Y. Xiong, M.S. Cha, and S.H. Chung
Proc. Combust. Inst. 35, pp. 3515-3520, (2015)
Experiments were performed by applying sub-critical high-voltage
alternating current (AC) to the nozzle of laminar propane coflow
diffusion flames. Light scattering, laser-induced incandescence and
laser-induced fluorescence techniques were used to identify the soot
zone, and the structures of OH and polycyclic aromatic hydrocarbons
(PAHs). Particle image velocimetry was adopted to quantify the velocity
field. Under certain AC conditions of applied voltage and frequency, the
distribution of PAHs and the flow field near the nozzle exit were
drastically altered, leading to the formation of toroidal vortices.
Increased residence time and heat recirculation inside the vortex
resulted in appreciable formation of PAHs and soot near the nozzle exit.
Decreased residence time along the jet axis through flow acceleration
by the vortex led to a reduction in the soot volume fraction in the
downstream sooting zone. Electromagnetic force generated by AC was
proposed as a viable mechanism for the formation of the toroidal vortex.
The onset conditions for the vortex formation supported the role of an
electromagnetic force acting on charged particles in the flame zone.