Velocity Distribution Of Gas Flow Research Articles

Flow Conditioner Design and Analysis Based on Computational Fluid Dynamics

To address the issue of uneven gas flow velocity distribution upstream of natural gas pipeline flow meters, a wave-type fin flow conditioner was designed. The Computational Fluid Dynamics (CFD) numerical simulation method was used to analyze the velocity distribution inside the pipe, and the rectification effect of the flow conditioner was measured by using the offset degree and the minimum length of the straight pipe section. The offset degree at a specific downstream section was calculated when the fluid passed through a 90 degrees elbow spoiler component without a flow conditioner with an Etoile conditioner and wave-type flow conditioner. The results show that the wave-type flow conditioner has a better rectification effect, and the minimum straight pipe section length is shortened by 72% compared to without a flow conditioner, greatly reducing the pipeline design cost and improving the accuracy of measurement of the Ultrasonic flowmeter.

Outside Front Cover: Plasma Process. Polym. 1/2022

Outside Front Cover: The study demonstrates how UV-Vis spectroscopy can be utilized to investigate the growth and transport of nanoparticles inside a gas aggregation source (GAS). Trapped nanoparticles were found at different positions inside the GAS. With the help of computational fluid dynamic simulations three distinct areas were identified, where nanoparticles can become trapped or lost. The gas flow velocity distribution was found to strongly impact the transport and trapping of nanoparticles. Further details can be found in the article by Jonas Drewes, Suren Ali-Ogly, Thomas Strunskus, Oleksandr Polonskyi, Hynek Biederman, Franz Faupel, and Alexander Vahl (e2100125).

Design of a new gas-dynamic stabilization system for a metal-cutting plasma torch

The analysis of the influence of various design solutions of the gas-dynamic stabilization system in plasma torches for cutting metals on the efficiency of equalizing the velocities of gas flows along the cross-section of the gas path is carried out. It is noted that the efficiency evaluation method developed by the authors should be based on the calculation of the uniformity of the gas flow velocity distribution over the cross-section of the gas-air path of the plasma torch. A vortex stabilization system using two swirlers is proposed. The effect of improving the reliability and quality of plasma cutting is shown. The results of the efficiency studies for the proposed system of gas-vortex stabilization in metal-cutting plasma torches are presented. The calculating results of equalization coefficients for the velocity distribution in different parts of the gas-dynamic stabilization system in the plasma torch are presented. Based on the results of the calculations, a constructive optimization of the gas-air path in the plasma torch was performed. The experimentally obtained advantages of the new upgraded plasma torch in terms of the gas-vortex stabilization efficiency are demonstrated. The effects of improved cutting quality and reduced nozzle wear in the new plasma torch are shown. This is due to the higher degree of the plasma arc stabilization in the new plasma torch, which leads to a decrease in its oscillations, and, consequently, to an increase in the efficiency of the cutting process.

Impact of argon flow and pressure on the trapping behavior of nanoparticles inside a gas aggregation source

AbstractIn this study, in situ UV–Vis spectroscopy is used to investigate the growth and transport of nanoparticles inside a gas aggregation source (GAS) dependent on the Ar gas flow and operating pressure. It was found that the nanoparticles were becoming trapped at different positions inside the GAS dependent on the gas flow. Moreover, in situ UV–Vis spectroscopy suggested the presence of large nanoparticles inside the GAS, which were not observed outside. Computational fluid dynamic simulations were performed to study the velocity distribution inside the GAS. Three distinct areas were identified, where nanoparticles can become trapped or lost. The gas flow velocity distribution was found to strongly impact the transport of nanoparticles.

A RESEARCH OF THE IMPROVEMENT OF THE GAS VELOCITY DISTRIBUTION IN ELECTROSTATIC PRECIPITATOR THROUGH CFD SIMULATION

Electrostatic precipitators (ESP) have been widely used in different fields such as thermal power plants, cement plants, production of constructive materials, chemical industry, fertilizer production, . . . due to their advantagesover other dust collector systems. One of the parameters which influences on dust removing efficiency of the ESP devices is the speed and velocity distribution of the polluted gas in the collecting chamber. This paper presents the research results of improving the uniform distribution of the gas velocity in the collecting chamber of ESP using CFD (Computational Fluid Dynamics) simulation. The simulation results showed that as the dispersion plate was installed at the gas inlet of the collecting chamber the velocity distribution of gas flow was more uniform and its direction was more stable towards the outlet. In addition, the dispersion plate also improved the flow stability at different flow rates and the smaller hole diameter on the dispersion plate was better for the velocity distribution and direction in the flow. The research results provide an approach foroptimum design of a ESP with high collection efficiency.

Experimental and numerical studies on the closed and vented explosion behaviors of premixed methane-hydrogen/air mixtures

The explosion overpressure behaviors of premixed methane-hydrogen/air mixtures in a duct were evaluated by a pressure sensor, while the flame propagation behaviors in the duct and the vented explosion region were captured by a high-speed schlieren camera and a high-speed video camera, respectively. It indicated that the flame front with various concentrations had different development processes. Meanwhile, the velocity of flame front experienced three acceleration processes and explosion overpressure went up three times accordingly. The ratio of the second overpressure peak to the first one increased with the rising methane-hydrogen concentration, which signified that the second explosion severity with higher concentration of methane-hydrogen in the vented explosion region was more drastic than that with lower concentration. In addition, the simulation was applied to reveal the explosion mechanism of premixed methane-hydrogen/air mixtures. The numerical results revealed that the flame shape and pressure dynamic varying processes were corresponding to the experimental results. Besides, the numerical results also yielded several explosion parameters which were difficult to be obtained in the experiments, such as the flame temperature distribution, explosion overpressure distribution, gas-flow velocity distribution, and gas turbulent kinetic energy distribution, whose coupling effect played an important role in the explosion venting.

Temperature influence on the effectiveness of gas-vortex stabilization in plasma torches

The results of the efficiency studies of gas-vortex stabilization systems for metal-cutting plasmatrons are presented. It is noted that the method of efficiency evaluation developed by the authors should be based on the calculation of the uniformity of the gas flow velocity distribution over the section of the gas-heating path of the plasma torch. Various simplified and accurate estimation methods are proposed. The results of calculation of the velocity distribution in the control section for different modifications of plasma torches are presented. Calculations are made on the “cold” model gas flow and its heating by a plasma arc. It is shown that when heated by a plasma arc, the flow rate at the inlet to the nozzle channel of the plasma torch and the degree of irregularity of the velocity distribution in the control section increase. By methods of statistical analysis the main parameter of the effectiveness evaluation of individual gaseous-vortex stabilization was chosen – criterion of the velocity variations. Demonstrated the advantages of the new upgraded torches, including working on technology narrow jet plasma, from the point of view of the effectiveness of gas-vortex stabilization.

Pressure and Gas Flow Distribution Inside the Filter of a Non-Filter Ventilated Lit Cigarette During Puffing

Summary Establishing a realistic gas flow velocity distribution inside a cigarette filter during smoking is important to understand filtration mechanisms of different mainstream smoke species and the overall effect of filter designs on mainstream smoke composition. In this paper, an experimental method is described which directly measures the gas pressure field inside a cellulose acetate filter during cigarette smoking. This was demonstrated by using 3R4F research reference cigarettes smoked under a 35 mL puff of 6 s duration. In addition, filter temperature measurements were also carried out at multiple locations within the filter. Both the temperature and pressure sensing locations were selected to match the radial and longitudinal directions of the cigarette filter. The temperature and pressure measurements were then used to calculate the velocity according to Darcy’s Law along the mainstream flow direction in the cigarette filter at each puff. The spatially resolved maps of temperature, pressure and flow velocity on a puff-by-puff basis provide useful insights into the dynamic filtration of smoke aerosol under the influence of the approaching burning coal and progressive accumulation of smoke particulate matter.

Simulation of Intense Electrohydrodynamic Flow Based on Dielectric Barrier Discharge

This paper presents a numerical analysis of the intense EHD gas flow velocity distribution at atmospheric pressure. The system consists of a coaxial plasma emitter and a collector grid. The ion source is a dielectric barrier discharge distributed over the surface of the emitter. The computational results coincide with the experimental data which allow us to predict the maximum flow rate produced by the experimental setup.

EVALUATION OF FLOW DISTRIBUTION IN THE PELLETIZING FURNACE THROUGH CFD AND EXPERIMENTAL VALIDATION AT SAMARCO

Samarco produces iron ore pellets thermally processed in Travelling Grate furnaces. This process is essential in order to obtain adequate mechanical strength to the pellets transportation and operation in the reduction reactors. All the mechanical properties of the agglomerates are obtained during the stage of firing, being a decisive step to pellet quality. Therefore, the velocity distribution of gas flow within this zone must be homogeneous. For this reason, it was developed a mathematical CFD model to characterize the gas flow in the burning zone, applying the equations of conservation of momentum, mass and energy. The validation of the model was obtained by measuring the temperatures inside the furnace. It was developed a wireless communication system in order to monitor continuously the evolution of the temperatures in the furnace

Numerical Simulation of Gas Flow Field in Gas-Liquid Hydrocyclone Separator

The gas flow field in hydrocyclone separator was numerically simulated by applying RSM turbulence model, and the gas flow velocity distribution and stress distribution were calculated. According to the characteristics of gas flow distribution within the separator, it is found that: (1) the rotating strength of gas flow is related to the outlet angle of guide blade, the greater the outlet angle, the smaller the tangential velocity; (2) the obvious short circuit flow distribution under the exhaust pipe mouth area is easy to carry droplets and roll them out, causing a decrease in separation efficiency; (3) the high strength of turbulence pulse at mouth area of vent and drainage is easy to break the droplets and decrease their diameter, which affects the separation efficiency. The above research results lay the foundation for the structure optimization and the improvement of separation properties of axial guide vane cyclone gas-liquid separator.

Numerical Simulation and Application of Gas Flow Distribution of ESP Transformed to Baghouse in Cement Kiln Head

By using Computational Fluid Dynamics (CFD) method,numerical simulation of gas flow distribution of ESP transform to baghouse in cement kiln head of 6000 t/d production. Through numerically simulation,air volume of every filter bag cell and head-on gas flow velocity distribution of filter bag were displayed. By adjusting the configuration parameter of the gas flow distribution device during the numerical simulation, it gives the result that the manner of installing gas flow distribution device, when the windage of the air volume of every filter bag cell is not more than 5% and the press drop of the dust collector with clean filter bag is 300 Pa. The calculated results showed good agreement with the measured results in the field. The simulation results were carried out by transformation. The dust emission concentration of precipitator is 26.6 mg/m3, and the dust running resistance is less than 1000Pa, can achieve the performance assessment requirements.

Nonequilibrium jet boundary layer in a polyatomic gas

The two-dimensional nonequilibrium hypersonic free jet boundary layer gas flow in the near wake of a body is studied using a closed system of macroscopic equations obtained (as a thin-layer version) from moment equations of kinetic origin for a polyatomic single-component gas with internal degrees of freedom. (This model is can be used to study flows with strong violations of equilibrium with respect to translational and internal degrees of freedom.) The solution of the problem under study (i.e., the kinetic model of a nonequilibrium homogeneous polyatomic gas flow in a free jet boundary layer) is shown to be related to the known solution of the well-studied simpler problem of a Navier-Stokes free jet boundary layer, and a method based on this relation is proposed for solving the former problem. It is established that the gas flow velocity distribution along the separating streamline in the kinetic problem of a free jet boundary layer coincides with the distribution obtained by solving the Navier-Stokes version of the problem. It is found that allowance for the nonequilibrium nature of the flow with respect to the internal and translational degrees of freedom of a single-component polyatomic gas in a hypersonic free jet boundary layer has no effect on the base pressure and the wake angle.

Translationally nonequilibrium free jet boundary layer in the wake behind a wedge

Macroscopic equations obtained as a thin-layer version of the 13-moment Grad equations derived from kinetic considerations are used for describing the translationally nonequilibrium monatomic gas flow in a hypersonic free jet boundary layer formed in the wake behind a wedge. This model makes it possible to investigate flows with strong violations of equilibrium with respect to the translational degrees of freedom. A method of constructing the solution of this kinetically justified problem based on the solution of an analogous problem in the Navier-Stokes interpretation is proposed. It is established that for the kinetic variant of the problem considered the gas flow velocity distribution along the separating streamline in a plane orthogonal to the wedge generator coincides with the distribution obtained in solving the Navier-Stokes variant. It is found that taking into account the nonequilibrium nature of the flow with respect to the translational degrees of freedom of the gas particles has no effect on the base pressure and the wake angle.

FAIMS Operation for Realistic Gas Flow Profile and Asymmetric Waveforms Including Electronic Noise and Ripple

The use of field asymmetric waveform ion mobility spectrometry (FAIMS) has rapidly grown with the advent of commercial FAIMS systems coupled to mass spectrometry. However, many fundamental aspects of FAIMS remain obscure, hindering its technological improvement and expansion of analytical utility. Recently, we developed a comprehensive numerical simulation approach to FAIMS that can handle any device geometry and operating conditions. The formalism was originally set up in one dimension for a uniform gas flow and limited to ideal asymmetric voltage waveforms. Here we extend the model to account for a realistic gas flow velocity distribution in the analytical gap, axial ion diffusion, and waveform imperfections (e.g., noise and ripple). The nonuniformity of the gas flow velocity profile has only a minor effect, slightly improving resolution. Waveform perturbations are significant even at very low levels, in some cases approximately 0.01% of the nominal voltage. These perturbations always improve resolution and decrease sensitivity, a trade-off controllable by variation of noise or ripple amplitude. This trade-off is physically inferior to that obtained by adjusting the gap width and/or asymmetric waveform frequency. However, the disadvantage is negligible when the perturbation period is much shorter than the residence time in FAIMS, and ripple adjustment appears to offer a practical method for modifying FAIMS resolution.

Measurement of gas velocity distribution using a wire-mesh electrostatic probe

A wire-mesh multi-channel electrostatic probe is utilized to determine gas velocity distribution in a small cylindrical metal container. The probe system is developed to implement in the measurement of gas flow in the container; probe fabrication and construction of the measurement system are explained in detail. Also a numerical analysis is conducted to compare the computed velocity profile in radial and axial directions with the measured velocity distribution. An implicit method is implemented to solve a set of motion equations. The velocity distribution of gas flow in the metal container is measured to analyze flow distribution for the understanding of flow pattern in a cylindrical tank which is widely utilized in chemical processes. Comparison between the measured velocity and the computed distribution of gas velocity indicates that the distribution of measured signal agrees with the computational outcome and the measurement system is useful for investigation of gas velocity distribution inside metal containers.

水滴の急加速分裂に関する研究

水滴の分裂は気流の速度分布によって強く影響を受ける。本研究はモデル化したノズル板の端から高速気流によって水滴が離脱, 急加速および分裂する状態を高速度カメラによて調べたものであり, 次の内容について考察している。a) 発生水滴径および分裂までの距離の気流速度による影響, b) 水滴の加速の状態, およびc) 分裂開始時のウェーバ数。ここで, 水滴の変形から分裂までの過程には2つの形態がみられ, 分裂開始時のウェーバ数は一様な平行気流中のものよりも広範囲に分布し, また比較的大きな値を示している。

超音波の非線形効果を用いた気体の流速分布計測系による流れの場の観測例

超音波の非線形効果を用いた気体の流速分布計測系による流れの場の観測例

超音波の非線形効果を利用した気体の流速分布計測系の高精度化

超音波の非線形効果を利用した気体の流速分布計測系の高精度化

Study on the Characteristics of Small Cyclone Separator (1st Report) : Experiments on a Small Multiclone-type Unit Cyclone

This paper presents the experimental results on a small multiclone-type unit cyclone with a dia. of 30 mm, which is connected to the suction side of high speed motor fan, in order to investigate the characteristics of small cyclone separator using to measure the dust content of flow-gas. From the test results, we assumed that, the entering stream in the annular space above the bottom of the exit pipe flows down forming a forced voltex flow, and below the bottom of the exit pipe, its flow changes to a double eddy type flow consisting of an outer downward free voltex and an inner upward combined voltex such as Rankine's flow. The tangential velocity distribution of gas flow above and below the bottom of the exit pipe may be given by the following expression. vi=c/rn The value of n determined in the present experiment is 0.5∼-1. The test cyclone has shown that the separating eff. exceeds 99% for nealy all kinds of industrial dust particles with a dia. of between 0.7∼1.0 micron, and slightly more increases than with no an enlarged dust hopper. We compared the partial separating capacity at various points in cyclone with the total separating eff. by injecting known quantities of dust at these points and determined the equal partial eff. distribution curve.