Kestabilan Api Difusi Double Concentric Jet Flow (Pengaruh Posisi Central Fuel Tube)

The effect of axial position of central fuel tube on diffusion fuel injection velocity stability of double concentric jet flow have been investigated experimentally. Fuel flow rate was varied from 1 to 12 m/s, primary air 0,7 - 3,2 m/s, and secondary air 2, 3, and 4 m/s. This research was intended to observe the characteristics of leading edge of flame using still camera and to determine lift off and blow out limits with variation of the secondary air flow and the position of central fuel tube. The result was flame stability diagram of fuel rate and primary air flow limits causing lift off and blow out. It was concluded that the biggest stability region occurred when concentric annulus tube and the least one when central fuel tube position was located in the bottom concentric annulus tube. The lift off phenomena showed and increase in turbulance intensity that caused the more turbulent flame, however, the upstream flame was laminar. Besides, the high secondary air flow caused flame shape to be shorter and wider. Key words : central fuel tube, diffusion flame, concentric annulus tube, external air pip