Detection of Separation Bubbles by Infrared Images in Transonic Turbine Cascades

[+] Author and Article Information
W. Bräunling

DFVLR, Institute for Experimental Fluid Mechanics, Göttingen, Federal Republic of Germany

A. Quast

DFVLR, Institute for Design Aerodynamics, Braunschweig, Federal Republic of Germany

H.-J. Dietrichs

Motoren und Turbinen Union München GmbH, Munich, Federal Republic of Germany

J. Turbomach 110(4), 504-511 (Oct 01, 1988) (8 pages) doi:10.1115/1.3262224 History: Received October 01, 1987; Online November 09, 2009


In a test facility for straight cascades, equipped with profiles designed for a highly loaded gas turbine rotor of a high-pressure stage, experiments were conducted to clarify some effects of shock wave–boundary layer interactions. The specific aim was to determine both the position and strength of compression shocks originating from profile wake flows and the position and extent of separation bubbles. The latter are most often detected by visualization methods like surface oil flow patterns or Schlieren photographs, as well as by typical properties in wall pressure distribution curves. In addition, the infrared image technique, which has found many applications in a wide range of technical activities in the recent years, may also be used. Compared with other methods, this technique has distinct advantages in fluid mechanics applications. The whole model can be observed without disturbing the boundary layer by tappings, measuring materials, or probes. Some typical infrared images are presented and interpreted using results of pressure distribution measurements, hot-film measurements, and surface oil flow visualizations.

Copyright © 1988 by ASME
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