Visualization of Pulsed Vortex Generator Jets

Abstract

This work highlights the use of porous pressure-sensitive paint (PSP) as a visualization tool for unsteady flows in turbomachinery.  Surface pressure measurements on turbomachinery components with semiconductor sensors or pressure taps are limited by sparse spatial resolution and complex installation. As a result, resolving high-frequency pressure fluctuations in unsteady flows has proven to be difficult.  Recent advancements in the development of porous pressure-sensitive paint (PSP) have enabled unsteady surface pressure measurements at frequencies of at least 20 kHz with very fine spatial resolution. Conventional PSP formulas use a polymer binder which results in a response time of several seconds; however, response characteristics have recently been improved by the formulation of a porous matrix binder.  Dynamic response calibrations are presented, and the application of PSP to a low pressure turbine blade is discussed. In particular, PSP is used to visualize the unsteady behavior of a spanwise row of vortex generator jets (VGJs) on an L1A low-pressure turbine blade placed in a cascade wind tunnel. The blade was painted with polymer/ceramic PSP (PC-PSP), and the VGJs were pulsed at 10.6 Hz with nitrogen. Intensity-based, time-resolved PSP measurements reveal the development and structure of the VGJs.