基于原型观测的梯级泵站管道振源特性分析

Analysis of vibration characteristics of pipeline of trapezoid pumping station based on prototype observation

以景电二期3泵站2号输水管道为对象,结合原型试验观测数据,研究该类型泵站结构的振源组成及其对管道的影响。首先,对连接2号管道的4号、5号机组正常运行和开关机过程中引起的管道结构振动频率进行识别统计,确定其动荷载来源;然后,分析统计不同工况下管道结构主要部位达到峰值时各分频所占比例,计算不同工况下各频带能量对总能量的贡献率。计算结果表明:机组稳定运行时,叶频和转频倍频引起的振动比例达73.4%,是管道振动的主振源低频所占比例为12%左右;机组开机过程中,低频水流脉动所占比例增加到33.7%,叶频所占比例保持40%左右,叶频和低频是主要振源;机组关机过程中,低频水流脉动引起的振动比例达73.3%,水体-管道耦合引起的高频振动达21.7%左右,低频水流和高频是主要振源,且低频对管道顺水流方向振动影响较大。研究结果有助于从量级上评价管道振动的原因及引起振动的各分频贡献率,以期为管道结构主动控制和安全运行提供依据。

Pipeline is a carrier of cascade pumping station with long distance water conveyance. Therefore, it is particularly important to keep the stable operation of pipeline structure. In order to ensure the safe operation of pipeline structure, it is significant to research the main influence factors of pipeline vibration and the contributions of different factors to pipeline structure. Based on prototype observation data, vibration source compositions and their influences on pipeline structure were investigated through analyzing the power spectral density of vibration data. Taking the No.2 pipeline of Pumping Station 3 in Jindian River pumping irrigation as the research object, six points were set up in different parts of pipeline. Three vibration sensors were placed in each measuring point, from which vibration data were collected in three directions of pipeline. First of all, on the basis of mathematical statistics theory and the observation data of vibration sensors, vibration frequencies of pipeline structure excited by four and five units in the process of normal operation and switch machine were identified according to the spectrum analysis. Dominant frequencies of pipeline structure were counted under different working conditions to determine the dynamic load sources and to introduce the vibration source compositions of pipeline structure. Furthermore, the contributions of different frequencies were calculated when the vibrations of main points reached the maximum values under different working conditions. At the same time, the contributions of the measured frequency bands energy to the whole vibration response were calculated. The analysis results showed that, under the working condition of steady operation of units, the contribution of vibration energy caused by blade frequency and rotation frequency was 73.4%, and the contribution of low frequency water-flow pulsation was about 12%. During unit start-up, the vibration energy contribution of low frequency water-flow pulsation was increased to 33.7%, and the contribution of blade frequency still was about 40%. During unit shutdown, compared with the steady operation conditions, the vibration energy contributions of low frequency and high frequency induced by water-pipeline coupling were increased by 73.3% and 21.7%, respectively. The study showed that the vibration of blade frequency and rotation frequency were the main vibration sources when the unit was stable in operation. The vibration of blade frequency and low frequency water-flow were the main vibration resources during unit start-up. The low frequency water-flow and high frequency induced by water-pipeline coupling were the main vibration resources during unit shutdown, and low frequency water-flow had greater effect on pipeline vibration along the direction of flow. The research results can be used for evaluating the sources of pipeline vibration and the contributions of different frequencies. This study provides a scientific basis for the safe operation and active control of pipeline structure.