Laser-Induced Fluorescence Measurements of Velocity in Supersonic Reacting Flowfields
Laser-Induced Fluorescence Measurements of
Velocity in Supersonic Reacting Flowfields
Physical Sciences, Inc.
20 New England Business Center
Andover, MA 01810
Mark G. Allen
This project's approach to non-intrusive velocity measurements in reacting flow
fields is based on the Doppler-shifted fluorescence of the OH radical. It addresses
a critical need in the area of non-intrusive combustion diagnostic measurements and
finds particular application in the design of supersonic ramjet propulsion systems.
The innovation is based on the Doppler-shift of a moving ensemble of molecules relative
to a stationary ensemble. By recording the relative fluorescence profiles of stationary
and moving groups of molecules, the mean velocity component aligned with the laser
beam may be determined. In reacting flows, the radical OH will be distributed over
a large portion of the flow field and is proposed as the fluorescence tracer species.
In flows without chemical reactions, possible tracers include NO seeded into the
flow or O2. This approach circumvents inherent limitations in laser Doppler anemometry
and hot-wire techniques. Preliminary signal estimates with OH show good sensitivity
for velocities as low as 3 X 104 cm/s.
Potential Commercial Application:
Potential Commercial Applications: The proposed technique will find extensive application
throughout the aerospace industry and other industries developing air-breathing propulsion