Spark Energy Research Articles

Повышение искробезопасности в системах импульсного питания потребителей в сравнении с системой питания постоянным током

The purpose of the work is to evaluate the magnitude of the arc sparking energy during switching in the wires of a pulsed power supply system when compared with the energy when powered from a direct current source and to determine the flammable currents of the methane-air mixture to improve intrinsic safety. Methodology. The research methodology is based on the fundamental principles of the application of the theory of electrical engineering, the theory of planning a scientific experiment, computer and simulation modelling. The experimental data were obtained in the laboratories of the Kremenchuk Mykhailo Ostrohradskyi National University using certified metrological measuring instruments. The system was modelled using the software packages Matthcad, Microsoft. EXCEL. StatGraphik. Results. Conducted theoretical and experimental studies of the magnitude of arc sparking prove that the energy of sparking with a pulsed current is less than with a constant one and can be used as the basis for reducing the ignition of gas in mines and other explosive industries. Scientific novelty. The useful use of the consumer’s reactive energy has been substantiated if the supply line or the current source is shut off for the duration of the pause and at the same time the consumer is shunted. Practical significance. The obtained results are recommended to be used in power supply systems of consumers that operate in a pulsed mode to increase their energy efficiency and explosion and fire safety of operation.

A study of machining characteristics of AISI 4340 alloy steel by wire electrical discharge machining process

However, over the past fifty years the rapid growth in the development of harder, tougher and stronger work piece materials. The 4340 steel is a medium carbon, low alloy steel (Heat-treatable). It has excellent toughness, superior strength in the heat treated condition, good fatigue resistance, admirable hardness and wear resistance. The 4340 steel is widely used in different applications as: Automotive system, Aircraft landing gears, transmission, Gas & oil sectors, forged hydraulic and structural areas. A WEDM is a non-contact erosion cutting process. It has a capability of machining parts with varying hardness, intricate shapes, contours and complex shapes. The WEDM is a competitive and economical machining option fulfilling the demanding machining requirements. In WEDM the electric sparks is generated between the tool and workpiece and it used to cut the various types of electrical conductive as well as non-conductive materials. The machining process is controlled by various process parameters such as pulse on time, pulse off time and servo voltage. It was found that servo-voltage and pulse on time are the significant factors affecting the SR. While increases the pulse off time and pulse duration affects the MRR, as the reason of pulse off time limits the spark energy and interrupting the discharge energies. From the experimental result, increases the pulse duration, wire speed, open circuit voltage causes the increases in material removal rate. The wire speed and wire tension play the dominant role in the machining of 4340 steel. Machining with zinc coated brass is found to be the best alternative to the 4340 alloy steel.

Electrical Waveform Measurement of Spark Energy and its Effect on Lean Burn SI Engine Combustion

<div class="section abstract"><div class="htmlview paragraph">The conventional transistor coil ignition system with coil-out energy up to 100 mJ might not be sufficient to establish a self-sustained flame kernel under lean combustion with strong in-cylinder flow motion. Further increase of the discharge current will decrease the voltage across the spark gap, which will affect the calculation of the energy delivered to the spark gap. In this paper, the relationship between the discharge current and gap voltage is investigated, and it is discovered that the spark energy doesn,t increase monotonously with the increase of the discharge current. However, engine test results still indicate a positive impact of discharge current amplitude on the engine performance.</div></div>

Electro spark deposition of WC–TiC–Co–Ni cermet coatings on St52 steel

The electro spark deposition (ESD) technique has been successfully applied to deposit a cermet layer of WC/TiC/Co/Ni at room temperature on a St52 carbon steel substrate and the electrochemical properties of the bare and coated samples were evaluated. Influence of ESD process parameters on electrochemical properties of coatings were examined by using of potentiodynamic polarization and impedance spectroscopy (EIS) techniques. It has been possible to obtain a dense coating with adjusting the ESD process as the current limit of 15 A, frequency of 11 KHz, duty cycle of 50%, rotating speed of 200 rpm and spark energy of 1.46 mJ. The results confirmed that the sample with these fabrication parameters had higher ESD efficiency with the value of 64% and the dense coating without holes and micro cracks could be fabricated through the process. The electrochemical tests also confirm the good quality of the optimized coated sample. According to the results, the largest corrosion resistance with maximum Rcoat 76.16 Ω cm2 was observed in optimized coating condition.

Effect of ElectroSpark Process Parameters on the WE43 Magnesium Alloy Deposition Quality

This research aims to investigate the effects of process parameters on the quality of WE43 coatings deposited on homologue substrate by ElectroSpark Deposition (ESD) technology. ESD is new technology used to apply coatings or for the restoration and refurbishment of worn or damaged high valued parts. The depositions were processed using five different levels of Energy input (Es, Spark Energy). The microstructure of both the base material and deposits cross-section were characterized by optical and scanning electron microscopies. Also, X-ray diffraction technique was used. In addition, stereological studies of the through-thickness heterogeneities of the deposits (e.g., voids) were performed. The mechanical properties were evaluated by Vickers micro-hardness. The results show that the deposits exhibited a fine grained microstructure due to the rapid solidification. The average micro-hardness values of the deposits are lower than that of the substrate and distributed in a small range (49–60 HV). The lower hardness of the deposits respect to the base material is due to the presence of defectiveness such as spherical, laminar and random shaped voids. The defects area percentage inside the deposits remains well below than 11%. All the deposits were mainly affected by laminar morphology defects. The results indicate that the deposits defectiveness decreases as the energy input increases.

Effect of machining parameters on cutting force during micro-turning of a brass rod

ABSTRACTMicro-needles finds abundant applications in the field of medicines, nanodevices and as a tool for µ-EDM to study single spark energy. Fabrication of such micro-needles with high accuracy and precision is a challenging task. In this work, an attempt has been made to manufacture a brass rod by micro-turning to a diameter of 100 µm. Effects of cutting speed and feed rate on feed-force, cutting-force, machining-force, surface-roughness, power, and specific cutting force have been studied to optimize the process of fabricating a brass micro-needle with a smoother surface. SEM, EDS, and AFM have been performed to study cutting behavior along with the fracture behavior of fabricated micro-needle. The cutting force behavior was non-linear and was in accordance with the available literature even at micro-level. In addition to this, the fabricated micro-needles were etched using hydrogen peroxide (H2O2) to fabricate a sharp-pointed needle having a diameter of ≤ 10 µm. Fabricated µ-turned sharp micro-needles may be further used as a tool to study single spark energy in the µ-EDM process. Additionally, crater depth, diameter, tool wear rate (TWR) and material removal rate (MRR) have been calculated for the single spark of the µ-EDM process using fabricated micro-tool.

Multi-Criteria Decision Making Using Preferential Selection Index in Titanium based Die-Sinking PMEDM

Powder mixed electrical discharge machining (PMEDM) is a new machining technology. The optimization of process parameters in PMEDM is being researched. The determination of the value of the weights of quality indicators in a multiobjective optimization problem is often complex and difficulty. Preferential selection index (PSI) is a new computational technique for solving multi-objective problems. This contributes to the process of solving the multi-objective optimization problems. In this study, material removal rate (MRR) and surface roughness (SR) were optimized with the help of the PSI method. The specimen and tool materials, electrode polarity, current, pulse-on-time, pulse-off-time and powder concentration were considered. The investigation showed that powder concentration can increase MRR with lower SR. The most significant factor was the electrode material. The optimal values were found as SKD11 (workpiece), Gr (tool), + (polarity), 5 ㎲ (ton), 57 ㎛ (toff), 8A (current) and 10 g/l (powder concentration) with a high accuracy of 7.82%. The electrode material and powder concentration could provide strong influence on the performance measures owing to their importance on determining spark energy in the PMEDM. The research results were compared with those of TOPSIS, GRA and MOORA methods. In conclusion, PSI is the method for the highest efficiency.

Potential of electrical discharge treatment to enhance the in vitro cytocompatibility and tribological performance of Co–Cr implant

Abstract

Effect of diluted dielectric medium on spark energy in green EDM process using TGRA approach

Abstract In the present situation, it is very important for modifying any manufacturing process into eco friendly process to reduce the environmental pollutants and hazardous substances. In electrical discharge machining process, the dielectric breakdown of insulating medium causes on liberating the toxic gases from the machining zone. In the present study, a research endeavor was performed to analyze the influence of process parameters with normal tap water mixed deionized water as insulating medium. It has been inferred that proposed dielectric medium can provide considerable machinability while machining titanium alloy. The optimum combination has also been found using Taguchi Grey-relational approach to achieve better multiple response parameters in the proposed eco friendly electrical discharge machining process. However, the material removal mechanism with proposed dielectric medium in EDM process may be affected due to stochastic and higher electrical conductivity of the insulating medium.

Effect of Combustion Reaction Based on Capacitive Discharge Ignition in Air-Propane Equivalence Ratio

The main purpose of this research work is to demonstrate the effective plasma of capacitive discharge ignition (CDI) comparing with conventional ignition discharge. A constant volume combustion chamber (CVCC) with a volume of 450 cm3 is developed to study thermochemical combustion process. The experimental conditions set 2, 3 and 4 bar for initial pressure, 363 K of chamber temperature, 1.00, 1.25 and 1.50 mm of electrodes gap, 1 ms of discharge time, 100 mJ in spark energy and λ = 1.0 to 1.7 in air-C3H8 equivalence ratio. In order to validate the collected data and verify the repeatability of experimental study, the experiments are repeated 10 times. The discharge effect of CDI is demonstrated to significantly enhance the combustion reaction, flame propagation and internal flame kernel comparing with conventional ignition discharge. Due to electron impact dissociation (EID) and breakdown strength (BS) increases, the effective plasma of CDI is shown to effectively propagate the flame kernel under the combustion reaction more than conventional ignition discharge inside CVCC. Consequently, the combustion reaction by CDI is verified that in CVCC diluted with the rarefied air-C3H8 equivalence ratios, the converting efficiency is much more active than conventional ignition energy.

A new look on the electric spark sensitivity of nitramines

Abstract Electric spark energy, EES, for a 50% probability of initiation of the 14 nitramines was determined using a measuring instrument in which the electrodes are in direct contact with the sample. Indirectly proportional relationships were established between the logarithm of the EES values and the length of the longest N–N bond in the nitramine molecule. This finding is compatible with the mechanism of the first step in the electro-reduction of the nitramine grouping. Directly proportional relationships were found to exist between the EES values and the crystal lattice free volumes, ΔV (i.e. an increase in the ΔV values increases the nitramine's resistance to electric sparks) but there were several nitramines with the opposite course of this relationship. Also a semilogarithic relationships between the EES values and a ratio of intrinsic volumes of molecule, Vint, to the ΔV values were described as well as ambiguous linear dependence between these energies and a sum of the positive and negative extremes of the molecular surface electrostatic potentials, VS,Σ. Several nitramines studied (always the same ones) display roughly the same distribution in the coordinate systems of relationships with lengths of the longest N–N bonds, the Vint/ΔV ratio and the sum VS,Σ as the independent variables. It was found that, typically, such relationships start from a single identical point, in effect a point corresponding to data for a structural unit from which the studied nitramines can be hypothetically generated, and/or are converging on another point, often the one corresponding to the data for HNIW. All the findings point to a fundamental influence of the intermolecular forces on reactivity of nitramines exposed to electric sparks.

Molecular dynamics simulation of single discharge and dimensionless correlation with actual material removal in micro electrical discharge machining

ABSTRACTShorter time pulses and length scales in micro EDM (MEDM) makes it difficult to observe the material removal phenomena taking place at very small zone during discharge. Since numerical or analytical model considers material to be uniform/isotropic, it cannot predict the discrete effects viz. crystal structure distortion due to discharge. Also, little attention has been given to the mechanism of material removal in MEDM at the atomistic level. Therefore, to understand the behaviour of material removal and crystal structure distortion due to single spark in MEDM, MD simulations have been carried out. Based on MD simulations, it was found that the percentage of material removed by vaporisation (∼40%) was higher at spark energies used in this model as compared to spark energies used by Wong et al. (20% at 23.50 µJ). Conversion from FCC crystal structure to amorphous was observed at the top surface of crater in both cases; the one with higher spark energy has marginally higher distortion indicating higher amorphisation. A new method is proposed based on which a dimensionless correlation was obtained between results of MDS and experiments which relates the ratio of specific material removal at higher spark energy to that at lower energy for both MDS and experiments.

An experimental parametric analysis on performance characteristics in wire electric discharge machining of Inconel 718

Wire cut electrical discharge machining was identified as a good alternative to conventional machining for machining super alloys that possess low machinability. In the present work, effect of wire tension along with current, pulse on time, and pulse off time on the performance characteristics such as spark gap, surface roughness, amplitude of wire vibration, and cutting rate were studied in wire cut electrical discharge machining of Inconel 718 metal. Experiments were conducted at five levels of the process parameters as per orthogonal array of L25 and their results were collected. These experimental results were analyzed and the interaction effect of wire tension along with current, pulse on time, and pulse off time on performance characteristics was studied using analysis of variance. Response models were developed for the four responses in terms of process parameters and the accuracy of such models was tested. In addition to the above studies, effect of the wire displacement on the kerf size, cutting rate was studied. Spark energy was also estimated for all the experiments and its effect on the performance characteristics was studied. The response models developed in this study were able to predict the experimental results i.e. amplitude of wire vibration, surface roughness, cutting rate, and spark gap with an accuracy of R2 values of 1.0, 0.96, 0.88, and 0.99, respectively. Interaction effect of current and wire tension was found to have the most significant effect on the amplitude of cutter vibration and surface roughness.

In vitro corrosion and hemocompatibility evaluation of electrical discharge treated cobalt–chromium implant

Abstract

Erosion processes of electrodes – Experiments and modeling

The scope of this work was to identify and examine lifetime limiting processes of spark plugs as used in stationary gas engine applications. Experimental investigations and analytic methods were applied in order to analyze and understand the wear process, especially in terms of electrode material. Physical parameters to describe rate of oxidation and diffusion processes were obtained and employed to set up a simulation model capable of lifetime prediction. Parameters not directly measurable, such as temperature load where the arc strikes the electrode, are extracted from a separate local, in-depth thermal analysis. Furthermore, ignition parameters such as level of ignition current and spark duration were systematically varied to determine their impact on the ignition system and to refine the wear model. Field tests on a Jenbacher Type 6 Gas engine have been conducted to observe the erosion of electrodes in gas engines due to the main contributing factors: combustion, spark energy input and oxidation. Using a specific spark plug test rig where combustion does not take place, the processes can be reduced to either spark energy impact or oxidation. Long-term testing as well as single spark experiments provide greater insight into the wear rate. Following this test rig step, the erosion of the electrode material caused by oxidation alone was investigated in a furnace using thermogravimetry. Before and after the tests, optical inspections (DOF), computer tomography (CT), energy dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD) and differential thermal analysis (DTA) were applied to analyze the electrode material. The understanding of wear phenomena obtained from these experiments in combination with the new simulation model developed provide the opportunity to predict lifetime and to evolve more durable spark plug designs.

Design of a test rig for fundamental investigations of spark characteristics

A common means to increase efficiency in stationary spark ignited engines is to operate the engine with a higher air/fuel ratio of the mixture in conjunction with a higher turbulence level; however, this generally leads to severe conditions that significantly impact the inflammability of the gas–air mixture and combustion stability. Because the electric arc that forms at the spark plug is a main influencing factor in combustion, detailed research work in the field of electric arc behavior generated at spark plugs is required. This article thus presents a specially tailored test rig that is designed to facilitate an investigation of electric arc behavior under cross-flows at a spark plug typically used in gas engines. The test rig consists of a closed flow circuit for inert gases; its centerpiece is a test cell that provides optical access for high-speed imaging of the electric arc behavior at the spark plug. The required flow velocity at the spark plug is set with a blower. Flow velocities up to 30 m/s, pressures up to 60 bar and temperatures up to 80 °C can be achieved inside the flow system at the location of the spark plug. Postprocessing algorithms have been developed to automatically extract information from the high-speed images. The results reveal that the arc stretches more at a higher flow velocity as indicated by its greater arc length. In addition, it is evident that the cycle-to-cycle variation in arc length increases at higher flow velocities. The secondary voltage history and its cycle-to-cycle variation are strongly influenced by the arc length. This is reflected in the cycle-to-cycle variation of the spark energy input to the flowing gas. These results support the conclusion that spark behavior itself can be a substantial source of cycle-to-cycle variation in the combustion process observed in spark ignited gas engines.

Thermal analysis for the large precision EDM machine tool considering the spark energy during long-time processing

Thermal error is a major factor influencing the accuracy of large precision electrical discharge machining (EDM) machine tools, especially when processing continuously for a long time. In this paper, a novel thermal analysis model was set up to identify the static and dynamic thermal behaviour of the large EDM machine tool. The thermal effect of multiple spark discharges is considered. An equivalent heat flux method was proposed to model the intermittent heat flux for the first time. Both the steady and transient analyses were applied to investigate the thermal equilibrium time of critical points. It is found that when the study point is far away from the heat source, the longer thermal equilibrium time is needed. And the thermal equilibrium time of the machine tool was also estimated. Verification experiment has been performed, indicating the simulation accuracy of 87 % on the temperature rise of the electrode. Moreover, on the displacement of the spindle, the simulated result matched with the experimental result in Z direction error of 7 %. Finally, suggestions for reducing the thermal deformation were proposed to further improve the machining accuracy of large EDM machine tools.

Microstructure characterization and maximization of the material removal rate in nano-powder mixed EDM of Al-Mg2Si metal matrix composite—ANFIS and RSM approaches

Al-Mg2Si in situ composite is a new metal matrix composite (MMC) with numerous applications in different engineering fields. MMCs are considered difficult-to-cut materials due to the abrasive nature of the reinforcement (e.g., Mg2Si), hardness, and built-up edge. Hence, electrical discharge machining (EDM) is one of the alternative ways to machine Al-Mg2Si. With EDM, it is possible to machine conductive materials with different strength, temperature resistance, and hardness as well as produce complicated shapes, high-aspect ratio slots, and deep cavities with precise dimensions and good surface finish. The experiments in this study were designed by response surface methodology (RSM) and ANFIS was utilized to analyze the nano-powder mixed EDM (NPMEDM) of Al-Mg2Si in situ composite. The study represents the impacts of NPMEDM parameters on changes in microstructure and material removal rate (MRR). The results revealed that among all interactions, the current-voltage and current-pulse ON time interactions have the most significant effect on MRR. Moreover, current has most significant effect, followed by voltage, pulse ON time and duty factor. An analysis of the Al-Mg2Si microstructure demonstrated that current, pulse ON time, and voltage have remarkable impact on the microstructure, size of craters, and profile of the machined surface. Moreover, decrease in spark energy leads to less microstructural change and better surface finish.

Experimental investigation on wire electric discharge machining (WEDM) of Nimonic C-263 superalloy

ABSTRACTNimonic C-263 superalloy offers a wide range of outstanding properties, namely, high-temperature resistance, high specific strength, high thermal fatigue, and hot corrosion resistance. The concern of the present study is mainly focused on the effect of wire electrical discharge machining (WEDM) process parameters namely, spark energy, spark frequency, and peak current on surface roughness, average cutting rate, and surface integrity aspects of Nimonic C-263 superalloy by using one-parameter-at-a-time (OPAT) approach. Surface roughness and average cutting rate were showing the increasing trend with the spark energy and peak current and reverse trend with the spark frequency. Surface integrity aspects of Nimonic C-263 such as surface topography, surface morphology, recast layer thickness, elemental composition, and phase analysis have been also considered in this study. Scanning electron microscope (SEM) micrograph of the machined surface shows the presence of micro-voids, discharge craters, micro-globules, and droplets of molten material. A recast layer of minimum thickness, with less transfer of foreign atoms (Mo, C, and O) from dielectric fluid and molybdenum wire, has been formed at lower spark energy compared to higher spark energy. The various compounds of Ni, Fe, Al, and Ti such as Fe1.2Ni0.8, Fe1.5Ni0.5, Co0.06Fe0.94, and Alo.29Ni0.27Ti0.44 were formed on the machined surface identified through analysis of XRD peaks.

Sparkplug ignition of mono- and bi-dispersed aluminum-air suspensions

In the present paper we numerically investigate the problem of spark ignition of monodispersed and bi-dispersed aluminum suspension in the air. The aim of the research is to determine the critical ignition conditions for an aluminum suspension depending on the size and mass concentration of the particles and the fraction distribution. The mathematical formulation of the problem is determined by a system of equations written in a cylindrical coordinate system, consisting of the gas continuity equation, the momentum and energy conservation equations for the gas and particles, oxygen and particles mass balance equations, the particle number density equation and the gas state equation. To solve the problem numerically we use the algorithms of arbitrary discontinuity decay and disintegration of a discontinuity in a medium devoid of its own pressure. We conduct parametric study on the minimum spark energy which is required to ignite the mixture and provide the subsequent steady propagation of the flame in the aluminum-air suspension.