A Method for the Determination of Flame Temperature from Emission in the Ultraviolet OH Band

Abstract

A new method for flame temperature measurement has been developed involving measurement of radiation, emitted by flames, in a narrow wavelength interval within the ultraviolet OH emission band. The mean value of flame emissivity within the wavelength interval is evaluated by measurement of mean flame transmission for a continuous spectrum source. The method requires that the wavelength interval studied be so narrow that the emission of the source used for transmission measurement and that of a blackbody at flame temperature both be approximately constant over the interval.The method has been tested on steady flames over temperature ranges from 2000°K to 3000°K and excellent agreement obtained with sodium line reversal measurements. Temperatures of pulsed flames have been determined from photographic traces obtained with a monochromator-photo-multiplier-oscilloscope-camera combination. Two high speed light choppers were used, one to interrupt the radiations entering the monochromator and the other to interrupt, at a different frequency, the radiations from a hydrogen discharge lamp transmitted by the flame to the monochromator. The time resolution was 0.10 millisecond and the accuracy in temperature measurement about 40°K in the range 2000°K to 3000°K. The method was calibrated by means of sodium line reversal although it is easily adaptable to absolute calibration.