The use of aerodynamic actuators, such as leading edge slats, trailing edge flaps, roughing strips and ailerons interact with the air during flight, providing maneuverability for air vehicles. These mechanical devices have many inherent, detrimental attributes, such as space requirements on the wing, added wing weight, second response times, increased drag, and increased airframe vibration, resulting in the production of noise. The potential to eliminate or improve upon these detrimental attributes may be realizable by replacing the current mechanical actuators with plasma actuators. Specifically, the surface-discharge-mode, dielectric barrier discharge (SDBD), plasma actuator has a response time on the order of microseconds to milliseconds, does not increase vibration by mounting flush to the wing surface, does not increase drag, and adds negligible weight to the wing. Unfortunately, these devices are not yet powerful enough to perform many of the tasks required for aerodynamic applications; however, they have demonstrated the potential to do so, providing motivation for the current study. Currently, the approach of the research community has focused on coordinating studies designed to determine the physics of the device and parametric studies to determine optimal configurations required for immediate application.
In this work, an experimentally based study utilizing optical emission spectroscopy, current-voltage measurements, and a force balance have been successfully applied, contributing new, specific detail to the morphology and characterization of the SDBD. The results of this study were tailored to aid the development of the appropriate, essential physics required for computational modeling of the SDBD. Initially, force measurements of the induced thrust were obtained to demonstrate how week the induced thrust is, justifying the need for a fundamental study. These results are also important in understanding an apparent discrepancy in the reported dependence of the induced thrust upon applied voltage amplitude.
Electrical properties of the device such as breakdown voltage, surface charge voltage, effective capacitance with and without a discharge, electrical current, dissipated power, and the details of breakdown are measured as a function of applied voltage. The measured surface potential is of particular interest because it provides information about one of the boundary conditions needed to solve Maxwell equation’s of electromagnetics. Measurements showed that the surface charge potential along the dielectric surface is around 4000 and 4200 volts for the positive and negative voltage half-cycle, respectively, at an applied potential of 6000 volts.
Properties determined from emission, including the relative concentrations of N2(C3Πu) and N2+(B2Πg), and rotational and vibrational temperatures, as a function of position, voltage amplitude and phase of the driving voltage, have been measured. The spatially resolved relative concentrations of N2(C3Πu) and N2+(B2Πg) are useful in demonstrating the difference in structure between the discharge occurring during the positive voltage half-cycle versus the discharge occurring during the negative voltage half-cycle. The rotational temperature obtained from the 1st negative band system of N2+ was shown to be significantly greater than the rotational temperature obtained from the 2nd positive band system of N2 and was shown to be a direct consequence of the local electric field. This is shown to be important when calculating the rate constants for reactions involving ions and neutrals. For example, neglecting this deviation in temperature results in an order-of-magnitude difference in rate constants. Therefore in modeling the plasma, measurements show it is important to calculate the ion temperature via the Wannier relationship and then calculate the rate constants.
The details of these experiments including set-up, results, significance and discussion, along with an exhaustive summary of the current understanding of the surface-discharge-mode, dielectric barrier discharge, constitutes the bulk of this dissertation.