Numerical and Experimental Study of Amplitude Modulated Positive Corona Discharge

The electrical behavior of a modulated positive corona discharge loudspeaker was studied. A coaxial transducer in air was built using a central copper wire of 75 μm radius (inner electrode) and a perforated tube of 11 mm (outer electrode). A high voltage DC supply provided the bias current and a sinusoidal signal was superimposed to measure the discharge admittance. The experimental results could not be matched to previously reported equivalent circuits with fixed components. Using the basic equations that describe the ion motion, a numerical model was proposed. The computed values matched well the experimental data and suggested an equivalent circuit composed of frequency dependent conductance and capacitance. This dependence is closely related to the ion travel time between electrodes (transit time). Simulations carried out at several inter-electrode distances could be synthesized in a single plot where the different results overlap and further emphasize the role of the transit time. This numerical model proved to be an efficient tool to simulate and design modulated corona transducers. Copyright © 2014 IFSA Publishing, S. L.