Research On Coupled Vibration Characteristics And Vibration Control Of Pipeline Of Cascade Pumping Station

In order to solve the problem of uneven distribution of regional water resources and increasing demand for industrial and agricultural water and domestic water supply,many cross-regional and cross-river long distance pipeline projects of pumping station are built energetically in recent years.Due to the complicated internal structure of centrifugal pump,and the interaction between high-speed water and pipeline,and long-distance and long-span characteristics of pipeline,as a carrier of cascade pumping station with long distance water conveyance,it is subjected to varying degrees vibration disturbance during operation.Therefor,it is particularly important to keep the stable operation of pipeline structure.Pipeline vibration is complex coupled vibration of ‘ground-water-pipe’ trinity.Due to the diversity and complexity of the causes of hydraulic factors,it is very difficult to determine the excitation source of pipeline vibration under each condition.Therefore it is significant to research the vibration information extracted and analysis of vibration source composition.Taking 3 pumping station 2 pipeline of Jintai river pumping irrigation as the research object,based on prototype test pipeline data,combined with digital information processing technology and modal parameter identification technology,this paper is aimed at investigations on coupled vibration characteristics and vibration source characteristics of the pipeline as well as the vibration source composition.The main results are as follows:(1)Vibration feature information extraction of pipeline of cascade pumping station.Firstly,a novel de-noising method,which combines wavelet threshold and empirical mode decomposition(EMD),is proposed.WT-EMD filtering method is used to process vibration signal to achieve a higher precision de-noised signal.The useful dominant dynamic characteristics of structure are highlighted,which decreases the noise interference to a large extent and avoided the false modal interference effectively during the later modal parameter identification processing.Then the de-noised signal is conducted by the improved HHT method,and the structure modal parameter is obtained.It is provides the basis for analyzing the causes of pipeline vibration.(2)Study the vibration source composition of pipeline of pumping station.Taking the No.2 pipeline of Pumping Station 3 as the research object,on the basis of mathematical statistics theory and the observation data of vibration sensors,vibration frequencies of pipeline structure excited by 4 and 5 units in the process of normal operation and switch machine are identified according to the spectrum analysis.Dominant frequencies of pipeline structure are counted under different working conditions to determine the dynamic load sources and introduce the vibration source compositions of pipeline structure.Furthermore,the contributions of different frequencies are 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 are calculated.(3)Study on vibration control and vibration reduction of pipeline.According to the analysis of the vibration source,the main vibration source of the pipeline vibration under each working condition is determined,based on structure frequency,pipeline vibration reduction system is established.TMD vibration control technology is used to simulate the pipeline vibration reduction.The result shows that it is correct and effective.At the same time,the mass ratio of TMD,the number of devices and the installation position are compared,so as to clear the above three factors influence on TMD vibration reduction effect.The results can provide basis for the analysis of vibration control and vibration reduction of the similar engineering structure,which can ensure the safe operation of pipeline structure.