Vortex Air Flow Research Articles

The preparation of polypropylene microfiber yarns via vortex airflow‐assisted melt differential electrospinning

AbstractPolypropylene (PP) yarn possesses the advantages of low density and exceptional mechanical properties. Through electrospinning, fibers of PP yarns can be refined from 10 to 20 μm to an ultrafine level, thereby acquiring an enlarged specific surface area and more functional sites, expanding its application in high‐value areas. Herein, vortex airflow‐assisted polymer melt differential electrospinning was proposed to fabricate PP microfiber yarns. Under the influence of an electrostatic field, molten PP automatically splits into multiple jets that are further stretched and cooled into ultrafine fibers by suction airflow induced by vortex airflow. Subsequently, multiple ultrafine fibers were twisted into PP yarns using the vortex airflow. The effects of voltage, melt feed speed, and air pressure on the PP electrospun yams formation process as well as the morphology and mechanical properties of both the yarn and fibers were investigated. The results showed that the diameter of PP fibers ranged from 3 to 5 μm. The PP microfiber yams exhibited a relatively high mechanical strength of 1.6 cN/tex under conditions of 56 kV voltage, 0.22 g/min feed rate, and 0.3 MPa air pressure. Finally, the woven fabric made from electrospun PP yams demonstrated higher hydrophobicity compared with fabric woven from commercial PP filaments, suggesting potential applications in waterproof fabrics.

Characteristics of columnar vortex airflow and dust escape prevention based on artificial tornado

Dust pollution resulting from industrial production posed a significant risk to worker health. To address this issue, the coupling model of airflow and dust was established using the Eulerian-Lagrange method and the effectiveness of this model was via experimental data. Then, the airflow-dust coupling diffusion results using the columnar vortex ventilation system from different jet angle θ, jet velocity vJ and suction-blowing flow ratio γ were simulated. The results indicated that the columnar vortex ventilation system generated “columnar vortex airflow” by synergistically combining the surrounding air supply jets and upper exhaust airflow. Firstly, as vJ increased, θ and γ decreased, the mutual impact between the jets would be intensified, resulting in decreased vortex stability, which in turn caused a decrease in the dust removal rate. Simultaneously, excessive θ and vJ resulted in vortex range expansion, increasing dust pollution area in the near-floor, and decreasing the dust removal efficiency. Finally, the optimal parameters were θ = 65°, vJ = 2.25 m/s, and γ = 1.06. Under the optimal parameter scheme, the dust removal efficiency of the column vortex ventilation system reached 86%. This study provided a theoretical reference for the application of the column vortex ventilation system and the improvement of the environment in industrial plants.

Field experiment and numerical simulation for airflow evaluation in a data center with row-based cooling

Row-based cooling has been recommended for cooling scenarios with high power densities. Existing studies on row-based cooling have mostly focused on good results, and the effectiveness and limitations of it need to be evaluated to optimize it. In this study, some airflow problems were observed by a field experiment for a data center with row-based cooling. Subsequently, a simulation corresponding to this data center was performed to fully learn and verify some airflow conditions below those expected, such as hot spots in some racks and vortex airflow, where the Supply Heat Index of modules 1 and 2 are 0.37 and 0.31. To further determine the airflow characteristics of row-based cooling, a comparative simulation of airflow distribution of row-based cooling and raised-floor cooling was performed. Finally, the effectiveness and limitations of row-based cooling were presented. The results showed that row-based cooling only decreases the Return Temperature Index by 0.4%. The limitations of it include vortex airflow, hot spots in head racks and adjacent racks of in-row coolers, and interaction between different modules; they are easy to occur in row-based cooling and some improvement suggestions are presented in future work.

Numerical simulation of the spatial and temporal distributions of the downwash airflow and spray field of a co-axial eight-rotor plant protection UAV in hover

The downwash airflow of a multi-rotor unmanned aerial vehicle (UAV) in hover can improve the penetration rate of droplets in the canopy of fruit trees, but the uncertain distribution of the downwash airflow can also lead to the generation of uneven distribution of droplets. With a co-axial eight-rotor plant protection UAV as the research object, the computational fluid dynamics (CFD) method is adopted in this study to establish the coupled flow field model of the downwash airflow and the two-phase flow model of airflow-droplets in hover. The spatial and temporal distribution law of the downwash airflow is analyzed, and the impact of the motion law of the droplets in the spray field is investigated. The results show that the downwash airflow shifts from an unsteady state to a steady state over time. Various wind vortices such as wake vortex, ground diffusion airflow, and vortex ring are generated during the evolution process, with a “negative velocity channel” of downwash airflow velocity identified in the central region under the rotors. The farther the airflow is from the rotor, the larger the area field of wake vortex airflow. Consequently, there is a gradual coupling of the left and right adjacent wake vortices from mutual independence, with the “spiral effect” of the downwash wind field offset by the mutual coupling of the upper and lower rotors of the UAV. When the installation position of the nozzle falls within the below-rotor region, the distribution of droplet deposition becomes more penetrative than the central axis installation position of the nozzle. It indicates that the below-rotor installation position of the nozzle can prevent droplets from entering into the coupling region of the trailing vortex, which reduces droplet drift. According to the field test, the measurement and simulation results of the downwash air velocity are consistent, with the minimum and maximum relative error reaching 4% and 29%.

A multiphase data fusion approach based on CFD-DEM for gas–solid flow simulation in PDSS

In order to improve the operating environment of the bulk material transfer system and promote the digital construction of such systems, a new multiphase data fusion method is proposed for simulation of dust suppression in the digital twin system. It is applied to the multiphase flow motion simulation in a new Powerless Dust Suppression System (PDSS), and the results show that the method based on Discrete Element Methods (DEM) and Computational Fluid Dynamics (CFD) can well calculate the interaction between air and bulk material. A stable vortex airflow field can be generated in the structure of the PDSS, and the speed difference between the inlet and the exit of transfer chute is almost 0%, which can effectively bind the fine coal dust particles and prevent dust diffusion. In the structure where the curtain is arranged, a part of the vortex airflow will flow back after the action of the curtain, the backflow air can further reduce the speed of the airflow, and the dust-laden airflow has more time to contact the curtain and the material to cause sedimentation, which can further prevent dust emission. This study provides a practical reference for the design of transfer dispatching station and other similar particle–fluid digital twin systems.

Numerical study on the effect of buoyancy-driven pollution source on vortex ventilation performance

High-temperature buoyancy-driven pollutants that generally exist in industrial buildings and kitchens often be eliminated by local exhaust ventilation systems. The high-temperature pollutant plume driven by buoyancy significantly affects the local exhaust process, resulting in the change in the exhaust flow field and reduction of the pollutant capture efficiency. In this study, the effects of thermal buoyancy-driven pollution sources on the vortex flow field and pollutant removal efficiency of a vortex ventilation system are evaluated through experiments and numerical simulations. The results show that with an increase in the buoyancy flux of the pollution source, the minimum negative pressure and maximum tangential velocity in the vortex flow first increase and then decrease, that is, the buoyancy plume first enhances and then weakens the vortex flow. A critical buoyancy flux exists, and the value of the critical buoyancy flux increases with an increase in the vortex ventilation intensity. Furthermore, the capture of high-temperature pollutants by vortex flow can be categorized as “plume-dominated” and “vortex-dominated”. These two types exhibit significant differences in pollutant transport paths and pollutant capture times during pollutant removal. In addition, on the basis of the pollutant capture efficiency, the vortex airflow performance with respect to capturing high-temperature buoyancy-driven pollutants can be classified as low-efficiency, transition, high-efficiency, and invalid zones. In the process of capturing high-temperature pollutants, vortex ventilation systems should be avoided in the low-efficiency and invalid zones.

Research and application of dust reduction technology for supersonic spiral an atomizers

To solve the problem of dust pollution, a new type of ultrafine spiral atomization nozzle with a small droplet size and strong dust reduction ability was developed according to the principle of air-water spray and the generation law of vortex airflow. Numerical simulation software is used to simulate the velocity and streamline distribution of the air flow field inside the air flow director under different parameters, and the best spiral effect parameters of the air flow director for the directional air flow are obtained. Set up an experimental platform to determine the performance parameters of the ultrafine spiral atomization nozzle and compare the dust suppression performance of the ultrasonic dry mist to study its dust suppression performance. The results show that when the angle between the spiral trough and the tapered wall is α = 30° and the ratio of the diameter of the top surface of the air flow director to the height d = 1.25, the air flow director has the best directional air flow spiral effect. When the air supply pressure of the supersonic nozzle and spiral groove is 0.4 MPa, the atomization angle of the supersonic spiral atomizer is the largest, the D90 of the droplet group is 19.7 μm, and the comprehensive atomization performance is the best. At this time, the total dust reduction efficiency is 92.18%, which is better than the ultrasonic dry mist for dust suppression and dust reduction. The efficiency is 81.97%. When the full-section spiral pneumatic dust control system with an ultrafine spiral atomization nozzle as the core is applied to the 06 return airway of the Mindong No. 1 Mine, the dust reduction efficiency of the respirable dust is 88.8% ~ 91.58%.

Numerical simulation and experimental study of vortex blowing suction dust control in a coal yard with multiple dust production points

The dust removal efficiency of the existing dust control technologies for coal yards involving multiple dust production spots is low and cannot satisfy the requirements stipulated by the existing standards. This paper proposes a new type of vortex blowing suction dust control technology. The principle of dust control was examined through numerical simulations. The dust control efficiency of the single suction and vortex blowing suction methods was compared experimentally. The results indicated that most of the dust particles were collected by the vortex, and they moved in a spiral from the bottom to the top. The highest vortex airflow performance corresponded to an optimal blowing ratio of 4.814. The experimental comparison indicated that the dust removal performance of the vortex blowing suction technique was better. Specifically, for the formal and latter techniques, dust removal efficiency was 93.25% and 41.19%, and dust escape rate was 6.31% and 46.60%, respectively.

Assessment of spray deposition, drift and mass balance from unmanned aerial vehicle sprayer using an artificial vineyard.

Under the rapid development of unmanned aerial vehicle (UAV) plant protection products (PPP) application in Asian countries, the drift risk of UAV sprayer operation in orchard or vineyard is fairly high because of the much finer droplets generated and the higher height than ground sprayers, increasing threats to non-targeted crop, human and environment. However, there is few of comprehensive experimental study on the effects of UAV type and nozzle type on spray deposition and drift from UAV sprayer. The objectives of this study were to compare the spray performance of three different typical commercial UAV types (helicopter, 6-rotor and 8-rotor) with two nozzles types (hollow cone nozzle, HCN and air-injector flat fan nozzle, AIN) in vineyard. An artificial vineyard and three vertical collection frames, designed and built by ourselves, were applied for collecting droplets together with PVC collectors, petri dishes and rotary samples. The characteristics of deposition, drift and mass balance of UAV aerial spraying in vineyard were analyzed. As a result, under the crosswind speed of 3.11-3.79m/s, AIN promoted spray deposition and uniformity and reduced drift significantly compared to HCN for all tested UAVs, improving of the utilization of PPP. The fitted regression functions of the sedimenting and airborne drift were obtained, respectively, and the drift percentage reduction values of AIN compared to HCN determined based on those functions varied from 81% to 95%. With HCN, 49.3%-73.4% of measured droplets drifted into non-targeted area and the highest proportion of drift loss was found for the airborne spray drift. According to the principle of more deposition and less drift, the spray performance of the three UAVs can be ranked in an order of 6-rotor, 8-rotor and helicopter, and two main reasons causing the difference in spray performance were the vortex airflow and the nozzle arrangement.

Design and Experimental Characterization of an Indoor-Scale Artificial Updraft Vortex Power Generator

An indoor-scale experimental model of artificial vortex power generator has been designed and tested. The model consists of four main components which are collector, tower, guide walls, and heating system. The collector and tower are constructed from poly-methyl methacrylate material. Both collector and tower are translucent allowing flow visualization experiments with laser and smoke to be performed for experimental characterization. The experimental model converts the supplied thermal energy into kinetic energy in form of updraft vortex airflow. Magnitude of the artificial updraft vortex is measured using a fan installed at the center of the tower. Rotational speed of the fan is measured by using a high-speed camera. The results show that the experimental model capable to rotate the fan up to 200 rpm.

Air Supply Mode Effects on Ozone Production of Surface Dielectric Barrier Discharge in a Cylindrical Configuration

We investigated the air supply mode effects on ozone production of the surface dielectric barrier discharge in the cylindrical configuration. The air into the discharge volume between two coaxial cylinders was supplied through four nozzles axially or tangentially. Using tangential air supply, the vortex flow in the part of the discharge chamber was created. Because the active electrode was in the form of interconnected rings on the outer surface of the glass tube, we changed the airflow orientation concerning this electrode. The existence of vortex airflow affects the plasmachemical processes taking part in the discharge, and therefore, it affects discharge ozone production. We also paid attention to ozone concentration and temperature of output air measurements as a function of the duration of the experiment for both tangential and axial air supply modes. We found that the time required for the stabilization of generated ozone concentration depends on the discharge power, and for our experimental conditions, it smaller than approximately 70 s. Besides, in the case of tangential air supply into the discharge chamber, the concentration of ozone produced by the discharge is for higher discharge power increased in comparison with the concentration for the axial air supply mode.

Investigation on cooling the hot tube surfaces of vortex tube at different pressure and fraction with comprehensive thermal performance analysis

The Raque Hilsch Vortex Tube (RHVT) is a heat pump system that uses the phenomenon of compressed vortex airflow in a tube for cooling and heating. This study aims to determine the effect of pressure and fraction on RHVT by cooling the surface of the hot tube naturally and forcefully. Tube type testing was conducted with a pressure variation of 0.5–1.5 bar and a fraction of 30%–70%. The results of the analysis show that forced cooling on the surface of the hot tube decreases the heating performance (Th, ΔTh, Q˙h, ηish, and COPh) and improves the cooling performance (Tc, ΔTc, Q˙c, ηisc and COPref). The higher pressure increases the performance of ThΔTh, Q˙h, TcΔTc, and Q˙c, and decrease the performance of ηish, COPh, ηisc, and COPref. The fraction 40% is the most optimal parameter for the performance of TcΔTc, Q˙c. The 60% fraction works best for Th, ΔTh, Q˙h, ηish, and COPh, while the fraction 70% works best for Q˙c and COPref. The most optimal performance values include Th (41 °C), ΔTh (14 °C), Q˙h(2.369kJ/s), ηish(24.21%), COPh (0.092), Tc (13.450 °C), ΔTc (13.550 °C), Q˙c(3.280kJ/s), ηisc (20.84%), and COPref (0.123).

Investigation of the regularities of particle motion in a vortex air flow of radius variable in height

Annotation Purpose. Improving the mathematical description of the motion of a solid particle in a vortex air flow for the case of changing the radius of twisting of the flow in the main direction. Methods. The specificity of the question under consideration determines the analytical method of research based on the compilation and analysis of the equations of motion of the particle, in the form of a sphere in the vortex air flow of a conical channel with uneven distribution of air flow velocity over height. Results. The motion of a solid particle in the air in the middle of a conical air-permeable surface is considered; air is sucked through the lateral surface of the cone with louver slits (holes) in the tangential direction, under the action of artificially created forces of the vortex air flow there is an effective intensification of grain fractionation. The obtained equation of particle motion under the action of vortex air flow allows to determine the dependence of material velocity in the grain material layer on a number of factors: geometric parameters of the separator, material feed angle, initial kinematic mode of the material and particle vitality coefficient. Conclusions. Based on the analysis of the force interaction of a particle of grain material with a vortex air flow, an improved mathematical model of particle motion in a non-uniform field of air flow velocity in a conical channel is obtained. Keywords: variable air velocity, trajectory, stability of forces, fractions, vortex air flow, fractionation process, grain mixture.

Features of the Current Sustainment in a Low-Current Discharge in Airflow

The paper relates to the investigations of a low-current discharge in a vortex airflow with the electrode configuration corresponding to classical coaxial plasmatron. The gas flow rate is varied from 0.1 to 0.3 g/s at an inner diameter of the plasmatron nozzle of 5 mm. The discharge is powered by dc voltage via a ballast resistor. Typical averaged current is changed from 0.06 to 0.15 A so that a maximum averaged power dissipated in the discharge amounts to 160 W. In these conditions, a luminous gas region at the plasmatron exit, which in most publications is associated with a plasma jet, is observed. The method for the jet diagnostics based on a usage of the additional electrodes at the plasmatron exit has been proposed. The main idea of the experiments is the elucidation of the problem whether the jet actually represents the plasma area or we have to apply the term “plasma” with care. In particular, in the case under discussion the main charged particles in the jet are electrons that are emitted from a plasma column located in the plasmatron nozzle. The model that describes the formation of electron flow in the jet has been proposed. Typical electron density in the jet estimated with a usage of the model is at a level of 109 cm−3.

Plasmochemical Approach to Template‐Free Synthesis of Highly Crystalline Mesoporous TiO2 within Milliseconds

AbstractA plasmochemical synthetic strategy for the template‐free and one‐step preparation of highly crystalline mesoporous TiO2 from oxidation of titanium tetraisopropoxide (TTIP) aerosol by gliding arc plasma in a vortex air flow within milliseconds is reported. The scanning electron microscopy, high‐resolution transmission electron microscopy, and nitrogen sorption characterizations confirm the wormhole‐like mesoporous structures. The highly crystalline mesoporous TiO2 has an optimized anatase/rutile weight ratio of about 80/20 for photocatalytic applications, exhibiting superior thermal stability and good photocatalytic activity.

Thermal buoyancy driven flows inside the industrial buildings primarily ventilated by the mechanical fans: Local facilitation and infiltration

The turbine hall houses a number of components with intense heat release, resulting in a hot and humid air environment and making it very unpleasant for plant staffs to conduct maintenance work there, particularly at a hot outdoor environment. The traditional pure buoyancy driven natural ventilated could fulfil the overall heat exhausting requirement, however, creating hot environment at several positions due to the vortex airflow structure. As only part of the building need to be cooled, a localized cooling system with assisting mechanical fans is used. Buoyancy driven natural ventilated flows primarily occupying this turbine hall have been investigated by a computational fluid dynamics (CFD) model and an on-site measurement. The ventilation airflow is solved by 3D steady state Reynolds Averaged Navier-Stokes (RANS) equations in conjunction with the SST k-ω turbulence model. The numerical codes and procedures were validated by comparing with on-site measurements. The concept of mean age of air is used to evaluate the natural ventilated efficacy. Following that, the potential of using mechanical vents and slabs to cool equipment work area at this buoyancy driven natural ventilated hall is analysed. The simulation results show that the mechanical vents could decrease air temperature and increase air exchange efficiency at work area effectively on condition that the local airflow pattern is well organized, which is strongly related to the ejection direction and velocity. Present research could benefit future development of the ventilation design in the power plant buildings.

Intensification of Heat Exchange in Laminar Vortex Air Flow in a Narrow Channel with a Row of Inclined Oval Trenches

With the use of multiblock computational technologies, the laminar flow and heat exchange in the modules arranged in a row at regular intervals in a plane-parallel channel, at the centers of which oval trenches oriented at an angle of 45o to the flow are positioned, were calculated at Re = 103. On the basis of the calculation data obtained, it was established that an increase in the maximum velocity of the flow in such a channel by one and a half times leads to the intensification of the heat exchange in it and an increase in the heat transfer from the surface region on its wall with an inclined trench by 80% with an increase in the hydraulic losses by 25%, as compared to those of an analogous smooth channel.

Numerical simulation and analysis of the dynamic finite element model of the fiber motion in the air spinning process

Under the spinning technology of the air-assisted twisting, this paper established the fiber finite element model, which has the structural and dynamic characteristics of the fiber flexible body, based on the space elastic thin rod unit. In this research, we deduced the static equilibrium equation of the fiber finite element model. The nonlinear geometric displacement large deformation problem of the space elastic thin rod unit was treated by the method of stepwise loading successive approximation, and the finite element simulation and analysis of the fiber flexible body’s movement and deformation during the air-jet twisting were carried out and verified by experiment in this paper. This research presents an effective and feasible theoretical model and method for the flexible fiber twisting formation process and mechanism under the high velocity vortex airflow.

Simulation experiments on the controllability of dust diffusion by means of multi-radial vortex airflow

In order to control the diffusion of dusts towards the working area in an excavation face, a novel multi-radial vortex wind generator was designed and developed in this study. Using a self-designed simulation system, the multi-radial vortex airflow migration and dust diffusion rules were experimentally investigated. As to the airflow migration, it was easier to form the dust suppression air curtains with uniform airflow distribution at a longer distance away from the head-on section (Lvortex), under smaller forced-to-exhaust ratio (Y), forced air flow rate (Qforced) and axial-to-radial-ratio (Z), with the airflow pointing to the head-on section. As to the control of dust diffusion, the dust concentration decreased gradually with the increase of Lsection. As the distance away from the head-on section increased, the control capacity of dust diffusion firstly weakened and then strengthened. The smaller values of forced-to-exhaust ratio and axial-to-radial ratio and the larger forced air flow rate would be beneficial to the control of dust diffusion. When the ventilation parameters were reasonably set, the airflow distribution of the dust suppression air curtain, the airflow direction and the hindrance on dust diffusion tended to be stable. Additionally, the optimal ventilation parameters were determined in this study, i.e., Lvortex = 20 m, Y = 5:4, Qforced = 200 m3/min and Z = 1:9. Under the optimal condition, the average removal ratios of total dusts and respirable dusts were as high as 96.02% and 95.51%, respectively.

Research on flow field in a modified ring spinning system with the air nozzle

Twisting is one of the most important steps in the yarn spinning, which influences the geometry of spinning triangle and determines the properties of spun yarns. Airflow is one of the most important measures on improving yarn spinning. In this paper, a kind of air nozzle with vortex guiding channel was designed and used on the modification of ring spinning system, and the spun yarn qualities was studied by analyzing the airflow field in the nozzle. Firstly, the three-dimensional physical model of nozzle was given using CAD software according to the geometrical size of the practical nozzle model. Then, the numerical simulations of the three-dimensional flow field in the nozzle were given using Fluent software. Finally, two different kinds of yarns 10Ne and 20Ne were spun in the modified ring spinning system with the nozzle installed. The airflow pressure 0.01 Mpa and two different swirling directions, anticlockwise and clockwise, were chosen. The qualities of spun yarns, hairiness, strength, evenness, and number of snarling were measured and analyzed. It is shown that the high vortex airflow can be produced in the nozzle, and then corresponding twist can be produced. For the Z(S) twisting spun yarn, under the effects of the clockwise (anticlockwise) vortex airflow, the pre-twisting would be produced and the yarn twist can be strengthened, while under the effects of the anticlockwise (clockwise) vortex airflow, the untwisting effect would be produced, and the yarn twist can be decreased.