Year of Publication

2003

Degree Name

Master of Science (MS)

Document Type

Thesis

College

Engineering

Department

Mechanical Engineering

First Advisor

Dr. Jamey D. Jacob

Abstract

The flow field around a low pressure turbine blade is examined using smoke-wire flow visualization, static surface pressure measurements, and particle image velocimetry (PIV). The purpose of the experimental study is to investigate the transition and separation characteristics on low pressure turbine blades under low Reynolds number (Re) and varying freestream turbulence intensity (FSTI). A cascade model consisting of 6 Pratt andamp; Whitney PAK-B low pressure turbine blades was examined in a wind tunnel using PIV and flow visualization. Smoke-wire visualization was performed for test section exit angles of 93°, 95°, and 97°, in the range Re = 3 · 104 to 9 · 104 and three levels of FSTI varied with a passive grid. The locations of separation and transition were determined to be approximately 45% and 77% of the suction surface length, respectively, based upon the smoke stream lines observed in the images, and appear to be independent of Re, turning angle, and FSTI. The maximum size of the separation bubble was found to decrease with increasing Re, turning angle, and FSTI. PIV images from three camera views were processed for an exit angle of 95° and a Re range of 3:0 · 104 to 30:0 · 104 and three levels of FSTI. Velocity, vorticity, and reversed flow probability field plots were generated along with velocity, vorticity, and RMS velocity profiles. The point of separation point was determined to be from 63% SSL to 67% SSL. The area of reversed flow was computed for each image pair from camera views 1 and 3, as an approxiamtion of the relative size of the separation region. For low Re and FSTI cases the area was much larger than for higher FSTI cases at any Re. The raw PIV images include some of the rst clear pictures of the turbulent flow structures forming in the unsteady shear layer over the suction surface of low pressure turbine blades. Several movies are compiled that show how the geometry and location of the shear layer evolve in time for a given set of flow conditions.

APS-Med.mov (19972 kB)
piv1_50_15.AVI (6275 kB)
piv1_50_75.AVI (6587 kB)
piv1_50_CLN.AVI (11432 kB)
smoke30_95.avi (989 kB)
smoke50_95.avi (674 kB)
smoke60_95.avi (793 kB)
smoke70_95.avi (827 kB)
smoke80_95.avi (582 kB)
smoke90_95.avi (586 kB)

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