摘要
混流式水轮机在偏离设计工况特别是在部分负荷下运行时,转轮出口的旋流会在尾水管中产生螺旋状涡带,该涡带引起的压力脉动是引起水轮机水力不稳定的最主要原因。采用全流道非定常三维流场数值模拟来计算尾水管流场不仅对计算资源性能要求很高和耗时,而且很难在设计阶段快速计算出尾水管涡带诱导的流场,不利于在较宽运行工况范围预评估水力稳定性。本文在螺旋涡管诱导流场理论的基础上探索建立在部分负荷运行下尾水管中螺旋涡带的近似解析模型。采用该模型可以快速近似地计算出尾水管的流速,与国外相关的试验结果对比,验证了该模型的正确性。可以进一步研究将该模型用于混流式水轮机设计过程中的优化流道设计,以减轻尾水管涡带的影响和扩大运行工况范围。
When a Francis hydraulic turbine operates at off- design regimes and particular at partial discharge,the residual swirl downstream runner leads to flow instability of the turbine,with development of a heliacal vortex rope and associated large pressure fluctuations on the draft tube. It is not only notoriously difficult and expensive to be computed by using full 3D turbulent unsteady flow models,but also can not meet the requirement of robust,tractable and accurate prior assessment of the flow unsteadiness level with a wide operating range before actually knowing the detail runner geometry. We established a quasi- analytical model of the vortex rope in the discharge cone based on the theory of processing helical vortex tube in swirl flow. The axial and circumferential velocity profiles can be quickly calculated with this averaged velocities model,and were validated by comparing the numerical results with the experimental results presented in the references. It can be further applied to optimize the flow path design in order to reduce the vortex rope and expanding the operating range for a Francis turbine.
出处
《西华大学学报（自然科学版）》
CAS
2015年第5期24-33,共10页
Journal of Xihua University:Natural Science Edition
基金
国家自然科学基金项目(51379179)
关键词
涡带
尾水管
混流式水轮机
流场计算
vortex rope
draft tube
francis turbine
flow field analysis
