Zhixun Xia

Bio: Zhixun Xia is an academic researcher from National University of Defense Technology. The author has contributed to research in topics: Combustion & Combustor. The author has an hindex of 16, co-authored 82 publications receiving 975 citations.

Three-Electrode Plasma Synthetic Jet Actuator for High-Speed Flow Control

Abstract: TO MANIPULATE a flowfield to realize a desired change, various types of actuators for different flow-control intents have been proposed [1]. Among all flow-control methods, plasmabased actuators are very promising because of their advantages of robustness, simplicity, sufficient bandwidth, and fast response [2]. At present, most of the plasma-based devices in common use are developed using dielectric-barrier discharges [3], glow discharges [4], arc discharges [5], or RF discharges [6]. For the surface discharge presented above, the plasma is formed near the actuator surface and interacts directlywith the base flow to be controlled. As an alternative technique to the surface-based approach, plasma flow actuation can also be achieved by a jet impinging on to a flow. And a new type of plasma-based pulsed jet device, in which a spark discharge is struck to heat the gas in a small cavity and forms a pulsed jet that issues through a small orifice, has been proposed recently [7]. A pulsed jet device that specifically uses spark discharge to heat the cavity has been studied by several groups under different names [7–10]. This type of pulsed jet device has the characteristic of zero mass flux of synthetic jet actuator, which requires no flow supply and no flow piping [11] and has the advantages of no moving parts, very low mass, and extremely fast response of surface plasma actuator as well [2], and so we call it a plasma synthetic jet (PSJ) actuator. Although computational analyses [7] and experimental demonstrations [9] indicate that the PSJ has the potential to manipulate a supersonic flowfield, a significant increase in control authority is needed for the actuator to be effective for supersonic/hypersonic flow. For most applications, the control authority of the actuator depends on the momentum imparted into the controlled flowfield, and the jetmomentum is a function of the jet velocity and the gasmass ejected from the actuator. The speed of the PSJ is as high as several hundredmeters per second, but the cavity volume of the actuator is so small (∼50 mm) [9,10] that the expelled gas mass during the jet is too little. The ejected gas mass can be enhanced by augmenting the cavity volume. The augment of the cavity needs the electrode gap to increase to realize the cavity to be heated sufficiently and instantaneously. Based on Paschen’s law, the breakdown characteristic of a gap is a function of the product of the gas pressurep and gap length d, Ud f pd . Thus, the disruptive voltage increases as the gap length increases. For example, at 1 atm in air, the electric potential required for gap breakdown in a uniform electric field can be described as Ud 3d 1.35, where the units of Ud and d are kilovolts and millimeters, respectively. For a nonuniform electric field produced by the electrodes of the PSJ actuator, the disruptive voltage for a 1.2 mm air gap is 4.7 kV [10]. The increase of the disruptive voltagewill lead to the size andweight of the power supply increase remarkably. In this note, a three-electrode PSJ actuator based on a new discharge mode is presented. The actuator could create highmomentum PSJ with relative low disruptive voltage. The high-speed shadowgraphy visualization is used to characterize the performance of the three-electrode PSJ actuator, and the influence of the capacitance on the flowfield and the jet velocity is investigated.

Review of actuators for high speed active flow control

Abstract: Actuators are one of the key points for the development of active flow control technology. Efficient methods of high speed flow control can provide enhanced propulsive efficiency and at the same time enable safe and maneuverable high speed flight. The development of high speed flight technology promotes the emergence of novel and robust actuators. This review introduces the state of the art in the development of actuators that can be used in high speed active flow control. The classification and different operation criteria of the actuators are discussed. The specifications, mechanisms and applications of various popular actuator types including fluidic, mechanical, and plasma actuators are described. Based on the realistic need of high speed flow control and the existing results of actuators, a new actuator design method is proposed. At last, the merits and drawbacks of the actuators are summarized and some suggestions on the development of active flow control technology are put forward.