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  • 1
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    Test Medium Effects on Ignition, Combustion and Flameholding Processes in Scramjet Combustors (2000)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: The total temperatures (enthalpies) required to ground-test air-breathing (aero-propulsion) engines at high Mach number flight conditions can be achieved in a number of ways. Among these are: 1. Heat exchangers, including pre-heated ceramic beds. 2. direct electrical heating, e.g., arc discharge and resistance heaters. 3. Compression heating. 4. Shock heating, and 5. In-stream combustion, with oxygen replenishment to match air content. Each method has distinct advantages, disadvantages and limitations. All have a common characteristic of being designed for intermittent flow, due to the extreme energy required for continuous operation at simulated Mach numbers above about 3. All also distort the composition of atmospheric air to some degree, due to the high temperatures that occur in the plenum section prior to expansion of the flow to simulated flight conditions. In the case of in-stream combustion, the resulting test medium is commonly referred to as "vitiated air", being composed of oxygen, nitrogen and some fraction of combustion products.
    Keywords: Aircraft Propulsion and Power
    Type: JANNAF 25th Airbreathing Propulsion Subcommittee, 37th Combustion Subcommittee and 1st Modeling and Simultation Subcommittee Joint Meeting; Volume 1; 243-271; CPIA-Publ-703-Vol-1
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  • 2
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    Using a global hydrogen-air combustion model in turbulent reacting flow calculations (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 06, p. 836, Accession no. A82-17790)
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
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  • 3
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    Mixing, ignition and combustion studies using discrete orifice injection at hypervelocity flight conditions (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: 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.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-2396
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  • 4
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    A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computationally-viable model describing the interaction between fluid-mechanical turbulence and finite-rate combustion reactions, principally in high-speed flows was developed. Chemical kinetic mechanisms, complete and global, were developed describing the finite rate reaction of fuels of interest to NASA. These fuels included principally hydrogen and silane, although a limited amount of work involved hydrocarbon fuels as well.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: NASA-CR-181227 , NAS 1.26:181227
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  • 5
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    Premixed shock-induced combustion studies in the hypulse facility (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Engine performance calculations strongly suggest that the oblique detonation-wave engine can outperform the diffusive-burning scramjet engine in the high hypervelocity flight regime; i.e., at flight Mach numbers exceeding about 14. Research is described that examines and characterizes the behavior of oblique detonation waves (ODW). The effort is both computational and experimental, the latter utilizing the NASA Hypulse expansion tube. The experimental work is hampered by preignition of the hydrogen-oxygen-helium mixtures in either the intermediate or acceleration sections of the facility. The experiments are described and possible causes of this preignition are discussed. Initial results obtained from a parallel computation effort indicate that temporally steady ODW are achievable in the Hypulse facility.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 92-3427
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  • 6
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    High pressure Mach 10 to 20 electrothermal hypersonic wind tunnel (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: 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.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: Johns Hopkins Univ., The 1990 JANNAF Propulsion Meeting, Volume 1; p 211-226
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  • 7
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    Theoretical studies of the ignition and combustion of silane-hydrogen-air mixtures (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A chemical kinetic mechanism is proposed for the combustion of silane-hydrogen-oxygen-nitrogen mixtures in the initial temperature range from 800K to 1250K and pressure range from 0.5 to 1.35 atm. The mechanism yields results which are in agreement with published ignition delay times obtained from shock tube experiments. Comparisons between the results obtained using the proposed mechanism and that of an alternative mechanism reveal that the former predicts appreciably shorter ignition delay times, but a flame blowout envelope which is shifted so as to decrease the stable flame region. Over much of the thermodynamic range examined, the mechanism predicts long reaction times. A three step global mechanism is proposed which closely models the ignition phase of SiH4 - H2 - air combustion; however, the reaction phase is less well reproduced by the global model. The necessity for additional experimental data to further assess the proposed models is stressed.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: NASA-CR-3876 , NAS 1.26:3876
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  • 8
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    A model for reaction rates in turbulent reacting flows (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: To account for the turbulent temperature and species-concentration fluctuations, a model is presented on the effects of chemical reaction rates in computer analyses of turbulent reacting flows. The model results in two parameters which multiply the terms in the reaction-rate equations. For these two parameters, graphs are presented as functions of the mean values and intensity of the turbulent fluctuations of the temperature and species concentrations. These graphs will facilitate incorporation of the model into existing computer programs which describe turbulent reacting flows. When the model was used in a two-dimensional parabolic-flow computer code to predict the behavior of an experimental, supersonic hydrogen jet burning in air, some improvement in agreement with the experimental data was obtained in the far field in the region near the jet centerline. Recommendations are included for further improvement of the model and for additional comparisons with experimental data.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-85746 , L-15679 , NAS 1.15:85746
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  • 9
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    The effect of temperature fluctuations of reaction rate constants in turbulent reacting flows (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Current models of turbulent reacting flows frequently use Arrhenius reaction rate constants obtained from static or laminar flow theory and/or experiments, or from best fits of static, laminar, and turbulent data. By treating the reaction rate constant as a continuous random variable which is temperature-dependent, the present study assesses the effect of turbulent temperature fluctuations on the reaction rate constant. This model requires that a probability density function (PDF) describing the nature of the fluctuations be specified. Three PDFs are examined: the clipped Gaussian, the beta PDF, and the ramp model. All the models indicate that the reaction rate constant is greater in a turbulent flow field than in an equivalent laminar flow. In addition, an amplification ratio, which is the ratio of the turbulent rate constant to the laminar rate constant, is defined and its behavior as a function of the mean temperature fluctuations is described
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: In: Fluid mechanics of combustion systems; June 22, 23, 1981; Boulder, CO
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  • 10
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    Nonlinear combustion instability in liquid-propellant rocket motors Final report (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Mathematical models of nonlinear combustion instabilities in liquid propellant rocket engine
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-119182 , MR-6903
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