Comparative Study on Combustion and Flame Characteristics of Laminar Methane/Air and N-Butane/Air Flames in a Micro-Slot Burner

Abstract

Combustion and flame characteristics of laminar methane/air and n-butane/air flames in a 3D-printed micro-slot burner is compared and reported in this study. The stability limit, flame appearance, and emission performance are investigated experimentally. In addition, past research on conventional burners is compared with the results of this study throughout the paper. The construction of this micro-slot burner was met by selective laser melting (SLM) process. Flame characteristics such as lift-off height, length, visible area, maximum width, and neck width are obtained using an image processing algorithm and are examined at different fuel and airflow rates. The results show that the blow-out limits of methane/air and n-butane/air flames are almost the same when compared at the same volume flow rates, although the methane/air flames are more stable than n-butane/air flames at the same thermal input powers. A region of interesting rope-like oscillatory flames (that has never been seen before in conventional burners) is observed in a small portion of a stable region for n-butane with a period ranging from $75.0$ to $210.0\mathrm{m}\mathrm{s}$ . It is also observed that the fuel type and fuel and airflow rates affect the flame shape and appearance and the flames formed by heavier fuel (n-butane) have longer length, lift-off height, maximum width, and visible area and lower neck width. Furthermore, methane/air flames exhibit lower values of $\mathrm{C}\mathrm{O}$ and higher values of ${\mathrm{N}\mathrm{O}}_{\mathrm{x}}$ in the flue gas when compared to n-butane/air flames.