汽缸结构上下缸接触的有限元分析

FINITE ELEMENT ANALYSIS FOR THE CONTACT STATE OF THE TOP AND BOTTOM CYLINDERS OF THE TURBINE STRUCTURE

采用有限元软件MSC/NASTRAN计算分析了汽轮机汽缸结构上下缸接触状态的应力分布和变形.分析了汽缸在温度场作用下以及温度场同内压联合作用下的应力分布情况,重点分析上下半缸的螺栓连接面——中分面上的应力和变形情况.建立了气缸三维实体有限元分析模型,并对每根连接螺栓均建立了模拟模型.分析结果表明,同内压引起的应力相比,热应力是缸体中应力的主要成分.当内外壁温差达到100℃时,缸体中最大应力为1230 MPa,出现在约束处应力集中部位,缸体绝大部分应力水平在600-700 MPa;汽缸外壁温度为25℃时,缸体中最大应力为1080MPa,缸体绝大部分应力水平在100MPa,得出减小汽缸内外壁的温差能有效减小缸体中应力的结论.分析表明,缸体轴向最大伸长量为2.55 mm,横向最大变形为2.02 mm.z向最大位移为1.24 mm.中分面有分离,但分离程度较小,分离值均在10-3mm量级上.

In this paper, the finite element software MSC/NASTRAN is adopted to calculate and analyze the stress and deformation distributions of the cylinder. The effect of the temperature field, and the joint action of the temperature field and the internal pressure are analyzed with particular emphasis on the linking surface-halved surface on the bolt of the half cylinder in the top and bottom. The 3D body model for finite element analysis and the simulating model for all link bolts are established. Analysis results show that the thermal stress is the main part of the stress in the cylinder, as compared with the stress caused by the internal pressure.When the difference of the inside and outside wall temperatures has reached 100℃, the maximum stress is 1230 MPa inside the cylinder body, in the position of the stress concentration, and the stress levels in most places of the cylinder body are about the 600-700 MPa. When the outside wall temperature is 25℃, the maximum stress is about 1080 MPa inside the cylinder body, the stress levels in the most parts of the cylinder body are about 100 MPa. Therefore, when the temperature difference of the inside and outside walls of the cylinder was reduced, the stress inside the cylinder body can be efficiently reduced.The analysis shows that the maximum axial deformation is about 2.55 mm in the cylinder body, the maximum horizontal deformation is about 2.02 mm. The maximum deformation in the Z axis is about 1.24mm. A separation appears upon the halved surface, but the separation degree is small and in the order of 10-3 mm.