1998-02-23
2000-05-23
Swinehart, Ed
Marine propulsion
Jet drive
B63B 3558
Patent
active
060660112
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a thruster for use in fluids and particularly relates to a marine thruster used to propel water vehicles.
BACKGROUND ART
Fluid thrusters for use in marine applications conventionally comprise external propellers, or jet propulsion where water passes into an internal impeller. External propellers are well-known, have a number of problems including efficiency, and problems with wake.
Impellers, such as used in jet boats, consist of an internal flow tube having a forward inlet through which water passes. The impeller rotates at high speed in the flow tube and propels the water through the flow tube and to the outlet. An advantage of the jet propulsion thrusters is that there is little likelihood of propeller damage in shallow water.
OBJECT OF THE INVENTION
It is an object of the invention to provide a thruster such as marine thruster comprising an internal impeller where the impeller does not directly contact and accelerate incoming fluid. In one form, the invention resides in a thruster comprising a forward fluid inlet, a rear fluid outlet and an internal fluid passageway through which fluid flows and is accelerated, a curved body positioned between the fluid inlet and fluid outlet and about which fluid can circulate, the curved body having a forward portion adjacent the forward fluid inlet and which is dimensioned to provide a lower pressure surface to the fluid circulating about the curved body, a rear portion adjacent the rear fluid outlet and which is dimensioned to provide a higher pressure surface to the fluid circulating about the curved body, an outer portion between the forward portion and the rear portion and which is in fluid communication with the fluid passageway, an inner portion, and fluid acceleration means to accelerate the fluid about the curved body.
Thus, the thruster has a fluid acceleration means which accelerates fluid about the curved body, and the fluid recirculating around the curved body causes acceleration of incoming fluid passing through the forward fluid inlet.
The curved body may be in the form of a doughnut or toroid. The curved body need not be totally symmetrical and may be slightly elliptical in cross-section. The curved body need not be entirely curved in two directions and portions of the curved body may be straight if desired. If the curved body is in the form of a doughnut or toroid, a central passage is formed. Fluid passing through the central passage in the curved body and over the forward portion will exhibit a reduction in pressure as it passes over the forward portion which is a surface of increasing surface area, and which can also be seen as a lower pressure surface. As the fluid passes over this area, along the outer portion and back into the central portion, it passes over the rear portion which has a surface of decreasing surface area thereby fluid passing along it will undergo an increase in pressure, and therefore this portion can be seen as a higher pressure surface relative to the forward portion.
If the curved body is toroidal or doughnut shaped, and therefore has an annular-type appearance, it is preferred that the forward fluid inlet is also annular such that fluid can pass over all parts of the curved body. Similarly, it is preferred that the rear fluid outlet is annular which may improve the efficiency of the thruster.
In order to further improve the efficiency of the thruster, a tapering rear after portion may be positioned behind the rear fluid outlet such that fluid existing from the outlet passes over and exerts pressure on the tapered after portion.
The curved body can be positioned in the thruster between the forward fluid inlet and the rear fluid outlet in such a manner that the outer portion only and possibly some of the forward and rear portions contact incoming fluid while the inner portion contacts only recirculating fluid.
The fluid acceleration means may be positioned within the central passage formed by the toroid or doughnut shaped curved body. The fluid acceleration means can comprise
REFERENCES:
patent: 3047208 (1962-07-01), Coanda
patent: 3566823 (1971-03-01), Hope-Gill
patent: 5074759 (1991-12-01), Cossairt
Jetfan Australia Pty. Ltd.
Swinehart Ed
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