低温管系动力学响应分析

发布时间：2018-05-23 10:54

本文选题：低温管系 + 动态分析　；参考：《兰州理工大学》2017年硕士论文

【摘要】：在低温领域,低温管系用以输送流体介质、传递流体动力及信息。与低温管系相连的各种动力设备(如往复式压缩机、泵)工作时存在一定的间隙性与周期性,动力设备对管内流体提供一定的激发,使管内流体呈脉动状态。脉动流体对管系弯头、异径管、阀门等元件集中施加一定周期的脉动激振力,引发管系振动。管系振动会使管系连接部位发生磨损、松动,使管系支吊架发生疲劳断裂。若管系持续振动,会造成仪器仪表精度下降,接管、三通及弯头损坏进而引起整个管线的破坏,造成严重事故。结合国内外管系振动标准,以蓝科高新2万方低温贮罐配套管系(低温乙烯液体输送管系)为研究对象,对低温管系中动力设备引起的振动问题进行研究,分析引起低温管系振动的原因及影响管系振动的因素,并应用CADWorx或CAESARII软件建立低温管系物理模型,针对不同工况下低温管系进行静力学与动力学响应分析,根据计算结果提出了相应的改造措施。具体工作包括:1.进行低温管系静力学分析,校核了低温管系的一次应力、二次应力及管系位移水平,验证了现行设计的可行性,并介绍了不同类型的低温管系支吊架建模注意事项及其使用方法。利用CAESARII软件对管系进行了应力、位移、约束分析,结果表明管系最大应力比均小于1,管系线位移偏大,管系横向、纵向受力较大。因此,管系与设备连接管口因承受设备重量、基础沉降等受力过大;管系中因固定支撑与导向不足,管系稳定性不够。据此提出了相应的改造措施,优化管系设计。2.以低温潜液泵出口管系为例,应用CAESARII软件进行谐响应分析,获得了潜液泵轴频激励下流体压力脉动激发的管线谐响应结果。表明:原管系基频过低,应力超标,压力脉动下管系振动剧烈,需采取一定的防护措施以消弱管系振动。通过改变管系支撑结构与布置,减小管口附加位移,调整阀门等附件在管系中的位置,一次应力比降低了38.8%,二次应力比为原来的3倍,基频提高了219.5%。管系固有频率避开了共振区,最大振幅从22mm减小到不到2mm,管系振动趋势明显减弱。3.应用CAESARII软件对某低温乙烯液体输送管系进行动态分析,校核了在泄放阀泄放反力作用下管系的位移、应力是否符合规范,并对管系结构进行了优化。结果表明:原管系基频过低、应力超标,距离泄放阀最近端管系弯头纵向振幅较大,泄放阀泄放反力作用弯头位置横向振动剧烈,须重新对管系进行改进。据此提出改进方案:(1)将管系中间位置约束改为固定支撑,以增大管系刚度;(2)将距离泄放阀最近弯头处承重支撑改为弹簧支撑,以承担竖直方向的反冲力;(3)在泄放阀进口管段设置阻尼约束,泄放阀出口管弯头位置加设承重支撑与限位,并调整限位与管系之间的间隙,找到最佳间隙为6.63 mm。据改进后的方案重新建模并分析,管系在X、Y、Z向的最大振幅分别减弱了88.12%、76.02%、99.86%。
[Abstract]:In the cryogenic field, cryogenic pipes are used to transport fluid media and transfer fluid dynamics and information. All kinds of power equipment (such as reciprocating compressors and pumps) connected with the low temperature pipe system have certain gap and periodicity when working. The power equipment provides a certain excitation to the fluid in the pipe and makes the fluid pulsate in the pipe. The pulsating fluid exerts a certain period of pulsating excitation force on the pipe elbows, diameters, valves and so on, which causes the pipe system to vibrate. The vibration of the pipe system will make the connection part of the pipe system wear and loosen, and make the support and hanger of the pipe system fatigue fracture. If the pipe system continues to vibrate, it will cause the instrument precision to decline, the pipe, the three way and the elbow damage, then causes the entire pipeline destruction, causes the serious accident. The vibration problem caused by power equipment in low temperature pipe system is studied by taking Lanke hi-tech 20 thousand square cryogenic tank system (cryogenic ethylene liquid conveying pipe system) as the research object in combination with the vibration standard of domestic and foreign pipe system. The causes of low temperature tube system vibration and the factors influencing the low temperature tube system vibration are analyzed. The physical model of low temperature pipe system is established by using CADWorx or CAESARII software. The static and dynamic responses of low temperature tube system under different working conditions are analyzed. According to the result of calculation, the corresponding measures are put forward. Specific tasks include: 1. The static analysis of the low temperature pipe system is carried out, and the primary stress, secondary stress and displacement level of the low temperature pipe system are checked, which verifies the feasibility of the current design. The paper also introduces the matters needing attention in modeling of different types of low-temperature pipe suspension and their application methods. The stress, displacement and constraint of the pipe system are analyzed by CAESARII software. The results show that the maximum stress ratio of the pipe system is less than 1, the line displacement of the pipe system is larger than that of the pipe system, the transverse and longitudinal stress of the pipe system is larger. Therefore, because of bearing the weight of the equipment and the settlement of the foundation, the pipe system and the connecting nozzle of the equipment are subjected to too much force, and the stability of the pipe system is not enough because of the insufficient fixed support and guidance in the pipe system. Based on this, the corresponding measures are put forward to optimize the design of pipe system. Taking the outlet pipe system of cryogenic submersible pump as an example, the harmonic response of pipeline excited by axial frequency excitation of submersible pump is obtained by using CAESARII software. The results show that the vibration of the original pipe system is too low, the stress is over the standard, and the vibration of the pipe system is intense under the pressure pulsation. Some protective measures should be taken to reduce the vibration of the pipe system. By changing the support structure and arrangement of the pipe system, reducing the additional displacement of the pipe opening and adjusting the position of the valve and other accessories in the pipe system, the primary stress ratio is reduced by 38.8 times, the secondary stress ratio is 3 times that of the original one, and the fundamental frequency is increased by 219.55. The natural frequency of the tube system avoids the resonance region, the maximum amplitude decreases from 22mm to less than 2 mm, and the vibration trend of the tube system obviously weakens by .3. The dynamic analysis of a cryogenic ethylene liquid conveying pipe system was carried out by using CAESARII software, and the displacement and stress of the pipe system under the action of the releasing reaction force of the release valve were checked, and the structure of the pipe system was optimized. The results show that the base frequency of the original pipe system is too low, the stress exceeds the standard, the longitudinal amplitude of the elbow of the nearest end of the discharge valve is larger, and the lateral vibration of the elbow position of the relief valve acting on the releasing reaction force is intense, so the pipe system should be improved again. Accordingly, an improved scheme: 1) to change the middle position constraint of the pipe system to a fixed support to increase the stiffness of the pipe system is put forward. (2) the load-bearing support at the nearest elbow of the relief valve is replaced by a spring support. The damping constraint is set in the inlet section of the outlet valve, the load bearing support and limit position are added at the elbow position of the outlet pipe of the discharge valve, and the clearance between the limit position and the pipe system is adjusted, and the optimum clearance is found to be 6.63 mm. According to the remodel and analysis of the improved scheme, the maximum amplitude of the tube system in the direction of XNY _ (Z) is reduced by 88.128.12 / 76.02 / 99.86, respectively.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ055.81

【参考文献】