Corona Discharges in Asymmetric Electric Fields and its Impact on Ionic Wind Generation

The challenge of thermal management in small form-factor electronic devices drives the development of novel technologies for heat dissipation. Ionic wind devices, which operate on the principle of electrohydrodynamic interaction, are being studied as a replacement for conventional fans because of the inherent advantages of small acoustic signature, low weight, low power consumption, and the absence of moving parts. In particular, corona discharge driven ionic winds are favored for their ease of operation in direct current (DC) mode and stability at atmospheric pressures.

Miniaturization of ionic wind blowers to extremely small form factors (heights < 3 mm) is accompanied by various challenges. The operating potentials too are constrained to ~2000V to minimize safety hazards. To obtain flow rates comparable to fans under such constraints necessitates development of novel configurations and new modes of operation.

This dissertation presents a multi-electrode corona discharge as a solution to the challenges arising from miniaturization of duct heights in ionic wind devices. An overview of fundamentals of corona discharges and ionic winds, and a literature survey of various ionic wind devices and numerical modeling procedures is included. Data from preliminary experiments on sub-millimeter scale coronas is presented and compared to theory to study the limiting conditions for corona formation and sustenance. Corona discharges are studied experimentally and numerically in configurations that induce asymmetric electric fields in the discharge space. Multiple collector configurations are a particular subset of these and are studied in more detail to characterize their fundamental behavior and to understand the differences from traditional discharges involving a single collecting electrode. The configurations are shown to present characteristics that are suitable for mitigating some of the problems encountered in device miniaturization. The three-electrode configurations are shown to reduce the onset potentials for device operation, increase the total current production, and present a favorable redistribution of current to the various collectors. Traditional corona modeling procedures are demonstrated to have significant shortcomings in asymmetric configurations and an alternative modeling procedure is developed for application in these conditions.

The multi-electrode configurations were adapted to the development of an ionic wind blower. In a laboratory setup, these configurations are shown to improve flow rates by a factor of ~3x and reduce power consumption by up to 0.5x. A prototype fabricated within the constraints imposed by handheld electronic systems on size and operating potential is described. The performance of the prototype-installed system is compared to the baseline system for flow and acoustic characteristics and is shown to be comparable in terms of the flow rates generated and significantly better in the acoustic signature levels.