Experimental investigation and optimization of the effect of the air inlet position on combustion performance and emissions in a pellet-fuelled stove

In this study, the effect of burner pot design by changing supply airflow position at three different excess air ratios (λ=1.7, λ=2.2 and λ=3) and three different thermal power inputs (6 kW, 9 kW and 12 kW) on combustion characteristics and emissions at pellet stove experimentally investigated. In this context, burner pots with four different constructions were designed and manufactured, and performance tests were realised. This study showed that, in all supply airflow positions, the flue gas temperatures increased and efficiency decreased with increasing excess air ratios. Considering all excess air conditions, in the case of 6 kW, the efficiencies in the 75 mm distance showed the worst performance; in the case of 9 kW, the 30 and 60 mm distances are better, and in the case of 12 kW, it was determined that the 30 mm distance reached the highest efficiency with the value of 80.80-89.48%. The highest CO emissions obtained at the supply airflow distance of 15 mm and λ=1.7 conditions at 12 kW with the value of 2982 ppm. In all cases, it was observed that the supply airflow distance had a negligible effect on NOx emission, which was about 28.6-56.6 ppm. Also the other main aim of this study is to optimize the effect of burner pot design by changing supply airflow position in a pellet stove. For this purpose, the calibration model based on Gaussian Process Regression (GPR) with optimized hyper-parameters was proposed to determine relationship between input and output parameters of the pellet stove. The designed model was validated by the experimental data and was measured by several statistical tools. The modelling findings showed that the developed model was an efficient technique and has the potential to predict pellet stove output characteristics with high accuracy.