Increasing Input Power Research Articles

Electron number density measurement on a DC argon plasma jet by stark broadening of Ar I spectral line

In thermal plasma processing, input power and gas flow rate play a major role in controlling the plasma jet temperature, velocity and density. Emission spectroscopy study is an important method for plasma diagnostics. A DC atmospheric plasma spray torch was operated at different power levels and flow rates of plasma gas (argon). Electron number density of the plasma jet, the corresponding temperature and the degree of ionization were determined using stark broadening of the Ar I (430.010 nm) line, the atomic Boltzmann plot method and the Saha equation, respectively. In the present work, we have investigated the effect of input power, axial position of the plasma jet and gas flow rate on the electron number density in the plasma jet. While an increase in input power considerably increased the electron number density, gas flow rate did not show any significant effect on the same.

Agitation effects on morphology and protein productive fractions of filamentous and pelleted growth forms of recombinant Aspergillus niger

Recombinant Aspergillus niger genetically engineered to produce glucose oxidase using the constitutive gpdA promoter and the glucoamylase signal sequence for secretion was grown in batch cultures at agitation speeds of 200–800 rpm covering the industrial relevant power input range of 0.1–5 W kg −1. The growth morphology ranged from large pellets with an average diameter of 1500 μm at low power input up to micropellets embedded in a filamentous network at high power input. A correlation of agitation intensity with growth morphology and glucose oxidase production revealed an increase of the protein production capability with the change of the growth morphology from pelleted to filamentous growth forms. However, the exposure to higher shear stress with increasing power input also resulted in lower biomass yields as well as increased transient formation of polyol (xylitol) and higher final concentrations of oxalic acid. The highest specific production rates were found in young filamentous growth forms at high power input. Although intermediate agitation intensity leading to small pellets became more favorable during prolonged cultivation. An acridine orange staining procedure discriminating between RNA rich (red) and RNA poor regions (green) of the fungal biomass proved that active protein production is restricted to filamentous growth forms and the outer layer of fungal pellets. A correlation between the RNA rich fraction of the biomass determined by image analysis and the productivity is shown.

Experimental study on an all-optical switching based on MF-NOLM

In this paper, the experiment on an all-optical switching is reported based on a microstructure fiber(MF)-nonlinear optical loop mirror (NOLM). In the experiment, a 25-meter-long MF (γ=36W−1km−1@1550 nm) is used as a nonlinear medium of the nonlinear optical loop mirror and the input signal is generated by a 10 GHz tunable picosecond laser source, with a full-width at half-maximum (FWHM) of 2 ps and centered at 1550 nm. With the increase of input power, a π nonlinear phase shift is obtained by a 40/60 coupler in the experiment, but the same result can not be found by a 48/52 coupler. Additionally, the switching devices can also be used as an all-optical regeneration.

Chemical structure and surface morphology of plasma polymerized-allylamine film

In this study, we conducted the plasma polymerization of allylamine using radio frequency (RF) glow discharge with continuous wave (CW) in order to make an organic thin film with an amine functional group retained. Allylamine as a monomer was deposited on a glass in a bell-jar type plasma reactor and polymerized to plasma-polymerized allylamine (PPAa). The parameter to control the property of plasma polymer was input power at other conditions remaining constant. The chemical structure and the surface morphology of plasma-polymerized allylamine (PPAa) film were characterized by contact angle measurement, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM). The property of PPAa film was highly dependent upon the plasma input power. The input power, which determines the plasma density, results in a property of PPAa thin film such as hydrophilicity, high retention of functionality of PPAa’s surface. Surface energy calculated by contact angle measurement indicated that increasing input power (from 30W to 90W) decreased the hydrophilic property of PPAa due to loss of amine functional group and high cross-linking. The increase of the energy causes the films to be harder. ATR-FTIR and XPS results showed that high input energy fragmented the amine group from monomer with increasing nitrogen atomic content and nitrile group. The high retention of amine groups seems mainly favored by low input power (<30 W). From thickness measurement usingα-stepper, the deposition rates were 0.43, 0.83, 1.11, 1.37 nm/s at 30, 50, 70, 90W, respectively. The change of surface morphology of plasma-polymerized thin films was investigated after soaking the PPAa film into ethanol. Due to weak adhesion with substrate and internal stress in plasma polymer film, the surface morphology of PPAa film revealed some irregular network pattern.

Meniscus Behavior in Electromagnetic Soft-Contact Continuous Casting Round Billet Mold

Using molten Pb-Sn-Bi alloy, the meniscus shape under high frequency magnetic field of o100 mm round billet caster was investigated. The effect of some parameters on meniscus shape was studied. The results show that for a mold with 12 segments, the meniscus shape is relatively stable. With increasing power input, the meniscus height increases with intensification of fluctuation. For the given caster, the reasonable power input is about 70 kW. The coil should be near to the top of mold and/or the initial meniscus should be near to the center of the coil. The lower the frequency, the higher is the meniscus height. With increasing frequency, the free surface is more flattened and meniscus becomes more stable. In practice, the power input should be increased simultaneously with frequency. The optimal frequency is about 20 kHz.

Demonstration of steady inductive helicity injection

Initial results demonstrating the concept of constant inductive helicity injection are presented. Constant helicity injection is achieved using two oscillating inductive helicity injectors, with the goal of producing a bow tie spheromak. Each injector is a 180° segment of a reverse field pinch and they are driven 90° out of phase. Approximately 5 MW of power is injected during the 6 ms pulse, and the input power has been maintained at a fairly constant value by directly fuelling the injectors with neutral gas. Motivation for the experiment is given, including beta-limit calculations for the bow tie spheromak. Fuelling the injectors with neutral gas during the discharge is shown to produce injector parameters that are more constant in time. A series of discharges with increasing power input shows a promising increase in toroidal current. Unique construction techniques of the experiment are also described.

MPDスラスタ内における電熱・電磁加速モード間の遷移に関する研究

It is widely known that a self-field MPD thruster changes from an electrothermal acceleration mode to an electromagnetic one as the discharge current is increased. Such transitional behavior is numerically studied with argon propellant using a two-dimensional TVD Lax-Friedrich scheme incorporating multiple ionization processes. As the discharge current J is increased from 4 to 10kA under a mass flow rate of 0.8g/s, a steep rise of the voltage, which indicates the transition, occurs between low and high current modes of operation around J=7kA, which is equivalent to the Alfven’s critical ionization current. The steep voltage rise is attributed to the increase in the work of the Lorentz force around the cathode. The radial distributions of the heavy particles and electrons are examined and compared with the past experimental results. Additionally, in the electromagnetic mode, the ratio of the ionization energy to the input power decreases with increasing input power, and the maximum ratio of the kinetic energy to the input power is 0.57. This high thrust efficiency can be attributed to the idealized model, in which the effects of the sheath as well as the heat loss to the electrodes are neglected.

Effect of antenna configuration on power transfer efficiency for planar inductively coupled plasmas

Based on a transformer model for inductively cowpled plasmas (ICPs), the dependence of power coupling efficiency on Q value, plasma electron density and effective electron-atom collision frequency is analyzed. The effect of coil configuration on power coupling efficiency is studied using four types of coils (one-turn, two-turn, three-turn and four-turn planar concentric coils) experimentally. The results indicate that the inductive discharge depends on coil inductance while the coupling efficiency varies with the Q value and discharge conditions such as pressure and input power. The coupling efficiency increases with the increase of pressure and input power, which is in accordance with the transformer model. However, the prediction given in the model that an increase in coil Q value improves power coupling efficiency is only applicable for coils with the same inductance. The study on power coupling efficiency for single multi-turn coil has been applied as an experimental reference for a large-area, high density inductive discharge source using four parallel multi-turn coils.

Direct observations of the α → γ transformation at different input powers in the heat-affected zone of 1045 C-Mn steel arc welds observed by spatially resolved X-ray diffraction

Spatially resolved X-ray diffraction (SRXRD) experiments have been performed during gas tungstenarc (GTA) welding of AISI 1045 C-Mn steel at input powers ranging from 1000 to 3750 W. In-situ diffraction patterns taken at discreet locations across the width of the heat-affected zone (HAZ) near the peak of the heating cycle in each weld show regions containing austenite (γ), ferrite and austenite (α+γ), and ferrite (α). Changes in input power have a demonstrated effect on the resulting sizes of these regions. The largest effect is on the γ phase region, which nearly triples in width with increasing input power, while the width of the surrounding two-phase α+γ region remains relatively constant. An analysis of the diffraction patterns obtained across this range of locations allows the formation of austenite from the base-metal microstructure to be monitored. After the completion of the α → γ transformation, a splitting of the austenite peaks is observed at temperatures between approximately 860 °C and 1290 °C. This splitting in the austenite peaks results from the dissolution of cementite laths originally present in the base-metal pearlite, which remain after the completion of the α → γ transformation, and represents the formation of a second more highly alloyed austenite constituent. With increasing temperatures, carbon, originally present in the cementite laths, diffuses from the second newly formed austenite constituent to the original austenite constituent. Eventually, a homogeneous austenitic microstructure is produced at temperatures of approximately 1300 °C and above, depending on the weld input power.

NOLM-NALM fiber ring laser

We study the bidirectional lightwave propagations in an erbium-doped fiber ring laser and an inverted-S fiber ring laser, and observe their optical bistability behaviors. We develop a model for the inverted-S fiber ring laser using nonlinear optical loop mirror and nonlinear amplifying loop mirror (NOLM-NALM) principle, which operates in the nonlinear region. Good agreements between the laser experimental performance and the developed model are achieved. The laser shows good switching and pulse compression capabilities. In addition, the laser model illustrates the route to chaotic operation via period doubling bifurcation, when the input power increases. We also obtain quasi-periodic operation when the laser is amplitude modulated experimentally.

Langmuir probe measurements in inductively coupled CF 4 plasmas

The characteristics of low-pressure inductively coupled CF 4 plasmas have been investigated using a Langmuir probe. The electrons gain energy through the collisionless heating mechanism. In addition, the plasma has two electron populations: low temperature population of electrons with high density, and high temperature population of electrons with low density. With the increase of radio-frequency input power, the former temperature T ce, the latter temperature T he, and mean electron temperature T e decrease, while their densities n ce, n he, n e increase. This phenomenon has been explained by the thermodynamic equilibrium of the collision between the electrons and radicals in the plasma.

Tungsten Coating on Low Activation Vanadium Alloy by Plasma Spray Process

Tungsten (W) coating on fusion candidate V-4Cr-4Ti (NIFS-HEAT-2) substrate was demonstrated with plasma spray process for the purpose of applying to protection of the plasma facing surface of a fusion blanket. Increase in plasma input power and temperature of the substrate was effective to reduce porosity of the coating, but resulted in hardening of the substrate and degradation of impact property at 77 K. The hardening seemed to be due to contamination with gaseous impurities and deformation by thermal stress during the coating process. Since all the samples showed good ductility at room temperature, further heating seems to be acceptable for the vanadium substrate. The fracture stress of the W coating was estimated from bending tests as at least 313 MPa, which well exceeds the design stress for the vanadium structure in fusion blanket.

Advances in understanding quiescent H-mode plasmas in DIII-D

Recent QH-mode research on DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] has used the peeling-ballooning modes model of edge magnetohydrodynamic stability as a working hypothesis to organize the data; several predictions of this theory are consistent with the experimental results. Current ramping results indicate that QH modes operate near the edge current limit set by peeling modes. This operating point explains why QH mode is easier to get at lower plasma currents. Power scans have shown a saturation of edge pressure with increasing power input. This allows QH-mode plasmas to remain stable to edge localized modes (ELMs) to the highest powers used in DIII-D. At present, the mechanism for this saturation is unknown; if the edge harmonic oscillation (EHO) is playing a role here, the physics is not a simple amplitude dependence. The increase in edge stability with plasma triangularity predicted by the peeling-ballooning theory is consistent with the substantial improvement in pedestal pressure achieved by changing the plasma shape from a single null divertor to a high triangularity double null. Detailed ELITE calculations for the high triangularity plasmas have demonstrated that the plasma operating point is marginally stable to peeling-ballooning modes. Comparison of ELMing, coinjected and quiescent, counterinjected discharges with the same shape, current, toroidal field, electron density, and electron temperature indicates that the edge radial electric field or the edge toroidal rotation are also playing a role in edge stability. The EHO produces electron, main ion, and impurity particle transport at the plasma edge which is more rapid than that produced by ELMs under similar conditions. The EHO also decreases the edge rotation while producing little change in the edge electron and ion temperatures. Other edge electromagnetic modes also produce particle transport; this includes the incoherent, broadband activity seen at high triangularity. Pedestal values of ν* and βT bracketing, those required for International Experimental Thermonuclear Reactor [Nucl. Fusion 39, 2137 (1999)] have been achieved in DIII-D, demonstrating the QH-mode edge densities are sufficient for future devices.

Far-field spectral characterization of conical emission and filamentation in Kerr media

By use of an imaging spectrometer we map the far-field ($\theta-\lambda$) spectra of 200 fs optical pulses that have undergone beam collapse and filamentation in a Kerr medium. By studying the evolution of the spectra with increasing input power and using a model based on stationary linear asymptotic wave modes, we are able to trace a consistent model of optical beam collapse high-lighting the interplay between conical emission, multiple pulse splitting and other effects such as spatial chirp.

Influence of plasma reactor structure on methanol oxidation

AbstractPlasma oxidation of methanol (CH3OH) in oxygen and nitrogen was investigated using two dielectric barrier discharge (DBD) reactors with or without Al2O3 as a catalyst and using a DC circle‐to‐plate (CTP) reactor. An AC power supply was used for the DBD reactors to generate corona discharges. A DC power supply, a 20‐MΩ resistor, and a 100‐pF capacitor were used to yield pulselike discharges. CH3OH was oxidized to formaldehyde (HCHO), carbon monoxide (CO), and carbon dioxide (CO2). HCHO was the main product when using DBD reactors and without Al2O3. CO was the main product when using the DBD reactor with Al2O3 and CTP reactor. Al2O3 could inhibit CH3OH further oxidation. The energy efficiency of the DBD reactors decreased with increasing power input and power density. The energy efficiency of the CTP reactor peaked with 7 g CH3OH/kWh that was three times as high as that with the DBD reactors at the same power input. Furthermore, the power density of the CTP reactor was higher than that of the DBD reactors, implying that the CTP reactor could be used for CH3OH oxidation with a small discharge space volume. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Generation of ozone by pulsed corona discharge over water surface in hybrid gas–liquid electrical discharge reactor

Ozone formation by a pulse positive corona discharge generated in the gas phase between a planar high voltage electrode made from reticulated vitreous carbon and a water surface with an immersed ground stainless steel plate electrode was investigated under various operating conditions. The effects of gas flow rate (0.5–3 litre min−1), discharge gap spacing (2.5–10 mm), applied input power (2–45 W) and gas composition (oxygen containing argon or nitrogen) on ozone production were determined. Ozone concentration increased with increasing power input and with increasing discharge gap. The production of ozone was significantly affected by the presence of water vapour formed through vaporization of water at the gas–liquid interface by the action of the gas phase discharge. The highest energy efficiency for ozone production was obtained using high voltage pulses of approximately 150 ns duration in Ar/O2 mixtures with the maximum efficiency (energy yield) of 23 g kW h−1 for 40% argon content.

Color Variable Light Source Using Electrodeless Discharge

Color variable pulsed Hg-Ne discharge lamp was invented and reported by Itatani's group in 1973. The color of Hg-Ne discharge was controlled by changing electron temperature by changing pulse frequency. Maya's group reported about color variable mercury fluorescent lamps using burst pulse and different type of phosphors. Kroesen's group proposed Hg-Ne color variable lamp using depletion effect. All these lamps use electrodes inside a tube. The authors propose a new type of color variable discharge lamp using inductively coupled plasma (ICP), electrodeless discharge. Color variable lamp using ICP is demonstrated. Just after starting discharge of Hg-Ne, the luminescent color of the lamp is red because of Ne emission. After that, the color changes gradually toward blue resulting from increase in mercury vapor pressure. When the color change stoppes and it is in the steady state with blue color, the color can be changed toward red by increasing input power. This is due to Ne emission resulting from increase in current density.

Microwave Heating Behavior of Blast Furnace Slag Bearing High Titanium

Blast furnace (BF) slag in south-western part of China contains large amount of titanium. For the purpose of beneficial utilization of titanium in the slag, microwave (MW) processing of the slag has been proposed. In this study, a fundamental research on heating behavior of the slag by application of 2.45 GHz MW was performed.The slag specimens can be heated in a domestic MW oven at constant input power (0.5 kW) and sudden increase of the temperature is observed after several heating cycles. A phenomenon of so-called thermal runaway (TRW) occurred. A part of the specimen melted, and the XRD analysis indicated that this area became amorphous. Crystallization of the CaTiO3 phase occurred by MW heating of the melted slag at 600°C.A sintered CaTiO3 compact was heated by MW much more than the synthetic Chinese slag. The synthetic slag without containing Ti was not heated very well. Permittivity of CaTiO3 (loss factor) was measured and demonstrated to be much larger than the other oxides in the slag. Therefore, it is concluded that CaTiO3 phase is responsible for heating of the whole slag.

20415 高温窒素プラズマによるディーゼル排ガスの浄化(OS3 エンジン燃焼と排気浄化)

A technique for removing the NOx contained in combustion exhaust gas has been developed by using radicals produced in the mixing arc plasma. By feeding the diesel exhaust from engine into (N_2+diesel oil) arc plasma torch, diesel oil and N_2 radicals such as NH, HC, N, H are produced, and these radicals are mixed in a reactor with the exhaust gas. The NOx decreases as a result of the formation of the innocuous products N_2, H_2O and CO_2 if O_2 is contained in the gas. Under present experimental conditions, diesel oil reacts as reduction agency such as the thermal De-NOx process, the oxidation of diesel oil are not expected. In the case of t O_2 rich gas, NOx increases with increasing input power to plasma. The effects of input power, Diesel oil/NOx, treated gas flow rate and the distance from nozzle exit to exhaust pipe L/d on the NOx removal rate are investigated experimentally.

Decomposition of benzene in the RF plasma environment: Part I. Formation of gaseous products and carbon depositions

This study employed radio-frequency (RF) plasma for decomposing benzene (C 6H 6) gas, and examined both gaseous products and solid depositions after reaction. The reactants and products were analyzed mainly by using both an on-line Fourier transform infrared (FT-IR) spectrometer and a gas chromatography. The analyses for solid deposition included electron spectroscopy for chemical analysis (ESCA), element analysis and heat value analysis. The C 2H 2, C 2H 4, C 2H 6, CH 4, CO 2 and CO were detected and discussed. The analytical results demonstrate that in the C 6H 6/Ar plasma, C 2H 2 is the sole gaseous product being detected. The fraction of total carbon input converted into C 2H 2 ( Y C 2 H 2 ) increased with increasing C 6H 6 feed concentration, but decreased with increasing input power. In the C 6H 6/H 2/Ar system, besides C 2H 2, CH 4, C 2H 4 and C 2H 6 were also detected, and their yields increased with increasing H 2/C 6H 6 ratio. The above results indicated that the addition of H 2 (auxiliary gas) achieves the benefit of creating hydrogen-rich species like CH 4, C 2H 4 and C 2H 6. In the C 6H 6/O 2/Ar system, C 6H 6 could be totally oxidized into CO 2, CO and H 2O, and no measurable phenol was found. Analyses of solid depositions revealed that the carbon depositions were similar to those of Anthracite. The carbon deposition has a heat value of 7000 kcal/kg. Additionally, the possible reaction pathways were also built up and discussed.