Three-Component Planar Doppler Velocimetry Measurements in a Full-Scale Aircraft Exhaust

A diagnostic system will be developed and demonstrated for measuring three-component velocities in a planar measurement region in the exhaust plume of a full-scale aircraft turbine engine. The method, known as Planar Doppler Velocimetry (PDV), does not require seeding of the flow and involves measuring the Doppler shift of laser light scattered from soot and/or dust particles naturally present in a typical aircraft exhaust. An iodine cell filter is used to spectrally discriminate the scattered light based on the Doppler shift. In prior work, the technique was developed for a subscale turbojet engine, resulting in the demonstration of three-component velocity measurements in the exhaust plume that were in good agreement with conventional Pitot probe measurements of the same flow. The proposed effort will extend the technique for use on a larger engine, culminating with a demonstration of three-component spatially resolved velocity measurements on a full-scale fighter jet engine. The proposed work will harden the system to isolate the sensitive components from engine vibrations, and will optimize the image processing software to produce a widely applicable user-friendly measurement system.