Effects of Free Stream Turbulence on Compressor Cascade Performance

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.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Mechanical Engineering

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2001

Author dc:creator

• Douglas, Justin W.

Chair dc:contributor.committeechair

• Ng, Wing Fai

Committee members dc:contributor.committeemember

• Li, Shi Ming
• Diller, Thomas E.
• Dancey, Clinton L.

• Compressor Cascade
• Anemometer
• Hotwire
• Aerodynamic Loss
• Turbulence Grid
• Boundary Layer Transition

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-03122001-155007

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/31449