尾水管流动不稳定性的实验研究

The draft tube of a hydraulic turbine is the component where the flow exiting the
runner is decelerated, thereby converting the excess of kinetic energy into static pressure.
However, in some refurbishment cases, the installation of an upgraded runner with an old drafttube
leads to an undesirable efficiency drop as the discharge is increased above the best
efficiency point value. It is found to be related to a corresponding sudden variation in the draft
tube pressure recovery coefficient at the same discharge. The model of a recent refurbishment
which presents this instability is installed in the CREMHyG test rig. Steady and unsteady
measurements of velocity and pressure fields of the complex and highly turbulent swir领 flow
exiting the runner have been carried out at CREMHyG (Grenoble). They included the three
components of the velocity. The flow in the draft tube is rich in secondary flows and possible
flow separation due to the elbow as well as to the divergent shape of this geometry. Pressure
and velocity field measurements in the draft-tube have been performed. They let us identify
some phenomena that may explain the origin of the unusual behavior of the draft tube. Finally,
the same model, with a modified draft tube geometry that was designed to reduce the efficiency
drop phenomenon has been installed. Velocity measurements were made to validate the benefit
of such geometry modification. 德国LaVision PIV/PLIF粒子成像测速场仪 Imager pro X PIV相机 用于粒子成像测速(PIV)的荧光示踪粒子