Input Gas Flow Rate Research Articles

Studies on the Morphological and Mechanical Properties of TiZrHfNiCuCo Metallic Coatings Deposited by DC Magnetron Sputtering

This research aimed to investigate the effects of input power and gas flow rate on the composition, microstructure, and mechanical properties of TiZrHfNiCuCo metallic coatings. These metallic coatings were deposited on a p-type Si wafer using a direct current magnetron sputtering system with varying input powers (100–300 W) and Ar flow rates (5–20 sccm). It was observed that increasing input power and decreasing Ar flow rate led to TiZrHfNiCuCo metallic coatings with higher hardness and smoother surfaces. The experiment resulted in the formation of a metallic amorphous coating. This study describes the mechanism by which the mechanical properties of the TiZrHfNiCuCo coating change according to sputtering parameters. Based on these results, the effects of sputter variables, such as input power and gas flow rate properties, on the properties of coatings are discussed.

Insight in NO synthesis in a gliding arc plasma via gas temperature and density mapping by laser-induced fluorescence

A gliding arc (GA) plasma, operating at atmospheric pressure in a gas mixture of 50% N2 and 50% O2, is studied using laser-induced fluorescence spectroscopy. The main goal is to determine the two-dimensional distribution of both the gas temperature and the NO ground state density in the afterglow. As GA plasma discharges at atmospheric pressure normally produce rather high NO x densities, the high concentration of relevant absorbers, such as NO, may impose essential restrictions for the use of ‘classical’ laser-induced fluorescence methods (dealing with excitation in the bandhead vicinity), as the laser beam would be strongly absorbed along its propagation in the afterglow. Since this was indeed the case for the studied discharge, an approach dealing with laser-based excitation of separate rotational lines is proposed. In this case, due to a non-saturated absorption regime, simultaneous and reliable measurements of both the NO density and the gas temperature (using a reference fitting spectrum) are possible. The proposed method is applied to provide a two-dimensional map for both the NO density and the gas temperature at different plasma conditions. The results show that the input gas flow rate strongly alters the plasma shape, which appears as an elongated column at low input gas flow rate and spreads laterally as the flow rate increases. Finally, based on temperature map analysis, a clear correlation between the gas temperature and NO concentration is found. The proposed method may be interesting for the plasma-chemical analysis of discharges with high molecular production yields, where knowledge of both molecular concentration and gas temperature is required.

High-Speed Generation of Microbubbles with Constant Cumulative Production in a Glass Capillary Microfluidic Bubble Generator.

This work reports a simple bubble generator for the high-speed generation of microbubbles with constant cumulative production. To achieve this, a gas-liquid co-flowing microfluidic device with a tiny capillary orifice as small as 5 μm is fabricated to produce monodisperse microbubbles. The diameter of the microbubbles can be adjusted precisely by tuning the input gas pressure and flow rate of the continuous liquid phase. The co-flowing structure ensures the uniformity of the generated microbubbles, and the surfactant in the liquid phase prevents coalescence of the collected microbubbles. The diameter coefficient of variation (CV) of the generated microbubbles can reach a minimum of 1.3%. Additionally, the relationship between microbubble diameter and the gas channel orifice is studied using the low Capillary number (Ca) and Weber number (We) of the liquid phase. Moreover, by maintaining a consistent gas input pressure, the CV of the cumulative microbubble volume can reach 3.6% regardless of the flow rate of the liquid phase. This method not only facilitates the generation of microbubbles with morphologic stability under variable flow conditions, but also ensures that the cumulative microbubble production over a certain period of time remains constant, which is important for the volume-dominated application of chromatographic analysis and the component analysis of natural gas.

Solid Oxide Electrochemical Cells for Nitrogen and Oxygen Production

Nitrogen and oxygen are both very important commodities with a wide variety of applications in industries, such as chemical, food and metallurgical plants as well as in the medical sector. Nowadays most of the nitrogen and oxygen are produced via air separation technologies such as cryogenic distillation (ASU) or pressure swing adsorption (PSA). Both ASU and PSA offer economical and mature ways for nitrogen and oxygen production at large (>100 ton/day) or medium scales (20-100 tons/day). If one can develop a technology for providing these gases in an energy efficient and cost effective way also at small scale, preferably driven by electricity only, this would enable new applications of the gases. Such a technology would match characteristics of the future green electricity system relying on small scale (few MWs) power generation and fluctuating production..In this work we present an efficient electrochemical process for N2 and O2 production based on a solid oxide electrochemical cell technology by oxygen extraction from air. Cells with a 53 × 53 mm2 size were produced by a conventional tape casting method. They consist of a ca.10 μm CGO (Ce0.9Gd0.1O2-δ) electrolyte sandwiched between composite electrodes made from either LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) - CGO, or LSF (La0.6Sr0.4FeO3-δ) - CGO. To boost performance at low temperature, the electrodes were infiltrated with Pr-oxide. The electrochemical performance with the different supports were characterized by obtaining current-voltage (iV) characteristics at different temperatures as well as through electrochemical impedance spectroscopy(EIS) with or without infiltration. For characterization, air was used as feed stock to the cathode compartment and air, or oxygen was used as sweep gas to the anode compartment. A voltage below 200 mV is needed to drive a current of 1 A/cm2 through the cell, which can provide a purity of 90% of N2 out at an operation temperature of 650 °C (see Figure 1a). The cells were demonstrated to operate for producing a 98% pure N2 stream without degradation over a 1500 h period (see Figure 1b).Further analysis show that the specific power consumption calculated based on the power input and outlet gas flow rate for 90% N2 production is ca. 0.1 kWh/m3 and the specific power consumption for 96% and 98% N2 production is 0.21 and 0.31 kWh/m3, respectively. A 3-fold increase in required power is observed when going from a N2 purity from 90% to 98%.Detailed electrochemical analysis and the electrochemical performance comparison between LSCF and LSF based mixed ionic electronic conductor (MIEC) electrodes will be presented. Factors limiting cell performance will as well as analysis of optimal point of operation in terms of energy consumption and reliability will also be discussed. Acknowledgment This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 862482. Figure 1

Computational and experimental research on the performance of ECRIT ion source with nitrogen propellant

Electron cyclotron resonance ion thruster (ECRIT) with a diameter of 2 cm has the characteristics of no hot cathode and high specific impulse, which is suitable for the air-breathing electric propulsion system. In order to adapt to the atmospheric composition characteristics of nitrogen and oxygen in low orbit, the computational and experimental research on the performance of the ECRIT ion sourse with nitrogen propellant is an important basis for analyzing the feasibility of applying ECRIT to the air-breathing electric propulsion system. In this paper, the global model of the nitrogen ECRIT ion source with a diameter of 2 cm is established to calculate its performance. Then, the computational results are compared with the experimental results to analyze the difference. The research results show that when the input power of the ion source is 8 W and the gas flow rate is 2 ml/min, the computational and experimental results of the extracted ion beam current and thrust reach the maximum with the extracted beam current of 16.2 and 12.5 mA and the thrust of 476.6 and 368 μN, respectively. When the input power is 8 W and the gas flow rate is 0.6 ml/min, the computational and experimental results of the specific impulse are 2 095.8 and 1 855.6 s, both reaching the maximum value. The relative errors between the computational and experimental results of the extracted ion beam current, thrust and specific impulse all range from 2% to 32%. When the input power and gas flow rate used are 8 W and 1 ml/min in calculation, and 8 W and 0.8 ml/min in experiment, the ion source is on the optimal operating state. At this situation, the computational and experimental propellant utilization efficiencies with 17.8% and 16.2% respectively are high, and the ion energy loss with 443.9 and 596.2 W/A respectively is low.

Study of plasma parameters and gas heating in the voltage range of nondischarge to full‐discharge in a methane‐fed dielectric barrier discharge

AbstractExperimental data are used in theoretical models to study the effects of input voltage and gas flow rate on plasma and background gas parameters in a voltage range where the transition from nondischarge to full‐discharge happens. To this end, a specific methane‐fed dielectric barrier discharge is used as a plasma reactor, and electrical modeling, the Boltzmann equation method, and emission spectrum analysis are employed to calculate plasma parameters and gas heating. The output of this study proves that a uniform plasma with a controllable background gas heating is achievable by the adjustment of input parameters such as voltage and gas flow rate in a well‐designed dielectric barrier discharge.

Sustainable Development Solutions for the Medical Waste Problem Using Thermal Plasmas

Waste-to-energy (WTE) conversion is a vital process in the Middle East, especially in the Kingdom of Saudi Arabia (KSA), which is considered sustainable development for the environmental strategic project. Previous publications dealt with the environmentally friendly plasma treatment of wastes such as municipal waste, scrap tire waste, plastic waste, and grey water, using thermal plasmas produced by the cornerstone part of plasma reactors, namely the air plasma torch. In the present paper, with a view to energy recovery from medical waste, the thermodynamic properties of air plasma torches with a flow rate of air ranging from 10 mg/s to 30 mg/s and plasma jet temperatures ranging from 1500 °C to 5000 °C were investigated; these include power loss, enthalpy, plasma flux, and torch efficiency variation with plasma input power and air flow rate. The measured electrothermal efficiency of the plasma torch is in the range of 42% to 80% and increases with the increasing input power and gas flow rate. In Makkah, the number of beds in the hospitals is 10,500; the average annual weight of the medical waste in the hospitals is 2835 × 103 t, with an extracted amount of pyrolysis oil equivalent to 2268 × 103 t and an equivalent energy of 90 × 109 M J. In the proposed plasma treatment project, the amount of diesel oil after the distillation process will reach up to 1928 × 103 t, with an estimated sale profit of the electricity reaching up to 21 × 106 MW·h. The sale profit of pyrolysis oil in 2022 reaches up to USD 34.44 million, and the sale profit of electricity extracted by using the diesel oil in 2022 reaches up to USD 1020 million for households and USD 1445 million for factories.

Synergetic enhancement of interfacial properties and impact resistant of UHMWPE fiber reinforced composites by oxygen plasma modification

This study reveals the synergetic enhancement of oxygen plasma treatment on the interfacial properties and impact resistant of ultrahigh molecular weight polyethylene (UHMWPE) fiber-reinforced polymer matrix composites (PMCs). The UHMWPE fiber reinforcement was modified by oxygen plasma with different parameters including input power, treatment time and gas flow rate. Then, the surface physicochemical properties of modified fibers were analyzed. Oxygen plasma modified UHMWPE/vinyl ester composites exhibited an enhanced interface shear performance of 90.99%, which would significantly influence the mechanical properties of the composites. The optimal parameters were proved to be an input power range of 150–180 W, a time range of 120–150 s, and a gas flow rate of 8sccm, at which situation the tensile strength had been enhanced 10.67%, the impact-resistant damage projection area and dent depth had been reduced up to 51.93% and 24%, respectively. Simultaneously, the energy dissipation pattern dominated by fiber fracture was gradually formed in the modified composites, which maximize exploitation of the fiber-reinforcing effect and improved the impact resistance.

Arc dynamics in a vortex-stabilized non-transferred plasma torch with a tangential gas feed

The mode of anode arc attachments in a thermal plasma torch, such as constricted arc, multi-arc or diffused arc attachment, has operational as well as economic consequences on the use of plasma torches in industrial applications. The mode of arc attachment is strongly dependent on the gas flow dynamics, gas vortex formation and wall energy exchange. To gain more insight into arc attachment behaviour, this article presents a transient flow plasma model implemented using OpenFOAM computational fluid dynamics code to study the effect of gas swirl and arc rotation on modes of arc attachments. A tangentially fed plasma gas creates a gas swirl that helps to induce the arc rotation. The investigations were carried out at arc currents between 200–450 A and input gas flow rates in the range of 5–20 slpm. High gas swirl and low arc currents are found to favour constricted attachment on the anode surface. The local gas vortex driven by the plasma swirl creates hot spots inside the torch that dictate the arc attachment. The transition of arc attachment from the diffuse to constricted mode was simulated by imposing a step-change in the gas flow which shows the evolution of different arc attachment behaviour. During the transition from constricted to diffused attachment, the arc tends to undergo a transitionary multi-attachment mode at specific selected current and flow parameters.

Ex-situ biogas upgrading in thermophilic up-flow reactors: The effect of different gas diffusers and gas retention times

Four different types of ceramic gas distributors (Al2O3 of 1.2 μm and SiC of 0.5, 7 and 14 μm) were evaluated to increase biomethane formation during ex-situ biogas upgrading process. Each type of gas diffuser was tested independently at three different gas retention times of 10, 5 and 2.5 h, at thermophilic conditions. CH4 production rate increased by increasing input gas flow rate for all type of distributors, whereas CH4 concentration declined. Reactors equipped with SiC gas distributors effectively improved biomethane content fulfilling natural gas standards. Microbial analysis showed high abundance of hydrogenotrophic methanogens and proliferated syntrophic bacteria, i.e. syntrophic acetate oxidizers and homoacetogens, confirming the effect of H2 to alternate anaerobic digestion microbiome and enhance hydrogenotrophic methanogenesis. A detailed anaerobic bioconversion model was adapted to simulate the operation of the R1-R4 reactors. The model was shown to be effective for the simulation of biogas upgrading process in up-flow reactors.

Thermal Behavior of Oil Shale Pyrolysis under Low-Temperature Co-Current Oxidizing Conditions.

The thermal behavior of the Huadian oil shale during low-temperature co-current oxidizing pyrolysis was studied by lab-scale experiments under different basic pyrolysis temperatures and input gas flow rates. The results showed that, in the process of oil shale co-current oxidizing pyrolysis, the increasing input gas flow rates under the same basic pyrolysis temperatures can significantly enhance the heat generation of oil shale. Meanwhile, it can be seen from the temperature variation characteristics of oil shale that the heat released by the oxidation reaction of semicoke and oxygen is enough to support the thermal decomposition of organic matter without supplemental heating. Moreover, it can be concluded from the 92.06% effective recovery of shale oil that a high yield of oil without a significant loss can be achieved. Finally, compared with increasing basic pyrolysis temperatures, the increased input gas flow rates have a more obvious effect on improving the effective recovery of shale oil.

The investigation of arc fluctuations in thermal plasma torch using 3D modeling approach

Two and three-dimensional transient models of a thermal plasma torch are presented to analyse the effect of operating conditions on arc root fluctuations for various types of anode configuations. The computational fluid dynamics code, OpenFOAM(c), is utilised in a modified form to model the arc and plasma flow inside the argon plasma torch. Modeling a thermal plasma requires a combination of mutually related fluid dynamics and electromagnetic phenomena which dictate the size and stability of the arc column. While the 2D axisymmetric model is effective in depicting the average energy and average velocity profiles of plasma gas, it fails to describe the fluctuations in arc behaviour and its mode of attachment on the anode. In a 3D model, the arc movement is captured in both axial and azimuthal directions wherein the arc-root attachment on anode surface seems to fluctuates in a periodic manner and the voltage fluctuations mirrors the arc-root attachment behaviour within the system. We have here investigated the effect of operating conditions on the frequency of this arc reattachment, finding that the input current and gas flow rate have a significant effect on arc behaviour. We have also reported the effect of arc voltage perturbations on the exit plume properties (velocity and average temperature) and finally the effect of anode nozzle geometry on the fluctuations and plume behavior is presented.

Investigation on the Removal of Carbon Dioxide Exhausted from Industrial Units in a Lab-Scale Fluidized Bed Reactor

In this study, CO2 removal efficiency from flue gas was investigated in a fluidized bed reactor under semi-dry conditions. A lab-scale fluidized bed reactor, filled with inert glass beads, was used to investigate the effect of operating parameters on the CO2 removal efficiency using calcium hydroxide slurry as the absorbent. The Taguchi design method was used to design the experiments. The maximum inlet concentration of CO2 was 3 vol%. The most important factors were the reaction surface area, inlet gas velocity, inlet CO2 concentration, absorbent solution flow rate, inlet gas temperature and calcium hydroxide slurry concentration. The experimental results indicated that the CO2 removal efficiency increased when increasing the effective surface area of the reaction. Moreover, the removal efficiency increased by decreasing the input gas flow rate and inlet CO2 concentration. By performing experiments under optimum conditions, the maximum obtained CO2 removal efficiency was 79%. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Conversion of CO2 in a low-powered atmospheric microwave plasma: In-depth study on the trade-off between CO2 conversion and energy efficiency

The influence of microwave input power (P) and gas flow rate (F) was compared by analyzing the change of CO2 conversion and energy efficiency with the specific energy input. It was found that the influence of input power and flow rate on CO2 conversion (P > F) is opposite to that on energy efficiency (P < F). When the input power and flow rate were increased in the same proportion from (60 W, 600 mL/min) to (150 W, 1500 mL/min), CO2 conversion and energy efficiency could be both improved by a factor of 1.43. The emission spectroscopy diagnostic suggested that this improvement could be attributed to more electron-impact vibrational excitation, which was proved by the increase in vibrational temperature and electron density associated with the decrease in electron temperature.

Efficient degradation of Fipronil in water by microwave-induced argon plasma: Mechanism and degradation pathways

Fipronil and its metabolites are potentially harmful to the ecological environment and have chronic neurotoxic effects, which makes it to be classified as class C carcinogens. Fipronil has been banned from agricultural use in China since 2009, but its residue remains in the environment. Therefore, an efficient and economical method is urgently needed to degrade fipronil residues in the environment. Herein, the degradation of fipronil in water solution using argon microwave-induced plasma (MIP) system was studied and a plausible reaction pathway was proposed in combination with Density Functional Theory (DFT) calculations. The degradation of fipronil by MIP system was optimized in terms of input power, plasma-sample distance, initial concentration and gas flow rate. After short time MIP treatment with an input power of 150 W, as high as 85.62% degradation efficiency was achieved for the fipronil at concentration of 20 mg·L‐−1 under the optimized conditions, and the corresponding energy efficiency was 1334.8 mg·kwh−1. Optical emission spectrometry (OES) was employed to characterize the distribution and intensity of OH, H and O species which play key roles in the degradation of fipronil by plasma, and it revealed that the degradation reaction mainly occurs at gas-liquid interface where the highest intensity of OH, H and O species was observed. High resolution mass spectrometric analysis in combination quantum chemical calculations indicate that a wide diversity of reaction processes occurred for fipronil degradation under MIP treatment, involving oxidation or reduction, nitro reduction, oxidative dichlorination, reductive dichlorination, hydration, dehydration and thiourea to urea. The possible degradation mechanism and pathways were proposed based on the degrading species identified by high resolution Mass Spectrometry (HRMS) and the thermodynamic profiles.

A CFD strategy to retrofit an anaerobic digester to improve mixing performance in wastewater treatment.

To date, mixing design practice in anaerobic digestion has focussed on biogas production, but no adequate consideration has been given to energy efficiency. A coherent, comprehensive and generalized strategy based on computational fluid dynamics (CFD) modelling is proposed to improve mixing efficiency of a full-scale, unconfined gas-mixed digester for wastewater treatment. The model consists of an Euler-Lagrange (EL) model where biogas bubbles are modelled as the Eulerian dispersed phase, and non-Newtonian sludge as the Lagrangian continuous phase. Robustness tests show that mixing predictions are independent of bubble size. The CFD strategy comprises the assessment of different mixing geometries and a range of input gas flow rates. Quantitative results show that simple retrofitting measures are able to achieve a significant improvement in the degree of mixing with reduced mixing times, and consequently recommendations for best mixing geometry and gas flow rate are given. A generalization to a generic digester is discussed in a form that is readily usable by professionals and consultants.

Cell viability and measurement of reactive species in gas- and liquid-phase exposed by a microwave-excited atmospheric pressure argon plasma jet

A microwave-excited atmospheric pressure plasma jet (ME-APPJ) was generated utilizing coaxial transmission line resonators with the resonance frequency of 788 MHz. We investigated the effects of the operating parameters such as input power and gas flow rate on the electron excitation temperature and electron density using optical emission spectroscopy. The amounts of various reactive species in the plasma-activated media (PAM) exposed by the ME-APPJ were estimated using colorimetric methods. The PAM was applied to A549 cultured cells and subsequently incubated for a given duration. The concentrations of NO2− and H2O2 in the PAM incubating A549 cells were monitored until 24 h. The reduced cell viability rate was observed on A549 cells incubated in the PAM. The concentrations of NO2− and H2O2 and the viability of A549 cells depended on the operating conditions of ME-APPJ. The cell viability rate exhibited a decrease with increasing power and decreasing gas flow rate. Correlation between the concentrations of gaseous reactive species in the plasma and in the PAM and the cell viability is discussed.

Pressurized cultivation strategies for improved microbial hydrogen production by Thermococcus onnurineus NA1.

While the hydrogen economy is receiving growing attention, research on microbial hydrogen production is also increasing. Microbial water-gas shift reaction is advantageous as it produces hydrogen from by product gas including carbon monoxide (CO). However, CO solubility in water is the bottleneck of this process by low mass transfer. Thermococcus onnurineus NA1 strain can endure a high-pressure environment and can enhance hydrogen production in a pressurized reactor by increasing CO solubility. As CO causes cell toxicity, two important factors, pressure and input gas flow rate, should be considered for process control during cultivation. Hence, we employed different operational strategies for enhancing hydrogen production and obtained 577mmol/L/h of hydrogen productivity. This is the highest hydrogen productivity reported to date from microbial water-gas shift reaction.

Effects of input power, gas flow rate and hydrogen concentration on Cu film deposition by a radio frequency driven non-thermal atmospheric pressure plasma jet

A radio frequency driven non-thermal atmospheric plasma jet with a copper wire used as precursor is applied for Cu film deposition. The effects of input power, hydrogen concentration (CH2) and gas flow rate on the discharge parameters, and eventually on film deposition rate and its properties are investigated. The results show that, besides the plasma gas temperature (Tg), the discharge current flowing through the copper wire (Ifc) is also a key parameter for Cu film deposition. With increasing input power, both Tg and Ifc increase, which both facilitate the increase of film deposition rate, surface roughness and particle size on the film. Higher gas flow rate leads to lower Tg, and results in the decrease of the deposition rate, surface roughness and particle size. The influences of CH2 in plasma forming gas on Cu film deposition have dual characters, due to the increase in the Tg and decease in the Ifc with CH2 increase. When the CH2 is below1.6‰, increasing CH2 has promotion role on the film deposition rate increase and particle size enlargement on the film, and the results reverse as the CH2 is above 1.6‰.

Spectroscopic diagnosis of gas temperature in blown-out plasma of atmospheric-pressure microwave oxygen plasma torch

The gas temperature of atmospheric-pressure microwave oxygen plasma torch in a blown-out plasma is diagnosed by optical emission spectroscopy (OES) via the atmospheric band O2(b1Σg+ →X3Σg−). The variations of gas temperature with respect to input power and gas flow rate are investigated, as well as the spatial distribution of gas temperature along the blown-out plasma. And the limitation of OES diagnosis in the experiment is discussed extensively. Moreover, the morphology of plasma torch is also inspected at various gas flow rates and values of microwave power.