Observation of Laminar Premixed Flame Structure Variation Associated with Downsizing to Micro Scale

Abstract

   A micro laminar premixed flame formed on a burner with pilot flame is observed. The flame is stabilized even on the burner whose diameter is 0.4 mm. However, the shape of the flame formed on the burner whose diameter is less than 1mm and at around the lowermost flow rate is near spherical. It is similar to the appearance of micro diffusion flames. On the other hand, the flame formed on the burner whose diameter is less than 0.6 mm is not considered as propagating flame, because typical laminar propagating flame has a structure more than 0.6 mm thickness at this condition. We observed the flame structure variation and the uppermost and the lowermost flow rates which the flame could be formed stably. It is, consequently, supposed that the flame formed on the burner whose diameter is submillimeter is dominated by the diffusion mixing of oxygen and methane from the premixture and high temperature heat flux from the pilot gas flow. We, further, examined the flame structure and the extinction mechanism of the premixed microflame and tried to explain scale effects on the extinction limit and the flame structure variation.