Experimental Investigation of Trailing Edge Crenulation Effects on Losses in a Compressor Cascade
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF SYSTEMS AND LOGISTICS
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The effects of blade trailing edge crenulations on wake losses in a compressor cascade were investigated at the Air Force Institute of Technology. The cascade used NACA 64-A905 blades with a turning angle of about 30 to model last row stators of an axial flow compressor. Three blade configurations were used unmodified blades, blades with large crenulations, and blades with small crenulations. Wake losses and mixing were evaluated in four flow conditions, generated by combinations of increased freestream turbulence and sidewall boundary layer removal. Injection of air perpendicular to the inlet flow increased freestream turbulence from about 0.15 to about 4. The sidewall boundary layers could be removed by suction through sidewall slots immediately ahead of the cascade. A total pressure rake measured the difference between upstream and downstream total pressure, yielding pressure loss and velocity data, and hot wire anemometry was used downstream from the cascade to measure flow angle, relative turbulence, and velocity. For each test condition, the crenulated blades decreased total pressure loss, the wake velocity deficit, and wake velocity variance by about 10 to 20, while slightly decreasing turning angle and increasing the turbulence level. The size of the crenulations had a small effect on these parameters.
- Fluid Mechanics
- Jet and Gas Turbine Engines