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  • 1
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    An experimental investigation of rubbing interaction in labyrinth seals at cryogenic temperature (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An experimental program was carried out to address issues related to the observed cracking of the titanium knife edges on the labyrinth seals of the high pressure fuel pump (HPFP) in the Space Shuttle main engine (SSME). Thermal shock experiments were carried out using a jet specimen with geometry similar to the knife edge geometry. These tests demonstrate that cracking of the titanium alloy is possible in a situation involving repeated thermal cycles over a wide temperature range, as might be realized during a rub in the liquid hydrogen fuel pump. High speed rub interaction tests were conducted using a representative knife edge and seal geometry over a broad range of interaction rates. Alternative materials were also experimentally evaluated. These tests provide information which can be used to design improved labyrinth seals for the HPFP of the SSME. In particular, plasma-sprayed aluminum-graphite was found to be significantly better than aluminum alloy seals used at present from the standpoint of rub performance. Ion nitriding of the titanium alloy knife edges was also found to improve rub performance compared with the untreated baseline knife edge material.
    Keywords: MECHANICAL ENGINEERING
    Type: Wear (ISSN 0043-1648); 102; 51-66
    Format: text
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  • 2
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    Design, development, and test of a laser velocimeter for a small 8:1 pressure ratio centrifugal compressor (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The instrument was designed as a diagnostic tool for the basic fluid dynamics of the inducer, impeller, and diffuser regions of this type compressor. The LV instrumentation was optimized to measure instantaneous velocities up to approximately 500 m/s, measured in absolute coordinates, within the rotating compressor impeller and in the two dimensional radial plane of the diffuser. Some measurements were made within the diffuser and the impeller inlet flows; however, attempts to make detailed measurements of the velocity field were not successful. Difficulties in maintaining high seed particle rates within the probe volume and the improper operation of the blade gating optics may explain the lack of success. Recommendations are made to further pursue these problems. At 100% speed the stage attained a total static pressure ratio of 7.5:1 at 75% total-static efficiency. Flow range from choke-to-surge was 6.8% of choking mass flow rate. Performance was lower than the design intent of 8:1 pressure ratio at 77% efficiency and 12% flow range. Detailed measurements of the stage components are presented which show the reasons for the stage performance deficiencies.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-134781 , CREARE-TN-289
    Format: application/pdf
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  • 3
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    Analytical and experimental investigation of rubbing interaction in labyrinth seals for a liquid hydrogen fuel pump (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Cracking of the titanium knife edges on the labyrinth seals of the liquid hydrogen fuel pump in the Space Shuttle main engine is considered. Finite element analysis of the thermal response of the knife edge in sliding contact with the wear ring surface shows that interfacial temperatures can be quite high and they are significantly influenced by the thermal conductivity of the surfaces in rubbing contact. Thermal shock experiments on a test specimen similar to the knife edge geometry demonstrate that cracking of the titanium alloy is possible in a situation involving repeated thermal cycles over a wide temperature range, as might be realized during a rub in the liquid hydrogen fuel pump. High-speed rub interaction tests were conducted using a representative knife edge and seal geometry over a broad range of interaction rates and alternate materials were experimentally evaluated. Plasma-sprayed aluminum-graphite was found to be significantly better than presently used aluminum alloy seals from the standpoint of rub performance. Ion nitriding the titanium alloy knife-edges also improved rub performance compared to the untreated baseline.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-174657 , NAS 1.26:174657 , CREARE-TN-371
    Format: application/pdf
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  • 4
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    Design, development, and test of a laser velocimeter for high speed turbomachinery (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper describes the design, development, and test of a laser Doppler velocimeter (LDV) to map the velocity fields in a small, high speed, 8:1 pressure ratio, 0.91 kg/s (2 lbm/s), centrifugal compressor. This instrument is being used as a diagnostic tool for the study of the basic fluid dynamics of the inducer, impeller and the diffuser regions of high pressure ratio, small, centrifugal compressors. The LDV instrumentation has been optimized to permit the measurement of instantaneous velocities up to approximately 500 m/s, measured in absolute coordinates, within a rotating compressor impeller. Velocities of the same magnitude can also be measured in the two-dimensional radial plane of the diffuser. It is shown that LDV can make nondisturbing gas velocity measurements and surmount the difficulties found in applying other types of aerodynamic instrumentation to this measurement problem.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: The accuracy of flow measurements by laser Doppler methods; Aug 25, 1975 - Aug 28, 1975; Copenhagen; Denmark
    Format: text
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  • 5
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    Pressure recovery performance of conical diffusers at high subsonic Mach numbers (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The pressure recovery performance of conical diffusers has been measured for a wide range of geometries and inlet flow conditions. The approximate level and location (in terms of diffuser geometry of optimum performance were determined. Throat Mach numbers from low subsonic (m sub t equals 0.2) through choking (m sub t equals 1.0) were investigated in combination with throat blockage from 0.03 to 0.12. For fixed Mach number, performance was measured over a fourfold range of inlet Reynolds number. Maps of pressure recovery are presented as a function of diffuser geometry for fixed sets of inlet conditions. The influence of inlet blockage, throat Mach number, and inlet Reynolds number is discussed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2299 , TN-165
    Format: application/pdf
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  • 6
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    Flight Test Results for the NICMOS Cryocooler (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In October 1998 a mechanical cryocooler and cryogenic circulator loop were flown on NASA's STS-95 as part of the Hubble Orbital System Test (HOST). The system will be installed on the Hubble Space Telescope (HST) during Service Mission #3 in 2000 and will provide cooling to the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). It will extend the useful life of that instrument by 5 to 10 years. This was the first successful space demonstration of a turbobrayton cryocooler. The cooler is a single stage reverse Brayton type, using low-vibration high-speed miniature turbomachines for the compression and expansion functions. A miniature centrifugal cryogenic circulator is used to deliver refrigerated neon to the instrument. During the mission, the cooler operated without anomalies for approximately 185 hours over a range of conditions to verify its mechanical, thermodynamic and control functions. The cryocooler satisfied all mission objectives including maximum cooldown to near-design operating conditions, warm and cold starts and stops, operation at near-design temperatures, and demonstration of long-term temperature stability. This paper presents a description of the cooler and its operation during the HOST flight.
    Keywords: Engineering (General)
    Type: TN-602 , Cryogenic Engineering; Jul 01, 1999; Montreal; Canada
    Format: text
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  • 7
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    A laser velocimeter system for small radial turbomachinery (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper describes the design and test of a laser Doppler velocimeter (LDV) to map the velocity fields in small high-speed turbomachinery. This instrument is presently being used as a diagnostic tool for the study of the basic fluid dynamics of the inducer, impeller and the diffuser regions of high-pressure-ratio small centrifugal compressors. The LDV instrumentation has been optimized to permit measurement of instantaneous velocities up to approximately 500 m/s within a rotating impeller. It is shown that LDV can make nondisturbing gas velocity measurements and surmount the difficulties found in applying other types of aerodynamic instrumentation, e.g., hot-wire anemometers, to this measurement problem.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: SQUID Workshop on Transonic Flow Problems in Turbomachinery; Feb 11, 1976 - Feb 13, 1976; Monterey, CA
    Format: text
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