大型双质体反共振振动筛的设计与动力学优化

发布时间：2018-08-28 09:00

【摘要】：振动筛作为一种常见的工程机械,由于其操作简单,运行可靠,工作效率高等优点,在我国众多的工业生产领域得到了广泛的发展和应用,振动机械的出现极大的促进了工业生产的发展,提高了企业经济效益。在我国经济快速发展的同时,对于能源的需求量也在日益增长,能源消耗量大大增加,带来的环境问题也愈加严峻,反过来制约着经济的发展。对于一些传统的振动机械,由于其高耗能,低效率等特点,已经不符合我国当前节能低碳的经济发展方向。相比之下,反共振振动机械的优点更加突出,其具有寿命长、重量轻、噪声低、节能环保等优点,符合我国当前经济发展低碳节能的要求,因其广阔的发展和应用前景,反共振振动机械越来越受到人们的重视。将反共振理论应用于一种新型双质体反共振振动筛的设计,并对其进行充分的理论研究和性能仿真,主要进行了以下工作:首先,建立双质体反共振系统力学模型,对振动系统进行动力学响应分析,得到上、下质体的位移公式。为了便于研究振动系统的振动机理,引入反共振系统参数:固有频率比,质量比,阻尼比,反共振频率比等。通过MATLAB软件对振动系统进行仿真,得到各反共振系统参数对于质体位移的影响规律。分析了“工作点处工作振幅变化最小”和“工作点附近振幅变化最小”两种情况下的参数选择方法,在此基础上,确定了参数优选方法,为接下来振动筛结构设计中的动力学参数选择提供了理论指导和设计依据。其次,仅以悬臂筛网为上质体,即在保留悬臂筛筛面结构的基础上,提出以悬臂筛网作为参振体的新型反共振振动筛,依据《振动筛设计规范》和《GBT 26506-2011悬臂筛网振动筛》等规范和标准,对振动筛主体结构:悬臂筛网、筛箱、横梁、机架等进行结构设计,并基于反共振理论对一些运动学参数和动力学参数的选择进行了详细计算,用材料强度准则对一些重要零部件做了强度校核。并基于反共振理论,依据前面所提出的参数选择方法确定反共振系统参数。针对筛网和筛箱的弹簧连接问题,设计出两种结构,分别以板弹簧和螺旋弹簧进行连接。考虑到板弹簧结构简单,承载能力强,便于安装;成本低,便于维修更换;同时板弹簧可以起到导向和传递激振力的作用,相比螺旋弹簧弹簧,不需要导杆和套筒,使结构得到简化。经对比分析选用板弹簧作为主振弹簧,设计出以板弹簧为主振弹簧的悬臂筛网为参振体的新型反共振振动筛。第三,为了研究所设计双质体反共振振动筛的弹性动力学性能,将三维模型适当简化后导入ANSYS Workbench进行有限元分析,包括静强度分析,模态分析,谐响应分析。静力学分析得到振动筛结构的静应力和静变形,并依据材料许用静强度准则,判定振动筛结构静强度满足要求;通过模态分析得到筛网和筛箱的固有频率以及各阶振型,激振频率16Hz避开了结构共振点,且相邻两侧共振峰间隔很大,表明正常工作状态下可避免发生共振。在谐响应分析中,对反共振点进行了验证,并分析了共振状态下筛网和筛箱的力学性能,依据材料许用强度准则,判定振动筛共振状态下动强度满足要求。通过瞬态动力学分析,得到了振动筛在简谐激振力作用下的动应力和动变形,,根据振动机械动强度准则,判定振动筛满足动强度要求。第四,运用动力学软件ADAMS建立虚拟样机模型,并进行启动过程和停机过程仿真模拟,得到上、下质体位移响应曲线和隔振弹簧动载荷变化情况。仿真分析验证了所选反共振系统参数的正确性以及反共振理论在本设计中应用的可行性。为了进一步研究所设计振动筛的工作稳定性,联合使用ANSYS和ADAMS,针对激振力偏离质心、物料量波动、主振弹簧刚度不均及两电机转速不同步对振动筛筛分性能的影响,进行了仿真分析;针对悬臂筛网特有的“二次振动”进行柔性体动力学分析,表明悬臂筛网的“二次振动”改变筛孔程度大小为0.142%,对于所设计振动筛筛分性能轻微的促进作用,对单个筛棒进行模态分析,发现激振频率16Hz远小于筛棒第一阶固有频率215.58Hz,故振动筛反共振工作时,实现筛棒的共振是不现实的。总之,在对双质体反共振动力学特性分析的基础上,设计出一种新型双质体反共振振动筛,以悬臂筛网为参振体,最大程度的减少参振质量,降低能耗,相比同等规格的振动筛,参振质量减少70%左右,电机功率预计可降低67%左右,稳定工作基础动载荷减少79%左右。通过对振动筛有限元分析,并依据强度准则判定其结构强度满足要求。针对物料分布不均、激振力偏移质心、主振弹簧刚度不均和两电机转速不同步对振动筛的工作稳定性影响情况,进行了仿真分析。仿真结果表明:(1)为了保证筛网的正常工作和筛分效果,安装激振器时,应保证激振力偏心距不得大于0.05m。(2)所设计振动筛从空载到满载的物料增加过程中,其工作振幅和振动强度基本不变,保持良好工作状态。筛网物料堆积在筛网一侧时,会增大筛网左右摆动,同时筛箱在Y方向发生拍振动。物料堆积在入料口处时主要影响激振力偏心距大小,同时影响反共振点位置,增大筛箱振幅。(3)当筛网两侧弹簧刚度不均时,会加剧筛网在Z方向(垂直于筛箱侧板方向)的振动,造成筛网左右摆动,同时会增大筛箱在竖直方向上的启动阶段的共振振幅。(4)当两电机转速不同步时,会出现转速差,在转速差较小时,振动筛所产生的拍振动振幅接近工作振幅,所产生的拍振动是由于频率相差较小的简谐振动相互叠加作用而成,在一定程度上增加了物料的振动强度,有助于物料筛分效果的提高。随着转速差增大,拍振动周期变短,在转速差在15.6%时,拍振动基本得到消除,但是振动强度减弱一半,则无法满足原先工作要求。针对悬臂筛网的“二次振动”进行了动力学分析,结果显示筛棒的“二次振动”对于筛分效果具有轻微促进作用,减少筛孔堵塞。
[Abstract]:As a kind of common construction machinery, vibrating screen has been widely developed and applied in many industrial production fields in our country because of its simple operation, reliable operation and high efficiency. The appearance of vibrating machine has greatly promoted the development of industrial production and improved the economic benefits of enterprises. The demand for energy is increasing day by day, the consumption of energy is increasing greatly, and the environmental problems are becoming more and more serious, which in turn restricts the development of economy. Vibration machinery has many advantages, such as long life, light weight, low noise, energy saving and environmental protection. It meets the requirements of low-carbon energy saving in China's current economic development. Because of its broad development and application prospects, anti-resonance vibration machinery has attracted more and more attention. In order to study the vibration mechanism of the vibration system, the anti-resonance system parameters are introduced. There are frequency ratio, mass ratio, damping ratio, anti-resonance frequency ratio and so on. Vibration system is simulated by MATLAB software, and the influence of anti-resonance system parameters on mass displacement is obtained. On this basis, the optimization method of parameters is determined, which provides theoretical guidance and design basis for the selection of dynamic parameters in the next structural design of vibrating screen. Secondly, a new type of anti-resonance vibrating screen with cantilever screen as the upper mass is proposed on the basis of retaining the structure of cantilever screen. Screen design specification > and < GBT 26506-2011 cantilever screen vibrating screen > and other specifications and standards, the main structure of vibrating screen: cantilever screen mesh, screen box, crossbeam, frame and so on are designed, and based on the anti-resonance theory, some kinematic parameters and dynamic parameters are calculated in detail, and some important parts and components are selected with the material strength criterion. Based on the anti-resonance theory, the parameters of the anti-resonance system are determined according to the parameter selection method proposed above. Two kinds of structures are designed for the spring connection of screen and screen box, which are connected by plate spring and spiral spring respectively. Compared with the coil spring, the guide rod and sleeve are not needed to simplify the structure. By comparison and analysis, the plate spring is selected as the main vibration spring, and a new type of anti-resonance vibration screen with the main vibration spring cantilever screen mesh as the reference body is designed. The elastodynamic performance of the double-body anti-resonance vibrating screen designed by our institute is studied. The three-dimensional model is simplified and then imported into ANSYS Workbench for finite element analysis, including static strength analysis, modal analysis and harmonic response analysis. The static strength of the vibrating screen meets the requirements; the natural frequencies and modes of the screen and the box are obtained by modal analysis, and the excitation frequency is 16Hz to avoid the resonance point of the structure, and the adjacent resonance peaks are separated greatly, which indicates that resonance can be avoided under normal working conditions. According to the allowable strength criterion of materials, the dynamic strength of vibrating screen under resonance is determined to meet the requirements. The dynamic stress and deformation of vibrating screen under the action of harmonic exciting force are obtained by transient dynamic analysis. According to the dynamic strength criterion of vibrating machine, it is determined that the vibrating screen meets the requirements of dynamic strength. Fourthly, the virtual prototype model is established by using the dynamic software ADAMS, and the simulation of start-up and shutdown process is carried out. The displacement response curves of upper and lower mass and the dynamic load changes of vibration isolation spring are obtained. In order to further study the working stability of the vibrating screen, ANSYS and ADAMS are combined to simulate the influence of the exciting force deviating from the center of mass, the fluctuation of material quantity, the uneven stiffness of the main vibrating spring and the asynchronous speed of the two motors on the performance of the vibrating screen. Mechanical analysis shows that the "secondary vibration" of the cantilever screen changes the size of the screen hole to 0.142%. For the slight promotion of the screening performance of the designed vibrating screen, the modal analysis of a single screen rod shows that the excitation frequency of 16Hz is far less than the first natural frequency of the screen rod 215.58Hz. Therefore, the resonance of the screen rod is realized when the vibrating screen is anti-resonant. In short, on the basis of the analysis of the dynamic characteristics of the dual-body anti-resonance, a new type of dual-body anti-resonance vibrating screen is designed. The cantilever screen mesh is used as the vibrating body to minimize the vibration quality and energy consumption. Compared with the vibration screen of the same specifications, the vibration quality is reduced by about 70% and the motor power is expected to be reduced by 67%. The dynamic load of the stabilized working foundation is reduced by about 79%. Through the finite element analysis of the vibrating screen and according to the strength criterion, the structural strength meets the requirements. The simulation results show that: (1) In order to ensure the normal operation and screening effect of the screen, the eccentricity of the exciting force should not be greater than 0.05m when installing the vibrator. (2) The working amplitude and vibration intensity of the designed vibrating screen are basically unchanged during the process of increasing the material from no-load to full-load, and keep good working condition. When the material is piled up at the inlet, the eccentricity of the exciting force is mainly affected, and the position of the anti-resonance point is also affected, and the amplitude of the screen box is increased. (3) When the stiffness of the springs on both sides of the screen is uneven, the vibration of the screen in the Z direction (perpendicular to the side plate of the screen box) will be intensified. When the rotating speed of the two motors is not synchronous, the rotating speed difference will occur. When the rotating speed difference is small, the amplitude of the beat vibration produced by the vibrating screen is close to the working amplitude. The beat vibration is caused by the superposition of the simple harmonic vibration with small frequency difference. With the increase of rotational speed difference, the beat vibration period becomes shorter. When the rotational speed difference is 15.6%, the beat vibration is basically eliminated, but the vibration intensity is reduced by half, which can not meet the original work requirements. Dynamics analysis shows that the "secondary vibration" of the screen rod can slightly promote the screening effect and reduce the blockage of the screen hole.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH237.6

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