振動篩畢業(yè)論文外文文獻翻譯

1、Dynamics and screening characteristics ofa vibrating screen with variable elliptical traceHE Xiao-mei,LIU Chu-shengSchool of Mechanical and Electrical Engineering,China University of Mining & Technology,Xuzhou,Jiangsu 221116,ChinaAbstract: the ideal motion characteristics for the vibrating scree

2、n was presented ,vibrating screen with variable elliptical trace was proposed. An accurate mechanical model was constructed according to the required structural motion features.Applying multi-degree-of-freedom vibration theory,characteristics of the vibrating screen was analyzed.Kinematics parameter

3、s of the vibrating screen which motion traces were linear,circular or elliptical were obtained.The stable solutions of the dynamic equations gave the motions of the vibrating screen by means of computer simulations.Technological parameters,including amplitude,movement velocity and throwing index,of

4、five specificpoints along the screen surface were gained by theoretical calculation .The results show that the traces of the new designed vibrating screen follow the ideal screening motion .The screening efficiency and processing capacity may thus be effectively improved.Keywords:variable elliptical

5、 trace;screening process with constant bed thickness; dynamic model;motion characteristic;screening characteristics1 Introduction Screening operations are an important part of coal processing. The vibrating screen is one of the most extensively used screening tools. Vibrating screens, such as linear

6、 vibrating screen, circular vibrating screen or elliptical vibrating screen, have a simple translational motion. The motion follows the same path everywhere on the screen and so the screen has constant transport velocity and throwing index, which leads to low screening efficiency. Augmenting the thr

7、owing index to improve breaks the exciting motors processing capacity lowers the working.In this paper , we report on the design of a new vibrating screen with variable motion traces that is based on the principle of screening process with constant bed thickness34.Different parts of the vibrating sc

8、reen traverse different elliptical traces and the resulting motion agrees well with the ideal motion .Thus the screen processing capacity and efficiency can both be improved.2 Ideal motion for a screen surface and the proposal of a vibrating screen with variable elliptical trace2.1 Screening charact

9、eristics of common vibrating screensVibrating screens commonly work at a fixed vibration intensity .Material on the screen surface moves by throwing, rolling or sliding motions .For common screeners ,material granularity is widely distributed at the feed end .The energy imparted to the material part

10、icles from the vibrating screen is severely dissipated .Consequently ,a large number of particles become laminated only a short distance from the feed end .The material penetrates the screen within the first 1/4 to 1/2 of the screen ,which affects screening and lowers processing capacity 5.The decre

11、ase of fine-grained material causes the ratio of particles close in size to ,or larger than ,the mesh to increase .Thus ,the screening efficiency declines dramatically .The material granularity simultaneously becomes uniform and the energy imparted from the vibrations to the material suffers little

12、loss .Hence ,the amplitude and velocity of the material particles increase .This causes the material bed depth at the feed end to be thick while at the discharge end it isThin .This kind of motion leads to an asymmetrical penetration along the screen surface,which influences the screening efficiency

13、 and processing capability 6.Common screening characteristics are shown in Fig.1.2.2 Ideal motion for screen surface and implementing schemeThe ideal motion for screen surface is described below, according to the principle of screening process with constant bed thickness .The feed end of the screen

14、has a bigger throwing index and a higher material delivery velocity ,which makes bulk material quickly penetrate and causes rapid delaminating. Earlier lamination of material increases the probability of fine-grained material passing through the mesh .The screen has an appropriate throwing index and

15、 a little higher material delivery velocity in its middle part .This is of benefit for stabilizing fine-grained materials and for penetrating uniformly along the screen length .A lower throwing index and material delivery velocity near the discharge end causes the material to stay longer on the scre

16、en and encourages more complete penetration of the mesh. Two methods are currently used to improve screening efficiency 78.The first is to add material to the screen from multiple feed ports. This is troublesome in practical use especially in terms of controlling the distribution of differently gran

17、ulated materials .Hence it is rarely used in practical production. The second way is to adopt new screening equipment like, for example, a constant thickness screen. The motion of the new screen surface causes material to maintain the same, or an increased, thickness .It achieves a rather more ideal

18、 motion.The main problem with the constant thickness screen is that it covers a bigger area and that the structure is complicated and hard to maintain .A simple structure with good screening efficiency is still a necessity. We have designed a new vibration screen with a variable elliptical trace tha

19、t is based upon an ideal screen motion for use in raw coal classification. The size of the vibrating screen is 3.6 m×7.5 m,the feed granularity is 0 to 50 mm and the classification granularity is 6mm.Elliptically vibrating screens combine the basic advantages of both circular and linear vibrati

20、ng screens 910.The long axis of the ellipse determines material delivery and the short axis influences material loosening, to be exact.3 Dynamics model analysis of vibrating screen with variable elliptical traceWe made the exciting force deviate from the center of gravity,to change the motion patter

21、n of the new vibrating screen.The stiffness matrix of the vibration isolation spring was not zero under these circumstances and the vibrating system had multiple degrees of freedom.Minor transverse wagging was neglected to simplify the research.The motion was considered to be a linear vibration of a

22、 rigid beam in the longitudinally symmetrical plane.At each point the vibration is a combination of the translation of the center of gravity and the screen pitching about the center of gravity.Previous studies neglected the influence of elastic forces in the horizontal and vertical direction on the

23、swing of the vibrating screen 3,11.An accurate dynamic model consisting of three differential equations that include coupling of degrees of freedom in the vertical,horizontal and swing directions is proposed.The mathematical model of the vibrating screen is shown in Fig.2.The center of gravity, is t

24、aken as the origin of a rectangular coordinate system at staticequilibrium, in accordance with rigid motion on the plane 12.Simultaneous differential equations in generalized coordinates using center of gravity coordinates,(x,y),and the swing declination angle, ,may be written aswhere M is the mass

25、of the vibrating screens the moment of inertia of M relative to the center of gravity,O;x and y the displacements in the x and y0directionas;x and y the velocities in the x and y directions and y the accelerations in the x and y directions; is the swing angular displacement; the installation angle;f

26、x,f yond father damping coefficients in the x,y and directions;x k and k the stiffness coefficients of the supporting spring along the x and y directions; A0 the amplitude of the exciting force, given by2 0 A =mr, where r is the radius of eccentricity the mass of the eccentric block and the exciting

27、 angular frequency; L1 and L2 the distances between each supporting spring and the center of gravitys the distance between the rotating center of the eccentric block and the center of gravity; and,the included angle between the l and x directions. The damping force is rather small and can be neglect

28、ed. Then Eq. (1) can be simplified to Eq.(2).4 Motion and screening effect analysis of a vibrating screen with variable elliptical trace4.1 Analysis of the motion parameters Multiple degree-of-freedom vibration theory was used to find a stable solution for the forced vibration 13,as follows:When E 2

29、 S 2 +C 2 H 2 +2 ESCH=0, the trace of point D is a line. When E =Sand C =H, the trace of point D is a circle. In general. (6) expresses the equation of an ellipse.The xoy coordinate was rotated degrees anticlockwise to give a new set of x oycoordinates. A standard elliptical equation was then obtain

30、ed after eliminating D D x y in Eq.(7).From this we know that some points on the screen move in a line or a circle while others move in an ellipse .As long as the relative position of the rotating center of the eccentric block and the center of gravity are properly adjusted, variable elliptical moti

31、on of the screen will be obtained .This provides a reasonable throwing index and material delivery velocity and improves screening efficiency.4.2 Analysis of motion trace and screening efficiency The stable solution of a vibrating system, in terms of the vibrating screen, can be given byThe equation

32、s of motion for any point on the vibrating screen areEq.(8)shows that the center of gravity traces an approximate circle and that the amplitude in the horizontal and vertical directions is between 3.5 mm and 5 mm.Fig.3 shows how the center of gravity moves in three degrees of freedom.Fig.3 gives the

33、angular phase difference between the horizontal and vertical directions as well as the amplitude of the swing angle.5 Conclusions1)A new vibrating screen with variable elliptical motion trace was proposed according to the principle of screening process with constant bed thickness.Different points on

34、 the vibrating screen trace different elliptical paths.The motion pattern agrees well with the ideal motion characteristic for a screening surface. Thus,screening capacity and process efficiency can be increased.2)A theoretical kinematic analysis of the vibrating screen was done to study how varying

35、 different parameters affects the motion of the screen.Kinematics parameters of the vibrating screen that motion traces are linear,circular or elliptical are obtained.3) Motion traces of total vibrating screen were gained through computer simulations.Screening technological parameters,including ampl

36、itude, velocity and throwing index,of five specific points along the screen surface were calculated. Theseparameters are related to screening efficiency. The results show that the motion pattern of the designed vibrating screen conforms to an ideal screening motion and that the design is able to eff

37、ectively improve screening efficiency.4)The position of the exciter axle center,relative to the center of gravity of the vibrating screen,is extremely important for screening efficient.Thus,we can design a vibrating screen with higher processing capacity without increasing power consumption by adjus

38、ting the relative position of the axle center.This is a point that requires further study.References1Wen B C,Liu F Q.Theory and Application of Vibration Machines.Beijing:China Machine Press,1982.2Gu Q B,Zhang E G.Study on complex-locus vibration screen.Mining&Processing Equipment,1998(1):4246.3H

39、ao F Y.Coal Preparation Manual:Technology and Equipment.Beijing:China Coal Industry Publishing House,1993.4Yan F.Screening Machines.Beijing:China Coal Indus-try Publishing House,1995.5Liu C S,Zhao Y M.Study on nonlinear characteristics of single particle on screening surface.Mining&Processing Eq

40、uipment,1999(1):45486Tao Y J,Luo Z F,Zhao Y M.Experimental research on desulfurization of fine coal using an enhanced centri- fugal gravity separator.Journal of China University ofMining&Technology,2006,16(4):399403.7Zhang E G.Screening,Crushing and Dewatering Equipments. Beijing: China Coal Ind

41、ustry Publishing House,1991.8 Khoury D L.Coal Cleaning Technology .USA:Noyes Data Corporation,1981.9Shang N X,Na J F.2TYA1842 elliptical vibration screen. Mining&Processing Equipment,1990(2):2024. 10YeHD.Elliptical isopachous screening technology andits application.Sintering and Palletizing,1999

42、,5(3):3033.11Wen B C,Liu S Y,He Q.Theory and Dynamic Design Method of Vibration Machines.Beijing:China Machine Press,2001. 12Wang F,Wang H.Screening Machines.Beijing:China Machine Press,2001.13Ni Z H.Vibration Mechanics.Xian:Xian Jiaotong University Press,1989.14Zhu W B.Working principle and compute

43、r simulation of vibrating screen with complicated motion trace.Mining &Processing Equipment,2004(10):3436.15Peder M.The mogensen E-seriesa new screening oncept.Mineral Processing,1996,7(37):311315.16Wen B C.Synchronization theory of self-synchronous vibrating machines with ellipse motion locus.

44、Boston:American Society of Mechanical Engineers,1987:495500.變橢圓軌跡振動篩的動力學(xué)和篩選特性何小梅，劉楚生機械和電氣工程學(xué)院，中國礦業(yè)大學(xué)科技，江蘇省徐州市221116，中國摘要：根據(jù)振動篩的理想運動特性，提出了變橢圓軌跡的振動篩。根據(jù)所需的結(jié)構(gòu)運動特性建立了一個精確的力學(xué)模型。應(yīng)用多自由度振動理論，對振動篩的特性進行了分析。獲得了線性的、圓形或橢圓形的運動軌跡振動篩的運動學(xué)參數(shù)。通過計算機模擬振動篩的運動動態(tài)方程得以有效的求解。通過理論計算求得振動篩上五個具體點的工藝參數(shù),包括振幅、運動速度和拋擲指數(shù)。結(jié)果顯示，新設(shè)計的振動篩的軌

45、跡遵循理想的篩選運動。篩分效率及處理能力可能因此而得到有效改進。關(guān)鍵字：變橢圓軌跡；等厚篩分；動態(tài)模型；運動特性；篩分特性1前言篩分操作是一個重要的煤礦處理組成部分。振動篩是最廣泛使用的篩選工具之一。振動篩，如直線振動篩、圓振動篩或橢圓振動篩，都有一個簡單的平移運動。運動在振動篩上到處都遵循相同的路徑,所以振動篩有恒定的運輸速度和拋擲指數(shù)，從而導(dǎo)致低的篩分效率。增強拋擲指數(shù)來改善激振電機在工作中的較低的處理能力。在本文中，我們就一個基于等厚篩分理論的新的可變的運動軌跡振動篩的設(shè)計做報告34。振動篩的不同部分有著不同的橢圓運動軌跡，由此產(chǎn)生的運動與理想的運動軌跡相吻合。因此振動篩的處理能力和效率

46、都可以得到改善。2振動篩表面的理想運動軌跡和變橢圓軌跡振動篩的建議2.1振動篩常見的篩選特性 振動篩通常工作在一個固定的振動強度。材料在篩面上拋擲、滾動或滑動運動。對于常見的篩網(wǎng)，物料顆粒在入料端廣泛的分布。振動篩給予物料顆粒的能量被大量的浪費。因此，大量的顆粒只在入料端附近很短的一段距離里分層。材料進入振動篩在第一個1/4到1/2的篩體，它影響篩選并降低加工能力5。細(xì)質(zhì)級材料的減少，導(dǎo)致粒子的比例接近或大于網(wǎng)格增加的大小。因此,篩選效率急劇下降。物料粒度同時統(tǒng)一的，從振動源給予物料的能量損失很小。因而物料粒子的振幅和速度增加。這導(dǎo)致了物料的垂直深度在入料端厚，而在出料端薄，進而影響了篩分效率

47、和處理能力。常見的篩分特性如圖1.2.2振動篩表面的理想運動和實施方案振動篩表面的理想運動描述如下，根據(jù)篩選過程的等厚篩分原則。振動篩的入料端有一個較大的拋擲指數(shù)和較高的材料傳遞速度，這使得大部分材料迅速滲透,導(dǎo)致快速分層。材料的快速分層增加細(xì)粒度的材料通過篩網(wǎng)的概率。振動篩有一個適當(dāng)?shù)膾仈S指數(shù)和高一點材料傳遞速度的中間部分。這有利于穩(wěn)定處理細(xì)粒度材料并沿著振動篩的長度方向穿過。靠近出料端較低的拋擲指數(shù)和材料遞送速度導(dǎo)致材料在振動篩上停留更長的時間并完成更細(xì)致的篩分。有兩種方法目前用于提高篩選效率78。第一種方法是材料從多個入料口添加到振動篩上。這在實際應(yīng)用是麻煩的尤其是在控制粒狀材料不同的分

48、布這方面。因此，這很少用于實際生產(chǎn)。第二種方法是采用新的篩選設(shè)備，例如一個等厚振動篩。新的振動篩的表面運動使材料保持相同，或者增加厚度。它達到一個更理想的運動。等厚振動篩的主要問題是,它涵蓋了一個更大的區(qū)域,結(jié)構(gòu)復(fù)雜,難以維護。一個結(jié)構(gòu)簡單切具有良好的篩選效率的振動篩仍然是必需的。我們設(shè)計了一個基于理想振動篩運動軌跡的新的變橢圓軌跡振動篩用于原煤分類。振動篩的大小為3.6 m×7.5 m，進料粒度是0到50毫米和分類粒度是6毫米。橢圓軌跡振動篩結(jié)合了圓軌跡振動篩和直線振動篩兩者的基本優(yōu)勢910。確切地說，橢圓軌跡的長軸決定材料的運送速度，短軸影響材料的松散程度。3 變橢圓軌跡振動篩的

49、動力學(xué)模型分析我們使激振力偏離中心，來改變新的振動篩的運動模式。隔振彈簧的剛度矩陣并不是零，在這種情況下,振動系統(tǒng)有多個自由度。小的橫向搖擺被忽略來簡化研究。運動被認(rèn)為是一個剛性梁的縱向?qū)ΨQ平面上的線性振動。在每個點的振動是平移重心和振動篩重心的結(jié)合。先前的研究忽略了振動篩水平方向上的彈性力與豎直方向上的擺動3,11。由三個耦合垂直、水平和擺動方向自由度的微分方程組成一個精確的動態(tài)模型。圖2 振動篩的數(shù)學(xué)模型振動篩的數(shù)學(xué)模型如圖2所示。重心被作為一個靜力平衡直角坐標(biāo)系的原點，與平面上的剛體運動相一致12。使用重心坐標(biāo)(x,y)和擺動傾斜角在義坐標(biāo)聯(lián)立微分方程可以寫成：式中M是振動篩的質(zhì)量相對于重心的慣性矩，x和y表示在x方向和y方向上的位移，和表示x方向和y方向的速度，和表示在x方向和y方向的加速度，為振動角位移，是安裝傾角，