GB2419861A

GB2419861A - Shrouded vane marine propeller

Info

Publication number: GB2419861A
Application number: GB0525498A
Authority: GB
Inventors: Peter Woodford
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-11-09
Filing date: 2005-11-08
Publication date: 2006-05-10
Also published as: GB0424697D0; GB0525498D0

Abstract

A marine propeller comprises an outer cylindrical shroud 1 and a plurality of curved blades or vanes 2 mounted on the inside surface of the shroud such that there is no central hub. The blades extend towards the centre of the shroud and in the direction of a longitudinal axis of the shroud. The shroud minimises slippage of the propeller by being in contact with the outer edge of the blades, maximising fluid displacement input/output ratios per propeller revolution, while avoiding peripheral loss of fluid. This results in maximised propeller performance at all propeller speeds, increasing fuel economy. The propeller shroud and blades may be made from a material not subject to warping or deformation. The propeller may be used with an inboard or an outboard motor.

Description

PROPELLER DESIGN

Technical Field: This invention relates to Propeller design for watercraft propulsion.

Background: Past and current designs of marine inboard and outboard motor propeller designs suffer from inefficient fluid displacement ratios, resulting in an overall loss in performance and efficiency. Ideally, a ratio closest to a one-to-one is desirable, resulting in every unit of fluid being displaced by the leading edge of the propeller design, is displaced at the trailing edge of the propeller design. Current designs of propellers do not achieve nearly the ideal ratio due to the phenomena of "slippage". The problem of slippage occurs at all speeds in which hydro-methanical flow passing through the front of a propeller (intended to be displaced at the rear of the propeller), is lost prematurely on the peripheral sides of the blades (the central axis or drive shaft is also part of the problem as water is displaced outwards and around this area). Peripheral exposure of a propeller's blades and lack of enclosure of the blades results in this problem of slippage. As a result, overall pressure and fluid velocity is decreased at the outflow point of a propeller. The net result is less distance obtained by the watercraft per each revolution of a propeller and less fuel efficiency.

In addition, prior designs of watercraft propellers experience atmospheric ventilation at high speed because atmospheric gases are introduced to the peripheral edges of a propeller blade.

Introduction of gaseous ventilation also decrease the overall mass and velocity of the fluid being displaced by a propeller, and again decreasing performance and efficiency, especially at high rates of revolution.

Another disadvantage of the prior propeller designs is that inadvertent or accidental contact with the propeller may occur during times of revolution, resulting in personal injury. This is due to the peripheral portions of a propeller's blades being exposed Should a propeller with exposed blades make contact with a submerged hard surface, catastrophic failure of a propeller can occur.

Watercraft vehicles, such as submarines, are currently pushed through the water using propeller-based propulsion systems. Drag forces acting on the central axis cause the water in front of, and around the axis, to become displaced and turbulent in nature.

These drag forces lead to decreased efflcency and a tower overall thrust. Further, such propeller-based propulsion systems cause an inrrae in the submarine's noise with an associated increase in speed This may aid others in detecting the submarine, enabling its destruction. The increase in noise s due largely to cavitation Cavitation is the formation of water vapor bubbles caused by rapId prrrHer move ent that creates a vacuum-like area in the incompressible water. The vapor pressure of the water forms a a bubble. Surrounding water pressure soon violently collapses the bubble creating substantial noise.

Water on a normal propeller design slips off from the blade at the outer region of the blade (which is moving fastest). The proposed design provides an innovative way to get that normal slip off water to become displaced water as it is focused on the volume of water within the cylindrical shroud.

Essential Technical Features: According to the present invention there is provided a propeller design for use as a propulsion system for watercraft. The propulsion system comprises of curved, twisted, shaped propeller blades mounted inside a cylindrical shroud with no attachment of the blades or shroud to a central shaft axis.

The curved, twisted configuration of the blades creates a jet-like drive system configured to propel water rearward with improved performance.

Example: A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:Figure 1 shows in perspective, the propeller design.

Figure 2 shows in front view, the propeller design.

Figure 3 shows in sectional view, the propeller design.

Referring to the drawings, the propeller design comprises a surrounding outer cylindrical shroud 1 and a series of blades 2 housed inside the shroud with no attachment of the blades or shroud to a central shaft axis.

Referring to drawings figure 1, 2 and 3, the propeller design would be rotated in a clockwise direction to propel a watercraft.

Referring to drawings figure 1, 2 and 3, the leading edge of the propeller design is shown as dosest to the viewer.

The proposed propeller design would be used as a propulsion unit mounted to the submerged portion of a motor.

The propulsion unit could be situated behind or in front or replace the need for a rudder, allowing full performance of its intended design and function.

The propulsion unit is cylindrical in shape, with both leading and trailing edges open allowing the unrestricted hydro-dynamic flow both to, and away from the propulsion unit propeller blades.

The inner diameter of the shroud connects with the outer diameter of the propeller blades located inside it.

The shroud around the propeller blades minimizes slippage by eliminating slippage and directing fluid from a propeller's leading edge to a propeller's trailing edge, while maximizing fluid input- output ratios.

The risk of atmospheric ventilation is reduced significantly.

The shroud reduces the risk of personal injury or incident during times or propeller revolution. The shroud can be retrofitted by the utilization of fasteners, or can be pre-casted from an outboard engine manufacturer during assembly line fabrication.

The diameter of the leading edge of the shroud is large enough to allow the propeller blades to displace a significant enough amount of fluid and avoid choking.

The diameter of the shroud is only slightly larger than a propeller blades, resulting in its anti-slippage characteristics. This unique aspect of the shroud results in the increase of performance.

The trailing edge of the shroud directs maximum outward flow of propeller wash rearward, and focusing thrust at high rates of propeller revolution.

Fluid which is restricted from being lost at the peripheral portions of a propeller as a result of the shroud is displaced along with the rest of the fluid, away from the trailing edge of the shroud.

The diameter of the leading edge of the shroud is large enough to allow the appropriate volume of fluid to make contact with the leading edge of the propeller blades and be displaced to the rear.

The shroud is cylindrical and therefore the diameter of the shroud is uniform, symmetrical, and only slightly larger in relationship the propeller blades and encloses the peripheral sides of the propeller by 360 degrees.

The propulsion system is a propeller-based system with a shroud enclosing the propeller blades, with no central shaft axis.

Upon rotation the propeller design forms a jet due to the arrangement of blades attached to the rotating shroud.

The shroud is shaped to provide an inlet and outlet for water; generally, the trailing edge is shaped (rounded) to minimize cavitation at stealth speed.

Claims

1 A propeller design for use as a propulsion system for watercraft, comprising of a plurality of curved blades secured to a shroud surrounding the plurality of blades and submerged in water.

2 A watercraft propulsion device with an anti-slippage shroud for use on motor powered craft.

3 The propulsion system may also be used for maneuvering the vehicle.

4 A propulsion device, comprising of a cylindrical shroud which is fixed to the submerged portion of an inboard or outboard motor, for use by motor powered watercraft.

The shroud having only the same inner diameter as the said propeller's outer diameter, centered inside the shroud's inner circumference resulting in contact between the inner surface of the shroud and the peripheral sides of a propellers blades.

6 The leading edge of the shroud allowing unrestricted hydro- mechanical flow to a propeller blade's leading edge, while the peripheral side of the shroud encompasses the entire peripheral circumference of the propeller blades, eliminating displacement and loss of fluid from the peripheral side of each propeller blade, minimizing slippage during rates of high revolution and increasing performance.

7 The propulsion unit not restricting adequate passage of hydromechanical flow to a motor's cooling system.

8 The propeller shroud minimizes slippage by being in contact with the peripheral circumference of the propeller blades situated inside the shroud, maximizing fluid displacement input-output ratios per each revolution of the propeller while avoiding peripheral loss of fluid, resulting in maximized performance of the propeller blades during all operating speeds, an increase in fuel economy.

9 The shroud enclosing the propeller blades, to avoid accidental contact with a propeller.

The shroud eliminating access to the peripheral portion of propeller blades enclosed by the shroud during periods of revolution by either individuals, or accidental encounters with submerged objects, or grounding.

11 The propeller shroud and blades being constructed of material not subject to warping or deformation, mounted to the submerged portion of an inboard or outboard motor. (0

12 A propulsion system for use on watercraft which utilize either an inboard motor, or an outboard motor.

13 A method and apparatus for propelling a watercraft through the water comprised of a submerged portion, including a propulsion unit. The unit has attached from the shroud spirally wound propeller blades.

14 A feature of the present invention is the provision of a method and apparatus for propelling a surface ship through water that provides higher speed at stealth.

The shroud may be driven and turned without direct contact with an external gear or transmission but instead by magnetic fields.

16 The propulsion unit could be situated behind or in front or replace the need for a rudder, allowing full performance of its intended design and function.