Theoretical analysis of transient counter-flow combustion system fueled by porous biomass particles in a non-premixed configuration under non-adiabatic conditions

Abstract

The current research aims to implement a reliable analytical model in order to scrutinize the transient behavior of a counter-flow non-premixed combustion system fueled by wet porous biomass particles under non-adiabatic conditions, including several processes such as phase change and dehumidification. A special term is added to the heat equation based on the law of conservation of energy as a means to assess the convective heat loss impacts. In order to analyze the structure of the diffusion flame and predict the time-dependent temperature and mass fractions of reactants distributions, transient forms of energy and mass equations are solved through the asymptotic method. Eventually, the influences of key factors such as equivalence ratio, porosity factor of particles, and reactants Lewis numbers on the flame structure and transient behavior of diffusion flames are elaborately investigated in the non-adiabatic condition, considering convective heat loss and compared to those in the adiabatic condition. The findings reveal that increasing the porosity factor not only improves flame temperature but also leads the flame to be located further from the fuel nozzle. In addition, when the system reaches its steady-state condition, the temperature of the flame formed in the adiabatic condition is about 20% higher than that formed in the non-adiabatic condition.