Search Results (14)

The dry conversion of CO₂ into CO and O₂ provides an attractive path for CO₂ utilization which allows for the use of the CO produced for the synthesis of valuable hydrocarbons. In the following work, the CO₂ conversion is driven by an arc discharge at atmospheric pressure, producing hot plasma. This study presents a series of experiments aiming to optimize the process. The results obtained include the energy efficiency and the conversion rate of the process, as well as the electrical parameters of the discharge (current and voltage signals). In addition, optical emission spectroscopy diagnostics based on an analysis of C₂’s Swan bands are used to determine the gas temperature in the discharge. The data is analyzed according to several aspects—an analysis of the arc’s motion based on the electrical signals; an analysis of the effect of the gas flow and the discharge current on the discharge performance for CO₂ conversion; and an analysis of the vibrational and rotational temperatures of the arc channel. The results show significant improvements over previous studies. Relatively high gas conversion and energy efficiency are achieved due to the arc acceleration caused by the Lorentz force. The rotational (gas) temperatures are in the order of 5500–6000 K. Full article

Powder metallurgy (PM) offers several advantages over conventional melt metallurgy, including improved homogeneity, fine grain size, and pseudo-alloying capabilities. Transitioning from conventional methods to PM can result in significant enhancements in material properties and production efficiency by eliminating unnecessary process steps. Dynamic compaction techniques, such as impulse and explosive compaction, aim to achieve higher powder density without requiring sintering, further improving PM efficiency. Among these techniques, magnetic pulse compaction (MPC) has gained notable interest due to its unique process mechanics and distinct advantages. MPC utilizes the rapid discharge of energy stored in capacitors to generate a pulsed electromagnetic field, which accelerates a tool to compress the powder. This high-speed process is particularly well-suited for compacting complex geometries and finds extensive application in industries such as powder metallurgy, welding, die forging, and advanced material manufacturing. This paper provides an overview of recent advancements and applications of MPC technology, highlighting its capabilities and potential for broader integration into modern manufacturing processes. Full article

This work investigates CO₂ conversion using atmospheric pressure low-current gliding discharges (GD). The following three modifications are studied: classic GD; magnetically accelerated GD (MAGD); and magnetically retarded GD (MRGD). In the latter two, permanent magnets produce a magnetic field that either accelerates or retards the discharge downstream. The gas flow is confined between quartz plates and the electrodes, with varying channel thicknesses. The magnetic configurations improve the performance compared to the classic GD, with up to 30% higher energy efficiency and up to a 50% higher conversion rate. The highest conversion rate is 11–12% with 10% energy efficiency, while the highest efficiency is 40% with 5% conversion, achieved with MRGD and MAGD at channel thicknesses of 2 mm and 3 mm. Full article

A disruptive Electric Propulsion system is proposed for next-generation Low-Earth-Orbit (LEO) small satellite constellations, utilizing an RF-powered Helicon Plasma Thruster (HPT). This system is built around a Magnetically Enhanced Inductively Coupled Plasma (MEICP) reactor, which enables acceleration of quasi-neutral plasma through a magnetic nozzle. The MEICP reactor features an innovative design with a multi-dipole magnetic confinement system, generated by neodymium iron boron (NdFeB) permanent magnets, combined with an azimuthally asymmetric half-wavelength right (HWRH) antenna and a variable-section ionization chamber. The plasma reactor is followed by a solenoid-free magnetic nozzle (MN), which facilitates the formation of an ambipolar potential drop, enabling the conversion of electron thermal energy into ion beam energy. This study explores the impact of an inhomogeneous magnetic field on the heating mechanism of the HPT and highlights its multi-mode operation within a pulsed power range of 200 to 500 W of RF. The discharge state, characterized by high-energy electron-excited ions and low-energy excited neutral particles in the plasma plume, was analyzed using optical emission spectroscopy (OES). The experimental testing campaign, conducted under pulsed power excitation, reveals that, as RF input power increases, the MEICP reactor transitions from inductive (H-mode) to wave coupling (W-mode) discharge modes. Spectrograms, electron temperature, and plasma density measurements were obtained for the Helicon Plasma Thruster within its operational envelope. Based on OES data, the ideal specific impulse was estimated to exceed 1000 s, highlighting the significant potential of this technology for future LEO/VLEO space missions. Full article

Magnetic pulse welding (MPW) employs a strong pulsed magnetic field to accelerate parts against each other, thus forming an impact joint. Single-turn tool coils and field-shapers (FSs) used in MPW operate under the most demanding conditions, such as magnetic fields of 40–50 T with periods lasting tens of microseconds. With the use of conventional copper and bronze coils, intense thermo-mechanical stresses lead to the rapid degradation of the working bore. This work aimed to improve the efficiency of field-shapers and focused on the development of two- and four-slit FSs with a nanocomposite Cu 18Nb brazed wire acting as an inner current-carrying layer. The measured ratios of the magnetic field to the discharge current were 56.3 and 50.6 T/MA for the two- and four-slit FSs, respectively. FEM calculations of the magnetic field generated showed variations of 6–9% and 3% for the two- and four-slit FSs, respectively. The ovality percentages following copper tube compression were 27% and 7% for the two- and four-slit FSs, respectively. The measured deviations in the weld-joining length were 11% and 1.4% in the two- and four-slit FSs, respectively. Compared to the previous experiments on an entirely steel inductor, the novel FS showed significantly better results in terms of its efficiency and the homogeneity of its magnetic field. Full article

Impurity elimination in tundishes is an essential metallurgical function in continuous casting. If inclusions in a tundish cannot be effectively removed, their presence will have a serious impact on the quality of the bloom. As a result, this research investigates the locations of inclusion particles in a six-strand induction-heating tundish in depth, combining the flow, temperature, and inclusion trajectories of molten steel under electromagnetic fields. The results show that a pinch effect occurred in the induction-heating tundish, and a rotating magnetic field formed in the channel, with a maximum value of 0.158 T. The electromagnetic force was directed toward the center of the axis, and its numerical distribution corresponds to the magnetic flux density distribution, with a maximum value of 2.11 × 10⁵ N/m³. The inclusion particles’ movement speed accelerated as the molten steel’s temperature rose, and their distribution in the channel was identical to the rotating flow field distribution. When the steel’s temperature rose from 1750 K to 1850 K, the removal percentage of inclusion particles in the discharge chamber rose by 9.20%, the removal rate at the outlet decreased from 8.00% to 3.00%, and the adhesion percentage of inclusion particles in the channel decreased from 48.40% to 44.40%. Full article

In the 21st century, researchers have been exploring different designs, performance characteristics, charging–discharging regions, and regenerative braking aspects of electric vehicles. However, there has been a major gap in the multimodal analysis of the accelerating pedal drive for electric vehicles; therefore, herein, a novel analytical model of a mimicked foot pedaling control of an electric vehicle is developed by cascading five sub-models (i.e., foot pedal, resistive potentiometer, 555 timer, buck converter, and the permanent magnet DC motor) to synthesize the overall third-order transfer function of the system. MATLAB is utilized to comprehensively analyze the transient and steady-state characteristics of the developed model by considering the pedaling force, four different materials (i.e., aluminum, brass, carbon fiber, and polyamide 6), the potentiometer’s resistance, and the mechanical and electrical attributes of the motor. The results highlight that the linear pedaling drive is possible by considering the polyamide 6 material’s pedaling properties of 0.25 kg mass and 2.679 Ns/m damping coefficient. Furthermore, at a lesser potentiometer track length (around 10 cm) and equivalent inertia of 5 Kgm², the motor generates the regulated angular velocity, thereby minimizing the transient characteristics of the accelerating pedal. Full article

Waste oil scum is commonly discharged during the air flotation process at oil-bearing wastewater treatment plants and disposed as an additive in cement kilns and/or furnaces. Herein, it was mixed with a magnetite-rich waste sludge and then completely recycled as value-added gas/oil and magnetic char via a facile catalytic pyrolysis route. Results showed that the oil scum was a blackish gel and contained 36.2% water, 52.5% tar, and 11.3% inorganics. After direct pyrolysis, the conversion efficiencies of tar to gas, oil, and char were 30.2%, 41.2%, and 28.6%, respectively, and the generated gas/oil was rich in aromatics. By adding Fe-rich sludge, the efficiencies varied to 57.3%, 26.9%, and 15.8%, respectively, and the gas/oil mainly comprised a chain hydrocarbon. During oil scum pyrolysis, the redox reaction of tar to Fe-rich sludge enabled a cycle of Fe/magnetite to accelerate the cleavage of tar as volatiles and to steadily retard the polycondensation of tar as char. In addition, the added Fe-rich sludge not only activated the rest of the char and created more surface functional groups for contaminant adsorption but also endowed the char with a good magnetic response. Such magnetic char showed a maximum adsorption capacity of ciprofloxacin of 63.5 mg/g, higher than that without the Fe-sludge catalyst, and had ability to selectively adsorb ciprofloxacin from benzoic/sulfanilamide-bearing wastewater. In summary, a ‘waste to treat waste’ strategy was developed to recycle waste oil scum as combustible gas/oil and magnetic char with the addition of magnetite-rich sludge. Full article

High temperature superconducting (HTS) magnets often work at high energy density and have slow quench propagation speed, so a quench will present a serious risk to the safety of magnets. The quench protection method based on the dump resistance can effectively reduce the current and release the energy in the HTS magnets. However, too large dump resistance may cause excessive voltage across the magnets. A quench protection system consisting of dump resistances and metal discs has been proposed. Copper discs are often embedded in HTS magnets for conducting cooling and mechanical support. In the discharging process of HTS magnets, the copper discs can absorb energy from the magnets through magnetic coupling, thus accelerating the current decay of the magnets. This quench protection method is more effective than using dump resistance alone. In this paper, the effect of different copper discs on the discharging process of HTS coils is discussed. Eight types of copper with different residual resistivity ratios (RRR) are applied. The results show that with the increase of the RRR of the copper disc, the current decay rate of the coil increases, and the energy absorbed by the copper disc from the coil increases. The role of different copper discs in the fast quench protection of the coil can be sorted as: RRR = 300 > RRR = 100 > RRR = 80 > RRR = 60 > RRR = 40 > RRR = 30 > RRR = 20 > RRR = 10. The copper disc with RRR of 300 shows the best performance in quench protection of HTS coils. Full article

A novel design of a neutralizer-free plasma thruster is proposed. This setup features a capacitively coupled RF discharge for plasma generation combined with a magnetic nozzle configuration for acceleration. Characteristics of the plasma plume and ions flux are investigated with the help of emissive probes and retarding potential analyzers (RPA). Essential parameters of the thruster like ions energy, ions flux, utilization efficiencies, and thrust are estimated. The investigated system produces a beam of ions accelerated to an energy of 10 eV when operated at power levels of ~20 W and a mass flow of 1.2 mg/s. The ion energy coincides with the potential drop in the plasma plume indicating that the acceleration takes place due the formation of an ambipolar electric field in the expanding plasma. The design is compared to the data available of other similar thrusters. Full article

The acceleration of inactivating viable cells of Escherichia coli (E. coli), by using new direct and indirect innovative methods, is the targeted method of using an atmospheric pressure plasma jet (APPJ) operated by an AC high-voltage power source with variable frequency up to 60 kHz and voltage ranging from 2.5 to 25 kV. Discharges using dry argon (0% O₂) discharges and different wet argon discharges using admixtures with O₂/Ar ratios ranging from 0.25% to 1.5% were studied. The combined effects of dry and wet argon discharges, direct and indirect exposure using a mesh controller, and hollow magnets were studied to reach a complete bacterial inactivation in short application times. Survival curves showed that the inactivation rate increased as the wettability increased. The application of magnetized non-thermal plasma discharge with a 1.5% wetness ratio causes a fast inactivation rate of microbes on surfaces, and a dramatic decrease of the residual survival of the bacterial ratio due to an increase in the jet width and the enhanced ability of fast transport of the charges to viable cells, especially at the edge of the Petri dish. The membrane damage of E. coli mechanism factors in the activation process by APPJ is discussed. Full article

Vacuum arc thruster performance in a magnetic nozzle configuration is experimentally characterized. Measurements are performed on a miniature coaxial thruster with an anode inner diameter of $1.8$ mm. The magnetic field B is produced by a single air coil, 18 mm in diameter. Direct measurement of thrust, mass consumption and arc current are performed. To obtain statistically viable results $\approx 6000$ arc pulses are analyzed at each operational point. Cathode mass erosion is measured using laser profilometry. To sustain thruster operation over several measurement cycles, an active cathode feeding system is used. For $0<B\le 0.2$ T, performance increase over the non-magnetic case is observed with the best thrust to arc power ratio $T/P\approx 9$ $\mathsf{\mu }$ N/W obtained at $B\approx 0.2$ T. A parametric model is provided that captures the performance enhancement based on beam collimation and acceleration by the magnetic nozzle. For $B>0.2$ T, the arc discharge is shown to be suppressed nullifying any additional gains by the nozzle effect. Full article

To predict the thrust of magnetoplasmadynamic thrusters (MPDTs), a modified electromechanical model was proposed and a comparison with experimental results is presented in this paper. The motion of propellant in the thruster was divided into two portions: the axial motion which was accelerated by the interaction of current and induced self-field, and the swirling motion which was accelerated by the interaction of current and applied magnetic field. The electromechanical model was in good agreement with the experimental data, and the fitting degrees of the model were greater than 0.93. Furthermore, the influence of parameters on the performance of MPDT were investigated by utilizing the electromechanical model. The results indicate that the thrust performance of the thruster improved with the increase of discharge current, anode radius, applied magnetic field strength, and the decrease of mass flow rate. However, the large anode radius and low mass flow rate readily led to the failure of thruster function. Therefore, the model can not only predict the thrust performance of MPDTs, but also guide the design and operation optimization of the thruster. Full article

In order to clarify the discharge principle of the self-field magnetoplasmadynamic thruster (MPDT), a two-dimensional axisymmetric particle-in-cell/Monte Carlo collision (PIC/MCC) model is proposed. The spatial distribution and the collision characteristics of discharge plasma were calculated using this model. In addition, the influence of the operation parameters on the plasma was analyzed including the voltage and mass flow rate. The effectiveness of the model was verified by comparison to the experimentally induced magnetic field. It was found that the electrons were mainly accelerated by the electric field in the cathode sheath and the electric field shielding effect of plasma was obvious in the bulk plasma region. Due to the pinch effect, the charged particles were constrained near the cathode. The results of the present work implied that the PIC/MCC model provides an approach to investigate the plasma distribution and a kinetic description of particles for the discharge of the self-field MPDT. Full article