title: Application of time-division-multiplexed lasers for measurements of gas temperature and CH4 and H2O concentrations at 30 kHz in a high-pressure combustor.
abstract: Two time-division-multiplexed (TDM) sources based on fiber Bragg gratings were applied to monitor gas temperature, H(2)O mole fraction, and CH(4) mole fraction using line-of-sight absorption spectroscopy in a practical high-pressure gas turbine combustor test article. Collectively, the two sources cycle through 14 wavelengths in the 1329-1667 nm range every 33 μs. Although it is based on absorption spectroscopy, this sensing technology is fundamentally different from typical diode-laser-based absorption sensors and has many advantages. Specifically, the TDM lasers allow efficient, flexible acquisition of discrete-wavelength information over a wide spectral range at very high speeds (typically 30 kHz) and thereby provide a multiplicity of precise data at high speeds. For the present gas turbine application, the TDM source wavelengths were chosen using simulated temperature-difference spectra. This approach is used to select TDM wavelengths that are near the optimum values for precise temperature and species-concentration measurements. The application of TDM lasers for other measurements in high-pressure, turbulent reacting flows and for two-dimensional tomographic reconstruction of the temperature and species-concentration fields is also forecast.
authors.affiliation: Engine Research Center, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Caswell
authors.forename: Thilo
authors.initials: T
authors.lastname: Kraetschmer
authors.forename: Keith
authors.initials: K
authors.lastname: Rein
authors.forename: Scott T
authors.initials: ST
authors.lastname: Sanders
authors.forename: Sukesh
authors.initials: S
authors.lastname: Roy
authors.forename: Dale T
authors.initials: DT
authors.lastname: Shouse
authors.forename: James R
authors.initials: JR
authors.lastname: Gord