Vibration Interaction Of Adjacent Units In Underground Powerhouse Of Pumped Storage Power Station

With the continuous development of water conservancy and hydropower industry in China,more and more pumped storage power stations have been constructed.The vibration of hydropower plant buildings is related to the safe operation of hydropower plant buildings and units,and is also closely related to the safety of hydropower station staff.The space structure of the pumped storage power plant is very complicated.The powerhouse has high water head,large unit capacity and high unit speed.With the significant increase in the size of turbines and generators,the rigidity of the unit and supporting structure is relatively reduced.The various excitation forces acting on the unit have increased sharply,and the prediction and the control of the vibration has become increasingly difficult.The vibration problem of the plant structure is particularly prominent and unavoidable,which will cause different degrees of vibration of the adjacent plant unit.In order to meet the requirements of fast and accurate frequency adjustment of the power grid and improve the stability of the power grid,some newly built pump-storage power stations need to use two units with different speeds,or even variable speed units.When adjacent units are running at different speeds,the analysis and evaluation of the dynamic interference between the plant structures of the unit sections becomes an important issue in the design and research of the underground powerhouses of pumped storage power plants.This paper takes the underground powerhouse of a pumped storage power station as the research object,and establishes a complete model of the underground powerhouse structure of two units adjacent to each other with different speed units.This paper systematically studies the mutual influence of unit vibration load and flow channel pulsating pressure on the structure vibration of the adjacent unit section.The influence of the elastic modulus of the filler falling into the structural gap between the unit sections on the vibration transmission between the unit sections was also investigated.The specific research content and conclusions can be summarized as follows:(1)Take a practical project as the research object and establishes a finite element model including the structure of two adjacent unit sections,the influence of vibration load of two units on the vibration displacement and acceleration of adjacent units is calculated and analyzed.The results show that the vibration load of the unit in normal operation has little effect on the vibration of the adjacent unit section,and the vibration load of the unit in runaway operating condition has significant effect on the vibration acceleration of the adjacent unit section.The increase of vertical root mean square acceleration of volute layer column reached 113.33%.However,due to the low vibration load frequency of the units,the acceleration of the plant structure is not too large,and the maximum acceleration of the root mean square in each part of the unit sections does not exceed 0.20 m/s2.It shows that the vibration load of the unit under runaway operating condition can significantly increase the vibration acceleration of the plant structure of the adjacent unit section,but it will not cause the deterioration of the structural vibration state and have a significant adverse effect.(2)Simulate the pulsating pressure in the hydropower plant flow channel.The maximum dynamic displacement,velocity and acceleration changes of each structural in the two-unit operating condition and the single-unit operating condition are very small.The result shows that the pulsating pressure of the adjacent unit section has very little effect on the vibration of the main plant structure and will not have significant adverse effect on the structure.(3)It is assumed that rigid filler falls between the floor slabs of the two-unit section and in the structural joints below the floor slab.The longitudinal displacement of the structure increases under the action of the unit vibration load of the adjacent unit section alone,and the maximum longitudinal displacement ratio reaches 3.3.The longitudinal displacement ratio of the structure increases rapidly with the increase in the elastic modulus of the filler and then rapidly stabilizes,and the rate of change of the longitudinal displacement ratio is greater than that of the lateral and vertical displacement ratio.When the pulsation pressure of the adjacent unit section is acting alone,the structural acceleration changes significantly,with a maximum acceleration amplitude ratio of 10.04 and a maximum acceleration of 3.58 m/s2,which are much larger than the corresponding value when there is no filler in the structural joint.The modulus of elasticity of the filler in the structural seam has the greatest influence on the longitudinal vibration of the plant structure of the adjacent unit section,and the influence on the vertical and lateral vibration is relatively small.(4)The falling of hard filler into the structural gap between the units will have an adverse effect on the vibration transmission of the structure between adjacent units.It is recommended to fill the structural joints with low-elasticity mold materials such as foam boards during construction,or to install cover plates immediately above the joint surfaces after the structural joint surfaces are formed,to avoid hard fillers falling into during construction and operation.