Marine propulsion – Jet drive
Reexamination Certificate
2001-03-15
2003-10-07
Swinehart, Ed (Department: 3617)
Marine propulsion
Jet drive
C440S041000, C440S043000
Reexamination Certificate
active
06629866
ABSTRACT:
BACKGROUND OF THE INVENTION
The instant invention falls in the field of marine propulsion systems that utilize enclosed powered rotors that accelerate water or fluids taken from external to a marine vehicle to thereby generate a propelling thrust. They are commonly known as waterjet propulsors. In commercially available state-of-the-art waterjet propulsors a powered rotor or impeller builds up a pressure in water forward of a discharge nozzle that discharges to atmosphere. The differential pressure across the discharge nozzle results in a jet velocity that, when discounted for incoming water picked up at marine vehicle velocity and multiplied by the mass flow of water, gives the resulting thrust.
Several shortcomings of the present day waterjets are evident: 1) Since they have impellers that are basically simple water pressurizing pump impellers, they have a serious falloff in performance when air is ingested as is the case when operating in rough seas and/or when propelling air cushioned marine vehicles, 2) They are subject to impeller blade cavitation damage especially when running at high power levels at low marine vehicle speeds, 3) Their efficiencies at low marine vehicle speeds is generally considered to be poor with speeds of 35 knots or more considered necessary for optimum performance, 4) Their performance at very high marine vehicle speeds, say over 55 knots or so, is also poor due mainly to low efficiency of and high drag of their water inlets at the higher speeds, and 5) In multiple unit installations, drag of a non-operating waterjet is of a high magnitude due to water passing through the non-operating waterjet. In spite of all of their drawbacks, present day waterjets are seeing a lot of applications. These are primarily in craft that cruise mostly in the 35-50 knot area such as high speed ferries where their advantages of low maintenance and even engine loadings compared to open water propellers is valuable. They are also seeing application in small jetboats and personal watercraft where the loss of efficiency compared to the open water propeller is accepted for the added safety considerations of the enclosed rotor.
Presented here are some new concepts in a waterjet propulsor that solve all of the present-day waterjets just mentioned shortcomings. They are mainly improvements on a newer variation of a waterjet propulsor that uses a rotor that is supplied with gas over part of its rotation during it primary mode of operation. The basic ideas of this new type of propulsion system are given in Applicant's earlier U.S. Pat. Nos. 5,505,639, 5,730,636, and 6,024,614.
The instant invention waterjet propulsor not only supplies gas to its fluid-accelerating rotor during forward high speed propelling of a marine vehicle but also has a simple way to prevent gas from reaching the rotor when operating at low speed or during reversing. Preventing gas from reaching the rotor during low speed operation insures that the mass flow is about doubled which enhances thrust at low marine vehicle speeds. Also, it is particularly important to be able to prevent gas from reaching the rotor during reversing. This is because when the rotor is trying to build up pressure to impact a reversing bucket it tends to spin freely in a gas pocket if gas is entrained in the water. Little reversing thrust is generated in such a case. Lastly, an adjustable inlet fluid device can direct inlet water away from its water inlet to reduce drag of a non-operating unit.
SUMMARY OF THE INVENTION
With the foregoing in mind, it is a principal object of present invention to provide a new enclosed fluid accelerating rotor marine vehicle propulsion system that has an enclosed fluid accelerating rotor that is capable of operating efficiently when either partially or fully submerged in water.
It is a further related object of the invention that its inlet be a ram fluid inlet, as seen in vertical transverse planes of the improved waterjet propulsor with a rotational centerline of the fluid accelerating rotor horizontal, to thereby be, as a sum of its parts, a ram fluid inlet over a majority of 180 degrees of an arc.
It is yet another object of the invention that said ram fluid inlet be, at least in its majority, disposed above a lower portion of the marine vehicle forward of the ram fluid inlet.
Another object of the invention is that an adjustable inlet fluid directing means be disposed, at least in its majority, forward of said ram fluid inlet.
A further object of the invention is that it include a gas supply means that is capable of supplying gas to a forward portion of the fluid-accelerating rotor.
It is another object of the invention that the ram fluid inlet, on average, angles rearward from its upper to lower portions.
It is a further directly related object of the invention that the ram fluid inlet, on average, angle rearward from its upper to its lower portions at an angle of less than 60 degrees to a transverse horizontal plane of the improved waterjet propulsor when a rotational centerline of said fluid accelerating rotor is horizontal.
It is yet another directly related object of the invention that the ram fluid inlet, on average, angles rearward from its upper to its lower portions at an angle of less than 50 degrees to a transverse horizontal plane of the improved waterjet propulsor when a rotational centerline of said fluid accelerating rotor is horizontal.
A further directly related object of the invention is that the ram fluid inlet, on average, can angle rearward from its upper to its lower portions at an angle of less than 40 degrees to a transverse horizontal plane of the improved waterjet propulsor when a rotational centerline of said fluid accelerating rotor is horizontal.
Yet another object of the invention is that an inlet lip of said ram fluid inlet can be, at least in part, angled downward by an angle of less than twenty degrees to a transverse horizontal plane of the improved waterjet propulsor when a rotational centerline of said fluid accelerating rotor is horizontal.
A further refinement of the just mentioned object of the instant invention is that an inlet lip of said ram fluid inlet can be, at least in part, angled downward by an angle of less than fifteen degrees to a transverse horizontal plane of the improved waterjet propulsor when a rotational centerline of said fluid accelerating rotor is horizontal.
Yet another refinement to the just mentioned objects of the instant invention is that an inlet lip of said ram fluid inlet is, at least in part, angled downward by an angle of less than ten degrees to a transverse horizontal plane of the improved waterjet propulsor when a rotational centerline of said fluid accelerating rotor is horizontal.
It is still a further object of the invention that said ram fluid inlet is, at least in its majority, disposed below a rotational centerline of the fluid-accelerating rotor.
Another related object of the instant invention is that the ram fluid inlet is, at least in its majority, curvilinear in shape.
Yet another object of the invention is that an adjustable inlet fluid directing means can, when the marine is vehicle moving forward, direct a majority of incoming water away from impacting the ram fluid inlet.
A further object of the invention is that, when the marine vehicle is moving forward, an adjustable inlet fluid directing means can direct a majority of incoming water to the ram fluid inlet.
A related object of the instant invention is that the adjustable inlet fluid directing means can direct incoming water to at least a majority of an inlet of said fluid accelerating rotor.
It is a further object of the invention that the adjustable inlet fluid directing means can be composed of two or more fluid directing elements wherein said fluid directing elements are moveable in relation to the improved waterjet propulsor.
It is another object of the instant invention that movement of at least one of the fluid level directing elements is accomplished by forces supplied by an actuator.
It is a further object of the invention that one of said inlet
Swinehart Ed
Van Der Wall Robert J.
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