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  • AIRCRAFT PROPULSION AND POWER  (2)
  • Polymer and Materials Science  (2)
  • J15
  • 1985-1989  (4)
  • 1
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    Vortex shedding in compressor blade wakes (1987)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The wakes of highly loaded axial compressor blades were often considered to be turbulent, unstructured flows. Recent work has suggested that the blade wakes are in fact dominated by a vortex street-like structure. The work on the wake structure at MIT is reviewed, the results of a viscous numerical simulation are presented, the blade wake vortices are compared to those shed from a cylinder, and the implications of the wake structure on compressor performance are discussed. In particular, a two-dimensional, time accurate, viscous calculation shows both a periodic wake structure and time variations in the passage shock strength. The numerical calculations are compared to laser anemometer and high frequency response probe data. The effect of the wake structure on the entropy production and apparent adiabatic efficiency of the compressor rotor is discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AGARD Transonic and Supersonic Phenomena in Turbomachines; 13 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Unsteady design-point flow phenomena in transonic compressors (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: High-frequency response probes which had previously been used exclusively in the MIT Blowndown Facility were successfully employed in two conventional steady state axial flow compressor facilities to investigate the unsteady flowfields of highly loaded transonic compressors at design point operation. Laser anemometry measurements taken simultaneously with the high response data were also analyzed. The time averaged high response data of static and total pressure agreed quite well with the conventional steady state instrumentation except for flow angle which showed a large spread in values at all radii regardless of the type of instrumentation used. In addition, the time resolved measurements confirmed earlier test results obtained in the MIT Blowdown Facility for the same compressor. The results of these tests have further revealed that the flowfields of highly loaded transonic compressors are heavily influenced by unsteady flow phenomena. The high response measurements exhibited large variations in the blade to blade flow and in the blade passage flow. The observed unsteadiness in the blade wakes is explained in terms of the rotor blades' shed vorticity in periodic vortex streets. The wakes were modeled as two-dimensional vortex streets with finite size cores. The model fit the data quite well as it was able to reproduce the average wake shape and bi-modal probability density distributions seen in the laser anemometry data. The presence of vortex streets in the blade wakes also explains the large blade to blade fluctuations seen by the high response probes which is simply due to the intermittent sampling of the vortex street as it is swept past a stationary probe.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-176879 , NAS 1.26:176879
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
    Electronic Resource
    Electronic Resource
    Cellulose hydrolysis after combined action of high pressure and shear deformation (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 677-687 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070340221
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Brain biocompatibility of a biodegradable, controlled-release polymer in rats (1989)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 253-266 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We report the biocompatibility in the rat brain of a controlled-release, biodegradable polymer, the polyanhydride poly-[bis(p-carboxyphenoxy)propane-sebacic acid] copolymer (PCPP-SA) in a 20:80 formulation. The biodegradable polyanhydride can be used for drug delivery directly into the brain, circumventing the difficulties posed by the blood - brain barrier and avoiding the consequences of having to administer toxic doses systemically to reach therapeutic doses in the central nervous system. The tissue reaction in the presence of PCPP-SA was compared to that seen with other standard neurosurgical implants. Fifty-six adult Sprague-Dawley rats were assigned to one of seven groups and underwent bilateral frontal lobe implantation of PCPP-SA (42 hemispheres), Surgicel (oxidized regenerated cellulose) (35 hemispheres), or Gelfoam (absorbable gelatin sponge) (35 hemispheres). None of the animals showed any behavioral changes or neurological deficits suggestive of either systemic or localized toxicity from the biodegradable polyanhydride, all surviving to the scheduled data of sacrifice. PCPP-SA evoked a well localized inflammatory reaction, comparable to that of Surgicel, which resolved as the PCPP-SA polymer degraded over five weeks. The biodegradable polyanhydride has been shown in this study to be nontoxic and biocompatible in the rat brain, when compared to standard neurosurgical implants.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820230209
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    Paper (German National Licenses)
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