The design of the aerodynamic performance parameters of the ventilator is an important part of the design of the ventilator. In the past, most of the pneumatic parameters were obtained by manual calculation, with large workload, low precision and long cycle. At the same time, after the design of the aerodynamic parameters is completed, during the process of drawing the blade section, a large amount of dimensional data is completed by manual input, and the work repetition degree is high and error-prone, thereby prolonging the design cycle and reducing the work efficiency. By using Visual Basic 6.0 (abbreviated VB) programming development tool to compile the aerodynamic parameter design program of the fan, using AutoCAD VBA secondary development technology, the large amount of dimensional data obtained by the aerodynamic parameter design program is directly drawn into AutoCAD graphics, from parameter design to Through the whole process of automatic drawing, at the same time, through repeated calculation of key parameters, the parameters are continuously optimized, thereby shortening the calculation time, speeding up the development cycle, and improving the reliability and effectiveness of the design and drawing of the aerodynamic parameters of the fan. 1 programming ideas 1.1 The lift theory of the isolated airfoil The lift theory and experimental data of the isolated airfoil are one of the main basis for the design of the axial flow fan. In order to study the flow of airflow in an axial flow ventilator, in order to facilitate the study of the flow of airflow on different radial flow surfaces, it is necessary to develop the toroidal cascade on the same radius into a planar cascade, which is called Primitive level. The actual full pressure of the ventilator (considering flow losses) is [1] 1.2 choice of programming language Visual Basic is a visual programming language based on Basic. It is an object-oriented integrated development system with the advantages of simple and easy to use, object-oriented, event-driven, and visual interface. From numerical computing, database management, electronic communication, multimedia to the Internet, you can use VB to develop. VB makes it easy to compile Windows-oriented applications. Users don't have to think too much about the details of visual implementation and concentrate on writing the main algorithm of the program. Based on these advantages, the author uses the Visual basic 6.0 programming tool to develop a ventilator aerodynamic parameter optimization design program. 1.3 AutoCAD drawing software AutoCAD is a series of graphic design software developed by Autodesk in the United States. Its 2D drawing function and 3D modeling function are very powerful, and it is widely used in mechanical graphic design. VBA (Visual Basic for Application) is a programming language with a completely object-oriented architecture. Because of its ease of use in development and its own powerful functions, many applications are embedded in the language as a development tool. Autodesk also built VBA development tools in AutoCAD R14.01. It also provides ActiveX Automation object model for VBA development. It provides programming control of AutoCAD through ActiveX Automation interface 121 to further realize parametric automatic drawing. This program takes full advantage of this advantage to achieve the entire process from data entry to automatic drawing. 2 programming points 2.1 system structure diagram In order to make the program development process and the fan design process consistent, the program is divided into four modules, as shown in Figure 1. 2.2 Visual control selection and application Using VB's own system controls to write visual operator interfaces not only makes the programming work more intuitive, but also makes it easy for users to understand and use these Windows-style operator interfaces. This program makes full use of SSTab control to realize the input advantages of a large number of different types of data on the same interface. It is used as the main body of the program, and a large number of application text boxes, labels, combo boxes, etc., common dialog boxes to complete data input, selection and Display, making data entry and display more convenient and intuitive. 2.3 parameterized automatic drawing The aerodynamic parameters of the fan blades and the data of each section of the blade are calculated by the program, and then the AutoCAD VBA is used to parameterize the blade section parts automatically. When you use it, you can automatically draw the required graphics by simply entering the necessary original parameters according to the instructions and requirements on the user interface. If you are not satisfied with the graphical results, you can redraw after changing the parameters, or you can directly modify the subtleties in the AutoCAD drawing environment. The block diagram of the parameterized automatic drawing event of this program is shown in Figure 2 [2]. 3 practical application of the program Here, an example is given to illustrate the running conditions of the program and the functions of each module. The design of the counter-rotating axial flow fan is taken as an example. The design parameters are: full pressure l400Pa, air volume 18m3/s. 3.1 basic parameter input module The basic parameter input module is used to input the fan design parameters and calculate and determine the structural parameters of the fan. At this stage, through the characteristic parameters such as specific number of revolutions, total pressure coefficient, flow coefficient, peripheral speed, and dimensionless axial velocity, compare the typical products with excellent performance and the empirical data of fan design data to judge whether the design is reasonable, if the parameter deviation is better. If you are large, re-enter the relevant parameters and perform the calculation again until it is reasonable. When the first stage is selected, the result of the subsequent calculation is the aerodynamic parameters of the first stage impeller of the fan. Similarly, if the second stage is selected, the result is the aerodynamic parameters of the secondary impeller, as shown in Figure 3. 3.2 Impeller pneumatic parameter calculation module This module is used to determine and calculate the aerodynamic parameters of each section of the blade. According to the radial balance condition of the fan, when the aerodynamic design of the fan is carried out, it is divided into two methods: equal ring flow type and variable ring flow type. The equal-volume axial flow rate Ca(r)=constant and pressure P(r)=constant has the advantage of convenient design. It can achieve better results for the axial flow fan with larger hub. . In the variable loop design, the total pressure P is generally increased along the leaf height to make full use of the peripheral speed of the tip portion. The commonly used variable loop flow pattern is Δcurn=constant (rn is a coefficient), and the hub is relatively small. Flow ventilator with variable ring design prevents blade distortion and is easy to manufacture. This program adopts the equal loop design method. In the equal loop design, the load factor τCy is gradually increased from the tip to the root of the blade. In order not to make the cascade r at the root of the blade too large, when the lift coefficient Cy is selected, it can be The tip of the leaf to the root of the leaf gradually increases the lift coefficient. After the Cy value of each section is determined, the corresponding angle of attack α can be selected according to the Cy-α curve of the standard airfoil, and then the factors such as the thickness of the cascade and the strength of the blade are used to judge whether the designed leaf size parameter is reasonable, as shown in Fig. 4. . 3.3 Each section geometry display output module This module is used to display the geometry of each section. The geometry of each section of the airfoil determined by the aerodynamic design is calculated and displayed based on the coordinate parameters of the selected standard airfoil (see Figure 5). The standard airfoil used in this procedure is the CIARKY airfoil. After the design of the blade aerodynamic parameters is completed, the calculation results can be stored in two forms: paper print storage and computer file storage. 3.4 parameterized automatic drawing module Click the “AutoCAD and Create Drawing File†button to launch the AutoCAD drawing software. Click the “Draw AutoCAD Drawing†button to draw the graph of each section (see Figures 6, 7). 4 Conclusion The program uses Visual Basic 6.0 as a development tool, and the operating environment is the Windows operating system. Through practical application, the program can repeatedly calculate key parameters, obtain optimized aerodynamic performance parameters, and complete the whole process from design parameters to automatic drawing, realize parameter optimization and docking of ventilation machine aerodynamic parameter design process and drawing process. Shorten the development cycle and improve the design and drawing efficiency of the aerodynamic parameters of the ventilator. The program has achieved satisfactory results in the design of impeller parameters of dozens of main ventilators and local ventilators. The parameters in this example are the design parameters of FBDCZN010/2×22 kW main ventilator, and the actual measurement after making the prototype. The highest total pressure efficiency can reach 85.2%. Practice has proved that the program is simple, practical and operable. Foldable Mini Trampoline,Trampoline With Enclosure,Bowl Trampoline With Net, fitness trampoline Jiangsu Baoxiang Sports Equipment Co., Ltd , https://www.skyboundbx.com