轴系与汽轮发电机基础的联合动力分析
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摘要
通过自身的工程实践和国内外经验的借鉴,以"轴系与基础联合动力分析"和"汽轮发电机基础动力优化设计"两个前沿课题为主线,从空间杆系计算模型的准确性、合理性上展开论述,重点突出了轴系对汽轮发电机基础动力特性的影响.为了准确且合理地建立汽轮发电机基础联合动力分析计算模型,对不同计算模型的处理方法进行了分析和评价,指出了常规计算模型存在的不足和主观因素;以转子动力学为基础,对原始Jeffcott转子作了较为完整的动力分析和推广,得出了任意残余不平衡量分布以及内阻尼、介质阻尼作用下变直径转子的梁单元数学模型,为联合模型的线性有限元分析奠定了理论基础;在计算模型中采用了材料阻尼,选择了线性油膜力模型来模拟油膜的刚度;引入了梁局部刚度的概念,推导了梁局部刚度的解析表达式,提出了油膜刚度、轴承刚度和基础梁局部刚度的刚度串联模式;将常规的基础有限元模型与转子梁单元、轴承-油膜-基础梁等效连接单元合并,获得了总的空间杆系的线性有限元计算模型.以一单机容量为1 000 MW的火力发电厂汽轮发电机基础的动力分析为例,通过不同计算模型振动线位移分析结果的比较,揭示了临界转速、残余不平衡量的分布对汽轮发电机基础动力特性的影响,充分体现了轴系在汽轮发电机基础动力分析中的重要作用.
According to the engineering practice and the references of foreign & domestic experiences,based on two foreland subjects,"associated dynamic analysis of shafting and turbo-generator foundation(TGF)" and "dynamic optimum design of TGF",discussions focused on accuracy and rationality of spatial beam calculation model are proceeding,the important influence on TGF dynamic properties of shafting is emphasized.To set up the associated dynamic model of shafting and TGF with more accuracy;different modeling methods are discussed and evaluated;objective factors of general TGF model are pointed out;original Jeffcott rotor model is analyzed and extended based on rotor dynamics,under the action of ambient damping and internal damping,the beam element mathematical model of arbitrary residual unbalance distribution are acquired,which is the basic theory of the following finite element analysis;material damping is adopted in the model to simulate the stiffness of oil film;concept of beam local stiffness is introduced;analytical expressions are derived;a compound stiffness model of beam local stiffness,bearing stiffness and oil film stiffness is proposed;general TGF finite element model,rotor beam element and the compound link element of bearing,oil film and beam are merged;integral spatial beam finite element linear model is acquired;beam elements with concentrated mass are adopted to simulate the mass and stiffness behavior of turbine & generator rotors.Finally,a 1000 MW thermal power plant TGF is used for case study,vibration linear displacements of different models are compared with each other;it is shown that the influence of critical rotation speed and distribution of residual unbalance on TGF dynamic properties,sufficiently shows the important function of shafting in TGF dynamic analysis.
According to the engineering practice and the references of foreign & domestic experiences,based on two foreland subjects,"associated dynamic analysis of shafting and turbo-generator foundation(TGF)" and "dynamic optimum design of TGF",discussions focused on accuracy and rationality of spatial beam calculation model are proceeding,the important influence on TGF dynamic properties of shafting is emphasized.To set up the associated dynamic model of shafting and TGF with more accuracy;different modeling methods are discussed and evaluated;objective factors of general TGF model are pointed out;original Jeffcott rotor model is analyzed and extended based on rotor dynamics,under the action of ambient damping and internal damping,the beam element mathematical model of arbitrary residual unbalance distribution are acquired,which is the basic theory of the following finite element analysis;material damping is adopted in the model to simulate the stiffness of oil film;concept of beam local stiffness is introduced;analytical expressions are derived;a compound stiffness model of beam local stiffness,bearing stiffness and oil film stiffness is proposed;general TGF finite element model,rotor beam element and the compound link element of bearing,oil film and beam are merged;integral spatial beam finite element linear model is acquired;beam elements with concentrated mass are adopted to simulate the mass and stiffness behavior of turbine & generator rotors.Finally,a 1000 MW thermal power plant TGF is used for case study,vibration linear displacements of different models are compared with each other;it is shown that the influence of critical rotation speed and distribution of residual unbalance on TGF dynamic properties,sufficiently shows the important function of shafting in TGF dynamic analysis.
引文
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[4]GB 50040-96,动力机器基础设计规范[S].北京:中国计划出版社,1997.
[5]梁超锋,欧进萍.结构阻尼与材料阻尼的关系[J].地震工程与工程振动,2006,26(1):49-55.
[6]张策.机械动力学[M].第二版.北京:高等教育出版社,2008.
[7]孟光.转子动力学研究的回顾与展望[J].振动工程学报,2002,15(1):1-9.
[8]顾家柳,丁奎元,刘启洲,等.转子动力学[M].北京:国防工业出版社,1985.
[9]李录平,卢绪祥.汽轮发电机组振动与处理[M].北京:中国电力出版社,2007.
[10]龙驭球,包世华.结构力学下册[M].第二版.北京:高等教育出版社,1996.
[11]杨建刚,等.汽轮机轴承动力特性三维流固耦合分析模型[J].中国电机工程学报.2004,24(8):147-151.
[12]罗国澍.汽机基础的结构分析与设计~关于我国现行的空间多自由度法[J].电力建设,1983,(1):54-63.
[13]顾晃.汽轮发电机组的振动与平衡[M].北京:水利电力出版社,1989.
[14]张艾萍,等.汽轮机组振动幅值与轴承载荷及油膜刚度之间的关系[J].汽轮机技术,2002,44(2):80-81.
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