Study And Calculation Of Pressure Distribution Of Hydropower Station Runner Belonging To Francis Hydro-turbine During Large Fluctuation Transient Process

The pressure of runner during the transient process of the hydropower station has an important impact on the economic and safe operation of the hydropower station.The Francis turbine is the most widely used type in the hydropower station in China.It is usually used in hydropower stations with high head.The pressure of the runner during the load rejection transient process poses a great threat to the safe operation of the unit.In this paper,large fluctuation transient process when the guide is closed totally is emphasized,by comparing the calculation results of the runner pressure distribution in the transient process of the high-head hydropower station with Francis turbine installed,it is concluded that the runner pressure distribution of the transient process via the multi-dimensional coupling method,has the shorter calculation time,higher calculation efficiency,and more accurate calculation results,when comparing to the single dimensional calculation.The main research contents and conclusions are as follows:1)When dealing with the synthetic characteristics curve,three-dimensional space surface interpolation method have higher calculation accuracy than the higher-order surface fitting and BP neural network fitting,and it can be used as the main method of numerical processing,while the BP neural network fitting method as a supplement.2)Through the three-dimensional hydraulic calculation of the entire runner of the hydropower station during the transition process,it is found that there is a large uneven pressure distribution phenomenon in the same flow cross section.The maximum difference between the maximum pressure and the minimum pressure at the same time reaches 149.64%.3)By comparing the calculation results of the pressure distribution in different dimensions of the flow channel of the same hydropower station during the transition process,the pressure pipeline area is obtained.The difference between the onedimensional pressure mean value of the same section and the three-dimensional calculated section pressure extreme value does not exceed 0.03%.The partial pressure distribution of the medium-pressure pipeline adopts simple one-dimensional calculation,and the other partial pressure distribution adopts a multi-dimensional calculation method combined with three-dimensional calculation,which saves calculation time and improves calculation efficiency.4)Build a multi-dimensional calculation method for the calculation of the pressure distribution of the runner in the transient process of the hydropower station,and compare the result with the single-dimensional calculation result.The multidimensional calculation method has the advantages of shorter calculation time,higher calculation efficiency and higher calculation accuracy.