Influence of the temperature fluctuations on the flame temperature and radiative heat exchange inside a pulverized coal-fired furnace

Abstract

In this paper, influence of the temperature fluctuations, (as a version of turbulence-radiation interaction), on the flame temperature and radiative heat exchange inside the pulverized coal-fired furnace was investigated. The radiative heat exchange was solved by the Hottel zonal model. The influence of the temperature fluctuation was studied for three values of the extinction coefficient of the flame: 0.3, 1.0, and 2.0 m-1. The investigation was conducted for the relative temperature fluctuations obtained by solving the transport equation for the temperature variance, and for four constant values of the relative temperature fluctuations (0.0, 0.1, 0.15, and 0.2). The maximal values of the mean temperature fluctuations and relative temperature fluctuations were obtained in the region close to the burners. The decrease of the flame temperature of about 100 K was obtained in the hottest region, for every extinction coefficient. An increase in the mean wall flux was found to be on the order of several percents, compared to the case without the temperature fluctuations. When the temperature variance was calculated, the mean relative temperature fluctuations were approximately 15%, for every extinction coefficient. The mean wall fluxes increased and flame temperature at the furnace exit plane decreased with the increase in the relative temperature fluctuations. The selected indicators of the furnace operation, such as the mean wall flux and mean flame temperature at the furnace exit plane, obtained for the calculated temperature variance, were close to the values predicted for the constant relative temperature fluctuation of 15%.