大型混流式水机全流道涡系激振轴系耦合响应研究

Taking the vibration of the unit shafting urged by the vortices change in as study objects the entire flow passage of Large-scale Francis turbine, Leaf turbulent channel flow control equation is established based on LES-IBM method, simulate the tandem cascade flow formed by the oscillation and unsteady flow and the growth of Kaman vortex, interblade vortices and vortex strip in the draft tube what were urged by the tandem cascade flow. The FEM and LES methods were used to simulate the change process of the vortices urged reciprocally by multifarious swirls in the entire flow passage. The vibration system of the principal axis that is multiple degrees of freedom consist axial vibration, radial bend vibration and tangential torsion vibration restricted by the four bearings( upper guide bearing, lower guide bearing, water guide bearing and thrust block bearing). Establish analytical model of vibration equation for the every system and confirm the system steady-state response and complex frequency response caused by the harmonic excitation. Based on ALE, simulate by FEM on the vortices and the shafting, constitute numerical algorithm appropriate to the calculation model, study the prompting effect produced when the pressure pulsation caused by the vortex change in the entire flow passage coupled with the unit shafting. What's more, approach the feedback produced by the vibration of the axis system caused to the instability of water flow. Then show up the vibratory response mechanism and rule of the shafting vibration urged by the vortices in the entire flow passage of Large-scale Francis turbine, and obtain the information by PIV measurement and sensor measurement related to flow, vibration, and so on. And thereby test out and improve numerical calculation.

以大型混流式水机全流道涡系变迁诱发机组轴系振动为研究对象，基于LES-IBM法建立叶道湍流控制方程，模拟振荡、非定常湍流所形成的双列叶栅绕流并由此激励卡门涡、叶道涡、尾水涡带全流道涡系生长。混用FEM、LES法模拟各旋涡相互激励下的全流道涡系的变迁过程。组成由四个轴承(上导、下导、水导、推力)约束的轴向振动、径向弯曲振动及切向扭转振动三方向多自由度的主轴振动系统。建立各系统的振动方程解析模型，确定系统受简谐激励的稳态响应和复频率响应。研究全流道涡系变迁所引发的压力脉动在与机组轴系的耦合中所产生的激励作用，基于ALE对涡系及轴系进行紧耦合模型FEM数值模拟，建立与计算模型相适应的数值算法，探讨主轴轴系的振动对流体流动不稳定性所产生的反馈影响，从而阐明大型混流式水轮机全流道涡系涡激机组主轴系统振动响应机理和规律。并通过PIV流场测量和传感器技术测量获取流动、振动等相关信息，检验及完善数值计算。

大型混流式水机全流道涡系激振轴系耦合响应研究项目于2013年1月立项。立项考虑是基于混流式水轮机长期以来一直存在压力脉动和水力激振所形成不稳定问题，阐明大型混流式水轮机全流道涡系涡激机组主轴系统振动响应机理和规律是该领域关注及研究的重点。.研究以混流式水机全流道涡系变迁诱发机组轴系振动为研究对象，对水机导叶双列叶栅卡门涡列、转轮叶片叶道涡及尾水管涡带形成的涡系相互影响、相互作用进行全流场模拟。研究全流场涡系变迁形成的组合激振力及对机组主轴系统激振的综合作用。根据水轮机耦合试验系统上的水轮机木模图划分全流道区域网格，生成全流道网格数值模型。完成对水轮机叶片的三维建模，并完成划分各流道区域的网格，研究网格数量对CFD模拟精度的影响，用进出口压差作为对比参数，用倍增网格数的方法，对比不同网格密度对压差的影响，找到适合计算的最佳网格数。使壁面网格y+值满足模型准则要求。以表面摩擦系数理论计算值为参照，合理选择网格高度绘制边界层网格。生成了分析计算所需的高质量的网格。在涡系研究过程中对固定导叶双列叶栅的卡门涡进行动力学分析并对导叶进行燕尾修型研究，捕获固定导叶尾迹涡量场。对叶道涡基于欧拉描述法的混合流体无滑移模型，以空化模型，采用经过粘度修正的RNG 湍流模型和压力修正算法，对混流式水轮机转轮进行了定常空化湍流数值模拟。对尾水管弯肘部分采用新的投影建模。使尾水管内部流动状况清晰，获得更高的精度要求及尾水涡带。开展了尾水管导流栅形成的振动对轴系系统的影响研究。推导了压力脉动力与涡带偏心距之间的表达式。研究了导流栅、涡带偏心及机组激振之间的联系。在轴系激振研究中考虑到水轮发电机组轴向稳态响应和振动响应研究、主切向扭转稳态响应和振动响应研究、主轴弯曲稳态响应及振动方程。针对瓦斯继电器误动对轴系较强的激振影响做相关研究。建立了变压器振动监测系统并对机组进行了实测数据分析研究，该项目对轴系激振影响有着重要的意义。