Ships – Ice breakers
Patent
1984-01-23
1985-10-01
Barefoot, Galen L.
Ships
Ice breakers
114 67A, 417198, B63B 138
Patent
active
045439001
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates generally to improvements in jet pumps and shipboard ice lubrication systems utilizing such pumps for facilitating the movement of a ship through ice laden water.
BACKGROUND OF THE INVENTION
The presence of ice in navigable waters impedes the progress of ships therethrough because of, among other things, friction created by the hull of a ship rubbing against large pieces of ice. A variety of ice lubrication systems for reducing such friction have been proposed. For example, U.S. Pat. No. 3,665,886 describes means for discharging heated water from above the water line of the ship to melt ice proximate thereto, and U.S. Pat. Nos. 3,580,204 and 4,029,035 describe pump and pipe arrangements designed to blow compressed air or other gases through openings in a ship's hull below the waterline. The gas so discharged rises alongside the hull, creating a ridge of gas and water between the hull and the ice. Such prior art devices typically require means for compressing the gases and/or heating the water utilized by the system.
SUMMARY OF THE INVENTION
The present invention is directed to an improved ice lubrication system for a ship for facilitating its passage through ice strewn water and to an improved jet pump suitable for use in such an ice lubrication system.
In accordance with one aspect of the present invention, an improved jet pump is provided which efficiently utilizes a liquid flow, e.g. water, to entrain a gas, e.g. air, to discharge a mixture having a relatively high gas/liquid ratio. In accordance with the invention, a vortex generating means is incorporated in the jet pump inlet to impart a controlled rotational motion to the surface of the liquid stream flowing into the jet pump suction chamber. The liquid stream, exiting at a high velocity from the inlet nozzle, lowers the pressure in the suction chamber to draw gas from a supply source coupled thereto. The surface turbulence of the stream increases the ability of the liquid to capture and transport the gas while also reducing the back pressure on the stream.
In accordance with a different aspect of the present invention, an improved shipboard ice lubrication system is provided including means for discharging a liquid/gas mixture through openings in the ship's hull, preferably located below the waterline, to wet the hull/fractured ice interface to reduce friction therebetween and thus facilitate movement of the ship through ice laden waters.
In a preferred embodiment of the shipboard ice lubrication system, a plurality of jet pumps are provided, each having its discharge port mounted adjacent to a different opening in the ship's hull. The jet pumps are supplied by a pressurized water source and an air source. The pressurized water source includes a liquid manifold which is supplied by a water pump drawing water from the sea.
In accordance with one feature of the preferred embodiment, the vortex generating means in each jet pump comprises a plurality of vanes oriented around the inner periphery of the inlet nozzle to rotate the surface of the liquid stream passing therethrough while permitting waterborne debris and ice to move through the nozzle's central axial region without clogging.
In accordance with another feature of the invention, the air drawn by the jet pump suction ports can be comprised of exhaust gases produced by the ship's machinery, such as the primary or auxiliary engines.
In accordance with a further feature of the preferred embodiment, the suction chamber of each jet pump is coupled to a manifold having an air entrance opening adjacent the ship's hull above the waterline and a valve is provided to enable the water stream exiting from the jet pump inlet nozzle to be discharged through the air entrance opening to facilitate snow removal from floating ice blocks.
In accordance with a still further feature of the preferred embodiment, the aforementioned ice lubrication system is associated with a directional thruster system enabling the same water pump to supply water to both systems.
REFERENCES:
patent: 2764954 (1956-10-01), Oeltgen
patent: 2954750 (1960-10-01), Crump et al.
patent: 3273333 (1966-09-01), Roulund
patent: 4029035 (1977-06-01), German
Schutte & Koerting Co., Bulletin #4-P, Jet Catalog, pp. 4401-4416, Aug. 1934.
Barefoot Galen L.
Omnithruster Inc.
Swinehart Edwin L.
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