Static and Dynamic Finite Elements Analysis of Main Shaft of Bulb Tubular Turbine-Generator
|School||Hebei University of Technology|
|Course||Mechanical Design and Theory|
|Keywords||bulb tubular turbine-generator main shaft finite element method static strength analysis modal analysis MSC.NASTRAN UG|
Turbine-Generator machine set is the crucial equipment of waterpower. Bulb Tubular Turbine-Generator is the eximious type that develops the hydraulic resources of low headwater. With the development of the national economy of our country, among the hydraulic resources that can be developed in economic developed coastal area and plain area, power stations of high and middle headwater have been developed completely step by step. To meet the demand of power with fast economic development, the development of the hydraulic resources of low headwater have mentioned agenda. It is benefit to improve the level of designing this type and production efficiency if the thought of Finite Elements Method and Optimization Design combined with engineering analysis software is applied into development and design of Bulb Tubular Turbine-Generator.In this paper, main shaft, one of the key parts of Bulb Tubular Turbine-Generator, is analyzed with Finite Elements Method and the Theory of Modal Analysis combined with UG and MSC.PATRAN/NASTRAN, mainly static strength analysis and modal analysis.Firstly, according to the actual structure of main shaft, three dimensions substance geometry model is built with UG, and the relative small structures are left out to predigest the model. Because of need of Finite Element Analysis, the model is divided into three parts, and left out the holes on flanges. Then the solid geometry model is entered into MSC.PATRAN to do the pre-treatment of FEA. It is disassembled by ten-noded tetrahedron elements. At the same time RBE3, a type of rigid element, and MFC (Multi-point Constraint) is applied to imitate the distribution load on flange plate that transmitted by bolts so as to make the loaded condition of main shaft accorded with actual condition more.Secondly, static strength of main shaft is analyzed and calculated with MSC.NASTRAN to gain the stress distribution and deformed state of main shaft. Analysis result shows: the stress on the part of transition from flange to shaft body is greater and more complex; by contrast with material submitted stress limit, strength reserve of main shaft is still greater. In a word, main shaft meets the requirement under various static loads.Finally, on the basis of the reasons of vibration of main shaft, its modes are analyzed with MSC. NASTRAN. There are 6 modes in 0-300 Hz scope, corresponding 6 natural frequencies and 6 normal mode of vibration. By analysis, it is known that there is not the condition that each part of main shaft at the same time vibrates in calculating frequency scope, but mainly local vibration and curved modal shape. In the normal working conditions the possibility that main shaft occurs resonance is very small.The research for main shaft has laid certain foundation for analysis with FEM and optimization design of overall machinery and others parts and calculation of vibration responds.