Marine propulsion – Jet drive – Having means to increase fluid drive means efficiency
Patent
1995-06-08
1997-06-03
Avila, Stephen
Marine propulsion
Jet drive
Having means to increase fluid drive means efficiency
B63H 11103
Patent
active
056348312
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a water jet propulsion unit primarily for use in jet boats but able to be used in other water craft.
BACKGROUND ART
Water jet propulsion units are of two main kinds, a mixed flow and an axial flow configuration. A mixed flow unit is one in which the water enters the impeller parallel to the shaft and is directed radially from the shaft and leaves the impeller with radial and axial velocity. An axial flow unit is one where the water enters the impeller parallel to the shaft and also leaves the impeller parallel to the shaft. The differences are more fully explained in the publication "Jet Boating", November 1986, Volume 6, No. 8, page 46.
An example of an axial flow unit may be seen in New Zealand Patent Specification 123,228 where there is described a motor with two impellers, that is a two stage motor having a set of stators between the two impellers and another set of stators in the rear nozzle of the jet unit.
In DE 3942672 A1 there is described a mixed flow water jet propulsion unit. In the embodiments described there are two or three impellers in the pump section whose casing diverges from a narrower cross-sectional area at the inlet to a maximum cross-sectional area at the middle and converges to the minimum cross-sectional area at the outlet. The impellers are counter-rotating with respect to each other.
The provision of counter-rotating propellers mounted on concentric shafts is well known from the prior art, for example in U.S. Pat. Nos. 4,642,059; 4,832,570; 5,030,149; 5,087,230 and in WO 93/01085. It is desirable to use a concentric configuration in jet propulsion units so as to minimize obstructions causing turbulent flow within the pump casing and also to achieve maximum reliability under the extreme conditions encountered in a water jet propulsion unit.
It is an object of this invention to go some way towards achieving these desiderata or at least to offer the public a useful choice.
DISCLOSURE OF THE INVENTION
Accordingly the invention may be said broadly to consist in a water jet propulsion jet comprising: downstream impeller being configured and calibrated to convert any radial flow created by the upstream impeller into axial flow, said counter-rotating impellers being each mounted on separate counter-rotating drive shafts, said drive shafts extending forwardly from said pump section through said intake section; or more hydro-dynamic vanes, said counter-rotating shafts being bearingly mounted in said mounting means; section; and 0.55 to less than the swept area of the forward of said impellers.
Preferably the outlet cross-sectional area of said nozzle can be adjusted.
This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.
The invention consists in the foregoing and also envisages constructions of which the following gives examples.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side sectional elevation of a first embodiment of an axial flow pump to be driven by a motor mounted forward of the propulsion unit.
FIG. 2 is a side sectional elevation of a second embodiment axial flow pump to be driven by a motor which is mounted on the outside of the housing of the intake section of a propulsion unit.
FIG. 3 is a side sectional elevation of a first embodiment of a mixed flow pump in which the motor is also mounted on the housing of the intake seciton of the jet propulsion unit.
FIG. 4 is a side sectional elevation of the rear portion of the intake section, the pump section and the nozzle section of the embodiment of FIG. 1 showing a first embodiment of a nozzle throttle.
FIG. 5 is a rear perspective view of the nozzle throttle of
REFERENCES:
patent: 3269111 (1966-08-01), Brill
patent: 3561392 (1971-02-01), Baez
patent: 3967573 (1976-07-01), Charles et al.
patent: 4642059 (1987-02-01), Noharah
patent: 4832570 (1989-05-01), Solia
patent: 5030149 (1991-07-01), Fujitat
patent: 5087230 (1992-02-01), Yates et al.
"Ian Andrews Tests A Berkeley Jet Unit", Jet Boating, 1986, vol. 6, No. 8, pp. 45-47, at p. 46.
Mechanics of Fluids, Sec. Edition Si Units, by A.C. Walshaw and D.A. Jobson, Publishers Longman Group, London, pp. 156-158.
Davies Barry J.
Davies Richard G.
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