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In this paper, we present a cost-effective system for monitoring and controlling alkaline electrolyzers, intending to improve hydrogen gas production on a laboratory scale. Our work includes two main innovations. Firstly, we suggest an approach to calibrate a standard air flow meter to accurately measure the flow of hydrogen-rich gas from electrolyzers, improving measurement accuracy while keeping costs low. Secondly, we introduce a unique cascade control method to manage hydrogen-rich gas production in the electrolyzer, ensuring precise control over gas flow rates. By combining affordable, energy-efficient devices with a PI control system, we achieve efficient gas production through electrolysis, replacing manual control approaches. Experimental results confirm the effectiveness of our cascade control method, demonstrating stable operation with minimal errors. These results provide a foundation for further research into control strategies to enhance the performance of electrolytic cells. [ABSTRACT FROM AUTHOR]

Metallic microfluidic devices made from powder-bed additive manufacturing systems have received increasing attention, but their feasible channel geometry and complexity are often limited by lack of an effective approach to removing trapped powder particles within the channels or conduits of the sintered parts. Here, we present an innovative approach to fabricating long serpentine, high-aspect-ratio submillimeter channels made of stainless steel 316L (SS) by binder jet printing (BJP) and liquid-phase sintering. We leverage the unique nature of the BJP process, that is printing and consolidation steps are decoupled, enabling us to join two or more parts during the sintering step. Instead of constructing the channel device as a single part, we print multiple parts for easy powder removal and later join them to form enclosed channels. The key innovation lies in adding sintering additives like boron nitrides (BN) to the SS stock powder—at the SS/BN interfaces, liquid phase is locally generated at temperature much lower than the SS melting temperature, facilitating the bonding of the multiple parts as well as the consolidation of parts for near-full density. We systematically vary the sintering temperature to show how it affects the joining quality and the channel shape distortion. The joining quality such as the fracture strengths of the joined samples is measured by a pull test while the shape distortion is characterized by various imaging techniques. The feasibility of the proposed approach is demonstrated by fabricating a 400-mm-long, fully enclosed serpentine channel with a rectangular cross-section of 0.5 mm in width and 1.8 mm in height. The pressure drop across this 3D-printed SS serpentine channels is measured for air flow and compared to a standard gas flow model, showing that the device is free of leakage or clogs. [ABSTRACT FROM AUTHOR]

Through composite dry separation, effective precipitation and impurity removal can be achieved, improving the quality of raw coal. This paper mainly systematically analyzes the synergistic control mechanisms of airflow velocity, airflow transition layer height and control angle on the upgrading characteristics of moist coal. The results show that Zone I is a high airflow area, and when v = 2.12 m/s, it can effectively destroy the original static stable structure of low-density particles, increase the degree of freedom of particle accumulation volume, and achieve effective precipitation of particles. Zone II is a medium air volume area, and when v = 1.78 m/s, the high-density particle group in this area has the weakest obstruction effect on airflow, which can achieve efficient particle precipitation. Zone III is a low airflow area, where the dispersion of high-density particle groups increases at v = 1.36 m/s. The airflow can effectively act on the particles through the bed layer, reducing their surface water. When the height (H) of the gas transition layer is 49-52 mm and the regulatory perspective is 20–25, the distribution uniformity of the gas flow in the bed is the best. After separation and upgrading, the moist coal concentrate yield is 78.3%, ash content is 10.05%, as well as the possible deviation E value is 0.1 g/cm3. [ABSTRACT FROM AUTHOR]

An airlift pump is a vertical tube that utilizes the buoyant effects of a gas to lift a liquid. Unlike a standard mechanical pump, the liquid flow rate through the airlift pump is not directly controlled; rather, it depends on the supplied gas flow rate, the tube length and diameter, and the relative height of the liquid supply free surface (submergence ratio). The present study uses the commercial CFD code ANSYS CFX to model the isothermal, 3D, transient flow in an airlift pump using water and air. The model applies pressure boundary conditions at both ends of the tube and specifies the mass flow rate of air through multiple openings in the side of the tube. The bottom of the tube is an inlet of water only and the outlet is a two-phase flow opening. A time-dependent, homogeneous, VOF two-phase RANS CFD modelling approach is used with the air treated as an ideal gas. This work found that a complete 3D domain was necessary for consistent prediction of the airlift performance and physically realistic two-phase flow structures. Statistical analysis of the two-phase flow structures was applied to characterize airlift pump instability and better understand the physics of the airlift pump. [ABSTRACT FROM AUTHOR]

The multi-stage water spray cooling system of the space launch site involves a complex gas–liquid two-phase mixed cooling problem in the process of spraying water onto the rocket engine gas jet. To investigate the complex multiphase flow field of the interaction between the airflow and liquid water jet, the Mixture multiphase flow model is adopted, which is coupled with the vaporization equation and component transport model of liquid water. The computational fluid dynamics method is used to numerically analyze the mixing and cooling mechanism of low-temperature liquid jet in high-temperature and high-speed gas flow. The results show that mixing low-temperature liquid jets in high-temperature and high-speed airflow can cause the exchange of momentum and energy, resulting in pressure loss and temperature reduction in the gas phase flow field. Due to the acceleration of transverse airflow, the diffusion flow range of the jet is significantly increased, and violent vaporization occurs, which further consume a large amount of airflow energy. The mixing cooling effect of transverse airflow and liquid water jet is directly related to the mass flow rate ratio of the jet to airflow. In addition, directly designing liquid water jet orifices on the solid wall of the guiding device can achieve the effect of improving the gas flow field environment. This conclusion can provide theoretical reference for the thermal protection design of ground launch devices in space launch site. [ABSTRACT FROM AUTHOR]

For shallow buried mines, the cracks generated due to the mining activities will connect the surface ground and the working face through the gob, which may result in the gas exchange between the surface and underground. In this study, we proposed the gob gas flow model and verified its applicability based on the measured data on site in our previous research and discussed the effect of delay time of pressure variation between working face and surface ground on the airflow direction according to the simulation. The results suggest that the delay time of pressure variation is the main factor affecting the pressure difference between surface and working face and airflow direction. Due to the characteristics of the surface pressure changes, the effect of delay time on airflow in gob is small in a short time, but this effect gradually increases with time. According to the airflow law in a cycle of pressure variation, the airflow direction in the gob is predictable when the delay time reaches a certain value, which can be interpreted clearly on the surface pressure variation diagram. This research may provide references for the measures taken against mine disasters caused by different airflow directions. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

[Display omitted] • The void fraction (41.31%) formed by large-particle size gravel was rapidly reduced. • High rate of gas flow in the pipeline made landfill gas diluted rapidly. • A larger void fraction (44.62%) led to formation of a smaller anaerobic zone. The main disposal method for municipal solid waste (MSW), including the growing worldwide volumes of kitchen waste, involves transport to landfills. Because kitchen waste is mainly composed of organic matter and has a high moisture content, large amounts of leachate and landfill gas are generated when it is sent to landfills. Therefore, rapid waste stabilization is essential. In this study, four semi-aerobic bioreactors (named NS, SS, MS, and LS) were established with void fractions of 33.76%, 39.84%, 44.62%, and 41.31%, respectively. The results showed that the void fractions of landfill directly affected the gas flow path. When the landfill void fraction was small (e.g., NS), most airflow traveled directly through the pipeline and minimal airflow entered the waste layer. When the landfill void fraction was large (e.g., MS), air easily entered the waste layer and some air flowed into the gas vent with the landfill gas. As the reaction proceeded, the void fraction gradually decreased due to gravity-induced sedimentation. During the water addition experiment, the voids were occupied by water, leading to formation of an anaerobic area. Among the four bioreactors, only MS had negligible formation of an anaerobic zone in the center. Methane (CH 4) generation was detected only at the connection between the gas vent and the leachate collection pipe. A larger void fraction led to formation of a smaller anaerobic zone. The ratio of air flowing in pipeline was lowest in MS. These results indicated that a large void fraction promotes the decomposition of organic matter. [ABSTRACT FROM AUTHOR]

Vegetable precision planting agronomy is suitable for my country's current vegetable planting system, and the air-suction vegetable precision planter is currently the most important work tool in my country. This paper designs a kind of air-absorbing vegetable precision sower for the problems of small vegetable seeds with small grains, poor mobility and high difficulty in achieving uniform sowing of small seeds. First, Fluent software is used to simulate and analyze the flow field of the air chamber in the seed metering device, and the pressure and velocity of the fluid in the air chamber are analyzed. Through the comparison of the pressure distribution cloud chart and the velocity distribution cloud chart, the influence of different apertures, holes, vacuum degree, and gas chamber depth on the flow field of the gas chamber is analyzed. The air suction seed discharger test bench was set up and orthogonal test was carried out, and the test results showed that the optimal parameter combination was 3.5 kPa vacuum degree of the air chamber, 2.4 mm diameter of the type hole, and 18 r/min rotational speed of the seed discharging disk. The high-speed photographic test was carried out under the optimal parameter combination, and the results showed that leakage of suction, adsorption of 1 seed, and adsorption of multiple seeds appeared in the process of suction, and it is important for the development of the air suction precision machine for small seeded vegetables with better performance. The results showed that the phenomenon of leakage, adsorption of 1 seed and adsorption of multiple seeds occurred in the process of seed suction, which provided a reference basis for the development of a better performance of the air-absorption precision planter for small seeds. [ABSTRACT FROM AUTHOR]

This study investigated the efficacy of the full transverse exhaust method for smoke extraction in tunnel fires. It examines factors such as the number and layout of air supply and exhaust outlets, analyzing their impact on smoke spread, tunnel temperature, visibility, and airflow. The results demonstrate that the full transverse exhaust method effectively controls smoke emissions in raised highway tunnels. It limits smoke spread, reduces tunnel temperature, and effectively controls the fire‐affected area. The number and layout of outlets significantly influence smoke dispersion, with fewer exhaust outlets providing better smoke control and optimizing the tunnel environment. However, insufficient outlets disrupt gas flow stability. The position of exhaust outlets affects smoke distribution, and caution is advised to prevent directing fresh air flow toward the fire. Opening an equal number of exhaust outlets on one side of the fire source yields superior smoke extraction results, reducing tunnel ceiling temperatures and minimizing risks to personnel and structures. Though stabilization may take longer, this configuration proves advantageous. The study offers valuable insights and practical guidelines for implementing the full transverse smoke control method in real‐world scenarios. [ABSTRACT FROM AUTHOR]

In this paper, the main characteristics and principles of the bubble-cap distributor which widely used in the second stage gas phase hydrogenation of gasoline are analyzed. At the same time, the single test and combination test of the bubble-cap distributor are carried out respectively. The uneven distribution coefficient and pressure drop are used as performance evaluation indexes to explore its gas phase distribution characteristics. The experimental results show that the distribution performance of bubble-cap distributor is not affected by the air volume. Increasing the air flow rate can not improve the gas phase distribution performance, but increases the flow resistance and the pressure drop. And due to structural reasons, the gas phase after flowing out of the central tube is basically concentrated under the central tube, with a small diffusion range, and the cooperation is not formed. According to the performance and energy saving analysis, the bubble cap structure distributor is not the best structure as a gas phase distributor. Therefore, without affecting the distribution characteristics, the new gas phase distributor should adopt a non-bubble cap structure, thus greatly reducing the gas phase flow resistance. In addition, the distribution performance of the unit and the interaction between the adjacent units should be considered, and the distribution area should be expanded as much as possible. The homogenized combined flow field can improve the safety and stability of the internals during operation. [ABSTRACT FROM AUTHOR]

Open in new tab Download slide OBJECTIVES To evaluate the safety and feasibility of removing drainage tubes at larger size of air leak in patients with prolonged air leak after pulmonary surgery. METHODS Ninety-five patients who underwent pulmonary surgery with prolonged air leak in our centre were enrolled in this randomized controlled, single-centre, non-inferiority study. The drainage tube was clamped with a stable size of air leak observed over the last 6 h, which was quantified by gas flow rate using the digital drainage system. The control group (n  = 48) and the study group (n  = 46) had their drainage tube clamped at 0–20 ml/min and 60–80 ml/min, respectively. We continuously monitored clinical symptoms, conducted imaging and laboratory examinations, and decided whether to reopen the drainage tube. RESULTS The reopening rate in the study group was not lower than that in the control group (2.08% vs 6.52%, P  > 0.05). The absolute difference in reopening rate was 4.44% (95% confidence interval –0.038 to 0.126), with an upper limit of 12.6% below the non-inferiority margin (15%). There were significant differences in the length of stay [16.5 (13–24.75) vs 13.5 (12–19.25), P  = 0.017] and the duration of drainage [12 (9.25–18.50) vs 10 (8–12.25), P  = 0.007] between the control and study groups. No notable differences were observed in chest X-ray results 14 days after discharge or in the readmission rate. CONCLUSIONS For patients with prolonged air leak, removing drainage tubes at larger size of air leak demonstrated similar safety compared to smaller size of air leak, and can shorten both length of stay and drainage duration. Clinical trial registration number Name of registry: Gas flow threshold for safe removal of chest drainage in patients with alveolar-pleural fistula prolonged air leak after pulmonary surgery. Registration number: ChiCTR2200067120. URL: https://www.chictr.org.cn/ [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The setting machine exhaust gas contains a large number of fiber particles and micro oil droplets, which are adhesive and flammable. This leads to difficulties in waste heat recovery of the exhaust gas. In this article, numerical and experimental studies of a non-uniform plate heat exchanger with dimples/protrusions for waste heat recovery of setting machines are carried out. Based on the three-dimensional fluid-thermal-structural coupling method, the regenerative process between gas and air are investigated numerically with low Reynolds number turbulence model. The effect of the structural parameters (protrusions diameters, protrusions spacing and plate spacing) and operation parameters (air inlet temperature, gas and air flow rate) on the heat transfer performance are discussed. The multi-objective optimization of the plate regenerator is conducted by Box-Behnken Design and Nondominated Sorting Genetic Algorithm II to maximize the thermal performance coefficient and minimize entransy dissipation number. It is found that when D1, H1 S1, D2, H2, S2 are 9 mm, 7 mm, 161 mm, 9 mm, 8 mm and 153 mm respectively, the heat exchanger has the best heat transfer performance. Compared with the original model, the heat transfer rate of the optimized heat exchanger is increased by 3.9%, the thermal performance coefficient of the air side and flue gas side is increased by 5.7% and 5.9% respectively, and the entransy dissipation number is reduced by 24.6%. [ABSTRACT FROM AUTHOR]

This study demonstrates the applicability of an explicit model predictive controller (ExMPC) to the air mass flow control in a fuel cell electric vehicle. The two control tasks comprise the supply of air to the fuel cell stack for the electrochemical reaction as well as the dilution of hydrogen in the outlet gas flow of the cathode subsystem. With the aim of achieving zero control deviation for steady states, the linear model in the state observer is extended with two perturbations. During the experimental validation of the proposed controller, fast dynamics are achieved with the ExMPC, which generally exploits the limits of the control variables. After the calibration of the ExMPC, the final comparison to a set of reference PI controllers reveals a significant improvement in the closed-loop behavior of the cathode subsystem during step changes in the controller setpoints. • An explicit model predictive controller is applied to a fuel cell electric vehicle. • Delays for control and controlled variables are considered. • The operating limits of the control variables are exploited during dynamic operation. • Improved closed-loop behavior is achieved in comparison to reference PI controllers. [ABSTRACT FROM AUTHOR]

Regarding the gas disaster caused by the complex ventilation system and the changeable flow field in the combined goaf during the transition period of the coal pillar-free working face, the self-designed physical simulation test bench for the combined goaf of coal pillar-free mining was used to compare and analyze the distribution law of wind pressure, gas, and oxygen concentration field in the combined goaf during the moving period of the working face and the normal mining period. The results show that during the relocation period, the gas concentration in the stope will always be slightly higher than that in the normal mining period, and the existing air leakage channel will lead to complex air flow in the combined goaf, which is easy to cause gas explosion accidents. The formation conditions, judgment principles, and judgment methods of the dangerous area of gas explosion coupling disaster in goaf are analyzed. By changing the air distribution ratio of the main and auxiliary air intake roadways, it is concluded that the explosion area will form an "L"-shaped explosion zone in the goaf, and the area of gas explosion disaster area during the relocation period will be larger than that the normal mining period. According to the size of the gas explosion area, the optimal air distribution ratio of the main and auxiliary air intake roadway during the transition period of the working face relocation and the normal mining period is 2:1. Under this air distribution ratio, the gas explosion area is the smallest, which is 132 284 and 113 534 mm2, respectively. The research results are of great significance to reveal the mechanism of gas disaster induced by goaf during the transition period of coal pillar-free relocation. [ABSTRACT FROM AUTHOR]

Top-submerged nozzles with lateral holes find applications as passive mixing devices in radiochemical/hazardous industries. We report the mechanism of bubble formation and detachment at a lateral hole in such a nozzle for the first time. Three distinct phases – a growth phase, an elongation phase and finally a rise/detachment phase – could be observed during bubble formation. Effect of gas flow rate, diameter of lateral hole (1, 2 and 3 mm) and physical properties of liquid-liquid system on bubble detachment time and bubble equivalent diameter are reported. Three different liquid-liquid systems (DM water, 2 N and 4 N nitric acid) have been considered. Bubble diameter first reduced, reached a minimum and then started to increase in an oscillatory manner with increase in air flow rate. Before the onset of oscillatory behaviour an increase in hole diameter was seen to reduce bubble diameter. Such a behaviour is typical to bubble formation at lateral hole and is not seen for top-submerged nozzles with central opening. A detailed analysis of the results was carried out and it was observed that inertial forces played a major role. The work also reports a fundamental criterion which must be achieved for onset of oscillations in bubble diameter with flow rate. We also report a 2D CFD model that can simulate bubble formation dynamics at a lateral hole. The model was validated qualitatively as well as quantitatively against the experimental data. • Mechanistic picture of bubble detachment form a top-submerged nozzle with lateral hole. • Bubble diameter reduces to a minima, then increases in an oscillatory manner with air flow. • A fundamental criterion for onset of oscillations determined. • 2D CFD model reveals presence of asymmetric re-circulatory patterns in liquid phase. [ABSTRACT FROM AUTHOR]

This study investigates the behavior of air supply in tunnels with multiple vertical shafts during fire incidents, focusing on natural ventilation dynamics. Numerical simulation is utilized to analyze the effect of different variables on air supply within vertical shafts. The findings reveal that the position of the smoke front significantly influences the direction and flow rate of gases during fire development. The mass flow rate of air supply during the stable fire development stage is influenced by the geometric size and positioning of vertical shafts, with shafts closer to the fire source exhibiting higher air flow rates. To address this issue, this study introduces a predictive model for estimating air flow rates in vertical shafts. This model exhibits a high level of accuracy when compared to simulations, offering a reliable method for predicting air flow rates based on the geometric characteristics of vertical shafts. Overall, this research contributes to understanding the complexities of air supply in tunnels with multiple vertical shafts, aiding in the improvement of natural ventilation strategies during fire incidents. [ABSTRACT FROM AUTHOR]

In this study, the effect of gas flow rate and air stone pore size on the gas bubble-assisted fractional precipitation efficiency of paclitaxel was investigated. As the gas flow rate increased and the air stone pore size decreased, more numerous and smaller bubbles were generated and the bubble surface area increased. Additionally, at gas flow rates of 0.5 to 1.5 L/min, the precipitation yield and rate constant increased to be 2.2 to 2.4 and 3.2 to 4.3 times (air stone pore size 10 µm), 1.8 to 2.2 and 1.6 to 3.2 times (air stone pore size 30 µm), and 1.7 to 2.1 and 1.5 to 2.8 times (air stone pore size 43 µm) higher than those obtained in the conventional precipitation. Also, as the gas flow rate increased and the bubble size decreased, the changes in activation energy decreased. The results seem to confirm that the bubble surface acts as a heterogeneous nucleation site, lowering the free energy barrier for nucleation and thus improving the precipitation efficiency. [ABSTRACT FROM AUTHOR]

Dodecanedioic acid (DC12) is mainly prepared via microbial synthesis in industrial production, however, the refined products have many drawbacks, such as low purity, poor crystal size distribution (CSD), and heavily agglomerated character, to name a few. Therefore, the refining process is a crucial step in DC12 preparation by microbial production. In this study, a novel pneumatically agitated crystallizer for DC12 refinery by gassing crystallization was developed. A batch cooling crystallization process was developed, providing the final crystal in 82.0% yield and purity increment to 99.20% at the end of crystallization process. Optimized conditions were determined as the initial supersaturation ratio of 300:3000 (g/mL) and gassing air flow rate of 4 L/min with solution preparation temperature of 85 °C. The crystal products with significantly better morphology characteristics than the starting crude feedstocks, including crystal uniformity and color brightness, were harvested. These obtained results indicated that the pneumatically agitated crystallizer-based crystallization process without any mechanical agitation was a robust and economically feasible technique. To our knowledge, this is also the first DC12 crystallization process with sole gassing agitation for unseeded batch cooling crystallization. [ABSTRACT FROM AUTHOR]

The effects of using cyclone spiral inlets on the air flow pattern and the bioparticle separation process has been investigated using an integrated approach of computational fluid dynamics (CFD) and discrete element method (DEM). The investigation involved designing and testing six distinct cyclone separators with varied inlet dimensions and positions, featuring both single (SI) and double axisymmetric spiral (DI) inlets. A heterogeneous bio-granular flow was employed in experiments and numerical simulations, that consisted of airflow and jojoba seeds along with their leaves. The study's findings emphasised the critical role of inlet type and design in determining cyclone performance, as illustrated by differences in pressure, velocity, and turbulence parameters of the cyclone airflow. Specifically, the airflow behaviour of the double axisymmetric spiral inlets demonstrated enhanced coordination, resulting in a 4%–14% increase in cyclone performance. Single spiral inlets exhibited reasonable separation capabilities, particularly when the inlet height was increased. However, their performance was undermined by the suspension of seeds at the base of the cyclone. Based on the data collected, the study concludes that the double axisymmetric spiral inlet cyclone design is the most optimised design for achieving the highest performance in separating large particles such as jojoba seeds. The methodology determined the air-particle flow pattern analysis at precise operating conditions, concluding that inlet types and dimensions profoundly influence cyclone performance. These findings serve as a crucial step in developing efficient and effective separation systems for industrial and agricultural applications. [Display omitted] • Evaluation of flow and performance of single and double spiral inlet cyclones. • CFD is used to model the gas flow, and DEM to model and track particles. • Increasing inlet height improved the single spiral inlet cyclone's performance. • Cyclone performance varies significantly with inlet structures and dimensions. • Double spiral inlet cyclone exhibited a 14% performance boost. [ABSTRACT FROM AUTHOR]

The widespread industrial use of cupola-type shaft furnaces requires controlling their gas-dynamic and thermal behavior. When a cupola operates with an open top, its thermal regime is characterized mainly by the peripheral flow of gases with a significant difference in the ratio of the heat capacity of gas flows to material thermal capacity. The use of forced removal of exhaust gases from the shaft furnace contributes to an earlier transition from a peripheral to a predominantly central gas flow mechanism. By increasing the degree of rarefaction at the furnace top to 0.71 – 0.73 bar, it is possible to increase the melt temperature, pressure in the furnace cavity, temperature and air blast flow, as well as exhaust gas temperature while improving the conditions of heat transfer between gases and heated materials. A continuous decrease in the productivity of the unit accompanies this process, while the melting process stability improves. A further increase in the degree of rarefaction at the top contributes to a gradual transition from the peripheral to the central gas flow mechanism with a deterioration in cupola melting performance. [ABSTRACT FROM AUTHOR]

For bloodstain pattern analysis (BPA), interpreting statistically reliable data on a crime scene resulting from gunshots is a great challenge. This is due to various uncertainties, including blood rheology, hematocrit, coagulation, surrounding atmospheric conditions, victim's peculiarities, gun types, geometries, etc. In addition, muzzle (propellant) gases that follow the bullet may influence the aerodynamics of blood spatter in the cases of short-range shooting. We studied the muzzle gas effect on forward blood spatter. Muzzle gas can penetrate the wound channel and be ejected from the bullet exit hole affecting the forward blood spatter. Experiments with blood atomization by a gas flow issued from a supersonic de Laval converging–diverging nozzle are conducted. Defibrinated sheep blood was enclosed in a thin solid cylinder, which was filled by a supersonic air flow ejected from a de Laval nozzle, mimicking the muzzle gas flow through a wound channel. The mass flow rate of the supersonic air stream was varied by controlling the upstream chamber pressure. It was found that the number counts of the forward blood spatter from the muzzle gas blasting peaked at relatively shorter distances from the exit hole compared to the one that would be caused by a bullet. The effects of the muzzle gas and bullet could cause the formation of a bimodal spatter distribution on the floor behind the exit hole. These findings imply that atomization events owing to muzzle gas cause coarser atomization than that of a bullet, which could facilitate BPA in distinguishing certain homicides from staged suicides. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main contribution of this research study is to highlight the crucial role of radiating gas effect combined with circumferential ribs on the inner tube of a double-pipe heat exchanger to obtain higher thermal performance by recovering wasted heat for air heating. By taking the advantage of gases with higher radiative characteristics, significant performance improvement can be obtained by increasing the rate of heat transfer from participating hot exhaust gas flow to the cold air flow. This concept is demonstrated and verified by the numerical solution of the radiative transfer equation coupled with the set of conservation equations of energy, momentum, and continuity in steady-state conditions. The turbulent forced convection is solved by the well-known κ − ϵ model to calculate the turbulent stress and heat flux. All computations are done by the COMSOL multi-physics software for a wide range of gas radiative properties in the double-pipe HE with and without ribs. The numerical findings reveal that the contributions of ribs and gas radiation effect in increasing the HE efficiency are 21% and 45%, respectively. In addition, by adding ribs into HE configuration, an increase of pressure drop of 1.76 and 0.71 Pa is observed for the gas and air flows, respectively. [ABSTRACT FROM AUTHOR]

Three different sugarcane-based biochars were prepared as adsorption materials by the methods of direct carbonization, CO2 activation, and H3PO4 activation methods based on bagasse. The surface structure of sugarcane-based biochar was characterized by scanning electron microscopy（SEM） and pore size surface area analyzer（BET）. The adsorption performance of different sugarcane-based biochars on hydrogen sulfide（H2S） and ammonia（NH3） was tested on a fixed adsorption bed, and the effects of the adsorption temperature, the pollutant concentration, and the intake flow rate on the adsorption of H2S and NH3 on sugarcane-based biochar were investigated. The results showed that the he sugarcane-based biochar prepared by the H3PO4 activation had the largest specific surface area and total pore volume, reaching 1 181. 038 m~2·g-1 and 1. 174 cm~3·g-1,respectively. Increasing the adsorption temperature, intake air concentration and intake air flow rate were not conducive to the adsorption of H2S and NH3 by sugarcane-based biochar. The optimum adsorption process conditions were an adsorption temperature of 25 ℃,H2S and NH3 inlet concdntrations of 30×10-6,and an inlet gas flow rate of 1 000 mL·min-1. Under these conditions, the sugarcane-based biochar had the longest dynamic equilibrium adsorption time for H2S and NH3,and the dynamic equilibrium adsorption amounts reached 5. 96,5. 11 mg·g-1,respectively. The sugarcane-based biochar prepared by H3PO4 activation can be applied to the adsorption of H2S and NH3,and had a good application prospect. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Profile loss that contributes 1/3 of their total loss is one of the major sources of entropy within the turbine blades. Understanding loss mechanisms and accurate prediction of them play critical role in turbine design. In this study, the loss mechanisms within the two-dimensional axial flow turbine passage, whose working fluid is R134a, are computationally investigated. Firstly, the numerical model is experimentally validated with VKI LS89 and LS59 cascades for air flow by examining the variation of the total pressure loss for various exit Mach numbers of the cascades. Then, the real gas deviations of the aerodynamic loss generation for the case of R134a organic fluid from the ideal gas flow with air are investigated. It is observed that the results obtained using the ideal gas approach of R134a fluid do not provide significant deviations from the results obtained using air. The major difference appears when the inlet state of the real gas approaches the saturation line having low compressibility factors. As the compressibility factor decreases while going away from the ideal gas state, due to having high density, the Reynolds number increases. The shock losses behind the trailing edge decreases up to inlet compressibility factor of 0.7 but then they increase continuously with the decreasing compressibility factor. The compressibility factor and Reynolds number which are two driving mechanisms for the loss generation within turbine passage are investigated separately. It is observed that the total pressure loss decreases by 5% as the compressibility value goes from 1 to 0.7, and increases by about 50% as it goes from 0.7 to 0.4. According to the results obtained from the study, the loss correlations extracted for the ideal gas should be corrected when R134a gas is used. Finally, a curve that is fitted to the numerical results is offered to correct the profile loss coefficient for air flow. [ABSTRACT FROM AUTHOR]

Three organic monolayers coatings were developed and tested for their effectiveness to increase cleaning efficiency of attached microscale particles by air flows. The experiments were performed using silica substrates coated with these organic thin films and subsequently exposed to stainless-steel and silica microparticles as a model of contamination. Laser-induced–damage tests confirmed that the coatings do not affect the laser-induced–damage threshold values. The particle exposure results suggest that although the accumulation of particles is not significantly affected under the experimental conditions used in this work, the coated substrates exhibit significantly improved cleaning efficiency with a gas flow. A size-distribution analysis was conducted to study the adsorption and cleaning efficiency of particles of different sizes. It was observed that larger size (> 5-μm) particles can be removed from coated substrates with almost 100% efficiency. It was also determined that the coatings improve the cleaning efficiency of the smaller particles (≤ 5 μm) by 17% to 30% for the stainless steel metal and 19% to 38% for the silica particles. [ABSTRACT FROM AUTHOR]

The gas flow through sheet-like porous materials such as paper can show marked lateral variations due to a heterogeneous, locally varying microstructure. Hence, reliable predictions of such lateral flux variations require an appropriate consideration of local variations in the microstructure. The flow through such sheet-like materials is commonly described with Darcy's law in which permeances are formulated in terms of microstructure properties, such as porosities, tortuosities, or hydraulic radii. This work proposes an extension of existing permeance models that directly considers the variation and the cross-dependence between local microstructure properties. The extended model is applied to local air fluxes through a paper sheet to exemplarily reveal the joint impact of local porosities and local tortuosities on the air flux. The key extension is to consider a joint distribution of porosity and tortuosity. The latter is constructed from the univariate property distributions using a copula approach and yields local tortuosities including their variation for any encountered local porosity. These values jointly enter any permeance model that qualitatively captures the dependence of the air flux on the porosity. To assess the merit of the model, variations in the air flux and in the pore space properties are independently determined from the same measured microstructure of paper. Air flux variations are provided by computational fluid dynamics simulations on multiple, nonoverlapping segments taken from the microstructure. A statistical analysis of the entire microstructure provides the distribution of local porosity, tortuosity, and thicknesses. Our model quantitatively explains that porosity-dependent variations in the tortuosity, in particular the ones associated with high-volume pathways, decisively determine air flux variations. Article Highlights: Computational fluid dynamics simulations determine local variation of air flow through an actual microstructure of paper. Construction and use of the copula approach to model joint distribution of local porosities and tortuosities is explained. Existing permeance models equipped with variations in porosity and porosity dependent tortuosity capture most variations in air flow. [ABSTRACT FROM AUTHOR]

Water-sorption studies and certain organic chemistry reactions require water removal from cellulosic samples. This is hindered by the strong interaction of cellulosic materials with water, and it remains uncertain if a completely anhydrous state can be reached under common drying conditions. Here, different drying conditions were applied to wood and cellulose, and the residual moisture contents were quantified either gravimetrically or by coulometric Karl-Fischer titration. Vacuum-drying at 103 °C and ≤ 1 mbar for at least 360 min decreased the moisture content to ≤ 0.04%. However, in automated sorption balances, drying at atmospheric pressure under dry air or nitrogen flow left some samples with more than 1% moisture content. The residual moisture content obtained under dry gas flow was temperature dependent. Increasing the temperature up to 55 °C decreased the residual moisture content and cooling resulted in a moisture re-uptake, presumably due to small quantities of water vapor in the surrounding atmosphere. These effects must be considered in fundamental studies on water interactions of cellulosic materials. [ABSTRACT FROM AUTHOR]

To reduce the emission of nitrogen oxides (NOx) during the co-disposal of sludge in a TTF-type precalciner, an optimized co-disposal process of a TTF-type precalciner has been implemented in a cement plant in Hebei. The model was built using ANSYS FLUENT software. The effects of three singlefactor perspectives (sludge input ratio, gas flow rate, and tertiary air temperature on NO concentration) were investigated. The response surface method of Box-Behnken design was used. When the sludge ratio increased from 0 to 25%, the NO concentration at the outlet was 122-297 mg/m2. Meanwhile, it increased from 192 mg/m2 to 241 mg/m2 since the airflow increased from 95 m2/s to 122 m2/s. The maximum NO concentration was 192 mg/m2 when the tertiary air temperature was 1170 K. The interaction between airflow and sludge ratio was more significant than any other interaction between other conditions (P < 0.05). Finally, the optimum conditions were a sludge ratio of 5%, airflow 109 m2/s, and tertiary air temperature 1280 K. NO concentration was 166.9 mg/m2 under this condition. [ABSTRACT FROM AUTHOR]

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Dynamic gas lock (DGL) is one of the central components of contamination control for extreme ultraviolet lithography, and airflow efficiency is a key parameter. In this paper, the principle of the DGL and airflow efficiency is described at first, then a set of experiments is carried out on a self-developed DGL experimental device. The results of the experiment show that the pressures of the project optics box and the wafer chamber do not influence the airflow efficiency of DGL. In addition, the airflow efficiency increases slowly with the total airflow, and the gradient gradually diminishes. With an increase in the total airflow from 1 to 3 Pa m3/s, the argon efficiency increases from 0.247 to 0.260, while the nitrogen efficiency increases from 0.251 to 0.264, which shows that the efficiency of argon is slightly smaller than that of nitrogen under the same conditions. Within the interesting range of argon gas flow, the maximum difference between theory and experiment is less than 6%, which is acceptable in engineering. The theoretical calculation method in this paper can be used to evaluate the airflow efficiency for engineering applications. It is concluded that the airflow efficiency of the DGL is almost independent of the pressures of the upper and lower sides. However, the total airflow and the gas species will change the airflow efficiency. [ABSTRACT FROM AUTHOR]

The smelting reduction of vanadium–titanium magnetite (VTM) with oxygen-rich side-blown bath smelting furnace (OSBF) is a promising process. However, the study on the behavior of gas–liquid multiphase flow in the OSBF in ironmaking process is deficient. In present work, a 3D simulation model of the OSBF is established to investigate the multiphase flow of gas–slag–metal in the furnace during the VTM smelting process. The bubbles motion, slag phase distribution, flow field distribution, and the flow status in the bath during the smelting process are obtained by combining the Coupled Level Set Volume of Fluid (CLSVOF) method and the Realizable k-ε model. The analysis of the characteristics of gas–slag–metal multiphase flow in the horizontal and vertical directions in the bath indicates that the gas and slag in the bath are evenly mixed, the fluctuation of the slag iron interface is subtle, and the turbulence of the molten iron layer is weak, which is conductive to the smelting process. In addition, the effects of primary air flow, slag layer thickness, and slag viscosity on the smelting process are also studied, and the appropriate operation conditions were recommended. This provides a theoretical basis for the operation and optimization design of the OSBF. [ABSTRACT FROM AUTHOR]

As the core equipment for the production of high-purity magnesia, the determination of suitable structure and operating parameters has a significant impact on its efficient production. In present work, a three-dimensional numerical model of the high-purity magnesia shaft kiln is established to study the influence of different operating and structural parameters on outlet clinker temperature and outlet exhaust air temperature. The novelty is adding a convective term to the solid-phase equation of the energy model, as well as embedding the heat transfer coefficient and a modified Ergun's correlation, obtained by a homemade experimental setup. Production data verify the accuracy and reliability of the model. The results indicate that with all other parameters being constant, the most significant impact on the outlet temperature of clinker and exhaust air is cooling air flow rate, followed by sintering gas flow rate, height below the burners and height above the burners. Finally, a combination of parameters for the 50,000 tons shaft kiln is obtained through orthogonal experiment and optimization, which is 2622 m3/h for sintering gas flow rate, 2422 m3/h for cooling air flow rate, 7.07 m for the height above the burners, and 12.14 m for the height below the burners. [Display omitted] • A reliable numerical model of gas solid heat transfer process in shaft kiln is established. • Effects of structural and operating parameters on the outlet temperature in shaft kiln are investigated. • A suitable parameter combination condition is determined through orthogonal experiment. • The range of the appropriate parameters are obtained by univariate analysis. [ABSTRACT FROM AUTHOR]

Direct ionization mass spectrometry has the advantages of rapid, in-situ and real-time ionization, which has been widely used for the detection of drugs, explosives, food additives, etc. The coupling between direct ionization source and mass spectrometer vacuum is usually achieved with a narrow baffle hole such as capillary or skimmer, which can result in a significant reduction in the ion transmission efficiency. It is well known that this has become a key bottleneck for the improvement of instrument sensitivity. This study was carried out based on a rapid screening mass spectrometry platform coupled with a pulsed direct current electrospray ionization (pulsed-dc ESI) source, which has the advantages of low sample volume required, high ionization efficiency, no cross-contamination risk, and so on. The instrument performances with flat and flared capillaries under different spray voltages, emitter positions, inner diameters of emitter, diameters of capillary inlet were investigated. For the pulsed-dc ESI emitters with the inner diameter of 5, 20, 50 and 100 μm, the highest ion intensity could be achieved with the 20 μm emitter for all capillaries. Besides, compared with the flat capillary, the ion intensity of flared capillary was more stable to the variation of radial distance between emitter and capillary inlet. By simulating the gas flow and ion trajectories of various capillaries, it was found that the air stream around capillary inlet dominated the ion transmission. For the flat capillary, the gas flow pointed inward only in the area of very close to the porthole. As a contrast, the gas velocities of flared capillaries increased gradually from the entrance of conical mouth to the narrowest part of capillary, of which the directions always pointed to the capillary’s porthole. Due to the larger radial focusable airflow area, the flared capillaries, especially the flared capillary with an inlet diameter of 6 mm could evidently improve the ion transmission efficiency between the direct ionization source and the mass spectrometer. In the simulation, the enhancement of ion transmission efficiencies by fared capillaries was more prominent for high mass-to-charge ratio ions, of which the motion usually was more sensitive to gas flow because of lower mobility. Compared to the conventional flat capillary, the ion signal intensity of 10 μg/L standard methamphetamine solution by the flared capillary of 6 mm in the inlet diameter had increased 3.3 times. The signal-to-noise ratios of five conventional drugs, such as methamphetamine, 3,4-methylenedioxymethamphetamine, ketamine, cocaine, and O6-monoacetylmorphine in hair matrix were also boosted to certain degrees. Especially for ketamine, the signal-to-noise ratio of the flared capillary to the flat capillary was up to 3.3. The results showed that the adoption of a flared capillary can significantly increase the detection sensitivity of direct ionization screening platform, which does not require any complex modification to the instrument. [ABSTRACT FROM AUTHOR]

Today, reciprocating internal combustion engines are used in many branches of the economy (power engineering, machine engineering, transportation, and others). In order for piston engines to meet stringent environmental and economic regulations, it is necessary to develop complex and accurate control systems for the physical processes in engine elements based on digital twins, machine learning, and artificial intelligence algorithms. This article is aimed at preparing and analysing experimental data on the gas dynamics and heat transfer of pulsating air flows in a piston engine's intake system for modelling and machine learning. The key studies were carried out on a full-scale model of a single-cylinder piston engine under dynamic conditions. Some experimental findings on the gas-dynamic and heat-exchange characteristics of the flows were obtained with the thermal anemometry method and a corresponding measuring system. The effects of the inlet channel diameter on the air flow, the intensity of turbulence, and the heat transfer coefficient of pulsating air flows in a piston engine's inlet system are shown. A mathematical description of the dependences of the turbulence intensity, heat transfer coefficient, and Nusselt number on operation factors (crankshaft speed, air flow velocity, Reynolds number) and the inlet channel's geometric dimensions are proposed. Based on the mathematical modelling of the thermodynamic cycle, the operational and environmental performance of a piston engine with intake systems containing channels with different diameters were assessed. The presented data could be useful for refining engineering calculations and mathematical models, as well as for developing digital twins and engine control systems. [ABSTRACT FROM AUTHOR]

Pythium species are saprophytic or facultative plant pathogens that cause a variety of diseases. Usually, chemical anti-fungal seed dressing is applied in the conventional pre-harvest for seed protection. Nevertheless, recent legislative rules have created a ban on certain agrochemicals. Therefore, alternative eco-friendly methods have to be identified to ensure healthy field emergence and seedling development. In this study, a proof-of-concept was performed on the inactivation of Pythium ultimum Trow mycelia grown on potato dextrose broth agar (PBA) by plasma-processed air (PPA). Different plasma process parameters were applied using variation in gas flow of air through the microwave plasma generator and PPA exposure time. The PPA treatment was compared to the untreated and gas treated controls. The results showed a complete inactivation of P. ultimum mycelia after the PPA treatment. Inactivation efficiency was independent of the gas flow parameter and even shorter exposure times resulted in complete inactivation. To fully evaluate the potential of PPA as a possible seed hygiene measure, tests regarding the inactivation of P. ultimum after artificial inoculation onto seeds and/or studies using naturally infected seeds should be performed. This may be accompanied by monitoring the disease severity after the PPA treatment on a field scale. [ABSTRACT FROM AUTHOR]

The treatment of polluted industrial flow remains a relevant topic for the purpose of sustainable development and improvement of the general state of the environment. The removal of particulate matter, and especially their fine and ultra-fine fractions, from the gas flow, is an urgent task, but it poses many challenges and demands for purification technology. This paper presents the results of the first stage of the research using a newly developed cleaning device operating by a complex principle, which consists of a new generation two-stage centrifugal filtration device and an electro-filter. The rate of air flow was varied from 0.3 to 1.16 m/s at the inlet and corresponds to an air flow yield of 53 m3/h to 205 m3/h. The maximum pressure drop at an air flow of 255 m3/h is 26 Pa. Research has shown that the efficiency of removing ultra-fine particulate matter is up to 99.7% for particles 0.3–0.5 µm in size at 200 m3/h of the air flow rate. [ABSTRACT FROM AUTHOR]

Turbulence in fluids is an ubiquitous phenomenon, characterized by spontaneous transition of a smooth, laminar flow to rapidly changing, chaotic dynamics. In 1883, Reynolds experimentally demonstrated that, in an initially laminar flow of water, turbulent motions emerge without any measurable external disturbance. To this day, turbulence remains a major unresolved phenomenon in fluid mechanics; in particular, there is a lack of a mathematical model where turbulent dynamics emerge naturally from a laminar flow. Recently, we proposed a new theory of turbulence in gases, according to which turbulent motions are created in an inertial gas flow by the mean field effect of the intermolecular potential. In the current work, we investigate the effect of viscosity in our turbulence model by numerically simulating the air flow at normal conditions in a straight pipe for different values of the Reynolds number. We find that the transition between laminar and turbulent flow in our model occurs, without any deliberate perturbations, as the Reynolds number increases from 2000 to 4000. As the simulated flow becomes turbulent, the decay rate of the time averaged Fourier spectrum of the kinetic energy in our model approaches Kolmogorov's inverse five-thirds law. Both results are consistent with experiments and observations. [ABSTRACT FROM AUTHOR]

This article presents an experimental stand for the generation of gas flows with very low velocities. The constant volume air flow was generated in the measurement area with the use of a Mariotte bottle and a water piston (water column in a tank). The air-flow velocity was determined from the change in the height of the water piston with time, which was measured via the difference between the pressure above the water surface and the pressure at the bottom of the water column. The tests were carried out in the mean velocity range of 0.35–66 cm/s. The five different velocities of air flowing out of the measurement pipe, measured with the particle image velocimetry method were compared with the results from the water piston method. The differences did not exceed 7%. [ABSTRACT FROM AUTHOR]

Ionic wind is a phenomenon of electrofluid movement in electrostatic precipitator, which changes the motion state of flue gas and dust in electrostatic precipitator to a certain extent. In order to study the influence of ionic wind on air flow characteristics in electrostatic precipitator, this paper constructed a numerical model of electric field-flow field coupling and compared the impact of electro-hydro dynamics (EHD) effect on flue gas flow state at different inlet velocities. In addition, this paper analyzed the influence of EHD effect on the motion trajectories of particles with different sizes. The results showed that the EHD effect changed the flue gas flow field near the anode plate at 0.3m/s inlet velocity, forming an obvious reflux region; this phenomenon weakened when the inlet velocity increased. At the same time, the EHD effect reduced the dust removal efficiency when the particle radius ranged from 0.25 µm to 1 µm. [ABSTRACT FROM AUTHOR]

In this paper, the proposed diamagnetic levitation structure was studied to explore its potential in energy harvesting. It is proved that the floating magnet rotor can be levitated stably under the joint action of two highly oriented pyrolytic graphite (HOPG) sheets and the lifting magnet. Simulation calculation was carried out to analyze the influence of different coil radius and wire diameter on peak voltage and average power in scheme A or scheme B, so as to obtain appropriate layout and wire diameter for the coils which was built the experimental platform. Subsequently, the center hole, notch radius and thickness of the floating rotor are analyzed by experiment. And the influence of different parameters on rotation speed of the rotor and peak output voltage of coils is obtained. Through experimental results, it is found that the notch radius of the floating rotor has the greatest influence on the rotation speed of the rotor. Based on the experiment, a new-type rotor was designed, with an outer shell to reduce the notch radius. Compared with the original floating rotor, there was 49.73% increase in voltage, 55.70% increase in rotation speed and 124.50% increase in power according to the experimental results. Test was performed with the optimization, the LED array of Zhengzhou University logo, which was composed of 60 LED lights, was lighting up. According to the oscilloscope measurement, the diamagnetic levitation energy harvester has an output voltage up to 1.294 V and average power of 60.67 mW under gas flow rate of 3000 sccm and nozzle exit velocity of 6.173 m/s. Obviously, the new-type rotor proposed in this paper could significantly increase the energy conversion efficiency, and make the future application of airflow energy harvester a step further. [ABSTRACT FROM AUTHOR]

Prefilming air-blast atomizers are widely used in modern gas turbine combustors. Due to insufficient awareness of the coupling mechanism of multi-stage swirling flow in gas turbines, there is a lack of effective methods for flow field optimization in combustor. In this study, the effect of some critical parameters on the flow field of a prefilming air-blast atomizer was analyzed with CFD. The parameters include the angle and number of the first swirler blades, the angle of the second swirler blades and the angle of sleeve. Furthermore, the coupling mechanism of two-stage swirling airflows of prefilming air-blast atomizer was discussed. Moreover, the influence of the interaction between two-stage counter swirling airflows on the characteristics of flow field was explained. The results show that with the increase in SNi, the axial length of the primary recirculation zone decreased, while the radial width increased. The starting position of primary recirculation zone (PRZ) moves forward with the increase in SNo. Reducing the sleeve angle β helps to form the primary recirculation zone. The results indicate that it is the transition of tangential velocity of airflow to radial velocity that promotes the formation of the PRZ. These results provide theoretical support for optimization of the flow field in swirl combustor. [ABSTRACT FROM AUTHOR]

In this article, three-dimensional periodic numerical model for fully developed flow in a cross wavy primary surface recuperator for a micro-gas turbine system is built. Influence of leakage of air hole on flow and heat transfer of high temperature gas core and compressed air core was analyzed. The results of analysis show that with leakage of air hole considered, flow velocity of compressed air from air hole flowing into gas core is far greater than that of high temperature gas. In addition, the flow is opposite to each other. As a result, the flow resistance in gas channel increases. With leakage of air hole considered, heat convection between gas core and air core weakens. When the diameter of air hole increases by 50 μm, maximum temperature in gas core increases by 1 K in a period. The performance of heat recovery for regenerator is degraded. Thermal ratio decreases with the improvement the diameter of air hole. When the diameter of air hole increases by 50 μm, thermal ratio decreases by about 0.3%. The flow in the gas and air channel is anti-symmetry along the center of channel. The flow of fluid is fluctuant. The flow velocity of gas is much larger than that of air. The research results can be used to guide checking the performance of a recuperator. [ABSTRACT FROM AUTHOR]

Powder mixing is critical in many industries. Despite the wide variety of available mixers, the container blender is favored in industries due to easy manufacturing and convenient operation. As fine powders are frequently encountered in practical mixing, the presence of air during mixing may significantly impact the process. However, a scientific understanding of air–particle interactions in powder mixing has not been established so far. From a physical view, the air drag force on particles might be significant when the gas velocity is high and the particles are fine. Therefore, this novel study numerically investigates the effects of particle size and air presence on powder mixing under typical conditions, such that the relationship between particle–fluid dynamics and mixing performance is clarified for the first time. In the calculation, our advanced computational fluid dynamics–discrete element method, namely, the flexible Eulerian–Lagrangian method with an implicit algorithm, is utilized. To examine the effect of particle size on powder mixing, the coarse-grained discrete element method is employed for fine particle systems. Through the advanced numerical framework, the effect of airflow on powder mixing can be discussed in depth. The numerical results show that airflow accelerates the mixing of fine particles under the investigated rotation speeds. Based on the calculation results of the particle kinetics and fluid velocity distribution, it is clarified that the accelerated mixing results from the fine particle movement under air entrainment. How the movement of fine particles is developed is also elucidated by the continuously circulating gas flow and fluid drag force. Thus, this study provides a new understanding of the effects of airflow on powder mixing, which has not been scientifically clarified in previous studies. [ABSTRACT FROM AUTHOR]