ARTICLE:

• DIODE-LASER ABSORPTION SPECTROSCOPY SENSORS FOR ACTIVE CONTROLS OF TURBULENT COMBUSTION  download article

M. Shimura
Tokyo Institute of Technology, Tokyo, Japan

Mamoru Tanahashi
Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, Japan

Toshio Miyauchi
Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, Japan

ABSTRACT

Diode-laser absorption spectroscopy has been applied to a 200kW swirl-stabilized turbulent combustor to detect high frequency combustion oscillation and combustion state related to combustion noise. Two diode-laser absorption spectroscopy techniques of scanned-wavelength method and fixed-wavelength method are adopted. In the scanned-wavelength method, fluctuations of temperature and H₂O mole fraction up to 1kHz are detected. Two dominant peak frequencies of power spectra of these fluctuations, which are about 125Hz and 140Hz, coincide with those of pressure fluctuation in the combustor. In the case of control by secondary fuel injection, the energy at peak frequency of temperature and H₂O mole fraction decreases in accordance with noise reduction. Similar to the combustion noise, temperature fluctuation shows a minimal value at the appropriate frequency of secondary fuel injection. By analyzing transmitted signals, the fixed-wavelength method provides power spectra similar to those obtained by the scanned-wavelength method. The advantage of the fixed-wavelength method is capability of detection of high frequency combustion oscillation more than 1kHz. These results prove that the diode-laser absorption spectroscopy has great applicability as sensors for the active controls of turbulent combustion.

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