Stabilization of a Round Jet Flame with a Recirculation Zone in Parallel Air Flow : Part I. General Properties of the Flame and the Mixing Process in the Recirculation Zone

Abstract

The stability limits were measured for a double concentric propane-air premixed jet flame. The burner tubes have an 8 mm inner diameter with rims of 0-7 mm thicknesses. The flame was stabilized in a higher velocity region where the rim is of sufficient thickness because of a recirculation zone forming behind a thick rim. For the recirculation zone, the aerodynamic structures such as the length and flow directions were investigated as well as the thermodynamic structures, that is, the distribution of temperatures, gas components concentration and local mixing ratio. The results showed that the real mixing ratio of the recirculation zone changed with the flow conditions. The real mixing ratio was measured by CO2 trace method with cold flow, and was predicted successfully with a simple assumption for the ratio of the mass exchanges.