High-voltage Pulsed Discharge Research Articles

Prediction of plasma path and analysis of axial fracturing properties in rock fragmentation by high-voltage pulsed discharge (RHPD)

Rock fragmentation by high-voltage pulsed discharge (RHPD) is widely utilized in resource recovery and energy extraction due to its low energy consumption and high efficiency. However, observing the plasma development process during RHPD presents challenges, and the frequency dependence of dielectric properties further complicates plasma path prediction and the analysis of fracturing properties in the axial direction of the plasma. To address these issues, we analyzed the development properties of plasma within rocks and established a segmented breakdown criterion that considered the propagation velocity of plasma. Additionally, utilizing a transient electromagnetic field model and a particle flow model (PFM), we established a multi-physics field model and proposed a predictive method for the plasma path in a rock–liquid combination environment. This allows for the quantification of the velocity, potential, and length of the plasma. Furthermore, we computed the time response of shock waves and analyzed the loading mechanism of shock waves. Based on the spatial distribution of plasma, the PFM was applied to simulate the fracturing properties of rocks under shock wave loading. Finally, we established a comprehensive experimental platform for RHPD and conducted three-dimensional reconstructions of the fractured area to validate the accuracy of plasma path prediction methods and fracturing properties analysis. This study significantly advances plasma development theory and provides insights for optimizing rock fragmentation efficiency.

Electric discharge process modelling when piston pins recovery in internal combustion engines

Introduction. The relevance of the topic of the presented article is determined by the improvement of the technology for repairing and restoring machine parts. Currently, the technology of restoring piston pins of internal combustion engines (ICE) by a high-energy method of plastic deformation of metal using the energy of a high-voltage pulse discharge in a liquid is widely used – the electrohydraulic effect, and on its basis electrohydraulic processing. The purpose of the article is to increase the efficiency of the method of restoring piston pins of internal combustion engines due to the use of the electrohydraulic distribution method.Materials and methods. The research methods such as the analysis of the degree of influence of the electrical parameters of the electrohydraulic distribution process on the amount of deformation of the piston fingers depending on the relevant material were used. The article discusses a mathematical model of the electric discharge process when restoring piston pins. The calculation method determines the modes and parameters of the process of electrohydraulic distribution of piston pins while maintaining their fatigue life, static strength and wear resistance.Results. In this work, the degree of influence of the electrical parameters of the electrohydraulic distribution process on the amount of deformation of the piston pins, depending on the product material used, is established. A mathematical model of the electric discharge process during the restoration of piston pins has been developed, and based on them, the modes and parameters of the process of electrohydraulic distribution of piston pins have been determined while maintaining their fatigue life, static strength and wear resistance.Discussion and conclusions. The studies have shown that exploding wires made of iron, copper, and tungsten are not effective in restoring piston pins with an internal radius of up to 10 mm. The pressure in the case of their use does not exceed 100 MPa. Exploding Al wires with a diameter of less than one millimeter have the greatest effect. In this case, the inductance of the circuit should be minimal, because this provides the largest share of the energy released in the discharge channel from all stored in the capacitor. This ensures the highest pressure in the channel. Based on the same considerations, the capacity should be limited to a range of 3-12 UF. This method can be applied to the restoration of other car parts.

Effect of electric pulse treatment on silver recovery from spent solar panel sheet by acid-leaching

AbstractThe number of spent photovoltaic (PV) panels is expected to increase significantly in the coming decades. Crystalline silicon photovoltaic cells contain materials, such as silver, copper, aluminum, silicon, glass, and resins. Approximately 600 g/t of silver is used as a current collector, so-called finger wires, in photovoltaic modules; therefore, silver recovery is an important issue. To establish an effective recycling process for spent photovoltaic panels, a wire explosion method using high-voltage pulsed discharge was investigated to expose and separate silver selectively. In this study, acid-leaching experiments were conducted on spent ground photovoltaic panels with and without electric pulse treatment to verify the effect of the pulse treatment on acid-leaching of silver. Electric pulse treatment improved both the maximum silver recovery rate and leaching speed. Leaching experiments were also conducted using photovoltaic samples from three different silver exposure states. It can be concluded that silver recovery was strongly controlled by the exposure state and that the electric pulse treatment could effectively promote silver exposure of spent PV panels, even in the region where the silver wires were not energized.

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.

Study on fracture characteristics and mechanisms of red sandstone under high-voltage pulse discharge

To investigate the influences of geometrical size and discharge voltage of the pulse discharge equipment on the fracture characteristics and mechanisms of sandstone under high-voltage pulses, a series of experiments was conducted using a high-voltage pulse discharge device on sandstone circular disc specimens of sandstone with a thickness of 10 mm. These experiments covered a range of disc diameters ranging from 50 mm to 142 mm and discharge voltages from 15 kV to 40 kV. Through these experiments, the fracture characteristics of sandstone at both macroscopic and microscopic levels were investigated. In the experiments, a quantitative analysis of surface fracture was undertaken based on fracture density and fractal damage. Additionally, using the principle of energy equivalence, numerical simulation methods were used to study the damage evolution process in sandstone. The research results indicate that the formation and distribution of fractures in the sandstone specimens are significantly affected by geometrical size and discharge voltage. By analyzing the interaction between stress waves and fracture propagation, combined with indoor experimental results, the fracture mechanism was revealed. The high temperature and shock wave generated by the plasma channel leads to the crushing zone near the electrode, while the circumferential tensile component of the stress wave can result in radial fractures, and the reflected tensile wave leads to circumferential and radial fractures near the boundary.

Transverse magnetic field effects on the high-voltage pulsed discharge plasma in helium

This study investigates the effect of a transverse magnetic field on high-voltage pulsed discharge in helium at a pressure of 30 Torr. A simple two-dimensional fluid model that describes the high-voltage pulsed discharge in helium in a transverse weak magnetic field (B = 0.4 T) is presented, which uses an empirical relation to account for the magnetic field. The results of using the empirical relation for the effective field agree well with the experimental results. The dynamics of discharge development in the presence of the magnetic field is also investigated. The magnetic field does not significantly affect the gas-discharge development dynamics in helium at a pressure of 30 Torr.

The plasma path development model (PPDM) in rocks during rock breaking by high-voltage pulse discharge

High-voltage pulse discharge rock-breaking technology (high-voltage pulse discharge rock-breaking technology, HPDT) is widely used in the energy mining industry. In HPDT, in order to analyze the path distribution characteristics of plasma, based on the homogeneous dielectric breakdown theory, the segmental breakdown criterion for the plasma path is proposed. The plasma path development model (plasma path development model, PPDM) is established with the help of the discrete element method, finite element method, and numerical calculation method. For a typical granite-liquid combination, the development process and distribution characteristics of the plasma path inside the rock are calculated for different distances between electrodes. The results show that the fracture of rock is the result of air gap breakdown. Finally, the accuracy of the model is analyzed and the method to reduce the error is given. This work lays a foundation for quantifying the crushing efficiency of HPDT and improving its application range.

Study on Formation of Interstellar C7H from Reactions C4 + C3H2 and C4H + C3H.

We interrogated C7H produced from reactions C4 + C3H2/C4H + C3H → C7H + H using both translational and photoionization spectroscopy. Reactants C3H, C3H2, C4, and C4H were synthesized in two crossed beams of 1% C2H2/He ignited by pulsed high-voltage discharge. The individual contributions of reactions C4 + C3H2 and C4H + C3H to product C7H were evaluated as 17:83 from reactant concentrations in both molecular beams. The translational energy distribution, the angular distribution, and the photoionization efficiency curve of product C7H were unraveled. C7H was identified as the most stable linear isomer by its photoionization efficiency curve that features two ionization thresholds corresponding to separate transitions to singlet and triplet states of l-C7H+. The quantum-chemical calculations indicate that the associations of C4 with C3H2 and C4H with C3H incur no entrance barriers, and the most favorable exit channel leads to product l-C7H + H. It is the first time demonstrating that C7H is producible from reactions 1,3C4 + 1C3H2 and 2C4H + 2C3H on the lowest-lying singlet and triplet potential energy surfaces of 1,3C7H2. This work implies that the reactions of C4 + C3H2 and C4H + C3H might have contributions to interstellar C7H to some extent as compared with the C + C6H2 reaction commonly adopted in an astrochemical model.

Analysis of spatial damage characteristics of rock under multiple high-voltage pulse discharges: I. Cross-section characteristics

Rock breaking by high-voltage pulse discharge (rock breaking by high-voltage pulse discharge, RHPD) is an efficient technology for rock breaking. A single discharge will lead to the initiation or expansion of cracks inside the rock, and the expansion of cracks after multiple discharges will lead to the destabilization of the rock and finally produce a fractured zone. Because of the difficulty in quantifying the spatial damage characteristics of the fractured zone, in this paper, based on the discrete element method and theoretical analysis, the spatial damage model (spatial damage model, SDM) of rock is established. For a typical liquid-solid combination, from the microscopic point of view, the damage characteristics of the fractured zone on the radial cross-section of the plasma are quantified. The changing characteristics of the damage characteristics were analyzed for multiple discharges. In addition, an experimental platform has been built, and the accuracy of the SDM has been verified by the experimental results. The results show that the increase in the discharge distance will improve the deposition energy and crushing effect, and will also improve the accuracy of the model. The findings of this paper provide a technical reserve for the application of RHPD.

Enhancement of magnetization roasting of hematite ore by high voltage pulse discharge

High voltage pulse discharge (HVPD) is a new type of crushing technology with good application. Existing studies have focused on the crushing characteristics, with less reports on follow-up work. This study magnetization roasts hematite ore after mechanical crushing and HVPD, analyzing the difference in the roasting effect between the two crushing methods by establishing a new system of HVPD-magnetization roasting. For a roasting temperature of 500 °C, roasting time of 30 min and number of pulses of 100 times, the grade and recovery of magnetic separation concentrate obtained from HVPD products after secondary separation were 64.69% and 82.05% respectively, which were 0.28 and 1.96 percentage higher than those of mechanical crushing. X-ray diffraction (XRD), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) were used to analyze the process and showed that the specific surface area, pore volume and average pore size of the HVPD products were improved. Grain boundary fracture and burn marks were present in the HVPD products.

Probing NV and SiV charge state dynamics using high-voltage nanosecond pulse and photoluminescence spectral analysis

Nitrogen-vacancy (NV) and silicon-vacancy (SiV) color defects in diamond are promising systems for applications in quantum technology. The NV and SiV centers have multiple charge states, and their charge states have different electronic, optical and spin properties. For the NV centers, most investigations for quantum sensing applications are targeted on the negatively charged NV (NV−), and it is important for the NV centers to be in the NV− state. However, it is known that the NV centers are converted to the neutrally charged state (NV0) under laser excitation. An energetically favorable charge state for the NV and SiV centers depends on their local environments. It is essential to understand and control the charge state dynamics for their quantum applications. In this work, we discuss the charge state dynamics of NV and SiV centers under high-voltage nanosecond pulse discharges. The NV and SiV centers coexist in the diamond crystal. The high-voltage pulses enable manipulating the charge states efficiently. These voltage-induced changes in charge states are probed by their photoluminescence spectral analysis. The analysis result from the present experiment shows that the high-voltage nanosecond pulses cause shifts of the chemical potential and can convert the charge states of NV and SiV centers with the transition rates of ∼MHz. This result also indicates that the major population of the SiV centers in the sample is the doubly negatively charged state (SiV2−), which is often overlooked because of its non-fluorescent and non-magnetic nature. This demonstration paves a path for a method of rapid manipulation of the NV and SiV charge states in the future.

New insights on the breakage mechanism of magnetite quartzite via high voltage pulse discharge: liberation, property difference, micro morphology, and numerical simulation

Herein, new insights on the breakage mechanism of magnetite quartzite via high voltage pulse discharge were proposed. The liberation of magnetite quartzite was significantly enhanced by high voltage pulse discharge. The ground products liberations of pulse numbers 300 were improved by 20.93% at grinding time 3 min. The iron distribution rate of high voltage pulse breakage in −0.074 mm were improved by 29.04 percentage points at pulse numbers 300. The linear thermal expansion coefficient of magnetite and quartz were 7.52 × 10−6 °C and 5.70 × 10−7 °C, thus different expansion deformation and thermal stress of grain boundary expansion generated to promote the grain boundary separation of quartz and magnetite. The impact wave force destroyed the intergranular force rather than the intragranular force preferentially during the high voltage pulse breakage. A distorted electric field was generated at the mineral interface to produce grain boundary cracks and realized the macro fracture of magnetite quartzite.

Experimental study on crushing of concrete slabs by high-voltage pulse discharge

To investigate the effectiveness of high voltage pulse discharge (HVPD) in crushing concrete slabs, HVPD in-liquid tests were conducted in pre-drilled holes in three double-layer bi-directionally reinforced and twelve single-layer bi-directionally reinforced concrete slabs. The parameters that were varied in the tests included the concrete strength, discharge hole diameter and spacing, discharge voltage and number of copper wires discharged. The results showed that the explosion caused by HVPD using copper wires increased the crack width by more than 34.8% compared to that caused by the electrohydraulic effect. After 10 explosions caused by HVPD using copper wires, the single-layer reinforced concrete slab was split into several slabs by cracks to achieve the crushing effect. The single discharge energy, i.e., discharge voltage, had a significant effect on the crushing of concrete slabs, and the width of concrete cracks produced by a 100 kV discharge was more than twice that of a 40 kV discharge. The increase in concrete strength acted as a crack arrestor for the slabs, and the crack width of C20 concrete slabs increased by approximately 10% to 25% compared to C40 concrete slabs. The increase in crack width with increasing number of discharged copper wires decreased with increasing discharge voltage. The width of concrete cracks produced by the explosion of 60 copper wires compared to 30 copper wires increased by approximately 10% at 100 kV and by approximately 20% from 60 to 80 kV. The crack width of concrete slabs with discharge holes of diameter 40 mm increased by approximately 5% to 15% compared to concrete slabs with holes of 50 mm. Expressions for the relationships between the damage degree of the concrete slab (i.e., the width of the concrete cracks around the holes on the outside of the slab) and the key parameters such as the output voltage, the number of discharged copper wires, and the strength grade of the concrete were established based on the experimental results.

Comparative study on the degradation of phenol by a high-voltage pulsed discharge above a liquid surface and under a liquid surface

The degradation of phenol by pulsed discharge plasma above a liquid surface (APDP) and under a liquid surface (UPDP) was compared. The effects of discharge voltage, discharge distance, initial solution conductivity and initial pH on the removal of phenol were studied. It was concluded that the removal of phenol increases with increasing discharge voltage and with decreasing discharge distance in both APDP and UPDP systems. An increase in the initial solution’s conductivity has a positive effect in the APDP system but a negative effect in the UPDP system. In addition, alkaline conditions are conducive to the degradation of phenol in the APDP system, while acidic conditions are conducive in the UPDP system. Free radical quenching experiments revealed that ·O− 2 has an important influence on the degradation of phenol in the APDP system, while ·OH plays a key role in the UPDP system. This paper verifies the differences in the two discharge methods in terms of phenol removal.

Evaluation of spatial distribution of the oxidation of glass beads simulating soil using high-voltage pulsed discharge

The spatial distribution of soil oxidation using a high-voltage pulse generator was evaluated using indigo carmine. The results showed that the amount of indigo carmine decolorization increased with increasing charging voltage and energy input. It was also found that the decolorization of indigo carmine occurred on the surface of the needle electrode, in the discharge path, and near the ground electrode. The probability of discharge penetrating soil increased with decreasing the gap length between the electrode tip and soil surface, which promoted the decolorization reactions. The amount of indigo carmine decolorization per volume decreased with increasing soil depth. When the soil depth was large, discharges reaching the ground electrode could not be confirmed. This suggests that the oxidation reaction of indigo carmine depends on a discharge that penetrates the soil.

Numerical simulation of the breakdown process of dielectric in high voltage pulse discharge

In order to study the breakdown process of the insulating medium of the needle-needle electrode under the action of high-voltage pulse discharge, the HV-LAB simulation software was used to study the discharge channel formed in the three kinds of insulating media, namely water, transformer oil, and air, and the three-dimensional model of the discharge breakdown insulating medium was designed. The process of discharge channel expansion, voltage, current, power, and energy loss in the discharge channel is analyzed. The results show that in the process of high-voltage pulse discharge breakdown of the insulating medium, the formation time of the discharge channel of transformer oil is long, the energy is accumulated, the number of discharge channels is less, the horizontal isopotential lines are dense, and the energy is concentrated. Under the same discharge conditions, the energy consumption of transformer oil in the process of high-voltage pulse discharge is the least. The results of this study can provide a reference for the selection of high-voltage crushing insulation medium.

Numerical Simulation of Electrode Structure on High Voltage Pulse Discharge Characteristics

For the study of the different electrode structures of the high voltage pulse discharge breakdown process of the insulating medium, the numerical simulation software is compiled to establish two kinds of the electrode structure of high voltage pulse discharge three-dimensional model, finite element difference method to simulate the expansion of plasma channel, the discharge characteristics of electrode structure internal voltage, and current of plasma channel and the impact of energy consumption. The simulation results show that, compared with the needle-needle electrode structure, the needle-plate electrode structure has a shorter time to reach the critical field strength of distilled water smaller breakdown voltage, shorter time to establish the discharge channel, smaller equivalent resistance, faster extension speed of the discharge channel, and less energy consumption for breakdown. And other conditions are the same. The results of this study can provide a theoretical reference for the structural design of high-voltage pulse-crushing electrodes.

Uniform Action of Plasma of a Nanosecond Pulsed High-Voltage Discharge on the Surface of a Flat Anode

The results of an experimental study of the effect of a plasma of a nanosecond pulsed high-voltage discharge in air at atmospheric pressure, excited in a sharply nonuniform electric field, on the surface of a flat-grounded electrode are presented. It is shown that at relatively large interelectrode distances between the pointed cathode and the flat anode, a diffuse discharge is implemented, which ensures a uniform action of the discharge plasma on the anode surface.

Stress wave analysis of high-voltage pulse discharge rock fragmentation based on plasma channel impedance model

High-voltage pulse discharge (HVPD) rock fragmentation controls a plasma channel forming inside the rock by adjusting the electrical parameters, electrode type, etc. In this work, an HVPD rock fragmentation test platform was built and the test waveforms were measured. Considering the effects of temperature, channel expansion and electromagnetic radiation, the impedance model of the plasma channel in the rock was established. The parameters and initial values of the model were determined by an iterative computational process. The model calculation results can reasonably characterize the development of the plasma channel in the rock and estimate the shock wave characteristics. Based on the plasma channel impedance model, the temporal and spatial distribution characteristics of the radial stress and tangential stress in the rock were calculated, and the rock fragmentation effect of the HVPD was analyzed.

Effects of Static Pressure on Failure Modes and Degree of Fracturing of Sandstone Subjected to Inter-Hole Pulsed High-Voltage Discharge

This research aims to explore the fracturing behaviors of sandstone subjected to pulsed high-voltage discharge (PHVD) under different static pressures. An experimental method of rock fracturing induced by inter-hole PHVD was proposed. The static pressure was applied to the specimens, then the proposed method was applied to induce electrical breakdown testing under static loading. The microscopic fracture morphology of the sandstone was observed. The influences of the direction and level of static pressure on the crack length and fractal dimension of sandstone under the effect of PHVD were discussed. The results indicated that in the absence of static pressure, there are a discharge channel and multiple radial cracks in the sandstone after electric breakdown. The microscopic analysis implies that rock failure in the zone around the discharge channel is mainly influenced by the high temperature; while radial cracks are induced by shock waves. When static pressure is vertical to the discharge channel, tensile and compressive stresses concentrate in different parts around the discharge channel, which can remarkably alter the distribution zone and propagation path of cracks. In addition, the fractal dimension and total length of cracks first decrease, then increase with increasing static pressure. When static pressure is parallel to the discharge channel, the distribution characteristics and propagation direction of cracks are unchanged; however, under this loading mode, circularly distributed hoop tensile strains are generated at the zone around the discharge channel, which enables the fractal dimension and crack length increase with increasing static pressure.