WO2009041897A1

WO2009041897A1 - Ship propeller having surface cutting propeller blades

Info

Publication number: WO2009041897A1
Application number: PCT/SE2008/051055
Authority: WO
Inventors: Torbjörn Eriksson
Original assignee: Stormfågeln Ab
Priority date: 2007-09-25
Filing date: 2008-09-19
Publication date: 2009-04-02
Also published as: SE0702129L

Abstract

Ship propeller having surface-cutting propeller blades (7), comprising members (9, 10, 11, 12) for conducting a gaseous medium to gas outlets (13) on or close to the rear edge (14) of the propeller blades (7).

Description

HIP PROPELLER HAVING SURFACE CUTTING PROPELLER BLADES

TECHNICAL FIELD

The present invention relates to a ship propeller having surface-cutting propeller blades, comprising a central hub housing and at least two essentially diametrically opposed propeller blades which are supported by the hub housing and have an at least substantially triangular cross-sectional profile, with the apex of the triangle forming the front edge of the propeller blade and the base of the triangle forming its rear edge.

BACKGROUND ART

When a propeller having the above-described cross-sectional profile moves through the water, an underpressure is formed at the rear edge of the propeller. This underpressure creates a resistance to the movement of the propeller through the water. The resistance can be significant when the propeller installation is not a height-adjustable drive of the Arneson™ type, but rather a fixed installation, since this, in a planing craft, lies wholly beneath the water upon launch and the underpressure therefore acts upon all the propeller blades throughout the propeller revolution, i.e. including those blades which normally in a planing situation lie above the water surface.

DISCLOSURE OF INVENTION

The object of the present invention is to produce a boat propeller of the type stated in the introduction, which is especially intended for such installations in which the propeller lies totally beneath the water when the vessel is laid up or is travelling at non-planing speed and operates in a surface-cutting manner at planing speed and which in this context, in a fully lowered position in the water, produces lower rotation resistance than previously known surface-cutting propellers.

This is achieved according to the invention by the fact that members are arranged to conduct a gaseous medium to outlets on or close to the rear edge or suction side of the propeller blades. The gaseous medium can be exhaust gases from the engine(s) of the vessel or air which is itself sucked down as a result of the underpressure and which, when it flows out at the propeller blades, re- duces the underpressure on the rear edge or suction side of the blades and hereupon reduces the rotation resistance in the water.

In a preferred embodiment, the rear edge of the respective propeller blade is concave, so that a channel which is open to the rear and extends from the said outlets to the tip of the blade is formed. It is thereby ensured that the gaseous medium is conducted along the whole of the rear edge of the blade from its root to its tip.

In an especially preferred embodiment, the propeller blades are disposed on propeller blade carriers, which are rotatably mounted in the hub housing to enable the pitch of the blades to be varied. By combining, upon launch, a blowout of gaseous medium behind the blades with a low pitch setting for the blades, an optimally low rotation resistance in the water is achieved, so that, if the engine, for example, is a turbo-charged engine, the rev speed range in which the turbocharger produces maximum charging pressure is reached in the shortest possible time. BRIEF DESCRIPTION OF DRAWINGS

The invention is described in greater detail below with reference to illustrative embodiments shown in the appended drawings, in which:

Fig. 1 shows a diagrammatic longitudinal section through a propeller installation having an embodiment of a surface-cutting propeller according to the present invention,

Fig. 2 shows a partial enlargement of the view in Fig. 1 , Fig. 3 shows a diagrammatic end view of the propeller in Fig. 1,

Fig. 4 shows a partial enlargement of the view in Fig. 3,

Fig. 5 shows a diagrammatic cross section through a nozzle for the supply of gaseous medium to the hub housing of the propeller in Fig. 1 , and Fig. 6 shows a cross section through a propeller blade of the propeller according to the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

In Fig. 1 , 1 denotes the stern portion of a vessel, in which a propeller shaft 2 is rotatably mounted in a bearing 3. The propeller shaft 2 supports a propeller, denoted in general terms by 4, comprising a fastening flange 5 fixed to the shaft 2, a hub housing 6 connected to the fastening flange, and propeller blades 7, which in the shown illustrative embodiment are ten in number and are fixed to a blade carrier 8 which is rotatably mounted in the hub housing 6 to allow the pitch of the blades 7 to be varied. The rotation of the blades is achieved with a mechanism (not shown), which can be of the type which is shown and described in SE-A-0701543-1. In front of the propeller 4, a nozzle 9 having an inlet 10 and an outlet 11 is fixed to the hull 1. The inlet 10 communicates with a source (not shown) for supplying a gaseous medium to the nozzle 9. The gaseous medium can be exhaust gases from the engine(s) of the vessel or air from an air compressor. The outlet 11 communicates with distribution ducts 12 in the hub housing 6 and in the propeller blade carriers 8. In the shown preferred embodiment, the respective distribution duct 12 has an outlet 13, which is placed directly adjacent to the rear edge 14 of the blades. A certain deviation from the placement directly behind the rear edge of the propeller blade can however be permitted.

In Fig. 6 is shown the cross-sectional profile of the propeller blades 7, which in accordance with the norm for surface-cutting propellers, is triangular, with the front edge 15 of the blades in the apex of the triangle and the rear edge 14 of the blades in the base of the triangle. The profile of the embodiment shown in Fig. 6, which embodiment is preferred according to the invention, differs from the traditional profile of previously known surface-cutting propellers by the fact that the rear edge is concave, so that a channel 17 is formed which is open to the rear. In interaction with the surrounding water, a closed channel is formed, which conducts the gaseous medium from the blade root to the tip. In this way, the underpressure, and hence the rotation resistance in the water, is reduced.

Fig. 5 illustrates in diagrammatic representation, an embodiment of the nozzle 9, which has blocking members 18 blocking parts of the nozzle in order for the gas to be conducted to a certain part of the nozzle - in the shown illustrative embodiment the lower part - so that gas is only supplied to the distribution ducts in the bottom half of the propeller. The blocking of the sections can, of course, be moved to the desired place in dependence on the size of the vessel. The described embodiment, having both a gas supply to and a variable pitch for the blades, enables the minimum possible rotation resistance in the water to be achieved at speeds below the planing threshold. This means that, during acceleration, the engine speed at which the turbocompressor of a turbocharged engine produces full charging pressure is reached in the shortest possible time, which in turn results in the planing threshold, too, being able to be reached in the shortest possible time. Once maximum charging pressure and engine torque have been achieved, the gas supply is shut off and the blade pitch is gradually increased to a pitch suitable for the chosen speed.

Claims

1. Ship propeller having surface-cutting propeller blades, comprising a central hub housing (6) and at least two essentially diametrically opposed propeller blades (7) which are supported by the hub housing and have an at least substantially triangular cross-sectional profile, with the apex (15) of the triangle forming the front edge of the propeller blade and the base of the triangle forming its rear edge (14), characterized in that members (9, 10, 11, 12) are arranged to conduct a gaseous medium to outlets (13) on or close to the rear edge of the propeller blades.

2. Ship propeller according to Claim 1, characterized in that the rear edge (14) of the respective propeller blade is concave, so that a channel (17) which is open to the rear and extends from the said outlets (13) along the rear edge (14) to the tip of the blade is formed.

3. Ship propeller according to Claim 1 or 2, characterized in that the said members comprise a nozzle (9) having an inlet (10) for the gaseous medium and an outlet (11) which open out into distribution ducts (12) in the hub housing (6) and in propeller blade carriers (8), which distribution ducts open out into the said outlets (13).

4. Ship propeller according to any one of Claims 1-3, characterized in that members (18) are arranged to allow blocking of the supply of the gaseous medium to chosen distribution ducts (12).

5. Ship propeller according to any one of Claims 1-4, characterized in that the propeller blades (7) are disposed on propeller blade carriers (8), which are rotatably mounted in the hub housing (6) to enable the pitch of the blades (7) to be varied.

6. Ship propeller according to any one of Claims 1-5, characterized in that the hub housing (6) supports ten propeller blades (7) arranged diametrically opposite one another in pairs.