Study Of Different Types Of Francis Turbine Runner Cone On The Pressure Pulsation

Hydraulic turbine is the core equipment of hydroelectric generating units.With the improvement of modern hydropower unit generating capacity,increasing of the dimensions of a turbine,the vibration and stability problem of hydropower generating unit is becoming more and more prominent.At present there is no effective technical measure to the stability of large hydro turbine at home and abroad.The stability of hydraulic turbine is more complex,many factors can influence it,among which the low frequency pressure fluctuation caused by the vortex of the draft tube is the most important one.This paper studies the effects of different types of draft tube cone to pressure fluctuation by adopting the Xiangjiaba power station turbine model as the research object,with numerical calculation and model turbine test.Firstly this paper gives a brief description of the current status and progress home and abroad of the turbine test and CFD numerical simulations for turbine pressure pulsation problem research.Following the computational fluid dynamics control equations and turbulence in the numerical simulation is introduced,especially the discussion of the RANS model and the related basic principle is discussed,and a brief introduction to the solving strategies for the wall function and CFX software is shown.Then,a transient numerical simulation was carried out to the full turbine flow channel with computational fluid dynamics software.For two kinds of runner cone,we mainly focused on pressure trends over time at different test points of draft tube,also analyzed the pressure signal spectrum of different test points.The effects to the pressure pulsation of draft tube the was assessed by comparing the vortex shape,the pressure pulsation amplitude and frequency characteristics in draft tube with two runner cones.Finally,thisis paper introduces the basic parameters of hydraulic test stand.The influence of five different types of draft tube cone to pressure fluctuation was studied by the model hydraulic turbine test.Through the draft tube pressure pulsation amplitude analysis and draft tube outlet vortex flow view observation of different position,the variation of draft tube pressure fluctuation and vortex caused by different cone was acquired,which lays research foundation to further understanding of the relationship between pressure fluctuation intensity and cone type at different operation condition.