Various concentric-ring patterns formed in a water-anode glow discharge operated at atmospheric pressure

Pattern formation is a very interesting phenomenon formed above a water anode in atmospheric pressure glow discharge. Up to now, concentric-ring patterns only less than four rings have been observed in experiments. In this paper, atmospheric pressure glow discharge above a water anode is conducted to produce diversified concentric-ring patterns. Results indicate that as time elapses, the number of concentric rings increases continuously and up to five rings have been found in the concentric-ring patterns. Moreover, the ring number increases continuously with increasing discharge current. The electrical conductivity of the anode plays an important role in the transition of the concentric patterns due to its positive relation with ionic strength. Hence, the electrical conductivity of the water anode is investigated as a function of time and discharge current. From optical emission spectrum, gas temperature and intensity ratio related with density and temperature of electron have been calculated. The various concentric-ring patterns mentioned above have been simulated at last with an autocatalytic reaction model.

Influence of Wind Speed Forecasting Error on the Choice of the Number of Balancing System Batteries

In the energy balancing system of distributed generation systems with RES (renewable energy sources), in particular with wind turbines, the effective use of the battery of the balancing system depends on the charge-discharge modes that are implemented. To be effectively used in an energy balancing system, the RES control system should coordinate the processes of energy generation and accumulation in the system through the implementation of operational management with forecasting. Depending on the characteristics of the battery and the accuracy of the measurement or prediction of the energy the battery capacity (or the number of batteries) that will provide the specified control range (controlled operation area) needs to be chosen. Empirical relations (equations) devoted to the dependence of the battery capacity on the discharge current and to the change of voltage at the terminals of the battery during direct current discharge were listed. Among the equations Peukert’s law was chosen. A general view of the dependence of the battery capacity on the discharge current was shown. The formula for Peukert's constant (coefficient) was given. 5 Packert's law limitations were listed including the fact that the effect of temperature on the battery is not taken into account. The influence of depth charge-discharge and the number of discharge cycles on the capacitance was shown. In the process of using the battery and increasing the number of charge-discharge cycles, the capacity decreases. Peukert’s formula was extended to be influenced by temperature: both the Peukert’s capacity and the Peukert’s coefficient depend on the temperature because the Peukert’s coefficient depends on the capacity. For further calculations, a rechargeable battery HZB12-180FA from manufacturer HAZE Battery Campany Ltd was chosen. The temperature was taken into account by empirical dependences from the manufacturer and then they were approximated by 3rd order polynomials. Graphical results of the approximation were shown. The formula of dependency between the power of the wind turbine and the wind speed was shown. The connection between wind speed prediction error, amount of power that could not be obtained because of that and the number of batteries that would provide the specified control range (controlled operation area) was shown. Thus, for calculation of the number of batteries the depth of discharge, temperature and prediction (measurement) error were taken into account. Example dependences of the number of batteries on the wind speed error at temperatures of -20 °C, 0 °C and 20 °C were shown. Curves of dependence of the number of batteries of the balancing system on the ambient temperature and the error of wind speed forecasting was constructed. As an example, when the prediction error increases from 10% to 15%, the number of batteries needs to be increased by 1.17 times, and when the temperature decreases from 20 °C to 0 °C, the number of batteries needs to be increased by 1.48 times. The results of the work can be used at the stage of planning the wind turbine when choosing the number and capacity of the batteries to be installed. Possible areas of further research are using Peukert's formulas, generalized for other or different types of batteries, using other formulas, except for Peukert’s one, for taking into account the dependence of battery capacity on discharge current, using a non-empirical approach to include dependency on temperature.

Developing Shunt-Current Minimized Soluble-Lead-Redox-Flow-Batteries

Shunt currents in membraneless soluble-lead-redox-flow-batteries (SLRFB) are observed in open-circuit condition and found to depend on size of the stack, manifolds, flow rates and charge/discharge parameters. Ramifications of shunt currents on the performance of membraneless SLRFB stacks with internal and external manifolds are reported. In the case of stacks with 3, 5 and 7-cells and internal manifold design, the charge current for the middle cell decreases by 3.3%, 6%, and 8.5%, while the discharge current increases by 2.6%, 5.5%, and 6.6% , respectively, for 3 A charge/discharge current. By contrast, no such adverse effect is observed for external manifold design. The current – potential studies show that while the stacks comprising 3 and 5-cells deliver a maximum power density of 35 mW/cm2, which declines to 15 mW/cm2 for the 7-cell stack with internal manifold design, while the power density remains invariant at 50 mW/cm2 for stacks with external manifold design. An 8-cell stack of 12 V, 50 mAh/cm2 specific capacity and 273 Wh energy storage capacity with 64% energy efficiency is also reported which shows good cyclability over 100 cycles with 95% coulombic efficiency when cycled at 20 mA/cm2 current density for 1h duration.

High-Voltage Nanosecond Discharge as a Means of Fast Energy Switching

The formation of a nanosecond discharge with the use of a Hamamatsu streak-camera and with simultaneously wideband (10 GHz) measurement of voltage and displacement current caused by a streamer in one pulse has been studied. Nanosecond voltage pulses of various amplitudes (16, 20, and 27 kV) were applied across a point-to-plane gap (8.5 mm) filled with air at various pressures (13, 25, 50, 100, and 200 kPa). It was found that the voltage across the gap drops as soon as a streamer appears in the vicinity of the pointed electrode. At the same time, a pre-breakdown current begins to flow. The magnitude of the pre-breakdown current, as well as the voltage drop, is determined by the rate of formation of dense plasma and, accordingly, by the rate of redistribution of the electric field in the gap. The streamer velocity determines the rise time and amplitude of the current. The higher the streamer velocity, the shorter the rise time and the higher the amplitude of the pre-breakdown current. The propagation of a backward and third ionization waves was observed both with the streak camera and by measuring the displacement current. As they propagate, the discharge current increases to its amplitude value.

Investigation on Material Removal Rate and Surface Finish in Electrical Discharge Machining of AA 6061-B4C Composite Material

One of the non-conventional techniques of metal removal manufacturing processes is electrical discharge machining (EDM). The objective of this paper is to prepare a composite material consisting of a matrix of Aluminium AA 6061 alloy and Boron carbide (B4C) as reinforcement and investigate the output responses, the material removal rate, the quality of the surface formed and overcut during EDM process. The process parameters discharge current, Pulse on time and Duty cycle along with the weight % of B4C are considered for investigation to investigate the output responses such as material removal rate, surface roughness and overcut. From the experimental results, it is observed that the weight % of reinforcement has more influence on the material removal rate. The parameters discharge current and pulse-on-time plays an important role in reducing the surface roughness and overcut. Microstructural study helps in understanding the effect of process parameters on the output responses.

A comprehensive investigation on machining of composites by EDM for microfeatures and surface integrity

In electro-discharge machining (EDM), the material removal takes place by precisely controlled sparks that occur between tool and workpiece separated with a spark gap in the presence of a dielectric. Generally, the non-contacting type and less material removal rates are attributed to attain a good surface finish and close dimensional tolerances during an EDM of monolithic metals and alloys. But the dimensional accuracy and surface integrity parameters would considerably affect during EDM of composites due to the existence of more than one material phase constituents. Therefore, the present work aims to study and optimize the performance characteristics under various EDM conditions employed in making rectangular channels on AA6061-B4C composite material. Initially, AA6061-4wt.%B4C composites were fabricated by ultrasonically assisted stir-casting, and the improved properties were obtained from various mechanical characterizations. The EDM experiments were conducted according to the full factorial experimental design. The three levels of input conditions such as discharge Current (I), discharge duration (T On), and discharge idle time (T Off) were considered. The considered output responses are material removal rate (MRR),taper (θ) of the machined channel, tool wear rate (TWR), average surface roughness (R) of the machined surface, and average recast layer thickness (ARLT) of the machined zone. These responses are co-related with multi-objective types in the sense that the MRR has to be maximized with all other responses minimized. Hence, principal component analysis (PCA) coupled with grey relation analysis (GRA) was used for optimization in which the results were normalized, and all the responses were converted into a single response named weighted grey relation grade (WGRG) for each trial. The experimental trial, which had the highest WGRG, was considered as a local optimum. The global optimum parameters were obtained by performing the Taguchi method (TM) (higher-the-better) for the maximization of WGRG. The analysis of variance (ANOVA) was performed to know the contribution of each EDM parameter toward the WGRG. The optimum levels of Current, T On, and T Off were identified as 8 A, 25 µs, and 36 µs, respectively. Results showed that all three input parameters significantly affected the WGRG, and a higher contribution of Current (52.11%) followed by the T On (26.72%) was observed. The interaction between the Current and T Off was found to be greater than other interactions. Taper values were observed to be reduced at the combination of 8 A discharge Current and 25 µs T On. None of the input parameters significantly affected the Ra, except for Current, which showed a slight effect. ARLT values showed an increasing trend of T On from 25 µs to 45 µs but decreased slightly at 65 µs for all Current levels. The moderate Current level 6 A was observed to be favorable in reducing ARLT when compared to low (4 A) and high (8 A) for all Ton values.

THE INFLUENCE OF CATHODE MATERIAL ON THE CHARACTERISTICS OF PULSED NEGATIVE CORONA IN OXYGEN

Change in time for the shape of the discharge current pulses of the pulsed negative corona in oxygen with cop-per and stainless steel cathodes has been studied for two discharge modes. The change lies in the decrease of the pulse amplitude and duration at half maximum. It is shown that for stainless steel cathodes, the amount of electric charge transferred in one pulse of the discharge current is 15% greater than for copper cathodes. It is also shown that under the maximum load mode, the amount of charge transferred in one pulse of the discharge current is de-creased with time by 10% for both types of cathodes. It is shown that ozone synthesis in the electrode system with copper cathodes is 25% more efficient.

Forecasting Methods of Battery Charge and Discharge Current Profile for LEO Satellites

The orbital characteristics of low Earth orbit (LEO) satellite systems prevent continuous monitoring because ground access time is limited. For this reason, the development of simulators for predicting satellite states for the entire orbit is required. Power-related prediction is one of the important LEO satellite simulations because it is directly related to the lifespan and mission of the satellite. Accurate predictions of the charge and discharge current of a power system’s battery are essential for fault management design, mission design, and expansion of LEO satellites. However, it is difficult to accurately predict the battery power demand and charging of LEO satellites because they have nonlinear characteristics that depend on the satellite’s attitude, season, orbit, mission, and operating period. Therefore, this paper proposes a novel battery charge and discharge current prediction technique using the bidirectional long short-term memory (Bi-LSTM) model for the development of a LEO satellite power simulator. The prediction performance is demonstrated by applying the proposed technique to the KOM-SAT-3A and KOMSAT-5 satellites operating in real orbits. As a result, the prediction accuracy of the proposed Bi-LSTM shows root mean square error (RMSE) within 2.3 A, and the prediction error well outperforms the most recent the probability-based SARIMA model.