel equivalence ratio was increased from one to three. Comparisons were made with the results of a one-dimensional, finite-rate chemistry code and one-dimensional cycle codes that assume equilibrium chemistry. These comparisons indicate that the magnitudes and trends of the measured longitudinal pressure distributions are predicted by the one-dimensional codes provided the relevant physical phenomena are accounted for in the computations.

Facility opportunities and associated stream chemistry considerations for hypersonic air-breathing propulsion

Wallace Chinitz is a Principal Scientist at General Applied Science Laboratories (GASL) as well as a Professor of Mechanical Engineering at Cooper Unions Nerken School of Engineering. He received his Ph.D. from the Polytechnic Institute of Brooklyn in 1962, and taught at that institution before leaving to conduct research at GASL until 1972. Dr. Chinitz began his career at the Fairchild Engine Division in 1957, then worked at Republic Aviation Corporation until 1960. He has published over 100 articles, papers, and reports. Dr. Chinitz is an Associate Fellow of the AIAA and is a member of the ASME, the ASEE, and the Combustion Institute.

Calculated chemical and vibrational nonequilibrium effects in hypersonic nozzles

A method of characteristics computer program has been developed for designing shock-free scramjet engine nozzles, including the effects of finite-rate chemistry and vibrational relaxation. The program incorporates a compressible, turbulent boundary-layer calculation to determine boundary-layer displacement thickness, and skin friction coefficient. Results obtained for a generic nozzle designed for a Mach 20 flight condition lead to the conclusions that finite-rate chemical recombination and viscous effects are of major consequence in determining nozzle design and performance, but that the vibrational mode is in equilibrium throughout the nozzle. In addition, nozzle design may be tailored to produce a certain geometry and performance characteristics by specifying a priori parameters such as design exit pressure ratio and maximum permissible wall angle.

Investigation of Short Contact Time Reactors for Regeneratively Cooled Hypersonic Vehicles

To counter the extreme heat loads experienced by hypersonic engine structures, it is imperative that fuels double as coolants. However, the use of logistical fuels (e.g., JP-7 and JP-10) in hypersonic applications is becoming more accepted in near-term flight engine test applications. In order for hydrocarbon based fuels to be viable as scramjet fuels they must be able to absorb heat in the form of sensible, latent, and chemical enthalpies, while attempting to minimize coke formation. In this study, we attempt to achieve these ends using a short contact time (SCT) catalytic reactor. This type of reactor has the advantages of short residence times, enhanced wake mixing, and heat conduction into the core flow of the process stream, while minimizing pressure losses. In this investigation, we have performed experiments using a series of different catalysts (Pt- αAl2O3, Pd-αAl2O3, and zeolite) on a set of logistical fuels (JP-7, JP-8, JP-10 and S-8, a synthetic hydrocarbon fuel currently being investigated by the USAF). Experiments were performed at low (1-3 atmospheres) and elevated (40-50 atmospheres) pressures, at temperatures expected in a hypersonic engine heat exchanger. Experiments measured the production of various gas-phase and liquidphase species in the reactors as a function of pressure, temperature, residence time, and catalyst formulation. Results show the production of small (H2, C1 – C3) species in the gas phase, with a shift from hydrogen and ethylene formation at low pressures towards methane and ethane formation at elevated pressures. In addition, experiments have shown significant coke formation at elevated pressures for all of the fuels investigated. Detailed kinetic modeling has identified shortcomings in models used for describing the pyrolysis of these fuels.

Use of an expansion tube to examine scramjet combustion at hypersonic velocities

Combustion testing at total enthalpy conditions corresponding to flight Mach numbers in excess of 12 requires the use of impulse facilities. The expansion tube is the only operational facility of its size which can provide these conditions without excessive oxygen dissociation or driver gas contamination. Expansion tube operation is described herein and the operational parameters having the largest impact on its performance are determined. These are: driver-to-intermediate chamber pressure ratio, driver gas molecular weight and specific heat ratio, and driver gas temperature. Increases in the last-named parameter will markedly affect the test section static pressure. Preliminary calibration tests are discussed and test gas conditions which have been achieved are presented. Calculated and experimental test times are compared and the parameters affecting test time are discussed. The direction of future work using this important experimental tool is indicated.