This part of the study aims to evaluate the advantages and disadvantages of technical standards of screw conveyors in China,Germany,and the USA for industrial applications.The source or determination method of empiric...This part of the study aims to evaluate the advantages and disadvantages of technical standards of screw conveyors in China,Germany,and the USA for industrial applications.The source or determination method of empirical coefficients as well as the theoretical foundation of dimensioning-relevant diagrams in these standards is not explicitly documented in the literature.Therefore,instead of less efficient on-site tests,the numerical simulation by discrete element method is conducted.Based on the geometrical and operational designs determined in three standards for horizontal,slightly inclined,and vertical conveyance of three representative bulk solids(barley,lignite,and sand),the potential influencing factors are discussed.With constant particle and contact parameters,the potential deviations caused by particle models are eliminated.Furthermore,the accuracy of power consumption calculation of each standard and the divergence between accessible and required mass flows is comprehensively assessed based on the analysis of simulated outcomes.Two main conclusions are drawn:(1)Particle fall back is barely considered by all three standards and leads to overestimated mass throughput;(2)The decrease in mass throughput caused by an increasing degree of filling can be compensated by slowing down the rotational speed.展开更多
Screw conveyors are widely used for bulk material transportation.This study investigates the critical role of radial clearance,the gap between the screw and the conveyor body,on performance across various inclination ...Screw conveyors are widely used for bulk material transportation.This study investigates the critical role of radial clearance,the gap between the screw and the conveyor body,on performance across various inclination angles.The Discrete Element Method(DEM)is employed to analyze the effects of different radial clearances on conveyor performance for concrete aggregate and sand as bulk materials.Volumetric efficiencies and capacity losses serve as key performance indicators,quantitatively assessed for each radial clearance and inclination combination.Experimental validation is conducted to corroborate the findings.In the study,the optimal radial clearance was identified as 1.5 to 3 times of the particle size.This optimal clearance minimizes the material jamming and increases the performance for screw conveyors with different inclinations and bulk material types as a result.展开更多
Screw conveyors are extensively used in modern industry such as metallurgy,architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials.And substantial efforts have been dev...Screw conveyors are extensively used in modern industry such as metallurgy,architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials.And substantial efforts have been devoted to the study of the screw conveyors.Numerical method is an effective way to study screw conveyor.However,previous studies have mainly focused in the regime of spherical particles while the in-depth investigations for non-spherical particles that should be the most encountered in practical applications are still limited.In view of the above situations,discrete element method(DEM),which has been widely accepted in simulating the discrete systems,is utilized to investigate the conveying process of non-spherical particles in a horizontal screw conveyor,with particles being modeled by super-ellipsoids.In addition,a wear model called SIEM(Shear Impact Energy Model)is incorporated into DEM to predict the wear of screw conveyor.The DEM simulation results demonstrate that the particle shape is influential for the flow behaviors of particles and the wear of conveyor.The conveying performance evaluated quantitatively of both mass flow rate and power consumption is subsequently obtained to investigate the effect of sphericity of particle with different operation parameters.Moreover,particle collision frequency and collision energy consumption are acquired to investigate the possible particle breakage between particles and screw blade.The comparisons between particle-particle collision and particle-wall collision reveal that particles with large shape index have more possibility to be damaged in particle-wall impingement.展开更多
Screw conveyors are widely employed in industrial fields for conveying bulk materials.The shearer drum which uses the screw conveying principle is responsible for excavation and conveying coal particles onto the chain...Screw conveyors are widely employed in industrial fields for conveying bulk materials.The shearer drum which uses the screw conveying principle is responsible for excavation and conveying coal particles onto the chain conveyor.Screw conveyor performance is affected by potential factors,such as the blade axial tilt angle and style,core shaft form and diameter.The effect of blade axial tilt angle on the conveying performance was investigated with the help of DEM.In the case of the screw conveyor,the mass flow rate,and particle axial velocity increased with increasing positive axial tilt angle,and declined with increasing negative axial tilt angle.In the case of the drum,the mass flow rate,particle axial velocity,and loading rate first increased and then decreased with increasing positive axial tilt angle,and decreased with increasing negative axial tilt angle.These results can be considered as a benchmark for screw conveyor and drum structural designs with axial tilt screw blades.展开更多
Radio frequency(RF)treatments have been increasingly studied due to the rapid heating,deep power penetration depth and high energy efficiency.However,the major challenges for commercial RF applications are non-uniform...Radio frequency(RF)treatments have been increasingly studied due to the rapid heating,deep power penetration depth and high energy efficiency.However,the major challenges for commercial RF applications are non-uniform and run-away heating.The purpose of this study was to improve RF heating uniformity in three granular products(soybean,corn,and peanut)using a custom-made screw conveyor with sample movement and mixing.The results showed that soybean,corn and peanut samples in the screw conveyor were RF heated in a similar heating rate under the selected electrode gap and screw rotation speed,and the variations between the highest and lowest temperatures in the three samples were all clearly reduced as compared to the stationary treatments.The RF heating uniformity index was also reduced for soybean,corn,and peanut during and after the RF treatment.Therefore,the screw conveyor could improve RF heating uniformity due to stable,continuous,uninterrupted movement and mixing of samples.The small-scale screw conveyor used in RF systems would provide a solid basis for further large-scale industrial applications.展开更多
Screw conveyors,widely used devices for transporting bulk materials,play an irreplaceable role in the modern industrial system.Despite of their traditional advantages,designers of screw conveyors still heavily rely on...Screw conveyors,widely used devices for transporting bulk materials,play an irreplaceable role in the modern industrial system.Despite of their traditional advantages,designers of screw conveyors still heavily rely on their own country's experiments and standards,which are closely related to empirical data.Therefore,the same conveying task often results in different designs.This work aims to compare the design standards of screw conveyors in China,Germany and the USA.Based on related standards acquired from renowned associations in the three countries,the similarities and particularities of these design guidances are compared.With preforming the geometrical and operational designs for horizon-tal,slightly inclined and vertical conveyance of three representative bulk solids(barley,lignite,sand),the advantages and disadvantages of these semi-empirical designs are comprehensively presented.Fur-thermore,the potential influence of empirical coefficients,which are not explicitly documented,are extensively discussed.By analysing all outcomes,the compatibility and applicability of each standard are qualitatively assessed.展开更多
In the centrifugal separations of drilling fluid,screw conveyor is a critical component to push and separate the sediment.The work performance and structural parameters of conveyor are immediately related to the produ...In the centrifugal separations of drilling fluid,screw conveyor is a critical component to push and separate the sediment.The work performance and structural parameters of conveyor are immediately related to the production capability,the working life and the separating effect of the centrifuge.The existing researches always use the theoretical calculation of the approximate loads to analyze the strength of conveyor,and it cannot reflect the stress situations accurately.In order to ensure the precise mastery of the working performance,this article obtained pressure distribution under working conditions from CFX evaluation and gained equivalent stress and deformation under several load conditions by using the ANSYS Workbench platform to check the strength of conveyor.The results showed that the influence of centrifugal hydraulic pressure was less than that of centrifugal force on the strength and deformation of conveyor.Besides,the maximum equivalent stress occurred at the inside of the feed opening,while the maximum deformation occurred at the conveyor blade edge of taper extremity.Furthermore,whether considered the feed opening or not,the computing model had a great influence on the analysis results,and the simplified loads had a great influence on the deformation analysis results.The methods and results from this article can provide reference for the design and the improvement of screw conveyor.展开更多
【目的】为提高螺旋输送机的输送效率,降低输送机的功耗与磨损,探究在不同进料速率、螺旋轴转速与几何体摩擦系数下,超细碳酸钙在水平变径变距螺旋输送机内的颗粒流动状态、出口质量流量、输送机功耗与磨损分布。【方法】使用计算流体...【目的】为提高螺旋输送机的输送效率,降低输送机的功耗与磨损,探究在不同进料速率、螺旋轴转速与几何体摩擦系数下,超细碳酸钙在水平变径变距螺旋输送机内的颗粒流动状态、出口质量流量、输送机功耗与磨损分布。【方法】使用计算流体动力学(computational fluid dynamics,CFD)与离散单元法(discrete element method,DEM)双向耦合数值模拟的方法,对螺旋输送机在不同转速下的质量流率进行分析对比,验证数值模型的正确性。【结果】摩擦系数对颗粒的运动有较大影响,颗粒流的轴向速度峰值和质量流率峰值随着摩擦系数的增加先增大再减小;随着下料速度和摩擦系数的增大,输送机功率明显增大,且摩擦系数在高进料速度与低转速的情况下对功耗的影响相对于低进料速度和高转速更加明显;磨损较严重的区域集中在下料口处的螺旋轴与螺旋叶片的边缘处。【结论】简单增大或减小摩擦系数并不能提高颗粒的轴向速度和质量流量,而是存在一个局部最优参数组合;适当地提高转速能够减小颗粒密实度与颗粒停留时间,从而减小输送机的功耗与几何体磨损。展开更多
基金the European Union's Horizon 2020 Program(H2020/2014–2020)under grant agreement No.654446.
文摘This part of the study aims to evaluate the advantages and disadvantages of technical standards of screw conveyors in China,Germany,and the USA for industrial applications.The source or determination method of empirical coefficients as well as the theoretical foundation of dimensioning-relevant diagrams in these standards is not explicitly documented in the literature.Therefore,instead of less efficient on-site tests,the numerical simulation by discrete element method is conducted.Based on the geometrical and operational designs determined in three standards for horizontal,slightly inclined,and vertical conveyance of three representative bulk solids(barley,lignite,and sand),the potential influencing factors are discussed.With constant particle and contact parameters,the potential deviations caused by particle models are eliminated.Furthermore,the accuracy of power consumption calculation of each standard and the divergence between accessible and required mass flows is comprehensively assessed based on the analysis of simulated outcomes.Two main conclusions are drawn:(1)Particle fall back is barely considered by all three standards and leads to overestimated mass throughput;(2)The decrease in mass throughput caused by an increasing degree of filling can be compensated by slowing down the rotational speed.
文摘Screw conveyors are widely used for bulk material transportation.This study investigates the critical role of radial clearance,the gap between the screw and the conveyor body,on performance across various inclination angles.The Discrete Element Method(DEM)is employed to analyze the effects of different radial clearances on conveyor performance for concrete aggregate and sand as bulk materials.Volumetric efficiencies and capacity losses serve as key performance indicators,quantitatively assessed for each radial clearance and inclination combination.Experimental validation is conducted to corroborate the findings.In the study,the optimal radial clearance was identified as 1.5 to 3 times of the particle size.This optimal clearance minimizes the material jamming and increases the performance for screw conveyors with different inclinations and bulk material types as a result.
基金This research was financially supported by the National Key Research and Development Program of China(grant No.2019YFC1805605)the National Natural Science Foundation of China(grant No.22078283)。
文摘Screw conveyors are extensively used in modern industry such as metallurgy,architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials.And substantial efforts have been devoted to the study of the screw conveyors.Numerical method is an effective way to study screw conveyor.However,previous studies have mainly focused in the regime of spherical particles while the in-depth investigations for non-spherical particles that should be the most encountered in practical applications are still limited.In view of the above situations,discrete element method(DEM),which has been widely accepted in simulating the discrete systems,is utilized to investigate the conveying process of non-spherical particles in a horizontal screw conveyor,with particles being modeled by super-ellipsoids.In addition,a wear model called SIEM(Shear Impact Energy Model)is incorporated into DEM to predict the wear of screw conveyor.The DEM simulation results demonstrate that the particle shape is influential for the flow behaviors of particles and the wear of conveyor.The conveying performance evaluated quantitatively of both mass flow rate and power consumption is subsequently obtained to investigate the effect of sphericity of particle with different operation parameters.Moreover,particle collision frequency and collision energy consumption are acquired to investigate the possible particle breakage between particles and screw blade.The comparisons between particle-particle collision and particle-wall collision reveal that particles with large shape index have more possibility to be damaged in particle-wall impingement.
基金funded by the National Natural Science Foundation of China(Grant No.51704178)the Natural Science Foundation of Shandong Province(Grant No.ZR2017MEE034)+2 种基金the Open Foundation of Shandong Province Key Laboratory of Mine Mechanical Engineering(Grant No.2019KLMM102)the Project of Shandong Province Higher Educational Young Innovative Talent Introduction and Cultivation Team(Performance enhancement of deep coal mining equipment)the project of the Postdoctoral Science Foundation of China(Grant No.2019M662403).
文摘Screw conveyors are widely employed in industrial fields for conveying bulk materials.The shearer drum which uses the screw conveying principle is responsible for excavation and conveying coal particles onto the chain conveyor.Screw conveyor performance is affected by potential factors,such as the blade axial tilt angle and style,core shaft form and diameter.The effect of blade axial tilt angle on the conveying performance was investigated with the help of DEM.In the case of the screw conveyor,the mass flow rate,and particle axial velocity increased with increasing positive axial tilt angle,and declined with increasing negative axial tilt angle.In the case of the drum,the mass flow rate,particle axial velocity,and loading rate first increased and then decreased with increasing positive axial tilt angle,and decreased with increasing negative axial tilt angle.These results can be considered as a benchmark for screw conveyor and drum structural designs with axial tilt screw blades.
基金This research was conducted in the College of Mechanical and Electronic Engineering,Northwest A&F University,and supported by research grants from National Key R&D Program of China(2016YFD0401000).
文摘Radio frequency(RF)treatments have been increasingly studied due to the rapid heating,deep power penetration depth and high energy efficiency.However,the major challenges for commercial RF applications are non-uniform and run-away heating.The purpose of this study was to improve RF heating uniformity in three granular products(soybean,corn,and peanut)using a custom-made screw conveyor with sample movement and mixing.The results showed that soybean,corn and peanut samples in the screw conveyor were RF heated in a similar heating rate under the selected electrode gap and screw rotation speed,and the variations between the highest and lowest temperatures in the three samples were all clearly reduced as compared to the stationary treatments.The RF heating uniformity index was also reduced for soybean,corn,and peanut during and after the RF treatment.Therefore,the screw conveyor could improve RF heating uniformity due to stable,continuous,uninterrupted movement and mixing of samples.The small-scale screw conveyor used in RF systems would provide a solid basis for further large-scale industrial applications.
基金This project has received funding from the European Union's Horizon 2020 Program(H2020/2014-2020),under grant agreement no.654446.
文摘Screw conveyors,widely used devices for transporting bulk materials,play an irreplaceable role in the modern industrial system.Despite of their traditional advantages,designers of screw conveyors still heavily rely on their own country's experiments and standards,which are closely related to empirical data.Therefore,the same conveying task often results in different designs.This work aims to compare the design standards of screw conveyors in China,Germany and the USA.Based on related standards acquired from renowned associations in the three countries,the similarities and particularities of these design guidances are compared.With preforming the geometrical and operational designs for horizon-tal,slightly inclined and vertical conveyance of three representative bulk solids(barley,lignite,sand),the advantages and disadvantages of these semi-empirical designs are comprehensively presented.Fur-thermore,the potential influence of empirical coefficients,which are not explicitly documented,are extensively discussed.By analysing all outcomes,the compatibility and applicability of each standard are qualitatively assessed.
基金This research is supported by the Major Cultivation Foundation of Sichuan Education Department(13ZA0179).
文摘In the centrifugal separations of drilling fluid,screw conveyor is a critical component to push and separate the sediment.The work performance and structural parameters of conveyor are immediately related to the production capability,the working life and the separating effect of the centrifuge.The existing researches always use the theoretical calculation of the approximate loads to analyze the strength of conveyor,and it cannot reflect the stress situations accurately.In order to ensure the precise mastery of the working performance,this article obtained pressure distribution under working conditions from CFX evaluation and gained equivalent stress and deformation under several load conditions by using the ANSYS Workbench platform to check the strength of conveyor.The results showed that the influence of centrifugal hydraulic pressure was less than that of centrifugal force on the strength and deformation of conveyor.Besides,the maximum equivalent stress occurred at the inside of the feed opening,while the maximum deformation occurred at the conveyor blade edge of taper extremity.Furthermore,whether considered the feed opening or not,the computing model had a great influence on the analysis results,and the simplified loads had a great influence on the deformation analysis results.The methods and results from this article can provide reference for the design and the improvement of screw conveyor.
文摘【目的】为提高螺旋输送机的输送效率,降低输送机的功耗与磨损,探究在不同进料速率、螺旋轴转速与几何体摩擦系数下,超细碳酸钙在水平变径变距螺旋输送机内的颗粒流动状态、出口质量流量、输送机功耗与磨损分布。【方法】使用计算流体动力学(computational fluid dynamics,CFD)与离散单元法(discrete element method,DEM)双向耦合数值模拟的方法,对螺旋输送机在不同转速下的质量流率进行分析对比,验证数值模型的正确性。【结果】摩擦系数对颗粒的运动有较大影响,颗粒流的轴向速度峰值和质量流率峰值随着摩擦系数的增加先增大再减小;随着下料速度和摩擦系数的增大,输送机功率明显增大,且摩擦系数在高进料速度与低转速的情况下对功耗的影响相对于低进料速度和高转速更加明显;磨损较严重的区域集中在下料口处的螺旋轴与螺旋叶片的边缘处。【结论】简单增大或减小摩擦系数并不能提高颗粒的轴向速度和质量流量,而是存在一个局部最优参数组合;适当地提高转速能够减小颗粒密实度与颗粒停留时间,从而减小输送机的功耗与几何体磨损。
