HK1025292B - Improved fluid displacing blade - Google Patents

Description

Improved fluid-discharging vane

Technical Field

The invention relates to a blade for acting on a fluid, in particular for a propeller of an aircraft, but it can also be used for a pump for acting on a fluid.

In particular, the invention relates to blades acting on water, which are used as propellers for water craft, or in rotary power machines in boats, such as yachts, propeller-propelled boats or ships, impeller-propelled jet drives, for example in inboard, outboard or stern drives. The invention can also be used for the rotation of air-discharging augers, such as airplanes, hovercraft and helicopters.

Furthermore, the invention can also be used for impellers for pumps, turbines or the like.

Background

In a waterjet, a difficulty encountered by propellers is that as the rotational speed of the propeller increases, a loss of power efficiency will result. Most of the efficiency losses that occur are due to the blades of the propeller generating a rotation in the water and, thereby, increasing turbulence or vortices in the water flow and generating power transmission losses. As the impeller speed is further increased, cavitation occurs, so that the likelihood of blade damage increases.

In australian patent specification AU25138/71 there is proposed a proposal in which apertures near the upstream edges of the impeller blades allow water flow from the front face of a blade to its rear face and equalise pressure between the blades around the circumference of the impeller, thereby reducing cavitation and noise.

The invention is achieved by providing a plurality of holes extending through both surfaces of a propeller blade, said holes extending in a direction substantially perpendicular to the radial direction of the rotating power machine, and said plurality of holes being arranged in a substantially uniform distribution over said blade. Thus, the arrangement and spatial distribution of the plurality of apertures may be considered critical in maximizing the benefit of the apertures.

In the description of the invention, unless otherwise indicated herein, the term "comprises/comprising" should be taken to include the stated features and groups of features, but not to exclude the presence of other features or groups of features.

Disclosure of Invention

According to one aspect of the present invention there is provided a blade for a rotary power machine for acting on a fluid, wherein the blade has two surfaces which are located on either side of the blade, at least one surface of the blade acting on the fluid, and between the two surfaces of the blade there is a plurality of apertures extending through the blade, the apertures extending in a direction substantially perpendicular to the radial direction of the rotary power machine, the plurality of apertures being located substantially uniformly across the blade.

Preferably, the cross-sectional area of the aperture may be up to 50% of the total blade area.

Preferably, the cross-sectional area of the aperture may be up to 20% of the total blade area.

Preferably, the cross-sectional area of the holes may be up to 10% of the total blade area.

Preferably, the cross-sectional area of the holes may be up to 5% of the total blade area.

Preferably, the cross-sectional area of the holes is about 1 to 3% of the total blade area.

Preferably, the cross-sectional area of the aperture is about 2% of the total vane area.

Preferably, the ratio of the sizes and diameters of the holes may be up to 1: 10. The holes are rectangular holes or elliptical holes having such a size diameter ratio.

Preferably, the ratio of the size to diameter of the holes may be up to 1: 4

Preferably, the ratio of the sizes and diameters of the holes may be up to 1: 2.

Preferably, the pores are circular or square in cross-section, with a ratio of pore diameters of 1: 1.

Preferably, the aperture comprises a sloping leading edge at the leading aperture on the blade.

The size of the holes depends on a number of factors, such as the speed of rotation of the blades through the fluid. In this respect, the size of the holes is preferably 2.5-3.5 mm, and the blade is used for a propeller of a power ship. The faster the speed of rotation or the smaller the pitch of the blades, the larger the aperture required. Furthermore, for blades used in propellers, the faster the rotational speed used or the smaller the pitch of the blade, the larger the cross-sectional area occupied by the holes in the blade.

In the propeller, it is preferable that the size of the hole at the outer edge of the blade (linear velocity is relatively large) be larger than the size of the hole near the hub. Preferably, the size of the holes is varied in a gradual or abrupt manner, with the diameter of the holes decreasing from the outer edge of the propeller towards the hub. For propellers in a powered boat or outboard power machine, the size of the holes near the outer edge of the blades may be about 2.8-3.0 mm, while the size of the holes closest to the hub may be about 2.0-2.2 mm. The size of the holes decreases from the outer edge of the blade towards the hub location. Preferably, the size of the holes between the outer edge of the blade and the hub is selected so that the fluid flow rate through each said hole is substantially constant along the blade, so that the applied action is uniform across the propeller.

Preferably, the plurality of holes are axially aligned in an extension direction up to 75 ° from the direction of motion of the vane.

Preferably, the plurality of holes are axially aligned in an extension of up to 60 ° relative to the direction of blade movement along the propeller axis.

Preferably, the plurality of holes are axially aligned in an extension direction up to 45 ° from the direction of blade movement relative to the propeller axis.

Preferably, the plurality of holes are axially aligned in an extension of up to 30 ° relative to the direction of blade movement along the propeller axis.

Preferably, the plurality of holes are axially aligned in an extension of up to 20 ° relative to the direction of blade movement along the propeller axis.

Preferably, the plurality of holes are axially aligned in an extension of up to 10 ° relative to the direction of blade movement along the propeller axis.

Preferably, the plurality of holes are axially aligned in an extension direction up to 5 ° from the direction of blade movement relative to the propeller axis.

Preferably, the plurality of holes are axially aligned in a substantially uniform direction of extension of the blade movement relative to the propeller axis.

The above-mentioned angle refers to the angle of the direction of rotation of the blades with respect to the axis of the propeller and does not include any component resulting from the forward motion imparted by the blades. In the case of blades with a small pitch, it is necessary to make the angle of the hole greater than 20 °. The smaller the pitch of the propeller, the larger the angle of inclination of the hole.

According to a second aspect of the invention, a rotary power machine is provided having at least one blade as described above.

Two or more of the vanes are preferably provided for mechanical balancing of the rotary power. In practice, the plurality of blades is arranged in a dynamically balanced configuration, typically comprising three or more blades.

It is to be understood that the rotodynamic machine may be a propeller used in rotodynamic machines in ships, such as yachts, propeller-propelled ships, impeller-propelled jet ships, e.g. in inboard, outboard or stern drives. Likewise, the rotary power machine may be a pump, an impeller of a turbine in a hydro-electric power plant. It will also be appreciated that the rotodynamic machine may be a rotating propeller for use in an aircraft or helicopter.

Drawings

A particular embodiment of the invention is described below with reference to the accompanying drawings, in which:

FIG. 1 is a view shown along the axis of rotation of the propeller of the described embodiment, this propeller being used in an outboard propeller of a boat;

FIG. 2 is a radial cross-sectional view of the screw propeller of FIG. 1, showing one blade of the propeller;

FIG. 3 is a side sectional view through one of the vanes shown in FIG. 1.

Detailed Description

Referring to fig. 1, a rotary power machine in the form of a propeller 11 is shown. The propeller 11 has five blades 13, said blades 13 being supported on a hub 14, and, as shown, the blade surfaces 15 of these blades 13 are facing the viewer, i.e. facing out of the paper. The propeller 11 is right-handed, and when the propeller 11 rotates clockwise, a driving force for driving the ship forward is generated. The area of each leaf surface 15 is about 4000mm²The length of the blade 13 is 80mm, and the width is 50 mm.

Thirty holes 19 extend from the blade face 15 to the blade back face 17 through each blade 13. The diameter of the holes in those locations near the outer edge of the propeller is 2.8mm, while the diameter of the holes in those locations near the hub 14 is 2.2 mm. The diameter of the holes in those locations in the central region 28-50 mm from the outer edge of the propeller is 2.5 mm. The axis of extension of said hole 19 is substantially aligned with the direction of movement of the blade 13 with respect to the axis of the propeller 11. The holes 19 are rectilinear for the sake of simplicity of construction. However, in another embodiment, the holes 19 are curved, which coincides with the direction of the angular movement of the propeller. The holes 19 may be perpendicular to the radial and axial directions of the propeller 11.

Each aperture 19 comprises a bevelled edge in the form of a countersunk lip 21, which countersunk lip 21 extends around the edge of the aperture 19 on the leaf surface 15. Such a counter-bore lip 21 may be formed when a chamfer tool is used to drill the bore 19, it being believed that the counter-bore lip 21 facilitates fluid flow through the blade face and through the bore 19. However, in another embodiment, the lip 21 may be omitted.

The propeller of the described embodiment would be used for a two horsepower outboard propeller, which would be mounted on an aluminum boat. It is believed that the water flow through the holes 19 interferes with the turbulent water adjacent the blade backs 17 of the propeller 11, thus improving the power transfer efficiency of the propeller.

In the case of a propeller driven by a more powerful motor, it is believed that the holes allow fluid to flow through where a vacuum and air bubbles form on the back of the propeller. This effect is known for cavitation, and the loss of power transmission, or loss of tractive force, resulting from cavitation, and cavitation-induced erosion of the blade surfaces.

In other embodiments the propeller may have a fine pitch and the holes may extend towards the back of the blades in a propeller having an extremely fine pitch, whereas the holes extend in the forward direction in the range 45-90, or even in the range 60-75 in the case of a very fine pitch propeller, the axial extension of the holes being measured at an angle relative to the axial direction of the propeller, but while the holes remain axially substantially perpendicular to the radial direction of the propeller.

It is obvious that the scope of the invention is not limited to the scope described in the embodiments.

Claims (27)

1. A blade for a rotary power machine for working on a fluid, wherein the blade has two surfaces which are located on either side of the blade, at least one surface of the blade being for working on the fluid, between the two surfaces of the blade, the blade having a plurality of holes extending through the blade, the holes having a total cross-sectional area of up to 20% of the total blade area, the holes extending in a direction substantially perpendicular to the radial direction of the rotary power machine, and the plurality of holes having an axial direction extending through the blade from a direction perpendicular to the axial direction of the rotary power machine to an extension direction of up to 30 ° from the direction of movement of the blade through the fluid; the plurality of holes are arranged at positions which are substantially evenly distributed on the blade.

2. The blade of claim 1, wherein: the cross-sectional area of the holes may amount to 10% of the total blade area.

3. The blade of claim 1, wherein: the cross-sectional area of the holes may amount to 5% of the total blade area.

4. The blade of claim 1, wherein: the cross-sectional area of the holes is 1-3% of the whole blade area.

5. The blade of claim 1, wherein: the cross-sectional area of the holes is about 2% of the total blade area.

6. The blade of claim 1, wherein: the cross-section of the hole is circular or square.

7. The blade of claim 6, wherein: the axial alignment of the plurality of holes is aligned with an extension of up to 20 ° of the direction of blade movement through the fluid.

8. The blade of claim 7, wherein: the axial alignment of the plurality of holes is aligned with an extension of up to 10 deg. of the direction of movement of the blades through the fluid.

9. The blade of claim 8, wherein: the axial alignment of the plurality of holes is aligned with an extension of up to 5 deg. of the direction of movement of the blades through the fluid.

10. The blade of claim 9, wherein: the plurality of holes are axially aligned in a direction of extension substantially coincident with the direction of blade movement through the fluid.

11. A rotary power machine having at least one blade according to claim 6.

12. The rotary power machine of claim 11, wherein: the size of the hole near the outer edge of the blade is larger than the size of the hole near the hub.

13. The rotary power machine of claim 12, wherein: the size of the holes decreases in a gradual or abrupt manner from the outer edge of the rotary power machine towards the hub.

14. The rotary power machine of claim 13, wherein: the holes between the outer edge of the blade and the hub are sized so that the fluid flow rate through each of said holes is substantially constant along the blade so that the applied action is uniform throughout the rotating power machine.

15. The rotary power machine of claim 11, wherein: a plurality of blades are arranged in a dynamic balance structure.

16. The rotary power machine of claim 15, wherein the size of the aperture adjacent the outer edge of the blade is greater than the size of the aperture adjacent the hub.

17. The rotary power machine according to claim 16, wherein the size of the hole decreases in a gradual or abrupt manner from an outer edge of the rotary power machine toward the hub.

18. The rotary power machine of claim 17, wherein the apertures between the outer edge of the blade and the hub are sized such that the fluid flow rate through each of said apertures is substantially constant along the blade, whereby the applied force is uniform throughout the rotary power machine.

19. The blade of claim 6, wherein: the aperture includes a beveled leading edge at the positive end of the aperture.

20. The rotary power machine of claim 19, wherein the size of the aperture adjacent the outer edge of the blade is greater than the size of the aperture adjacent the hub.

21. The rotary power machine according to claim 20, wherein the size of the holes decreases in a gradual or abrupt manner from the outer edge of the rotary power machine toward the hub.

22. The rotary power machine of claim 21, wherein the apertures between the outer edge of the blade and the hub are sized such that the fluid flow rate through each of the apertures is substantially constant along the blade, whereby the applied force is uniform throughout the rotary power machine.

23. A rotary power machine having at least one blade according to claim 19.

24. The rotary power machine according to claim 23, wherein the plurality of vanes are arranged in a dynamic balance configuration.

25. The rotary power machine of claim 24, wherein the size of the hole near the outer edge of the blade is larger than the size of the hole near the hub.

26. The rotary power machine according to claim 25, wherein the size of the holes decreases in a gradual or abrupt manner from the outer edge of the rotary power machine toward the hub.

27. The rotary power machine of claim 26, wherein the apertures between the outer edge of the blade and the hub are sized such that the fluid flow rate through each of the apertures is substantially constant along the blade, whereby the applied force is uniform throughout the rotary power machine.