薄膜蒸发器筒节整体夹套封口环 应力分析及其改进设计

1、薄膜蒸发器筒节整体夹套封口环应力分析及其改进设计刘友宏(清华大学胡国霖(中石化有限公司金陵分公司设计院摘要根据对流传热数值模拟结果, 算模型, 载荷时, 结构是安全的; 当考虑温度载荷时, 构设计和相应的强度计算, 关键词薄膜蒸发器, 较多的工作。夹套结构, 因为夹套内流体压力引起的封口环处的弯曲应力很小, 前人研究较少。本文研究的多台按规范设计的 18m 2薄膜蒸发器在使用5个月后仍然发生了容器最上面一段筒节的夹套封口环与筒体连接的焊缝热影响区大面积穿透裂纹。在排除了其他一些可能因素后, 笔者认为在夹套类传热结构设计中, 当容器筒体两侧介质温度差较大时, 还需考虑流固耦合作用, 进行包括固体

2、壁面在内的流体力学、传热学计算。然后利用固体力学进行包括温度载荷在内的应力场的精确计算, 最后进行应力分析设计。按以上思路, 笔者进行了薄膜蒸发器夹套结构的流固耦合对流传热数值模拟, 在本文中建立了结构的有限元计算模型, 进行了原结构和改进设计结构的应力分析, 并按沿线进行强度评定方法进行了强度评定。1有限元模型建立111夹套结构和温度场18m 2薄膜蒸发器是一种直立容器, 主体分3段筒节, 每段结构相同, 其中的一段结构见图1。在夹套的中间位置有一个厚壁加强圈, 加强圈上有许多沿圆周方向均布的通孔, 以便导热油流过。容器的主要设计参数如表1所示。容器筒体内80水系混合物溶液从筒体内壁面顶部降

3、膜流下, 容器筒体外表面夹套中320的导热油从夹套底部进入, 经与筒体外壁面换热后, 从夹套上部侧面出口离开。夹套结构对流传热数值模拟的计算域见图2, 计算出的夹套封口环处温度场见图3。图118m 2薄膜蒸发器筒节结构简图表118m 2薄膜蒸发器主要设计参数设计参数设备内夹套设计压力/MPa -0. 10. 4设计温度/200320工作介质水系混合物溶液导热油焊缝系数0. 850. 85腐蚀裕度/mm 1. 01. 0主要受压元件材料0Cr18Ni916MnR容器类别741第28卷第3期化工机械刘友宏, 男,1963年11月生, 副教授。北京市,100084。 图2图3夹套封口环处温度场等值线

4、图112网格划分因为容器具有轴对称性, 所以采用轴对称实体单元对图1的夹套结构进行网格划分。另外 , 由于筒节结构在轴线方向具有1/2 对称性, 同时使用时夹套的上封口环最先泄漏, 所以取加强圈以上的半筒节为研究对象。经过网格划分试验和调整, 在充分保证计算精度的条件下, 划分的有限元网格如图4所示。容器筒体划分单元的最大长度为0109(RT 1/2, 远小于(RT 1/2, 满足Mershon 准则1。对原设计划分的单元总数为849, 节点总数为1136。改进设计后划分的单元总数为1005, 节点总数为1344。113载荷和约束计算中考虑的载荷:夹套内的筒体部分承受压力载荷为0. 5MPa

5、; 夹套内的其他部分表面承受压力载荷0. 4MPa ; 夹套外容器筒体的外表面承受0. 1MPa 压力载荷; 所有固体壁面中各节点的温度载荷按数值模拟结果输入。a. 原设计图4有限元网格划分图约束条件:在图4所示的有限元模型网格中,由于加强圈的刚度很大, 并且处于对称面上, 所以此面上节点的轴向位移和转动自由度均为0。另外与上法兰连接的筒节各节点径向位移和转动自由度均为0。114有限元计算软件采用有成熟使用经验的通用有限元计算软件A LG OR 2FE A12有限元分析系统。2有限元应力计算与改进设计根据上面建立的有限元计算模型, 分2种载荷工况进行了计算:在工况一下结构承受压力和温度的作用;

6、 在工况二下结构仅承受压力作用。原设计的薄膜蒸发器在工况一下最大应力点附近841化工机械2000年的应力强度场如图5所示, 结构中的最大应力点位于筒体与封口环连接的焊缝区, 其虚拟弹性最大应力强度已远远超过材料的屈服限, 必须进行强度评定。该焊缝区在工况二下的应力强度场如图6所示。从图5、6中可见, 压力载荷引起的应力是很小的, 而温度载荷引起的应力却非常大。工况一下最大应力点和工况二下同一点的各应力分量见表2 。图5 图6原设计工况二下应力强度等值线图表2最大应力点的各应力分量值MPa 应力分量原设计工况一工况二改进设计工况一11-2000. 39. 6-435. 0227. 1-0. 11

7、. 633-743. 06. 6-166. 61227. 32. 14. 423000 在改进设计中, 为了能有效降低温度载荷的作用, 夹套材料选用了热膨胀系数较小的碳素钢, 同时在夹套的中间增设了一个标准波形膨胀节(具体结构和尺寸参见L130026,JB1121283 。改进设计的薄膜蒸发器在工况一下最大应力点附近的应力强度场如图7所示。结构中的最大应力点仍位于筒体与封口环连接的焊缝区, 膨胀节中的应力水平较低。最大应力点的虚拟弹性最大应力强度已超过材料的屈服限, 也必须进行强度评定。对比图5, 最大应力点附近的应力水平已有大幅度的降低, 最大应力点的各应力分量见表2。图7改进设计工况一下应

8、力强度等值线图3强度评定311依据按照AS ME 卷第二册中AD 2140, 剪应力理论, 2倍, 即:S 12|,|2-3|,|3-1|应力强度; 1、2、3主应力。根据AS ME 锅炉及压力容器规范第卷第二册强制性附录4(以应力分析为基础的设计 中的规定:一次总体薄膜应力强度P m 应不超过设计许用应力强度S m , 即:P m S m一次局部薄膜应力强度P l 许用极限为115S m , 即:P l 1. 5S m一次局部薄膜应力加一次弯曲应力的应力强度P l +P b 的许用极限为1. 5S m , 即:P l +P b 1. 5S m一次局部薄膜应力加一次弯曲应力以及二次应力的应力强

9、度P l +P b +Q 的许用极限为3S m ,即:P l +P b +Q 3S m 一次局部应力加二次应力以及峰值应力的应力强度P l +P b +Q +F 的许用应力幅为2S a , 即:P l +P b +Q +F 2S a 式中S a 容器材料在一定循环次数下的疲劳许用应力幅。薄膜蒸发器夹套加热结构在封口环固体壁内的应力类型有:总体一次薄膜应力P m 、局部一次薄膜应力P l 、二次应力Q 和峰值应力F 。从而对薄膜蒸发器中的最大应力点进行强度校核,16MnR 在设计温度下的许用应力强度S m =170MPa 。941第28卷第3期化工机械312结构的应力强度计算与评定为了从有限元分

10、析结果中得到薄膜、弯曲和峰值等各类应力强度, 本文采用沿线进行强度评定方法进行计算2。首先在截面上过最大应力点沿壁厚方向确定一条应力处理线A 2A , 如图4所示。沿该线建立一局部坐标系, 为便于处理, 在应力为最大值的一端=1, 另一端=0。然后, 根据静力等效和静力矩等效原理, 分离出各类应力分量, 进行强度计算, 计算结果如表3所示, 其中计算步骤见图8。表3薄膜蒸发器夹套结构有限元分析应力处理结果应力处理线A 2A 局部一次膜应力强度S = 1m -3m一次加二次应力强度S =1m+b -3m+b峰值应力强度S =1F -3F原设计工况一355. 7>1. 5S m 2009.

11、2µ3S m 2075. 4µ3S m 改进设计工况二49. 0<1. 5S m393. 4<3S m416. 0<3S m图8各类应力分量强度计算步骤4结论411仅按压力载荷引起的应力场进行强度计算,原设计结构是相当安全的。412温度应力的附加作用是导致薄膜蒸发器筒体与夹套的封口环处焊缝穿透裂纹、泄漏的主要原因。413在薄膜蒸发器夹套上增加膨胀节后, 结构是安全的。414当夹套加热容器筒体两侧的温度差较大时,设计中应进行固体壁中的温度场计算, 然后进行分析设计。参考文献1Mershon J L. N ozzles and Branch Pipes in

12、Cylindrical Shells 2C omparis on of Experimental and Analytical Methods for E lastic Analysis Under Internal Pressure and External M o 2ment. WRC Bulletin in preparation ,19942李永生, 沈迅伟, 於孝春. 受压圆筒矩形大开孔的三维有限元分析与强度评定. 压力容器,1996,13(4 :4450(收稿日期:2000211216, 修回日期:2001202220051化工机械2000年sults of heat exchan

13、gers with various flow patterns was made. K ey Words :Heat Exchanger , F oul , Heat T rans fer Perfor 2manceStre ss analysis of the integrate jacket seal ring of the cylinder of a thin film evaporator and its improvement de 2sign.Liu Y ouhong (Qinghua University ,Beijing ,China Hu G uolin (Design In

14、stitute , Jinling Division , S inopec , Nanjing , Jiangsu , China (147Based on the numerical simulation result of convective heat trans fer ,the finite element calculating m odel of the integrate jack 2et structure of the cylinder of a thin film evaporator was estab 2lished , the stress analysis and

15、 the intensity calculation of the structure were made using the finite element method. The result shows that the structure was safe when the temperature load was not in consideration ; the structure was not safe when the temper 2ature load was in consideration. The structure design was im 2proved ,

16、and the corresponding intensity calculation was , they were success ful in practice.K ey Words :Thin Film AnalysisStructure two stage petrochemical flow pump s and their Zhao Wany ong (G ansu University of T echnology ,Lanzhou ,G ansu ,China (151The various structures of the centrifugal petrochemica

17、l flow pumps were compared ,the important action of adopting the dou 2ble 2extracting impellers and the double 2turbine pressure chambers for increasing erosion performance and balancing radial force was described. The theoretical analysis , test result , and commercial application show that the vib

18、ration of the pumps could be re 2duced ,the efficiency of the pumps could be increased ,the high efficiency zone could be extended by using the small blade exit angle 2,the impellers with less blade number Z and large blade wrap angle ,and tw o middle transition channels with X 2shaped distribution.

19、K ey Words :ChemicalFlow Pump ,S tructure Design Simple criterion of the equivalent area reinforcement of the openings of pre ssure ve ssels. Deng X iaoming (G uangdong Petrochemical C ollege ,Maoming ,G uangdong ,China (153Based on the compensation principle of equivalent area of the openings of pr

20、essure vessels and the design formulae regulated in National S tandards ,a simple criterion of opening rein forcement was derived. The simplicity and reliability of the formula were described ,the function of applying the simple criterion to simpli 2fying calculation process was als o described.K ey

21、 Words :Pressure Vessel ,Opening ,Rein forcement ,Cri 2terionFailure analysis of the jacket tube s of a cooling effluent steam heater. Chen G uofeng (E thylene Plant ,G uangzhou Petro 2chemical C omplex ,G uangzhou ,G uangdong ,China (155The failure cause of the jacket tubes of a cooling effluentste

22、am heater was analyzed ,the result shows that the major cause was stress corrosion ,and s ome improvements were proposed.K ey Words :Stress C orrosion ,Jacket Tube of Heater , Fail 2ure AnalysisCrack failure analysis of cylinder dryers.Lin Ping , Y ue Bin ,Li Changxi ,Liao D ongtai ,Ma Pengju (Res.

23、Inst of Chem. Mach ,Lanzhou ,G ansu ,China (157A macro 2analysis and a micro 2analysis was made for the weld seam cracks on the cylinder dryers in a compound fertilizer plant ,and it was found out that the cause was stress corrosion cracking ,and s ome repair methods were K ey Words :Stress C orrosi

24、on of tpye nitrogen 2ssors. , Y ang Y ingjie (Shanxi C o ,Shanxi ,China (160rings in the second section of 3D22 compress ors were changed into the packed MC nylon rings in a retrorit ,the structure calculation of the packed MC nylon piston rings and their retrofit result were presented. The cast iro

25、n piston rings in the first section and the third section were als o retrofitted based on the experience above mentioned.K ey Words :Nitrogen2Hydrogen C ompress or ,Piston Ring Non 2preheating weld between 15CrMoR steel and A3R steel. Liu Lanju (Shengli Refinery , Qilu Petrochemical Industry C orpor

26、ation ,Z ibo ,Shandong ,China (162The non 2preheating weld process between 15CrM oR heat re 2sistant steel and A3R low carbon steel was presented.K ey Words :15CrMoR S teel ,A3R S teel ,Weld ,Preheating Application of the compensation principle of wall thick 2ne ss in the proce ss of bending R/D <2tube s. H ou X i 2aofen g , Sha Quanshu , Zhang Y ong , Zhang Xuefeng (Daqing Petrochemical Machinery Plant ,Daqing ,Heilongjiang ,China (164 The application of the compensation principle of thick wall in bending tubes was