The Effects Of Runner Performance With Cut-off Runner Trailing Edges Based On CFD

The Tiewu hydroelectric power station located at Tongren County of Huangnan Tibetan Autonomous Prefecture within Qinghai Province, its 2# unit is the HL220-WJ-71 mixed-flow turbine.Because has operated for more than 20 years, unit equipments either in performance or structure already gone out of date,causes the accident to increase and the frequent overhaul.The long-term operation has caused the overflow components to be weared, especially the runner,guide vanes and so on, as a result of the cavitation erosion and the abrasion, the blade section are destructed, and produces the varying degree crack in the blade surface.Because the original generator has been changed from 1250KW to 1600KW,for the full use hydro energy and the generator capacity, the power station hopes to make the capacity-increasing improvement to the 2# unit runner during the diversion channel's renovation, and find out the reason of creating the crack on blade surfac,achieves to increase the capacity and increase the unit's life at the same time.This topic take the Tiewu hydroelectric power station's 2# unit as a prototype, which is HL220-WJ-71 hydraulic turbine,carries on each overflow components' three dimensional modelling of the hydraulic turbine entire flow channel, chooses the suited turbulent flow field model and algorithm used on hydraulic turbine through comparison;by the Cut-off Runner trailing Edges method, find out the rule of the external characteristic as well as the internal characteristic of the unit when several kind of computation operating modes and different cutting quantity based on CFD, according to the numerical simulation result to determine the runner trailing edges cutting quantity applied to the power station,makes the turbine output power be increased to 1337.8 KW but the unit efficiency did not decline much more;according to the flow field computation results, uses finite element analysis to research the runner's static strength and the runner's first eight step modal frequencies based on fluid-solid coupling, find that the Tiewu hydroelectric power station 2# turbine runner first-step frequency very close to the frequency caused by guide vanes outlet flow off, the Carmen vortex frequency and the runner's high step frequencies relatively close, have big hazardous nature,so the reason of causing the crack on runner blade surface is,the stability stress and vibration alternating stress causes micro cracks and crack extension. This method can provides beneficial references for the low design parameters standard turbines'capacity increases and longevity modification in old stations.