Computer Aided Design of Three-legged Settling Centrifuge

Zhang Jianwei Gao Junyan Yang Yuanfeng Cong Lei 【Abstract】The computer-aided design of three-legged sedimentation centrifuge was carried out by artificial interaction design system. The article describes the steps of this auxiliary design, the basic design ideas, and the functions of the design system. Key words: centrifuge; CAD; optimization design Centrifuges generally refer to machines that use centrifugal force to achieve solid-liquid, liquid-liquid, liquid-liquid-solid separation operations. It is mainly used in processes such as dehydration, concentration, separation, clarification, purification and solid particle grading. It is widely used in various engineering fields. The three-legged centrifuge is applied to Zui for a wide range of centrifuges. It has a wide range of applications and is highly adaptable to materials. The number accounts for about 50% of the total of various separation machines. The three-legged sedimentation centrifuge often needs to be modified for its different materials. Computer-aided design technology is an emerging design method. CAD technology combines the speed and accuracy of the computer with the logical thinking and comprehensive analysis capabilities of the designer, which will greatly reduce the labor intensity of the designer, speed up the design process, and improve the design. quality. This design method has been applied to many mechanical designs, such as gear reduction boxes, drums, springs, etc. The computer aided design technology is applied to the design of the three-legged sedimentation centrifuge, which greatly improves the design efficiency and optimizes the design parameters, which provides the possibility to obtain the design result optimized by Zui. 1 Design task analysis 1. 1 structural composition The three-legged sedimentation centrifuge consists of a drum, a spindle, a bearing, a housing, and a belt drive assembly (pulley and belt). 1. 2 Initial basic design data and database establishment The basic parameters of the three-legged sedimentation centrifuge include: the diameter of the drum, the working speed of the drum, the large amount of feed of the drum, the material density, the solid-liquid ratio of the material, and the start of the centrifuge to reach the working speed from standstill. Time and so on. For these parameters, the design software uses the FOXBASE database management system to store them, which are called by character variables when used. This allows a large amount of known data to be automatically queried by the computer, reducing unnecessary (massively repeated) human-computer interaction processes and increasing the computational speed. 1. 3 basic design ideas The basic design idea is that each part of the computer participates in the design process, and the process is shown in Figure 1. Based on the design requirements and basic raw data proposed by the designer, the computer performs a large number of rapid analysis and calculation optimization design until the drawing work. According to their own design experience, the designer judges whether the design result meets the predetermined requirements, and proposes the information of the modification plan according to the way of man-machine dialogue, so that the traditional manual calculation and manual drawing design process are used with efficient man-machine. The combination design process is replaced. For a complex structure such as a three-legged sedimentation centrifuge, the principle of distributed design and common area storage data is adopted. 2 Design system functions The overall function of the computer aided design system was determined by structural analysis of the three-legged sedimentation centrifugation. It includes the following four parts: 2. 1 Zui optimization design of centrifuge drum 2. 1. 1 Determination of the objective function The objective function of the centrifuge drum optimization design is selected as the quality of the drum. The quality is small, on the one hand, it can save the machine cost; on the other hand, it can reduce the starting power of the centrifuge and reduce the consumption. 2. 1. 2 Determination of constraints Constraints include three aspects: (1) Stress constraints Σmax ≤[σ] Σmax is the zui large stress of the drum, which is obtained by an axisymmetric finite element calculation program. The finite element program has been verified by a drum strain test. [σ] is the allowable stress of the drum material, [σ] = min{σS/ ns , σb/ nb} , and the required material is selected according to the separated material, thereby determining the yield limit, strength limit and safety factor of the material. . Then determine the allowable stress. (2) Displacement constraints Umax ≤[ U ] That is, the large displacement of the Zui of all points is less than or equal to the allowable displacement. (3) Geometric constraints Also known as rigid constraints. V min ≥[ V ] 2. 1. 3 graphic output Optimize the calculated parameter results, visually display the graph with a computer, and output it with a plotter. At the same time, for the optimized design of the drum, the moment of inertia of each part is calculated and summed into the total moment of inertia, and the data is stored in the common data area. 2. 2 Determine motor power The calculation of motor power is based on the following aspects of the overall motor power consumption: (1) The power consumed to start the drum to reach the working speed. (2) The power consumed to start the material to reach the working speed. (3) The power consumed by the drum and air friction. (4) The power consumed by the friction between the shaft and the bearing. The data of the common area is called during calculation, and the result calculated after the Zui is guided by the control module to the manual discriminating function area, and the given data of the motor sample is discriminated to select a suitable motor, and the relevant data of the motor is re-stored. Common data area. 2. 3 belt drive design calculation and pulley design The necessary motor data and structural data are transferred from the common area, and the design calculation of the belt drive is performed. After the Zui, the number of the belt, the center distance and the tension of the belt with the shaft are stored in the common area, and the pulley is carried out. Structural design, drawing a wheel structure diagram. 2. 4-axis system design calculation 2. 4. 1 axis design calculation According to the material and structural requirements of the shaft, part of the data of the common area is called to determine the diameter of each part of the shaft, and the strength of the shaft is accurately checked. 2. 4. 2 Critical speed calculation of the shafting system The centrifuge is a high-speed rotary machine, and the spindle has a high rotation speed. If the working speed of the spindle is close to the critical speed of the shaft system, resonance may occur, and the rotating member collides with the stationary member, causing a serious accident. The analytical method is used to calculate the critical speed of the single-rotor shafting system of the centrifuge. It is judged whether it is feasible compared with the working speed of the shaft. If it is not feasible, return to section 3.4.1 to modify the structural size of the shaft and re-check. Until feasible. 2. 4. 3 Selection and calculation of rolling bearings The bearing is selected based on the load and the speed of the shaft, and then the program of the rolling bearing check is run to output the life of the bearing. Manual judgment is feasible. The whole design system is a basic automatic design system. The host computer is a microcomputer with a memory of 64M or more, and is equipped with a drawing software resource UNIX operating system. 3 module division The program system is divided into a calculation part and a graphic part. The functional blocks of the calculation section are shown in Figure 2. (1) Optimized design and moment of inertia calculation of OPTB drum (2) MPC motor power calculation (3) GBD belt drive design calculation (4) GSH shafting calculation These operations are in the second layer of the program system structure diagram, and each of them can be further decomposed into smaller modules by a top-down method. Figure 3 takes the optimized design drum as an example and gives the module further. break down. 4 Conclusion The design of the three-legged centrifuge is itself a more complex design. The computer-aided design work is also complicated, and it is quite difficult or even impossible to implement with a fully automatic continuous design system. Therefore, the human-computer interaction design system is used here. When each staged work result is evaluated, selected, and satisfied by the designer, the next step is performed. If it is not satisfied, it will return and work again until a satisfactory result is obtained. During the running of the program, when the designer needs to operate, the menu for selection is displayed on the display, which is convenient for the designer's operation.

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