Project Title:

Simultaneous Temperature, Density, and Flow Diagnostics for Aeropropulsion Systems

01.03-1520
Simultaneous Temperature, Density, and Flow
	Diagnostics for Aeropropulsion Systems
Deacon Research 
900 Welch Road, Suite 203
Palo Alto, CA 94304
Anthony O'Keefe  (415-326-1520)
LeRC -- NAS3-25401

Abstract:

	 The design of advanced propulsion systems requires simultaneous measurement of
the flow velocities and the thermodynamic properties in order to verify the mathematical
models based on the time-averaged, Navier-Stokes equations. The coherent anti-Stokes
Raman scattering (CARS) technique makes possible the measurement of the temperature
and pressure but not velocity. Laser Doppler velocimeters fail at high velocities
because the measured dust particles no longer follow the flow lines. The innovation
is in combining CARS with a well-known spectroscopic technique, stimulated Brillouin
scattering (SBS), which can measure flow velocity from subsonic through hypersonic
speeds. By adding a detection system and changing the CARS geometry slightly, one
can measure the flow velocity, temperature, and density with a single, stop-motion
laser pulse.The Phase I investigation showed that an SBS system can be configured
to measure velocities in the range of Mach 0 to 20 and above with an accuracy of
Mach 0.02, expanding, thereby, the range of velocity measurements more than an order
of magnitude. An SBS technique can also be coupled with a CARS measurement of the
temperature and density so that the three critical variables of the Navier-Stokes
equations can be measured independently within 100 ns of each other.

Potential Commercial Application:

Potential Commercial Application: An SBS velocimeter could find applications not
only at ground-based testing facilities but also in flight testing, where the SBS
configuration makes these simultaneous flow and thermodynamic measurements possible
for the first time.