Active control of lifted diffusion flames with arrayed micro actuators

Active control of a lifted flame issued from a coaxial nozzle is investigated. Arrayed micro flap actuators are employed to introduce disturbances locally into the initial shear layer. Shedding of large-scale vortex rings is modified with the flap motion, and the flame characteristics such as liftoff height, blowoff limit, and emission trend, are successfully manipulated. Spatio-temporal evolution of large-scale vortical structures and fuel concentration is examined with the aid of PIV and PLIF in order to elucidate the control mechanisms. It is found that, depending on the driving signal of the flaps, the near-field vortical structures are significantly modified and two types of lifted flames having different stabilization mechanisms are realized.