Combustion control using a lobed swirl injector and a plasma swirler

A low swirl injector incorporating a lobed swirler and a plasma swirler was developed for combustion control. The lobed swirler was used to replace the vane swirler to enhance fuel/air mixing and stabilize flame downstream of the injector. The plasma swirler installed at the exit of the injector was used to control the flame lift-off height, which is a critical parameter influencing the flame stability and thermal load. The plasma swirler is composed of three dielectric barrier discharge (DBD) actuators which were placed in a circular array around the axis to generate ionic wind in the circumferential direction. Experiments were carried out to investigate the aerodynamics and combustion characteristics of the low swirl injector. Non-reacting velocity distributions at the exit of the injector with different blockage ratios were captured with two-dimensional Particle Image Velocimetry. Reacting flow velocity profiles downstream of the lobed swirl injector were measured by two-dimensional Laser Doppler Anemometry. Based on the non-reacting flow field analysis, guidelines of the optimal design were deduced and a proper perforated plate was chosen to carry out further combustion experiments. Stable lifted flame was sustained by the lobed swirler with a vane angle of 30 degrees and a blockage ratio of 75.5% which demonstrated that the flow field with a suspended central recirculation zone was suitable for stabilizing the lifted flame. It was found that the DBD actuation enhances the effectiveness of combustion control that can be used to adjust the position of the flame front.