Analysis The Influence Of Blade Number On Performance Of Hydraulic Based On CFD

Small turbine in small hydroelectric power station have a short blade opening,the runner can be easily chocked by floating objects. It is necessary to open draft tube and clean floating objects frequently,it is needed to stop all the unit when do inspection and repair work because butterfly valve is not closed completely and all units use the same diversion pipe or each tubine has one diversion but draft head is negative number, this can influence the economic benefit seriously, this subject use HL220-WJ-71 unit as reserch object,bring up a method that do capacity-increase improvement by reduce the number of blade. it have some science signification and much more practice engineering signification.This article select the product of Francis turbine HL220-WJ-71,and select four typical condition(limited condition, greater guide vane condition,optimum operating condition,low flow condition)to do computation.The standard k-εturbulence model and SIMPLE algorithm are applied by FLUENT6.3 in the computation.By analyse the computation results we can find that the change of blade number has a serious influence in suction side of blade, the cavitation of the improved runner caused by the low pressure part in suction side of blade improved when it works from low flow condition to limited condition and deteriorated when it works in large flow condition. When the turbine is working in optimum operating condition,water have a positive value circular rector in trailing edge,the circular rector of the improved runner in trailing edge is greater than before in the same conditon because the optimum operating condition has been moved to large flow condition,the circular rector in trailing edge of improved runner is smaller than primary when it's working in limited condition and large flow condition.There is a obvios vortex strip in draft tube cone when hydraulic tubine is working in low flow condition,and the vortex strip is weakened when it has been improved.Combining with Empirical formula and using the function of surface integral in the FLUENT, we calculate the change rule of efficiency and power with the change of guide vane opening of improved runner and the primary runner.The calculating result show that the efficiency of improved runner declines 2.6%, and the power of it increases 44.92kw when working in optimum operating condition,the efficiency of improved runner increases 0.27%, and the power of it increases 59.29kw when working in limited condition, the efficiency of improved runner increases 1.96% and the power of it increases 65.85 when working in larger flow condition. the efficiency of improved runner declines 1.04%, and the power of it declines 1.04kw when working in low flow condition.In addition, the numerical simulation result coincide with the production and examine and repair date of the hydroelectric power station. So it shows the calculate result is credibility and rightly.