| Aeroengines seem to be the hearts of aircrafts. From a certain angle, the development of aeroengine represents the whole science and technology strength for a country. Aerospace of China has gained great development and the research of aeroengine has made rapid progress in recent years. Aeronautical manufacturing technology plays an important role in aeroengine development. Blades are very important parts of aeroengine. They impart kinetic energy and redirect the flow to the next stage at the optimum angle. Because of the special characteristics of turbine blade and the hardness of manufacturing, the processing method of blade has been the key point of research in many years. Being a non-mechanical metal removal process, electrochemical machining (ECM) provides an economical and effective way for machining heat-resistant, high strength materials into complex shapes which are difficult to machine by conventional method, so it becomes the main method to process turbine blade. With the raise of aeroengine performance, the changement of the blade materials and profiles, and the improvement of machining accuracy, ECM has faced a higher challenge. The research emphases is to improve the surface quality and machining accuracy of blade in ECM, shorten the period of blade making, reduce the jamming and raise the automation level of blade processing which are the main research contents in this paper.According to the research actuality of blade ECM, the present study focused on the several key technologies and difficulties of blade ECM in order to improve the potential ability of ECM further and settle the foundation for the following study. The main research contents of this paper include:1. The idea of Digital Description to Full Process of blade ECM was presented. Different from the traditional definition of omnidirectional blade ECM which machined the several parts of blade simultaneously, the meaning of this idea is to make the full process of blade ECM under the computer control. All the links of blade ECM, such as blade modeling, designation of flow field and cathode, optimization of feeding angles, blade experiments and amendment of cathode, combined firmly with computer technology. The aim is improving the automation level of blade ECM and reducing the human disturbance.2. A flexible 3-Electrode feeding ECM method was investigated. The anode was moved during the process and the feeding angles of two cathodes were fitted by the velocities of cathodes and anode in order to overcome the defects of traditional blade ECM which includes fixed feeding angles, tapered platform and two time etching. The relationship of machining accuracy with the feeding angles and workship clamping angle was discussed. The optimization criterion of these angles was given according to the different accuracy requirements of profile and platform. The optimal angle combination was also got in this paper.3. A new electrolyte flow mode named"active distributary mode"was proposed. Since flow field is a critical factor to affect the ECM process stability and the accuracy of blade, a two-dimensional incompressible flow field model describing electrolyte flow in the interelectrode gap was developed. The flow mode was analyzed by finite element method and was contrast with the traditional lateral flow modes. Electrolyte flowed from the platform of blade and was divided into two parts to flow across the convex and concave parts of blade individually considering the characteristics of electrolyte flow and the different accuracy requirements of blade profile and platform. The performances of electrode corners starved of electrolyte were studied and diversion block was designed to solve the problem. According to the continuity equation, momentum equation, energy equation and the Blasius formula of flow field, the characteristics of electrolyte flow between the gap of cathode and anode were analyzed by using forth order Runge-Kutta method with varying step size. The relevant clamping fixture which makes the flow tunnels was also designed in this paper.4. The variable gap amendment method of cathode and the cathode modification model using BP neural network were proposed. The corrections data of cathode were variable based on the value of interelectrode gap and were used to the cathode design. The approximate formula of cathode corrections data which were calculated along the contours line was given and the experimental method of interpolation approximation was also adopted. The digital cathode modification model was developed using BP neural network on the basis of the method of the variable gap modification of cathode and its experimental data. The network was trained by the experimental data which is normalized, and then it was simulated. The simulation results showed that the model has a good prediction effects.5. The blade ECM machining system was perfected. The electrolyte circulation system and CNC system were built based on the blade ECM machine tool. The software system of blade ECM was designed by using the virtual instrument technology and Labview development platform which including Flexmotion module.6. Some blade ECM experiments were carried out. The comparative tests of different feeding angle combinations were developed. The results showed that with the optimal angle combination the accuracy of blade profile could be kept and the accuracy of blade platform could be improved. The experimental investigations of flow field were carried out in order to evaluate the rationality of the flow mode. It revealed that the surface roughness could be improved to 0.36(Ra) with the new flow mode. On the contrary, the surface roughness of the blade profile with the traditional lateral flow mode was 1.67(Ra). The machining accuracy could also be enhanced. The experimental investigations by using the cathode amendment method were carried out. The results reveal that the accuracy of blade was enhanced to 0.05mm by using the method 3 times. Furthermore, the efficiency and automation level of cathode amendment could be improved by using the BP neural network cathode modification model.7. The idea of Digital Description to Full Process of blade ECM was applied in the development of a certain aeroengine blade. Because of the high requirement of machining accuracy and the special thin and distortion of blade profile, it was difficult to be made by ECM. The technologies and methods above mentioned were applied in the process. The whole making process, such as blade modeling, designation of flow field and cathode, control of making velocity, optimization of feeding angles, designation of flow field, blade experiments and amendment of cathode, was controlled by computer technology. The results revealed that the machining accuracy of blade profile could be improved to 0.05mm with the technologies and methods above mentioned.
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