The use of chemiluminescence for the detection of temperature and fuel-to-air ratio in turbulent premixed flames

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Virginia Tech

A fast response method for the determination of temperature and equivalence ratio has been developed for turbulent premixed flames. This method utilizes chemiluminescent signals to make correlations with flame temperature and equivalence ratio. Emissions from two radical groups are used for the correlations: an OH system at 309 nm and a CH system at 431 nm. The experimental apparatus consists of a turbulent burner, an optical system (lenses, monochromator, and photomultiplier tube), and a data collection system (digital oscilloscope and computer). An optical system using fiber optics and band pass interference filters was also investigated. The spectra of turbulent, premixed methane flames of known stoichiometry were recorded. A high temperature Pt-Pt10%Rh thermocouple was used to establish flame temperature. The ratio of signal width to signal height of the OH spectra was used to correlate flame temperature. The ratio of OH to CH signal heights was used to correlate equivalence ratio. Turbulent correlations were compared to laminar correlations developed in previous studies. The effect of increasing turbulence on correlations was investigated. Applications for this technology and recommendations for future work are discussed.