Nonintrusive Measurement of Gas Turbine Exhaust Velocity Using Hydroxyl Tagging Velocimetry

The Hydroxyl Tagging Velocimetry (HTV) technique has been applied to the measurement of engine exhaust velocities for an aviation gas turbine engine with augmentor capabilities. The J85-GE-5 engine exhaust was measured to be 110 m/s at idle and ramping up to 540 m/s at full throttle conditions. This information can be useful for the development of a noncontact thrust measurement system, which would rely on fluid flow measurements, rather than the use of load cells, to infer engine thrust. For the augmented (afterburner) mode of operation, the HTV tag lines were not present in the camera field of view; instead, there was significant fluorescence indicating turbulent mixing between fluorescing and nonfluorescing flow regions. The tag line absorption and concomitant exhaust gas fluorescence is probably a result of unreacted kerosene vapor exiting the afterburning gas turbine engine. Although this prevents the HTV technique from being applied to the afterburning engine, it can provide useful information about the instantaneous spatial distribution of fuel in the engine exhaust, and this information could be used to understand the processes occurring inside the engine in regards to its augmented operation.