Secondary Air Velocity Research Articles

Eddy Diffusions of a Fuel Gas from a Cylindrical Fuel Burner

It is easy to determine the mechanism of time average eddy diffusion of fuel gas in a flame, but it is very difficult to determine the instantaneous movements of fuel gas in the flame. In the experiment described in this paper the fuel jet was ignited at various positions in the fuel jet by electric sparks, and the spreading of the flames was observed. Ignition probability was measured at various positions of the fuel jet, being determined by the mixture ratio and mean velocity of fuel jet and the velocity of secondary air. It seems that the ignition probability chiefly depends upon the fluctuation of the fuel concentration. It was found that, for an ignition for obtaining a steady flame, a spark must be provided immediately behind the burner tube wall.

The Blow-off of Diffusion Burner Flames

The blow-off of diffusion burner flames is affected by the shape of the burner tube, the flow pattern of mixture and surrounding secoundary air, and the state of concentration. There are three kinds of states of the blow-off of a diffusion flame. One is the state in which the mixture is in laminar flow. The other two states are those of turbulent flow. In the turbulent region of the mixture, a vortex of flame is created just outside of the burner tube. At a relatively low velocity of mixture flow in this region, the vortex of flame is blown away by the increasing of the surrounding secondary air velocity, and at a higher velocity of the mixture flow, the blow-off of the flame is accomplished by the blow-off of the propagation from the vortex of flame, as the velocity of secondary air increases.