An experimental study of emission from counterflow diffusion flames for application to combustion control

摘要

The use of photodiode detectors was examined in the context of developing a fast time response diagnostic system for use in real-time control of combustion systems. Emission intensities [W/sr-m{sup}2] from well-characterized, steady counterflow diffusion flames were measured using a calibrated pyroelectric detector and narrow band-pass filters. The pyroelectric detector has uniform spectral response, facilitating absolute radiation intensity measurements. Fast time-response silicon (Si) and lead selenide (PbSe) detectors were characterized by comparison with the pyroelectric detector measurements. Five methane/oxygen/helium/nitrogen flames of differing fuel and oxidizer concentrations and flow rates were examined. Methane mole fractions in the fuel flow varied from 0.15 (blue flame) to 0.29 (sooty flame), while oxygen mole fractions in the oxidizer flow varied from 0.43 to 0.82. Fuel flow rates varied from 100 to 211 cm{sup}3/s, and oxidizer flow rates varied from 43 to 123 cm{sup}3/s. A series of spectral filters were used with each detector to isolate the emission from targeted combustion species: CO, CO{sub}2, H{sub}2O, CH, and C{sub}2. The emission data were compared with spatially integrated concentration data determined in previous work via gas sampling. The combined data from the photodetectors and gas sampling measurements were evaluated in the context of developing species specific filter and detector combinations for real-time measurement of important combustion species.