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April 24, 2020
Research on Key Technology of Design and Manufacture of Hydro Pelton Turbine Runner
The hydropower energy industry occupies an important position in the national strategic emerging industry development plan. High-head hydraulic power generation must use impact type hydraulic turbine units.The design of the key components of the water bucket runner and the overall CNC machining technology are currently not perfect in China. The existing problems are as follows: how to realize the overall CNC machining of the water bucket under the premise of ensuring the hydraulic performance of the water bucket; how to predict the stability of the water bucket plunge milling process and optimize the milling parameters; how to solve the extra long tool holder in the water bucket plunge milling process (Length ratio up to 1:20) processing chatter problem to improve the efficiency and quality of the water bucket processing, this paper carried out the following research in response to these problems. In order to realize the optimization of the manufacturing-oriented water bucket structure, a numerical simulation analysis based on CFD (Computational Fluid Dynamics) was carried out for the interaction between the bucket line and the jet, and the hydraulic performance of the water bucket was optimized. At the same time, the structural optimization design of the uniformity of curvature of the bucket surface and bucket root depth, bucket root depth and bucket root thickness is also carried out, so that the bucket design can meet the hydraulic performance and strength characteristics, and at the same time can have better CNC machining Craftsmanship. Through the optimization of the root structure of all the buckets, the comprehensive stress and alternating stress of the bucket are greatly reduced. Aiming at the problem that the cutting tool vibration is prone to occur when the ratio of tool length to diameter during plunge milling, cutting force prediction and cutting dynamics are studied. Based on the cutting principle, a prediction model of plunge milling cutting force was established. Compared with the results of finite element analysis and actual cutting verification, the model has high prediction accuracy; based on the vibration theory, the three-dimensional stable domain equation of plunge milling machining was established. The influence of various factors on the stability of the water bucket plunge milling process on the machining stability is described. The above work provides a means for the optimization of the water bucket plunge milling process.
According to the characteristics of the water bucket structure and plunge milling process, an analytical model of the tool holder vibration was established. The finite element method was used to study the tool holder geometric structure parameters, the structure of the hole and taper handle, the tool holder material and other factors on the tool holder deformation and vibration. Affected by the law, a new structure of anti-vibration tool holder was developed. The actual cutting application proved that the tool holder has good vibration suppression effect. This work has important guiding significance for large aspect ratio cutting and cutting tool design. Through the analytical calculation of the cutting thickness in the process of plunge milling, the regional planning of the CNC machining of the runner was realized from the perspective of priority in processing efficiency. An optimized solution is proposed for the key technological problems in the overall processing of impact turbine runners. The actual processing results show that the quality and efficiency of the water bucket processed by this process are at the leading level. The results of this research can provide important technical support for the industrialization of the overall CNC machining of the runner. By comprehensively considering the key issues of the design and manufacturing of the water bucket runner, the integrated research results have formed an independent intellectual property.
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