超临界600MW汽轮机低压缸装配误差分析
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摘要
在目前的国内电力市场上,超临界600MW汽轮机作为一种主力机型,占有很大的市场份额。该产品低压外缸体组装后,直径约为7m,而壁体较薄,约为32mm,属于典型的大型薄壁零件。这类零件体积大、总体刚性较差,在加工、装配过程中缸体极易在装夹力及装配面的相互作用下产生变形,使得缸体装配面出现接触不良,配合面间隙超差等情况,影响机组装配质量。基于经验的、定性的分析而采取的工艺补偿措施,不可避免地需要对汽轮机进行多次重复组装调整,甚至需要关键部件的回机床返修,由此造成产品制造周期长,制造成本居高不下。此外,装配误差对汽轮机性能的影响缺乏系统的分析,特别是装配误差如何影响通流间隙及低压缸下半裙座与基础台板的接触等问题亟待解决,因此,本文的工作对于确保汽轮机达到设计标准具有重要的理论与实用意义。
大量的实践表明,汽轮机低压缸装配误差最终均表现为低压外缸上半各爿缸体垂直结合面斜张口形误差。本文基于有限元分析针对超临界600MW汽轮机低压缸这一装配误差对汽轮机性能的影响进行了研究。首先建立了低压缸各主要零部件三维UG模型及有限元分析模型。然后以螺栓拉紧力作为外力消除装配误差,研究在不同装配误差下,该外力对螺栓强度、低压外缸产生的变形及其对低压缸通流动静间隙、低压缸下半裙座与基础台板接触情况的影响。本文结合企业生产实际情况,选取了具有代表意义的多个斜张口误差数据,分析了装配误差对低压缸通流动静间隙的变化趋势,以及对低压缸下半裙座与基础台板接触情况影响范围,并对低压缸上半缸体垂直结合面连接螺栓强度进行了分析。研究表明:随着装配误差的增大,拼缸处螺栓的最大应力、低压外缸的变形量、裙座四周的变形量及外缸上爿进汽口法兰面沿重力方向的变形量均随之增大。而装配误差的大小对外缸与内缸接触面的变形量影响很小,因此对通流间隙影响不大。
本文获得了大量的、全面的理论数据,对于指导实际生产具有重要价值。此外本文提出的基于斜张口误差分析方法可以推广到其它类型的汽轮机装配过程中。
As an important power equipment, the supercritical 600MW steam turbine occupies the main market share of the power industry now in China. The diameter of the low pressure (LP) outer cylinder of this turbine is 7000mm approximately. But the thickness of the LP outer cylinder wall is only 32mm. As mentioned above, the LP outer cylinder belongs to typical big thin-wall part. This kind of parts, due to their large volume and low rigidity, are apt to deformation under the force of fixture and the effect of assembly surface during machining and assembling processes. And the quality of the turbine will also be affected by the anormaly of contact among those assembled surfaces. According to the normal technical method based on the experience and qualitative analysis, the turbine must be adjusted and assembled repeatedly, and in some cases even its main part should be machined again. Thus the manufacturing period of the turbine becomes longer and the manufacturing cost is higher. Moreover, there is short of systemic study on the effect of assembly deviation on the steam turbine performance. And the effect on the flow gap and on the LP outer cylinder base contacting surface caused by assembly deviation should be analysed in great need in industry. Therefore, the study of this thesis is of great significance from both academic and practical perspectives for making qualified turbines according to the design standards.
As proven by a lot of industrial practices, the assembly deviation of LP cylinder of steam turbine occurs finally on the vertical joint surfaces of LP upper outer cylinder in a form of wedging gap. Based on the finite element analysis method, in this thesis the effect on the turbine performance caused by the assembly deviation of supercritical 600MW steam turbine LP cylinder will be studied. The 3D UG models and finite element analysis models of main parts of LP cylinder are finished at first. And then the assembly deviation should be eliminated by the tighting force of screw bolts. Under this condition and based on the different assembly deviation values, the effect on the screw bolt intensity, the deformation of LP outer cylinder, the flow gap of LP cylinder, the contacting between the LP outer cylinder and base bedplates will be explored. According to the practice of the enterprise, several representative wedgeing gap values are selected and used for studying the alteration trend of LP cylinder flow gap, the affected range on LP outer cylinder base supporting surface and the strength of screw bolt on the LP outer upper cylinder vertical joint surfaces. It is shown with the FEA analysis that the maximum stress of screw bolt, the deformation of LP outer cylinder, the deformation of LP outer cylinder base supporting surface and the vertical deformation of the inlet opening of LP outer upper cylinder increase with the increasing of assembly deviation. But the deformation altering of the contacting surfaces between the LP outer cylinder and LP inner cylinder is very small based on different assembly deviation. Therefore, the LP cylinder flow gap is hardly affected by assembly deviation.
The plentiful and comprehensive technical data obtained in the thesis is very useful and valuable for instructing the production. And the analysing method based on wedging gap deviation suggested in this thesis can be extended and applied in the assembly process of other kinds of steam turbines.
大量的实践表明,汽轮机低压缸装配误差最终均表现为低压外缸上半各爿缸体垂直结合面斜张口形误差。本文基于有限元分析针对超临界600MW汽轮机低压缸这一装配误差对汽轮机性能的影响进行了研究。首先建立了低压缸各主要零部件三维UG模型及有限元分析模型。然后以螺栓拉紧力作为外力消除装配误差,研究在不同装配误差下,该外力对螺栓强度、低压外缸产生的变形及其对低压缸通流动静间隙、低压缸下半裙座与基础台板接触情况的影响。本文结合企业生产实际情况,选取了具有代表意义的多个斜张口误差数据,分析了装配误差对低压缸通流动静间隙的变化趋势,以及对低压缸下半裙座与基础台板接触情况影响范围,并对低压缸上半缸体垂直结合面连接螺栓强度进行了分析。研究表明:随着装配误差的增大,拼缸处螺栓的最大应力、低压外缸的变形量、裙座四周的变形量及外缸上爿进汽口法兰面沿重力方向的变形量均随之增大。而装配误差的大小对外缸与内缸接触面的变形量影响很小,因此对通流间隙影响不大。
本文获得了大量的、全面的理论数据,对于指导实际生产具有重要价值。此外本文提出的基于斜张口误差分析方法可以推广到其它类型的汽轮机装配过程中。
As an important power equipment, the supercritical 600MW steam turbine occupies the main market share of the power industry now in China. The diameter of the low pressure (LP) outer cylinder of this turbine is 7000mm approximately. But the thickness of the LP outer cylinder wall is only 32mm. As mentioned above, the LP outer cylinder belongs to typical big thin-wall part. This kind of parts, due to their large volume and low rigidity, are apt to deformation under the force of fixture and the effect of assembly surface during machining and assembling processes. And the quality of the turbine will also be affected by the anormaly of contact among those assembled surfaces. According to the normal technical method based on the experience and qualitative analysis, the turbine must be adjusted and assembled repeatedly, and in some cases even its main part should be machined again. Thus the manufacturing period of the turbine becomes longer and the manufacturing cost is higher. Moreover, there is short of systemic study on the effect of assembly deviation on the steam turbine performance. And the effect on the flow gap and on the LP outer cylinder base contacting surface caused by assembly deviation should be analysed in great need in industry. Therefore, the study of this thesis is of great significance from both academic and practical perspectives for making qualified turbines according to the design standards.
As proven by a lot of industrial practices, the assembly deviation of LP cylinder of steam turbine occurs finally on the vertical joint surfaces of LP upper outer cylinder in a form of wedging gap. Based on the finite element analysis method, in this thesis the effect on the turbine performance caused by the assembly deviation of supercritical 600MW steam turbine LP cylinder will be studied. The 3D UG models and finite element analysis models of main parts of LP cylinder are finished at first. And then the assembly deviation should be eliminated by the tighting force of screw bolts. Under this condition and based on the different assembly deviation values, the effect on the screw bolt intensity, the deformation of LP outer cylinder, the flow gap of LP cylinder, the contacting between the LP outer cylinder and base bedplates will be explored. According to the practice of the enterprise, several representative wedgeing gap values are selected and used for studying the alteration trend of LP cylinder flow gap, the affected range on LP outer cylinder base supporting surface and the strength of screw bolt on the LP outer upper cylinder vertical joint surfaces. It is shown with the FEA analysis that the maximum stress of screw bolt, the deformation of LP outer cylinder, the deformation of LP outer cylinder base supporting surface and the vertical deformation of the inlet opening of LP outer upper cylinder increase with the increasing of assembly deviation. But the deformation altering of the contacting surfaces between the LP outer cylinder and LP inner cylinder is very small based on different assembly deviation. Therefore, the LP cylinder flow gap is hardly affected by assembly deviation.
The plentiful and comprehensive technical data obtained in the thesis is very useful and valuable for instructing the production. And the analysing method based on wedging gap deviation suggested in this thesis can be extended and applied in the assembly process of other kinds of steam turbines.
引文
[1] Sanderson A C. Assemblability Based on Maximum Likelihood Configration of Tolerance. Presented at IEEE Symposium on Assembly and Task Planning. Marinadel Ray. CA.1997.
[2]罗振璧,汪劲松,杨世明等.制造过程质量控制中误差流理论的研究[J].机械工程学报,1995,31(4):62~69.
[3]张发平,孙厚芳,袁光明,陈光明.工-夹系统刚度计算及变形加工误差模型[J].北京理工大学学报,2004,24(12):1042~1047.
[4]赵家黎,郭伟,于鸿彬.制造过程中误差传播问题研究的进展分析[J].中国机械工程,2006,17(8):445~450.
[5]彭红梅.薄壁件装配公差的计算与分析[D][硕士学位论文].天津:河北工业大学,2004.
[6] Assembly-oriented Design A Top-down Approach to Modeling Assemblies:[Ph.D.disscrtation]. Cambridge, Mass.:Mass.Inst. Technol,1997.
[7] Mantripragada R, Whitney D E. Modeling and Controlling Variation in Mechanical Assemblies using State Transition Models. IEEE International Conference on Robotics & Automation, Luven, Belgium.1998.
[8] Mantripragada R, Whitney D E. Modeling and Controlling Variation Propagation in Mechnical Assemblies using State Transition Models. IEEE Transactions on Robotics and Automation, 1999,15(1):124~140.
[9] MENASSA R J,DEVRIES W R. Opimization methods applied to selecting support positions in fixture design[J]. Transactions of the ASME Journal of Engineering for Industry,1991,113:412-418.
[10] Y.J. Liao, S.J. Hu, D.A. Stephenson,.Fixture layout optimization considering workpiece–fixture contact interaction: simulation results, Transactions of the NAMRI of SME XXVI (1998) 341~346.
[11]万志坚,基于Pro/Engineer建模的装配仿真研究,汽车工艺与材料,2008年第2期.
[12]梅泽高,俞涛,王栋,朱文华,虚拟装配仿真系统相关技术的研究,计算机仿真,2007年11月,第24卷第11期.
[13]周志革,黄文振,薄壁件的装配误差诊断与控制综述,汽车工程,2000年,第22卷,第1期.
[14]郑轶,宁汝新,刘检华,杜龙.虚拟装配关键技术及其发展[J].系统仿真学报2006.33.
[15]周志革,武一民,彭红梅崔根群.柔性薄壁件装配公差的分析[J].机械设计与制造,2005,8(8):37~39.
[16]李永立,张树有,刘振宇.VRML环境下基于语义的产品装配设计技术研究[J].计算机辅助设计与图形学学报,2003.2
[17] S.Jayaram,H.Connacher,K.Lyons.Virtual Assembly UsingVirtual-Reality Techniques[J].Computer Aided Design(S0010-4485),1997,8(29):575-584.
[18] Bourjault A,Lbole A.Modeling an Assembly Process[C]//IEEE International Conference on Automation of Manufacturing Industry. California:IEEE,1986.183-198.
[19] T.L.De Fazio, D.Whitney. Simplified Generation of All Mechanical Assembly Sequences[J].IEEE Transaction on Robotics and Automation (S1042-296X), 1987,3(6):640-658.
[20]鲁建霞,苟惠芳,有限元法的基本思想与发展过程,机械管理开发,2009年4月,第24卷,第2期.
[21] G.Swoboda,杜庆华,接触摩擦单元的理论及其应用,岩土工程学报,1994年5月,第16卷,第3期.
[22]刘天祥,刘更,伽辽金-有限元耦合方法,西北工业大学学报,2003年8月,第21卷,第4期.
[23]董玉文,任青文,苏琴,接触摩擦问题的扩展有限元数值模拟方法,长江科学院院报,2009年5月,第26卷第5期.
[24] Fredriksson B. Finite element solution of surface nonlinearities in structural mechanics with special emphasis to contact and fracture mechanics problems. Computers & Structures. 1976,6:281~290.
[25] Tsuta T,Yamaji S. Finite element analysis of contact problem.Theory and Practice in Finite Element Structure Analysis, Japan: University of Tokyo Press,1973.
[26] Campos L T, Oden J T, Kikuchi N, A numerical analysis of a class of contact problems with friction in elastostatics. Computer Meth Appl Mech and Engng, 1982,34:261~268.
[27] P Wriggers G Z. Applieation of Augemented Lagrangian Teehniques for Nonlinear constitutive Laws in contact Interfaee [J]. Cnunou.Number Meth.Eng,1993,(3):286~298.
[28] J H Heegaard A C. An Augemented Lagrangian Method for disereet Large- slip contact problem [J].Int J. Number Meth eng,1993,(3):146~155.
[29] J C Simo T A L. An Augemented Lagrangian treatment of contact problem Involving Friction [J]. Int Computer & strueture,1992,(42):12~ 20.
[2]罗振璧,汪劲松,杨世明等.制造过程质量控制中误差流理论的研究[J].机械工程学报,1995,31(4):62~69.
[3]张发平,孙厚芳,袁光明,陈光明.工-夹系统刚度计算及变形加工误差模型[J].北京理工大学学报,2004,24(12):1042~1047.
[4]赵家黎,郭伟,于鸿彬.制造过程中误差传播问题研究的进展分析[J].中国机械工程,2006,17(8):445~450.
[5]彭红梅.薄壁件装配公差的计算与分析[D][硕士学位论文].天津:河北工业大学,2004.
[6] Assembly-oriented Design A Top-down Approach to Modeling Assemblies:[Ph.D.disscrtation]. Cambridge, Mass.:Mass.Inst. Technol,1997.
[7] Mantripragada R, Whitney D E. Modeling and Controlling Variation in Mechanical Assemblies using State Transition Models. IEEE International Conference on Robotics & Automation, Luven, Belgium.1998.
[8] Mantripragada R, Whitney D E. Modeling and Controlling Variation Propagation in Mechnical Assemblies using State Transition Models. IEEE Transactions on Robotics and Automation, 1999,15(1):124~140.
[9] MENASSA R J,DEVRIES W R. Opimization methods applied to selecting support positions in fixture design[J]. Transactions of the ASME Journal of Engineering for Industry,1991,113:412-418.
[10] Y.J. Liao, S.J. Hu, D.A. Stephenson,.Fixture layout optimization considering workpiece–fixture contact interaction: simulation results, Transactions of the NAMRI of SME XXVI (1998) 341~346.
[11]万志坚,基于Pro/Engineer建模的装配仿真研究,汽车工艺与材料,2008年第2期.
[12]梅泽高,俞涛,王栋,朱文华,虚拟装配仿真系统相关技术的研究,计算机仿真,2007年11月,第24卷第11期.
[13]周志革,黄文振,薄壁件的装配误差诊断与控制综述,汽车工程,2000年,第22卷,第1期.
[14]郑轶,宁汝新,刘检华,杜龙.虚拟装配关键技术及其发展[J].系统仿真学报2006.33.
[15]周志革,武一民,彭红梅崔根群.柔性薄壁件装配公差的分析[J].机械设计与制造,2005,8(8):37~39.
[16]李永立,张树有,刘振宇.VRML环境下基于语义的产品装配设计技术研究[J].计算机辅助设计与图形学学报,2003.2
[17] S.Jayaram,H.Connacher,K.Lyons.Virtual Assembly UsingVirtual-Reality Techniques[J].Computer Aided Design(S0010-4485),1997,8(29):575-584.
[18] Bourjault A,Lbole A.Modeling an Assembly Process[C]//IEEE International Conference on Automation of Manufacturing Industry. California:IEEE,1986.183-198.
[19] T.L.De Fazio, D.Whitney. Simplified Generation of All Mechanical Assembly Sequences[J].IEEE Transaction on Robotics and Automation (S1042-296X), 1987,3(6):640-658.
[20]鲁建霞,苟惠芳,有限元法的基本思想与发展过程,机械管理开发,2009年4月,第24卷,第2期.
[21] G.Swoboda,杜庆华,接触摩擦单元的理论及其应用,岩土工程学报,1994年5月,第16卷,第3期.
[22]刘天祥,刘更,伽辽金-有限元耦合方法,西北工业大学学报,2003年8月,第21卷,第4期.
[23]董玉文,任青文,苏琴,接触摩擦问题的扩展有限元数值模拟方法,长江科学院院报,2009年5月,第26卷第5期.
[24] Fredriksson B. Finite element solution of surface nonlinearities in structural mechanics with special emphasis to contact and fracture mechanics problems. Computers & Structures. 1976,6:281~290.
[25] Tsuta T,Yamaji S. Finite element analysis of contact problem.Theory and Practice in Finite Element Structure Analysis, Japan: University of Tokyo Press,1973.
[26] Campos L T, Oden J T, Kikuchi N, A numerical analysis of a class of contact problems with friction in elastostatics. Computer Meth Appl Mech and Engng, 1982,34:261~268.
[27] P Wriggers G Z. Applieation of Augemented Lagrangian Teehniques for Nonlinear constitutive Laws in contact Interfaee [J]. Cnunou.Number Meth.Eng,1993,(3):286~298.
[28] J H Heegaard A C. An Augemented Lagrangian Method for disereet Large- slip contact problem [J].Int J. Number Meth eng,1993,(3):146~155.
[29] J C Simo T A L. An Augemented Lagrangian treatment of contact problem Involving Friction [J]. Int Computer & strueture,1992,(42):12~ 20.