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  • Other Sources  (14)
  • 1980-1984  (10)
  • 1975-1979  (4)
  • 1
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    Prediction of force coefficients for labyrinth seals (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The development of a linear model for the prediction of labyrinth seal forces and on its comparison to available stiffness data is presented. A discussion of the relevance of fluid damping forces and the preliminary stages of a program to obtain data on these forces are examined. Fluid-dynamic forces arising from nonuniform pressure patterns in labyrinth seal glands are known to be potentially destablizing in high power turbomachinery. A well documented case in point is that of the space Shuttle Main Engine turbopumps. Seal forces are also an important factor for the stability of shrouded turbines, acting in that case in conjunction with the effects of blade-tip clearance variations.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 235-256
    Format: application/pdf
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  • 2
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    Dynamics of drive systems for wind energy conversion (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Calculations are performed to determine the dynamic effects of mechanical power transmission from the nacelle of a horizontal axis wind machine to the ground or to an intermediate level. It is found that resonances are likely at 2 or 4/REV, but they occur at low power only, and seem easily correctable. Large reductions are found in the harmonic torque inputs to the generator at powers near rated.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Res. Center Wind Turbine Structural Dyn.; p 187-193
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  • 3
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    Prediction of low frequency and impulsive sound radiation from horizontal axis wind turbines (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Theoretical models to predict the radiation of low frequency and impulsive sound from horizontal axis wind turbines due to three sources: (1) steady blade loads; (2) unsteady blade loads due to operation in a ground shear; (3) unsteady loads felt by the blades as they cross the tower wake. These models are then used to predict the acoustic output of MOD-1, the large wind turbine operated near Boone, N.C. Predicted acoustic time signals are compared to those actually measured near MOD-1 and good agreement is obtained.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center Wind Turbine Dyn.; p 401-409
    Format: application/pdf
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  • 4
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    Analytical model of the structureborne interior noise induced by a propeller wake (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The structure-borne contribution to the interior noise that is induced by the propeller wake acting on the wing was studied. Analytical models were developed to describe each aspect of this path including the excitation loads, the wing and fuselage structures, and the interior acoustic space. The emphasis is on examining a variety of parameters, and as a result different models were developed to examine specific parameters. The excitation loading on the wing by the propeller wake is modeled by a distribution of rotating potential vortices whose strength is related to the thrust per blade. The response of the wing to this loading is examined using beam models. A model of a beam structurally connected to a cylindrical shell with an internal acoustic fluid was developed to examine the coupling of energy from the wing to the interior space. The model of the acoustic space allows for arbitrary end conditions (e.g., rigid or vibrating end caps). Calculations are presented using these models to compare with a laboratory test configuration as well as for parameters of a prop-fan aircraft.
    Keywords: ACOUSTICS
    Type: NASA-CR-172381 , NAS 1.26:172381
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  • 5
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    Advanced LOX/H2 engine technologies for future OTVs (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is pointed out that NASA and DOD missions of the near future include, by current estimates, approximately 50 highly energetic missions to geosynchronous orbit. Advanced concepts make use of the Space Shuttle to transport the assembled orbital transfer vehicle (OTV) to low earth orbit (LEO) or to bring components and propellants from which to assemble the OTV in LEO. An advanced expander cycle engine based upon the RS-44 engine design has been planned for ultimate use with advanced space-based OTVs. Its design features complement the characteristics of manned space-based aeroassist vehicles which will provide the most cost-effective means for payload transfer between LEO and GEO orbits. A test-bed program is planned for early demonstration of the advanced expander cycle engine operation.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 83-1312
    Format: text
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  • 6
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    Aerodynamic theory for wing with side edge passing subsonically through a gust (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An approximate solution for the unsteady loading near the square-shape tip of a wing passing through an oblique gust is obtained in closed form. The aerodynamic theory developed can be used to predict airloads felt by a helicopter blade experiencing a blade/vortex interaction for high blade tip speed and/or for small vertical blade/vortex separation. Under these conditions one can show that the blade's trailing edge has little influence on the character of the chordwise loading at all spanwise sections; thus, the chord may be allowed to extend to infinity in the downstream direction. Therefore, the model considered here is that of a quarter-infinite flat plate wing with side edge passing subsonically through an oblique gust.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; June 198
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  • 7
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    Unified aerodynamic-acoustic theory for a thin rectangular wing encountering a gust (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A linear aerodynamic-acoustic theory is developed for the prediction of the surface pressure distribution and three-dimensional acoustic far-field for a flat plate rectangular wing encountering a stationary short-wavelength oblique gust. It is suggested that for an infinite-span wing, leading- and trailing-edge responses to a short-wavelength gust are essentially independent. This idea is used to solve for the two-dimensional pressure field due to the passage of an infinite-span wing through an oblique gust. By allowing the field point to come down to the wing's surface, one finds an expression for the surface pressure distribution which agrees with that given in the two-dimensional aerodynamic theories of Amiet and Adamczyk. Spanwise Fourier superposition of two-dimensional solutions to the infinite-span wing problem is used to approximate the three-dimensional acoustic field due to the interaction of a stationary oblique gust with a flat-plate rectangular wing traveling at a subsonic speed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 18; June 198
    Format: text
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  • 8
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    An aeroacoustic model for high-speed, unsteady blade-vortex interaction (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A three-dimensional aeroacoustic model is developed to predict the sound pulse radiated by the passage of a helicopter blade over a potential vortex. The linearized analysis assumes that either the blade-vortex separation is small or that the blade-tip Mach number is close to 1, or both, so that an acoustically noncompact situation exists. The three-dimensional blade loading due to blade-vortex interaction is constructed through a spanwise superposition of two-dimensional solutions with strength linearly increasing from hub to tip. Such a loading overestimates somewhat the strength of tip region dipoles in the acoustic calculation that follows. The final expression for the predicted far-field signature is obtained in closed form, and thus permits a relatively inexpensive calculation of the directivity of peak acoustic pressures in three dimensions.
    Keywords: ACOUSTICS
    Type: AIAA Journal (ISSN 0001-1452); 21; Sept
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  • 9
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    Linear rocket engines for advanced space transportation systems (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The linear rocket engine is shown to be a viable candidate propulsion system for post-Space Shuttle single-stage-to-orbit systems. The linear engine system has been developed and fired demonstrating high performance and long life with firing durations exceeding 500 seconds. The application of the split or dual combustor to the linear engine permits the uses of two different propellant combinations in a single engine system. The split combustor possesses the advantages of the two position extendible bell nozzle in a fixed nozzle configuration. Engine power cycles and applications to typical vehicles are discussed.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 75-1251
    Format: text
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  • 10
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    The use of tethers for payload orbital transfer. Continuation of investigation of electrodynamic stabilization and control of long orbiting tethers, volume 2 (1982)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The SKYHOOK program was used to do simulations of two cases of the use of the tether for payload orbital transfer. The transport of a payload along the tether from a heavy lower platform to an upper launching platform is considered. A numerical example of the Shuttle launching a payload using an orbital tether facility is described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-162035 , NAS 1.26:162035
    Format: application/pdf
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