Study on Calculation Method of Butterfly Valve Shaft Considering Fatigue Effect
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摘要: 阀轴是蝶阀的关键受力部件,传统方法基于扭矩计算阀轴应力而未充分考虑弯矩的影响,应用于大型蝶阀设计存在一定的风险。本文分别将滑动轴承支反力简化为均布载荷和集中力,与变形协调方程相结合,提出了一种新的阀轴弯扭组合数学模型,采用有限元方法和实验方法对数学模型进行了验证;最后,分别采用冯·密斯应力和Goodman准则对阀轴应力进行评定,得到阀轴设计安全系数。结果表明,本文提出的阀轴计算数学模型与评估方法具有较高的精度,对改进蝶阀设计方法具有重要指导意义。Abstract: The valve shaft is the key force component of butterfly valve, the traditional calculation method of the valve shaft stress is based on the torque which not fully considers the bending moment effect, so there exist the certain risks for applying to the large butterfly valves design. In this paper, the sliding bearing constraint force is simplified to uniform distributed-load or concentrated force, by combining with the compatibility equation, then a new model for valve shaft bending and torsion combination is proposed, thus finite element and experimental method is used to verify the present model. Finally, the valve shaft stress is evaluated with the Von Mises stress and Goodman criteria respectively, and the safety factor of the valve shaft design is obtained. The results show that the given model and evaluation method of the butterfly valve shaft calculation perform with high precision, which are of the important guiding significance to improve the design method of butterfly valve.
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Key words:
- butterfly valve /
- valve shaft stress /
- fatigue life /
- bending and torsion combination
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表 1 蝶阀运行条件与结构参数
物理量 数值 物理量 数值 阀门直径 0.9 m 工作压力 0.7 MPa 介质流速 8 m/s 介质温度 20 ℃ 阀轴轴径 11 cm 蝶板重量 379.5 kg 一偏心 8.8 cm 二偏心 1.6 cm 重锤大小 0.7 t 开阀油压 8 MPa 表 2 各危险工况载荷表
力矩/(N·m) 危险工况 1 2 3 重锤力矩 6 625.8 6 217.1 6 625.8 一偏心力矩 98 74.5 98 二偏心力矩 3 257.5 16 276.2 21 247.2 轴承摩擦力矩 1 676.8 2 456.9 4 867.7 填料摩擦力矩 214.2 215.6 215.1 密封面力矩 4 594.2 - - 动水力矩 - 6 021.1 - 表 3 危险工况阀轴剪应力
危险工况 1 2 3 剪应力/MPa 18.8 26.6 50.6 表 4 各危险工况主动力
分力 危险工况1 危险工况2 危险工况3 F1x/N 67 752.4 112 617.7 318 086.3 F1z/N 1 859.6 96 357.1 1 859.6 F2x/N 20 370.5 12 730.6 0 F2z/N 17 323.8 12 860.1 41 314.4 表 5 危险工况下轴套支反力和支反力矩
参数 危险工况 1 2 3 RBx/N 57 475.8 106 195.3 318 086.3 RBz/N -6 880.1 89 869.3 -18 983.0 RAx/N 10 093.9 6 308.2 0 RAz/N 8 584.2 6 372.4 20 471.9 MBx/(N·m) 869.3 11 092.7 1 789.8 MBz/(N·m) -8 234.4 -12 876.4 -34 989.5 表 6 各危险工况下载荷与应力
危险工况 位置 Mz/(N·m) Mx/(N·m) T/(N·m) σca/MPa 1 B 583.4 6 590.6 -1 892.4 52.0 2 B -4 846.6 10 795 2 672.5 110.2 3 B+ -93.0 15 904 5 083.3 126.3 表 7 集中力下阀轴应力
应力 危险工况1 危险工况2 危险工况3 σca 58.4 MPa 126.0 MPa 126.3 MPa 表 8 蝶阀主要材料性能
材料 弹性模量/MPa 泊松比 密度/(kg·m-3) 屈服极限/MPa 抗拉强度/MPa Q345A 206 0.28 7 850 345 470.0 2Cr13 230 0.25 7 750 440 687.5 表 9 各零件接触关系
销 短轴 长轴 蝶板 阀体 端盖 卡环 销 - 无摩擦 无摩擦 绑接 - - - 短轴 - - 无摩擦 有摩擦 - 无摩擦 长轴 - 无摩擦 有摩擦 - - 蝶板 - - - - 阀体 - 绑接 无摩擦 端盖 - 无摩擦 卡环 - 表 10 各工况下蝶阀载荷及方向
危险工况 压力/MPa 密封面力矩/(N·m) 油缸力矩/(N·m) 重锤力矩/(N·m) 动水作用力/N 动水力矩/(N·m) 静水力矩/(N·m) 1 0.213(-x) 4 594.3(y) 28 369.0(-y) 6 625.8 (y) - - - 2 0.710(-x) - - 6 217.1 (y) 294 024(-x) 6 021.1(y) - 3 1.000(x) 4 594.3(y) - 6 625.8 (y) - - 315.6(y) 表 11 各计算方法阀轴Von Mises应力
MPa 计算方法 危险工况1 危险工况2 危险工况3 均布载荷理论 52.03 110.23 126.29 集中力理论 58.40 126.00 126.30 有限元 58.81 128.38 102.76 表 12 阀轴剪应力
MPa 方法 危险工况1 危险工况2 危险工况3 有限元 20.25 57.76 31.66 阀门手册 18.83 26.59 50.57 表 13 各测点最大应力统计结果
测量点 2 3 4 5 6 7 载荷/MPa 64.5 56.6 47.1 65.5 27.3 37.4 表 14 实验工况下阀轴应力
MPa 实验 理论计算 有限元 65.50 69.63 64.22 -
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