Nitrogen Arc Research Articles

A new formula for the rotational velocity of magnetically drivenarcs

A new, more precise and simple semi-empirical formula has beenobtained for the prediction of the rotational velocity of magnetically drivenarcs in air and nitrogen. The formula is based on the balance between themotive Lorentz force and the aerodynamic drag force and takes into accountchanges in the gas density value due to the arc rotation and the axial gasvelocity. The formula enables the calculation of the arc velocity in electricarc heaters as a function of current, magnetic field, axial gas velocity andgas density. Experimental results are presented for arcs in air and nitrogen,for currents in the range 100-1760 A, magnetic induction values of0.005-3.9 T and axial gas velocities of 0.2-33 m s-1. The formula canbe useful for the study of cold electrode erosion and engineering calculationsof electric arc heaters.

Residual stress in TiN film deposited by arc ion plating

TiN films were deposited on aluminum and stainless steel substrates by arc ion plating (AIP). Bias voltages, nitrogen gas pressures and arc currents were changed to examine their role on the hardness and residual stress of a TiN film. Vickers microhardness tests revealed high hardness value (HV = 2250–2500) which depends on both nitrogen gas pressures and arc currents. From the X-ray diffraction pattern, it was found that the crystal orientation of the TiN film markedly varied with the bias voltage. Residual stresses in the TiN film were measured by the two-exposure X-ray stress analysis as a function of the nitrogen gas pressure, arc current. Very high compressive residual stresses, −5 GPa in the films on aluminum substrates and −7 GPa in the film on a stainless steel substrate, were observed.

Preparation of ultrafine composite particles of Ag+AlN/Al by nitrogen plasma metal reaction

Abstract Pure Ag and Al were melted simultaneously by nitrogen arc plasma in a common chamber using two electrodes. Ultrafine composite particles consisting of fcc-Ag, fcc-Al and hexagonal AlN are obtained together with 17% mixture of hexagonal Ag 2 Al ultrafine particles. Ag, Al and AlN ultrafine particles are formed through the condensation of element vapor, but Ag 2 Al ultrafine particles are formed through a solid reaction between Al and Ag ultrafine particles.

アーク・イオンプレーティング法により形成されたＴｉＮ皮膜のＸ線残留応力測定

Surface roughness, hardness and residual stress of TiN films deposited on stainless steel substrates by an arc ion plating method were examined by changing arc current and nitrogen gas pressure, respectively. The TiN films have an average roughness of about 0.1 to 0.3μm, while the surface roughness decreases with increasing nitrogen gas pressure. Vickers micro hardness tests revealed high hardness (HV 1650-2500) whose value depended on nitrogen gas pressure and arc current, respectively. X-ray photoelectron spectroscopy analysis showed the ratio of nitrogen to titanium (N/Ti) of from 0.85 to 0.92 in the as-deposited TiN film.The X-ray diffraction pattern showed the crystal orientation of the TiN film depends on the nitrogen gas pressure. By using a two-exposure method, residual stresses in the TiN films were measured as a function of nitrogen gas pressure and arc current, respectively. The TiN films showed very high compressive residual stresses of about-8.0 to -7.0 GPa.

Non-Maxwell Behavior of Electron Energy Distribution Functions in Expanding Nitrogen Arcs

The electron energy distribution function (eedf) in expanding nitrogen arcs has been obtained by solving a Boltzmann equation including elastic, inelastic, and superelastic terms. Different realistic hypotheses on the concentrations of vibrationally and electronically excited states as well as on the ionization degree have been assumed. The results show that eedf and related coefficients are strongly dependent on the concentrations of excited states that superimpose structures to the bulk of eedf.

NATURE OF ARGON AND NITROGEN ELECTRIC ARC FLUCTUATIONS IN PLASMA TORCH

The electric arc modes of operation in the plasma torch with the cylindrical anode and vortex stabilisation are studied experimentally. Three arc modes are observed but especially two are investigated: the restrike mode and the takeover mode. Particularly the attention is given to the difference of the behaviour of the arc in argon, nitrogen and mixture of argon-nitrogen. The results show that the takeover mode is characteristic for argon arc. The restrike mode occurs for specified argon arc conditions with the thermal breakdown. The restrike arc mode is typical for nitrogen and mixture of argon-nitrogen with electrical breakdown. The time of arc root displacement on anode surface and time of breakdown, the amplitude of fluctuation as functions of arc current and pressure are shown and discussed.

Numerical simulation of a 2 kA convection-stabilized nitrogen arc using CFD tools

A physical model for the computation of convection-stabilized circuit-breaker arcs is presented. The compressible Euler equations have been used as the basic flow model and have been coupled with a two-dimensional arc model to account for the ohmic heating and radiation transport. The governing equations are discretized following a control-volume method for unstructured triangular grids and the fluxes are evaluated using Roe's approximate Riemann solver. This computational fluid-dynamics model is used for the numerical investigation of an axially blown nitrogen arc in a supersonic nozzle and the results are compared with previous numerical results and experimental data.

Generalization of characteristics of cascade electric arcs in various gases

Generalization of differential volt-ampere and other characteristics of cascade electric arcs in air, nitrogen, argon, helium, and hydrogen is carried out for currents of 0.4-300 A and channel radii of 1-20 mm.

Optical emission spectroscopy of the nitrogen arc in an arc-heated beam source used for synthesis of carbon nitride films

An exhaustive study of optical emission from a nitrogen arc produced by an arc-heated beam source is reported. Atomic nitrogen emission lines in the spectral region provide unequivocal evidence that the arc-heated beam source generates an appreciable flux of nitrogen atoms. Experimental results show that the ratio of [N] to increased as the arc pressure decreased. It is believed that this is because of the reduced probability of recombination of [N] atoms. Using this arc-heated beam source for pulsed laser deposition (PLD) film growth, we have synthesized carbon nitride and other nitride films with a high nitrogen content. AES and XPS results indicate that composition ratios ([N]/[C]) in the deposited films were between 0.2 and 0.6. It has been considered that [N] atoms, rather than molecules in the arc, are the most likely species responsible for the synthesis of nitride films.

Arc erosion reduction on electrical contacts using transverse current injection

Electrical contact lifetime is often directly determined by arc erosion. A method for reducing are erosion was developed consisting of injecting from an external current source an additional electrical current flowing parallel to the contact surface. This method was examined in three are environments using the additional transverse electrical current with a density less than 1 A/mm/sup 2/: 1) automobile ignition contacts; 2) pulsed air arc; and 3) low pressure (P=100 mTorr) arc in nitrogen, SEM and X-ray examination showed that application of a transverse current in a contact during arcing changed the phase composition and microstructure of the contact surface. Under optimal conditions, the microstructure which is formed is significantly more erosion resistant than without the transverse current injection.

The influence of demixing on the properties of a free-burning arc

Demixing in an atmospheric-pressure free-burning welding arc was investigated using a two-dimensional numerical model. Simulations of arcs in argon–nitrogen and argon–helium mixtures demonstrated that demixing can have a major influence on the composition of the arc in both the central and edge regions. Convection suppressed the change in composition in the central 0.5 mm of the argon–nitrogen arc only. Furthermore, demixing was found to have only a relatively minor effect on temperature and axial velocity, but it significantly altered thermal transport in the argon–nitrogen mixture. It is concluded that demixing can be important in both chemical and thermal applications of mixed-gas arcs.

Modeling of the Flow, Temperature and Concentration Fields in an Arc Plasma Reactor with Argon-Nitrogen Atmosphere.

A mathematical formulation was developed for describing the flow behavior, temperature profile and concentration fields in pure or mixed argon and nitrogen arc plasmas impinging on a metal target inside a reactor. The simulation involves solution to conservation equations of mass, momentum, energy, k-e model, chemical species, and current continuity. Combined diffusion coefficients were used in chemical species conservation to account for all species present in the plasma. An increase in the proportion of nitrogen introduced in the reactor results in higher arc velocity and temperature, reduced arc column diameter and increased heat flux imparted to the metal target. Demixing resulted to an increase of mass fraction of nitrogen at the central portion of the arc.

Animal protein production modules in biological life support systems: Novel combined aquaculture techniques based on the closed equilibrated biological aquatic system (C.E.B.A.S.)

Based on the experiences made with the Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) which was primarily deveoloped for long-term and multi-generation experiments with aquatic animals and plants in a space station highly effective fresh water recycling modules were elaborated utilizing a combination of ammonia oxidizing bacteria filters and higher plants. These exhibit a high effectivity to eliminate phosphate and anorganic nitrogen compounds and arc. in addidition. able to contribute to the oxygen supply of the aquatic animals. The C.E.B.A.S. filter system is able to keep a closed artificial aquatic ecosystem containing teleost fishes and water snails biologically stable for several month and to eliminate waste products deriving from degraded dead fishes without a decrease of the oxygen concentration down to less than 3.5 mg/l at 25 °C. More advanced C.E.B.A.S. filter systems, the BIOCURE filters, were also developed for utilization in semiintensive and intensive aquaculture systems for fishes. In fact such combined animal-plant aquaculture systems represent highly effective productions sites for human food if proper plant and fish species are selected The present papers elucidates ways to novel aquaculture systems in which herbivorous fishes are raised by feeding them with plant biomass produced in the BIOCURE filters and presents the scheme of a modification which utilizes a plant species suitable also for human nutrition. Special attention is paid to the benefits of closed aquaculture system modules which may be integrated into bioregenerative life support systems of a higher complexity for, e. g.. lunar or planetary bases including some psychologiccal aspects of the introduction of animal protein production into plant-based life support systems. Moreover, the basic reproductive biological problems of aquatic animal breeding under reduced gravity are explained leading to a disposition of essential research programs in this context.

A Wall Stabilized Nitrogen Arc Model at Different Concentration of Silver Vapour and Current Intensity

This paper presents theoretical results for a nitrogen arc contaminated with silver vapours emitted from arc electrode in a range from 0 to 10% and current intensity between 5 to 50 A. By solving the equation of conservation of energy, the effect of these vapours on the arc plasma characteristics are studied. In particular it was seen that the presence of 10-4% Ag in the arc column decreases strongly the axial temperature while the presence of 10-1% Ag has an explicit decreases in the electric field at current near 20 A.

Powerful pulse generator of dense plasma with high concentration of metal vapour

The results of experiments on the heating of hydrogen and nitrogen of high initial pressure (20 – 40 MPA) by high-current discharge with discharge current amplitude up to 1,5 MA, initiated by wire explosion, are represented in the paper. Owing to high erosion of anode and cathode due to the discharge, equal to 200 – 300 C, passing through them, the average magnitude of metal vapours concentration in the discharge chamber is 10cm20 cm−3, that can be compared to working gas concentration. On the basis of the experimental results and metal plasma conductance calculations data the estimations of the temperature of the discharge channel are given.Using data of the experiments with arcs in hydrogen, nitrogen and helium with current discharge amplitude equal to 20 – 200 kA the conclusion about the defining influence of metal vapours on the properties of the arc itself and on the heat exchange between the arc and the environmental gas is drawn. For example, the increase of arc's turbulence level with the decrease of distance between electrodes is connected with metal streams introduction from electrodes to the near-electrodes areas. The increase of gas heating efficiency with the increase of initiating wire mass is stipulated by metal vapours radiation absorption in the cold zone.

Reduction of NOx Contained in Combustion Exhaust Gas by Using Corona Discharge Tube.

In order to develop methods of plasma injection for removing pollutants such as NOx and SOx contained in combustion exhaust gas, we have investigated radical formation in nitrogen arc plasma, and reported that the NOx removal efficiency has a maximum value in the range of low electrical power for plasma operated under stable conditions. In this paper, in order to further economize electrical energy in actual use, the simulated exhaust gas (N2+O2+CO2+NO) is excited by passing through a corona discharge tube in a high electric voltage field. The NO is oxidized to NO2, and OH radical generated from H2O contained in gas reacts with NO2, and NO concentration decreases as a result of generation of HNO3. The effects of H2O, O2 and CO2 contents on the NOx reduction rate are discussed experimentally. The NOx reduction rate of about 25% is obtained under the input power of 45 watts.

Study of the Nitrogen Arc under Reduced Pressure

AbstractThe paper presents a model of arc in a d.c. vortex plasma torch which allows to determine distributions of temperature and plasma electron density in conditions of reduced pressure. The model makes it possible to elucidate voltage‐current characteristics of the arc at different pressures and its dynamic behaviour connected with the phenomenon of the electric arc root displacement. The experimental research also determined voltage‐current characteristics for different flow rates and pressures. The fluctuations of the arc current and the arc voltage were measured. The corresponding wave shapes were analysed by Fast Fourier Transform. The frequency variations with flow rate, arc current and pressure were studied and discussed.

Laser-scattering temperature measurements of a free-burning arc in nitrogen

Measurements of the temperature of a 200 A free-burning arc in nitrogen, performed using a laser-scattering technique that does not require frequency resolution of the scattered signal, are presented. The technique is applicable to the full temperature range observed in free-burning arcs. However, signal-to-noise problems limited the present measurements to temperatures below about 16000 K. The laser-scattering results show excellent agreement with temperatures measured by emission spectroscopy. The spectroscopic measurements are shown not to be affected by deviations from local thermodynamic equilibrium at temperatures as low as 8000 K, below which the emission was too weak to allow temperatures to be determined. This is contrasted with the case of free-burning arcs in argon, for which departures from local thermodynamic equilibrium, thought to be caused mainly by resonance radiation trapping, render spectroscopic measurements unreliable below about 11000 K. An explanation for the differences between arcs in the two gases, in terms of different rates of excitation of high-energy states by resonance radiation trapping, is suggested.

Phénomènes thermiques et électriques dans le plasmatron en courant alternatif

There was presented a model of the A.C. electric arc stabilized with gas. This model takes into account the real conditions existing in plasmatrons, in particular the method of the reignition of arc after current zero. The model allows to calculate a distribution of the temperature in the arc and the parameters occurring in the equation of the arc conductance. The results are discussed for the argon and nitrogen arc

Experimental study of a supersonic low-pressure nitrogen plasma jet

A supersonic nitrogen arc plasma jet expanded in a low-pressure test chamber is studied. Radial measurements of temperatures and densities are performed in the expanding region over various sections from the nozzle exit. Nitrogen is highly dissociated in the arc chamber and the plasma is far from equilibrium. Electron temperature and density, as well as gas velocity, are measured by means of parallel and crossed electrostatic probes. Measurements of selected atomic and molecular line intensities are performed in the 250–850 nm spectral range to obtain number densities of various N2, N2+ and N excited levels. The rotationally resolved emission spectrum from the (0–0) band of the N2+ first negative system (B2Σ+u→X2Σ+g) is analyzed and compared to synthetic spectra to evaluate the rotational temperature within the flow field. The kinetic scheme of ionic recombination of N+ and N2+ is examined. A recombination path of the N2(C3Πu) electronic state via the N2(C″5Πu) state is proposed for the N(2D0)+N(4S0) nitrogen recombination.