Abstract
This paper studies the shape of jet diffusion flame, whose burner diameter is less than 1 mm. Previously, it has been assumed that the buoyancy force has little influence on the shape of a flame of such a scale, owing to the large value of associated Froude number.However, little is known on the critical burner diameter over which the buoyancy force begins influencing the shape of flame. The lengths of butane diffusion flames are measured using three burners of different diameters to vary the Froude number. The results are understood on the basis of a flame-length theory developed by the authors.
