混流式水轮机轴向水推力研究综述和讨论

Overview and discussion on hydraulic axial thrust in Francis turbine research

混流式水轮机稳定性的好坏直接关系到机组能否正常运行,其影响因素主要可分为水力稳定性和非水力稳定性,而前者是研究的热点问题。作为水力稳定性影响因素之一的轴向水推力是水流作用在转轮轴向上的力,通过推力轴承传递到厂房承重机架基础上,会影响轴承和厂房的安全运行。本文归纳分析了已建成水电站中由于轴向水推力异常导致的主要事故案例,从理论公式、试验测量和数值计算3个方面总结了轴向水推力计算的研究进展;系统讨论了多种水力激振力作用下轴向水推力的脉动特性,有利于提高对厂房的结构振动特性的认识;综合对比了减轻轴向水推力的各种措施及其特点,强调了对推力轴承的运行状态进行分析的重要性;最后展望了轴向水推力研究的发展趋势。本文可为继续深入研究涉及轴向水推力的相关工程设计、安全运行等问题提供参考。

The stability of Francis turbine is of importance to the safe and reliable operation of unit,which is mainly comprised of hydraulic stability and non-hydraulic one;while the former has become a major concern in engineering community. Being one of the crucial factors in hydraulic stability,the hydraulic axial thrust is the resultant force in the axial direction of turbine runner exerted by the flow in the turbine passage,which is then transmitted to the load-bearing frame base via thrust bearing,and consequently poses a threat to the bearing and powerhouse. After carrying out an extensive literature survey, major accidents brought about by abnormal hydraulic axial thrust is analyzed. Subsequently,analytical formula,experimental measurement and numerical simulation regarding the calculation of hydraulic axial thrust are discussed. Moreover,on the basis of aforementioned investigation,the systematic exploration into the pulsating property of hydraulic axial thrust under the impact of multiple hydraulic excitation forces,contributes significantly to the analysis of structural vibration of hydropower plant. In addition,various measures for alleviating the axial thrust are compared. Additionally,the significance of diagnosing the operating status of thrust bearing is pointed out. Finally,the prospect of research into hydraulic axial thrust is presented. This paper is expected to provide reference for issues associated with hydraulic axial thrust in the process of relavant engineering design and safe operational planning.