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A. N. Makarov - One of the best experts on this subject based on the ideXlab platform.
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Effect of the Slag Layer Thickness, Gas Composition, and Furnace Capacity on the Arc Efficiency and Heat Transfer in Arc Furnaces. Part I. Effect of the Slag Thickness and Furnace Capacity on Arc Efficiency
Metallurgist, 2021Co-Authors: A. N. Makarov, V. V. Okuneva, A. V. KuznetsovAbstract:The angular thermal radiation coefficients and the Efficiency of Arcs for different distances from them to the walls of electric-Arc furnaces of 0.5 to 120 t capacity are calculated. A relationship between the Arc Efficiency and the specific power consumption of the furnaces is established. The Arc Efficiency versus the depth of submersion of the Arcs into the metal bath and slag in high- and low-capacity electric-Arc furnaces is calculated and plotted.
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Calculation and Analysis of the Relationship Between the Efficiency and Position of Electric Arcs and Power Consumption in Electric Arc Furnaces (EAF) of Smaller and Larger Capacity. Part 2. Calculation and Analysis of the Relationship Between Positi
Metallurgist, 2019Co-Authors: A. N. MakarovAbstract:The power consumed during the melting process by a small-capacity DSP-5 furnace was analyzed. For each melting stage, the Arc Efficiency values of DSP-5 furnaces and average Arc Efficiency of the melting process (η_AM = 0.57) were calculated. The Arc Efficiency of the small-capacity furnaces is considerably lower than that of the modern large-capacity DSP-120 furnaces (η_AAV = 0.78). One cause of the lower Arc Efficiency of the small-capacity furnaces during furnace charge melting and Arc burning inside the wells is the small distance between the Arcs and the lining of the furnace walls. Another cause of the lower Arc Efficiency of the small-capacity furnaces during the liquid-phase periods of the melting process is the large exposed portion of the Arc, no deep Arc immersion into slag, and no slag foaming in the furnace. The low Arc Efficiency of the small-capacity furnaces leads to a significant specific power consumption during melting (700–750 kW·h/t), which is 1.9 to 2 times greater than that of the modern DSP-120 furnaces (375 kW·h/t). By using slag foaming devices in the small-capacity furnaces, it becomes possible to increase the average furnace Arc Efficiency of the melting process to η_AM = 0.72–0.74, while reducing the specific power consumption during melting to 400–420 kW·h/t.
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Effect of the Architecture on Energy Efficiency of Electric Arc Furnaces of Conventional and Consteel Designs
Metallurgist, 2019Co-Authors: A. N. MakarovAbstract:Heat transfer and Arc Efficiency of the electric Arc furnaces (EAF) of Consteel (DSP-120co) and conventional (DSP-120ob) designs, equipped with the modern melting process intensification means, have been analyzed. For comparison purposes, EAFs of similar capacity and performance were used. As a result of analysis, it was found that the average Arc Efficiency of the Consteel DSP-120co furnace is 8 to 9% lower than that of the DSP-120ob furnace. The analysis of the EAF Arc Efficiency made it possible to explain the higher specific energy consumption by the DSP-120co compared to that of the DSP-120ob furnace.
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Electromagnetism and the Arc Efficiency of Electric Arc Steel Melting Furnaces
Journal of Electromagnetic Analysis and Applications, 2014Co-Authors: A. N. Makarov, V. V. Rybakova, M. K. GalichevaAbstract:Results of analytically studied effect of electromagnetic blowing and the slag height on the Arc Efficiency are stated. An Arc is blown from under an electrode toward the furnace walls under an electromagnetic force, Arc radiation on the wall and roof increase and effective output, absorbed by the metal decreases. EAF (electric Arc steel melting furnace) with independently powered Arcs, eliminating its electromagnetic blowing is proposed. When Arcs are powered independently, its Efficiency increases significantly, and specific energy consumption decreases.
Changseog Seo - One of the best experts on this subject based on the ideXlab platform.
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Arc discharge Efficiency of a multi megawatt long pulse ion source for the kstar neutral beam injector
Plasma Sources Science and Technology, 2005Co-Authors: Doohee Chang, Seungho Jeong, Kwang Won Lee, Changseog SeoAbstract:A multi-megawatt long pulse ion source (LPIS) was developed for the Korea Superconducting Tokamak Advanced ReseArch (KSTAR) neutral beam (NB) injector. Arc discharge characteristics of the ion source were investigated on the NB test stand. The ion source consists of a magnetic bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerators with circular apertures. The inner volume of the ion source, including the accelerator column, is approximately 150 litres. Design requirements for the ion source were a 120 kV/65 A deuterium beam and a 300 s pulse length and initially an 80 kV/48 A hydrogen beam for a 20 s pulse length. Arc discharges of the plasma generator with hydrogen gases have been controlled by the emission-limited mode, operated by the applied heating voltage of the cathode filaments. Stable and efficient Arc plasmas, with a maximum Arc power of 110 kW, have been produced by a constant voltage (CV) mode operation of an Arc power supply. The CV mode operation of the Arc powers was more efficient than the constant power (CP) mode operation in the LPIS. A maximum ion density of 9.1 × 1011 cm−3 was measured by using electrostatic probes. The plasma non-uniformity of the ion source was less than 8% and was under the design limit. An optimum Arc Efficiency, defined by the ratio of extractible ion beam current to Arc input power, of 0.46 A kW−1 was estimated for the CV mode operation and 0.44 A kW−1 for the CP mode operation. This Arc Efficiency is enough to extract the expected hydrogen beam of 48 A.
Kjell Hurtig - One of the best experts on this subject based on the ideXlab platform.
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a critical analysis of weld heat input measurement through a water cooled stationary anode calorimeter
Science and Technology of Welding and Joining, 2016Co-Authors: Kjell Hurtig, Isabelle Choquet, Americo Scotti, Larserik SvenssonAbstract:Comprehensive models of heat transfer require specification of the total amount of heat received by the workpiece. The objective of this work was to critically examine the use of a water-cooled stationary anode calorimeter to obtain both Arc Efficiency and total heat input into the workpiece. For simplicity and clarity, this last quantity is called the gross heat input. The effects of current, material type and water flow rate on the calorimeter performance were determined experimentally. Some measures for reducing errors in calorimetry were evaluated. Improvements were made to reduce heat losses from the top surface of the test coupon and boost heat removal from the opposite surface. A sensitivity test was conducted to estimate the effect of measurement inaccuracies. The results demonstrate the effectiveness of calorimetry for measuring gross heat input in Arc welding.
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a critical analysis of weld heat input measurement through a water cooled stationary anode calorimeter
JOM 18 International conference on joining materials Helsingör Danmark april 26-29 2015, 2015Co-Authors: Kjell Hurtig, Isabelle Choquet, Americo Scotti, Larserik SvenssonAbstract:A comprehensive model on heat transfer in welded plates is able to calculate the amount of heat losses from the surfaces. A model demands as input parameter the amount of heat delivered to the plate, independently of any loss (called here gross heat input for clarity). However, the great discrepancies among the results of calorimetric measurements have left many reseArchers skeptical about using this parameter in modeling as absolute term. The objective of this work was to assess the use of a water-cooled stationary anode calorimeter to obtain not only Arc Efficiency, but also gross heat input. A series of tests was carried out to determine the effect of current, material type and water flow rate on the calorimeter performance, as well as to evaluate some measures for reducing the calorimeter intrinsic errors. Finally, a sensitivity test was conducted to estimate the effect of measurement inaccuracies on the absorbed heat and Arc Efficiency values. The results showed that this calorimetric approach is a simple way for measuring gross heat inputs in Arc welding. Nevertheless some improvement to reduce heat losses from the top surface and boost heat sinking from the opposite surface of the test coupon must be applied. This calorimeter is, on the other hand, highly sensitive to the parameter measurements, leading to errors up to ± 0.09 in Arc Efficiency determination if the instrument is not properly calibrated and installed.
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Review of Arc Efficiency Values for Gas Tungsten Arc Welding
2012Co-Authors: Nils Stenbacka, Isabelle Choquet, Kjell HurtigAbstract:The aim of this study was to review the literature that specifies Arc Efficiency values for gas tungsten Arc welding (GTAW) and, if possible, propose a plausible value range. The literature review covered the years between 1955 and 2011, and showed that the Arc Efficiency values published lie in a wide range. Values between 0.36 and 0.90 were found for GTAW DCEN. Only a few studies covered DCEP and AC current welding. Specific information about the reproducibility of calorimetric studies was scArce (considering both random and systematic errors). A plausible Arc Efficiency range (95% confidence) for GTAW DCEN was estimated to be 0.73 – 0.82 with an average value of 0.78. The Arc Efficiency is lowered by longer Arcs (increased Arc gap). Reports describing the influence of Arc current and travel speed, however, conflict. The GTAW process with DCEN is an efficient welding method.
Doohee Chang - One of the best experts on this subject based on the ideXlab platform.
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first neutral beam injection experiments on kstar tokamak
Review of Scientific Instruments, 2012Co-Authors: Seungho Jeong, Doohee Chang, Kwang Won Lee, Taeseong Kim, Jungtae Jin, Daesik Chang, Y S Bae, J S Kim, H T Park, K WatanabeAbstract:The first neutral beam (NB) injection system of the Korea Superconducting Tokamak Advanced ReseArch (KSTAR) tokamak was partially completed in 2010 with only 1∕3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly, which is designed to deliver a 1.5 MW, NB power of deuterium at 95 keV. Before the beam injection experiments, discharge, and beam extraction characteristics of the ion source were investigated. The ion source has good beam optics in a broad range of beam perveance. The optimum perveance is 1.1-1.3 μP, and the minimum beam divergence angle measured by the Doppler shift spectroscopy is 0.8°. The ion species ratio is D(+):D(2)(+):D(3)(+) = 75:20:5 at beam current density of 85 mA/cm(2). The Arc Efficiency is more than 1.0 A∕kW. In the 2010 KSTAR campaign, a deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with a beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. The edge pedestal formation in the T(i) and T(e) profiles was verified through CES and electron cyclotron emission diagnostics. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and plasma stored energy were found.
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Arc discharge Efficiency of a multi megawatt long pulse ion source for the kstar neutral beam injector
Plasma Sources Science and Technology, 2005Co-Authors: Doohee Chang, Seungho Jeong, Kwang Won Lee, Changseog SeoAbstract:A multi-megawatt long pulse ion source (LPIS) was developed for the Korea Superconducting Tokamak Advanced ReseArch (KSTAR) neutral beam (NB) injector. Arc discharge characteristics of the ion source were investigated on the NB test stand. The ion source consists of a magnetic bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerators with circular apertures. The inner volume of the ion source, including the accelerator column, is approximately 150 litres. Design requirements for the ion source were a 120 kV/65 A deuterium beam and a 300 s pulse length and initially an 80 kV/48 A hydrogen beam for a 20 s pulse length. Arc discharges of the plasma generator with hydrogen gases have been controlled by the emission-limited mode, operated by the applied heating voltage of the cathode filaments. Stable and efficient Arc plasmas, with a maximum Arc power of 110 kW, have been produced by a constant voltage (CV) mode operation of an Arc power supply. The CV mode operation of the Arc powers was more efficient than the constant power (CP) mode operation in the LPIS. A maximum ion density of 9.1 × 1011 cm−3 was measured by using electrostatic probes. The plasma non-uniformity of the ion source was less than 8% and was under the design limit. An optimum Arc Efficiency, defined by the ratio of extractible ion beam current to Arc input power, of 0.46 A kW−1 was estimated for the CV mode operation and 0.44 A kW−1 for the CP mode operation. This Arc Efficiency is enough to extract the expected hydrogen beam of 48 A.
Tarasankar Debroy - One of the best experts on this subject based on the ideXlab platform.
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guaranteed fillet weld geometry from heat transfer model and multivariable optimization
International Journal of Heat and Mass Transfer, 2004Co-Authors: A. Kumar, Tarasankar DebroyAbstract:Abstract Numerical heat transfer models of gas metal Arc (GMA) fillet welding do not always predict correct temperature fields and fusion zone geometry. The inaccuracy results, to a large extent, due to the difficulty in correctly specifying several input parameters such as Arc Efficiency from scientific principles. In order to address this problem, a heat transfer model is combined with an optimization algorithm to determine several uncertain welding parameters from a limited volume of experimental data. The resulting smart model guarantees optimized prediction of weld pool penetration, throat and leg-length within the framework of phenomenological laws. A boundary fitted coordinate system was used to account for the complex fusion zone shape. The weld pool surface profile was calculated by minimizing the total surface energy. Apart from the direct transport of heat from the welding Arc, heat transfer from the metal droplets was modeled considering a volumetric heat source. The Levenberg–Marquardt and two versions of conjugate gradient method were used to calculate the optimized values of unknown parameters. An appropriate objective function that represented the difference between the calculated and experimental values of the penetration, throat and leg-length was minimized. The calculated shape and size of the fusion zone, finger penetration characteristic of the GMA welds and the solidified free surface profile were in fair agreement with the experimental results for various welding conditions.