混流式水轮机内部空化流动数值模拟

摘要

In order to study the influence of different proportion of long and short blades on internal flow field cavitation of Francis turbine,the numerical simulation of three dimensional constant cavitation turbulent flow in Francis hydro -turbine pas-sage was conducted by using the mixed two -phase non -slip model based on the assumption of uniform multiphase flow in the Euler -Euler approach,and also the RNG k ~εmodel and the Reynolds averaged Navier -Stokes equations were used.For dif-ferent Francis turbines with 3 proportions of long and short blades,the flow characteristics of cavitation phase under various cavi-tation coefficients and the graph of σ ~ηon each Francis hydro -turbine were obtained.The results show that the minimum of critical cavitation coefficient of turbine is 0.0608 at the Di /D2 of 0.47,and this data is reduced by 8.82% compared with that at the Di /D2 of 0.6.When the turbines have the same cavitation coefficient,the turbine with Di /D2 of 0.6 has the highest efficien-cy.The cavitation and the energy performance are improved greatly by the increase of the short blades.These conclusions have an important significance to the design,optimization and modification of Francis turbine with long and short blades.%为探究不同比例的长短叶片对混流式水轮机内部流场空化特性的影响，基于欧拉－欧拉方法中均匀多相流假设的混合两相流体无滑移模型，采用 RNG k ～ε湍流模型以及三维时均 N －S 方程，对各混流式水轮机进行全流道三维定常空化湍流计算，获得了3种不同比例长短叶片对应的混流式水轮机在各空化系数下空泡相的流动特征以及各水轮机对应的σ～η曲线图。计算结果表明，当长短叶片比例为0．47时，水轮机临界空化系数最小，为0．0608，相比长短叶片比例为0．6时降低了8．82％；当3种水轮机处于同一空化系数下时，该型水轮机效率最高；随着水轮机转轮短叶片的增多，水轮机的空化性能及能量性能得到了明显的提升。研究结果对长短叶片混流式水轮机的设计、优化和改型等具有一定的指导意义。