Numerical investigations of soot generation during wood-log combustion

Journal article, 2022

Soot formation is an important challenge in the design of modern wood stoves, as soot not only deteriorates the combustion efficiency but also poses threats to human health. Although soot formation in biomass combustion has been studied previously, the investigation at wood stove level is still rare due to its complex nature. In this paper, numerical simulations are performed to uncover the basic trends of soot formation during wood log combustion. The soot formation model is developed based on a particle-resolved biomass combustion algorithm, where the intraparticle heat and mass transfer effect, soot mass fraction and particle size are all resolved. Besides, simplified tar and precursor models are used in solving the reaction kinetics of soot formation. The integrated model is first validated through the combustion simulation of a micron-sized coal particle in air, where the predicted flame temperature and the soot volume fraction show improved agreement with experimental data compared to a previous modeling work. Thereafter, the soot formation during wood-log combustion in a confined stove is studied. Different combustion behaviors are observed for varying numbers of wood logs and for variations in the wood-log stacking. Additionally, the flow field temperature, tar, soot, and oxygen concentrations during the combustion are analyzed. Finally, the influences of the air intake rate, the relative distance between wood logs, and temperature boundary condition on the soot formation are discussed. This work provides useful information for the design and the optimization of modern wood stoves.