Accession Number:

ADA516713

Title:

Diode Laser-Based Detection of Combustor Instabilities with Application to a Scramjet Engine

Descriptive Note:

Journal article (postprint)

Corporate Author:

AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE

Personal Author(s):

• Carter, Campbell D.
• Gruber, M. R.
• Rieker, G. B.
• Jeffries, J. B.
• Hanson, R. K.
• Mathur, T.

Report Date:

2010-02-01

Pagination or Media Count:

10.0

Abstract:

Fluctuations in temperature non-uniformity along the line-of-sight of a diode laser absorption sensor in a model scramjet are found to precede backpressure-induced unstart expulsion of the isolator shock train. A novel detection strategy combining Fourier analysis of temperature time series to determine low-frequency heat release fluctuations with simultaneous measurements of multiple absorption features of H2O to identify temperature non-uniformities was applied to the scramjet combustor. Time-resolved absorption is measured using wavelength modulation spectroscopy for three transitions chosen with different temperature-dependent absorption characteristics. The line-of-sight LOS-averaged temperature inferred from the ratio of absorption from one pair of transitions is highly sensitive to low-temperature nonuniformities along the absorption path while the other ratio is less sensitive. The fraction of fluctuations in the range 1 f 50 Hz is determined from short-time Fourier transforms STFTs of the measured temperatures from both transition pairs.

Descriptors:

• *SUPERSONIC COMBUSTION RAMJET ENGINES
• *DIODE LASERS
• DETECTION
• TIME SERIES ANALYSIS
• LASER BEAMS
• COMBUSTORS
• LASER APPLICATIONS
• LONG WAVELENGTHS
• MODULATION
• SHORT WAVELENGTHS
• INSTABILITY
• LOW FREQUENCY
• FOURIER ANALYSIS
• MEASUREMENT
• FOURIER TRANSFORMATION
• REPRINTS

Subject Categories:

• Lasers and Masers
• Jet and Gas Turbine Engines

Distribution Statement:

APPROVED FOR PUBLIC RELEASE