1、毕 业 设 计（论 文）外 文 参 考 资 料 及 译 文译文题目： Dynamics and screening characteristics ofa vibrating screen with variable elliptical trace 变椭圆轨迹振动筛的动力学和筛选特性学生姓名： 学 号： 专 业： 所在学院： 指导教师： 职 称： 20xx年 2月 27日Dynamics and screening characteristics ofa vibrating screen with variable elliptical traceAbstract: the ideal mo
2、tion characteristics for the vibrating screen 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 vibrat
3、ing screen was analyzed.Kinematics parameters 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 amplit
4、ude,movement velocity and throwing index,of 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 effec
5、tively improved.Keywords:variable elliptical 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 screen
6、ing tools. Vibrating screens, such as linear 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
7、low screening efficiency. Augmenting the throwing 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 thi
8、ckness34.Different parts of the vibrating screen 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 va
9、riable elliptical trace2.1 Screening characteristics 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 e
10、nd .The energy imparted to the material particles 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 screenin
11、g and lowers processing capacity 5.The decrease 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 th
12、e vibrations to the material suffers little 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 is thin .This kind of motion leads to an asymmetrical penetration along the screen surf
13、ace,which influences the screening efficiency 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 consta
14、nt bed thickness .The feed end of the screen 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
15、 screen has an appropriate throwing index and 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 screen 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 u
