PURPOSE: To surely reduce water thrust in the axial direction in all operating conditions by forming an intermediate seal provided on the back of the crown of a high pressure stage part smaller than the radial position of respective inner circumferential seals respectively formed on high and low pressure stage parts.
CONSTITUTION: An inner circumferential seal 29 is provided on the outlet side of the band part of a high pressure stage part runner 2, and an intermediate seal 24 is provided on the back of a crown. A runner back pressure chamber is separated into an outside back pressure chamber 6 and an inside back pressure chamber 4, and a water pressure balance tube 27 to communicate the inside back pressure chamber 4 and a draft tube 17 to each other is provided. An inner circumferential seal 28 is provided on the outlet side of the band part of a low pressure stage part runner 3, and the respective inner circumferential seals 29, 28 of the high pressure stage part and the low pressure stage part are formed on the same radial position. The intermediate seal 24 providing on the back of the crown of the high pressure stage part is formed on the radial position smaller than the radial position of the inner circumferential seals 29, 28, namely inside them. Hereby, water thrust in the axial direction as the whole pumpturbine can be balanced.
SHIRAKI KIYOTAKA
UMEDA SADAICHI
YAMAGATA ICHIRO
TOSHIBA CORP