Novel Technique to Determine SparkJet Efficiency

A plasma synthetic jet (PSJ) actuator (PSJA) with a Laval-shaped exit is investigated using a numerical method alongside a PSJA with a straight-shaped exit for comparison. The accuracy of the numerical method is first verified by comparing simulation results with experimental schlieren images and pressure measurement values. The performance of the PSJA with the Laval-shaped exit is then investigated in quiescent air. The results show that when the dimensionless energy ε > 5.06, the maximum exit velocity of the PSJA with the Laval-shaped exit becomes supersonic and is higher than that of the actuator with straight-shaped exit. The opposite is true when ε ≤ 5.06. The jet front velocity of the PSJ is much lower than the exit velocity, and no obvious improvement is seen when changing from the straight-shaped exit to a Laval-shaped exit due to the shock waves near the exit. Finally, the drag reduction effect of an opposing PSJ on a hemisphere in Ma3 flow is investigated. For a geometrically fixed PSJA, the flow field of a singled-pulsed opposing PSJ in Ma3 flow can be classified into three patterns according to the values of the maximum pressure ratio and ε: pattern 1 consists of only vortices and a slight change in the bow shock, pattern 2 consists of a typical long penetration mode (LPM) of the opposing PSJ, and pattern 3 consists of both a short penetration mode and a LPM. For PSJAs with both kinds of exits within a certain range, the average drag reduction increases with ε. However, when ε is higher than 48.02 for a Laval-shaped exit and 16.01 for a straight-shaped exit, the drag reduction effect decreases due to the rise in drag associated with the formation of the PSJ. The drag reduction effect associated with a PSJA with a Laval-shaped exit is significantly better than that of one with a straight-shaped exit when ε > 8. The optimal average drag reduction values, 25.82% and 20.55%, are obtained at ε = 48.02 and ε = 16.01, respectively, for a Laval-shaped exit and a straight-shaped exit.

Characteristics of plasma synthetic jet (PSJ) actuators driven by repetitive pulsed discharge have drawn much attention. In this paper, the PSJ actuator is composed of a pair of tungsten electrodes and a boron nitride cavity without a cap. The cavity has a diameter of 8 mm and volume of 400 mm'. The distance between two electrodes ranges from 1 mm to 4 mm. The PSJ actuator is excited by a homemade generator CMPC-40D, output pulse parameters of which are as follows: the maximum voltage of 30 kV, the rise time of 0.5 μs, the pulse width of 8 μs, the repetition rate ranges from 0to5 kHz. Effects of pulse repetitive frequency (PRF) and air gap spacing on the discharge characteristics of a single actuator are investigated. Experimental results show that the discharge voltage increases with the increase of the gap spacing but decreases with the increase of the PRF. During the ignition time, the discharge voltage falls to zero in a few nanoseconds and the current discharge is damped sinusoidal oscillation. We observe that the energy dissipation oscillates in time, for a total discharge energy of 2 to 9.9 mJ. The energy decreases with the increase of the PRF, but it increases with the increase of the gap spacing. Furthermore, three actuators in series connection are studied. Experimental results show that synchronous discharge could be achieved for three PSJ actuators.

No AccessTechnical NoteThree-Electrode Plasma Synthetic Jet Actuator for High-Speed Flow ControlLin Wang, Zhi-xun Xia, Zhen-bing Luo and Jun ChenLin WangScience and Technology on Scramjet Laboratory, National University of Defense Technology, 410073 Changsha, People’s Republic of China*Ph.D. Candidate, Science and Technology on Scramjet Laboratory; .Search for more papers by this author, Zhi-xun XiaScience and Technology on Scramjet Laboratory, National University of Defense Technology, 410073 Changsha, People’s Republic of China†Professor, Science and Technology on Scramjet Laboratory; .Search for more papers by this author, Zhen-bing LuoScience and Technology on Scramjet Laboratory, National University of Defense Technology, 410073 Changsha, People’s Republic of China‡Associate Professor, College of Aerospace Science Technology; (Corresponding Author).Search for more papers by this author and Jun ChenBeijing Space Physics Major Laboratory, 100076 Beijing, People’s Republic of China§Professor; .Search for more papers by this authorPublished Online:17 Mar 2014https://doi.org/10.2514/1.J052686SectionsView Full TextPDFPDF Plus ToolsAdd to favoritesDownload citationTrack citations ShareShare onFacebookTwitterLinked InRedditEmail About References [1] Cattafesta L. N. and Sheplak M., “Actuators for Active Flow Control,” Annual Review of Fluid Mechanics, Vol. 43, Jan. 2011, pp. 247–272. doi:https://doi.org/10.1146/annurev-fluid-122109-160634 ARVFA3 0066-4189 CrossrefGoogle Scholar[2] Moreau E., “Air Flow Control by Non-Thermal Plasma Actuators,” Journal of Physics D: Applied Physics, Vol. 40, No. 3, 2007, pp. 605–636. doi:https://doi.org/10.1088/0022-3727/40/3/S01 JPAPBE 0022-3727 CrossrefGoogle Scholar[3] Enloe C. L., McLaughlin T. E., VanDyken R. D., Kachner K. D., Jumper E. J. and Corke T. C., “Mechanisms and Responses of a Single Dielectric Barrier Plasma Actuator: Plasma Morphology,” AIAA Journal, Vol. 42, No. 3, 2004, pp. 589–594. doi:https://doi.org/10.2514/1.2305 AIAJAH 0001-1452 LinkGoogle Scholar[4] Shin J., Narayanaswamy V., Raja L. L. and Clemens N. T., “Characterization of a Direct-Current Glow Discharge Plasma Actuator in Low-Pressure Supersonic Flow,” AIAA Journal, Vol. 45, No. 7, 2007, pp. 1596–1605. doi:https://doi.org/10.2514/1.27197 AIAJAH 0001-1452 LinkGoogle Scholar[5] Li Y. H., Wang J., Wang C., An Z. Y., Hou S. L. and Xing F., “Properties of Surface Arc Discharge in a Supersonic Airflow,” Plasma Sources Science and Technology, Vol. 19, No. 2, 2010, Paper 025016. doi:https://doi.org/10.1088/0963-0252/19/2/025016 PSTEEU 1361-6595 CrossrefGoogle Scholar[6] Merriman S., Ploenjes E., Palm P. and Adamovich I. V., “Shock Wave Control by Nonequilibrium Plasmas in Cold Supersonic Gas Flow,” AIAA Journal, Vol. 39, No. 8, 2001, pp. 1547–1552. doi:https://doi.org/10.2514/2.1479 AIAJAH 0001-1452 LinkGoogle Scholar[7] Grossman K. R., Cybyk B. Z. and VanWie D. M., “Sparkjet Actuators for Flow Control,” 41st Aerospace Sciences Meeting and Exhibit, AIAA Paper 2003-0057, Jan. 2003 LinkGoogle Scholar[8] Anderson K. V. and Knight D. D., “Plasma Jet for Flight Control,” AIAA Journal, Vol. 50, No. 9, 2012, pp. 1855–1872. doi:https://doi.org/10.2514/1.J051309 AIAJAH 0001-1452 LinkGoogle Scholar[9] Narayanaswamy V., Raja L. L. and Clemens N. T., “Characterization of a High-Frequency Pulsed-Plasma Jet Actuator for Supersonic Flow Control,” AIAA Journal, Vol. 48, No. 2, 2010, pp. 297–305. doi:https://doi.org/10.2514/1.41352 AIAJAH 0001-1452 LinkGoogle Scholar[10] Belinger A., Hardy P., Barricau P., Cambronne J. P. and Caruana D., “Influence of the Energy Dissipation Rate in the Discharge of a Plasma Synthetic Jet Actuator,” Journal of Physics D: Applied Physics, Vol. 44, No. 36, 2011, Paper 365201. doi:https://doi.org/10.1088/0022-3727/44/36/365201 JPAPBE 0022-3727 CrossrefGoogle Scholar[11] Glezer A. and Amitay M., “Synthetic Jets,” Annual Review of Fluid Mechanics, Vol. 34, Jan. 2002, pp. 503–529. doi:https://doi.org/10.1146/annurev.fluid.34.090501.094913 ARVFA3 0066-4189 CrossrefGoogle Scholar[12] Haack S. J., Taylor T. M. and Cybyk B. Z., “Experimental Estimation of SparkJet Efficiency,” 42nd AIAA Plasmadynamics and Lasers Conference, AIAA Paper 2011-3997, June 2011. LinkGoogle Scholar Previous article Next article

Among the various active flow control techniques, Synthetic Jet (SJ) actuators represent a very promising technology due to their short response time, high jet velocity and absence of traditional piping, that matches the requirements of reduced size and low weight. Therefore, understanding in depth the basic physical aspects driving the operation of these actuators is a key point. A practical tool, employed for design and manufacturing purposes, consists in the definition of a low-order model, lumped element model (LEM), which is able to predict the dynamic response of the actuator in a relatively quick way and with reasonable fidelity and accuracy. The research activity focused by the present author has tried to tackle different aspects to achieve various goals. A major task has concerned the development of LEMs to predict the behavior of two types of actuators: piezo-driven SJ and Plasma Synthetic Jet (PSJ) actuators. These models share the same philosophy: they represent valuable tools useful not only for design purposed, but also to obtain useful insights on the devices performances. A second crucial task has consisted in the design, manufacturing and characterization of various prototypes, which have been used to validate LEMs results. As an additional task of the research activity, applications both in automotive and aerospace fields have been considered. As regards the piezo-driven synthetic jets, the main activity was concerned with the extension of an already available lumped-element model in order to: derive a non-dimensional form of the governing equations; identify the main design quantities; estimate the device performances; shed light on the actuator energy efficiency with reference to the different stages involved in the operation process. Several issues have been faced including the technology required for bonding the piezo-element over the metallic shim (so as to realize the so-called diaphragm), the design and manufacturing of the experimental mock-up, the production of the different parts of the device, the post-processing analysis. A very interesting application of the piezo-driven SJ technology, which can have outcomes in the automotive sector, has regarded the manipulation of a continuous water spray. Experimental data, taken within a chamber test rig at two injection pressures, for different SJ positions, have been acquired. Starting from the flow field velocity distributions, detected with Particle Image Velocimetry (PIV), the effective influence region of the jet on the spray has been computed through a T-Test algorithm and corroborated by a vorticity analysis. Another innovative LEM, able to predict the temporal evolution of the main fluid-dynamic variables involved, has been developed for PSJ actuators. It is fully based on the gasdynamics equations, it includes viscous losses as well as radiative and convective heat transfer mechanisms at walls, and it considers real gas effect for air. OpenFOAM numerical computations have been carried out to perform a first calibration of the lumped model through the determination of key fitting parameters. Results for both single pulse mode and repetitive working regimes have been analyzed, providing insights on the major actuation characteristics. To validate the LEM model, a home-made PSJ actuator has been designed and manufactured. The overall experimental mock-up has been also designed, together with the control electrical system. Experimental measurements of the jet velocity, obtained with Hot-wire anemometer and Pitot tube, have completed the actuator characterization and have allowed the model validation.

Plasma synthetic jet actuator array driven by a programmable triggered Marx high-voltage generator

A three-electrode high-energy plasma synthetic jet (PSJ) actuator was used for shock wave control. This actuator is an enhanced version of the two-electrode actuator as a high-voltage trigger electrode is added to increase the cavity volume and the input energy while retaining a relatively low disruptive voltage. The electrical properties were studied using current-voltage measurements, and the energy consumption was calculated. To assess the jet strength, the penetration of PSJ was compared with empirical values, and the results show that the momentum flux ratio of PSJ for a capacitance of 0.96, 1.6, and 3 μF was approximately equal to 0.6, 1.0, and 1.3, respectively. The interaction of PSJ with shock waves was acquired using high-speed shadowgraph imaging. The shock was generated by a 25° compression ramp in Mach 2 flow, and PSJ actuator was placed up-stream of the compression ramp. Under the action of PSJ, the strength of the shock was notably weakened, and the near-wall part of the shock was entirely eliminated. The results show the good control effect of the three-electrode high-energy PSJ in high-speed flow.

Experimental characteristics of a two-electrode plasma synthetic jet actuator array in serial

Discharge and electrothermal efficiency analysis of capacitive discharge plasma synthetic jet actuator in single-shot mode

The plasma produced by a pulsed generator is an efficient tool for an airflow control. In this paper, a nanosecond pulsed generator constructed with a fast solid-state switch is designed for triggering synchronous discharges in plasma synthetic jet (PSJ) actuators connected in series. The generator delivers high-voltage pulses with a peak voltage varying from 0 to 20 kV, a rise time of 20 ns, a full-width at half-maximum of 200 ns, and a wide range of pulse-repetition rate varying from 0 to 5.5 kHz. It is proved that this generator is able to trigger synchronous discharges in three PSJ actuators in atmospheric air with a peak discharge current more than 90 A and a deposited energy per pulse of 39 mJ. A schlieren system is used to observe the airflow dynamics, which shows the high synchronization among the three PSJ actuators with a time triggering delay of about 20 ns. The synchronous operation of three PSJ actuators produces a plasma jet with a maximum velocity of 60 m/s and a precursor wave with a velocity of 350 m/s.

The effect of a novel spark-plug plasma synthetic jet actuator on the performance of a PEM fuel cell

The plasma synthetic jet actuator (PSJA), also named as sparkjet actuator, is a special type of zero-net mass flux actuator, driven thermodynamically by pulsed arc/spark discharge. Compared to widely investigated mechanical synthetic jet actuators driven by vibrating diaphragms or oscillating pistons, PSJAs exhibit the unique capability of producing high-velocity (>300 m/s) pulsed jets at high frequency (>5 kHz), thus tailored for high-Reynolds-number high-speed flow control in aerospace engineering. This paper reviews the development of PSJA in the last 15 years, covering the major achievements in the actuator working physics (i.e., characterization in quiescent air) as well as flow control applications (i.e., interaction with external crossflow). Based on the extensive non-dimensional laws obtained in characterization studies, it becomes feasible to design an actuator under several performance constraints, based on first-principles. The peak jet velocity produced by this type of actuator scales approximately with the cubic root of the non-dimensional energy deposition, and the scaling factor is determined by the electro-mechanical efficiency of the actuator (O(0.1%–1%)). To boost the electro-mechanical efficiency, the energy losses in the gas heating phase and thermodynamic cycle process should be minimized by careful design of the discharge circuitry as well as the actuator geometry. Moreover, the limit working frequency of the actuator is set by the Helmholtz natural resonance frequency of the actuator cavity, which can be tuned by the cavity volume, exit orifice area and exit nozzle length. In contrast to the fruitful characterization studies, the application studies of PSJAs have progressed relatively slower, not only due to the inherent difficulties of performing advanced numerical simulations/measurements in high-Reynolds-number high-speed flow, but also related to the complexity of designing a reliable discharge circuit that can feed multiple actuators at high repetition rate. Notwithstanding these limitations, results from existing investigations are already sufficient to demonstrate the authority of plasma synthetic jets in shock wave boundary layer interaction control, jet noise mitigation and airfoil trailing-edge flow separation.

Plasma synthetic jet (PSJ) has a wide application prospect in flow separation suppression and boundary layer control. Comparing with traditional control methods, synchronous discharges of PSJ with high repetition frequency and high energy could achieve a better flow control effect because it can meet multi-angle, wide-range and long-time flow control requirements. In this paper, a microsecond-pulse power supply for synchronous discharges of three plasma synthetic jet actuators (PSJA) is developed. Parameters of output pulses are as follows: the maximum voltage pulse is 10 kV, the pulse repetition rate is 1000 Hz and the full width is 15 μs. The generator can withstand a discharge current with an amplitude of 320 A and a discharge energy of 150 mJ. The electrical characteristics of the synchronous discharges of PSJAs including the voltage-current waveforms, discharge images and Schlieren images are investigated. The experimental result shows that the microsecond-pulse generator could sustain three discharge channels in PSJAs when the output voltage is 10 kV. These discharge channels have preferable performance in synchronicity when the repetition frequency is 1000 Hz. Furthermore, the Schlieren images show that the power supply can sustain three PSJAs with a maximum jet velocity of up to 150 m/s.

If the actuator of the plasma synthetic jet (PSJ) operates continuously under a high frequency, the performance of the actuator will become worse than it is in single pulse test. This is because the air in the cavity cannot fully recover to the original state before the next cycle starts. Therefore, the characteristics of the plasma synthetic jet during continuous operation, rather than during a single pulse, need to be studied carefully. In this paper, simulated flow fields of the continuously working PSJ are analyzed. It is found that the time-averaged results of the PSJ are self-similar, however, the instantaneous results are only self-similar when y is less than y0.5. Moreover, the effects of the dominant parameters, such as the maximum temperature, cavity shape and the operating frequency, on the performance of the PSJ actuator under stable operating condition are discussed. The maximum temperature is the most important parameter for the PSJ actuator. Actuator performance improves when the maximum temperature increases. In contrast, the frequency has little influence on performance, and the PSJ actuator is shown to perform well under a wide range of frequencies. This is more beneficial for active flow control compared with the synthetic jet actuator driven by the piezoelectric patch. The shape and the volume of the cavity can also influence the performance of the actuator. As the volume of the cavity becomes smaller, the duration of the spurt period is reduced.

This paper reviews the background to and the current status of analyses developed to address the problem of icing on aircraft. Methods for water droplet trajectory calculation, ice accretion prediction, aerodynamic performance degradation and an overview of ice protection system modelling are presented. The paper addresses the issues involved in the development of icing analyses including problem formulation and assumptions, solution techniques, validation and the incorporation of empirical inputs where a purely theoretical approach is not feasible. Results are presented to illustrate the capabilities of the analyses when applied to practical design problems. Recommendations are made for further research.

In the field of flow control research, oblique jets are known to offer several advantages over vertical jets. To gain a comprehensive insight into the flow field characteristics of a plasma synthetic jet actuator with an oblique-slot exit, the related experiments are conducted. The experiment employed high-speed schlieren imaging techniques and electrical parameter measurements to acquire the flow field characteristics and discharge properties of the oblique-slot actuator, followed by a comparative analysis with a vertical circular orifice actuator. The oblique-slot plasma synthetic jet exhibits a wall-attaching effect and asymmetric flow characteristics, which differ from those of the vertical circular orifice actuator. The actuator generates a wall jet with an initial velocity of 389.5 ± 15.08 m/s, effectively propelling the fluid within the boundary layer. The Mach number of the precursor shock wave in the direction of the jet reaches 1.59, but decreases to just 1.02 in the opposite direction. Over a period in the range of 10–70 μs, the Froude number of the plasma jet decreases from 1841 to 238. The dominant role of the inertial force gradually weakens, while the influence of buoyancy increases, causing the jet boundary to move upward. The oblique-slot jet configuration represents a typical planar jet, exhibiting superior flow control uniformity compared with the vertical circular orifice jet. The results indicate that the high-speed oblique-slot plasma synthetic jet actuator designed in this study possesses distinct advantages over vertical circular orifice actuators for high-speed fluid flow control.