Research On The Digital Machining Simulation For Francis Hydro Turbine’s Blade

Nowadays, with the shortage of conventional energy and the deterioration of environment, the hydropower resources has received the recognition and favor in many countries. And hydropower mature technology has the advantage of low cost and renewable, which can help to alleviate the problem of shortage of electric power in the world. At the same time, more and more countries have to speed up the pace of hydropower development. We can think of that the hydroelectric power will become the mainstream of power industry in China.Hydraulic turbine is essential part of the power-generation, and the runner blade is the core component of the turbine. So the manufacture quality and accuracy of the turbine runner’s blade will directly affects safety, security, and accurately smooth and efficient operation. Hydro turbine blade is a very complex body closed by sculptured surfaces, and the traditional manufacturing process, which is called sand mold casting, grinding wheel relief grinding three-dimensional model test, can’t ensure the machining accuracy and quality. In recent years, the technology of large sized turbine blades with multi-axial NC machining tool has been researched by hydraulic turbine manufacturers. In NC machining process of the blades, a step called "trial machining" is still required for the verification and modification of the process procedure and NC programming, which is not only cost very high but also lower the productivity. The digital machining simulation technology is a powerful tool to solve these problems, which can simulate the process of machine moving and cutting on the computer.In this paper, which is on the basis of the computer aided geometric design, NC machining simulation and the secondary development of software, a large kind of Francis turbine blade was used as research object. Firstly, the3D geometric model of the blade and the corresponding machine should be build, and so did the five coordinate’s blade NC machining tool path planning and its post processing; On this basis, the digital processing simulation environment of the blade was constructed and the digital processing of the blade geometry simulation was conducted. At last, on the basis of the secondary development of the professional software, an numerical simulation method that combined CNC geometric simulation with physical simulation was explored, and the NC machining simulation and cutting force simulation of large Francis turbine blade were realized by this way. It can optimize the cutting parameters and improve the processing quality of the blade.The results of this paper not only can be used to describe the space geometry motion of machining simulation, but also it can be used to simulate the blade’s material removal process, and predict the performance of the machining process, machining quality and machining efficiency. This achievement is an effective method of multi-axis NC machining for the blade’s auxiliary programming, to a certain extent it can instead of try cutting or machining process. By this, the manufacturing cost has been greatly reduced and the safety of process system has been guaranteed. It has great significance in improving the manufacture technology of hydraulic turbine in our country.