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Many studies on how the particle shape affects the discharge flow mainly focus on discharge rates and avalanche statistics. In this study, the effect of the particle shape on the packing fractions and velocities of particles in the silo discharge flow was investigated by using discrete element method. The time-averaged packing fraction and velocity profiles through the aperture were systematically measured for superelliptical particles with different blockiness. Increasing the particle blockiness is found to increase resistance to flow and reduces the flow rate. At an identical outlet size, larger particle blockiness leads to lower velocities and packing fractions at the outlet. The packing fraction profiles display evident self-similar features that can be appropriately adjusted by fractional power laws. The velocity profiles for particles with different shapes obey a uniform self-similar law that is in accord with previous experimental results, which is compatible with the free fall arch hypothesis. To further investigate the origin of flow behaviors, the packing fraction and velocity fields in the region above the orifice were computed. Based on these observations, the flow rate of superelliptical particles was calculated and agrees with the simulated data.

This paper presents a chemical kinetic model to investigate the physicochemical process in C5F10O-CO2 mixtures. The model contains 12 ions, including e, C+, O+, C2 +, O2 +, CO+, CO2 +, O−, C−, C2 −, O2 −, O3 − and 38 neutral species, containing C, O, C2, O2, CO, CO2, O3, C5F10O, C4F7Oa, C4F7Ob, C4F7Oc, C4F7Od, C3F5O, C3F4Oa, C3F4Ob, C3F4Oc, C3F4Od, C3F4Oe, C3F3Oa, C3F3Ob, COCF3, C2F2Oa, C2F2Ob, COFC, COF, C3F7a, C3F7b, C3F6a, C3F6b, C2F5, C2F4a, C2F4b, C2F3a, C2F3b, C2F2, CF3, CF2, CF. The total number of 180 reactions are considered. For the reactions whose forward and reverse rate constants can be obtained, the reactions are split into two one-way reactions. In addition, the reactions which produce photons are also considered as one-way reactions. The other reactions are reversable. The reverse rate constants can be obtained by the ratio of the forward rate constants and the equilibrium constants. The molar fractions of the decomposition products in C5F10O-CO2 mixtures with the C5F10O content to be 5%, 7% and 13% are calculated in the temperature range of 500–3500 K. The ratio of the electron temperature to the temperature of the heavy species is calculated to obtain the deviation from local thermodynamic equilibrium in different temperatures. The characteristic decomposition products in different temperature ranges are determined. In addition, the main reaction pathways for the main species are determined by analyzing the contributions of the corresponding reactions to the generation and consumption of the species. In order to validate the chemical kinetic model, the molar fractions of the species in pure CO2 are compared with those by Gibbs free energy minimization in a wide temperature range. This model can help better understand the physicochemical process from the aspect of the reactions during the over-heat fault, and the characteristic decomposition products in different temperature range can help identify the potential fault to avoid great power accidents.

This paper presents the results of numerical investigation of the current pulses characteristics in SF6/CF4 mixtures for the negative point-plane corona discharge. The pressure and the temperature of gas mixtures are 0.4 MPa and 300 K, respectively. The CF4 content varies from 20% to 80%. The 2D axisymmetric geometry with point-plane electrodes is investigated, and the three drift-diffusion equations are solved to predict the characteristics of the negative corona discharge. In addition, Poisson’s equation is coupled with the above three continuity equations to calculate the electric field. In order to calculate the electron impact coefficients, including the Townsend ionization and attachment coefficients, as well as the mobilities and diffusion coefficients for electrons, the two-term Boltzmann equation is solved. The characteristics of three ionic species at five stages of the first current pulse in 60%SF6-40%CF4 and 20%SF6-80%CF4 mixtures are selected to discuss the development mechanism of current pulses. Moreover, the reduced electric field strengths at the corresponding time instants are presented to help understand the discharge process. The current waveform and the total number of three species are compared in all the cases to analyze the effects of the CF4 content on the discharge. The reduced electric field strength is also helpful in understanding the effects of CF4 content. When the CF4 content increases to 80%, the discharge is more intensive and the pulse frequency also increases.

With the construction of the energy internet, the demand for various sensing devices is increasing. Most of sensing devices need power source which limits their application in the wide spread distributed nodes of sensor network. Therefore, there is an urgent need to develop passive sensing devices which is more intelligent and convenient. This paper studies the magnetoelectric effect of layered magnetoelectric composites. Firstly, the physical process is analyzed by using the finite element method. Secondly, magnetoelectric response of the eddy current in the Cu-PZT layered composite material is investigated. Finally, the voltage variations of circular and rectangular samples are compared. It can be seen from the results that under the action of the eddy current, there is a u-shaped curve relationship between the induced voltage and the magnetic field. The energy conversion of metal-piezoelectric composite material without power source provides an effective path for developing passive magnetic sensor.

Surface charge accumulation and transport on cellular polypropylene play an important role in nanogenerators, which could have a potential impact on energy harvesting and wearable devices for zero carbon energy systems and the internet of things. Different shapes have different charge accumulation and decay characteristics of the polymer. Therefore, we studied the influence of the sample’s shape on the surface charge decay by experiment and modeling. The surface potential of square and circular cellular polypropylene was measured by a two-dimensional surface potential measurement system with electrostatic capacitive probe. The experimental result shows that the surface potential distribution of the square sample dissipates non-uniformly from the bell shape to a one-sided collapsed shape, while that of the circular sample dissipates uniformly from the bell shape to the crater-like shape. Moreover, the simulated results of the initial surface potential distributions of the square and circular cellular polypropylene are consistent with the experimental results. The investigation demonstrates that the charge transport process is correlated with the shape of the sample, which provides significant reference for designing electret material used for highly efficient nanogenerators.

Corona (partial) discharges are generated in electrical equipment before faults occur due to insulation defects. The SF6-decomposition byproducts induced by the partial discharge are closely related to the insulation state of electrical equipment, so understanding the decomposition mechanisms of the byproducts is very important. In order to analyze the chemical processes and the generation mechanisms of the products of decomposition, two coupled 0D chemical kinetic models were developed and an experiment platform was established to verify the simulation results. The measured and predicted concentrations of SOF2, SO2F2 and SO2 were compared and found to have a reasonable agreement. The time-dependent generation mechanisms of SOF4 and HF were also predicted by the simulation model. The influence of moisture and oxygen impurities was examined; their presence increased the concentration of most of the decomposition products, with moisture generally having a stronger effect; the main exception is SOF4, whose production is predicted to be inhibited by the presence of moisture. Finally, the dominant pathways involving these five species in the plasma region and the gas region were analyzed to determine the dominant chemical processes for the generation and loss of these decomposition products.

This paper is devoted to the computation of the non-equilibrium composition of an SF6 plasma, and determination of the dominant particles and reactions, at conditions relevant to high-voltage circuit breakers after current zero (temperatures from 12 000 K to 1000 K and a pressure of 4 atm). The non-equilibrium composition is characterized by departures from both thermal and chemical equilibrium. In thermal non-equilibrium process, the electron temperature (T e) is not equal to the heavy-particle temperature (T h), while for chemical non-equilibrium, a chemical kinetic model is adopted. In order to evaluate the reasonableness and reliability of the non-equilibrium composition, calculation methods for equilibrium composition based on Gibbs free energy minimization and kinetic composition in a one-temperature kinetic model are first considered. Based on the one-temperature kinetic model, a two-temperature kinetic model with the ratio T e/T h varying as a function of the logarithm of electron density ratio (n e/ nemax ?> ) was established. In this model, T* is introduced to allow a smooth transition between T h and T e and to determine the temperatures for the rate constants. The initial composition in the kinetic models is obtained from the asymptotic composition as infinite time is approached at 12 000 K. The molar fractions of neutral particles and ions in the two-temperature kinetic model are consistent with the equilibrium composition and the composition obtained from the one-temperature kinetic model above 10 000 K, while significant differences appear below 10 000 K. Based on the dependence of the particle distributions on temperature in the two-temperature kinetic model, three temperature ranges, and the dominant particles and reactions in the respective ranges, are determined. The full model is then simplified into three models and the accuracy of the simplified models is assessed. The simplified models reduce the number of species and reactions by a factor of about 2, while providing results that agree closely with the full model. Thus, the physicochemical processes of SF6 arc can be characterized by relatively few species and reactions in each temperature range. It is noted that the simplified models can also be applied to a wide range of pressures, 1–16 atm, conditions which cover most circuit breaker applications. The simplified species and reactions will allow the computing time of multi-dimensional models, taking into account departures from both thermal and chemical equilibrium, to be decreased dramatically while capturing the main physicochemical processes in SF6 arcs.