Hydraulic Performance Optimization And Model Test Investigation For A Tubular Turbine With High Water Head

It is a good way to develop water resources with low head,high efficiency and low investment,for the tubular turbine.Com,pared with the low-head tubular turbine,the high-head tubular turbine has the characteristics of large variation range of water head,violent gradient change of internal pressure,velocity and other parameters,which induces poor operation stability and presents more difficult to carried out the hydraulic development.Based on the specific hydropower station project,this paper successively carried out the type selection,hydraulic development for hydraulic turbine and model test,and provides a feasible technical solution for the investigated project.Firstly,the operating head range of investigated hydropower station varies from 9.4m to 23.36m,the bulb tubular type turbine with 5 runner blades was selected considering the factors of unit speed and unit discharge,the runner diameter,hydraulic efficiency,project investment,and so on.The number of units is three,of which two are large-capacity and the rest is small.The suction height for the large and small capacity units is-5.8m and-3.8m respectively.Secondly,this paper carried out the hydraulic design of runner according to the technical characteristics towards the tubular turbine.It is necessary to keep the curvature change of blade trailing edge as smooth as possible,and adjust the matching relation between the placement angle of blade leading edge and the twist angle,all of which are conducive to depress the occurrences of flow separation and cavitation.The results of design and calculation show that the pressure of the runner blade changes uniformly,but one can observer low pressure region which could induce cavitation flowing.Furthermore,the runner was optimized by the method of parametric spline surface,the efficiency of the runner was increased by 0.7%at the best efficiency point,and the pressure load of the runner blade and the inflow condition of the leading edge also were improved.Finally,the model test including energy,cavitation performance,pressure fluctuation and runner runaway experiments was conducted on the model test rig.The experimental results show that the investigated bulb tubular type turbine could operate in a region with broad high efficiency,the hydraulic efficiency at best efficiency point was 95.14%for the prototype turbine,and the corresponding model efficiency is 93.83%.Within the range of main operating water head,the the critical cavitation allowances were greater than 1.23,the pre ssure pulsatio n amplitudes of ?H/H%were always less than 3%.In addition,the maximum runaway rotating speed was less than the guaranteed value.All of the experimental obtains suggested that the designed tubular turbine operates well with excellent performance,and the technical parameters could meet the project requirements.