Accession Number:

ADA446292

Title:

Spatially-Resolved Temperature Diagnostic for Supersonic Flow Using Cross-Beam Doppler-Limited Laser Saturation Spectroscopy

Descriptive Note:

Master's thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT

Personal Author(s):

Report Date:

2006-03-01

Pagination or Media Count:

185.0

Abstract:

Optical techniques for measuring the temperature in three-dimensional supersonic reactive flows have typically depended on lineshape measurements using single-beam laser absorption spectroscopy. However, absorption over extended path lengths in flows with symmetric, turbulent eddies can lead to systematically high extracted temperatures due to Doppler shifts resulting from flow along the absorption path. To eliminate these problems, Cross-Beam Saturation Absorption Spectroscopy CBSAS and Cross-Beam Inter-Modulated Fluorescence CBIMF have been developed which utilize two crossed and nearly copropogating laser beams.to record the spectral signal of an I2 ro-vibrational line in a small three-dimensional volume using a tunable CW dye laser. Temperature is extracted by fitting the recorded signal with a theoretical signal constructed from the Doppler-broadened hyperfine components of the ro-vibrational line. The CBIMF technique proved successful for extracting the temperature of an I2-seeded, Ar gas flow within a small, Mach 2, Laval nozzle where the overlap volume of the two 1 mm diameter laser beams was 2.4 mm3. At a test point downstream of the nozzle throat, the average temperature of 146 K - 1.5 K extracted from measurements of the I2 P46 17-1 spectral line compared favorably with the 138 K temperature calculated from isentropic, one-dimensional flow theory.

Subject Categories:

  • Fluid Mechanics
  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE