Carrying Capacity Of Cushioned Spiral Case And Vibration Of Powerhouse In Hydro-plant

Powerhouse is one of the main constructions in the hydro-plant.According to the increase of operation water head and unit capacity and improvement of plant vibration control requirements,the carrying capacity of spiral case and the anti-vibration ability of plant structure are getting more and more attention.The carrying capacity of the cushion volute structure is affected by several factors,such as friction contact effect between the steel spiral case and concrete or cushion,material properties and arrangement range of cushion and others.Compared with ground powerhouse,the effect of the consolidation of the surrounding rock on the vibration of underground powerhouse is also need to be studied.Combined with the actual underground powerhouse of a hydropower station and based on the finite element software ANSYS,the primary research contents are as follows.(1)The presence or absence of friction contact effect between the steel spiral case and concrete or cushion on carrying capacity of spiral case were compared.Besides,the friction coefficient,arrangement range of cushion lower end,elastic modulus of cunshion,thickness of cushion,plane arrangement range of cushion were researched.The results show that adopting friction contact model will be more close to the actual situation.Increasing friction coefficient,elastic modulus of cunshion,and decreasing arrangement range of cushion lower end,thickness of cushion appropriately can enhance anti-shear capacity and anti-torsion capability of penstock and stay ring.On the contrary,it will increase the proportion of internal water pressure transmitting outward.The effect of plane arrangement range of cushion on the distribution ratio of unbalanced force and torque,the concrete stress level and the proportion of internal water pressure transmitting outward is not identical.Determining plane arrangement range of cushion should be based on the principle of first solving the main problem.(2)The effect of concrete dynamic elastic modulus,boundary conditions and water simulation mode on the self-vibration characteristics of plant structure was researched.The results indicate that the vibration of structure above volute layer manifest in most of the top 20 vibration modes of the plant structure.Specifically,floors are weak parts of the plant vibration.While the ratio of concrete dynamic elastic modulus and static elastic modulus augment 20 percent,the natural frequencies will aggrandize 6 to 8 percent.Strengthening the constraints of the surrounding rock can effectively improve the anti-vibration capability of powerhouse structure.Actual engineering should pay special attention to the consolidation between surrounding rock and structure above volute layer.Passage water has little effect on the self-vibration characteristics of plant structure.It is feasible to simulate with mass element or fluid-solid coupling method,while employing mass element method is more convenient and efficient.(3)According to the engineering practice,the influence of the application mode of mechanical horizontal dynamic load on the vibration response of the powerhouse was discussed.In addition,the effect of structural damping ratio and concrete dynamic elastic modulus was also analyzed.It turns out that the horizontal vibration of unit foundation composite structure and the vertical vibration of floors near hole or electromechanical equipment is relatively obvious.The application mode of mechanical horizontal dynamic load has a great influence on the vibration response of the powerhouse.It is more reasonable to apply the radial vibration load to the four base plates near upstream and middle for the plant.With the increase of the structural damping ratio and the concrete dynamic elastic modulus,the vibration response of plant will decrease.The damping ratio 0.05 can meet the anti-vibration requirements of powerhouse.Using high strength concrete as far as possible can improve the anti-vibration capacity of plant.