The main purpose of this study is to investigate the structures of the flames and isothermal jets formed around a fuel jet surrounded by a swirling air flow. Two typical types of stable flames and one oscillating transition flame were produced by changing the positions of the exit of fuel nozzle in the reverse flow zone formed by the strongly swirling air flow. Clear pictures of their flames and isothermal jets were obtained by measuring time-averaged axial velocity, temperature and species concentrations.
The second purpose is to introduce the behaviors of the large time dependent flow motion called the processing vortex core in some flame and isothermal states. In order to elucidate the motion of helical vortex core and describe the effects of combustion on the large time dependent motion, measurements of instantaneous velocity and static pressure were conducted. Regular fluctuations of velocity and pressure signal are induced by the motion of helical vortex core. The motion of helical vortex core is described with assumption that the motion of vortex core center is governed by time-mean velocity field. Disappearance of these motions with the combustion reaction is observed and this phenomenon is explained with corresponding time averaged structures of swirling flames.
