An investigation of axial turbomachinery flow using PIV in an optically-unobstructed facility

Y-C Chow, O. Uzol, J. Katz & C. Meneveau
Department of Mechanical Engineering
Johns Hopkins University
Baltimore, MD 21218

ABSTRACT: Particle Image Velocimetry (PIV) is a powerful flow diagnostics tool but it requires optical access for the laser sheet and the camera. In turbomachines, such an access is frequently limited by the number of the blades (and blade rows) and their shapes. In this paper we introduce a two-stage axial turbomachine facility that has been developed to overcome this problem. Using a concentrated solution of Sodium Iodide and water (62% in weight) as the working fluid, we match the refractive index of this fluid with that of the transparent acrylic rotor and stator blades. Therefore the laser sheet is able to pass through multiple blade rows without being blocked or distorted, illuminating the seeded sample area anywhere in the entire rotor and stator passages. The illuminated plane can also be seen unobstructed by the digital camera. Results of measurements performed at 500 rpm and at a Reynolds number of 370,000 (based on the tip speed and rotor blade chord length) are presented. The experiments cover an entire stage, including the flow around the rotor, the stator and the gap between them. Distributions of phase-averaged mean velocity and turbulence parameters are obtained at different rotor orientations relative to the stator blade. The flow is dominated by unsteady interactions of wakes and non-uniform flow field generated by a blade row with the blades located downstream. In fact, it is possible to detect not only the effect of the adjacent previous row, but also the effect of the previous two rows. For example, substantial phase-dependent changes to the magnitude and angle of the velocity field at the inlet to the stator blade cause significant variations in the flow around the stator blade. “Chopping”, “shearing” and transport of the stator and rotor wakes are also visualized.

'The 9th of International Symposium on Transport Phenomena and Dynamics of Rotating Machinery' Honolulu, Hawaii, February 10-14, 2002.

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