Pulsed Plasma Generator Research Articles

Thermoacoustic stabilization of a sequential combustor with ultra-low-power nanosecond repetitively pulsed discharges

This study demonstrates the stabilization of a sequential combustor with Nanosecond Repetitively Pulsed Discharges (NRPD). Sequential combustors offer advantages such as enhanced fuel flexibility and broader operational range compared to the conventional combustors. However, thermoacoustic instabilities limit their potential. While passive control strategies like Helmholtz dampers have been utilized, active control methods have been hindered by the lack of robust actuators for harsh conditions with sufficient control authority. This study demonstrates successful suppression of instabilities using NRPD in a lab-scale atmospheric sequential combustor, even at low plasma power (1.1 W, about 1.5×10−3 percent of thermal power of 73.4 kW). We also examine the effect of pulse repetition frequency and plasma generator voltage on NO emissions and the sequential flame topology. Notably, higher plasma power can further enhance suppression, albeit with a slight increase in NO emissions. However, the highest plasma power in our study (81 W, 1.1×10−1 percent of flame thermal power) shows a slight improvement in acoustic suppression while significantly elevating NO emissions. Intriguingly, specific plasma parameter combinations can excite another acoustic mode, necessitating further exploration for optimized control. This pioneering study highlights the potential of ultra-low-power plasma-based thermoacoustic control in sequential combustors, paving the way for enhanced stability and performance.

Evolution of tungsten degradation under different cyclic ELM-like high heat flux plasma

A millisecond pulsed repetitive plasma generator based on capillary discharge is utilized to produce ELM-like heat load. Based on this device, the evolution of tungsten degradation under heat loads with different heat fluxes, pulses, and frequencies is investigated. With an increase of heat flux and pulse, the tungsten surface experiences an increasing melting and cracking damage. The cross-sections of samples are analyzed to investigate the mechanisms of crack formation and propagation. There are numerous small cracks of ∼20 μm length in the melting layer, which may extend to form the primary cracks under further stress. Among the primary cracks, the central crack in the heat-affected layer initially propagates perpendicularly to the surface and grows parallel to the surface, converging with the edge cracks under cyclic high heat loads. And the microstructures near cracks also reveal the mechanism of crack formation, including the intergranular primary cracks and partial transgranular secondary cracks. This work provides a novel approach to simulating ELM-like thermal load and corresponding tungsten cracking behavior under repetitive high heat flux plasma.

The partial electrical breakdown mechanism by high voltage electric pulses in multi-fractured granite

High-voltage electric pulse (HVEP) technology has currently become a new efficient rock breaking method. In order to reveal the influence of internal fracture characteristics of heterogeneous granite on electric pulse rock breaking, the two-dimensional numerical model of multi-physical field coupling electrical breakdown of fractured rock is established, which the high-voltage electric pulse plasma generation in multi-fractured heterogeneous granite is realized from the coupling of circuit field, current field, breakdown field, heat transfer field and solid mechanics. This paper analyzes the influence of fracture porosity, fracture types and granite heterogeneity on the electrical breakdown of rock (i.e. the formation of plasma channel inside the rock). At the same time, the two-dimensional numerical model of electrical breakdown parameters, which considers the circuit structure parameters of the pulsed tool, the initiation and development of the electrical breakdown, the dependence between electrical breakdown intensity and time, and rock heterogeneity, are analyzed. The simulation results indicate that with the heterogeneity H of granite changing, the plasma channel inside the rock samples are different, while the time required for breakdown t and rock breaking volume Vrock of rock samples with different heterogeneous H will show obvious fluctuations; among the rock samples with different heterogeneity H, existing a single crack requires a longer breakdown time and the extreme value of the internal conductivity is also significantly larger. And then, the formation of plasma channel is directional selective, extending towards fractures and the weak electrical breakdown intensity. With the dip angle of the fracture increasing, the required breakdown time increases accordingly, and conversely, the broken volume decreases accordingly. The larger porosity of fracture is, the larger broken volume and the shorter required break down time of the rock sample. Furthermore, with the continuous action of electric pulses, multi-fractured rock form interpenetrating plasma channels to improve the rock breaking efficiency. The research results can provide help and theoretical support for optimization of electric pulse rock breaking parameters and the development of electric pulse drilling technology.

Electric discharge generator of long-lived plasma formations in atmospheric pressure air

The paper presents the results of a study of the developed pulsed plasma generator based on the cylindrical foil electric explosion. The generator is used to form large-scale toroidal plasma vortices in atmospheric air. The influence of the specific stored energy on the phase composition of the plasma flow and the lifetime of plasmoids using a high-speed camera was studied. It was found that large condensed particles in the flow do not participate in the vortex motion and cause the destruction of plasma vortices. The formation conditions of stable plasma vortices were determined.

Study of Heterogeneous Plasma Created by Magneto-Plasma Compressor and Erosive Capillary Discharge

Magneto-plasma compressor with a pulsed capillary erosive plasma generator (MPC-EP) has been designed, manufactured and tested at the first time. This MPC-EP was used to study the physical properties of a high-energy long-lived heterogeneous plasma (ELHP) created by pulsed capillary erosive plasma generator (EP) at the wide range of pressure and temperature. The results of measurements of the parameters of the shock wave created by the MPC-EP, as well as optical spectroscopy and soft X-ray spectroscopy are presented.

Temporal characterization of fundamental plasma parameters in pulsed liquid electrode plasma (LEP) optical emission spectrometry

The fundamental characteristics of liquid electrode plasma (LEP), a pulsed plasma source for optical emission spectrometry, were investigated. Two distinct phases were observed during the process of pulsed plasma generation, namely bubble generation and active plasma discharge. The ionization efficiency of the LEP, with Mg as a representative analyte, was gauged from the ratio of Mg II 279.553 nm to Mg I 285.213 nm emission and was found to increase from about 5% to 20% in a close-to-linear fashion with the discharge voltage from 800 V to 1200 V. The Mg II/Mg I ratio of the LEP was 2.5 to 3 orders of magnitude less than that typically offered by an inductively coupled plasma (ICP) but was comparable to other solution-based glow discharges. It was found that an off-time interval of more than 150 ms between successive discharge pulses was required to obtain a stable pulse-to-pulse discharge current. Temporally resolved emissions of Mg II 279.6 nm, Mg I 285.2 nm, Fe I 373.5 nm, OH band head at 306 nm, and Hα line at 656.3 nm showed that the background species (OH band and Hα line) reached their maximum emission intensities at around 0.5 ms to 0.7 ms with respect to the onset of the discharge pulse whereas the maximum emissions were observed between 0.7 ms to 0.9 ms for analyte species (Mg and Fe lines). The electron density observed in the present work was in the range from 5.7 × 1015 cm−3 to 8.2 × 1015 cm−3, which was similar to those found in an analytical ICP. The temporal averaged OH rotational temperature was 3300 K, which was comparable to the values of an analytical ICP and solution-based glow discharges. By contrast, the temporally averaged Fe I excitation temperature was around 8900 K, which was even higher than that of an analytical ICP and roughly triple the values obtained by techniques based on glow discharge of liquid samples.

Вклад академика Ф.Г. Рутберга в электрофизику и энергетику (к 90-летию со дня рождения)

The article is devoted to the memory of Academician F.G. Rutberg and his scientific achievements in the field of electrophysics and electric power engineering. His works made a significant contribution to the study of powerful discharges in dense gaseous media, nonequilibrium processes in plasma flows, processes in complex electrodynamic systems, as well as to the development and construction of electrophysical equipment for various purposes. Under his leadership, pulsed and short-term high-capacity power supply systems with inertial energy storages, electric-discharge hyperspeed accelerators of bodies with limiting parameters, stationary powerful three-phase AC plasma generators, and powerful pulsed plasma generators were created. Plasma-chemical technologies for producing synthesis gas and hydrogen to obtain environmentally clean renewable energy, as well as liquid fuels, have been developed. Technologies for processing and destructing various types of waste have been elaborated, and equipment for bactericidal water purification by pulsed discharges and for development and production of oxide nanostructures has been created.

A numerical study on laboratory plasma dynamics validated by low current x-pinch experiments

The computational study of x-pinch plasmas driven by pulsed power generators demands the development of advanced numerical models and simulation schemes, able to enlighten the experiments. The capabilities of PLUTO code are here extended to enable the investigation of low current produced x-pinch plasmas. The numerical modules of the code used and modified are presented and discussed. The simulations results are compared to experiments, carried out on a table-top pulsed power plasma generator implemented in a mode of producing a peak current of ∼45 kA with a rise time (10%–90%) of 50 ns, loaded with Tungsten wires. The structural evolution of plasma density is studied and its influence on the magnetic field is analyzed with the help of the new simulation data. The simulated areal mass density is compared with the experimentally measured dense opaque region to enlighten the dense plasma evolution. In addition, the measured areal electron density is compared to the simulation results. Moreover, the new simulation data offer valuable insights to the main jet formation mechanisms, which are further analyzed and discussed in relation to the influence of the J × B force and the momentum.

Investigation of the time interval of plasma generation for a high repetition rate laser ion source.

To apply a laser ion source that generates a high-intensity pulsed beam to high-dose applications, such as ion implantation, a high repetition rate operation with a short pulse interval is required. However, when the pulse interval is shortened, there is a concern that a plasma, which is different from a single pulse plasma generation, may be formed due to the interaction between the preceding and following pulses. We investigated the time interval in which plasma pulses are generated without pulse-to-pulse interaction using a laser ion source with two lasers. In the experiment, a graphite target was irradiated by two laser beams (1064-nm wavelengths) with the same pulse widths (5.4 ns) and energies (15 mJ, 30 mJ, and 45 mJ) at different time intervals ranging from 1000 μs to 0 µs, and the time integrated value corresponding to the total charge amount was calculated from the measured time-of-flight signal of the generated carbon ion current. It was observed that the total charge did not change when the time interval was as low as approximately 100 µs, and the total charge rapidly decreased when the time interval was below approximately 100 µs. Thus, it was determined that the interaction occurs within a time interval of approximately 100 µs.

High-voltage pulsed plasma generation with frequency control for streamer initiation in liquid phase

Plasma streamers are produced utilizing a high-voltage pulse generator with variable peak-potential difference for up to 20 kV with 200 mJ of pulse energy, 15 microsecond rise time, and adjustable pulse frequency in the range between 1 Hz and 1.5 kHz for corona streamer initiation in liquid phase. The pulsed plasma generator is tested in a pin-to-plate electrode geometry in a sealed reactor filled with deionized water. Streamer geometry information and the resulting electrical waveforms are presented, in addition to quantitative description of temperature variation with respect to pulse frequency and electrical power applied. It is observed that consistent streamers without significant variation in length are obtained within the frequency range analyzed.

Study of gas flow in a discharge chamber of a pulse plasma generator

This paper focuses the features of computer simulation of gas flow in a gas-discharge chamber of a pulsed plasma generator using the STAR-CCM + program. The influence of the method of supply and consumption of plasma-forming gas on the output parameters of the plasma generator is shown.

Apparent reduced electric field control with nanosecond pulse width in a DC discharge for nitrogen vibrational excitation

A non-self-sustaining DC (NSS DC) discharge plasma source with an axial field geometry has been developed for emerging plasma applications on nitrogen fixation. This plasma source, composed of a pulse plasma generator and a DC power supply, enables external control of apparent reduced electric field (E/N). Pulse width extension, our proposed approach, is found to be a key parameter to achieve appropriate E/N for efficient nitrogen vibrational excitation leading to the nitrogen fixation processes. Owing to the pulse width modulation approach in the NSS DC discharge, the apparent E/N control up to 3 Td is achieved at 0.2 atm nitrogen.

Reduction of Iridium Loading to the Minimum Level Required for Water Oxidation Electrocatalysis without Sacrificing the Electrochemical Stability

Iridium(Ir)-based electrocatalyst exhibits an optimal trade-off between catalytic activity and stability and thus is considered one of the most promising candidates in acidic water oxidation electrocatalysis. Due to its cost and scarcity, however, the sparing use of it has become the top priority in this field. In this contribution, we demonstrate the immense potential of coaxial arc plasma deposition (APD) as catalyst coating technology for water oxidation. Taking advantage of controllable pulsed plasma generation with high kinetic energy, APD enables the rigid coating of uniform and ultrathin Ir films on the substrate surface. The strong anchoring propensity of the films is observed, and thereby, unless the Ir loading is too little to overcome the catalyst loss and dissolution caused during repetitive electrochemical redox cycling for full electrocatalyst activation, the electrocatalytic performance of the films remains unaffected even after thousands of cyclic water oxidation testing. In this regard, w...

A Simple Design Erosional Plasma Gun Made of a Coaxial Cable with Polyethylene Insulation

A compact pulsed plasma generator of simple design made of a coaxial cable with polyethylene insulation has been described. A plasma gun generates a cloud of carbon-hydrogen plasma with an electron density of more than 1013 cm–3, including in a magnetic field produced of up to 500 G and also in the presence of the background plasma with a density of about 1012 cm–3, which is produced by an independent source. The high resource of the gun and stability of plasma parameters from one pulse to another allows using such a gun in laboratory experiments simulating dynamic processes in space.

Простейшая эрозионная плазменная пушка из коаксиального кабеля с полиэтиленовой изоляцией

Abstract—A compact pulsed plasma generator of simple design made of a coaxial cable with polyethylene insulation has been described. A plasma gun generates a cloud of carbon-hydrogen plasma with an electron density of more than 10^13 cm^–3, including in a magnetic field produced of up to 500 G and also in the presence of the background plasma with a density of about 10^12 cm^–3, which is produced by an independent source. The high resource of the gun and stability of plasma parameters from one pulse to another allows using such a gun in laboratory experiments simulating dynamic processes in space.

Application of Solution Plasma Surface Modification Technology to the Formation of Thin Hydroxyapatite Film on Titanium Implants

Hydroxyapatite (HA) coatings on titanium implants enhance rapid bone formation around the implant due to their osteoconductive property. The present study aimed to achieve a thin and uniform HA film coating on titanium implants by solution plasma treatment (SPT). Commercially pure titanium and porous titanium disks were employed. A pulse plasma generator was used on the disks for 30 min. Morphologic and crystallographic features of the deposited films were examined by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). To evaluate the wettability of the disks, water droplet (20 µL) surfaces were measured using a contact angle analyzer. The initial attachment of osteoblast-like cells (MC3T3E1) on the titanium substrates before and after solution plasma treatment was evaluated by counting the number of attached cells after incubation for 4 h. After immersion in the mineralizing solution for up to seven days, no crystals were observed on the polished-Ti surface. A more uniform and dense precipitation of round and grown crystals with diameters of approximately 1–5 µm was observed on Ti-SPT. XRD clearly showed that the precipitated crystals on titanium disks were HA. The contact angle of the polished-Ti increased with time (θ = 37°–51°). The surface of the Ti-SPT remained hydrophilic (θ ˂ 5°) after up to 30 days of aging. The number of attached cells on the Ti-SPT after aging for 30 days remained above 85% of that on the Ti-SPT without aging. SPT in a mineralizing solution can be used to acquire a homogenous precipitation of HA on porous-surfaced titanium implants.

SiO2 films as heat resistant layers for protection of expandable polystyrene foam from flame torch–induced heat

Currently, polymeric insulation materials are widely used for energy saving in buildings. Despite of all benefits, these materials are generally sensitive to heat and highly flammable. This work discusses possibility to improve heat resistance of expanded polystyrene (EPS) foam using thin silicon dioxide (SiO2) films deposited by magnetron sputtering technique. In order to increase surface energy and adherence of SiO2 thin films to substrate EPS was plasma pretreated before films’ depositions using pulsed DC plasma generator for 40 s in argon gas. SiO2 formation was done in reactive argon and oxygen gas atmosphere. Laboratory made equipment was used for flame torch–induced heat resistance experiments. Results showed that silicon oxide films remains stable during heat resistance experiments up to 5 s and fully protects polystyrene (PS) substrate. Films are relatively stable for 30 s and 60 s and partially protect PS from melting and ignition. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analysis confirmed that SiO2 layer, which is distributed uniformly on the EPS surface, could work as a good heat resistant material.

Generation of Hydrogen Peroxide in Gas Bubbles Using Pulsed Plasma for Advanced Oxidation Processes

Advanced oxidation process (AOP) is one of the most effective methods of decomposing persistent organic pollutants in water using OH radicals. The O3/H2O2 method is widely used to form OH radials for AOP; however, this method needs a continuous H2O2 supply. The continuous generation of H2O2 using plasma is appropriate for the O3/H2O2 method, since plasma is readily available anywhere electricity is. This paper presents suitable conditions for pulsed plasma generation in oxygen bubbles for effective and rapid formation of H2O2. The experimental results show that low-voltage-driven and long pulsewidth plasma is best for H2O2 generation. The highest H2O2 generation rate of 61.8 mg/h and energy yield of 2.1 g/kWh were obtained at 2.5-kV voltage, 4-kHz pulse frequency, and 1- $\mu \text{s}$ pulsewidth.

Light-curing polymers for laser plasma generation

Solid rather than liquid media are used in pulsed laser plasma generators despite sophisticated transportation and dosing system need for a long-term operation. Liquid media could be more preferable due to transfer and dosing (down to 10-14 L) being well developed, but plasma generation of those results in intense droplet formation and kinetic energy losses. Combination of liquids transportation advantages and solids plasma generation efficiency might resolve this trade-off. Liquid-to-solid transition can be induced by cooling down to sublimation temperature, thermo-, photo- or electron induced polymerization (curing). Light cured polymers seem to be very useful as active media for plasma generators, since they can be solidified very fast (ca. 30 ms) just before impact. We considered experimentally several UV- curing polymer and mixtures ablation regimes and supply schemes for laser plasma generation. The best results were obtained for liquid polymer at high-power pulsed irradiation matching curing optimum wavelength.

Pulse Plasma Surface Thermostrengthening of Machine Parts

The paper presents a pulse plasma generator for surface hardening of parts. The given equations allow to calculate the parameters of the pulse plasma generator to ensure the specified quality indicators of the hardened zone.