Hydraulic axial forces acting on a Francis runner

F 1 = Force from ring area F 2 = Reaction force from the absolute velocity at the inlet. F 3 = Force due to the outlet pressure F 4 = Reaction force from the absolute velocity at the outlet. F 5 = Force due to the pressure between the top cover and the impeller hub at the low pressure side of the labyrinth sealing. F 6 =Force due to the pressure between the top cover and the impeller hub at the high pressure side of the labyrinth sealing. F 7 =Force due to the pressure between the lower cover and the impeller ring at the high pressure side of the labyrinth sealing F 8 =Force due to the pressure at the upper labyrinth sealing F 9 =Force due to the pressure at the lower labyrinth sealing Hydraulic axial forces acting on a Francis runner

Force from ring area, F 1

Reaction force from the absolute velocity at the inlet, F 2

Force due to the outlet pressure, F 3

Reaction force from the absolute velocity at the outlet, F 4

Force due to the pressure between the top cover and the impeller hub at the low pressure side of the labyrinth sealing, F 5. where: h p = pressure of the cooling water for the generator  25 meter water colomn h p will have another pressure if the water is not used for cooling. k = 0,50 – 0,55 r p = D p /2 r i = D r /2

Force due to the pressure between the top cover and the impeller hub at the high pressure side of the labyrinth sealing, F 6.

Force due to the pressure between the lower cover and the impeller ring at the high pressure side of the labyrinth sealing, F 7.

Force due to the pressure at the upper labyrinth sealing. F 8. where the pressure at the high pressure side of the labyrinth sealing is:

Force due to the pressure at the lower labyrinth sealing. F 9. where the pressure the high pressure side of the labyrinth sealing is: and h s = pressure head at the draft tube inlet