Measurement of temperature and emissivity of biomass candle flame using spectral thermometry

To develop in-situ temperature measurement technology for biomass combustion environment, rose and tea soybean candle flames were experimentally studied using spectral thermometry in this paper. The distributions of temperature and emissivity at different flame heights were calculated using four emissivity models, i.e., the Gray emissivity model, the Hottel and Broughton emissivity model, the polynomial approximation emissivity model and the Rayleigh approximation emissivity model. The results showed that the emissivity calculated by the polynomial approximation emissivity model was larger than that calculated by other models at the same flame height. The average temperature of rose soybean candle flame was 59 K larger than that of tea soybean candle flame. The temperature results were verified by the hyper-spectral imaging device and the polynomial approximation emissivity model performed the best. Normalized emissivity showed that the radiative property of the rose soybean candle flame was stronger than that of the tea soybean candle flame. Moreover, the alkali metal content in the tea soybean candle flame was higher than that in the rose soybean candle flame along the flame height.