| 摘要 |
A centrifugal pump has a casing (35) with an impeller cavity (48) in which a shrouded impeller (47) is mounted and with front and rear labyrinth seals (70-73) associated one with each of the front and rear shrouds (49, 50) of the impeller and located near the inner ends of the shrouds. An additional seal (76) is positioned inwardly of the rear labyrinth seal to substantially seal a space behind the innermost part of the rear shroud (50) and a pump structure (78, 79) is mounted on the impeller to the rear of the rear shroud for pumping fluid from the substantially sealed space to the entrance (55) of a volute surrounding the impeller. The impeller shaft has a front thrust bearing (80) coacting with a bearing surface (81), with fluid passing therebetween for lubrication and with the flow of the fluid being controlled to a minimal amount by a force imbalance on the impeller shaft created by location of the front and rear labyrinth seals (70-73) at different distances from the axis of rotation of the impeller (47) whereby pressure forces acting at the rear of the impeller urge the impeller shaft (45) in a forward direction. |
