Focused on a 1000 MW huge-capacity hydraulic turbine unit

this paper conducted three-dimensional steady internal flow numerical simulation using commercial code ANSYS. The impact of uneven clearance distribution on its internal flow characteristics of the turbine under the design operating point was investigated

considering radial installation deviations of 0.1 mm

0.3 mm

0.5 mm

1.5 mm

and 2.5 mm on the negative y-direction. The results revealed that within a certain range of deviation

the pressure in the corresponding region gradually rises with the decrease in clearance. However

once the deviation exceeded a certain threshold

water was unable to flow in

thus resulting in the formation of a low-pressure area. Furthermore

both the upper crown chamber and the bottom ring chamber exhibited an equal number of vortex evolving cycles with different vortex intensity

and the vortex was more intense in the upper crown chamber; The number of vortices is not an integer multiple of the blade number. Finally

we clarify that the vortex flow impact was greater on the inner wall of the bottom ring chamber than that of the upper crown chamber. This study is applicable to the design and installation of other large or medium size Francis turbines for improving their operational quality

reducing operating costs

and enhancing the overall efficiency of hydropower plants.