Title page for ETD etd-03122001-155007


Type of Document Master's Thesis
Author Douglas, Justin W
Author's Email Address douglasjw@hotmail.com
URN etd-03122001-155007
Title Effects of Free Stream Turbulence on Compressor Cascade Performance
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Ng, Fai Committee Chair
Dancey, Clinton L. Committee Member
Diller, Thomas E. Committee Member
Li, Shi Ming Committee Member
Keywords
  • Compressor Cascade
  • Anemometer
  • Hotwire
  • Aerodynamic Loss
  • Turbulence Grid
  • Boundary Layer Transition
Date of Defense 2001-03-01
Availability unrestricted
Abstract
The effects of grid generated free-stream turbulence on compressor cascade performance was measured experimentally in the Virginia Tech blow-down wind tunnel. The parameter of key interest was the behavior of the measured total pressure loss coefficient with and without generated free-stream turbulence. A staggered cascade of nine airfoils was tested at a range of Mach numbers between 0.59 and 0.88. The airfoils were tested at both the lowest loss level cascade angle and extreme positive and negative cascade angles about this condition. The cascade was tested in a Reynolds number range based on the chord length of approximately 1.2-2x106. A passive turbulent grid was used as the turbulence-generating device, it produced a turbulent intensity of approximately 1.6%. The total pressure loss coefficient was reduced by 11-56% at both the "lowest loss level" and more positive cascade angles for both high and low Mach numbers. Oil Visualization and blade static pressure measurements were performed in order to gain a qualitative understanding of the loss reduction mechanism. The results indicate that the effectiveness of an increasing turbulent free-stream on loss reduction, at transonic Mach numbers, depends on whether the shock wave on the suction surface is strong enough to completely separate the boundary layer. At negative cascade angles, increasing free-stream turbulence proved to have a negligible influence on the pressure loss coefficient. At cascade angles where transition exists within a laminar separation bubble, increasing free-stream turbulence suppressed the extent of the laminar separation bubble and led to an earlier turbulent reattachment.
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