Power plants – Reaction motor – Method of operation
Reexamination Certificate
2002-08-12
2003-12-16
Gartenberg, Ehud (Department: 3746)
Power plants
Reaction motor
Method of operation
C060S221000
Reexamination Certificate
active
06662549
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a propulsion system.
The invention has been devised particularly, although not solely, as a propulsion system for propelling watercraft. In such an application, a propulsive force for the watercraft typically arises from generation of a jet of water which imparts thrust to the watercraft. However, the propulsion system may have other applications; for example, the propulsion system may be used to propel a stream of liquid in the manner of a pump. Such a use may have particular application in, for example, fire-fighting where a stream of water is propelled onto a fire.
BACKGROUND ART
Various systems are known for propelling watercraft, including motor-driven propellers, and jet propulsion units which produce thrust by discharge of a stream of fluid.
Jet propulsion units are becoming increasingly popular in pleasure and commercial craft because of their shallow draft capability and reduced maintenance requirements in comparison to conventional propeller propulsion system.
U.S. Pat. No. 3,402,555 (Piper) discloses a steam jet nozzle system for propelling watercraft. In the nozzle system, steam is generated and discharged under high pressure to provide propulsion. The nozzle system includes a nozzle having an entrance end and an exit end. Steam enters the nozzle through the entrance end. Raw water from the body of water through which the watercraft is to be propelled is introduced into the nozzle so as to be converted into steam to supplement the steam already in the nozzle. The propulsion is not provided by a jet stream of water but rather by generation and discharge of steam under high pressure.
A known water-jet propulsion unit for watercraft is produced by Hamilton Jet in New Zealand. A water-jet propulsion unit of this type utilises an engine-driven impeller to draw water through a suction foot opening onto the underside of the watercraft and to discharge the water under pressure through a discharge port and thereby propel the watercraft. The impeller is typically driven through a drive shaft from an internal combustion engine. The use of an impeller in a conventional water-jet propulsion system has several disadvantages, including cavitation and other efficiency limitations. Furthermore, there is a significant loss of heat energy from the internal combustion engine used to drive the impeller.
There have been various proposals directed to propulsion of watercraft using a stream of water driven by a high pressure fluid to provide thrust. The high pressure fluid imparts momentum to the water stream which discharges as a water jet. Typically, such proposals involve a duct providing a flow passage having an intake and an outlet, with both the intake and the outlet being open to the water through which the watercraft is to be propelled. The high pressure driving fluid is injected into the duct to contact water in the duct and thereby transfer momentum thereto, causing a stream of water to flow through the duct and discharge as a jet from the outlet to provide propulsive thrust. One such arrangement is disclosed in U.S. Pat. No. 5,344,345 (Nagata) wherein the driving fluid comprises pressurised water and compressed air. Another such arrangement is disclosed in U.S. Pat. No. 5,598,700 (Varshay) where the driving fluid comprises a compressed gas.
The present invention seeks to provide a propulsion system for generating a fluid stream utilising a driving fluid without relying solely on momentum transfer.
DISCLOSURE OF THE INVENTION
According to one aspect of the present invention there is provided a propulsion system comprising a flow passage having an intake for communicating with a source of working fluid and outlet, a mixing zone disposed within the flow passage between the intake and the outlet, means for introducing a hot compressible driving fluid into the mixing zone, whereby interaction between the driving fluid and the working fluid in the mixing zone develops a pressure reduction in the mixing zone to cause working fluid to be drawn from said source into the mixing zone and propelled towards the outlet, and means for aerating the working fluid with an aerating gas prior to interaction of the driving fluid in the mixing zone whereby a three-phase fluid regime is created in the mixing zone by virtue of the interaction of the aerating gas, the working fluid and the driving fluid.
The compressible driving fluid is hot in the sense that it is at a temperature greater than the temperature of the working fluid entering the mixing zone. Typically, the driving fluid is at a temperature of at least 50 C above the temperature of working fluid and preferably more than about 70 C above the temperature of the working fluid.
The interaction between the hot compressible driving fluid and the working fluid involves contact of driving fluid with the working fluid causing rapid cooling of the driving fluid to produce the pressure reduction in the mixing chamber. The rapid pressure reduction is in effect an implosion within the mixing zone. The feature of the driving fluid being compressible allows for a volumetric change upon rapid cooling of the driving fluid.
The interaction between the hot compressible driving fluid and the working fluid preferably also involves momentum transfer from the driving fluid to the working fluid.
It is believed that contact between the driving fluid and the working fluid at the mixing zone within the flow passage may also cause liberation of gases (and oxygen in particular) from the working fluid when the latter is a liquid, and in particular water. The liberated gases may assist in momentum transfer from the driving fluid to the working fluid. Furthermore bubbles of the liberated gases may expand upon being heated in the mixing zone and in doing so apply pressure, and thus work, to the working fluid so further assisting propulsion of the working fluid towards the outlet. Additionally the liberated gases may serve to reduce skin friction between the working fluid and the surrounding boundary of the flow passage.
As alluded to above, the working fluid may comprise water, and said source may comprise a body of water. In the case of a propulsion system for watercraft, the working fluid would comprise water drawn from a body of water in or on which the watercraft is accommodated. In such a case the body of water is typically a lake, a river, an estuary or the sea.
The compressible driving fluid may comprise a substantially gaseous fluid capable of rapid pressure reduction upon exposure to the cooling influence of the working liquid. The gaseous fluid may comprise a gas or a gaseous mixture. Further, the gaseous fluid may have particles such as liquid droplets entrained therein.
The driving fluid may, for example, comprise a condensable vapour such as steam, or exhaust gases from a combustion process such as in an internal combustion engine or a gas turbine.
Steam is a particularly suitable driving fluid, as it can be generated readily and efficiently. Furthermore, steam can be expanded easily and is capable of rapid volume reduction upon condensation to generate the necessary implosion effect.
Steam is a particularly appropriate form of driving fluid where the working fluid is water. In such a case, the source from which the water is drawn as the working fluid may also supply water from which the steam is generated. Additionally, because of the relationship between steam and liquid water, where steam is the evaporated phase of water, there is no undesirable contamination of the water used as the working fluid upon contact with steam used as the driving fluid. This can be important where the propulsion system is used for propelling watercraft through a body of water, as it avoids pollution of the body of water by the driving fluid.
The driving fluid can also be a multi-phase fluid, such as a mixture of steam, air and water droplets. The air and water droplets can be in the form of a mist. Such a multi-phase fluid provides the benefit of increasing the mass flow rate of the driving fluid. Additionally, it serves to incr
Gartenberg Ehud
Nixon & Vanderhye P.C.
Pursuit Dynamics plc
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