The Characteristics Research And Numerical Simulation Of Electrolyte Flow Field For Three-dimensional Complicated Surface In Electrochemical Machining

With the development of modern manufacturing industry, there are more and more workpieces with complicated structures and hard-to-cut materials. The electrochemical machining(ECM) is one of main methods for difficult-to-cut conductive materials and complicated surface workpieces with relatively high machining efficiency and good surface quality. And there is less loss on cathode theoretically. Because of difficulties in researches of the forming laws for complicated surfaces, the problem of low machining accuracy exists.In ECM process, the flow field distribution in the inter-electrode gap is one of the important factors to affect the processing quality. Besides the influence of electrolyte flow field, the electric distribution and electrochemical reaction will interactive effect the forming process. Therefore it is a multi-physical field in the inter-electrode. Research on characteristics and distribution of flow field for complicated inter-electrode is helpful to grasp the mechanism of electrochemical machining process and even to improve the machining precision and surface quality.In the thesis, the research object is a compressor blade. In ECM process the curved blade body and its platform are shaped together. Firstly the “L” shaped model of interelectrode is built. The integral flow field model is divided into M blocks and N layers based on the discrete thought, to study the flow field characteristics and distribution in the “L” shaped inter-electrode. In every discrete model the dynamic equations of the flow velocity, pressure, temperature and other parameters of electrolyte are established according to fluid mechanics theories. Based on the electrochemical theory, the main parameters affecting flow field characteristics are substituted into calculation model of electrical conductivity. The distribution figures of the electrical conductivity of the “L” shaped flow field are obtained by the MATLAB software. In the complicated curved inter-electrode gap, the electrical conductivity varying with different spatial position approaches the practical condition.From above theoretical analyses, the electrolyte velocity and pressure distributions in the “L” shape gap are simulated by software Fluent. The simulation results show that, the flow field parameters' distributions in the abrupt curvature area have obvious differences with those of other area. According to the Momentum Theorem of the Fluid Mechanics,the change mechanism of velocity and pressure in the big corner of flow field are investigated based on the extrusion and momentum effect.In order to reduce the possibility of “dead water zone”, on the basis of traditional flow field structure, linear transitional flow field and arc transitional flow field are proposed. By comparing the distributions of velocity and pressure in different flow models, the structure of the electrolyte flow field is optimized. The diffluent channel is added to avoid the possibility of “negative pressure zone”.Finally, the relationship between the initial flow velocity, pressure, backpressure and the average velocity, average pressure, minimum pressure is built. And the corresponding sensitivity curve are obtained by the software Fluent. Taking the average velocity and minimum pressure of electrolyte for optimization objective, the initial values of electrolyte flow field are determined by the method of respond surface design.In this thesis, the electrolyte flow field characteristics and the distribution in three dimensional complicated curved inter-electrode are studied and numerical simulated. They are exploratory researches, which will lay the foundation for further perfecting the forming law theories of the electrochemical machining.