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  • 1
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    OH PLIF visualization of the UVa supersonic combustion experiment: configuration A (2014)
    Springer
    Details
    Publication Date: 2014-03-01
    Print ISSN: 1343-8875
    Electronic ISSN: 1875-8975
    Topics: Computer Science
    Published by Springer
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    PAPER CURRENT
  • 2
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    OH PLIF Visualization of the UVa Supersonic Combustion Experiment: Configuration A (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) measurements were performed in the University of Virginia s dual-mode scramjet experiment. The test section was set up in configuration A, which includes a Mach 2 nozzle, combustor, and extender section. Hydrogen fuel was injected through an unswept compression ramp at two different equivalence ratios. Through the translation of the optical system and the use of two separate camera views, the entire optical range of the combustor was accessed. Single-shot, average, and standard deviation images of the OH PLIF signal are presented at several streamwise locations. The results show the development of a highly turbulent flame structure and provide an experimental database to be used for numerical model assessment.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NF1676L-14920 , 42nd AIAA Fluid Dynamics Conference and Exhibit; Jun 25, 2012 - Jun 28, 2012; New Orlean, LA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "C" (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Measurements have been conducted at the University of Virginia Supersonic Combustion Facility in configuration C of the dual-mode scramjet. This is a continuation of previously published works on configuration A. The scramjet is hydrogen fueled and operated at two equivalence ratios, one representative of the scram mode and the other of the ram mode. Dual-pump CARS was used to acquire the mole fractions of the major species as well as the rotational and vibrational temperatures of N2. Developments in methods and uncertainties in fitting CARS spectra for vibrational temperature are discussed. Mean quantities and the standard deviation of the turbulent fluctuations at multiple planes in the flow path are presented. In the scram case the combustion of fuel is completed before the end of the measurement domain, while for the ram case the measurement domain extends into the region where the flow is accelerating and combustion is almost completed. Higher vibrational than rotational temperature is observed in those parts of the hot combustion plume where there is substantial H2 (and hence chemical reaction) present.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA Paper 2013-0335 , NF1676L14873 , 51st AIAA Aerospace Sciences Meeting; Jan 07, 2013 - Jan 10, 2013; Grapevine, TX; United States
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    NASA TECHNICAL REPORTS
  • 4
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    OH PLIF Visualization of the UVa Supersonic Combustion Experiment: Configuration C (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Non-intrusive hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) measurements were obtained in configuration C of the University of Virginia supersonic combustion experiment. The combustion of hydrogen fuel injected through an unswept compression ramp into a supersonic cross-flow was imaged over a range of streamwise positions. Images were corrected for optical distortion, variations in the laser sheet profile, and different camera views. Results indicate an effect of fuel equivalence ratio on combustion zone shape and local turbulence length scale. The streamwise location of the reaction zone relative to the fuel injector was also found to be sensitive to the fuel equivalence ratio. The flow boundary conditions in the combustor section, which are sensitive to the fuel flow rate, are believed to have caused this effect. A combination of laser absorption and radiative trapping effects are proposed to have caused asymmetry observed in the images. The results complement previously published OH PLIF data obtained for configuration A along with other non-intrusive measurements to form a database for computational fluid dynamics (CFD) model validation.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA Paper 2013-0034 , NF1676L-14828 , 51st AIAA Aerospace Sciences Meeting; Jan 07, 2013 - Jan 10, 2013; Grapevine, TX; United States
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  • 5
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    Measurement of Vibrational Non-Equilibrium in a Supersonic Freestream Using Dual-Pump CARS (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Measurements have been conducted at the University of Virginia Supersonic Combustion Facility of the flow in a constant area duct downstream of a Mach 2 nozzle, where the airflow has first been heated to approximately 1200 K. Dual-pump CARS was used to acquire rotational and vibrational temperatures of N2 and O2 at two planes in the duct at different downstream distances from the nozzle exit. Wall static pressures in the nozzle are also reported. With a flow of clean air, the vibrational temperature of N2 freezes at close to the heater stagnation temperature, while the O2 vibrational temperature is about 1000 K. The results are well predicted by computational fluid mechanics models employing separate "lumped" vibrational and translational/rotational temperatures. Experimental results are also reported for a few percent steam addition to the air and the effect of the steam is to bring the flow to thermal equilibrium.
    Keywords: Aerodynamics
    Type: NF1676L-13801 , 28th Aerodynamic Measurement Technology, Ground Testing, and Flight Testing Conference; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 6
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    Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "A" (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this paper we describe efforts to obtain canonical data sets to assist computational modelers in their development of models for the prediction of mixing and combustion in scramjet combustors operating in the ramjet-scramjet transition regime. The CARS technique is employed to acquire temporally and spatially resolved measurements of temperature and species mole-fraction at four planes, one upstream of an H2 fuel injector and three downstream. The technique is described and results are presented for cases with and without chemical reaction. The vibrational energy mode in the heated airstream of the combustor was observed to be frozen at near facility heater conditions and significant nonuniformities in temperature were observed, attributed to nonuniformities of temperature exiting the heater. The measurements downstream of fuel injection show development of mixing and combustion, and are already proving useful to the modelers.
    Keywords: Aircraft Design, Testing and Performance
    Type: AIAA Paper 2012-0114 , NF1676L-13977 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
    Format: application/pdf
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  • 7
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    OH PLIF Visualization of the UVa Supersonic Combustion Experiment: Configuration A (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) measurements were performed in the University of Virginia supersonic combustion experiment. The test section was set up in configuration A, which includes a Mach 2 nozzle, combustor, and extender section. Hydrogen fuel was injected through an unswept compression ramp at two different equivalence ratios. Through the translation of the optical system and the use of two separate camera views, the entire optically accessible range of the combustor was imaged. Single-shot, average, and standard deviation images of the OH PLIF signal are presented at several streamwise locations. The results show the development of a highly turbulent flame structure and provide an experimental database to be used for numerical model assessment.
    Keywords: Instrumentation and Photography
    Type: NF1676L-16899
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Dual-Pump CARS Development and Application to Supersonic Combustion (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A dual-pump Coherent Anti-Stokes Raman Spectroscopy (CARS) instrument has been developed to obtain simultaneous measurements of temperature and absolute mole fractions of N2, O2 and H2 in supersonic combustion and generate databases for validation and development of CFD codes. Issues that compromised previous attempts, such as beam steering and high irradiance perturbation effects, have been alleviated or avoided. Improvements in instrument precision and accuracy have been achieved. An axis-symmetric supersonic combusting coaxial jet facility has been developed to provide a simple, yet suitable flow to CFD modelers. Approximately one million dual-pump CARS single shots have been collected in the supersonic jet for varying values of flight and exit Mach numbers at several locations. Data have been acquired with a H2 co-flow (combustion case) or a N2 co-flow (mixing case). Results are presented and the effects of the compressibility and of the heat release are discussed.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/CR-2012-217569 , NF1676L-14665
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  • 9
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    Development of an Actuator for Flow Control Utilizing Detonation (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-11
    Description: Active flow control devices including mass injection systems and zero-net-mass flux actuators (synthetic jets) have been employed to delay flow separation. These devices are capable of interacting with low-speed, subsonic flows, but situations exist where a stronger crossflow interaction is needed. Small actuators that utilize detonation of premixed fuel and oxidizer should be capable of producing supersonic exit jet velocities. An actuator producing exit velocities of this magnitude should provide a more significant interaction with transonic and supersonic crossflows. This concept would be applicable to airfoils on high-speed aircraft as well as inlet and diffuser flow control. The present work consists of the development of a detonation actuator capable of producing a detonation in a single shot (one cycle). Multiple actuator configurations, initial fill pressures, oxidizers, equivalence ratios, ignition energies, and the addition of a turbulence generating device were considered experimentally and computationally. It was found that increased initial fill pressures and the addition of a turbulence generator aided in the detonation process. The actuators successfully produced Chapman-Jouguet detonations and wave speeds on the order of 3000 m/s.
    Keywords: Aircraft Stability and Control
    Type: NASA/CR-2004-213508
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  • 10
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    Numerical Analysis of the SCHOLAR Supersonic Combustor (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The SCHOLAR scramjet experiment is the subject of an ongoing numerical investigation. The facility nozzle and combustor were solved separate and sequentially, with the exit conditions of the former used as inlet conditions for the latter. A baseline configuration for the numerical model was compared with the available experimental data. It was found that ignition-delay was underpredicted and fuel-plume penetration overpredicted, while the pressure rise was close to experimental values. In addition, grid-convergence by means of grid-sequencing could not be established. The effects of the different turbulence parameters were quantified. It was found that it was not possible to simultaneously predict the three main parameters of this flow: pressure-rise, ignition-delay, and fuel-plume penetration.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/CR-2003-212689
    Format: application/pdf
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