中文摘要：

通过模型实验和基于整体流动模型的数值模拟研究了混流式水轮机进动过程中作用在转轮上冠的转动流体力矩的基本特性.模型实验中的转轮用一个圆盘来模拟,其上冠与后顶盖之间形成一个很小的轴向间隙.内向流由外部水泵供给.检验分析了间隙内泄漏流速、径向间隙进口处的预旋速度和轴向间隙宽度对流体力矩的影响.研究结果表明,进动流体力矩在很小的正向进动角速率比区间内对转轮的进动具有自激效应,并且进口处预旋速度对自激区间的影响显著.通过对转轮进动过程中流体所产生的转动力矩在转轮旋转和不旋转两种情况下的比较,得出了法向流体力矩在转轮只有进动没有旋转的情况下对转轮的进动没有自激效应.法向流体力矩对进动所产生的自激效应是由转轮转动所形成的漩涡流引起的.

英文摘要：

The fundamental characteristics of rotordynamic fluid force moment on the backshroud of Francis turbine runners in precession motion were studied by model experiments and the numerical simulation based on a bulk flow model.The runner is modeled by a disk set close to a casing with small radial clearance.An inward leakage flow is produced by an external pump.The effects of the leakage flow rate,the pre-swirl velocity at the inlet of the radial clearance,and the axial clearance on the fluid force moment were examined.It is found that the fluid force moment encourages the precession motion at small forward precession angular velocity ratios region and the region encouraging the precession motion is affected by the pre-swirl velocity.Through the comparisons of the fluid force moment acting on the backshroud under the precession motions with and without the rotation of the disk,it is found that the normal moment generated by the precession motion without the rotation of the disk has not the effect of encouraging the precession motion.The swirl flow due to the rotation of the disk is found to be responsible for the encouragement of normal moment on the precession motion.