A fluorescent PIV technique for turbomachinery flows

Abstract

This paper presents the development and applications of a fluorescent Particle Image Velocimetry (PIV) technique as a countermeasure for undesired light reflections on surfaces of channel walls or obstacles. The employment of the fluorescent dye-doped tracer particle with a wavelength-specific optical filter enables a separation of the stokes-shifted particle light emission from reflections on the surfaces. Aiming at applying the technique to engine-like turbomachinery flows, the fluorescent tracer particles were made out of pyrromethene 567 and Di-Ethyl-Hexyl-Sebacat considering multiple aspects of characteristics. The developed particles were firstly tested in a low-speed wind tunnel with a metal turbine blade placed in the flow path and a laser sheet oriented to impinge the blade surface. With the installation of an adequate optical filter, the undesired light reflections were successfully removed, and reasonable vector calculations were enabled in proximity to the reflective blade surfaces. Secondly, the fluorescent PIV was performed on a high-pressure turbine stage hosted in a high-speed short-duration rotating turbine rig to demonstrate the feasibility of the technique in engine-representative turbomachinery flows.