Initial Gas Concentration Research Articles

A hybrid back-propagation neural network and intelligent algorithm combined algorithm for optimizing microcellular foaming injection molding process parameters

The microcellular foaming injection molding process can effectively reduce the product weight and facilitate the realization of automobile lightweight, which is greatly affected by process parameters. Warpage of microcellular foaming material will increase, affecting the dimensional stability of the product, unless the process parameters are effectively controlled by process parameters. Warpage of microcellular foaming material has been based on key process variables including mold temperature, melt temperature, coolant temperature, coolant Reynolds number, v/p switch over, initial foaming volume, initial bubble radius and initial gas concentration. In order to reduce warpage of microcellular foaming material, the input and output data obtained from the Finite Element (FE) simulations are used to train BP neural network, GABP neural network and PSOBP neural network as prediction model for the warpage. Comparing the performance of the three methods in prediction error and training time, PSOBP is considered as the best prediction model for the warpage of microcellular foaming material. It has been proved that the prediction model has the ability to predict the warpage of the plastic within an error range of 1 %. The prediction model can be optimized by genetic algorithm to find the best combination of process parameters. The optimized warpage value is 0.7038 mm, which effectively reduces warpage of microcellular foaming material. Finally, finite element simulation and physical tests are carried out to verify the accuracy of the method to optimize microcellular foaming injection molding process parameters.

Degradation of ammonia from gas stream by advanced oxidation processes

The reduction of ammonia emissions from air was experimentally investigated by advanced oxidation processes (AOPs) utilizing the combination of ultraviolet irradiation with ozone. The influence of operating conditions such as initial ammonia concentration and flow rate of gas on the reduction of ammonia concentration was investigated in homemade photochemical unit. The conversion of ammonia decreased with increasing initial concentration of ammonia and with increasing flow rate of air (decreasing retention time). The highest conversion of ammonia (97%) was achieved under lower initial concentration of ammonia (30 ppm) and lower flow rate of air (28 m3/h). The energy per order was evaluated for the advanced oxidation process too. The energy consumption was about 0.037 kWh/m3/order for the 97% ammonia conversion at 30 ppm of initial ammonia concentration and 28 m3/h flow rate of air. Based on the results, the advanced oxidation process combining the UV irradiation and ozone was effective for mitigation of ammonia concentration and presents a promising technology for the reduction of odor emissions from livestock buildings. Moreover, the AOPs are suitable for application for high flow rate of air, especially for ammonia abatement from livestock buildings, where very high efficiency is expected.

Intensification of CO₂ capture by monoethanolamine solution containing TiO2 nanoparticles in a rotating packed bed

This study investigates the mass transfer intensification in the absorption of carbon dioxide (CO₂) into a monoethanolamine (MEA) solution enhanced by TiO2 nanoparticles in a typical rotating packed bed (RPB). The overall volumetric gas phase mass transfer coefficients (KGa) were investigated in a counter-current RPB with blade packings. The effects of TiO2 and MEA concentrations, rotational speed, initial concentration of CO₂, gas and liquid flow rates on KGa were specified. The rotational speed had positive effects on KGa. It is deduced that TiO2 nanoparticles led to enhanced CO₂ capture efficiency of over 26.9 % and enhancement in KGa from 7.5%–96.1% for MEA based TiO2 suspension in comparison with MEA solution without nanoparticles. Therefore, TiO2 nanoparticles can augment the mass transfer coefficient and intensify the CO₂ absorption, even in a high-efficiency equipment like a high gravity RPB.

Effects of concentration, temperature, ignition energy and relative humidity on the overpressure transients of fuel-air explosion in a medium-scale fuel tank

Experiments were conducted in a 907.5-L fuel tank to investigate the effects of concentration, temperature, ignition energy, and humidity on the explosion overpressure transients of gasoline-air mixture explosions. The results show that the overpressure-time profiles can be roughly divided into four stages: incubation stage, slow acceleration stage, abrupt acceleration stage, descending stage. During the explosion process, intense overpressure oscillation occurred in the fuel tank. Specifically, both the maximum overpressure (pmax) and the maximum rate of overpressure rise ((dp/dt)max) increased firstly and then decreased as the gasoline concentration increased, and the correction between overpressure parameters and gasoline concentration is approximately cubic polynomial. The peak values of pmax and (dp/dt)max were obtained at the concentration of 1.71%.The influence of temperature on pmax and (dp/dt)max was relatively complex, which may result from the vessel volume and the initial gas concentration. Moreover, with the increase of ignition energy, pmax and (dp/dt)max according to a linear increase trend and a logarithmical increase trend, respectively. With the increase of initial humidity, both pmax and (dp/dt)max showed a linear decrease trend. These results are useful for understanding the explosion characteristics of fuel-air mixtures under various initial conditions in medium-scale fuel tanks.

Accurate theoretical modeling of cell growth by comparing with visualized data in high-pressure foam injection molding

A novel simulation model has been developed that can predict cell growth tailored to high-pressure foam injection molding (HP-FIM) processes during the entire processing period. This was done together with systematic HP-FIM experiments using a visualization technique. The mathematical model that has been developed is based on the well-known Cell Model to describe the initial bubble growth accurately. To improve the model’s robustness and accuracy for the whole processing period, we used the Simha-Somcynsky equation of state for the PS/CO2 mixture, which facilitated the accurate prediction of realistic transport and rheological properties (that is, gas diffusivity, surface tension, viscosity, and relaxation time) that are changing as a function of the gas content. All of these properties were also a function of the temperature and the pressure in order to accurately capture the behavior of the fluid flow and the transport phenomenon associated with cell growth. By inputting the initial gas concentration and the transient pressure and temperature profiles, the proposed model could predict the cell growth profile under different HP-FIM conditions. The proposed model was validated by comparison with the experimental data obtained from the visualized HP-FIM trials. Reasonable quantitative agreement was achieved between the simulated and measured cell growth throughout the HP-FIM process. Moreover, a sensitivity analysis was conducted by varying the model’s material properties. It was found that an increase in the gas’s diffusivity increased the growth rate of the cell, whereas changes in the surface tension only led to minor changes in the growth profile. Meanwhile, a longer relaxation time promoted the growth rate, whereas a higher zero-shear viscosity restrained growth.

Large Eddy Simulation of Multiple-Stage Ignition Process of n-Heptane Spray Flame

Large eddy simulation of n-heptane spray flames is conducted to investigate the multiple-stage ignition process under extreme (low-temperature, low oxygen, and high-temperature, high-density) conditions. At low oxygen concentrations, the first-stage ignition initiates in the fuel-rich region and then moves to stoichiometric equivalence ratio regions by decreasing the initial temperature. It is also clear that at high temperatures, high oxygen concentrations, or high densities, the reactivity of the mixture is enhanced, where high values of progress variable are observed. Analysis of key intermediate species, including acetylene (C2H2), formaldehyde (CH2O), and hydroxyl (OH) in the mixture fraction and temperature space provides valuable insights into the complex combustion process of the n-heptane spray flames under different initial conditions. The results also suggest that C2H2 appears over a wider range in the mixture fraction space at higher temperature or oxygen concentration condition, implying that it mainly forms at the fuel-rich regions. The initial oxygen concentration of the ambient gas has great influence on the formation and oxidization of C2H2, and the maximum temperature depends on the initial oxygen concentration. OH is mainly formed at the stoichiometric equivalence ratio region, which moves to high-temperature regions very quickly especially at higher oxygen concentrations. Finally, analysis of the premixed and nonpremixed combustion regimes in n-heptane spray flames is also conducted, and both premixed and nonpremixed combustion coexist in spray flames.

Independent testing of Sparklike Laser™ – Non‐destructive insulating glass gas fill analyser

ABSTRACTA common insulating enhancement in modern insulating glass (IG) unit is filling it with argon or krypton gas. Insulating glass units (IGU) have higher and higher performance needs, and the requirements in insulating gas (IG) market are growing all the time. The challenges are confirming the correct filling degree and ensuring that the initial gas concentration will remain inside the insulating glass unit (IGU). Different markets have different standards for gas concentration, but usually the gas content needs to meet or exceed 90 % with a margin. Although invasive methods have their advantages, insulating glass industry specialist are looking for new ways to analyze the insulating gas fill. Traditionally gas concentration has been measured with a gas chromatograph, an invasive test device to analyse gas concentration within double and triple glazed insulating glass units. However, Sparklike Oy is the developer and manufacturer of Sparklike Laser™ devices, that allow non‐destructive insulating gas fill analysis for double and triple glazed insulating glass units, even through most coatings and laminated glasses. Sparklike Laser™ devices are based on technology known as TDLAS (Tuneable Diode Laser Absorption Spectroscopy). By using this technology, the device measures oxygen and from there, the amount of argon, krypton or other insulating gas can be calculated. Sparklike Oy requested a well‐known test laboratory to perform a test in order to determine the argon gas concentration in insulating glass units by using a particularly challenging test specimen. This test specimen included samples with different constructions i.e. clear glass, strengthened glass and laminated glass with different coatings. The purpose of the test was to verify the results from measurements done with Sparklike Laser Standard™ analyzer, by using gas chromatograph as a reference device. In order to receive reliable results, Sparklike provided 12 pieces of test glasses (350 × 350 mm) purchased from a Finnish CE marked glass manufacturer producing insulating glass units according to EN 1279‐5 standard (evaluation of conformity).

Laminar combustion regimes for hybrid mixtures of coal dust with methane gas below the gas lower flammability limit

Understanding flame propagation in dust clouds and hybrid mixtures requires knowledge of the fundamental combustion processes and their coupling interaction. The objective of this work is to use computational fluid dynamics to classify laminar flame structure in hybrid mixtures where the initial gas concentration is below the lower flammability limit. Particular focus is given to the role of reaction chemistry and overall equivalence ratio on flame structure and burning velocity. Through this study, five flame regimes were determined: fuel-lean flames (Type I), volatile-lean flames (Type II), volatile-rich flames (Type III), transition flames (Type IV), and kinetic-limited flames (Type V). Gas-phase chemistry was found to play a critical role in burning velocity for Type III, IV, and V flames. Burning velocities at hybrid volatile component equivalence ratios less than 0.9, were found to be less sensitive to reaction kinetics. Further research using this model will focus on initial gas concentrations above the lower flammability limit, exploring the flammability limits of hybrid mixtures, and extending the results to turbulent flames in system geometries relevant to industrial safety.

Experimental Study on Influence of Ignition Energy on Gas Explosion Reaction Characteristics

Based on both the theoretical analysis and laboratory test, the influence of ignition energy on the parameters such as gas explosion pressure and ignition delay time etc. was studied in this paper. The research results show that ignition energy is linearly proportional to the gas explosion pressure and pressure increase rate; the ignition energy in the 0.1-1J range has the greatest impact on the gas explosion pressure and pressure growth rate, and in the 10-100J it is the smallest. The methane explosion of gas is essentially a process in which the C-H chemical bond breaks to form the free radical, and this process requires a lot of energy. The greater the ignition energy, the more free radicals generated by the C-H breakage and the more complete the explosion reaction, which further allows the gas explosion to be completed in a shorter time. Besides, the greater the ignition energy, the larger the heated area of ??the gas, the more gas will participate in the explosion at the same time, and then the ignition delay time of the gas explosion will be smaller. With the initial concentration of gas 10% as the optimal concentration, the delay time at the time of explosion is 37ms at the minimum, the explosion pressure can reach a maximum value of 0.713MPa, and the increase rate of explosion pressure is a maximum of 17.1MPa/s.

Improving the permeability of coal seam with pulsating hydraulic fracturing technique: A case study in Changping coal mine, China

Abstract To improve the gas permeability of coal seams, industrial experiments of pulsating hydraulic fracturing (PHF) were carried out, and physical properties, including the reasonable fracture radius, gas extraction concentration, water content, permeability, pore and mineral composition of a coal seam, were investigated. The results show that the pulsating peak pressure is the main influencing factor of the fracturing radius, and the free surfaces of the fractured holes and guide holes can realize the directional penetration of the fractured area in the coal seam. The initial gas concentration of the fractured holes and the guide holes are 1.2–1.8 times and 1.5–2.2 times that of the ordinary hole, respectively. The gas concentration decreases with time, and the decay phase of the ordinary hole is approximately 14 days after fracturing, while the fractured holes and guide holes are 38 days and 34 days, and the gas concentrations are stable at 40% and 50%, respectively. The water content is approximately 2%, which is only 1.1 times that of the original coal seam. At the same time, the permeability coefficient of the coal seam increases by 48–217 times. Due to the erosion of pulsating water, the mineral crystals embedded in the coal are transported to the surface to form an erosion hole, which leads to improving the gas permeability of the coal seam by PHF.

Improved model for gas migration velocity of stagnant non-Newtonian fluids in annulus

Currently, analysis of the Sustained Casing Pressure (SCP) tests or other gas migration problems in the wellbore is limited because the mathematical models employed by most researchers are based on Newtonian fluids, which is not consistent with the actual situation that the mud is non-Newtonian fluid in the Annulus. To ensure the operators a realistic and accurate diagnostic test, the improvement of current gas-migration models is of great significance. In this study, a new model of gas migration in non-Newtonian power law fluids was established. This new model incorporates the correlation between swarm bubbles velocity and drag coefficient, and combines the petroleum correlations and the drift-flux model to determine the friction pressure gradient. In addition, the gas slip velocity in non-Newtonian power law fluids is rigorously determined by the proposed calculation procedure using an iteration approach. Furthermore, improvements of the new model are analyzed and discussed in details. During the process of the hypothetical parameters determination (Initial gas chamber length, initial gas concentration in liquid column, mud compressibility, cement permeability, and formation pressure) for simulation, the same values of parameters with previous study are tried to be utilized to minimize the difference. Results in this work indicate that the big discrepancy of matched parameters between the new model and previous model are generated from the mud compressibility, which is attributed to the gas holdup. The higher gas holdup obtained from the new model manifest the validity of proposed model, which is caused by the higher viscosity of non-Newtonian power law fluids. The new model is suitable for relatively low gas holdup (α<0.25), where the bubble flow prevails in annuli. This work provides significant and necessary improvements for gas migration. For the first time, the problem of multi-phase flow in the SCP problem is accomplished by introducing calculation approach of non-Newtonian fluids. This calculation approach can be extended to calculations of other multiphase flow problems in the wellbore.

Effect of water temperature and pH on the concentration and time of ozone saturation

Abstract Ozone has been used for many years to disinfect water due to its oxidizing potential. Since it decomposes quickly into molecular oxygen, leaving no residue, it has important advantages for use. The decomposition of ozone is affected by the temperature and pH of the medium, low pH values and temperatures increasing its half-life, which can result in more efficient disinfection. With the objective of increasing the effectiveness of ozonation, this study investigated the effect of temperature (8 ºC and 25 °C) and pH (3.0 and 6.0) of the water on the saturation time and gas concentration, employing two initial gas concentrations (13.3 and 22.3 mg L-1). The concentration of ozone saturation increased as the temperature and pH of the medium decreased, as also with the higher initial gas concentration ( C0). The highest saturation concentrations were obtained at pH 3.0 and 8 °C (4.50 and 8.03 mg L-1 with C0 of 13.3 and 22.3 mg L-1, respectively). This higher ozone content could result in greater decontamination efficiency of the food products washed with this water.

Advanced oxidation technology for H2S odor gas using non-thermal plasma

Non-thermal plasma technology is a new type of odor treatment processing. We deal with H2S from waste gas emission using non-thermal plasma generated by dielectric barrier discharge. On the basis of two criteria, removal efficiency and absolute removal amount, we deeply investigate the changes in electrical parameters and process parameters, and the reaction process of the influence of ozone on H2S gas removal. The experimental results show that H2S removal efficiency is proportional to the voltage, frequency, power, residence time and energy efficiency, while it is inversely proportional to the initial concentration of H2S gas, and ozone concentration. This study lays the foundations of non-thermal plasma technology for further commercial application.

Experimental Study on In-Situ Decomposition of VOCs Using Microwave-Induced Metal Discharge

In recent years, haze has become a critical environmental issue. As a crucial precursor of haze, volatile organic compounds (VOCs) have become a major research focus. In this study, microwave-induced metal discharge was developed for VOC decomposition. Toluene was used as the VOC model compound. Four types of metal strips were investigated for their decomposition efficiency of toluene using a microwave-induced metal discharge process. All discharges, regardless of the metal type, achieved a high decomposition efficiency of toluene [> 60% (mol/mol)]. In addition, the effects of reaction conditions such as metal strip weight, gas flow rate, microwave power, and gas initial concentration were studied to investigate the decomposition efficiency. The reaction conditions were optimized following a multi-factor orthogonal experiment. The weight of the metal strips and gas flow rate had greater impacts on the decomposition efficiency, whereas the microwave power had a moderate impact. The major reaction products were CO2, CO, O3 and H2O. Both hydroxyl radicals and active oxygen atoms were very important for toluene oxidation. This study offers an important reference for the development of new technology to support the decomposition of VOCs.

Synthesis and Characterization of Co-Doped Brookite Titania Photocatalysts with High Photocatalytic Activity

Transition metal-doping could effectively extend the light response range of TiO2 photocatalysts from the ultraviolet (UV) to the visible region. Co-doped brookite titanium dioxide (Co–TiO2) photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant. The prepared Co–TiO2 photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The photocatalytic activities of Co–TiO2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol (IPA), a typical volatile organic compound (VOC), under visible light. The influences of different Co doping rates, initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied. At the same time, the enhancement mechanism of cobalt ions as a trap for photogenerated holes was discussed. Thus, we found the optimum doping rate, initial concentration of IPA gas and amount of photocatalyst to add. The results show that the mesoporous Co–TiO2 photocatalysts possess smaller size particles, larger specific surface area, lower forbidden bandgap energy (Eg) and better photocatalytic activity than pure brookite TiO2. When the doping of Co was 7% by mass, the initial concentration of IPA gas was 1.0 × 10−6 mol/L and the addition of Co–TiO2 photocatalysts was 50 mg, the best photocatalytic activity was achieved. Furthermore, the degradation rate of IPA was up to 91%, which shows great potential for waste water treatment.

Current Scenario of Gas Scavenging Systems Used in Active Packaging - A Review

Due to the rise of customer’s alertness about fresh foods to health, in the past few years, the consumption of fresh food has increased sturdily. The use of gas scavengers is the most appropriate packaging technologies for fresh, fresh-cut produces and in ready to eat products. The gas absorber/scavenger has ability to protect or stabilize the wanted properties and shelf life of food. The success of gas absorbers in food depends on many parameters such as types of foods, storage temperature, relative humidity, initial gas concentration, and the characteristics of package materials. In this review article, we focus on the most recent research trends in gas scavenging systems used in food packaging, future trends. Intense research from industry and engineers remains important to the development of gas scavenging package that fulfill consumer requirements, enhance product quality, and offer environmentally friendly design and cost-effective application.

Perlakuan Pascapanen Buah Kesemek Reundeu (Diosphyros kaki L.) Menggunakan Gas Karbon Dioksida

Postharvest treatment for removing astringency on Reundeu persimmon by traditional way, make the appearance is not attractive visually for commercial purpose. One of the alternative treatment that potentially to be applied is the high concentration of CO2 gas from dry ice. Application of deastringency treatment aimed to analyze the effectiveness of CO2 gas for reducing tannin content on Reundeu persimmon. Fruits were put into closed jar with dry ice at dose 10, 20, and 30 g and control at ambient temperature. Treatments set for 24, 48, and 72 hours. Measurement of initial concentration of CO2 gas in the jar was carried out after dry ice sublimed. Final concentration of CO2 was measured at the end of treatment and accompanied with analyze of tannin content. The result showed that high concentration of CO2 gas (&gt;80%) can reduce tannin on Reundeu persimmon effectively. Based on minimum human perception, the treatment of CO2 gas as deastringency can be applied at three maturity levels, i.e. 10 g doses at 24 hours for green stage (0.097%), 10 g doses at 48 hours for greenmature stage (0.054%) and 10 g doses at 72 hours for orange-ripe stage (0.02%). This result can be use as a reference for distribution handling of persimmon fruit to fulfill the consumers and markets demands.Keywords: carbon dioxide gas, deastringency treatment, dry ice, persimmon, tannin

One-Dimensional Analysis of Gas Diffusion-Induced Cassie to Wenzel State Transition

We develop a one-dimensional model for transient diffusion of gas between ridges into a quiescent liquid suspended in the Cassie state above them. In the first case study, we assume that the liquid and gas are initially at the same pressure and that the liquid column is sealed at the top. In the second one, we assume that the gas initially undergoes isothermal compression and that the liquid column is exposed to gas at the top. Our model provides a framework to compute the transient gas concentration field in the liquid, the time when the triple contact line begins to move down the ridges, and the time when menisci reach the bottom of the substrate compromising the Cassie state. At illustrative conditions, we show the effects of geometry, hydrostatic pressure, and initial gas concentration on the Cassie to Wenzel state transition.

Effects of solute concentration in liquid on pore shape in solid

The effects of initial solute gas concentration in the liquid on the shape of a pore, resulting from a nucleated bubble entrapped by a solidification front, are predicted in this work. Solute concentration in liquid is responsible for solute transfer across the bubble cap, gas pressure in the pore, and shapes of the cap and pore in solid. Distributions and shapes of pores in solids influence not only microstructure of materials, but also contemporary issues of biology, engineering, foods, geophysics and climate change, etc. In this work, the relevant pore shape delineated by tracing contact angle of the cap to a first approximation is determined by accounting for mass and momentum transport across a self-consistent shape of the cap whose surface is satisfied by physico-chemical equilibrium, as proposed previously. This work finds that there exist three different mechanisms for pore formation, depending on directions and magnitude of solute transfer across the cap. Case 1 is subject to solute transport from the pore into surrounding liquid as a result of the cap emerged from a thin concentration boundary layer on the solidification front. An increase in initial solute concentration in liquid decreases pore radius and times for bubble entrapment. Opposite directions of solute transport across the cap submerged into a thick concentration boundary layer along the solidification front, however, cannot result in bubble entrapment, because solute concentration at the cap increases and decreases rapidly in late stage in Cases 2a and 2b, respectively. The predicted pore shape in solid agrees with experimental data. The pore shape therefore can be controlled by initial solute concentration to change directions and magnitudes of solute transport across the cap.

Dynamics of self-compressed argon and helium plasma streams in the MPC facility

The results of experimental investigations on self-compressed plasma streams and compression zone formation are presented for varied mass flow rate and initial concentrations of particles of working gas that depend on initial pressure. Experiments were carried out in the Magnetoplasma Compressor (MPC) facility. Space–time distributions of the electric current and electron density in the plasma stream compression region were measured under different experimental conditions. High-speed images of plasma stream dynamics in the MPC accelerating channel with a high temporal resolution were also obtained for different initial pressures. The experimental results show a strong dependence of plasma stream parameters and compression zone location on the initial gas concentration. The maximum electron density is obtained in the range of Ne = (1 ÷ 5) × 1018 cm−3. Plasma streams have a good radial symmetry under all experimental conditions. The distributions of plasma parameters along the plasma stream flows are discussed.