【作者】 宋洋；

【导师】 程耿东；

【作者基本信息】 大连理工大学 ， 工程力学， 2009， 硕士

【摘要】 叶轮是离心压缩机中最关键的旋转部件,自身结构、工作条件均十分复杂,其工作状态直接影响到整个机组的安全。随着压缩机各种设计参数的不断提高,叶轮的运转条件和自身的力学特性也变得更为复杂。对旋转叶轮进行深入的力学分析,为叶轮设计提供依据,确保叶轮运行的安全性,对于研发具有我国自主知识产权的重大工业装备具有重要的理论意义和工程实用价值。本文对旋转叶轮的力学特性进行了深入的研究,包括如下两个方面:(1)综合考虑计算精度、规模和效率,采用自适应有限元方法,对离心压缩机叶轮原始模型与修正模型进行了精细的弹塑性分析。在此基础上,数值模拟了超速预加载工艺过程,分析了超速预加载工艺过程中叶轮的von Mises应力和等效塑性应变的演化历程,通过与无超速预加载历史叶轮在正常工作下的应力水平做对比,揭示了超速预加载工艺的力学机理。分析了叶轮关键部位应力对有限元网格的敏感性问题,介绍了如何得到对网格不敏感的结构热点应力及相应的强度判别准则,进而正确使用有限元计算结果估计叶轮疲劳寿命。(2)提出了将叶轮加载至发生塑性变形再卸载形成的残余应力作为自平衡应力场的方法。根据极限分析与安定分析的两个下限定理,建立了求解极限荷载和安定荷载的数学规划,并进行求解。通过对简单结构进行安定分析验证了方法的正确性。最后,对复杂的叶轮结构进行了安定性分析,得到了叶轮工作时的安定条件。利用数学规划列式,我们还进一步证明了,如果对于结构的所有点,弹性包络都是在荷载乘子取最大(最小)值时达到,则结构的极限荷载和安定荷载相等。更多还原

【Abstract】 Rotating bladed-disk are the core rotating component of the centrifugal compressors.Its structure and work condition are both complicated and its work status directly affects the safety of the whole compressor unit.With the advance of the design parameters for compressor,the work condition and static character of the rotating bladed-disk become more critical.A detailed and reliable strength analysis provides designers a solid foundation, ensures the safety of compressor operation and is of great significance of theory and engineering value for design and production of important industrial equipment with self-owned intellectual property right.The present paper studies several important mechanical performances of the rotating bladed-disk as follows:(1) Making a comprehensive consideration of the computational accuracy,model size and efficiency,we apply the adaptive finite element method to carry out refined static elastic-plastic strength analysis for the rotating bladed-disk.The over-speed preloading techniques process is simulated;the evolution of von Mises stress and equivalent plastic strain with time is studied.The contrast of stress levels between the over-speed preloading disk and the no over-speed preloading disk in normal working condition reveals the mechanism of the over-speed preloading techniques.The concept of structural hot spot stress is introduced which is not sensitive to the mesh-size,and the method how to get the structural hot spot stress is discussed.With the comprehension of these problems,we can use the result of the finite element calculation to predict its fatigue life.(2) The residual stress obtained by loading the rotating bladed-disk into plastic deformation and unloading is proposed as the self-equilibrium stress basis.Based on the lower-bound theorem of limit analysis and lower-bound theorem of shakedown analysis,we developed the mathematical formulation of limit load and shakedown load,and solved with mathematical programming.The shakedown analyses of two simple structures are studied to verify the correctness of our method.The shakedown analysis of rotating bladed-disk is carried out.On the basis of mathematical programming formulation,we further prove that safety load factor and shakedown load factor is equal if the elastic envelop for every point in the structure is simultaneously attained at the maximum(or minimum) load factors.更多还原