| 摘要 |
An improved nozzle and method for operating a marine jet propulsion system are disclosed designed to allow the pump to operate more efficiently. The nozzle (60) includes an outer nozzle structure (62) which is mounted immediately downstream of the pump diffuser vanes (48). The outer nozzle (62) progressively reduces in diameter toward its rear exit opening (64). A needle structure (66) is mounted within the diffuser hub (49) and travels in axial alignment within the outer nozzle (62) to adjust the effective discharge area of the nozzle (60) according to a pump affinity relationship, so that the pump (40) is always operating at the most efficient head and flow for its current shaft rpm, regardless of boat speed or pressure recovery in the inlet duct (17). The disclosure also shows the incorporation of a through-the-jet exhaust system (176) in the pump and adjustable nozzle.
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