Modelling the Role of the Inner Electrode Radius on the Oxygen Negative Corona Discharge in Coaxial Electrode Geometry

The charge species plays a vital role in changing the field in direct current discharge (DC). This article introduces a numerical modeling in one dimension of the inner electrode diameter of oxygen-fed negative corona discharge in coaxial electrodes geometry. The properties of negative corona plasma in a concentric cylindrical electrodes (wire-cylinder) were simulated by COMSOL Multiphysics software. Various diameters of negative corona electrode, namely 0.01, 0.025, 0.05, 0.075, and 0.125 mm, were applied, ​​where the diameter of the outer cylindrical electrode was taken as 15 mm. The model was run at atmospheric pressure and the applied negative voltage was -10 KV. Moreover, oxygen gas was used to fill the inter-electrodes distance. Furthermore, the spatial distribution of electrons, positive ions, and negative ions as a function of the diameter of negative electrode of the negative corona discharge were investigated. The study also tested the effects of the electrode diameter of the negative corona discharge on ozone generation. The observed decrease in ozone density with the increase in negative electrode diameter was reasonable and consistent with other results provided by researchers in this field.

Breaking of Odd Chirality in Magnetoelectrodeposition of Copper Films on Micro-Electrodes

The surface chirality was investigated in magnetoelectrodeposition (MED) of copper films on micro-disc electrodes with the diameters of 100 and 25 µm. The MED was conducted in the magnetic fields of 1–5 T, which were parallel or antiparallel to the ionic currents. In the case of 100 µm-electrodes, the MED films prepared in 2 and 3 T exhibited odd chirality for the magnetic field polarity, as expected in the magnetohydrodynamic (MHD) vortex model. However, the films prepared in the higher fields of 4 and 5 T exhibited breaking of odd chirality. In the case of the 25 µm-electrode, the broken odd chirality was observed in 2 and 3 T. These results indicate that the strong vertical MHD flows induce the breaking of odd chirality. The mapping of chiral symmetry on the axes of the magnetic field and electrode diameter demonstrate that the odd chirality could be easily broken by the fluctuation of micro-MHD vortices.

Ozone Production in Cylindrical Co-axial Double Dielectric Barrier Discharge Ozone Generator

This study developed an ozone generator of a double co-axial cylindrical dielectric barrier discharge system with air, argon, and oxygen as the working gases. The discharge was produced by using a high voltage power supply of 0 - 18 kV and a line frequency of 50 Hz. The flow rate of air, argon, and oxygen was varied from 1 to 6 L/min. A comparison of O3 generation in air, argon, and oxygen using brass as a central electrode was conducted and it was found that O3 concentration was higher in the case of oxygen than in the air and in argon gases environment for given fixed discharge time, applied voltage, and diameter of the brass electrode. This study revealed that the concentration of ozone increased along with the increase in the applied voltage for constant discharge time and gas flow rate. The O3 concentration also increased with the increase in the discharge time at fixed applied voltage and gas flow rate; however, the concentration decreased with the increase in the gas flow rate at fixed discharge time, applied voltage, and diameter of the electrode. A small reactor with a large inner electrode generated a high concentration of O3. Yet, a reactor with a small diameter, there seemed to have an optimum inner electrode diameter. The glass tube reactor of the internal diameter of 18 mm and the brass electrode of diameter 8 mm were utilized in this study. The ozone concentration was higher for oxygen as feed gas than both in the air and in argon and the O3 concentration was also higher in the air than in argon at fixed discharge time, applied voltage, and diameter of ozone generator. HIGHLIGHTS Ozone concentration increases with increasing applied voltage and discharge time but concentration decreases with increasing gas flow rates Low cost ozone can be produced in DBD reactor at atmospheric pressure Oxygen can be used as feed gas to generate high concentration of ozone than other gases inside DBD generator Optimization of central electrode diameter and gap space inside DBD reactor can help to increase ozone concentration, yield, and efficiency Proper choice of central high voltage electrode also can play the important role for the generation of ozone in DBD chamber GRAPHICAL ABSTRACT

Optimization of TIG Welding Parameters for the 202 Stainless Steel Using NSGA-II

Tungsten Inert Gas welding is a fusion welding process having very wide industrial applicability. In the present study, an attempt has been made to optimize the input process variables (electrode diameter, shielding gas, gas flow rate, welding current, and groove angle) that affect the output responses, i.e., hardness and tensile strength at weld center of the weld metal SS202. The hardness is measured using Vicker hardness method; however, tensile strength is evaluated by performing tensile test on welded specimens. Taguchi based design of experiments was used for experimental planning, and the results were studied using analysis of variance. The results show that, for tensile strength of the welded specimens, welding current and electrode diameter are the two most significant factors with P values of 0.002 and 0.030 for mean analysis, whereas higher tensile strength was observed when the electrode diameter used was 1.5 mm, shielding gas used was helium, gas flow rate was 15 L/min, welding current was 240A, and a groove angle of 60o was used. Welding current was found to be the most significant factor with a P value of 0.009 leading to a change in hardness at weld region. The hardness at weld region tends to decrease significantly with the increase in welding current from 160-240A. The different shielding gases and groove angle do not show any significant effect on tensile strength and hardness at weld center. These response variables were evaluated at 95% confidence interval, and the confirmation test was performed on suggested optimal process variable. The obtained results were compared with estimated mean value, which were lying within ±5%.

Study on the Effect of Structure Parameters on NO Oxidation in DBD Reactor under Oxygen-Enriched Condition

To improve NO oxidation and energy efficiency, the effect of dielectric barrier discharge reactor structure on NO oxidation was studied experimentally in simulated diesel exhaust at atmospheric pressure. The mixture of 15% O2/N2 (balance)/860 ppm NOX (92% NO + 8% NO2) was used as simulated diesel exhaust. The results show that DBD reactor with 100-mm electrode length has the highest oxidation degree of NOX and energy efficiency. NO oxidation efficiency is promoted and the generation of NO is inhibited significantly by increasing the inner electrode diameter. Increasing the inner electrode diameter not only improve the E/N, but also makes the distribution of E/N more concentrated in the gas gap. The secondary electron emission coefficient (γ) of electrode material is closely related to electron energy and cannot be considered as a constant, which causes the different performance of electrode material for NO oxidation under different gas gap conditions. Compared with the rod electrode, the screw electrode has a higher electric field strength near the top of the screw, which promotes the generation of N radicals and inhibits the generation of O radicals. Rod electrode has a higher NO oxidation and energy efficiency than screw electrode under oxygen-enriched condition.

EFFECT OF ELECTRIC ARC WELDING ON IMPACT OF DIFFERENT MILD STEEL WELD GEOMETRIES

The effect of welding parameters (current, electrode diameter) on the impact of low carbon steel specimens was investigated in this work. Two different geometries namely square butt welded joint and double V welded joint were created. The welding operation was carried out at three different current for welding currents of 90, 110 and 130 amps and electrode diameters of 2.5, 3.2 and 4mm respectively. A Charpy impact testing machine was used to evaluate the impact of the welded samples. It was observed that a low current of 90 Amps for all the welding electrode diameters produced high impact values for both the welding geometries. Also, the 3.2 mm electrode diameter was found to be more suitable for welding the square butt and the double V geometry as it yielded higher impact values. Additionally, the double V geometry showed better performance when compared to the square butt geometry for all the combinations of welding currents and electrode diameters.

Pengaruh Variasi Diameter Elektroda E7018 Terhadap Kekuatan Tarik, Kekerasan, dan Struktur Mikro Pengelasan pada Baja Karbon Rendah Jenis SS400 dengan Metode SMAW

Metal welding by the welding method has weaknesses including the decrease in strength of the material and the results of residual stress, as well as the presence of cracks due to the welding process. The purpose of this research is to know the effect of variations in the diameter of the electrode E7018 to tensile strength, hardness, and microstructure on alloysteel SS400 before (raw material) and after welding using welding methodes Shileded Metal Arc Welding (SMAW) methode. This research uses experimental methode. Technique of data analysis used is the comparative descriptive. Based on the results of the reseach, it can be conclude that the result of the micro structure test showed an inrease perlit structure after welding. On raw material, ferrit structure looks prevalent but on welding result using SMAW welding methods with the variation in the diameter of the electrode 2.6 mm, 3.2 mm, and 4.0 mm showed that the ferrit decreases on each specimen, so the perlite structure is very dominating. Value of tensile strength on the welding result showed a difference in tension and strain. Specimen with a diameter of electrode 4.0 mm have a higher tension level and strain is 471.11 MPa and 24.98% if compared to the electrode diameter 3.2 mm specimen is 470.15 MPa and 24.81%, and the electrode diameter 2.6 mm is 462.42 MPa and 20.57%. This research shows that the welding using diameter variation of electrode changed value of the tensile strength, micro structure and effected on the value of hardness alloy Steel SS400.