基于单次料层冲击破碎质量模型的球磨选择函数

为提高球磨破碎效率,以及构建球磨装置的颗粒破碎过程模型,开展了基于单次料层冲击破碎质量模型的球磨选择函数研究。根据料层夹持形态与落球冲击试验,将料层破碎分为低冲击能下的未完全破碎和高冲击能量下的完全破碎两种状态。分析了单位质量能耗特性和细颗粒对夹持破碎质量的影响,分别建立了两种破碎状态下的料层冲击破碎质量模型。结合冲击能量谱,构建了基于单次料层冲击破碎质量模型的球磨选择函数,将介质球径、颗粒特性等影响球磨破碎效率的参数纳入到选择函数中。     

介质球间非限制料层夹持形态研究

颗粒的球磨粉碎以介质球间非限制料层破碎为主,料层的夹持特性与颗粒破碎密切相关。通过石英颗粒料层挤压实验和离散元仿真发现,介质球径和颗粒粒度对夹持料层厚度存在显著的影响：介质球径小则料层薄、颗粒粒度小则料层厚。通过对实验数据的回归分析,构建了石英颗粒的夹持料层高度计算模型;依据料层高度与料层自锁条件给出了料层夹持范围计算公式,计算模型和公式与料层挤压实验结果符合较好。     

磁粉夹持系统夹持力理论分析和实验研究

针对整体结构件加工过程中存在的装夹难的问题,提出了一种利用磁粉颗粒传递夹持力的装夹方案。介绍了磁粉夹持系统夹持的基本原理,分析影响磁粉夹持系统夹持力大小的各种因素,确定了磁粉颗粒的摩擦系数、磁感应强度和磁粉填充区域为主要的影响因素。通过实验测定了不同目数的磁粉颗粒的摩擦系数,并利用实验平台测定了电流大小、磁粉填充高度与夹持力大小的关系,根据实验数据确定了磁粉颗粒的目数,得出了磁粉填充高度、电流大小与垂直和水平夹持力的函数关系。     

基于EDEM的不同颗粒粒径对物料安息角的影响研究

为了研究颗粒物料的稳定特性,以物料的安息角大小作为衡量物料稳定性的重要指标,首先利用专业离散元软件EDEM对物料的安息角进行了仿真模拟实验,采用切片截断分析方法对不同粒径下的物料安息角的大小进行测量,分析物料粒径对安息角的影响。为进一步研究颗粒粒径对安息角的影响,对颗粒物料的安息角进行实验测量,在实验的过程中运用SPC法对实验所得的数据进行分析判断,并分析了仿真与实验的误差。研究结果表明:实验过程是稳定的,由实验所得到的安息角的数据是可用的。无论是仿真还是实验,都说明颗粒堆积安息角会随着颗粒粒径的增大而增大,并趋于一个极限角度,为物料的稳定性研究提供了一定的理论指导和参考。     

连续油管注入头夹持系统碰撞研究

连续油管注入头夹持系统中的夹持块轴承出现过碰撞碎裂的情况，作为减振部件夹持块垫片的刚度很重要。文中基于动力学基本理论，构建了连续油管注入头夹持系统多体动力学模型。在考虑系统刚度的前提下，针对夹持块垫片刚度对夹持块轴承和滑道板碰撞力的影响做了对比分析；同时，在不同的夹持块垫片厚度下对单个夹持块轴承进行了瞬态动力学碰撞分析。研究结果表明：由于链轮多边形效应，夹持块进入滑道板区域时轴承会与滑道板发生碰撞，滑道板端部采用倒圆弧设计能有效减缓夹持块轴承受到的横向冲击；合适的夹持块垫片刚度与厚度能有效起到减缓夹持块轴承与滑道板碰撞冲击的作用。     

磁粉夹持正压力理论分析和实验研究

采用磁粉柔性夹持某些整体结构件、异构件和薄壁件时,磁粉夹持正压力的大小影响着磁粉夹持效果.介绍了磁粉产生夹持力的基本原理,通过将磁粉颗粒简化为磁偶极子模型来分析处于磁场中的磁粉对工件产生的正压力,得出影响磁粉正压力的各种因素,通过实验验证理论分析结论的正确性.研究结果表明:磁粉的目数、磁导率和磁感应强度越大,磁粉对工件...     

近球壁射流空泡溃灭对微细颗粒破碎效果的影响

为有效解决大规模机械粉体制备中存在的微细颗粒团聚和粉磨极限等问题,采用了空化射流冲击结合磨介研磨的微细颗粒制备方法,并对近球壁空化射流有效冲击破碎颗粒开展了研究。理论分析了近球壁空泡溃灭对微细颗粒的冲击特性,得出了颗粒冲击破碎的有效量纲一距离及临界空泡最大半径;通过空化射流冲击球壁的数值模拟仿真,分析了喷嘴入口压力和靶距对近球壁空泡分布的影响。为验证理论与数值分析结果,开展了基于靶距、转速率、颗粒质量分数和喷嘴数目等多因素的石英砂球磨空化破碎对比实验,实验结果与理论和数值分析结果吻合良好,验证了此方法的有效性。研究结果表明：空化冲击结合磨介研磨微细颗粒的破碎率比单一研磨微细颗粒的破碎率更高;在空化射流入口压力5 MPa下,靶距和转速率是石英砂微细颗粒破碎效果的主要影响因素,其次是喷嘴数目。     

动态环境下重载锻造操作机夹持力建模及影响规律分析

以重载操作机夹持装置为研究对象,建立动态环境下包含销轴摩擦力矩、偏心距、角位移、角速度和锻件半径影响的夹持力模型,并用动力学仿真软件ADAMS进行动态仿真,通过锻造操作机测得的实验数据验证了所建模型的合理性,最后对夹持装置承载能力的影响因素进行了分析。结果表明:夹持装置提供的动态夹持力受其角位移影响小,与角速度和锻件半径成反相关,当钳口处于垂直位置且偏心角小于90°时,与偏心距和偏心角成正相关。这一模型为探讨大尺度时变重载工况下夹持装置承载能力和建立其评价指标提供了参考。     

基于EDEM的物料几何形状对安息角的影响

本文主要是针对载机作业装置的优化设计进行前期基础性研究。通过研究物料的几何形状对安息角大小的影响来探究物料堆积的稳定性,从而保证装载机进行铲装作业时工作装置不受到料堆稳定性的影响,进而更好地优化装载机作业装置。通过利用离散元软件EDEM对物料的安息角进行数值模拟,采用切片截断分析方法对五种不同形状下的物料安息角的大小进行测量,并在对应形状下的安息角进行实验验证,运用SPC法对实验所得的数据进行可靠性判定。研究结果表明:在所研究的五种形状中,安息角的大小按片状、中间状、角状、条状和等径方形的顺序逐渐增大,其机理是因为颗粒内部接触的数量越多,越能真实地反映颗粒之间的相互作用及咬合关系,力链中的颗粒越容易自锁,颗粒之间越不容易分离,堆积特性就越稳定。     

伸缩式对称夹具的设计

伸缩式对称夹具可以夹持不同类型不同厚度的工件,工件的厚度变化不会影响工件固定后的中心线。并且该夹具的夹持头可以缩回夹具架,该夹具还具有安装空间小,夹持力大等优点。     

Control and evaluation of particle impact conditions in a sand erosion test facility

For the prediction of actual damage to plant component materials and for making the erosion mechanisms clear, it is important to control and to evaluate the particle impact conditions in a testing facility. A sand blast type erosion test rig, which can achieve the particle impact velocities up to 135 m s⁻¹ and a wide range of impact angles has been constructed. The key factors in particle impact conditions of particle flux, impact velocity and impact angle were examined. The relative distance between particles and particle size was discussed, as the particle flux affected erosion rate of material. A new method was proposed to determine particle velocities in this facility. The theoretical velocity of the particle calculated by the equations of particle motion was compared with the experimental results. The divergence of particles from a geometrical angle was evaluated by measuring surface roughness of the specimens. Although some spread of the particles were observed surrounding the central damage area of the specimen surface, the greatest amount of damage was concentrated in the center. As a result, it was found that particle impact conditions were well controlled in this testing unit.     

The anti-slurry erosion properties of polyethylene for sewerage pipe use

Sewerage systems are more common in Japan. The pipes and fittings in the systems are exposed not only to a corrosive environment, but also to the impact by solid particles contained in mud drains, resulting in an erosive wear on the surface. A strategy for coping with these problems involves replacing the more traditionally used iron and steel pipes with polymeric materials, which have excellent anti-corrosion properties. In this study, a slurry erosion test were carried out using a jet-in-slit apparatus on seven types of polyethylenes, three other types of polymers, and two types of iron and steels, thoroughly taking into account the fact that erosion damage is highly dependent on the impact angle of the particles. As a result, all the polyethylenes proved to have excellent anti-erosion properties, compared with the other materials over the entire range of particle impact angle. Further, a model was proposed to account the impact angle dependency of the erosion damage. The model aided in clarifying the reasons why the erosion rate of the polyethylenes is satisfactorily correlated with a complex parameter in which the fracture energy and the elastic modulus are combined.     

基于有限元法催化剂颗粒撞击壁面的数值模拟

为解决催化裂化装置中的许多构件因为催化剂颗粒长期不断冲击而导致失效等的问题,将有限元法应用到其模拟仿真中,分析了单颗催化剂颗粒参数(角度、速度、材料)对不同壁面材料的撞击而造成壁面磨损的影响,建立了催化剂颗粒撞击壁面的数值分析模型,研究了催化剂颗粒以不同的速度、撞击角度,以及不同的催化剂颗粒的材料撞击不同材料的壁面对壁面造成的影响,并分析了催化剂颗粒变形对壁面磨损的影响,根据计算的结果,对催化剂颗粒参数进行了优化控制,提出了减少催化剂颗粒变形和构件磨损的技术措施.研究结果表明,该方法能够使催化裂化装置长期安全稳定地运行.     

Measurement technique for the on-line detection of fines in a fluidized bed

In many industrial applications knowledge of the particle size distribution in a fluidized bed and in particular knowledge of the proportion of fines, is extremely important in order to maintain good fluidization quality in the bed, and to prevent too many particles from leaving the cyclones in the gas stream. A common method of monitoring particle size in a laboratory situation is to take a sample of particles from the fluidized bed and use equipment such as a laser diffraction device to analyze the sample, which can be a cumbersome procedure. The objective of this study was to develop an online tool to monitor the proportion of fines in a fluidized bed. A novel online measurement technique for the detection of fines in fluidized beds was developed, which includes a correlation that relates the triboelectric signal to the proportion of fines in the bed.     

Hydrodynamics and particle mixing/segregation measurements in an industrial gas phase olefin polymerization reactor using image processing technique and CFD-PBM model

Particle size distribution (PSD) has a significant impact on the performance of fluidized bed reactors due to uneven distribution in the segregation and mixing phenomena. This paper develops a new method of digital image processing that investigates the hydrodynamics of an industrial gas phase olefin polymerization reactor and studies the fluidization structure of a wide range of particle size distribution in an industrial gas phase polymerization reactor by means of a CFD-PBM coupled model, where the direct quadrature method of moments (DQMOM) was implemented to solve the population balance model. It was shown that the applied parameter assumptions and closure laws were appropriately chosen to satisfactorily predict the available operational data in terms of pressure drop and bed height. The transient CFD-PBM/DQMOM coupled model and image analysis technique are then implemented extensively to analyze bubble fluidization structure and segregation phenomena at different velocities. The particle segregation indicates that the small bubbles present in the bed are unable to induce vigorous mixing at low superficial gas velocity while particle mixing improves at a velocity above the minimum fluidization velocity. Further, the predicted results show higher axial segregation phenomena when compared to the radial direction.     

Nonlinear impact model of a tennis racket and a ball

A nonlinear impact model of a ball impacting on a tennis racket was developed to investigate the impact characteristics of this collision. The impact model included a tennis ball, the tennis racket frame and string bed in a tennis racket. The governing equations for the impact model were derived and were solved by applying numerical analysis. Extensive parametric studies were conducted to study the effects of the system parameters including ball dynamic stiffness, ball damping ratio, racket head size, string tension, string axial rigidity, etc. The analysis results showed that although head size and string axial rigidity have negligible effects on the dwell time and velocity ratio of the ball, string tension can have a significant effect on the dwell time and velocity ratio of the ball.     

Design of a slurry erosion test rig

The design of a jet impingement slurry erosion test rig, built for laboratory use, is presented. This apparatus gives good control over many of the important test parameters, such as impact velocity, solid particle concentration and impact angle. An ejector nozzle is employed to entrain sand particles from a sand bed into a stream of water to form a slurry; after impingement, the abrasive particles and the water phase are separated and recycled. This makes the rig simple, economical and easy to operate and its pump and pipeline remain free from erosive wear. Experimental results are presented to illustrate the operation and performance of the rig.     

砂粒粒径对航空涡轴发动机压气机叶片冲蚀磨损的影响研究

高原、沙漠和沿海等服役环境中不同粒径的砂粒不可避免地对涡轴发动机压气机叶片造成冲蚀磨损,破坏叶片叶型和动力学特性,严重危及涡轴发动机使用寿命和直升机飞行安全。基于Finnie冲蚀磨损理论推导了颗粒对金属表面的磨损率表达式,分析颗粒粒径对材料冲蚀磨损率的影响,以某型涡轴发动机压气机动叶和静叶为研究对象,设计搭建砂粒冲击速度测试装置和钛合金冲蚀磨损实验装置,通过典型砂粒粒径下冲蚀磨损实验获取磨损率表达式中与靶材材料和冲击速度相关的关键参数,结合气固两相流动力学分析开展砂粒粒径对压气机动叶和静叶冲蚀磨损的影响研究。结果表明：砂粒粒径与冲击速度存在内在关联,材料冲蚀磨损率与砂粒冲击速度呈幂函数关系。实验条件下,砂粒粒径由177 μm增至423 μm时,其冲击速度平均降低约17%。压气机动叶和静叶的磨损集中区域不随砂粒粒径的改变而变化,但磨损程度差异明显,其中177 μm砂粒对动叶和静叶造成的最大冲蚀磨损率浓度值相比423μm砂粒分别增加91%和131%。研究结果为涡轴发动机压气机叶片抗磨损设计提供了理论参考。