长距离输水气液两相流管道振动特性研究

发布时间：2018-05-05 06:35

本文选题：长距离输水 + 气液两相流　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：长距离输水管道因气水两相流动状态不断转变而产生的强烈压力波动会诱发管道剧烈振动,引起管道连接部位的松动泄漏和整体结构稳定性的降低,甚至发生爆管现象。为了提高长距离输水管道运行的安全性,并探究气液两相流不同流型下重力输水和加压输水的管道振动特性,本文从气液两相流流型的基本理论出发,基于两相流体与管道的流固耦合作用,对长距离重力输水和加压输水两种方式在不同运行工况下的管道振动幅频特性进行了研究。采用理论与试验结合的方式,建立了气液两相流管道振动数学模型,理论分析了管道结构属性与气液两相流体流动特性对输流管道系统振动固有特性的影响。选用有机玻璃管材搭建长距离输水管道试验平台,通过调节气泵进气压力控制进气量在0~3.0m3/h之间并调节阀门控制流速在0.7~1.9m/s范围内,同时模拟重力输水和加压输水两种方式的稳态运行和关阀过渡过程工况。采用三向振动加速度传感器对水平管道、45°上升管道、45°下降管道以及阀门部位进行稳态条件下的振动响应检测,获得管道轴向和径向振动加速度频谱图。使用关阀时间可控的电动球阀和气动蝶阀进行过渡态试验,研究关阀和事故水锤对管道振动幅频特性的影响。理论和试验结果表明,管道系统的固有频率会随着管径或管材弹性模量的增大以及管长或管材密度的减小而提高。气液两相流含气率的加大在提升管道系统固有频率的同时也会提高水平管道的振动强度。在同一水流速下,水平管道轴向振动强度随含气率的增加而增大,于泡状-段塞流过程增长速率最快,并在段塞流流型时达到最大。由于水平管道段塞流振动频域较宽,极有可能发生管道共振,实际运行中应尽量避免该工况的出现。上升管弯头由于连接耦合作用,振动强度大。下降管段的振动强度与管内气团的发展密切相关,应尽量避免非满管流的产生。气液两相流过阀产生的局部扰动对上游近阀管段的径向振动影响剧烈,使管道径向振动向高频区域发展,轴向振动受其影响较小。快关阀试验中气体的存在会降低管道中的水锤升压,且含气率越高其降低的幅度越大,但水锤波和管道振动的持续时间变长。这些对于长距离输水管道的设计、改造及运行具有较大的参考意义。
[Abstract]:The strong pressure fluctuation caused by the continuous change of the gas-water two-phase flow state in the long distance water conveyance pipeline will induce the pipeline to vibrate violently, cause the loosening and leakage of the connection part of the pipeline, decrease the stability of the whole structure, and even cause the phenomenon of pipe burst. In order to improve the safety of long distance water conveyance pipeline and to explore the vibration characteristics of gravity water conveyance and pressurized water conveyance pipeline under different gas-liquid two-phase flow patterns, this paper proceeds from the basic theory of gas-liquid two-phase flow pattern. Based on the fluid-solid coupling between two-phase fluid and pipeline, the amplitude and frequency characteristics of pipeline vibration under different operating conditions were studied. A mathematical model for the vibration of gas-liquid two-phase flow pipeline is established by combining theory and experiment. The influence of pipeline structure properties and gas-liquid two-phase fluid flow characteristics on the natural vibration characteristics of pipeline system is analyzed theoretically. The plexiglass pipe is selected to build the test platform for long distance water conveyance pipeline. By adjusting the inlet pressure of the air pump to control the air intake between 0~3.0m3/h and the valve to control the flow rate in the range of 0.7~1.9m/s, At the same time, it simulates the steady operation of gravity water conveyance and pressurized water conveyance and the transient process of closing valve. The axial and radial vibration acceleration spectrum of horizontal pipeline is obtained by using three-direction vibration acceleration sensor to detect the vibration response of 45 掳descending pipeline and the position of valve under steady condition. The effect of shutoff valve and accident water hammer on the vibration amplitude-frequency characteristic of pipeline was studied by using electric ball valve and pneumatic butterfly valve with controllable closing time. The theoretical and experimental results show that the natural frequency of the pipe system increases with the increase of the diameter of the pipe or the elastic modulus of the pipe and the decrease of the length or density of the pipe. The increase of gas-liquid two-phase flow gas holdup can not only raise the natural frequency of pipeline system, but also increase the vibration intensity of horizontal pipeline. At the same water flow rate, the axial vibration intensity of horizontal pipeline increases with the increase of gas content, the fastest growth rate occurs in the bubbly slug flow process, and it reaches the maximum at the slug flow pattern. Due to the wide frequency domain of the slug flow vibration in the horizontal pipeline, it is very likely that the pipeline resonance will occur, which should be avoided in the actual operation. The vibration intensity of the riser elbow is high because of the coupling effect. The vibration intensity of the descending section is closely related to the development of the air mass in the pipe, and the non-full flow should be avoided as far as possible. The local disturbance caused by gas-liquid two-phase flow through the valve has a strong influence on the radial vibration of the upstream near valve section, which makes the radial vibration of the pipeline develop to the high-frequency region, and the axial vibration is less affected by it. The existence of gas in the fast closing valve test will reduce the pressure rise of water hammer in the pipeline, and the higher the gas content is, the larger the reduction range is, but the longer the duration of water hammer wave and pipeline vibration is. These are of great reference significance for the design, transformation and operation of long distance water conveyance pipeline.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU991.3

【引证文献】