Fluorescent Tracer Particles For PIV Measurement In Gas Flows
M. Okada, J. Pinho, S. Lavagnoli
Turbomachinery and Propulsion Dept., von Karman Institute for Fluid Dynamics, Belgium
This paper presents the development and employment of fluorescent tracer particles which allow removal of undesired strong light reflections in gas-phase Particle Image Velocimetry measurements. A spectroscopic investigation on fluorescent dye-doped solutions at different concentrations provided fluorescent emission spectra ranging their peak between 540 and 585 nm when excited by 527 nm wavelength Nd:YLF laser. The fluorescence intensity of the solutions in a form of sub-micron droplet was examined through comparison of statistical pixel intensities of raw particle images. Within the investigated concentration range, the intensity was found to be almost proportional to the dye concentration. The developed particle was tested in a wind tunnel at 5 m/s mean flow speed with a metal turbine blade placed in the channel and laser sheet oriented to impinge the blade surface. With the employment of an adequate optical band-stop filter, the undesired light reflections were successfully removed and reasonable vector calculations were enabled in proximity to the reflective surfaces. Lastly, the fluorescent PIV was performed in a high-speed short-duration rotating turbine test rig in order to demonstrate the effectiveness of the technique in industrial or extreme applications comprise severe conditions.