Hydroxyl tagging velocimetry (HTV) in highly accelerated flows

Abstract

MECHANICAL ENGINEERING

HYDROXYL TAGGING VELOCIMETRY (HTV) IN HIGHLY ACCELERATED FLOWS

AMBER PERKINS

Thesis under the direction of Professor Robert Pitz Hydroxyl tagging velocimetry (HTV) is applied to evaluate its use in propulsion test flows. In HTV, an 11x11 grid of OH molecules is formed by dissociating H2O in the flow with an ArF excimer laser at 193 nm. The OH grid is tracked over a fixed time interval with laser-induced fluorescence to determine the 2D velocity in the plane of the grid by time-of-flight displacement. In a turbojet test engine facility, a dual-pulse imaging technique determines centerline velocities in the J85 jet engine exhaust that range from 76 m/s to 580 m/s at low to full throttle. In a dual-pulse imaging method, the undisplaced and displaced images are taken in quick succession and the effects of engine vibrations are eliminated resulting in reduced velocity uncertainty. The HTV method is also applied to a shock tube test facility where the vibrations are low and a single-image method can be used. The induced velocity in the gas behind the transient shock wave creates steady-state test flow of up to 1690 m/s for a short period. Two configurations are studied: a detached shock wave formed over an axisymmetric blunt body and an attached shock wave formed on an axisymmetric cone. HTV is used to measure the freestream velocity of the transient shock induced flow and the resulting velocity field behind the shock waves. The results of the shock tube experiment demonstrate the use of the HTV method in a high-speed flow using a grid that provides 2D velocity data.