UK Fluids Lab

Turbine Blade Separation

The goal of this work is to obtain high quality data of turbine blade separation useful for validation of numerical models as well as to learn more about the physics behind separation and transition in a turbine cascade.

The wind tunnel cascade of 6 P&W Pak-B blades is used for both flow vis. and PIV.

The flow field around a low pressure turbine blade is examined using smoke-wire flow visualization, pressure measurements, and PIV. The purpose of the experimental study is to investigate the detailed transition and separation characteristics on low pressure turbine blades under low Re and varying FSTI.

Two smoke wire flow vis runs for two different exit angles: 97 and 93 degrees, respectively at Re=60,000.

A cascade model consisting of 6 low pressure turbine blades was inv estigated in a wind tunnel using PIV and flow visualization. Smoke-wire visualiz ation was performed for test section exit angles of 93, 95, and 97 degrees, in the range Re=30,000 to 90,000 and FSTI of 0.5% to 10%. The locations of separation and transition were determined to be approximately 45% and 77% of the suction surface length, respectively, based upon the smoke streamlines observed in the images, and appear to be independ ent of Re, turning angle, and free-stream turbulence intensity. The maximum size of the separation bubble was found to decrease with increasing Re, turning angle, and free-stream turbulence intensity.

Smoke wire flow vis. revealing separation and transition locations.

PIV images from three camera views were processed for an exit angle of 95 degrees and a Re range of 30,000 to 300,000 and a FSTI of 0.5%,, 5%, and 10%. Velocity, vorticity, and r eversed flow probability field plots were generated along with velocity, vortici ty, and RMS velocity profiles.

Vorticity profiles from PIV showing the outward advection of the separated region progressing downstream.

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 2 and 3. For low Re and FSTI cases the area was much larger than for higher FSTI cases at any Re.

Revers flow probability showing separation from a PIV run.

The location of the onset of transition can be nicely illustrated with raw PIV images.



Turbine Blade Separation		Turbine Blade Separation The goal of this work is to obtain high quality data of turbine blade separation useful for validation of numerical models as well as to learn more about the physics behind separation and transition in a turbine cascade. The wind tunnel cascade of 6 P&W Pak-B blades is used for both flow vis. and PIV. The flow field around a low pressure turbine blade is examined using smoke-wire flow visualization, pressure measurements, and PIV. The purpose of the experimental study is to investigate the detailed transition and separation characteristics on low pressure turbine blades under low Re and varying FSTI. Two smoke wire flow vis runs for two different exit angles: 97 and 93 degrees, respectively at Re=60,000. A cascade model consisting of 6 low pressure turbine blades was inv estigated in a wind tunnel using PIV and flow visualization. Smoke-wire visualiz ation was performed for test section exit angles of 93, 95, and 97 degrees, in the range Re=30,000 to 90,000 and FSTI of 0.5% to 10%. The locations of separation and transition were determined to be approximately 45% and 77% of the suction surface length, respectively, based upon the smoke streamlines observed in the images, and appear to be independ ent of Re, turning angle, and free-stream turbulence intensity. The maximum size of the separation bubble was found to decrease with increasing Re, turning angle, and free-stream turbulence intensity. Smoke wire flow vis. revealing separation and transition locations. PIV images from three camera views were processed for an exit angle of 95 degrees and a Re range of 30,000 to 300,000 and a FSTI of 0.5%,, 5%, and 10%. Velocity, vorticity, and r eversed flow probability field plots were generated along with velocity, vortici ty, and RMS velocity profiles. Vorticity profiles from PIV showing the outward advection of the separated region progressing downstream. 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 2 and 3. For low Re and FSTI cases the area was much larger than for higher FSTI cases at any Re. Revers flow probability showing separation from a PIV run. The location of the onset of transition can be nicely illustrated with raw PIV images. One image in the region of separation - the separated bubble is clearly visible from the smoke droplets. One image in the region of transition - note the rollup of the shear layer; this region exhibits strong transient behavior with distinct structures. Some movies from the raw PIV data are also available (AVI format). These show in detail formation and advection of vortex structures in the separated region for 3 different levels of FSTI. Also note that the height of the separated region fluctuates greatly but the location of separation does not vary. All cases are Re=50,000 near region of separation (~50% SSL). Movie 1: 1_50_CLN.AVI 0.5% FSTI (11.1 MB) Movie 2: 1_50_15.AVI ~5% FSTI (6.4 MB) Movie 3: 1_50_75.AVI ~10% FSTI (6.1 MB)