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The term “hybrid draft biomass cookstove” (HDBC) refers to a stove that employs both natural and forced drafts for its primary and secondary air supply. The HDBC optimization analysis is carried out in this work using computational fluid dynamics (CFD), considering the effect of forced draft secondary air mass flow rates to achieve the optimum (lower emissions and higher efficiency) HDBC performance. The analysis includes combustion and soot modeling to evaluate the thermal and emission performance of the stove. The CFD results are validated against the experimental data obtained from the water boiling test (WBT 4.2.3). The extremely low or high secondary air mass flow rate degrades the stove’s performance; hence, its optimization is essential. The optimal mass flow rate identified in this investigation was 0.017 kg/s, at which the thermal and emission performances of HDBC were evaluated. An eddy dissipation model is employed to simulate biomass combustion, considering the reaction kinetics of wood volatiles reacting with oxygen, and a one-step soot model is used to predict soot formation. The combustion model agreed well with the experimental data for efficiency and temperature, with an average deviance of 10% and 20%, respectively. However, it significantly overestimated CO emissions by 81% and achieved Tier 4 performance in simulation as opposed to Tier 0 in the experiment. The PM2.5 emissions were under predicted by the soot model, but both the CFD and the experiment results achieved Tier 4 performance as per the World Health Organization (WHO) standards. Hence, a one-step soot model was found to be effective in predicting soot formation.
Ghiwe et al. (Thu,) studied this question.