Low-temperature Plasma Generator Research Articles

Identification of the electromagnetic field of a laboratory bench with a low-temperature plasma generator

Identification of the electromagnetic field of a laboratory bench with a low-temperature plasma generator

Generation of low-temperature plasma by pulse-width modulated signals and monitoring of the interaction thereof with the surface of objects

The article discusses the use of pulse-width modulation signals to generate low-temperature atmospheric plasma in an inert gas environment. The results of studies of the energy consumption of a low-temperature plasma generation system depending on the duty rate, as well as the pulse repetition rate, are presented. The operating modes of the system have been established, in which a minimum of energy consumption is achieved. The issues of evaluating the interaction of plasma with objects based on the analysis of changes in signal parameters in the high-voltage circuit of the generator are also considered.

Low-Temperature Plasma Generators with Improved Energy and Resource Characteristics for Surface Treatment of the Technological Parts of Equipment

Low-Temperature Plasma Generators with Improved Energy and Resource Characteristics for Surface Treatment of the Technological Parts of Equipment

Analysis of Hydrogen Combustion in a Spark Ignition Research Engine with a Barrier Discharge Igniter

Hydrogen fuel is gaining particular attention in internal combustion engines. In addition to zero-carbon emissions, major advantages relate to its combustion characteristics, which allow a significant increase in thermal efficiency under ultra-lean operation and with very low NOx levels. The ignition system is one of the main technology enablers, as it determines the capability to control ultra-lean operations, avoid backfire phenomena, and/or reduce the risks of abnormal combustions. The latter results from hydrogen’s low ignition energy and it is associated with factors like high-temperature residuals, hot spots, and irregular spark plug discharge. The ACIS gen 2-Barrier Discharge Igniter excels in accelerating the initial flame growth speed by the generation of non-equilibrium low-temperature plasma, a strong ignition promoter for the combined action of kinetic and thermal effects. Moreover, its volumetric discharge facilitates combustion initiation on a wide region, in contrast to the localized ignition of traditional spark systems. In this work we present for the first time, to the best of our knowledge, experimental results showing the performance of a hydrogen engine with a low-temperature plasma discharge. Tests were conducted on a single-cylinder research engine, achieving ultra-lean conditions with cycle-to-cycle variability results below 2.5%. The analysis indicates that the H2-BDI combined solution is capable of accelerating the evolution of the flame front compared to traditional spark plugs, leading to a significant reduction in the cycle-to-cycle variability. A meticulous adjustment of the BDI control parameters further enhances igniter performance and contributes to a deeper understanding of the innovative approach proposed in this study.

Heat treatment of ground surface using an electric arc plasma generator

The article presents a generalization of the results of experimental and theoretical studies on the intensive thermal effect on the surface of foundations from cohesive soils (as opposed to deep heat treatment) using an electric arc generator of low-temperature plasma (plasmatron). A plasmatron with massive consumable electrodes made of borosilicated graphite and a wide "blurred" plasma torch was used for heat treatment. Physical and mathematical modeling of the thermal effect on the surface of clay soil by a moving high-temperature source has been performed. For the first time, a special installation was manufactured and experimental studies were carried out on the heat treatment of ground surfaces on the site with an electric arc plasma torch. It is established that the effective heat flux density reaches 2.5-.3.5 kW/cm2. The main part of the thermal energy for the used plasmatron enters the material due to radiant heat transfer. An analytical mathematical model of the temperature field of a three-dimensional semi-bounded body in the technological process under consideration is given by an essentially nonlinear boundary value problem for a nonlinear heat equation with nonlinear boundary conditions of the second kind. When solving thermophysical problems, the ground semi-bounded space was considered as a quasi-homogeneous medium having a constant initial temperature and initial thermophysical parameters that change in the process of temperature increase. The effective values of the thermophysical characteristics were determined on the basis of experimental data. Calculations and experiments have shown that the temperature boundary leading to significant changes in the structural properties of soils drops to a depth of 4-6 cm from the surface, despite the boiling of the ground melt with a temperature of 2500 ...2800 K on the ground surface. Therefore, a new technological principle of heat treatment is proposed, which consists in building up the ground melt in layers of 4-5 cm up from the initial surface. The impossibility of obtaining a positive effect even with the use of a powerful high-temperature source of exposure in the case of traditional surface heat treatment technology has been confirmed. The new plasma technology of surface heat treatment of ground surfaces to the stage of silicate melt allows to obtain a common layer of the required thickness. At the same time, the efficiency of surface heat treatment is significantly increased. The new technology of layer-by-layer surface deposition reduces cracking in the layer when the melt cools, but does not eliminate this negative process.

Load model and parameter measurement method of DBD for power supply design

Plasma is widely used in sterilization and disinfection, environmental treatment, and material surface modification. At present, the DBD load equivalent circuit model used in the design of dielectric barrier discharge (DBD) low-temperature plasma generator power supply mainly includes the nonlinear clamping model and linear resistance capacitance model, which have advantages and disadvantages in the research and application of DBD load. This paper focuses on the modeling and parameter acquisition method of the RC parallel DBD load linear model, adds measurement capacitance to the discharge load loop, and obtains RC parallel equivalent model parameters by Q-V and I-V Lissajous-Figure analysis. After the experimental data is processed, the simulation circuit model is built by MATLAB/SIMULINK, and the experimental results are compared with the simulation calculation results. They verify the feasibility of the DBD load parameter measurement scheme and comprehensively demonstrate that the DBD load linear resistance capacitance model has important guiding significance in the design of the DBD power supply.

Nonlinear Resonance Characteristics Analysis of DBD Load Based on State Plane Trajectory

Dielectric barrier discharge (DBD) loads and driving converters are widely utilized in low-temperature plasma generation, but their resonant tanks have typical nonlinear characteristics with control issues. The state plane trajectory analysis is used in this article to investigate the resonant behavior of a DBD load. The converter's working principle and state plane modeling are first discussed. The impact of a high-ratio step-up transformer with parasitic capacitance is then explored, and the updated trajectory model is examined. The DBD platform is created to verify the suggested model, and the associated experimental data are provided. The results of the experiment demonstrate that the discharge trajectory is a zone with distinct borders. The trajectory equations can be utilized to calculate the load equivalent capacitance, and the difference in the boundary equivalent capacitance represents the discharge intensity. The pattern of resonant frequency variation with discharge power is given. The impact mechanism of discharge phenomena and resonance characteristics is discussed.

Электродуговой синтез фотоактивных композиционных микрочастиц ZnO/TiO-=SUB=-2-=/SUB=-/Nb-=SUB=-2-=/SUB=-O-=SUB=-5-=/SUB=-

The method of electric arc synthesis of photoactive multicomponent composite microparticles on the example of a ZnO/TiO2/Nb2O5 system using a low-temperature plasma generator is proposed. Morphology and structural-phase composition of synthesized composite microparticles have been studied. Sold monstrated their record high photocatalytic activity (speed constant 128.6 · 10 − 3 min − 1) combined irradiation with ultraviolet and visible light

Генератор плазмы стримерного разряда

A description of the developed nanosecond high-voltage generator of low-temperature plasma based on a volume streamer discharge is given. Plasma is formed in a high-voltage three-electrode gap, one of which is at a floating potential. Plasma is formed when a special switch is triggered, which connects a floating potential electrode, pre-charged with positive streamers, to a grounded electrode. The operation of the generator in a pulse-periodic mode greatly simplifies its application in experimental studies. Its design and electrical circuit are described. The main electrical characteristics and parameters of streamer plasma radiation in the optical and ultraviolet ranges are presented. An example of a specific application of a generator plasma for solving problems of water purification from metal ions (by the example of manganese) using electric discharge technology is given. The use of a low-temperature plasma of a streamer discharge for experimental research in the field of propagation of an ultrahigh-frequency (microwave) signal in an ionized region of the atmosphere (thunderstorm cell) is described.

Results of studies of the direct current generator of low-temperature nitrogen-propane plasma

The effect of propane-butane addition to the plasma-forming gas on the state of cathodes with inserts made from lanthanated tungsten and hafnium is investigated. With a small propane addition (1%), the restorative effect of the insert material is noted, and the propane consumption has an upper limit when it is introduced together with the plasma-forming gas (no more than ∼ 73% of the plasma-forming gas consumption), below which the arc stability is not disturbed.

Energy characterization of an innovative non-equilibrium plasma ignition system based on the dielectric barrier discharge via pressure-rise calorimetry

A dielectric barrier discharge igniter (BDI) ensures engine stable combustion at lean and/or diluted conditions by the generation of non-equilibrium low-temperature plasma (LTP), strong promoter of the ignition, in a wide mixture volume.Beside this, a substantial amount of thermal energy is also released in the medium to enhance the chemical reactions of fuel oxidation. Therefore, the measurement of thermal energy is crucial to characterize the igniter capability to guarantee a robust combustion onset and it can be performed only in controlled environments.In this work, a Radio-Frequency BDI was tested via pressure-based calorimetry by evaluating the thermal energy released during the discharge in a controlled environment represented by a constant volume vessel. The corresponding thermal efficiency was evaluated as well. Pure nitrogen and air were exploited at engine-relevant pressure levels by varying the discharge features as its time duration and intensity (the latter by peak electrode voltage variation), to fully characterize the igniter behavior.Both media showed similar trends of absorbed and released energy but differences up to 50% were found for the latter. This trend was found to be linear, unexpectedly in contrast to the quadratic one showed by the LTP corona streamer-type igniter (CSI). Furthermore, the thermal energy dependence from pressure showed a change up to complete independence at a specific electrode value. To provide an explanation for such different behaviors, a comparative analysis between the diverse discharges of the two igniters was carried out. Moreover, by varying voltage and duration, the device was found to be able to release up to 60 mJ in the tested point with very low dispersion, essential to guarantee stable combustion ignition at challenging operating conditions for next-generation internal combustion engines.

Lowtemperature plasma generator for effective processing of materials

Low-temperature plasma is used in metallurgy for steel alloying by nitrogen, deoxidization of magnetic alloys, obtaining of steels with particularly low carbon content, metal cleaning of nonmetallic inclusions, desulfurization and other refining processes. The wide application of those technologies is restrained by absence of reliable generators of low-temperature plasma (GLP) with sufficient resource of continuous operation. As a result of studies, a universal generator of high-enthalpy plasma jet of various working gases was created. The generator has expanding channel of the output electrode with an efficiency of ~60 % for argon working gas and ~80% for nitrogen and air. It was shown that the developed generator of low-temperature plasma ensures formation of a weakly diverging (2α = 12°) plasma jet with a diameter D = 5–12 mm, an enthalpy of 5–50 kJ/g and a mass average temperature of 5–10 kK, at a full electric power of the arc discharge of 5–50 kW and a plasma-forming gas flow rate of 1–3 g/s. Results of the study of propane additions to the plasma-forming gas effect on the state of cathodes with inserts made of pure tungsten, lanthanum tungsten, and hafnium presented. It was shown that a small propane addition (1%) to the plasma-forming gas, results in reducing effect of the insert material. Study of the GLP operation at arc current 100A with addition to the working gas nitrogen maximum possible volume of propane, which don’t disturb stability of arc showed that for the developed plasma generator at the nitrogen flow rate ~0,45 g/s, the propane flow rate was ~0,33 g/s (not more than ~73 % of the plasma-forming gas). The created high-resource GLP with changeable electrodes enables to obtain at the exit a high-enthalpy plasma flow of various gases (argon, nitrogen, air) and can be a prototype of more powerful plasmotrons of various technological application, in particular for plasma metallurgy.

A low-temperature plasma generator working on nitrogen–propane mixture

A low-temperature plasma generator of a mixture of nitrogen and propane has been developed, with the possibility of supplying propane to the cathode region, to the arc burning zone, and also to the plasma stream below the arc binding zone. The maximum propane flow rate for a given plasmatron design and plasma-forming nitrogen flow rate, at which the arc is stable, was determined. When propane is supplied into the arc binding zone, the decay products are deposited mainly on the electrodes, and when it’s supplied to the anode after the arc binding, the decomposition products are deposited mainly at the anode exit. The study of the microstructure and analysis of the phase composition of the decomposition products of propane were performed.

Plasma Disposal in Problems of Ecology (Review)

The current state and issues of plasma disposal are discussed. Various types of plasma torches used for disposal, the technological schemes of existing plasma systems, a plasma torch with an expanding output electrode, equipment characteristics, diagnostic methods for the design of an effective low-temperature plasma generator, and the studying of the effects of a high-enthalpy plasma jet generated by a direct-current plasma torch on a solid target material are described. The results obtained via high-speed imaging, micropyrometry, laser profilometry, spectroscopy, and stereoscopy methods are presented. The data on spatial and temporal changes of the temperature field on the sample surface, the dynamics of material loss, and changes in the parameters (temperature and electron density, temperature of heavy particles) of the plasma-jet incident on the sample are analyzed. The collected theoretical and experimental results and engineering solutions can be used to design various low-temperature plasma generators with a power of up to 1 MW and higher.

Low-Temperature Plasma Generator with Direct Arc for Plasma Remelting

An efficient low-temperature plasma generator with direct arc for plasma remelting was developed and studied with direct and reverse polarity. It has an expanding nozzle channel and the remelted metal acts as a second electrode. An efficiency of ≈90% and a long service life with a current strength of up to 200 A were obtained. It is shown that the nozzle increases arc stability at an opening angle of 12°. It is established that a super-equilibrium nitrogen content (up to 0.22%) in the molten metal can be obtained.

The use of low-temperature plasma in a combined technology for the formation of wear-resistant boron-containing coatings

Combined technologies based on the use of concentrated energy fluxes, including low-temperature plasma and a pulsed electron beam, is currently considered to be an effective approach for surface modification of metals and alloys, cermet and ceramic materials. The purpose of the paper is to identify and analyze the patterns of changes in the elemental and phase composition, the state of the defective substructure, and mechanical properties of industrial steel Gr1J03502 subjected to combined treatment that includes plasma deposition of a powder coating based on the Ni-Cr-B-Si system and irradiation with an intense pulsed electron beam. The results obtained by optimizing the mode of the substrate surface fusion and the mode of powder deposition onto the molten surface of the substrate using low-temperature plasma generators of the original design are presented. It has been found that the optimum melting mode of the substrate surface is implemented with the following parameters of the plant: the feed rate is Vп = 50 … 150 mm/min, the distance is h1 = 30…100 mm, the scanning frequency is ω = 50 min−1, β = 75 … 90°, the amplitude is 90 … 100 mm, the plasmatron voltage is 160 V, the current strength is Im = 100 … 120 А. The optimal spraying conditions of the powders are as follows: h1 = 30÷50 mm; h2 = 100÷120 mm; β = 75÷90°; α = 45÷50°; ω = 50 min−1; Um = 140÷160 В; IS = 350÷400A; Im = 80÷100 A; GH (sprayed powder consumption) 0.8÷1 g/s. The characteristics of a plasma jet generated by an electric arc plasmatron are presented. The parameters of the electron beam are as follows: the energy of accelerated electrons is 18 keV, the energy density of the electron beam is 20 J/cm2 and 40 J/cm2, the pulse duration of the electron beam is 200 μs, the pulse repetition rate is 0.3 s−1, and the number of pulses is 10. It has been shown that plasma spraying of a powder coating leads to formation of a high relief surface containing micro and macropores, microcracks, and particles of the sprayed powder. Subsequent treatment of the modified surface with an intense pulsed electron beam of a submillisecond duration in the melting mode of the surface layer is accompanied by smoothing of the coating surface, saturation of the crystalline lattice of the steel surface with Ni, Cr, B, and Si atoms, formation of submicron-sized dendritic crystallization cells, precipitation of nanosized particles of the second phase, and formation of a quenching (martensitic) steel structure. Together, these transformations of the structure and phase composition of the material have led to a multiple increase in the microhardness of the surface layer with a thickness of up to 1500 mm.

Efficient Generator of Low-Temperature Argon Plasma with an Expanding Channel of the Output

To study the thermophysical, electrophysical and optical properties of argon, as well as the implementation of various plasma-chemical reactions, a direct-current generator of a high-enthalpy argon plasma jet with a self-adjusting arc length and an expanding channel of the output electrode has been developed. A comparative analysis of the electrophysical characteristics (current–voltage characteristics—CVC, efficiency) in the expanding and cylindrical channels of constant cross section was carried out. Electrical, calorimetric and spectral studies have shown that the created generator of low-temperature plasma provides the formation of a slightly divergent plasma jet of argon with a diameter of 5–8 × 10–3 m and enthalpy of 5–10 MJ/kg and a mass-average temperature at the outlet of the gas-discharge channel of 5–12 × 103 K with an electron concentration in the axial plasma of 1017 cm–3, the total electric power of the arc discharge 2–10 kW and the plasma-forming gas consumption rate of 1.5–3 × 10–3 kg/s. Depending on the initial conditions at a distance of 0–3 × 10–2 m from the nozzle section of the low-temperature plasma generator, the plasma flow velocity varies from 990 to 300 m/s.

Investigation of the effect of the sprayed material on the operating modes and thermal characteristics of the plasma torch

Authors have presented results of a research of influence of additives on characteristics of the plasmatron at their input to a plasma stream of the generator of low-temperature plasma. For a research of influence of napylyaemy material on the modes and thermal characteristics of the plasmatron by authors copper powder was entered by dispersion of 15 - 20 microns. By results of researches the characteristics providing an optimum operating mode of the generator of plasma have been chosen. It is noted that plasmatrons with the submitted characteristics are expediently used for receiving steam-gas streams in relation to technology of drawing sheetings.

Generator of the low-temperature heterogeneous plasma flow

A generator of low-temperature dc plasma with an expanding channel of an output electrode for gas-thermal spraying was designed and constructed. The delivery of the sprayed powder into the cathode and anode arc-binding zones or into the plasma jet below the anode binding was realized. The electrophysical characteristics of both the plasma torch and the heterogeneous plasma flow with Al2O3 powder are studied. It is shown that the current–voltage characteristic (CVC) of a plasma torch depends on the gas flow rate. If the flow rate varies from 1 to 3 g/s, the falling CVC becomes gradually increasing. The speed and temperature of the sprayed powder are determined.

Генератор низкотемпературной воздушной плазмы для исследования взаимодействия плазменной струи с термостойкими материалами

Генератор низкотемпературной воздушной плазмы для исследования взаимодействия плазменной струи с термостойкими материалами