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The fabrication of film cooling holes on components coated with thermal barrier is challenging because the physical and chemical properties of each layer are quite different. Electrochemical discharge machining (ECDM) is a promising machining method for producing the film cooling holes on such multi-layer materials. Observation of the discharges show different characteristics when machining ceramic-coated Ni-superalloys. In this investigation, the discharge current during machining of both the coating and the superalloy substrate were recorded and analyzed. Experimental results indicate that the electrochemical discharge exists only during the machining of the coating, while both electrochemical discharge and electrical discharge take place when machining the superalloy substrate. Further analysis of the experimental results revealed that electrical discharge is the main contributor to material removal on the superalloy substrate, and the electrochemical discharge causes a small secondary material removal on the machined surface, resulting in a reduction of surface roughness. [ABSTRACT FROM AUTHOR]

CO 2 constitutes around 95 % of the atmosphere on Mars, and its in-situ utilization is of great value. O 2 is a significant target product transformed from CO 2 that can support both human respiration and fuel combustion, its conversion mechanism remains unclear. In this study, using a dielectric barrier discharge (DBD) with parallel plate electrodes, simulation and experimental results are combined to discuss the discharge characteristics and CO 2 conversion process, under Mars conditions. The DBD was driven by a repetitive frequency microsecond pulse voltage. According to the discharge current, the discharge process can be split into four stages, namely the positive (negative) discharge stage and the positive (negative) discharge extinguishing stage. With a contribution up to 98 % and primarily taking place in the positive discharge extinguishing stage, the recombination decomposition reaction of electron and CO+ 2 is the primary pathway of O 2 synthesis. At the position near the edge of the cathode potential drop zone, electron impact ionization of CO 2 ground state molecules dominates the formation of CO+ 2. Under the range of pulse parameters considered in this paper, increasing the pulse width can lengthen the time of recombination decomposition reaction of electron and CO+ 2 in positive discharge extinguishing stage, which is favorable for the formation of O 2. Likewise, reducing the pulse's rising edge can increase the discharge intensity and CO+ 2 density, which is also favorable to O 2 production. • The discharge characteristics of DBD was analyzed, the plasma was further used to convert CO 2 to O 2 under Martian pressure. • The main pathway to produce O 2 is recombination decomposition reaction of e and CO+ 2 , with a contribution of more than 95 %. • CO+ 2 is mainly produced by electron impact ionization of ground state CO 2 near the cathode drop region during discharge. [ABSTRACT FROM AUTHOR]

A cyclic volume and surface dielectric barrier discharge (V-SDBD) plasma wastewater treatment system with stainless steel net as discharge electrode was established and applied to the sulfadiazine (SDZ) degradation. The discharge characteristics, active substance yield and relative emission spectra in different net electrode systems were compared. The SDZ degradation as well as the UV–vis spectra and COD removal of the SDZ solutions under different treatment conditions were investigated to achieve the appropriate mesh parameter of the net electrode and circulating velocity of the solution. The obtained results show that the SDZ had a better degradation in the cyclic V-SDBD system than that in the intermittent DBD system. 10-mesh stainless steel net and 333 mL min−1 circulating flow rate were the optimal reaction conditions for the SDZ degradation. Compared with the other three net electrodes (14, 20 and 40-mesh), the 10-mesh electrode system could produce more H 2 O 2 and O 3 , and the relative emission spectrum had stronger intensity. The results of voltage and current waveform and Lissajous figures show that the air ionization in the V-SDBD system with 10-mesh electrode was higher, and more micro-discharge channels could be generated in the discharge space. UV–vis spectra and COD removal analysis of SDZ solutions also stated the SDZ degradation in the V-SDBD plasma system. According to the byproducts' identification, SDZ degradation pathway was speculated and the change of solution toxicity was analyzed. The results verified that the total toxicity of the initial SDZ solution could be reduced after treating in the V-SDBD plasma system. [Display omitted] • The established cyclic V-SDBD plasma had better effect on the SDZ degradation. • The air ionization in the V-SDBD system with 10-mesh electrode was higher. • 10-mesh stainless steel net electrode was favorable for the SDZ degradation. • The total toxicity of the initial SDZ solution decreased after treatment. [ABSTRACT FROM AUTHOR]

Abstract: The measurement of power and current is very important to study discharge characteristics of dielectric barrier discharge (DBD). In order to analyze the effect of measure elements on discharge characteristics of DBD, three different resistors and capacitors are used for measuring discharge current and power, respectively. The resistance values of the resistors are 5.1Ω, 15Ω and 56Ω. The capacitances of the capacitors are 2.2 nF, 22 nF and 150 nF. The experiments are carried out in a stainless mesh electrode DBD system. The discharge characteristics are obtained by using Lissajous figures and the discharge current. The results show that smaller capacitance and bigger resistance are suitable for obtaining the perfect lissajous and discharge current due to their improving the stability of DBD. [Copyright &y& Elsevier]

A wide variety of processes make use of plain orifice nozzles. Fuel injectors for internal combustion engines incorporate these nozzles to generate finely atomized sprays. Processes such as jet cutting, jet cleaning, and hydroentanglement, on the other hand, use similar nozzles, but require coherent jets. The spray or jet characteristics depend on the stability of the flow emerging from the orifice. This problem has been extensively researched for nozzles with diameters above 300 μm. Much less is known about the characteristics of jets produced by nozzles with smaller diameters, where viscous effects and small geometric variations due to manufacturing tolerances are likely to play an increasing role. Results are presented of a wide-ranging investigation of geometry effects on the flow parameters and jet characteristics of nozzles with diameters between 120 and 170 μm. Nozzles with circular cross-section and conical, cone-capillary and capillary axial designs were investigated. For conical and cone-capillary nozzles, the effect of cone angle and effects due to interactions between adjacent nozzles in the multi-hole cone-capillary nozzles were studied. For capillary nozzles, the effects of diameter variations and inlet edge roundness for capillary nozzles were considered. Furthermore, the effect of varying the aspect ratio (ratio of major and minor axes) of elliptical nozzles was studied. Flowrate and jet impact force measurements were carried out to determine the discharge coefficient Cd, velocity coefficient Cv, and contraction coefficient Cc of the nozzles for supply pressures between 3 and 12 MPa. Visualizations of the jet flow were carried out in the vicinity of the nozzle exit in order to identify near-nozzle flow regimes and to study jet coherence. The relationship between nozzle geometry, discharge characteristics, and jet coherence is examined. [ABSTRACT FROM AUTHOR]

• CO 2 reforming of CH 4 was performed in DBDs with different dielectric layers. • More intensified filamentary microdischarges were displayed in DBD-SD. • DBD-SD exhibited higher reactant conversion and liquid product selectivity. • Higher gas product selectivity and stable carbon balance were achieved in DBD-DD. • Higher energy efficiency for plasma reforming process was obtained in DBD-SD. CO 2 reforming of CH 4 in a non-thermal plasma process (e.g., dielectric barrier discharge, DBD) possesses dual benefits for our environment and energy needs. However, this process is strongly influenced by the dielectric structure of the DBD. Here, plasma CO 2 reforming of CH 4 has been performed in both single-dielectric and double-dielectric DBD (DBD-SD and DBD-DD) reactors under atmospheric pressure. Electrical and optical characterization, along with temperature measurements are performed to understand the influence of the DBD-SD and DBD-DD designs. Reactor performance for reforming is compared under different discharge powers. The results show that CO 2 /CH 4 discharges in both DBD-SD and DBD-DD display typical filamentary microdischarges. Compared with the DBD-DD, the DBD-SD reactor exhibits a larger number and higher intensity of current pulses, which leads to a higher electron density and formation of reactive species. The highest conversion of CO 2 (24.1 %) and CH 4 (49.2 %) are achieved in the DBD-SD at a high discharge power (75 W). Moreover, higher selectivities of gaseous products are obtained in the DBD-DD, while the DBD-SD reactor shows a higher selectivity for liquid products, mainly including methanol and acetic acid. The highest energy efficiencies for reactant conversion (0.34 mmol/kJ), gaseous and liquid production formation (0.26 mmol/kJ and 0.015 mmol/kJ) are achieved in the DBD-SD reactor at a low discharge power (22 W), resulting from the low energy loss to the environment. However, the carbon deposited on the inner electrode surface in the DBD-SD would have an adverse influence on the reactor's performance. Further research on the optimization of the DBD reactor to establish an efficient plasma-catalysis system is required for industrial applications. [ABSTRACT FROM AUTHOR]