A comparative study on design standards of screw conveyors in China,Germany,and the USA-Part Ⅱ:Discrete element method

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.

Investigation of the effects of radial clearance on the screw conveyor performances for different inclinations

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.

Developing a screw conveyor in radio frequency systems to improve heating uniformity in granular products

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.

固态发酵法生产白酒的连续蒸馏设备的设计

为提高白酒蒸馏设备的生产效率,设计固态发酵法生产白酒的连续蒸馏设备。在介绍固态发酵法生产白酒的连续蒸馏设备结构设计的基础上,进行输送系统、螺旋出料器的设计计算,得到输送链的链号、头轮和尾轮的齿数、输送系统的驱动功率及其传动比、螺旋出料器的驱动功率及其传动比、螺旋的螺距等设计计算方法,并结出算例,为固态发酵法生产白酒的连续蒸馏设备的开发及其应用提供了基本结构和设计计算方法。

4FY—0.8B型移动式生物质固化成型车螺旋输送系统的改进设计与仿真分析

移动式生物质固化成型车作为一种生物质固化燃料的小型制备机械,对我国秸秆的资源化利用具有积极的推动作用。以新疆农业机械化研究所研制的4FY—0.8B移动式生物质固化成型车螺旋输送系统为研究对象,采用理论分析、改进设计与软件仿真分析相结合的方法,为螺旋输送机性能改进提供依据。通过理论计算设计得出螺旋输送机的基本参数为:螺旋直径为D=125mm,螺距为S=125mm,螺旋输送机转速n=125r/min,驱动功率为P=0.55kW。仿真结果表明:螺旋输送机及其叶片在一阶固有频率下,叶片变形较大,刚性较弱;而在其他较高阶频率下,螺旋轴及叶片的最大变形更加局部化且变形区域增加,最多时可达三处,表明螺旋轴及叶片在高阶固有频率时,结构的形变增加且由叶片向轴处扩展,且增加为多处,因而,在实际设计工作中可以通过零件材质等措施减小共振引发的变形与损坏。

盾构螺旋输送机液压系统设计

简要介绍了盾构掘进机螺旋输送机的工作原理、结构和功能;以此为基础,依据某地铁施工现场对盾构掘进机提出的技术性能要求,对其螺旋输送机液压系统进行了设计;设计方案经过实际应用验证,具有优良的实用性能,能够很好地满足这一类工程用户的要求。

粉料均匀布料系统结构改进

锌空燃料电池极片干嵌法成形设备运行中粉料布料不均,严重影响电池极片的质量。通过分析影响粉料均匀布料的各结构,设计定量变螺距送料机构,解决送料不均匀的问题。研究落料与打料辊之间的相互作用,选择合适的打料辊转速并改进出料口的结构,提高布料的均匀性。

卧螺离心机螺旋输送器转子系统的动力学分析

为了通过螺旋输送器转子系统的动力学特性来研究其工作性能,本文利用有限元软件ANSYS,建立了螺旋输送器转子系统的有限元模型,并进行了模态分析和谐响应分析,计算出转子系统的固有频率和振型,从绘制的Campbell图得出临界转速。研究了转子系统在不平衡激励之后可能产生的共振问题,同时绘制了共振位移与频率的关系图。结果表明,基于ANSYS软件的有限元分析方法方便、实用,对临界转速的分析可以作为避免共振的理论依据,第1阶临界转速时不同位置的共振情况分析为实现卧螺离心机的状态监测和故障诊断提供了参考。

基于PLC的曲料输送系统设计及动力学仿真

针对汾酒集团曲料输送系统自动化程度低、堵料等问题,在不改变原有主体结构的基础上,采用PLC和变频调速技术,通过传感器实现闭环的自动化控制。利用ADAM S对螺旋输送机进行仿真分析,得到了输送机转速与推力间的关系曲线。仿真结果表明新方案可有效防止曲料拥堵和输送不均匀等情况的出现。螺旋输送机的使用性能及可靠性均达到设计要求,实际运行良好,经济效益显著。

磨煤干燥装置气力输送系统与螺旋输送机的对比

磨煤干燥装置中,最终制备出来的合格煤粉产品输送到气化装置。目前国内普遍采用的方式为螺旋输送机或者气力输送系统,本文针对两种煤粉输送方式进行了对比。

DEM investigation on conveying of non-spherical particles in a screw conveyor

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.

Application of a screw conveyor with axial tilt blades on a shearer drum and investigation of conveying performance based on DEM

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.

基于永磁阻尼器的电动螺旋推动器

从带式输送机不同型式的制动装置的对比和应用局限性出发,分析了常见的电液推杆制动器和液压盘式制动器的优缺点。基于电液推杆制动器原有结构,利用永磁阻尼器和螺杆结构的配合,设计并研发了一种纯电驱动的电动螺旋推杆制动器。新型电动螺杆推动器无液压环节,可安装于高、低速轴端,具有结构简单、制动力矩大、可靠性高等特点。通过现场测试,其制动动作可在0.2 s内完成,明显优于普通电液推杆制动器,因其推动器外形结构与电液推杆类似,故可在现有电液推杆制动器使用场合直接替换使用,可有效提高带式输送机制动系统设备的可替换性,降低运营成本。

A comparative study on design standards of screw conveyors in China,Germany and the USA-PartⅠ:Theoretical calculation and quantitative analysis

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.

浅谈对土压平衡盾构机螺旋输送机系统的改造

螺旋输送机系统在土压平衡盾构机施工中扮演着重要角色,其性能好坏直接影响着盾构机的安全可靠及整机掘进作业效率。本文就盾构机螺旋输送机在施工中常见的几种安全隐患、使用不便等情况进行分析,研究相应的改造方案与措施,对螺旋输送机进行进行了优化改造,供业内同行参考。

The fluidesolid coupling analysis of screw conveyor in drilling fluid centrifuge based on ANSYS

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.

浅埋富水地层特大断面矩形顶管隧道掘进参数分析

为保障特大断面矩形顶管隧道在浅覆土、小净距下的安全高效掘进,依托世界上首个直径15 m级3车道矩形顶管隧道工程,对顶管多刀盘开挖系统、减摩注浆系统、三螺机出渣系统进行针对性优化设计。通过对顶管主要掘进参数及地层沉降监测结果进行统计分析,得到以下结论:1)本工程采用的减阻措施有效降低了管节受到的地层摩擦阻力,实际总推力为理论值的40%左右;2)刀盘直径和安装高度对刀盘转矩影响较大,多数刀盘转矩均值小于额定转矩的一半,说明刀盘额定转矩有较大的优化空间;3)顶管掘进过程中盾壳受到较大的地层挤压力,土舱内渣土压力也显著大于地层侧向土压力,停机后上述压力均有较大幅度降低;4)顶管掘进后地表横向沉降槽呈“盆”状,隧道两侧0.5倍开挖宽度内的地层沉降较大。

Numerical investigation on the spewing mechanism of earth pressure balance shield in a high-pressure water-rich sand stratum

The spewing of a screw conveyor easily occurs from the earth pressure balance(called EPB)shield in a water-rich sand stratum.This may lead to the collapse of the tunnel face and even serious subsidence of the ground surface.To understand the spewing mechanism of the shield screw conveyor and explore the critical hydraulic condition of soil spewing in a shield–soil chamber,a simplified theoretical model for the spewing of the screw conveyor was developed based on the equation of groundwater flow in the screw conveyor under turbulent state.Thus,coupling Darcy's law with Brinkman's equation,this model was implemented within the COMSOL Multiphysics framework.The underground water flow in the shield screw conveyor was simulated so as to obtain its velocity and flow rate.Numerical simulations show that the water pressure distribution is concentrated in the lower part of the soil chamber after the groundwater enters the soil chamber.When the groundwater enters the screw conveyor,its pressure gradually decreases along the direction of the screw conveyor.When the water flow reaches the stratum–shield interface,the flow velocity changes markedly:first increases and concentrates at the entrance of the lower soil chamber,plummets and stabilizes gradually,and increases again at the exit.The soil chamber and screw conveyor are significantly depressurized.It is also found that the soil permeability coefficient can be reduced to k<2.6×10^(−4)cm/s through appropriate soil improvement,which can effectively prevent the occurrence of spewing disasters.

砂卵石层矩形顶管机切削技术及排渣系统研究与应用

为探索矩形顶管机在砂卵石层中的适应性,以成都市下穿人民南路人行通道矩形顶管项目为依托,对矩形顶管机在砂卵石地层中的组合式刀盘布置、下部刀盘减阻技术、螺旋机叶片安装位置和闸门结构形式等切削及排渣关键技术进行研究。结果表明:1)采用同平面刀盘开挖形式,可减少前后刀盘布置带来的卡卵石现象,避免卵石对刀盘的的冲击,更能适应砂卵石地层的施工;2)全部或部分切除下部刀盘加强大圆环,进行结构优化,在满足砂卵石地层开挖需求的同时,降低切削转矩20%左右;3)带式双螺旋输送机螺旋叶片伸入土舱设计使螺旋输送机携渣能力提高3倍,且弧形闸门装置能够对渣土实现有效封堵。

筒式烘干机搅龙试验研究

通过对筒式烘干机排粮机构两种不同外径的搅龙 ,在不同转速下 ,进行扭矩和弯矩测试 ,检验了开式输送物料理论 。