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The study of the movement of pollutants through ducts facilitates the assessment and control of ambient air quality problems (AQ). Among other things, understanding the deposition and distribution of particulate matter in elbows is important for practical engineering applications. In this study, the turbulent flow field and particle deposition in a 90° bend is investigated using RANS simulation. The RNG k-ε turbulence model was employed to calculate the airflow flow field and the discrete phase model (DPM) was used to simulate the particle phase motion. Where for the discrete phase, the Discrete Random Wander (DRW) model was considered and the deposition of particles with sizes of 1, 3, 5, 10, 20, and 40 μιτι in the flow field was investigated separately. Grid-independent validation of the models used in the simulations was performed. The effects of inlet velocity, particle size, and direction of gravity on the flow field and particle deposition in the elbow were considered. The results show that the flow field in the bend is strongly influenced by the above parameters. Among them, the turbulent disturbance in the bend section is the most intense, with high turbulent energy value, and it is also the region with the largest energy loss. The inlet velocity is negatively correlated with the deposition rate, and the particle size is positively correlated with the deposition rate. [ABSTRACT FROM AUTHOR]

In the process of laser cladding, there are usually problems such as powder plugging and uneven delivery, which affect the quality of the final cladding layer. Therefore, powder convergence characteristics in laser cladding need to be further improved. Gas–solid two-phase flow technology has been widely used in the study of powder flow characteristics because it can precisely regulate the interaction between carrier air and powder flow. In this paper, we systematically review the current status of gas–solid two-phase flow in the field of laser cladding powder, deeply analyze the latest optimization progress of laser cladding nozzle design, and comprehensively explain the key progress of gas–solid two-phase flow technology in improving the uniformity and efficiency of powder field distribution. At the end of this paper, the research results are summarized and a series of prospective prospects are proposed, aiming to provide a valuable reference framework and directional guidance for the subsequent related research. [ABSTRACT FROM AUTHOR]

This study proposed a new cyclone separator, using a designed nozzle inside the traditional cyclone separator, which significantly improved the efficiency of separating fine particles while maintaining an essentially unchanged pressure drop. Firstly, computational fluid dynamics (CFD) was used to compare the flow characteristics of the new cyclone separator with those of the traditional cyclone separator. On this basis, this study comprehensively investigated the pressure drop and separation efficiency of two separators under varying working conditions. The new separator achieved a separation efficiency for particles with a particle size of 1 μm that was approximately 45% higher than that of the traditional separator when the inlet velocity was 2–10 m/s. Besides, the pressure drop of the cyclone separator remained unchanged while the separation efficiency increased by 46% at an inlet flow rate of 2 m/s. The influence of the outlet area of the nozzle inside the new cyclone separator on the separation efficiency and pressure drop was analyzed, and the outlet area of the nozzle with the best overall performance was determined. It was found that the overall performance of the new cyclone separator is optimal when the nozzle outlet area is S/f = 2 cm. Finally, an energy-saving cyclone separator with high separation efficiency was developed through an in-depth study of the variation of particle motion configuration with time. It is worth noting that this study provides a guidance for the flow field analysis and geometry optimization of new gas-solid separators, not limited to cyclone separators.

In order to understand the behavior of gas-solid two-phase flow motion and the process of pulverized coal separation in coal mill separator, the numerical simulations on the gas-solid two-phase flow in the separator of a laboratory-scale coal mill were carried out. In the framework of the Eulerian-Lagrangian method, the realizable k-ɛ turbulence model was used to describe the gas-phase field and the discrete phase model with the random walk model was used to describe the pulverized coal particle motion in the simulations. On the basis of cell independence verification, the results of one-way coupling and two-way coupling simulations were compared with the experiments. It is found that the particle size distribution of pulverized coal obtained by the two-way coupling method agrees better with the experimental data than that obtained by the one-way coupling method. The gas phase flow behavior, particle motion characteristics and separator performance in the laboratory-scale coal mill separator were further investigated using a two-way coupling method. The results show that the particle overflow occurs later and the overflow lasts longer when using the two-way coupling method. Because of the effect of particles, the airflow velocity difference between the inner wall of the separator and the outer wall of the inner cone of the separator becomes large, and the uniformity of airflow velocity distribution in the inner cone becomes poor, and there are obvious backflow regions in the primary and secondary separation zones. With the increase of the inlet airflow velocity, the particle overflow rate increases, and the particle discharge rate decreases linearly. The inlet airflow velocity has a small influence on the total particle return rate but has a profound influence on the grade return rate. The grade return rate exhibits a unimodal distribution at the lower airflow velocity, and it displays a bimodal distribution at the higher airflow velocity. When the inlet airflow velocity remains constant, the grade separation efficiency increases as the particle diameter increases. The greater the inlet airflow velocity, the slower the grade separation efficiency increases with the particle diameter, and the larger the cut-off diameter of the separator.

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Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium 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.)

The transport and deposition of particles accompanying the heat setting process in the opposed jet air supply system have a significant impact on the equipment safety. This paper used the Realizable k–ε model to simulate the flow field distribution of the impinging jet and the Lagrange method to track the trajectory of particles, by considering factors, such as jet velocity (7–13 m/s), oven temperature (413–473 K), and particle size (1–30 μ m) changes, the instantaneous force process of particles was analyzed and their deposition mechanism was revealed. The numerical results have been well validated, with the root mean square error of within 10%. The results indicate that the flow field form of the opposed jet significantly affects particle placement on the surface of the air duct, the maximum turbulent vortex structure appears at the inlet of the air duct on both sides of the protruding nozzle, enhancing the capture of particles. Under the influence of gravity, the lower surface of the air duct becomes the main deposition surface, this phenomenon becomes more pronounced as the particle size increases and the maximum deposition rate difference between the upper and lower layers is 37%. The number of particles deposited on the rear end of the air duct is greater than that on the front end, and the deposition rate decreases with the increase in jet velocity. In the initial stage, a temperature gradient appeared in the machine room, which provided upward lift for the particles, resulting in more small diameter particles ( d p < 10 μ m) depositing on the upper surface of the air duct. The results can provide theoretical support for the fire prevention and pollutant purification of equipment, such as heat setting machines. [ABSTRACT FROM AUTHOR]

The use of glass fiber-reinforced polymer (GFRP) composites in fluid transport systems can effectively reduce corrosion damage caused by corrosive media. However, collisions between solid particles and the surfaces of ball valve flow passages can cause erosion damage and lead to safety issues. The two-phase flow and erosion characteristics of ball valves manufactured from resin-based fiber-reinforced composite materials were studied under different openings and particle sizes using the CFD-DPM method. The results indicate that both smaller and larger relative openings are prone to erosion damage at the thin edges of the valve ball. As the relative opening increases, the average erosion amount in the flow passage first increases and then decreases. The maximum average erosion amount is 0.0051 kg/m2·s when the relative opening is Cv = 40. At Cv = 40, erosion damage in the flow channel mainly occurs at the bottom of the inlet flow channel and the valve seat position. With increasing particle size, both the average and maximum erosion amounts in the flow channel increase. Larger particle sizes in the inlet flow channel significantly raise the erosion rate nearby, while at other locations, larger particle sizes mainly increase the erosion rate in the same area. During the use of GFRP valves, it is important to avoid introducing large-sized particles into the medium. Keeping the valve's relative opening greater than 40 and using more erosion-resistant materials for the valve seat can effectively reduce the erosion of the composite ball valve and extend its service life. [ABSTRACT FROM AUTHOR]

Biomass energy is one of the most important eco-friendly renewable resources to reduce environmental pollution. The effective pyrolysis in a down-tube structure reactor can directly catalyze the production of bio-oil from biomass, in order to recycle the heat carriers. Among them, the flow patterns of particles are crucial to optimize the efficiency of the down-tube operation and the quality of the bio-oil products. This study aims to clarify the flow patterns of ceramic beads and biomass particles within different down-tube structures. A comparative study was conducted on the impact of square and round downtubes on particle axial velocity, particle collision rates, and biomass residence time in a cold state. Additionally, a systematic investigation was implemented to examine the effect of tube diameter on particle axial velocity and biomass residence time. A CFD-DEM coupled computational framework was established, where the fluid part used the FLUENT software for CPU multicore parallel computation, and the solid particles were simulated using EDEM software. The simulations were velocity-validated using particle image velocimetry (PIV). The experimental results showed that better performance was achieved in the consistent test and simulation velocity for ceramic beads. In terms of electrostatic effects, the experimental velocity of biomass particles was consistently lower than the simulated one. However, the difference in velocity between biomass in simulations and experiments was kept within a narrow range after electrostatic removal operations on the down-tube walls, fully meeting experimental requirements. The structural differences in the down-tubes depended on the flow of particles. The mixed particles exhibited higher time-averaged axial velocities in round tubes than those in square ones. Particularly, the maximum axial velocity of ceramic beads in round tubes was about 10% higher than in square ones. The difference was observed in the particle axial velocity at the bends of the down-tubes under different tube diameters. The velocity of ceramic beads decreased by approximately 37%, 40%, and 45% at 60, 70, and 80 mm diameters, respectively; The biomass velocity decreased by about 49%, 52%, and 54%, respectively. The ceramic beads were introduced to change the comparative flow velocities of biomass particles in square and round tubes. The biomass velocity in round tubes was greater than that in square tubes. The ceramic beads reduced the flow velocity of biomass. The maximum axial velocity of biomass decreased by 41% and 33%, respectively, in both types of tubes. In square tubes, the biomass had a higher frequency of contact collisions with the walls, where about 23% of biomass particles were contacted with the ceramic beads, primarily flowing along the walls. In round tubes, there was a higher frequency of contact collisions between biomass and ceramic beads, where about 39% of biomass particles were contacted with the ceramic beads, resulting in a more uniform distribution of biomass and movement in the central part of the tube. Biomass particles shared a larger average residence time and more concentrated distribution in square tubes, compared with the round tubes. The ceramic beads were introduced to increase the dispersion of biomass residence time distribution, which increased by 10% and 17% in the square and round tubes, respectively. The findings can provide a strong reference for the particle flow states in the down-tube pyrolysis devices, in order to better design and optimize the down-tube structures. [ABSTRACT FROM AUTHOR]

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. 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.)

Erosion wear is a kind of material wear phenomenon caused by the interaction between solid surface and fluid containing solid particles with a certain velocity, which exists widely in industrial production and is an important reason for failure and damage to many mechanical devices. Especially under gas-solid two-phase flow conditions, bent pipes suffer from severe erosion wear, greatly reducing their service life and even causing major safety accidents. In order to provide reference for the study of erosion wear and anti-erosion wear of equipment under multiphase flow conditions, this article reviewed the current research status and progress on erosion wear of bent pipes under gas-solid two-phase flow conditions in recent years. Moreover, the main methods currently used to study the erosion wear of gas-solid two-phase flow bends were described, the advantages and disadvantages of commonly used experimental research equipment and numerical simulation methods were summarized emphatically. At last, the prospects for future research on erosion wear of bent pipes under gas-solid two-phase flow conditions were presented.

Coal particles carried by the gas extraction flow are easy to be deposited in the mining-induced fracture, which seriously reduces the flow rate of gas extraction. Mastering the deposition characteristics of particles in the fracture is an important basis for improving the flow rate of gas extraction. In this paper, we carried out a particle transport and deposition experiment in the fracture with a shrinkage, and studied the particle deposition bed evolution law after crossing the shrinkage under the influence of the gas extraction flow. In addition, we analyzed the influence of the gas velocity and shrinkage structure parameter on the particle deposition law of the back end of the shrinkage of the fracture and the local resistance of the gas flow. The results show that the granular sedimentary bed at the back end of the fracture shrinkage shows two kinds of evolution patterns. When the particle deposition bed is distributed in a “V” shape along the airflow direction, the deposition height of the granular deposition bed shows an evolution pattern of rapid increase followed by a slow decrease. When the depositional zone is a “Ʌ” shaped deposition along the direction of flow, the depositional height shows an evolutionary pattern of slow increase and then slow decrease. In addition, with the development of the particle bed in the fracture, the local resistance changes at the back end of the fracture shrinkage can be divided into the initial stabilization stage, the rapid development stage and the final stabilization stage. The evolution time of the initial stabilization stage is shortened with the increase of the pumping rate or the decrease of the shrinkage ratio. The evolution time of the rapid development stage is shortened with the increase of the pumping rate or the increase of the shrinkage ratio.

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. 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.)

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. 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.)

Traditional fossil energy sources still dominate the world energy structure. And fully utilizing biomass is a viable approach for energy transition. A bubbling fluidized bed has better heat and mass transfer, while particle agglomeration limits the development of its industrial application. In this paper, two-phase flow characteristics of a bubbling fluidized bed are investigated by combining numerical simulations and fluidized bed gasification experiments. Numerical simulations found that the bed fluidization height reached twice the initial fluidization height at the 0.054 m initial fluidization height with uniform particle distribution. Fluidized bed gasification experiments found that syngas yield increased with increasing temperature. The carbon conversion efficiency reached 79.3% and the effective gas production was 0.64 m3/kg at 850 °C. In addition, when the water vapor concentration reached 15%, the carbon conversion efficiency and effective gas production reached the maximum values of 86.01% and 0.81 m3/kg, respectively. [ABSTRACT FROM AUTHOR]

BACKGROUND: The current study introduces a novel infrared‐assisted spouted bed drying technique for the dehydration of green soybeans, which aims to enhance the drying quality and efficiency. The investigation involves an examination of the flow pattern in the spouted bed to obtain relevant data, followed by an optimization of the entire drying process. The drying process of green soybeans was simulated using SolidWorks and ANSYS Fluent software, based on the principles of computational fluid dynamics. RESULTS: The simulation test results showed that the simulation outcomes were consistent with the experimental data. The optimal conditions for the process of green soybean infrared‐assisted spouted bed drying were found to be an inlet speed of 8 m/s and a temperature of 50 °C with the wavelength and power settings of the infrared board at 10 μm and 500 W, respectively. CONCLUSION: The simulation method selected in this article, based on gas–solid two‐phase flow dynamics, is feasible for green soybean infrared‐assisted spouted bed drying process. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In order to explore the mechanism of dust escape during the unloading process of grab buckets and solve the problem of severe dust escape during the current port material transportation process, an online testing experimental platform for the escape airflow of grab bucket unloading was built. A combination of experiments and numerical calculations was used to explore the mapping coupling relationship between the impact of unloading height and unloading mass flow rate on the escape airflow velocity inside the hopper by taking typical main grain particles as unloading objects based on the gas-solid two-phase flow theory, and derive the critical particle size for dust escape based on the motion characteristics and laws of the dust particle escape process. The research results indicate that the peak velocity of the escaping airflow is positively correlated with the unloading height. At the same unloading height, the peak value of the escaping airflow is in a power function relationship with the mass flow rate; Based on the force acting on powder particles, a formula for calculating the critical particle size of dust particles escaping is derived, and the calculation error of the formula is verified to be within 11%; Based on experimental data, the critical particle size ranges for dust particle escape during unloading of soybeans, corn, and wheat are 160.9~292.5,182.6~359.6,95.1~196.1 μm. The research provides theoretical support for dust control and dust suppression device design in the process of grab bucket bulk grain unloading. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive numerical investigation of erosion in bends equipped with inner rings as a novel geometric concept for erosion control. The research aims to assess the effectiveness of these innovative configurations in reducing erosion through rigorous computational fluid dynamics (CFD) simulations. Numerical modeling for the gas-solid two-phase flow has been carried out based on one-way coupling using an Eulerian-Lagrangian approach. The CFD model employed in this work incorporates the RNG k-ε turbulence model for flow solution, the Oka model for simulating surface erosion, and the Grant and Tabakoff model to account for particle-wall collisions. The primary focus of the investigation is to evaluate the erosion reduction capabilities of different inner ring configurations. By systematically varying the number of inner rings, the study elucidates the influence of this parameter on erosion mitigation. The obtained numerical results are analyzed in terms of erosion patterns, erosion reduction percentages, and the integral erosion surface criterion. The findings reveal the elbow with two separate inner rings as the most effective configuration, exhibiting a remarkable decrease in erosion of up to 43 % compared to the standard elbow. Moreover, based on the integral erosion surface criterion, the elbow with five separate inner rings emerges as a more desirable alternative to the standard elbow. In addition, the study investigates the impact of an elbow with helical inner rings configuration on erosion. It is observed that this configuration intensifies flow velocity, thereby accelerating particle motion and leading to increased erosion along the outer wall.

The shot blasting machine recovery device is an important part of the operation of the shot blasting machine to recover solid particles and reduce environmental pollution. The recovery efficiency of solid particles has an important influence on their processing efficiency and service life. The computational fluid dynamics and discrete element method (CFD-DEM) simulation method is applied to study the gas-solid two-phase flow characteristics and solid particle recovery efficiency of shot pellet recovery unit. The results show that the simulation results of outlet and inlet wind speeds and pressures are in good agreement with the experimental data, which verifies the accuracy of the simulation model. The existence of particle phase divides the recovery pipeline into inner high-speed flow area and outer low-speed flow area, which has little influence on the air flow distribution inside the recovery bin. The results of solid particle recovery efficiency show that with the increase of incident angle, the recovery efficiency of waste particles and shot particles first decreases and then increases, and the recovery efficiency is the lowest when the incident angle is 30°. With the increase of particle formation rate, the efficiency of shot recovery first increases and then decreases. When the particle formation rate is 2000 n/s, the efficiency of shot recovery is the highest, which has little influence on the efficiency of waste recovery. [ABSTRACT FROM AUTHOR]

The Eulerian–Lagrangian method was used to establish a numerical model of a multi-elbow pipeline erosion and examine the erosion of the relief line elbow under supercritical conditions. The model was used to examine the effects of the discharge volume, sand content, and shape factor of sand on multi-elbow erosion and those of the connection length on double-elbow erosion. The erosion mechanism and law of multi-elbow lines under gas–solid two-phase flow conditions were revealed. The results indicated that the most severe erosion of the elbow occurred on the impact surface. However, the erosion area of the multi-elbow was relatively long. In a multi-elbow pipeline, the maximum erosion rate of the outlet elbow was 84 times that of the inlet elbow. For the multi-elbow pipeline, the erosion rate was related to the discharge volume, sand content, particle shape, and length of the connection between elbows. The erosion rate of the elbow at the outlet decreased gradually and stabilized with an increase in the connection length. [ABSTRACT FROM AUTHOR]

The study of the movement of pollutants through ducts facilitates the assessment and control of ambient air quality problems (AQ). Among other things, understanding the deposition and distribution of particulate matter in elbows is important for practical engineering applications. In this study, the turbulent flow field and particle deposition in a 90° bend is investigated using RANS simulation. The RNG k-ε turbulence model was employed to calculate the airflow flow field and the discrete phase model (DPM) was used to simulate the particle phase motion. Where for the discrete phase, the Discrete Random Wander (DRW) model was considered and the deposition of particles with sizes of 1, 3, 5, 10, 20, and 40 μm in the flow field was investigated separately. Grid-independent validation of the models used in the simulations was performed. The effects of inlet velocity, particle size, and direction of gravity on the flow field and particle deposition in the elbow were considered. The results show that the flow field in the bend is strongly influenced by the above parameters. Among them, the turbulent disturbance in the bend section is the most intense, with high turbulent energy value, and it is also the region with the largest energy loss. The inlet velocity is negatively correlated with the deposition rate, and the particle size is positively correlated with the deposition rate.

The dust in the main well tower seriously affects the health of the staff in the well tower and the safe and stable operation of the equipment. In order to reduce the dust diffusion effect in the well tower and further reduce the dust concentration in the well tower, the dust migration trajectory in the main hoisting shaft of Dongtan Coal Mine was studied, and the Eulerian-Lagrange method was used to study the gas-solid phase in the well tower. The average error of the numerical calculation method is 5% compared with the actual measured data in the field, and the numerical simulation method is reliable. The study found that the airflow in the tower produced swirling flow, and the static pressure of the airflow was clearly demarcated on the 8th floor. With the increase of floors, the proportion of PM2.5 gradually increased, especially in the 7th floor area, the proportion of PM2.5 was as high as 90%.

In the process of laser cladding, there are usually problems such as powder plugging and uneven delivery, which affect the quality of the final cladding layer. Therefore, powder convergence characteristics in laser cladding need to be further improved. Gas–solid two-phase flow technology has been widely used in the study of powder flow characteristics because it can precisely regulate the interaction between carrier air and powder flow. In this paper, we systematically review the current status of gas–solid two-phase flow in the field of laser cladding powder, deeply analyze the latest optimization progress of laser cladding nozzle design, and comprehensively explain the key progress of gas–solid two-phase flow technology in improving the uniformity and efficiency of powder field distribution. At the end of this paper, the research results are summarized and a series of prospective prospects are proposed, aiming to provide a valuable reference framework and directional guidance for the subsequent related research.

The use of glass fiber-reinforced polymer (GFRP) composites in fluid transport systems can effectively reduce corrosion damage caused by corrosive media. However, collisions between solid particles and the surfaces of ball valve flow passages can cause erosion damage and lead to safety issues. The two-phase flow and erosion characteristics of ball valves manufactured from resin-based fiber-reinforced composite materials were studied under different openings and particle sizes using the CFD-DPM method. The results indicate that both smaller and larger relative openings are prone to erosion damage at the thin edges of the valve ball. As the relative opening increases, the average erosion amount in the flow passage first increases and then decreases. The maximum average erosion amount is 0.0051 kg/m2·s when the relative opening is Cv = 40. At Cv = 40, erosion damage in the flow channel mainly occurs at the bottom of the inlet flow channel and the valve seat position. With increasing particle size, both the average and maximum erosion amounts in the flow channel increase. Larger particle sizes in the inlet flow channel significantly raise the erosion rate nearby, while at other locations, larger particle sizes mainly increase the erosion rate in the same area. During the use of GFRP valves, it is important to avoid introducing large-sized particles into the medium. Keeping the valve’s relative opening greater than 40 and using more erosion-resistant materials for the valve seat can effectively reduce the erosion of the composite ball valve and extend its service life.

In this paper, the Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) coupling method was used to simulate the pneumatic transport of pebble particles in a three-blade spiral tube. The results showed that the flow field distribution rotated along the circumference after loading. The maximum velocity of the flow field after loading was manifested as rotation along the circumference. In addition, the swirl intensity decreased exponentially with the increase in conveying distance, and the maximum swirl intensity had a saturation value. After reaching the saturation value, it is not evident that increasing the initial air velocity significantly affected swirl variation. The smaller the pitch, the greater the initial swirl intensity. The swirling flow was conducive to the fluidization of particles, but it would bring a significant energy loss. Increasing the swirl can increase the degree of particle dispersion. There is an optimal tangential airflow velocity, which allows the particles to fully spin and stay in the suspension zone without being thrown onto the pipe wall by excessive centrifugal force. At this time, the energy efficiency reaches the highest level. A 5.87 m/s velocity was deemed the optimal tangential airflow velocity for conveying 3 mm particles. [ABSTRACT FROM AUTHOR]

The gas–solids flow in an industrial‐scale semi‐dry method desulphurization tower is simulated by the computational particle fluid dynamics (CPFD) approach. Compared with previous studies on desulphurization towers, this study focuses on analyzing particle distribution characteristics such as particle volume fraction, temperature distribution, and residence time. The simulation fully considered the particle–fluid, particle–particle, and particle–wall interactions in the desulphurization tower. Based on these considerations, the effects of flue gas inlet velocity and temperature on the gas–solid distribution characteristics of the desulphurization tower are simulated. An optimization scheme for adjusting the gas–solid flow in the desulphurization tower is proposed. The research results show that the error between the CPFD simulation data and experimental data is small and the changing trend is consistent. The particles in the bed of the desulphurization tower show a typical core–annulus flow. The distribution of gas and particles in the bed has a serious deviation with the increase of the flue gas inlet velocity and temperature. As the axial height of the desulphurization tower increases, the flue gas velocity, temperature, particle concentration, and water vapour distribution in the bed become more uniform. The relatively stable operating conditions for the gas–solid flow in the desulphurization tower is that the flue gas inlet velocity and temperature are 15 m/s and 393 K, respectively. Under these operating conditions, the pressure loss caused by the venturi accounted for 73.6% of the total pressure loss of the desulphurization tower. When the particle radius is between 0–150 μm, the particle size and the flue gas inlet velocity have the greatest influence on the particle residence time. Finally, the distribution of gas and particles before and after the adjustment of the desulphurization tower is compared, which showed that adjusting the bottom structure of the desulphurization tower could optimize the gas–solid flow. [ABSTRACT FROM AUTHOR]

This paper uses the SPH method to study snow disasters, including the snow flow model of a vertical water diffusion equation and heat balance equation. The advantage of the SPH method is that it can capture particles' positions, which can be used to track the initial position distribution of hazardous particles. At the same time, a particle modeling method based on pixel value is proposed, which has certain advantages in dealing with the boundary modeling of different materials. In addition, snow disaster prevention and the control of classic embankment and cutting procedures were carried out. The final treatment results showed that the number of snow particles on the subgrade surface was reduced by about 90%. The validity and feasibility of the snow disaster simulation software based on the SPH method are verified by comparison with the experimental results. [ABSTRACT FROM AUTHOR]

The correction notice in the journal "Frontiers in Energy Research" addresses errors in affiliations, authorship, and funding in the article "A CFD numerical simulation of particle deposition characteristics in automobile tailpipe: power abatement pathways." The corrections include clarifying the affiliations of the authors, updating the author list, and rectifying the funding statement. The authors acknowledge the errors and assure that they do not impact the scientific conclusions of the article. The original article has been amended accordingly. [Extracted from the article]

Traditional fossil energy sources still dominate the world energy structure. And fully utilizing biomass is a viable approach for energy transition. A bubbling fluidized bed has better heat and mass transfer, while particle agglomeration limits the development of its industrial application. In this paper, two-phase flow characteristics of a bubbling fluidized bed are investigated by combining numerical simulations and fluidized bed gasification experiments. Numerical simulations found that the bed fluidization height reached twice the initial fluidization height at the 0.054 m initial fluidization height with uniform particle distribution. Fluidized bed gasification experiments found that syngas yield increased with increasing temperature. The carbon conversion efficiency reached 79.3% and the effective gas production was 0.64 m3/kg at 850 °C. In addition, when the water vapor concentration reached 15%, the carbon conversion efficiency and effective gas production reached the maximum values of 86.01% and 0.81 m3/kg, respectively.

Asthma is a common respiratory disease with symptoms such as repeated wheezing, shortness of breath, and coughing. However, currently, asthma cannot be cured but only controlled or relieved using medication. The metered-dose inhaler (MDI) is known to lead to high deposition fractions of drug particles in the mouth and throat, resulting in inadequate drug efficacy. Therefore, herein, the factors influencing the deposition fraction of asthma drugs in the mouth and throat regions were explored by computational fluid dynamics and a smart MDI for asthma was designed. The smart MDI was designed based on the obtained simulation results, which demonstrated that the deposition fraction gradually increased from 55.78% to 65.75% with an increase in the peak inspiratory flow rate at an angle of incidence of 0°. The deposition fraction first decreased and then increased as the angle of incidence increased at a constant peak inspiratory flow rate. The deposition fraction increased as the inspiration–press interval time increased at a constant angle of incidence and peak inspiratory flow rate. Meanwhile, performance analysis of the designed smart MDI indicated that the inhaler could effectively reduce the deposition fraction of drugs in the mouth and throat regions by 17% on average. [ABSTRACT FROM AUTHOR]

Understanding particle flow characteristics can help improve the efficiency of nonmetallic ore powder air classifiers. In this paper, dissipative particle dynamics (DPD) and the discrete element method (DEM) were adopted to study the interactions between the gas phase and solid particles. Gas and solid phases were coupled using the single-particle DPD model. Taking sepiolite particles as an example, at the optimal input air velocity in the pipeline, the gas particle velocity distribution, solid particle velocity distribution, solid particle concentration distribution, and solid particle position distribution were analyzed by numerical simulations. A comparison of numerical simulation and experimental results showed that when the input air velocity U a in the pipeline was 17 m/s, the velocity of particles and gas in the pipeline gradually increased from the wall to the center of the pipeline. The velocity near the pipeline wall changed rapidly, and the velocity in the main flow area remained basically unchanged. Particles left the pipeline in a uniform and dispersed state and were carried into the classification area. As the input air velocity increased, the pressure drop across the pipeline also increased. Therefore, the optimal input air velocity value could be reasonably selected to minimize energy consumption. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. 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.)

Fluidized bed is the main reactor for the heating and gasification of coal, biomass, and other solid fuels. The diameter, density, and shape of the particles significantly affects the gas–solid​ two-phase flow process. Based on the numerical method combining computational fluid dynamics and discrete element method (CFD–DEM), this paper mainly performs numerical simulation on the gas–solid two-phase flow process of coarse particles under different inlet mass flow rates with diameters of 2.5 mm, 3.0 mm, and 3.5 mm, respectively. The high-speed photographic experiments were carried out to validate the numerical results successfully. The effects of particle diameter on bubble morphology have been compared, such as bed height and initial bed mass change rate. The maximum value of the bed height reached gradually decreases as the particle diameter increases. Two typical C-shaped bubbles were found above the large bubbles during the fluidization processes, which further improve the uniformity of mixing. Slugging appears as the width of the bubbles in the fluidized bed is close to the width of the fluidized bed, which has great effects on the mass and heat transfer. This study could serve as reference for further optimal design of fluidized bed, especially for biomass or chemical looping combustion application with coarse particles.

Mechanical impact superfine grinder is characterized by the wide working condition, high efficiency, and simple operation. The vertical mechanical impact superfine grinder has been commonly used to crush agricultural by-products in recent years. However, the processed material often contains coarse particles with a wide distribution range, due to the current classification chamber structure. The classification performance can also depend mainly on some changes in the vertical position relationship between the current-guide cover and the classification wheel. In this study, two optimization schemes were proposed for the classification chamber using the initial structure, in order to examine the influence of different position relationships on classification performance. Optimized structure 1 involved the current guide that attached to the upper cover, thereby blocking the flow path between them, while maintaining the height of the classification wheel blades. Optimized structure 2 retained the original position of the current-guide cover in consistence with the initial structure, but increased the height of classification wheel blades. Additionally, 3mm was adjusted for the distance between the top edge of the classification wheel blades and the bottom of the discharge port. Firstly, the performance tests were conducted on three classification chamber structures. Secondly, the CFD software and numerical simulation of gas-solid two-phase flow were employed to analyze the flow of fluid within the classification chamber. Finally, the simulation was used to explain the test findings. The following conclusions were also drawn. Optimized structure 1 yielded a more uniform clipping velocity outside of the classification wheel. However, there was a small variation gradient of axial velocity and flow field velocity in the classification chamber. Consequently, the product with the smaller median particle size was obtained in the optimized structure 1, compared with the others. Classification efficiency and accuracy were only changed slightly. The optimized structure 1 resulted in the absence of large particles in the products, due to the blocked flow path in the attachment of the current-guide cover to the upper cover. Meanwhile, the radial velocity decreased gradually from the outer to the inner of the grading wheel in the optimized structure 2. The reverse vortices were generated between the grading wheel blades, leading to a more uniform axial velocity distribution within the grading wheel and a significant variation gradient of axial velocity and flow field velocity within the classification chamber. Consequently, the product with a larger median particle size was yielded, compared with the others, whereas, the classification efficiency and accuracy were enhanced significantly. Moreover, the increasing height of the grading wheel blades impeded the entry of large particles into the finished material. The reason was that the higher tangential velocity outside the grading wheel promoted the material dispersion and the ejection of large particles. In summary, both optimized structures 1 and 2 resulted in the products devoid of large particles. A comparative analysis was performed on the three classification performance indexes, namely product particle size, classification efficiency, and classification accuracy index. Therefore, the optimized structure 2 demonstrated better classification accuracy and efficiency than before, although was yielded a coarser product particle size. Conversely, the optimized structure 1 enabled the production of ultrafine powder with a smaller particle size, although at the cost of lower classification efficiency. The findings can provide a strong reference and theoretical foundation for the flow field investigation and structural optimization of the classification chamber in the CWFJ vertical mechanical superfine grinder. [ABSTRACT FROM AUTHOR]

Aiming at the problem of blade erosion of a mining counter-rotating fan in actual operation, the SST k-w turbulence model and the Finnie erosion model were used to numerically simulate the gas-solid two-phase flow field of the fan at different blade installation angles. Firstly, fan performance tests were carried out with fan static pressure, fan power and fan efficiency as evaluation indexes, and the accuracy of the numerical calculation methods and models was verified. Then, the erosion characteristics of the blade pressure surface and the distribution patterns of the gas-solid two-phase flow field of the fan were analyzed according to the six designed blade installation angle cases. Finally, the performance parameters of the gas-solid two-phase flow fan with different blade installation angles were compared, and the blade installation angle with the best anti-erosion effect and the optimum fan performance was determined. The results show that the average erosion rate of the blade surface is reduced by 6.0 x 10-8 kg/(m² s) after increasing the rear stage blade installation angle compared to the original blade installation angle. Increasing the rear stage blade installation angle reduces the separation vortex at the leading and trailing edges of the rear stage blade, improves the fan performance, and achieves the purpose of blade anti-erosion. [ABSTRACT FROM AUTHOR]

When using valves and pipes, erosion wear is a major issue. Erosion wear can result in equipment shutdown, material replacement, and other issues, as well as the failure of sealing surfaces. The depth of erosion wear is primarily determined by particle velocity, particle size, target material, and use conditions. A combination of the discrete element method (DEM) and computational fluid dynamics (CFD) was used in this study. The dynamic process of particle collision with the sealing surface is also considered. The wear depth was then calculated using Archard's abrasive wear theory. The erosion wear process of the graphite-sealing surface by gas-solid two-phase flow medium is numerically simulated in a high-temperature triple eccentric butterfly valve using the above theory and method. The erosion wear patterns of graphite-sealing surfaces were investigated under various particle velocities, particle sizes, target materials, and service conditions. The findings indicate that particle velocity and particle size are positively related to wear rate. Soft target wear depth is greater than hard target wear depth. The wear depth decreases as the ambient temperature rises. As a result, graphite has excellent resistance to erosion and wear at high temperatures. When feeding, however, particle velocity and particle size must be considered. The erosion wears characteristics of a high temperature three eccentric butterfly valve investigated in this paper can be used to optimize erosion wear prevention. [ABSTRACT FROM AUTHOR]

The two-dimensional distribution of gas-solid flow parameters is a great research significance to reflect the actual situation in industry. The commonly used method is the ultrasonic tomography method, in which multiple probes are arranged at various angles, or the measurement device is rotated as that in medicine, but in most industrial situations, it is impossible to install probes at all angles or rotate the measured pipe. The backscattering method, however, uses only one transducer to both transmit and receive signals, and the twodimensional information is obtained by only rotating the transducer. Ultrasound attenuates greatly in the air, and the attenuation changes with frequency. Therefore, COMSOL is used to study the reflection of particles with different radii in the air to ultrasound with various frequencies. It is found that the backscattering equivalent voltage is the largest when the product of ultrasonic frequency and particle radius is about 27.78 Hz �� m, and the particle concentration of 30% causes the strongest backscattering. The simulated results are in good agreement with the Faran backscattering model, which can provide references for selecting the appropriate frequency and obtaining the concentration when measuring gas-solid two-phase flow with the ultrasonic backscattering method.

The phenomenon of pipeline erosion dominated by sulfur particles has become a key research target for sulfur-containing gas-gathering pipelines. Gas-solid two-phase flow of sulfur-containing gases is simulated with a coupled CFD-DPM model in this paper. The Realizable k-ε turbulence model was used to determine the changes in the complex flow field and the Euler-Lagrange method was used to describe the specific trajectory of sulfur particles in the complex flow field. The main erosion trace distribution and the effect of secondary flow effects at the elbow were analyzed and the erosion distribution pattern was investigated for different curvature ratios, particle sizes, and pipe diameters. The results show that the formation of erosion along the tip of the V-shaped erosion trace on the outlet sidewall of the elbow may be related to secondary flow effects. The increase of the curvature ratio RD reduces the erosion intensity of the maximum erosion area, but subsequent increase will result in new secondary erosion trace near the outlet of the elbow and reach the maximum when RD = 8. Variations in particle size will have a significant effect on the extent of the erosion distribution, causing the main erosion distribution of the elbow to vary between 48.2° and 84.2°, while variations in pipeline diameter will have a lesser effect. The Stokes number can also be reduced by controlling the variation in particle size and pipe diameter to alter the force profile on the particles and reduce the erosion effect. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering 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.)

Copyright of Journal of Ballistics / Dandao Xuebao is the property of Journal of Ballistics Editorial Department 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.)

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power 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.)

A single–phase flow model was used to analyze the uniformity of the flow field in the desulfurization tower under different baffle combinations, and a multiphase flow model was used to explain the gas and solid two–phase flow characteristics and chemical reaction characteristics in the tower. The stability of the flow behavior of gas and solids in one furnace and two towers was discussed. The results show that the installation of shielding plates at appropriate positions in the tower for sulfur removal is beneficial to enhance the uniform distribution of flow in space, reduce the pulsation interference of bed pressure in the tower, keep the state of gas and solid flow unchanged, and maintain the efficiency of desulfurization at a high level. Reducing the instability of gas–solid two–phase flow is the basis of ensuring the stable switching between single and double towers. [ABSTRACT FROM AUTHOR]

Under the condition of nitrogen drilling and blowout in an oilfield, the high-speed gas carried cuttings to the wellhead equipment, causing erosion and wear damage to different degrees, especially the erosion and wear of the wellhead four-way bypass. To explore the erosion wear law of the wellhead four-way and slow down the wear rate, based on the erosion failure mechanism of gas–solid two-phase flow, this paper uses the CFD simulation software to establish a wellhead four-way fluid domain model and analyzes the erosion and wear causes of the four-way bypass. And studying the erosion and wear law of the wellhead four-way bypass under different gas blowout amount, cuttings mass flow rate, cuttings diameter and cuttings density. Then, the erosion resistance of Ni60, Ni45 and Inconel625 coating materials was analyzed through experimental research, and the erosion resistance coating on the inner wall of the wellhead four-way was optimized. The results show that: (1) With the increase of natural gas emission amount, cuttings content, and cuttings diameter, the bypass erosion rate increases; the cuttings density has no obvious effect on the erosion rate; (2) The coating material with the strongest erosion resistance is Inconel625, followed by Ni45, and Ni60 has the worst erosion resistance. [ABSTRACT FROM AUTHOR]

• Influence of jets on the distribution of particles in downer is studied. • Advantages of the counter-current introduced jets are summarized. • Distributions of solid holdups in the jet mixing zone of downer are fitted. The large-scale cold model experiments are carried out to investigate the influence of high-speed jets on the distribution of particles in downer. The cases of both downward jets (co-current contact) and upward jets (counter-current contact) are studied. Generally, it is found that the solid holdups in the initial mixing zone of feed with particles are higher under the influence of counter-current jets, which could form the local "thickening" region in downer. To make a quantitative comparison, the radial non-uniformity index of solid holdups RNI(ε s) in the jet mixing zone is calculated. Results show that the solid holdups in the counter-current jet mixing zone are more uniformly distributed in radial and the axial jet influence zone is shorter. By changing the jet gas velocity, its effects on the particle distributions are analyzed. Finally, based on experimental data, the distributions of solid holdups in co-current and counter-current jet influence zones of downer are formulated into formulas. [Display omitted] [ABSTRACT FROM AUTHOR]

The image reconstruction of flowing charged particles in gas-solid two-phase (GSTP) flow can be achieved through electrostatic tomography (EST). Accurate image reconstruction is crucial for detecting the movement patterns of the particles. In order to improve the quality of reconstructed images, a unique convolutional autoencoder neural network (CANN) is proposed. This study uses an image set generated by the linear backprojection (LBP) algorithm to train the CANN, which consists of an encoder and a decoder. The encoder utilizes convolutional and max-pooling layers to reduce the dimensionality of the images and extract key features, while the decoder restores and reconstructs the images through up-sampling and convolutional operations to closely approximate the reference image. To prevent overfitting, dropout layers are introduced after each max-pooling layer in the encoder. To verify the anti-noise capability of the network, Gaussian white noise ranging from 10 dB to 20 dB is added to the test set. The proposed CANN has been validated through simulations and experiments, demonstrating its effectiveness in overcoming noticeable artifacts and noise in reconstructed images when identifying GSTP flow patterns. Furthermore, it shows significant enhancements in imaging outcomes compared to conventional image reconstruction techniques and some current deep learning algorithms. • A unique CANN is proposed to improve the quality of reconstructed images in electrostatic tomography. • An image set generated by the LBP algorithm is simulated for the training, validation, and testing of the CANN. • CANN utilizes its encoder and decoder modules to map input images to reference images. [ABSTRACT FROM AUTHOR]

A gas–solid circulating fluidized bed heat exchanger is designed and built to investigate the particle collision behavior and heat transfer performance under different operating parameters, such as air flow rate, heat flux, and particle type. Air, Polyoxymethylene (POM) and three sizes of glass beads (GB) are selected as working media. Time-domain and frequency-domain analyses are conducted for the collision acceleration signals. The results show that adding solid particles can enhance heat transfer and increase pressure drop of system. The heat transfer enhancing factor reaches up to 33.4%, and the maximum pressure drop ratio is no more than 15.7%. The frequency distribution range of pure gas phase collisions is 0–1000 Hz, and the solid phase plays a dominant role in the collision of gas–solid two-phase flow, distributed between 2000 and 25,000 Hz. The signal power increases with the increase in air flow rate. The heat transfer enhancing factor of POM particles decreases with the increase in air flow rate, but those of GB particles first increases and then decreases. The signal power of POM particles is generally greater than those of GB particles. The heat transfer enhancing factor of POM particles is obviously higher than those of GB particles, especially at low air flow rate. The pressure drop ratio fluctuates with the increase in air flow rate, and generally increases with the increase in heat flux. The drop ratio of the POM particles is higher than those of the GB particles. [Display omitted] • Circulating fluidized bed technology is applied to gas-phase heat transfer process. • Particle collision behavior and heat transfer performance are investigated. • Effects of air flow rate, heat flux and particle type are discussed. • Signal power generally increases with the increase in air flow rate and particle size. • Adding solid particles can enhance heat transfer and increase pressure drop. [ABSTRACT FROM AUTHOR]

In this paper, the Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) coupling method was used to simulate the pneumatic transport of pebble particles in a three-blade spiral tube. The results showed that the flow field distribution rotated along the circumference after loading. The maximum velocity of the flow field after loading was manifested as rotation along the circumference. In addition, the swirl intensity decreased exponentially with the increase in conveying distance, and the maximum swirl intensity had a saturation value. After reaching the saturation value, it is not evident that increasing the initial air velocity significantly affected swirl variation. The smaller the pitch, the greater the initial swirl intensity. The swirling flow was conducive to the fluidization of particles, but it would bring a significant energy loss. Increasing the swirl can increase the degree of particle dispersion. There is an optimal tangential airflow velocity, which allows the particles to fully spin and stay in the suspension zone without being thrown onto the pipe wall by excessive centrifugal force. At this time, the energy efficiency reaches the highest level. A 5.87 m/s velocity was deemed the optimal tangential airflow velocity for conveying 3 mm particles.