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  • 1
    Publication Date: 2018-12-01
    Description: The complex cepstrum is used to correct bearing estimations of acoustic sources in the presence of a reflective surface. An automated liftering procedure is used which zeros out a block portion of the cepstrum including the echo information. The problem of the resulting distortion is alleviated by applying a coherence criterion to the recovered direct signals at each microphone. Thus to a large degree the interactive nature of cepstral processing is overcome for this application. For the test signals and geometries considered the cepstrum is shown to accurately correct for bearing errors in acoustic signals contaminated with reflections from nearby surfaces.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 87-0014
    Format: text
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  • 2
    Publication Date: 2018-12-01
    Description: The present model for fan rotor/support strut airfoil interaction uses a time-marching code for the rotor flow, coupled with a potential flow model for the stator-strut region. Study of the effect of strut design variables indicates that rotor flow disturbance is increased by the primary variables of larger strut thickness and circumferential spacing, while decreasing exponentially with increased rotor-strut separation. The time-marching code predicts local rotor pressure and flow perturbations in response to an unsteady downstream boundary condition.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-2282
    Format: text
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  • 3
    Publication Date: 2013-08-31
    Description: An investigation which was designed to provide insight into the fundamental aspects of fan rotor-downstream strut interaction was undertaken. High response, miniature pressure transducers were embedded in the rotor blades of an experimental fan rig. Five downstream struts were placed at several downstream locations in the discharge flow annulus of the single-stage machine. Significant interaction of the rotor blade surface pressures with the flow disturbance produced by the downstream struts was measured. Several numerical procedures for calculating the quasi-steady rotor response due to downstream flow obstructions were developed. A preliminary comparison of experimental and calculated fluctuating blade pressures on the rotor blades shows general agreement between the experimental and calculated values.
    Keywords: AERODYNAMICS
    Type: NASA-CR-175756 , NAS 1.26:175756 , IR-1
    Format: application/pdf
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  • 4
    Publication Date: 2018-12-01
    Description: In the present study of the unsteady pressure field produced on fan rotor blades by interaction with downstream struts, a single stage, low speed axial-flow fan was instrumented with blade-mounted high frequency pressure transducers. In addition, stationary pressure problems were used to map out the flowfield. Fluctuating pressure measurements are presented for blade midspan and 85-percent span on both the suction and pressure surfaces of the rotor blades at several positions of the downstream struts, and for two different flow coefficients. The strut is found to produce an effect on the unsteady pressure field on the rotor blades; this effect exceeds that due to the stator at design rotor-stator-strut spacing, but it rapidly declines as the struts are moved downstream.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 86-1870
    Format: text
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  • 5
    Publication Date: 2018-12-01
    Description: The objective of the work reported herein was to explore the use of a continuous operation plasma torch as an ignitor and flameholder for scramjet combustion. This research was motivated by the desire to eliminate the use of pyrophoric or toxic ignition and/or combustion enhancement materials in operational aircraft or shipboard systems. The total temperatures and torch powers used to ignite/flamehold Mach 2 combustion with hydrogen, ethylene, ethane, and methane were determined. The minimum ignition total temperatures for the fuels tested were hydrogen - 1065 R (lowest test temperature); ethylene - 1500 R; ethane - 2000 R; methane - 2700 R. These temperatures were obtained while operating the torch at a nominal 2 kw net power. The torch was shown to be a good ignitor and flameholder in that both hydrogen and hydrocarbon fuels could be stabilized by the torch and would 'blow off' when the torch was extinguished. The effectiveness of the torch was very sensitive to relative fuel injection location. Best combustion resulted when fuel was injected both upstream and downstream of the torch. These results indicated that an adiabatic plasma torch operating at about 2 kw could be an effective ignitor and flameholder for high-speed combustion.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 84-1408
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  • 6
    Publication Date: 2017-06-27
    Description: Microwave techniques for measurement of solid rocket propellant burning rates
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-66627
    Format: application/pdf
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  • 7
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 3; 157-163
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  • 8
    Publication Date: 2019-07-12
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 1; 464-469
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  • 9
    Publication Date: 2019-07-13
    Description: The detailed unsteady pressure field produced on the rotor blades of an axial-flow fan by interaction with downstream struts was investigated. The experimental arrangement was similar to that found in the fan casings of turbofan aircraft engines. Acoustically significant pressure fluctuations were measured on both thy suction and pressure sides of the rotor blades for several positions of the downstream struts. The level of the observed interaction decreased with increased spacing of the struts behind the rotor. An inviscid flow analysis for the disturbance level is compared with trends of the measured results.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 83-0682 , American Institute of Aeronautics and Astronautics, Aeroacoustics Conference; Apr. 11-13, 1983; Atlanta, GA
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