DC-Augmented Dielectric Barrier Discharge (DCA-DBD)

Time-dependent multiphysics interactions that drive the energy transfer in electromechanical systems are poorly understood. We probe dielectric barrier discharge (DBD) with an external DC-augmented (DCA) field to reveal new mechanistic insights. The biased HV DC electrode influences the interaction between the charged ions and the E-field, surface and space charge, and neutral molecules. Direct force measurement, velocity profiles, and time-resolved electrical and optical measurements of discharge characteristics provide evidence of complex plasma/flow interactions. Negative DCA leads to modest improvements in momentum transfer due to the field-augmented ion acceleration before the system transitions to sliding discharge and a counter jet at the DCA electrode, canceling the gains from positive ion acceleration. Positive DCA monotonically increases the wall-parallel force. A new oscillating residual charge interaction mechanism is identified to explain a greater than 2-fold increase in horizontal thrust, in which the acceleration of positive ions is augmented by the attraction from the residual (negative) charge

Momentum Injection via Dielectric Barrier Discharge Actuators in Low-Speed External Flow

Dielectric barrier discharge (DBD) plasma actuators can generate a wall jet without moving parts through interaction between ionized and neutral molecules in an electric field. The coupling between electro-hydrodynamic, turbulence, and viscous effects in the flow boundary layer remains unclear and deserves careful investigation. We present an experimental investigation of momentum injection by DBD actuators in a U_external = 5 m/s and U_external = 11 m/s co-flow and counter-flow configuration over a range of VAC = 12 kV - 19.5 kV peak-to-peak at a frequency of 2 kHz. In the co-flow configuration, the DBD actuator adds momentum to the boundary layer, similar to an electrohydrodynamic (EHD) jet in quiescent conditions. In the counter-flow configuration, flow separation is observed at free stream velocity U_external = 5 m/s. The momentum displacement in the counter-flow configuration is ~ 6x greater than EHD jet momentum in a quiescent environment. Both co-flow and counter-flow momentum injections show diminishing effects with increased external flow speed. This work highlights that the resulting flow pattern is not a simple superposition of the EHD jet and the free stream but is determined by a balance between the inertial, viscous and Coulombic forces of the EHD and the external flow. The velocity profiles and momentum characteristics can be used to validate numerical models and inform the design of DBD actuators for active flow control.Comment: 14 Pages, 13 figure

Calculation methods and detection techniques for electric and magnetic fields from power lines with measurement verification

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.An accurate determination and characterization of electric and magnetic fields produced by power lines is a complex task. Different models must be used for far fields and for near fields. This study is centered on computation and measurement aspects of extremely low frequency magnetic fields in the direct proximity of the conductors of power lines, situated well above the ground level. Conventional approximation of a sagged wire as a straight horizontal conductor of infinite length has been substituted with a periodical catenary model of the conductors A series of measurements performed with all electric utility bucket truck provide unique magnetic field data very close to the conductors. A conceptual design of a power line proximity detector is proposed as a result of these studies