Mixing and combustion studies using discrete orifice injection at hypervelocity flight conditions
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Bakos, R.↗
Engineering topics
Rizkalla, O.
Publications and source records attributed to Rizkalla, O..
Hypersonic mixing and combustion studies in the hypulse facility
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Bakos, R. J.↗
Mixing, ignition and combustion studies using discrete orifice injection at hypervelocity flight conditions
Testing at hypervelocity test conditions continues in the Hypulse expansion tube. A newly-calibrated Mach 13 operating point has been achieved, and hydrogen injection studies were performed at this test condition. The experiments were conducted in a 2-in x 1-in combustor model employing three injector configurations: a single flush-wall circular orifice; two such orifices on opposite walls (the 'dual' injector configuration); and two orifices on the upper and the lower walls (the 'quad' injector configuration). The quad injectors were distinctly superior to the other two configurations in promoting mixing, ignition, and combustion. The single injector, however, proved to be superior to the dual injectors, supporting the concept that the aspect ratio of the 'injection cell' plays a large role in promoting the processes required to achieve high combustion efficiency.
Bakos, R.↗
High pressure Mach 10 to 20 electrothermal hypersonic wind tunnel
A new technique is described for generating high enthalpy, long pulse flows for testing scramjet combustors at equivalent flight Mach numbers of 10 to 20. The approach derives from high pressure discharge technology developed for electrothermal guns and space thrusters. Cryogenic liquid air is heated with a high power electric discharge (500 MW for a 15 kg/sec test flow rate) in a capillary tube, generating a quasi-steady pressure of up to 6800 atm at 20,000 K. The heated air is mixed with additional cryogenic air and is expanded in a conventional supersonic nozzle to 0.5 to 1 atm at 3000 to 6000 m/sec. Combustion and nozzle expansion test time of approximately 300 m/sec are contemplated. Facility nozzle chemical kinetics calculations show that above Mach 16 increasing concentrations of argon and oxygen replenishment are required to obtain suitable test conditions. Initial experiments on a subscale test rig are described for 0.5 kg/sec and 300 atm pressure.
Burton, R. L.↗
Hypersonic Mixing and Combustion Studies in the GASL HYPULSE Facility
Hydrogen-air mixing and combustion experiments at air velocities approaching 17,000 ft/s have been conducted in the expansion tube in CASL's HYPULSE facility. The data were obtained in the facility's sub-millisecond steady flow test period. The results proved to be repeatable and indicated increasing extent of reaction as the fuel-air ratio was increased from stoichiometric to three times stoichiometric. Comparisons were made with the results from a one-dimensional, finite-rate chemistry code and from one-dimensional cycle codes which 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 that the relevant physical phenomena are accounted for in the computations.
Bakos, R. J.↗
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.
Rizkalla, O.↗