This study investigates how the operating position affects the voltage, temperature, and gas convection of a xenon short arc lamp using a 3D simulation. Under constant DC current, the voltage between the anode and cathode was higher in the vertical position. As a result, the lamp’s input power and radiative energy increased. In the horizontal position, the arc expanded due to buoyancy exceeding the Lorentz force, increasing the conductance and decreasing the voltage. Buoyancy drove hot gas upward, making the upper region hotter in the horizontal mode and the lower region hotter in the vertical one. However, the average gas temperature and operating pressure were nearly identical in both positions. The gas convection was axially symmetric in the vertical position, circulating throughout the gas region, while it mainly circulated in the upper region on the cathode side in the horizontal position. The electrodes also showed directional dependence. Specifically, the cathode was hotter in the horizontal position, and the anode was hotter in the vertical one. The bulb temperature correlated with the gas temperature, but the average bulb temperature was nearly the same in both positions. These results demonstrate that the operating direction significantly affects the lamp characteristics, including light output.

This study presents three-dimensional unsteady computational fluid dynamics simulations, under the assumption of local thermodynamic equilibrium, conducted in OpenFOAM to examine how varying the outlet diameter and throat length of a plasma spray torch affects its internal arc behavior and exit jet characteristics. Voltage and attachment-point temperature diagnostics show a restrike cycle driven by an imbalance between Lorentz and drag forces. These attachment dynamics are consistent across downstream geometries. Outlet observations reveal that Lorentz-driven off-axis motion produces crescent-shaped temperature and velocity fluctuations. When time-averaged, these yield a flat-topped parabolic radial temperature profile with a 15 kK centerline peak and an M-shaped mean velocity with a central dip. The hot-core thickness is geometry-insensitive because the sharp drop in thermal conductivity imposes the conductive bottleneck while elevated kinematic viscosity suppresses shear-layer mixing. In contrast, the velocity responds predictably to geometry: Larger outlets reduce overall jet speed and flatten the core, whereas longer throats increase centerline velocity nearly linearly by extending the acceleration region. These results supply compact, physics-based heat-source and inflow boundary conditions for thermal spray simulations.

Most plasma-based waste-treatment gasification systems employ arc plasma torches, in which the arc is usually stabilized either by a water vortex or by a swirling gas flow. Hybrid water–gas torches integrate both stabilization mechanisms. In current practice, argon is frequently selected as the stabilizing medium due to its strong arc-stabilizing capability; however, its presence in the produced synthesis gas is undesirable. This drawback motivates the search for alternative stabilizing gas compositions. Hydrogen has been proposed as a potential substitute for argon and may offer improved plasma-processing performance. In this study, we present thermophysical property calculations for argon–steam and hydrogen–steam plasmas, including enthalpy, electrical conductivity, thermal conductivity, and net emission coefficients. In addition, we introduce parameters derived from a simplified integral model of the arc column to characterize the influence of the stabilizing gas on arc-column behavior. The parameters were benchmarked against a more detailed one-dimensional numerical model of the central part of the plasma discharge. The results indicate that hydrogen increases the thermal conductivity and enthalpy of the plasma compared to argon, while the electrical conductivity is slightly larger for argon at relevant temperatures. The examined parameters suggest that hydrogen stabilization leads to higher arc voltages, although with increased heat losses to the torch walls. Relative to argon–steam, hydrogen–steam plasmas are expected to exhibit lower bulk temperatures while transporting higher enthalpy, which may translate into improved overall efficiency and supports the feasibility of hydrogen as an effective stabilizing gas for hybrid torches.

This study investigated the effects of pulsed current under different CO2 contents in mixture Ar-CO2 shielding gas on Metal Transfer Frequency (MTF) in Metal-Cored Arc Welding (MCAW) and compared it with Gas Metal Arc Welding (GMAW) using a solid wire. Experiments were conducted for an average current of 250 A with 5–50 + 20

Thermophysical properties of thermal plasmas are essential input data for computational models. The required data are usually taken from the literature without examination of their reliability. Cross-code verifications of properties are rare in the thermal plasma literature, partly due to the complexity of the calculation methods, which require a systematic treatment of large datasets, multiple computations and the adoption of different models. Here, a detailed comparison of two computational codes that use different workflows but very similar underlying methods is presented, using the example of thermophysical properties of argon, krypton, and xenon plasmas in local thermodynamic equilibrium at pressures from 1 to 100 atm. The comparison considers plasma composition, collision integrals, thermodynamic properties and, in particular, transport coefficients. The comparison allowed inconsistencies and errors to be identified and corrected, resulting in improved thermophysical properties of argon, krypton, and xenon. Furthermore, transport coefficients obtained from state-of-the-art intermolecular potentials were compared with those obtained from the simpler phenomenological potential, demonstrating good agreement, including at high pressures.

This study investigates the role of the flux column in the metal transfer process of Flux-Cored Arc Welding (FCAW). Three rutile-type wires with varying flux ratios were compared with metal-cored and solid wires under Ar-CO2 shielding at 220—280 A. Transfer frequencies increased with current for all wires. At 280 A, FCAW and Metal‑Cored Arc Welding (MCAW) showed higher frequencies (142.9 and 240.5 Hz) than Gas Metal Arc Welding (GMAW) (69.8 Hz). At 220 A, FCAW and MCAW showed similar frequencies (82.1 and 71.8 Hz) attributed to long flux or metal columns (un-melted metal core), which prevented neck formation by the Lorentz force. In the 250—280 A range, the MCAW frequency increased significantly, reaching 168

This study clarified the effects of flux composition on metal transfer characteristics in rutile-type Flux-Cored Arc Welding (FCAW). Seven prototype wires with varying TiO2, SiO2, and CaF2 contents in the flux were tested at three currents (220–280 A) under Ar-20

Radio-frequency (RF) inductively coupled plasma (ICP) thrusters are an emerging electric propulsion technology that electrodelessly heat propellant gas to high temperatures via plasma-gas collisional processes. Thrust is then produced by accelerating this hot gas through a converging-diverging nozzle. Propellant selection is an important factor that affects not only the thruster operation and performance but also the design and complexity of the overall propulsion system. In this work, we study several propellant options for RF ICP thrusters, considering propulsive performance, mission suitability, and storage requirements. The analysis accounts for important high-temperature considerations such as propellant dissociation at the elevated temperatures encountered inside the thruster and frozen flow losses in the nozzle. While low atomic/molecular mass propellants such as hydrogen exhibit the highest conventional specific impulse, their low storage density results in a poor total impulse mass density (impulse per propulsion system wet mass). By contrast, liquid propellants such as water and ammonia are found to be attractive alternatives because of their higher storage density and relatively low molecular mass, which is further reduced due to thermal dissociation.

Nonthermal plasma (NTP) offers a promising electrified route for CO2 methanation by enabling molecular activation under mild conditions; however, the role of catalyst supports in governing plasma–catalyst interactions and reaction pathways remains insufficiently understood. In this work, we systematically investigate Ni catalysts supported on Al2O3, ZrO2, BaTiO3, commercial CeO2, and high surfacearea CeO2 (HC300) to elucidate how support properties influence plasmaassisted CO2 methanation. Plasma catalytic testing revealed that while support materials alone have limited impact on overall CO2 conversion, the incorporation of Ni significantly enhances activity and CH4 selectivity, with performance strongly correlated to activemetal dispersion and surface basicity. Ni/HC300 exhibited the highest dispersion (58%), strongest weakbasicity population, and superior performance (82% CO2 conversion, 100% CH4 selectivity). Insitu comparative diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) provided mechanistic insights, showing that surface reactions dominate the conversion under NTP conditions, and both formate and CO pathways occur over the catalysts under investigation. The dominant ratedetermining steps involve hydrogenation of formate (HCOO*) or formyl (HCO*) species, or methoxy (CH3O*) dissociation depending on the nature of the support. Overall, this work establishes clear structure–property–function relationships, offering mechanistic guidance for rational catalyst design in plasmaassisted CO2 hydrogenation.

This study presents a comprehensive numerical investigation into the short-circuit transfer behavior in aluminum alloy metal inert gas (MIG) welding, focusing on the coupled interactions among arc plasma dynamics, droplet transfer, and molten pool flow. A multi-physics model was developed to simulate the transient dynamics of droplet transfer, incorporating wire melting kinetics and continuous feeding mechanisms. The model integrates arc-droplet-pool interactions and metal vapor transport phenomena, providing a detailed analysis of the short-circuit transfer process. It reveals significant dynamic changes in arc temperature and current density fields during the short-circuit transfer, which influence the wire heating and melting. The flow fields of the droplet and molten pool are influenced by electromagnetic forces, surface tension, and gravity, leading to complex flow patterns and pressure variations within the droplet. Experimental validation using high-speed video imaging confirmed the accuracy of the simulated droplet shapes and transfer behavior. This research lays a foundational theoretical framework for further numerical simulations of short-circuit transfer in aluminum alloy MIG welding, offering insights into optimizing welding stability and quality.

The collection of contributions from the Leibniz Institute for Plasma Science and Technology presents findings from experimental and modelling studies of the physical and chemical processes in non-thermal and thermal plasmas produced by various kinds of plasma sources. The characterisation and properties of micro-scale discharges and suitable gases for switching technologies are explored in view of their applications. Contributions to plasma medicine as an innovative research field focus on cold atmospheric-pressure plasma sources for specific biomedical applications. The development and optimisation of plasma-based processes is considered in works focused on bioeconomy and waste treatment. Finally, a modern concept of research data management for low-temperature plasmas demonstrates the digital workflows being developed to link metadata standards, laboratory notebooks and data repositories.

The increasing levels of CO2 in the atmosphere are significantly worsening the greenhouse effect, triggering a series of serious environmental problems. There is an urgency to develop and deploy decarbonization pathways to alleviate the situation. Electricity-driven plasma technology operates under mild conditions with high energy efficiency and can be coupled with renewable energy to realize the conversion of CO2 to fuels and chemicals, offering an alternative solution to transform and store the renewable energy into energy carriers. This perspective describes the challenges and prospects of plasma-enabled CO2 conversion processes in three conversion pathways (splitting, reforming and hydrogenation) and their techno-economic analysis. We highlight the key elements of integrating renewable electricity with the power source to generate and sustain plasma to reduce carbon emission. Unlocking the three conversion pathways has a substantial potential for rapid and deep decarbonization of the chemical industry, accelerating the transition to a low-carbon economy and facilitating improvements in environmental sustainability.

This study investigates the effects of alkali elements on metal transfer behavior in rutile flux-cored arc welding. Four types of prototype flux-cored wires with different sodium contents in the flux were fabricated. By using these wires, the influence mechanism of sodium on the metal transfer behavior was elucidated through shadowgraph measurements of the metal transfer behavior as well as spectroscopic and color image observations of the arc characteristics. It was found that the metal transfer between 190 A and 310 A was in the projected transfer mode and could be further classified into two sub-modes (type A and type B) based on the droplet formation process. A larger droplet was formed on the side of flux column in type A, while a smaller one was formed in the center covering the flux in type B. The metal transfer frequency became larger in the latter case for the same wire feeding speed. Type A tended to dominate in the lower current and lower sodium content conditions, while type B dominated in the opposite conditions. The dominant sub-mode was determined to depend on the Lorentz force acting on the droplet. At medium currents (250 A and 280 A), both sub-modes appeared in similar proportions. The maximum metal transfer frequency occurred at a particular sodium content. When the sodium content was smaller or larger, type A or type B became dominant, respectively. The sodium content at which the maximum frequency occurred decreased when the current increased. In type A, the iron plasma was widely distributed on the droplet side of the flux, while the sodium plasma was concentrated near the flux on the opposite side, so both were separated. In contrast, in type B, the sodium plasma was concentrated around the flux at the center and the iron plasma was widely distributed in the arc column, so both overlapped around the center. Sodium has a low boiling point and low ionization potential. In type A, the sodium vapor greatly increased the electrical conductivity of plasma around the flux column, so part of the current flowed from the wire through the sodium plasma to the weld pool. Accordingly, the current flowing through the bottom of the droplet to the arc decreased, leading to a lower arc pressure and recoil pressure under the droplet, and causing the metal transfer frequency to increase with sodium content. On the other hand, in type B, the sodium vaporization increased around the center, increasing the recoil pressure. In addition, the current density at the bottom of the droplet increased due to the current concentration in the arc, causing the arc pressure to rise. Therefore, the metal transfer frequency tended to decrease with sodium content. Due to the balance of these factors, the metal transfer frequency has a maximum at a particular sodium content.

This study aimed to clarify the influence of a longitudinal external magnetic field (EMF) on arc characteristics, metal transfer behavior, and weld bead formation in metal-cored arc welding (MCAW) process. The work focused on comparing two distinct conditions: without EMF (0 mT) and with EMF applied at a magnetic flux density (MFD) of 6 mT, evaluated by high-speed video observations and numerical simulation models for a welding current of 320 A. Experimental results indicated negligible changes in droplet transfer frequency between the two conditions, but significant differences were observed in arc behavior and weld pool characteristics. The application of EMF intensified arc brightness and increased weld penetration depth from 3.7 mm (no EMF) to 4.2 mm (EMF 6 mT). Simulation results revealed that EMF induced rotational plasma flow and reduced pressure at the arc column center, which resulted in an increased plasma velocity directed toward the weld pool surface. Consequently, a depression was observed at the weld pool surface to enhance the weld bead penetration. The findings highlight the potential of EMF as a valuable tool to optimize MCAW processes, particularly when precise penetration control and improvement of weld quality are required.

Given its significant environmental and economic impact, substantial research has been dedicated to improving the Haber–Bosch process. Leveraging the advantages of renewable energy sources and sustainable feedstocks, plasma catalysis is emerging as a promising green technology for small-scale, onsite nitrogen (N₂) fixation. However, current plasma-catalysis applications for nitrogen fixation face several challenges. These include high energy consumption for hydrogen (H2) production prior to ammonia synthesis, low energy efficiency, and a limited understanding of the underlying mechanisms. In this study, we compare two green chemical pathways for plasma catalysis in NH3 and NOx production and their effective storage in water from a plasma chemistry modeling perspective. Our model incorporates both electron and vibrational kinetics, along with updated surface reactions based on Density Functional Theory (DFT) calculations. These calculations consider catalytic ruthenium (Ru) on MgO supports and non-catalytic SiO2 as a reference for ammonia synthesis and titanium dioxide (TiO2) for NOx synthesis. We will evaluate and discuss key intermediates and pathways for producing high-density NH3 and NOx, and suggest opportunities for further improvement.

Converting carbon dioxide into useful products offers a pathway to reduce CO2 emissions and an opportunity to transform renewable energy into energy carriers and/or high-value products. Unlike traditional thermal chemical technologies, non-thermal plasma CO2 conversion processes are well suited to coupling to renewable energy sources. However, the technology readiness level of such plasma processes is low, and a significant gap between existing fundamental research and industrial application remains. After briefly summarising the available non-thermal plasma technologies for CO2 conversion, criteria for successful industrialisation are considered, and recent progress towards considering and meeting the technical and economic requirements is analysed. The needs identified include using consistent energy efficiency calculations that consider losses in the power supply and elsewhere, improved reactor design for plasma catalytic processes, detailed techno-economic analyses, and studies of the integration of individual plasma reactors into a modularised system and a complete chemical process.

Abstract Wire arc additive manufacturing (WAAM) is a metal additive manufacturing (AM) process attracting interest from the automotive, defence, aerospace, architecture/engineering/construction and other industries because of its ability to manufacture large metal parts cost-effectively. Nevertheless, problems such as part defects and process efficiency remain, and consequently, efforts to improve WAAM are continuing. The WAAM process involves physical phenomena that include fluid flow, heat transfer, phase changes including melting, solidification and vaporization, multi-phase interactions, and deformations resulting from residual stresses—so obtaining a complete understanding is challenging. While numerical modelling is widely used to understand and assist with developing processes, modelling of AM processes such as WAAM is sophisticated because of their multi-physics and multiscale nature. This review addresses the existing and likely future roles of numerical modelling in advancing WAAM technology. Consideration is given to the known problems with WAAM, the different types of numerical modelling, including computational fluid dynamics, the finite element method, and smoothed particle hydrodynamics, and their potential to address persistent issues. Additionally, this review seeks to provide an understanding of the physics associated with the WAAM process, examines the trends in the development of WAAM technology, and recommends possible future directions. These include the combination of different physics-based modelling approaches to overcome their individual shortcomings, and the inclusion of modelling as part of a digital twin of the WAAM process.

Excessive spatter formation in conventional CO2 arc welding significantly diminishes welding quality and efficiency, posing a critical challenge for industrial applications. To address this issue, this study investigated the mechanisms of metal transfer behavior and spatter formation under the influence of a longitudinal magnetic field (LMF) using a shadow-graph technique with high-speed imaging and back-laser illumination, also coupled with Computational Fluid Dynamics (CFD)-based arc-droplet numerical simulations. The results show that increasing the magnetic flux density (MFD) from 0 to 2 mT shifted the transfer mode from the repelled transfer to the globular transfer, while higher MFDs (3–4 mT) induced rotating repelled transfer. The globular transfer at 2 mT was considered to be primarily produced by the centrifugal effect due to the rotational motion of the molten metal inside the droplet, which was caused by the Lorentz force affected by LMF. The higher droplet temperature in this condition also contributed to forming this transfer mode, preventing the formation of repelled transfer through a decrease in the arc pressure. On the contrary, in the higher MFDs, the droplet temperature decreased to increase the arc pressure, lifting the droplet up. Furthermore, the very strong centrifugal effect rotated the molten metal column around the wire axis to induce the rotating repelled transfer. The spatter formation was found to occur with the two-stage motion of the curved long tail without LMF and at 4 mT, and also with the exploding molten metal column at 4 mT, due to an imbalance of the Lorentz force acting on the molten metal. On the other hand, the neck formation facilitated smooth droplet detachment without forming the curved long tail at 2 mT, reducing spatter significantly. These findings offer valuable insights for optimizing welding quality and efficiency by stabilizing globular transfer under an optimal LMF.

Given the significant greenhouse effect of SF6, the C4F7N-CO2-O-2 mixture has been identified as one of the most promising eco-friendly arc-extinguishing gases. Switching arcs typically exhibit pronounced non-local thermodynamic equilibrium (NLTE) phenomena in the peripheral regions and at the current zero-crossing point, thereby influencing the thermophysical properties of the plasma. To investigate the impact of NLTE conditions, the thermodynamic properties and transport coefficients of two-temperature (2-T) C4F7N-CO2-O-2 plasma were calculated under the local chemical equilibrium assumption. The results indicate that NLTE conditions significantly affect the properties of the mixture by altering its composition and particle energy, often having a more substantial impact than pressure variations. The generation of CO plays a critical role in shaping the thermodynamic and transport parameters of the plasma due to its molecular stability, particularly under non-equilibrium states. To maximise the arc-extinguishing performance of the gas, recommended oxygen mixing ratios are proposed. The results provide fundamental data for 2-T magnetohydrodynamic modelling of C4F7N gas mixtures in arc simulations.