| 摘要 |
An improved inlet duct for a marine jet propulsion system is disclosed designed to allow the overall system to operate more efficiently. The inlet duct includes a hydraulically efficient inlet tunnel with a forward entrance opening integrally formed on the bottom of the hull of the watercraft, and a rear exit opening formed inside the hull of the watercraft adjacent to the pump. The inlet tunnel is longitudinally aligned and gently curves upward inside said hull following streamlines of generation and has cross-sectional area that progressively increases from the fore to the aft positions therein. Disposed over the front entrance opening of the inlet tunnel is an articulating structure designed to adjust its size according to the difference in hydraulic conditions that exist inside the inlet tunnel and the outside of the hull so that the velocity of the incoming water matches the velocity of the watercraft in the body of water. By using the improved inlet duct, the total dynamic head of the incoming water can be recovered by the pump which is especially desirable when the combination of a large pump and a large, adjustable discharge nozzle are used which can handle a greater flow of water and maintain efficient hydraulic conditions on the pump. |
