Single-Pixel Particle Image Velocimetry for Characterization of Dielectric Barrier Discharge Plasma Actuators

Unsteady Vortex Structure Induced by a Trielectrode Sliding Discharge Plasma Actuator

Electromagnetic and Ozone Emissions from Dielectric Barrier Discharge Plasma Actuators

Novel Technique to Determine SparkJet Efficiency

In recent years, single dielectric barrier discharge (SDBD) plasma actuators have gained great interest among all the active flow control devices typically employed in aerospace and turbomachinery applications [1,2]. Compared with the macro SDBDs, the micro single dielectric barrier discharge (MSDBD) actuators showed a higher efficiency in conversion of input electrical power to delivered mechanical power [3,4]. This article provides data regarding the performances of a MSDBD plasma actuator [5,6]. The power dissipation values [5] and the experimental and numerical induced velocity fields [6] are provided. The present data support and enrich the research article entitled “Optimization of micro single dielectric barrier discharge plasma actuator models based on experimental velocity and body force fields” by Pescini et al. [6].

Ionic wind and ozone generation in a single magnetic fluid dielectric barrier discharge plasma actuator with different electrode configurations

The effects of single dielectric barrier discharge plasma actuators on flow control are studied using a new frequency and pressure-dependent capacitance-based model by calculating the spatiotemporal distribution of surface charge density in the present work. The proposed model is an improvement over earlier similar efforts, but it retains the superior features of previous macroscopic models. It can be used to accurately compute the spatiotemporal distribution of body force due to plasma actuation without computing the complex electrodynamics equations for charge density on microscopic scales. It has been shown that the proposed model estimates the time-averaged total body force more accurately than similar models developed earlier, as compared to experimental results. The effects of plasma excitation frequency and the voltage waveform were considered. The proposed model has been incorporated into a Navier–Stokes equation solver in a time-accurate manner to study single dielectric barrier discharge plasma actuation in a quiescent flow environment. The onset of plasma actuation causes the creation of a complex transient vortical flowfield: one of its actions is to create a wall jet. Computed instantaneous velocity profiles at downstream locations show this wall jet, and they are compared with the experimental results. The computed results of the evolution of a starting vortex in a quiescent air induced by initiation of single dielectric barrier discharge plasma actuation display an excellent match with the experimental results of Whalley and Choi (“The Starting Vortex in Quiescent Air Induced by Dielectric-Barrier-Discharge Plasma,” Journal of Fluid Mechanics, Vol. 55, July 2012, pp. 192–203).

Control of a turbulent boundary layer separating on a half-cylinder mounted on a flat plate has been investigated using a Dielectric Barrier Discharge (DBD) plasma actuator placed along the apex of a cylinder. The main focus of the study has been to evaluate if the control ability of the actuator can be improved through pulsed actuation compared to its steady counterpart. Investigations of the electric wind induced by the DBD plasma actuator in still air, when mounted on the flat plate, revealed that while the steady actuation produces an electric wind similar to a wall jet, the pulsed actuation creates a train of co-rotating vortices. The vortices are the result of a starting vortex produced by the actuator at each actuation pulse. A parametric study showed a dependence of the size, shape and propagation velocity of the vortices on the pulse frequency and duty cycle. With the actuator mounted along the apex of the cylinder, Particle Image Velocimetry measurements of the uncontrolled and controlled flow with a free-stream velocity of 5 m/s showed a clear reduction of the recirculation region downstream the cylinder when using plasma actuation. An even higher control effect could be achieved with pulsed actuation compared to the steady actuation. Phase-locked measurements of the unsteady actuation showed that pulsed actuation periodically shifted the flow separation location resulting in the propagation of vortical structures in the recirculation region. The size of the vortical structures showed a dependence on the pulsed actuation timing parameters.

Ice accretion is a common issue on aircraft flying in cold climate conditions. The ice accumulation on aircraft surfaces disturbs the adjacent airflow field, increases the drag, and significantly reduces the aircraft’s aerodynamic performance. It also increases the weight of the aircraft and causes the failure of critical components in some situations, leading to premature aerodynamic stall and loss of control and lift. With this in mind, several authors have begun to study the thermal effects of plasma actuators for icing control and mitigation, considering both aeronautical and wind energy applications. Although this is a recent topic, several studies have already been performed, and it is clear this topic has attracted the attention of several research groups. Considering the importance and potential of using dielectric barrier discharge (DBD) plasma actuators for ice mitigation, we aim to present in this paper the first review on this topic, summarizing all the information reported in the literature about three major subtopics: thermal effects induced by DBD plasma actuators, plasma actuators’ ability in deicing and ice formation prevention, and ice detection capability of DBD plasma actuators. An overview of the characteristics of these devices is performed and conclusions are drawn regarding recent developments in the application of plasma actuators for icing mitigation purposes.

Flow field generated by a dielectric barrier discharge plasma actuator in quiescent air at initiation stage

Flow control is used in many aerodynamic applications that require additional energy/momentum for improved performance. Although flow control methods have been developed over many decades, the research to find t he best method for specific applications is still underway. To name a few, micro-satellite a ttitude control, wind turbine lift enhancement, aircraft landing gear flow control are important applications where conventional flow control methods are challenging. Among the most conventional methods, blowing and Dielectric Barrier Discharge (DBD) Plasma actuators have been proven successful in wide aerodynamic applications. Blowing controls proven applicable in wide regime often require high pressure compressed air source and on the other hand plasma actuators are relatively simple and ease in constru ction proved to be an excellent tool in low speed flow control applications. To minimize the ne ed for complicated high-pressure source and to utilize the relatively simple plasma actuato rs, the current paper focused on developing an integrated flow control method by combining blowing and DBD Plasma actuators. The experiments were designed to compare the individual methods with equal strength blowing and plasma actuators and then comparing with the combined method. The momentum addition with the combined method was then compared with blowing only method and observed that the combined method was able to reduce 63% blowing ratio to produce identical effects. The performance of plasma actuators in low pressure was also experimentally observed. Finally, the integrated me thod was applied on NACA 0025 airfoil with blow placed at 25% x/C and plasma actuator at 25.5% x/C locations respectively. Windtunnel tests were performed at freestream velocities of 3 m/s and 4.5 m/s with airfoil angle set at 10 degree. Results indicated 110% incr ease in airfoil near wall velocities for 3m/s when integrated control was applied.

Rotating stall is a well-known aerodynamic instability in compressors that limits the operating envelope of aircraft gas turbine engines. An innovative method for delaying the most common form of rotating stall inception using an annular dielectric barrier discharge (DBD) plasma actuator had been proposed. A DBD plasma actuator is a simple solid-state device that converts electricity directly into flow acceleration through partial air ionization. However, the proposed concept had only been preliminarily evaluated with numerical simulations on an isolated axial rotor using a relatively basic CFD code. This paper provides both an experimental and a numerical assessment of this concept for an axial compressor stage as well as a centrifugal compressor stage, with both stages being part of a low-speed two-stage axial-centrifugal compressor test rig. The two configurations studied are the two-stage configuration with a 100 mN/m annular casing plasma actuator placed just upstream of the axial rotor leading edge (LE) and the single-stage centrifugal compressor with the same actuator placed upstream of the impeller LE. The tested configurations were simulated with a commercial RANS CFD code (ansys cfx) in which was implemented the latest engineering DBD plasma model and dynamic throttle boundary condition, using single-passage multiple blade row computational domains. The computational fluid dynamics (CFD) simulations indicate that in both types of compressors, the actuator delays the stall inception by pushing the incoming/tip clearance flow interface downstream into the blade passage. In each case, the predicted reduction in stalling mass flow matches the experimental value reasonably well.

Rotating stall is a well-known aerodynamic instability in compressors that limits the operating envelope of aircraft gas turbine engines. An innovative method for delaying the most common form of rotating stall inception using an annular DBD (Dielectric Barrier Discharge) plasma actuator had been proposed. A DBD plasma actuator is a simple solid-state device that converts electricity directly into flow acceleration through partial air ionization. However, the proposed concept had only been preliminarily evaluated with numerical simulations on an isolated axial rotor using a relatively basic CFD code. This paper provides both an experimental and a numerical assessment of this concept for an axial compressor stage as well as a centrifugal compressor stage, with both stages being part of a low-speed two-stage axial-centrifugal compressor test rig. The two configurations studied are the two-stage configuration with a 100 mN/m annular casing plasma actuator placed just upstream of the axial rotor leading edge, and the single-stage centrifugal compressor with the same actuator placed upstream of the impeller leading edge. The tested configurations were simulated with a commercial RANS CFD code (ANSYS CFX) in which was implemented the latest engineering DBD plasma model and dynamic throttle boundary condition, using single-passage multiple blade row computational domains. The CFD simulations indicate that in both types of compressors the actuator delays the stall inception by pushing the incoming/tip clearance flow interface downstream into the blade passage. In each case, the predicted reduction in stalling mass flow matches the experimental value reasonably well.

Flow control using plasma actuator is a promising research field of aeronautical applications. Due to its low energy consumption, rapid response and simple construction, this actuator has been investigated in various aerodynamics problems, such as boundary layer flow control, drag reduction, lift enhancement, noise reduction, and flow separation control. In order to understand the controlling mechanism of plasma actuator, many researchers have been carried out some experiments on the plasma actuator characterization in quiescent air and obtained the evolution process of starting vortex induced by plasma actuator. But the plasma actuator always works under flow condition. Therefore, understanding the interaction process between the starting vortex and incoming flow is a key to promote this technology development. In this paper, the starting vortex induced by symmetrical Dielectric Barrier Discharge (DBD) plasma actuator in quiescent air or under flow condition was investigated using Particle Image Velocimetry (PIV). Compared with the asymmetrical DBD plasma actuator, the symmetrical plasma actuator adopted the whole metal plate model as the insulated electrode. Three layers of kapton film as dielectric material covered the testing model and the thickness of each layer was 0.05 mm. The copper foil which was 2 mm in width and 0.05 mm in thickness was mounted on the trailing edge of the plate and oriented along the spanwise direction to induce a wall jet in the streamwise direction. The input AC voltage was 8 kV p-p and the frequency of the power source was 3 kHz. The wind speed was 1 m/s. The results suggested that the symmetrical actuator produced one pair of counter-rotating starting vortexes on each side of upper electrode and the trajectory of the starting vortex core was shown to scale with t0.7 in quiescent air. Compared to the evolution law of starting vortex in still air, the development evolution and life time of starting vortex under flow condition was different due to the interaction influence between incoming flow and starting vortex. The breakdown time of downstream starting vortex was earlier and the location of the starting vortex core scaled with t0.45 under flow condition. Conversely, the life time of upstream starting vortex which was in the opposite direction of incoming flow was delayed. The incoming flow enhanced the upstream starting vortex's capability of promoting mixing and entraining high-momentum fluid into boundary layer, therefore the boundary layer became more energetic and capable of withstanding adverse pressure gradient. The jet effect and mixing function could be achieved by the symmetrical plasma actuator. These investigations laid the groundwork for flow control using DBD plasma actuator at high wind speed or high Reynolds number.

In this paper, the high speed airfoil is selected as the research object, by using the calculation method of fluid mechanics, the effect of dielectric barrier discharge (DBD) plasma actuator on the neutral gas is seen as the body force and introduced into the Navier-Stokes equation as the source term, then the numerical simulation experiment of the flow control by dielectric barrier discharge plasma actuator is carried out. The specific research of this thesis is as follows: Firstly, the plasma actuator is mounted at the front of the flow separation point and the lift-drag ratio is selected as the characterization; secondly, the two situations that the actuator works and doesn’t work are considered and then carrying out simulation experiment to study the effect on flow control of the plasma actuator; further, changing the angle of attack of the airfoil and then carrying out a series of simulation experiments under different circumstances; finally, the conclusion of the experiment is obtained so that it can be further analyzed. The calculation results show that: for the high-speed airfoil selected in this paper, the dielectric barrier discharge plasma actuator can suppress the flow separation phenomenon and increase the lift-drag ratio at the same angle of attack, and the smaller the angle of attack is, the larger the lift-drag ratio increment will be, the maximum lift-drag ratio increment is about 7.82%.

The present study provides a methodology to derive the local frequency response of flow under actuation, in terms of the magnitude of actuator induced perturbations. The method is applied to a dielectric barrier discharge (DBD) plasma actuator but can be extended to other kinds of pulsed actuation. The actuator body force term is introduced in the Navier-Stokes equations, from which the flow is locally approximated with a linear-time-invariant system. The proposed semi-phenomenological model includes the effect of both viscosity and external flow velocity, providing a system response in the frequency domain. A validity criterium is additionally devised for the estimation of the threshold frequency below which the developed approach can be applied. Analytical results are compared with experimental data for a typical DBD plasma actuator operating in quiescent flow and in a laminar boundary layer. Good agreement is obtained between analytical and experimental results for cases below the model validity threshold frequency. Results demonstrate an efficient and simple approach towards prediction of the response of a convective flow to pulsed actuation.