Abstract
Effect of gravity direction on stability of small spherical diffusion flame (so called 'microflame') is investigated numerically. In this paper, microflames under normal gravitational field and reversed gravitational field are compared. The flame under reversed gravitational field can establish more stably. Here stability means it can establish under lower flow rate. When the microflame is reversed, the way of oxygen flow differs from under normal gravitational field. There are two distinct features. First, under normal gravitational field more oxygen can flow in flame base. Chain reaction (H+O_2→OH+O) occurs more fast. Second, under reversed gravitational field flame base exists at flame top. Distance of flame base to burner is longer and heat loss decreases. That means heat loss is more effective than heat release, and the microflame under reversed gravitational field can establish more stably
