EFFECT OF SWIRL ON COMBUSTION CHARACTERISTICS IN PREMIXED FLAMES

A double concentric premixed swirl burner is used to examine rite stru cture of two different methane-air premixed flames. Direct flame photo graphy together with local temperature data provides an opportunity to investigate the effects of swirl number distribution in each annulus on the global and local flame structure, flame stability and local dis tribution of thermal signatures. An R-type thermocouple compensated fo r high-frequency response is used to measure the local distribution of thermal signatures in two different flames, each of which represents a different combination of swirl number in the swirl burner, In order to improve the accuracy of the temperature data at high-frequency cond itions, information on the thermocouple time constant are also obtaine d under prevailing conditions of local temperature and velocity by com pensating the heat loss from the thermocouple sensor bead, These resul ts assist in quantifying the degree of thermal nonuniformities in the flame signatures as affected by the distribution of swirl and to devel op strategies for achieving uniform distribution of temperatures in fl ames.