Gas Blowing Research Articles

Mathematical modeling on the fluid flow during RH degassing process

A mathematical model combining VOF and DPM has been developed to investigate the effect of the lift force and the bubble size on the fluid flow in the RH process. The effect of the type of gas blowing was also discussed. The calculated results were validated against the experimental data from water modeling using a particle image velocimetry technique (PIV). In the current model, the interfacial behavior between the molten steel and the gas phase, and the motion of argon bubbles can be captured and tracked simultaneously. The results indicated that the speed of the molten steel and the recirculation rate increased with increasing the lift force. In order to accurately simulate the fluid flow in the RH process, the optimum lift coefficient was 0.1. However, an inverse tendency was obtained for the bubble size. With the bubble size increasing, the gas volume fraction in the up-leg snorkel changed from a double-peak distribution to a single-peak distribution, which weakened the interaction between the molten steel and gas bubbles and decreased the recirculate rate. To improve the recirculate rate and good stirring, small size gas bubbles should be adopted. In addition, the symmetrical flow of the molten steel in the down-leg snorkel was converted into a rotating flow pattern when increasing gas flow rates in one nozzle or two nozzles. Meanwhile, the recirculate rate decreased and the slag entrainment at the free surface might occur. Therefore, it was of great importance to ensure an equal gas flow rate in each nozzle in actual operations.

Влияние инжекции тяжелого газа в пристеночный слой сверхзвукового пограничного слоя на его переход

Влияние инжекции тяжелого газа в пристеночный слой сверхзвукового пограничного слоя на его переход

Synergistic Separation Behavior of Boron in Metallurgical Grade Silicon Using a Combined Slagging and Gas Blowing Refining Technique

A combined slagging and gas blowing refining technique for boron removal from metallurgical grade silicon using the CaO-SiO2-CaCl2 slag and the mixed Ar-O2-H2O gas is investigated. The oxygen gas blowing in combination with water vapor shows a wonderful removal efficiency of boron compared with the single oxygen or the single water vapor blowing. It is analyzed from the thermodynamics that a synergistic separation behavior of boron is resulted from CaCl2 and O2. Boron is removed and reduced from 22 to 0.75 ppmw with a removal efficiency of 96.6 pct.

Mechanism of boron removal from Si–Al melt by Ar–H2 gas mixtures

A new method about purification of metallurgical grade silicon (MG-Si) by a combination of Si–Al solvent refining and gas blowing treatment was proposed. The morphologies and transformation of impurity phases, especially for boron and iron in Si–Al melt were investigated during Ar–H2 gas blowing treatment. The mechanism of boron removal was discussed. The results indicate that gas blowing can refine grain size and increase nucleation of the primary Si. Boron can be effectively removed from MG-Si using the Ar–H2 gas blowing technique during the Si–Al solvent refining. Compared with the sample without gas blowing, the removal efficiency of boron increases from 45.83% to 74.73% after 2.5 h gas blowing. The main impurity phases containing boron are in the form of TiB2, AlB2 and VB compounds and iron-containing one is in the form of β-Al5FeSi intermetallic compound. Part of boron combines [H] to transform into gas BxHy (BH, BH2) and diffuses towards the surface of the melt and is volatilized by Ar–H2 gas blowing treatment under electromagnetic stirring.

Effects of Gas Blowing Condition on Formation of Perovskite Layer on Organic Scaffolds

We confirmed that the gas blowing condition during perovskite formation is suitable for fabricating large-scale cells composed of a PEDOT:PSS layer as a scaffold. Gas blowing minimized the defects at the interface between the perovskite and PEDOT:PSS and created a flat perovskite layer. The crystallization process by which the perovskite layer grew was different from one-step spin-coating. Gas blowing led to a perovskite layer with orientation along the (310) plane.

The Effects of Bottom Blowing Gas Flow Rate Distribution During the Steelmaking Converter Process on Mixing Efficiency

Featuring the advantages of top-blown and bottom-blown oxygen converters, top and bottom combined blown converters are mainstream devices used in steelmaking converter. This study adopted the FLUENT software to develop a numerical model that simulates 3D multiphase flows of gas (air and argon), liquid steel, and slag. Ten numerical experiments were conducted to analyze the effects that the bottom blowing gas flow rate distribution patterns (uniform, linear fixed total flow rate, linear fixed maximal flow rate, and V-type) and bottom blowing gas flow distribution gradients of combined blown converters exert on slag surface stirring heights, flow field patterns, simulation system dynamic pressures, mixing time, and liquid steel–slag interface velocity. The simulation results indicated that the mixing efficiency was highest for the linear fixed total flow rate, followed by the linear fixed maximal flow rate, V-type, and uniform patterns. The bottom blowing gas flow rate distribution exhibited linear patterns and large gradients, and high bottom blowing total flow rates increased the mixing efficiency substantially. In addition, the results suggested that even when bottom blowing total flow rate was reduced, adopting effective bottom blowing gas flow rate distribution patterns and gradients could improve the mixing efficiency.

ガス吹きつけMVP法によって超高速成膜されたDLCの膜厚分布に及ぼす吹きつけガス入射東の影響

ガス吹きつけMVP法によって超高速成膜されたDLCの膜厚分布に及ぼす吹きつけガス入射東の影響

アンモニアガス吹付けによる溶銑脱錫の基礎検討

アンモニアガス吹付けによる溶銑脱錫の基礎検討

Mathematical Simulation on Slag Entrainment in Bottom-blowing Gas Ladle with Immersed Cylinder

A flow field mathematical model of the molten steel in a 150 t bottom blowing gas ladle has been established. The ladle blowing argon process was simulated by mixture multiphase model. The flow of the liquid steel and the phenomenon of slag entrainment on the surface of the liquid steel in bottom blowing gas ladle with immersed cylinder were studied. On the basis of the effects of the gas flow rate and the way of blowing on the flow state of the top slag and mixing of molten steel, the critical gas flow rate with the immersed cylinder was determined. The results show that the flow distribution of the liquid steel tends to be uniform, the liquid surface velocity decreases, the critical gas flow of slag entrainment increases and the mixing time is shortened in the ladle when an immersed cylinder is applied.

A salting out-acetonitrile homogeneous extraction coupled with gas chromatography–mass spectrometry method for the simultaneous determination of thirteen N-nitrosamines in skin care cosmetics

A sensitive gas chromatography–mass spectrometry method was established for the simultaneous determination of thirteen N-nitrosamines (NAs) in skin care cosmetics. The cosmetics samples were firstly dispersed by water and subsequently extracted and purified using salting out-acetonitrile homogeneous extraction method. Finally, the extracting solution was concentrated by slow nitrogen gas blowing. All of the samples were separated by INNOWAX capillary chromatographic column, and detected by selected ion monitoring (SIM) mode of gas chromatography–mass spectrometry (GC–MS) and quantified by isotope internal standard method. The method was validated for linearity and range, accuracy, precision and sensitivity. Under the optimized condition, the calibration curves were linear over the selected concentration ranges of 2–500μg/L for all the thirteen analytes, with calculated coefficients of determination (R2) of greater than 0.996. The limits of detection (LODs) and the limits of quantitation (LOQs) of the method were 3–15μg/kg and 10–50μg/kg, respectively. Recoveries were calculated at three levels of concentration spiked in two kinds of cosmetics (skin care cream and water). The values were found between 93.8% and 121.0% with relative standard deviation (RSD) values of 2.5–7.2% for intra-day precision (n=6) and 3.3–6.7% for inter-day precision (n=5). The method was successfully applied to analyze twenty-two cosmetics samples and N-nitrosodimethylamine (NDMA) was detected in one sample with the concentration of 207μg/kg.

The Combined Influence Of Heat And Mass Transfer Through A Porous Wall On The Boundary Layer Stability Compressible Gas At High Mach Numbers

This work continues the research on modeling the management regime in the boundary layer of compressible gas. The effect of the distribution of heat and mass transfer on the stability characteristics of supersonic boundary layer at high supersonic Mach number M = 5,35. The focus is on the modeling of acoustic disturbances in the conditions as a normal injection, in which the only nonzero component of the average velocity V, and the injection of other areas, including tangential, when the wall is not zero only U component. Production close to the problem of influence on the development of gas curtain small oscillations. It is assumed that the effect of injection of a homogeneous gas of different temperature similar to that of the blowing gas of different density, namely, blowing cold gas simulates heavy gas blowing and vice versa. Therefore in this modeling work is achieved by changing the factor of temperature (heating or cooling of the walls). The variant when the socalled regime implemented «lock» when the velocity perturbations on the porous surface can be taken as zero.

Growth and gas formation by Lactobacillus wasatchensis, a novel obligatory heterofermentative nonstarter lactic acid bacterium, in Cheddar-style cheese made using a Streptococcus thermophilus starter

A novel slow-growing, obligatory heterofermentative, nonstarter lactic acid bacterium (NSLAB), Lactobacillus wasatchensis WDC04, was studied for growth and gas production in Cheddar-style cheese made using Streptococcus thermophilus as the starter culture. Cheesemaking trials were conducted using S. thermophilus alone or in combination with Lb. wasatchensis deliberately added to cheese milk at a level of ~104 cfu/mL. Resulting cheeses were ripened at 6 or 12°C. At d 1, starter streptococcal numbers were similar in both cheeses (~109 cfu/g) and fast-growing NSLAB lactobacilli counts were below detectable levels (<102 cfu/g). As expected, Lactobacillus wasatchensis counts were 3×105 cfu/g in cheeses inoculated with this bacterium and below enumeration limits in the control cheese. Starter streptococci decreased over time at both storage temperatures but declined more rapidly at 12°C, especially in cheese also containing Lb. wasatchensis. Populations of fast-growing NSLAB and the slow-growing Lb. wasatchensis reached 5×107 and 2×108 cfu/g, respectively, after 16 wk of storage at 12°C. Growth of NSLAB coincided with a reduction in galactose concentration in the cheese from 0.6 to 0.1%. Levels of galactose at 6°C had similar decrease. Gas formation and textural defects were only observed in cheese with added Lb. wasatchensis ripened at 12°C. Use of S. thermophilus as starter culture resulted in galactose accumulation that Lb. wasatchensis can use to produce CO2, which contributes to late gas blowing in Cheddar-style cheeses, especially when the cheese is ripened at elevated temperature.

Development of an air-knife system for highly reproducible fabrication of polydimethylsiloxane microstencils

In this study, an air-knife system was developed for the automated fabrication of polymer microstencils with microscale perforated patterns. Blowing compressed N2 gas through the air knife provided a uniform laminar gas flow of high intensity suitable for perforating holes in the stencil. The polydimethylsiloxane (PDMS) stencil was replicated from a master mold prepared by photolithography. When the prepolymer of PDMS was spin-coated onto the master mold, a thin layer of the prepolymer remained on top of the master's structure and consequently prevented the formation of the perforated patterns. This residual layer was easily removed by the presented air knife. The air-knife system controlled the flow rate of N2 gas and the conveying speed of the master mold; therefore, the system possessed high reproducibility compared to manual gas blowing. Its use reduced the fabrication time for perforated biocompatible polymer microstencils, allowing for their mass production via an automated system. The validity of this suggested method was proven through experiments and was evaluated by application in various fields.

Advanced reduction of Cr(VI) in real chrome-plating wastewater using a VUV photoreactor: Batch and continuous-flow experiments

Performance of a VUV photoreactor was investigated for the reduction of Cr(VI) in real chrome-plating wastewater. The effect of wastewater pH, initial Cr(VI) concentration, organic reductant, air/N2 gas blowing and reaction time was investigated for a decrease Cr(VI) in batch experiments. The decrease in Cr(VI) was examined using a VUV photoreactor in continuous-flow mode as a function of hydraulic retention time (HRT). Maximum photoreduction of Cr(VI) obtained in batch tests at acidic pH of 1.8 with N2 blowing. The presence of methanol accelerated reduction of Cr(VI). Cr(VI) at initial concentrations of 10, 20, 30, 50 and 100mg/L was reduced completely in the batch VUV photoreactor at reaction times of 2, 10, 12, 16 and 25min, respectively. The VUV photoreactor also operated in continuous-flow mode, where 91.7% of 30mg/L Cr(VI) reduced in a HRT of 6min. The VUV photoreactor is an efficient and practicable technology for reduction of Cr(VI) to treat Cr(VI)-laden streams.

Improving performances of microchannels in microfluidic chip using solidifiable adhesive film

In order to improve surface roughness and hydrophilicity of microchannels in microfluidic chip, then to achieve high fluid speed under small pressure, a technology named as coating solidifiable adhesive film is proposed. In this paper the microfluidic chip is manufactured using CO2 laser. The film is coated on inside wall of microchannels using ultraviolet optic solidifiable adhesive. Two coating methods were used to synthesise the NOA61 film. The surface roughness and water-phase contact angle of the microchannel with and without the NOA61 film are measured. The roughness is reduced from 2 μm to 243·36 nm and the contact angle is reduced from 100 to 72·55°, when NOA61 film is coated with the action of gas blowing and consequent drying by UV light. The roughness is reduced from 2 μm to 60·49 nm and the contact angle is reduced from 100 to 55·35°, when NOA61 film is obtained by gravity flow.

Film cooling effectiveness with injection through circular holes embedded in a transverse trench

Results of a numerical study of the thermal effectiveness of a gas wall screen implemented via gas blowing through cylindrical inclined holes embedded in a transverse trench are reported. The calculations were performed using 3D Reynolds-averaged Navier–Stokes equations, with the flow turbulence being modeled by means of the Reynolds-stress model. Blowing into the trench was compared to the conventional cooling technique using gas blowing without a trench. The film cooling effectiveness with gas injection through circular holes embedded in trench exceeds significantly the effectiveness of blowing without a trench. Such a method of coolant supply into the flow proved to be especially advantageous at high blowing ratios. Due to the formation of vortical structures inside the trench, a more uniform cooling flow in the spanwise direction can be achieved. A comparative analysis is indicative of acceptable qualitative agreement of the experimental and predicted data.

BASIC OXYGEN CONVERTER PROCESS WITH PULSATING TOP AND BOTTOM BLOWING

The article considers the peculiarities of the steel refining processes in top and bottom blown converter. Converter operation technology perfection and thermal balance improvement problems are discussed. The authors proposed two out-look versions of control actions: pre-assigned amplitude-frequency characteristics of pulsating gas jets in steelmaking with gas blowing and waste gases post combustion just above metal surface for effective chemical reaction heat transfer. Special blast designs are proposed for implementation of these assignments.

절단배추의 선도유지를 위한 절단 공정 개선

To maintain the freshness and to prevent browning of cut Kimchi cabbages, the effect of the cutting process using a ceramic knife under N2 blowing on the quality of the cut Kimchi cabbages was investigated. Kimchi cabbages cut with a ceramic knife under N2 gas blowing conditions (NC) were stored at 5°C for 7 days, and their weight reduction ratio and the browning degree and appearance were compared with those of the control treatment samples (OS; cut with a stainless steel knife under normal air, OC; cut with a ceramic knife under normal air). The weight reduction ratios were 0.07~0.13%, and the NC treatment showed the lowest reduction ratio among all the treatments (p&lt;0.05). The Hunter L values increased, but the a and b values decreased after 5-day storage in all the treatments. The NC treatment had higher L values but lower a and b values than the OS and OC treatments. The browning degrees by Hunter color value, PPO activity, and appearances were the least in the NC treatment (p&lt;0.05). The cutting process with a ceramic knife under N2 blowing could be applied to the cutting of vegetable products and for minimal fruit processing.

Tube bulge forming for one-piece fabrication of multi-joint head tubes for Ti-alloy-body bicycles

The tube bulge forming process is a very effective means to manufacture a complex part as one piece, without the need for additional processes, such as welding and joining. Since one-piece components can endure higher applied loads, they should be considered in the design and manufacture of structural parts. The head tube of a bicycle is one such example, being a four-directional multi-joint component that is also subjected to the highest external load of all bicycle parts. A head tube is therefore ideally fabricated as a singular piece using a suitable process such as tube bulge forming. Commercial Ti-3Al-2.5V alloy tube was selected for this study, as it represents a standard material for Ti-alloy-body bicycles. Finite element simulation is used to predict defects resulting from inappropriate gas blowing conditions and to calculate the optimum forming conditions. Based on the results of finite element analysis and practical experiment, an optimized pressure curve for the bulging of a bicycle head tube is proposed. The effect of microstructural change by deformation is also investigated to predict possible defects in the large-scale deformation of bulged head tubes.

Lattice-Boltzmann method applied to the pattern formation on periodic surface structures generated by multiline nanosecond laser

We simulated the pattern formation on silicon surfaces. For this purpose, we used Lattice-Boltzmann method assuming two non-ideal interacting fluids using a lattice velocity D2Q9. The experiment was carried out with a multiline (1064, 532 and 355 nm) Nd: YAG pulsed laser that employs an energy range from 310 to 3100 J on a surface p-type monocrystalline silicon oriented in the direction [111]. The whole system was subjected to argon gas blowing which is key in pattern formation. Computer simulation reproduces the overall behavior of the experimental geometric patterns expressed in oblique parallel ripples quite well.