Instrumentation to Support PIV and HPIV Measurements in an Axial Turbomachine Flow Visualization Facility

Abstract

Abstract : This DURIP grant has provided instrumentation that supports an AFOSR sponsored program. The objective of this program is to measure the unsteady flow in axial turbomachines and use the data to address turbulence and flow modeling issues that are specific to such complex environments. The motivation is to examine turbulence and unsteady flow phenomena at three levels of modeling: passage-averaged, steady RANS, unsteady RANS, and subgrid scale stress modeling for LES. The report describes in detail our unique two-stage axial-turbomachine flow visualization facility, specifying the instruments purchased under the resent grant and how they fit into the system. This facility contains fluid (concentrated solution of NaI in water with an optical index of refraction that matches that of the acrylic blades of the second stage. Consequently, it allows unobstructed view on an entire stage including the rotor, stator and the gas between blade rows. Two and three dimensional velocity measurement can be performed using 2-D Particle Image Velocimetry, planar 3-D measurements using stereo-IV and full 3-D HPIV. The report also describes current 2-D PIV measurements and presents sample data. With available access to any desired plane, these measurements provide data on rotor-stator interactions, the effects of wakes on downstream blades, tip leakage flows and hub vortices and their interactions with neighboring blades, unsteady separation, particularly off-design conditions, etc.