High-voltage Pulse Technology Research Articles

Study on preparation and anti-sand erosion performance of thick DLC coating combined with FCVA deposition and HVP technology

To address the compatibility issues between the hardness and thickness of DLC coatings and to improve the erosion resistance of engine blades, a thick DLC coating was prepared using a combination of filter cathode vacuum arc (FCVA) deposition technology and high voltage pulse (HVP) technology. The prepared thick DLC coating exhibits low residual stress (1.79 ± 0.087 GPa) and high C-sp3 content (70.13 %), with a thickness and hardness of 18.46 μm and 51.07 ± 0.23 GPa, respectively. The results of anti-sand erosion tests indicate that the mass loss rates of DLC coating at the erosion angles of 45° and 90° are 4.44 × 10−3 mg/g and 1.99 × 10−2 mg/g, respectively. The good erosion resistance of thick DLC coatings is attributed to the consumption of residual impact energy by carbon cluster structures, which prevents the generation and propagation of cracks. Therefore, the thick and super-hard DLC coatings can be prepared by combining FCVA deposition technique with HVP technique, which has great potential applications in the aerospace industry.

Effect of the electrode spacing on dynamic fracture behavior of red sandstone under high-voltage pulse discharge

High voltage pulse technology has broad application prospects in the field of rock fragmentation. Electrical breakdown experiments of red sandstone under the action of high-voltage pulse discharge (HVPD) at different electrode spacings were conducted. The current waveform was recorded using a Rogowski coil. The fracture process on the specimen surface was observed by using an ultra-high-speed camera. The stress wave generated by HVPD was obtained. The experimental results show that both the peak values of the current wave and the stress wave decrease with the increase of the electrode spacing. The surface fracture of the specimen is dominated by transverse fractures parallel to the electrode axis, accompanied by shorter vertical fractures that are perpendicular to the electrode axis. The numerical model is further established to elucidate the three-dimensional fracture process and mechanism of the specimens, and the influence of the electrode spacing on the degree of fracturing is expounded.

Effects of the spacing between plasma channels on the fracture behavior of red sandstone under high-voltage pulse discharge

In rock engineering, high-voltage pulse technology has attracted attention because it offers environmental protection, controllable energy, and repeatable discharge. It is necessary to study the fracture behavior of rock under high-voltage pulse discharge (HVPD) for the parametric design of rock breaking thereby. HVPD experiments were conducted in red sandstone samples with the plasma channel spacing ranging from 26 to 66 mm at intervals of 10 mm. The stress wave generated by HVPD was obtained from the current waveform measured by Rogowski coils. In combination with numerical simulations, the distribution characteristics, propagation process, and formation mechanism of fractures were analyzed. The results showed that after two applications of HVPD at different positions, the sample was both broken down and two plasma channels and radial fractures centered around them were formed within. The stress wave decays exponentially with the increase of the distance from the plasma channel. When the spacing between plasma channels is less than or equal to 46 mm, fracture coalescence occurs between the two plasma channels; thereafter, the fractures formed by the second HVPD face resistance to propagation towards the fracture area formed by the first HVPD. In addition, numerical simulation results indicate that the second HVPD will generate significant tensile stress in the middle region of the two plasma channels, leading to near-horizontal fracture coalescence. When the spacing between plasma channels increases to 56 mm and 66 mm, the tensile stress induced by the second HVPD in the middle region of the sample is small, and it is difficult to form fracture coalescence between the two channels.

Development of high voltage electric pulse charging and discharging device based on functional materials

As a relatively mature energy storage technology, charge/discharge devices are bound to develop significantly in the contemporary society among them energy is increasingly scarce. The traditional charging and discharging device is not smart enough, slow charging and discharging and other shortcomings have limited its further high-speed development. The application of functional materials and high-voltage pulse technology can drive the further development of charging and discharging devices. In this study, a safe, low-cost, functional material with high adsorption capacity was developed. At the same time, this functional material is applied to the charging and discharging device to improve the storage capacity and discharge efficiency of the device. In addition, we combine high-voltage electric pulse technology with charging and discharging technology to improve the charging and discharging rate of the charging and discharging device. It has certain guidance and reference values for the development of high-voltage electric pulse charging and discharging devices. According to the test results, the dynamic adjustment time of the charging module output current is only 20ms, and the dynamic adjustment response time of the discharging module input current is about 0.14s. The device provides a new idea for the development of high-voltage electric pulse charging and discharging equipment.

Mechanism Analysis of Rock Failure Process under High-Voltage Electropulse: Analytical Solution and Simulation.

This work aims to investigate and analyse the mechanism of rock failure under high-voltage electropulses in order to evaluate and increase the efficiency of high-voltage pulse technology in geological well drilling, tunnel boring, and other geotechnical engineering applications. To this end, this paper discusses the equivalent circuit of electric pulse rock breaking, the model of shock wave in electro channel plasma, and, particularly, the model of rock failure in order to disclose the rock failure process when exposed to high-voltage electropulse. This article uses granite as an example to present an analytical approach for predicting the mechanical behaviour of high-voltage electropulses and to analyse the damage that occurs. A numerical model based on equivalent circuit, shock wave model, and elasto-brittle failure criterion is developed for granite under electropulse to further examine the granite failure process. Under the conditions described in this study, and using granite as an example, the granite is impacted by a discharge device (Marx generator) with an initial voltage U0 that is 10 kV and a capacitance F that is 5 µF before it begins to degrade at about 40 µs after discharge, with the current reaching its peak at approximately 50 µs. The shock wave pressure then attains a peak at about 70 µs. Dense short cracks form around granite and the dominant cracks grow to an average length of about 20 cm at around 200 µs. The crack width dcr is predicted to be approximately 1.6 mm. This study detects dense cracks in a few centimetres surrounding the borehole, while around seven dominant cracks expand outward. The distribution of the length of the dominating cracks can be inhomogeneous because of the spatial heterogeneity of granite’s tensile strength, however the heterogeneity has an insignificant effect on the crack growth rate, total cracked area, or the number of main cracks. The mechanism of rock failure under electropulse can be well supported by the findings of numerical simulations and analytical studies.

Математична модель ініціювання розрядного процесу у рідких органічних відходах

In connection with the rapid development of high-voltage pulse technology, the phenomenon of electrical breakdown in a liquid is of increasing interest. Depending on the purpose of the installation, the working chamber can have various sizes and shapes. To process the waste of pig-breeding complexes, we have developed an electropulse installation, the working chamber of which has a cylindrical shape, which allows us to simplify the modeling of processes that will occur during the breakdown of liquid in the chamber. The nature and sequence of the discharge processes of the installation depends on such parameters as the state of the electrodes, their shape of exacerbation, the length of the interelectrode gap, the viscosity of the liquid in the chamber, and the presence of impurities. The use of a high-voltage spark as a “working tool” became the first stage of a complex technological process in which a liquid-insulating working medium. The article gives a generalized scheme of the experimental setup, the questions of mathematical modeling of the optimal operating modes of the electric pulse installation are considered. The features of constructing a mathematical model of the electropulse conversion of energy in liquid are considered. Considerable attention is paid to the process of operation of an electric pulse installation, where the current technological mechanism is pressure pulses that emit in the channel of high voltage discharges in an organic liquid. The effectiveness of the impact of pulses is spatially limited and decreases sharply with increasing distance from the axis of the channel and therefore it must be adjusted during the processing of the liquid. In the calculation mathematical model it is necessary to take into account factors affecting the parameters of the pressure pulse in the liquid and the position of the electrodes in space. The article presents the equations of a linearized mathematical model of the processes that occur in the discharge channel of the working body of the electric pulse installation. Key words: mathematical model, electric pulse installation, liquid organic waste

Preferential sequence crushing of copper ore based upon high-voltage pulse technology

In this study, high voltage pulse breakage was used to study the breakage process of copper ore. The particle size, shape coefficient and preferential crushing index (Δαi) were determined using systematic experiments. The parameters were further investigated by fitting the energy consumption model of breakage to the experimental data. The results showed that the shape coefficient of the completely broken product was stable at 0.82. During the crushing process, the mineral components with large dielectric constant migrated to −0.3 mm fine particle, and the Δαi assumed a value of more than 1. For −0.074 mm particles, Δαi of chalcopyrite and pyrite reached values of 4.51 and 2.74, respectively. The mineral components with small dielectric constant migrated in the opposite direction. For +4 mm particles, Δαi of muscovite was 1.86. The main factors that affected the breakage sequence were the dielectric properties. The results showed that a certain order existed for different mineral components during the fragmentation process: ηc>ηp>ηm. In addition, for higher dielectric constant, the breakage happened earlier. The fitted energy consumption model showed that, with the decrease in grain size, the efficiency of the energy utilization decreased.

Improvement of resistance protection of high-voltage capacitors of powerful capacitive energy storage systems from emergency overcurrent

A resistive protection circuit of high-voltage pulse capacitors with powerful capacitive energy storage (CES) in multimodule implementation from the emergency overcurrents arising in the individual modules of CES when internal or external electric breakdown of isolation of capacitors was proposed. The main distinctive feature of this circuit is separate operation of CES modules at the stage of charging of parallel-connected capacitors and their operation together at the stage of discharge of the capacitor of modules at the total electrical load. This mode prevents the explosion-like destruction of their protective graphite–ceramic fixed resistors of TVO-60 type in an emergency arising upon breakdown of a CES capacitor at the charge stage. The calculation results of the main electrotechnical parameters of the proposed resistive protection circuit are presented. The quantitative determination of such parameters of the protective circuit of CES indicates its practical feasibility in the area of high-voltage pulse technology.

The Dynamic Fracture Process in Rocks Under High-Voltage Pulse Fragmentation

High-voltage pulse technology has been applied to rock excavation, liberation of microfossils, drilling of rocks, oil and water stimulation, cleaning castings, and recycling products like concrete and electrical appliances. In the field of rock mechanics, research interest has focused on the use of high-voltage pulse technology for drilling and cutting rocks over the past several decades. In the use of high-voltage pulse technology for drilling and cutting rocks, it is important to understand the fragmentation mechanism in rocks subjected to high-voltage discharge pulses to improve the effectiveness of drilling and cutting technologies. The process of drilling rocks using high-voltage discharge is employed because it generates electrical breakdown inside the rocks between the anode and cathode. In this study, seven rock types and a cement paste were electrically fractured using high-voltage pulse discharge to investigate their dielectric breakdown properties. The dielectric breakdown strengths of the samples were compared with their physical and mechanical properties. The samples with dielectric fractured were scanned using a high-resolution X-ray computed tomography system to observe the fracture formation associated with mineral constituents. The fracture patterns of the rock samples were analyzed using numerical simulation for high-voltage pulse-induced fragmentation that adopts the surface traction and internal body force conditions.

High-voltage pulsed generators for electro-discharge technologies

A high-voltage pulse technology is one of effective techniques for the disintegration and milling of rocks, separation of ores and synthesized materials, recycling of building and elastoplastic materials. We present here the design and test results of two portable HV pulsed generators, designed for materials fragmentation, though some other technological applications are possible as well. Generator #1 consists of low voltage block, high voltage transformer, high voltage capacitive storage block, two electrode gas switch, fragmentation chamber and control system block. Technical characteristics of the #1 generator: stored energy in HV capacitors can be varied from 50 to 1000 J, output voltage up to 300 kV, voltage rise time ∼ 50 ns, typical operation regime 1000 pulses bursts with a repetitive rate up to 10 Hz.Generator #2 is made on an eight stages Marx scheme with two capacitors (100 kV–400 nF) per stage, connected in parallel. Two electrode spark gap switches, operated in atmospheric air, are used in the Marx generator. Parameters of the generator: stored energy in capacitors 2÷8 kJ, amplitude of the output voltage 200÷400 kV, voltage rise time on a load 50÷100 ns, repetitive rate up to 0.5 Hz. The fragmentation process can be controlled within a wide range of parameters for both generators.

Pulsed Electric Field Processing of Foods: A Review

Use of pulsed electric fields (PEFs) for inactivation of microorganisms is one of the more promising nonthermal processing methods. Inactivation of microorganisms exposed to high-voltage PEFs is related to the electromechanical instability of the cell membrane. Electric field strength and treatment time are the two most important factors involved in PEF processing. Encouraging results are reported at the laboratory level, but scaling up to the industrial level escalates the cost of the command charging power supply and of the high-speed electrical switch. In this paper, we critically review the results of earlier experimental studies on PEFs and we suggest the future work that is required in this field. Inactivation tests in viscous foods and in liquid food containing particulates must be conducted. A successful continuous PEF processing system for industrial applications has yet to be designed. The high initial cost of setting up the PEF processing system is the major obstacle confronting those who would encourage the system's industrial application. Innovative developments in high-voltage pulse technology will reduce the cost of pulse generation and will make PEF processing competitive with thermal-processing methods.

Acting on impulse: applications of HV pulse technology

High-voltage pulse technology began in the 18th century with the first attempts to simulate lightning. From the 1890s to the 1970s its importance in industrialised countries was concerned mainly with the development of HV and EHV transmission systems. The last two decades, however, have seen explosive growth of new applications in the aerospace, energy, defence, manufacturing and process industries. The paper describes the switching and pulse-forming techniques used to achieve features such as ultrafast risetime and high peak power, and reviews the use of HV pulse technology in a wide range of applications including fusion reactors, lasers, mineral extraction and processing, high-speed imaging and pollution-control systems.

Survey of high-voltage pulse technology suitable for large-scale plasma source ion implantation processes

Many new plasma processes ideas are finding their way from the research lab to the manufacturing plant floor. These require high voltage (HV) pulse power equipment, which must be optimized for application, system efficiency, and reliability. Although no single HV pulse technology is suitable for all plasma processes, various classes of high voltage pulsers may offer a greater versatility and economy to the manufacturer. Technology developed for existing radar and particle accelerator modulator power systems can be utilized to develop a modern large scale plasma source ion implantation (PSII) system. The HV pulse networks can be broadly defined by two classes of systems, those that generate the voltage directly, and those that use some type of pulse forming network and step-up transformer. This article will examine these HV pulse technologies and discuss their applicability to the specific PSII process. Typical systems that will be reviewed will include high power solid state, hard tube systems such as crossed-field ‘‘hollow beam’’ switch tubes and planar tetrodes, and ‘‘soft’’ tube systems with crossatrons and thyratrons. Results will be tabulated and suggestions provided for a particular PSII process.

Triggering regime of oil-filled trigatron dischargers

A comparative analysis made in [1, 2] of different types of regulable high-voltage dischargers with liquid insulation showed that trigatrons are currently the most promising for use in high-voltage pulse-operated devices due to their simplicity and reliability. Two basic mechanisms of discharge initiation can be realized in trigatrons — initiation by intensification of the field in the region of the control electrode [2, 3], and triggering by a spark in the ignition gap [4, 5]. The first type of trigatron has been studied sufficiently only for short voltage periods [3, 6, 7], so it is used mainly in switching the pulse-shaping lines of powerful nanosecond pulse generators with “rapid” (0.5–1.5 μsec) charging [8, 9]. Almost no use is now made of the second type of trigatron switch in high-voltage pulse technology due to its unsatisfactory time characteristics. Here we report results of a study of the time characteristics of both types of oil-filled trigatrons operating in a regime whereby they form the leading edge of rectangular voltage pulses with amplitudes up to 800 kV and durations of 1–100 μsec. The goal is to find the optimum conditions for triggering of trigatron dischargers with liquid insulation in the region of microsecond voltage discharges. Experiments were conducted on the unit in [10]. The test discharger was placed in a cylindrical chamber 45 cm in diameter and 27 cm in length. The high-voltage electrode of the discharger was in the form of a cylinder 20 cm in diameter positioned coaxially inside the chamber. The 10-mm-diameter ground electrode was positioned radially in a branch pipe 8 cm long. The control electrode was placed in a 2-cm-diameter hole in the center of the ground electrode. The chamber with the test discharge was filled with transformer oil with a breakdown voltage of about 50 kV. The oil was not replaced or cleaned during the experiment. We did not find that contamination of the oil by discharge products had any effect on the time characteristics of either type of discharger. The results were analyzed by the least squares method, with 50 measurements to a point (it was found that time lag of the discharger triggering conforms approximately to a normal distribution law for both types of discharger).