轴流式压缩机叶片静动态特性分析
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摘要
叶片是压缩机的关键部件之一,其结构设计的合理与否直接影响到整机的性能,而叶片性能的优劣主要体现在其静、动态等特性上。本文以一企业设计的某型号轴流式压缩机叶片为研究对象,采用有限元分析与实验测试相结合的方法,对该叶片的强度、固有频率和振型进行了研究。
首先针对叶片结构的高度扭曲性,以及采用常规建模方法不能很好将CAD模型转化为CAE分析模型的问题,提出将叶片各截面型线分成多段,以建立带多条边界曲线的实体模型。采用参数化设计软件SolidWorks建立了叶片的三维实体模型,并通过数据接口将其CAD实体模型精确转换为ANSYS环境下的CAE分析模型。
在成功建立叶片有限元分析模型的基础上,采用ANSYS软件分别计算了不同工作载荷、不同约束情况下叶片的静态特性,得到其应力与变形的分布规律。研究结果表明叶片的高应力主要由离心力产生,高应力区主要集中在叶根榫槽处,而气流力则主要引起叶片的大变形,出现在叶顶部位。将叶根约束部位力的作用点内移,能有效改善实际运行中叶根榫槽边缘经常出现裂纹的情况。
考虑到叶片动态特性研究的必要性,又对此类型叶片进行了固有频率、振型等特性的计算。前4阶振型依次表现为1阶弯曲、2阶弯曲、1阶扭转和弯扭联合。由计算得到的动频值绘制出了Campbell图,分析发现叶片在工作转速下存在两个共振点,必须对其进行调频。约束类型无论对其静频值还是动频值都影响不大。
最后采用频谱分析法测量了一级叶片的静频,实验测试值与数值计算值吻合良好,验证了有限元计算的准确性。此外,从测试的同一级叶片静频值来看,少部分叶片分散度超出标准,因此应提高加工精度和测频修频的准确性。
As one of the key parts of compressors, the blades play an important role in the working performance of the compressor, especially its' structural design rationality. While the static and dynamic characteristics are the main aspects in evaluating the performance of blades. In this thesis, one type of blade designed by an enterprise manufacturing the axial-flow compressors is used as the research object, and its characteristics in strength, natural frequency and mode shape are studied by combining the finite element analysis method and experiments method.
First, considering the high skewness of blades and the problem of converting the CAD model into CAE model freely by general modeling methods, a new method is put forward for blade's solid model with more than one boundary curves by dividing the cross-sections of the blade into 4 parts. SolidWorks, a parametric software, is used to build up the three-dimensional CAD model and then the model for CAE analysis in the environment of ANSYS is obtained by converting from CAD model by virtue of the data interface.
On the basis of successful establishing of the finite element model, the static characteristics of the blade subjected different loads and constraint conditions are analyzed by ANSYS software, and the distribution of stress and displacement are obtained. The results show that the high stress of the blade is mainly caused by centrifugal force, which primarily occurs on tenon-grooves of blade roots, while airflow pressure is more dominant factor affecting the deformation value of blades, deformation always reaches to the maximum on the top of blades. In addition, the crack phenomenon on the tenon-grooves of blade roots can be avoided to some extent if the forced location is ordered to offset the boundaries.
Considering the research necessity of dynamic characteristics of blades, the natural frequency and mode shape are also calculated. The first 4 modes are shown as one bending mode、two bending mode、one twisting mode and bending-torsion . Then the Campbell diagram is drawn based on the dynamic frequency values, where two resonance points exist in the normal working conditions. It is necessary to carry out the frequency modulation. Constraint conditions have little effect on the static or dynamic frequency.
Spectrum analysis is adopted to measure the natural frequency of the first stage blades and the numerical results are reasonably consistent with the experimental test, which shows the veracity of finite element analysis. In addition, the dispersities of a few blades are out of standard in from the tested natural frequency values of blades. So it is necessary to improve the accuracy of machining and the frequency of measurement and repairment.
首先针对叶片结构的高度扭曲性,以及采用常规建模方法不能很好将CAD模型转化为CAE分析模型的问题,提出将叶片各截面型线分成多段,以建立带多条边界曲线的实体模型。采用参数化设计软件SolidWorks建立了叶片的三维实体模型,并通过数据接口将其CAD实体模型精确转换为ANSYS环境下的CAE分析模型。
在成功建立叶片有限元分析模型的基础上,采用ANSYS软件分别计算了不同工作载荷、不同约束情况下叶片的静态特性,得到其应力与变形的分布规律。研究结果表明叶片的高应力主要由离心力产生,高应力区主要集中在叶根榫槽处,而气流力则主要引起叶片的大变形,出现在叶顶部位。将叶根约束部位力的作用点内移,能有效改善实际运行中叶根榫槽边缘经常出现裂纹的情况。
考虑到叶片动态特性研究的必要性,又对此类型叶片进行了固有频率、振型等特性的计算。前4阶振型依次表现为1阶弯曲、2阶弯曲、1阶扭转和弯扭联合。由计算得到的动频值绘制出了Campbell图,分析发现叶片在工作转速下存在两个共振点,必须对其进行调频。约束类型无论对其静频值还是动频值都影响不大。
最后采用频谱分析法测量了一级叶片的静频,实验测试值与数值计算值吻合良好,验证了有限元计算的准确性。此外,从测试的同一级叶片静频值来看,少部分叶片分散度超出标准,因此应提高加工精度和测频修频的准确性。
As one of the key parts of compressors, the blades play an important role in the working performance of the compressor, especially its' structural design rationality. While the static and dynamic characteristics are the main aspects in evaluating the performance of blades. In this thesis, one type of blade designed by an enterprise manufacturing the axial-flow compressors is used as the research object, and its characteristics in strength, natural frequency and mode shape are studied by combining the finite element analysis method and experiments method.
First, considering the high skewness of blades and the problem of converting the CAD model into CAE model freely by general modeling methods, a new method is put forward for blade's solid model with more than one boundary curves by dividing the cross-sections of the blade into 4 parts. SolidWorks, a parametric software, is used to build up the three-dimensional CAD model and then the model for CAE analysis in the environment of ANSYS is obtained by converting from CAD model by virtue of the data interface.
On the basis of successful establishing of the finite element model, the static characteristics of the blade subjected different loads and constraint conditions are analyzed by ANSYS software, and the distribution of stress and displacement are obtained. The results show that the high stress of the blade is mainly caused by centrifugal force, which primarily occurs on tenon-grooves of blade roots, while airflow pressure is more dominant factor affecting the deformation value of blades, deformation always reaches to the maximum on the top of blades. In addition, the crack phenomenon on the tenon-grooves of blade roots can be avoided to some extent if the forced location is ordered to offset the boundaries.
Considering the research necessity of dynamic characteristics of blades, the natural frequency and mode shape are also calculated. The first 4 modes are shown as one bending mode、two bending mode、one twisting mode and bending-torsion . Then the Campbell diagram is drawn based on the dynamic frequency values, where two resonance points exist in the normal working conditions. It is necessary to carry out the frequency modulation. Constraint conditions have little effect on the static or dynamic frequency.
Spectrum analysis is adopted to measure the natural frequency of the first stage blades and the numerical results are reasonably consistent with the experimental test, which shows the veracity of finite element analysis. In addition, the dispersities of a few blades are out of standard in from the tested natural frequency values of blades. So it is necessary to improve the accuracy of machining and the frequency of measurement and repairment.
引文
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[29]沈火明,唐伟.空压机转子的动力特性及其叶片根部强度分析[J].西南交通大学学报,2001,36(6):637-640.
[30]陈国强.轴流式水轮机叶片刚度和强度有限元分析[J].机械强度,2003,25(6):690-693.
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[2]谢进祥.轴流压缩机首级叶片疲劳断裂的原因分析[J].风机技术,2007,(2):64-70.
[3]万家宏.轴流-离心复合式压缩机叶片断裂原因分析[J].风机技术,2000,(6):53-55.
[4]齐文.空压机叶片断裂事故的解决[J].风机与压缩机,2004,(5):64-66.
[5]戴义平,等.轴流式压缩机叶片断裂原因分析及改型设计[J].化工机械,2006,33(1):14-19.
[6]谭奇峰.东深供水轴流泵叶片裂纹原因分析及处理[J].中国农村水利水电,2002,(6):50-51.
[7]胡宝玉,张利新,钟光华.小浪底转轮叶片裂纹产生原因分析及处理措施[J].中国水利,2004,(4):41-43.
[8]沈阳水泵研究所.叶片泵设计手册[M].北京:机械工业出版社,1983.
[9]Lucian J,Dorel H.Numerical analysis of the inviscid incompressible flow in two-dimensional radial-flow pump impellers[J].Engineering Analysis with Boundary Elements,1998,22(4):271-279.
[10]Vyas NS,Sidharth RJS.Dynamic stress analysis and a fracture mechanics approach to life prediction of turbine blades[J].Mechanism and Machine theory,1997,32(4):511-527.
[11]Prakash,Pandey RK.Failure analysis of the impellers of a feed pump[J].Engineer Failure Analysis,1996,3(1):45-52.
[12]关醒凡,姚兆生.泵零件强度计算[M].北京:机械工业出版社,1981.
[13]杨朝刚.离心通风机叶轮强度的二次计算法及应用[J].风机技术,1997,(1):5-10.
[14]李方泽,王正.工程振动测试与分析[M].北京:高等教育出版社,1992:178-185.
[15]陈锦明,王仲博.国内外汽轮机叶片振动监测技术发展综述[J].热力发电,1997,(3):53-57.
[16]魏先英,余耀.905mm叶片的动振动试验[J].汽轮机技术,1994,36(1):57-60.
[17]倪振华,谢壮宁,章应忠.拱形围带叶片组振动特性分析及实验研究[J].应用力学学报,1999,16(4):94-97.
[18]杨秉玉,刘启洲.喘振状态下叶片振动响应的试验研究[J].燃气涡轮试验与研究,2002,15(2):31-35.
[19]徐自力,谢浩.成组叶片振动特性的三维数值模拟及实验研究[J].西安交通大学学报,2003,37(7):678-682.
[20]黄俊清.国产300MW汽轮机叶片故障的试验研究[J].广东电力,2003,16(3):17-20.
[21]钱勤.李家峡1号机组转轮叶片动应力试验及机理分析[J].水力发电学报,2006,25(4):131-134.
[22]陶文铨.数值传热学[M].西安:西安交通大学出版社,2002.
[23]Kirkhope J,Wilson GJ.Analysis of coupled bladed disc vibration in Axial flow Turbine and Fans[C].AIAA/ASME 12th Structural Dynamics and Material Coference,1971,71-75.
[24]朱宝田,吴厚钰.用完整空间扭曲梁有限元法分析汽轮机叶片的力学特性[J].西安交通大学 学报,1998,(3):52-55.
[25]Leissa AW,Lee JK,Wang AJ.Rotating Blade Vibration Analysisi Using Shells[J].ASME Journal of Engineedng for Power,1982,104:296-302.
[26]龙卫国,金波.离心式压缩机叶轮叶片应力有限元分析[J].南华大学学报(理工版),2001,(4):44-49.
[27]谢永慧,王乐天,安宁,等.汽轮机叶片振动特性的三维有限元分析[J].机械强度,1997,19(4):1-5.
[28]谢永慧,王乐天,袁奇,等.汽轮机叶片静态和动态应力的三维有限元分析[J].应用力学学报,1999,16(3):89-93.
[29]沈火明,唐伟.空压机转子的动力特性及其叶片根部强度分析[J].西南交通大学学报,2001,36(6):637-640.
[30]陈国强.轴流式水轮机叶片刚度和强度有限元分析[J].机械强度,2003,25(6):690-693.
[31]郑兴海,张克危.水利机械叶片强度有限元分析[J].水泵技术,2004,(6):19-22.
[32]魏鹏飞,吴建军,陈启智.液体火箭发动机涡轮叶片结构特性的有限元分析[J].国防科技大学学报,2005,27(2):29-31.
[33]陈精一.电脑辅助工程分析ANSYS使用指南[M].北京:中国铁道出版社,2001.
[34]龚曙光.ANSYS基础应用及范例解析[M].北京:机械工业出版社,2003.
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