Dynamic Characteristic Study Of Francis Hydro Turbine Based On Numerical Analysis

With the increasing of the hydraulic turbine unit capacity, the unit size increases,and the stiffness is relatively weaker, which is a serious threat to the safe operation ofpower station. And the same time, due to the rapid development of technology,automation degree of unit operation is higher. So there are more remote controlhydropower plants without or less people on duty. Then the operation stability of unitis stricter. This article takes Francis turbine as example, using CFD numericalcalculation method, flow of turbine and the characteristics of flow field in differentoperation conditions are analyzed comprehensive. And based numerical calculation,the fluid-solid coupling of the runner is also calculated, the model of runner and thestress conditions of blades are mainly studied. Main contents are shown as following:（1）The numerical simulation methods and fluid dynamic models of flow field，structural static of runner, numerical simulation methods is analyzed. Withthree-dimensional modeling software, using the reverse engineering method of3D,the geometric model of the turbine is drawled. The computational domain grid modelis established by grid division software.（2）The whole flow field of hydraulic turbine are investigated with steady andunsteady numerical calculation by using software, Which contains detailed analysis ofthe internal flow characteristics of the turbine. And in the CFD based on thecalculation of wheel, the structure static calculation in coupling force field iscalculated, which analysis stress and strain of the runner blade in different loadingmethods. At the same time, the dynamic characteristics of the runner at differentrotation speeds are also calculated and analyzed. We got the effects of different speedon the maximum equivalent stress of runner blade: the maximum equivalent stress ofblade increases as the speed increases, the quantity change and speed increase asnon-linear. Stress variation tendency of runner is gentle in low speed range inside, itsvalue is smaller. As the speed increases, the stress and deformation changes rapidly.Comparing the effects of the runner, the maximum equivalent stress and themaximum deformation is mainly due to the centrifugal force of the larger.（3）Modal of runner is calculated in the air as well in coupling flow field androtary pre-stress in this paper. And it is found that the effect of modal in pre-stress andcoupled stress field is very small. By comparing the runner in different media under the natural frequency, no obvious rules was found; through the analysis of vibrationmode, which found that the frequency is low in the low order mode, the vibration inthe form of the overall vibration of runner, it is reflected the overall vibration andvibration, with vibration frequency to improve the vibration form, The evolution ofform vibration for the local vibration of runner.（4）The excitation force frequency of runner are analyzed. It is found a largedifference compared with the wheel vibration, there is the smaller possibility inrunner resonance.