| 摘要 |
PROBLEM TO BE SOLVED: To provide a water jet propelling device capable of preventing the occurrence of cavitation and providing a strong propelling force. SOLUTION: The axial flow impeller 7 of a closed type is provided in the front state of a suction casing 5, a helical oblique flow impeller 8 is provided in its rear stage, and the axial flow impeller 7 of the front stage is lifted lower than the helical oblique flow impeller 8. The axial flow impeller 7 of the front stage is brought close to the suction port of the helical oblique impeller 8 of the rear stage to set large the flowing-in elevation angle of fluids flowing into the oblique flow impeller 8, the axial flow impeller 7 of the front stage serves as an inducer for the rear stage oblique flow impeller 8 lifted higher to increase the circumferential speed of the impeller 8 against water, and thus even if the highly lifted impeller is used in the rear stage, no cavitation occurs. In addition, since the water flow of the front stage axial flow impeller 7 is corrected by the rear stage oblique flow impeller 8, a fixed guiding impeller 9 provided in a discharge casing 10 is shortened, and the length of a water jet propelling device is also shortened. |
