基于正交试验多目标的两叶片灯泡贯流式水轮机性能优化

Performance Optimization of Bulb Tubular Turbine With two Blades Based on Multi-objective Orthogonal Test

两叶片转轮适用于超低水头条件发电,并可弥补三、四、五叶片灯泡贯流式机组在超低水头条件下的缺陷,提高汛期发电量和电站低水头时运行稳定性。基于ANSYS CFX平台,采用正交试验法对某电站增容改造后的两叶片贯流式机组进行多目标结构优化。以叶片扭角、叶片安放角、轮毂比及导叶数4个设计参数作为影响水轮机的因素,探究其对机组出力、效率、压力脉动、叶片静应力和叶片变形这5个评判指标的影响规律。通过直观分析和极差分析结合的方法确定最优组合方案,并对优化前后的机组性能进行对比分析。通过研究发现:相对于其他3个设计参数,叶片扭角对水轮机性能影响最大。优化后,水轮机出力由3.13kW增加到4.11kW,增加31.3%;效率由87.63%提高到89.05%,提高1.42%。尾水管中段回流和漩涡消失,水流变得平顺,极大改善了流道内水流流态。

For a bulb tubular turbine,the two-blade runner can make up for the defects of three-blade,four-blade,and five-blade runners in ultra-low water head condition,and therefore improve the power generation in flood season and the operation stability of the power station in ultra-low head condition.Based on the ANSYS CFX platform,this paper adopted the orthogonal test method to optimize the two-blade tubular turbine unit’s multi-objective structure after the capacity increase in a power station.Four design parameters,blade twist angle,blade setting angle,hub ratio,and number of guide vane,were taken as the influencing factors of the turbine,and the influences on the five evaluation indexes of unit output,efficiency,pressure pulsation,blade static stress,and blade deformation were investigated.The optimal combination scheme was determined by visual analysis and range analysis,and the unit performance before and after optimization was compared and analyzed.It can be found that compared with the other three design parameters,blade twist angle has the most significant influence on turbine performance.After optimization,the turbine output increases from 3.13kW to 4.11kW,increasing by 31.3%,and the efficiency increased from 87.63%to 89.05%,increasing by 1.42%.The backflow and vortex disappear in the middle section of the draft tube,and the flow becomes smooth,dramatically improving the flow pattern in the flow passage.