MARINE PROPELLER APPLICABLE TO ALL SPEED RANGES

Abstract

An all speed range propeller includes a propeller hub and plural propeller blades having their shafts symmetrically connected with the propeller hub. Each propeller blade is divided into a first region and a second region from the propeller hub to an outer end. The first region and the second region are different in wing structure, and the wing cross-sectional area of the second region is smaller than that of the first region. Thus, in speed ranges that common ships navigate most frequently, the all speed range propeller of this invention can lower the influence of cavitation produced because of different speed ranges, able to maintain high efficiency in use and prevent the efficiency of the propeller from lowered exceedingly.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a marine propeller.

2. Description of the Prior Art

Conventionally, marine propellers are mainly categorized as NACA series propellers, KCA series propellers and Super-cavitating series propellers. Referring to FIG. 1, through viscous flow analysis and cavitation module analysis, it is found that when the surface ratio of the NACA series propeller is 1.0 and the speed range is 20 knots, the efficiency of the propeller is 0.72, and when the speed range is up to 40 knots, the efficiency is only 0.5. Obviously, when the NACA series propeller is operated in different speed ranges, the efficiency of the propeller will drop sharply because of cavitation, and it can also be found that the conventional propellers like the NACA series propeller can produce best efficacy only at some speed ranges, and once it goes beyond these ranges, its efficacy will drop greatly. In addition, the propellers employed by common ships are mostly NACA series propellers or KCA series propellers when the speed is under 30 knots, while the super-cavittating series propellers are mainly adopted if the speed is over 30 knots. However, for the present, the most frequent navigation speed of common ships is between 20 and 40 knots; therefore, if the NACA series propeller or the KCA series propeller is adopted and the navigation speed is over 30 knots, not only the efficacy of the propellers will be lowered greatly because of cavitation, but also the surfaces of propeller will produce numerous burst bubbles due to cavitation and make the ship body vibrate.

SUMMARY OF THE INVENTION

The objective of this invention is to offer an all speed range propeller applicable to high and low speed ranges. The all speed range propeller is composed of a propeller hub and a plurality of propeller blades having their shafts symmetrically connected with the propeller hub. Each propeller blade is formed with an upper surface and a lower surface, which have a junction of their front half section formed into a wing front edge and a junction of their rear half section formed into a wing rear edge. Each propeller blade is divided into a first region and a second region extending from the propeller hub to an outer end, and the first region and the second region are different in wing structure and the wing cross-sectional area of the second region is smaller than that of the first region. The propeller blades are radially combined with the propeller hub.

Each propeller blade contains two kinds of wing structures to make up an all speed range propeller. In speed ranges that ships navigate most frequently, the all speed range propeller of this invention can lower the influence of cavitation produced because of different speed ranges, able to maintain high efficiency in use and prevent the efficiency of the propeller from being lowered excessively.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be better understood by referring to the accompanying drawings, wherein:

FIG. 1 is a perspective view of a conventional NACA propeller;

FIG. 2 is a front view of a first preferred embodiment of an all speed range propeller in the present invention;

FIG. 3 is a cross-sectional view of the line B-B in FIG. 2;

FIG. 4 is a cross-sectional view of the line A-A in FIG. 2;

FIG. 5 is a cross-sectional view of a second preferred embodiment of the line A-A in FIG. 2;

FIG. 6 is a distribution curve of the torsion (KQ) of an all speed range propeller in the present invention;

FIG. 7 is a distribution curve of the thrust of the all speed range propeller in the present invention; and

FIG. 8 is a distribution curve of the pressure of the all speed range propeller in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A first preferred embodiment of an all speed range propeller 100 in the present invention, as shown in FIGS. 2-4, is composed of a propeller hub 200 and a plurality of propeller blades 10 having their shafts symmetrically connected with the propeller hub 200. In this preferred embodiment, the all aped range propeller 100 is provided with four propeller blades 10 respectively formed with an supper surface 11 and a lower surface 12, and the junction of the front half section of the upper surface 11 and the lower surface 12 is formed into a wing front edge 13, and a junction of the rear half section of them is formed into a wing rear edge 14. Each propeller blade 10 is divided into a first region 15 and a second region 16 extending from the propeller hub 200 to an outer end. The first region 15 and the second region 16 of each propeller blade 10 are different in wing structure, and the wing cross sectional area of the second region 16 is smaller than that of the first region 15. Then, such designed propeller blades 10 are radially combined with the propeller hub 200 to form an all speed range propeller 100.

Referring to FIG. 3, in this preferred embodiment, the first region 15 has its upper surface formed with an upper convex-curved portion 151 extending from the wing front edge 13 to the wing rear edge 14, and the rear half section of its lower surface formed with a first lower convex portion 152 extending toward the wing rear edge 14. Further, the upper surface and the lower surface of the second region 16 are formed with at least one concave portion. Referring to FIG. 4, in this preferred embodiment, a front half section of the upper surface of the second region 16 is formed with an upper even-smooth portion 161 and a rear half section is formed with a first upper concave portion 162 stretching toward the wing rear edge 14. Furthermore, a front half section of the lower surface of the second region 16 is formed into a lower even-smooth portion 163 and a rear half section formed into a second lower convex portion 164 stretching toward the wing rear edge 14.

A second preferred embodiment of an all speed range propeller 100 in the present invention, as shown in FIG. 5, is to have a rear half section of the upper surface of the second region 16 formed with a second upper concave portion 165 extending toward the wing rear edge 14, and a front half section of the lower surface of the second region 16 formed with a lower concave portion 166 extending toward the wing rear edge 14, making the second region 16 into an S-shaped wing structure.

In addition, each propeller blade 10 has an intermediate portion formed with a central region 17 that has its upper surface and lower surface connected between the first region 15 and the second region 16 with great-extent curvature changes so that the mutually jointing surface of the first region 15 with the second region 16 can be formed into a circular and smooth curve and avoid forming an irregular surface therebetween, letting the all speed range propeller 100 look beautiful in a appearance. Moreover, the central region 17 is a very small region connected between the first region 15 and the second region 16, able to reduce influence to the propeller 100 while it is operated and thus enabling the all speed range propeller 100 to attain optimized efficacy of operation.

Referring to FIGS. 3-5, the second region 16 of each propeller blade 10 is lighter and thinner than the first region 15, thus effectively lessening the whole weight of each propeller blade 10 and lowering the turning moment from each propeller blade 10 to the propeller hub 200. Therefore, when the propeller hub 200 is started to rotate, each propeller 10 can be rotated faster than a conventional propeller.

In addition, referring to FIGS. 3 and 4, the upper surface of the first region 15 has a location adjacent to the wing rear edge 14 defined to be an upper apex 153, and the lower surface of the first region 15 has a location adjacent to the wing rear edge 14 defined to be a lower apex 154. When the all speed range propeller 100 is rotated at intermediate and high speed ranges, cavitation bubbles will be formed at both locations of the upper apex 153 and the lower apex 154 of the first region 15 of the all speed range propeller unit 100, and foresaid cavitation bubbles will form a cavitation bubble area stretching toward the wing rear edge 14. Meanwhile, cavitation bubbles will also be formed at the first upper concave-curved portion 162 of the upper surface and at the second lower convex-curved portion 164 of the lower surface of the second region 16, and foresaid cavitation bubbles will form a cavitation bubble area.

On the other hand, when the all speed range propeller 100 is rotated at low and intermediate speed ranges, the lift coefficient of a unit area of each propeller blade 10 becomes large, able to decrease the area of each propeller blade 10 and equally attaining the same efficiency as the NACA series propeller and thus saving cost of materials.

Moreover, referring to FIGS. 6, 7 and 8 that are distribution diagrams of the torsion (KQ), the thrust (KT) and the pressure (−CP) of the all speed range propeller. It can be seen from FIGS. 6 and 7 that the curves of the torsion and the thrust of the all speed range propeller of this invention, after cavitating and at speeds of 30 and 40 knots, are higher than the curve of the torsion and the thrust of the propeller before cavitating and at a speed of 20 knots. Apparently, the all speed range propeller 100 of this invention has excellent thrust and torsion either before or after cavitation, applicable to all speed ranges. Additionally, FIG. 8 is a diagram of a pressure distribution area of the propeller at a section where the radius is 0.7 R. It is found that the pressure distribution area, before cavitating and at a speed of 20 knots, will produce state of pressure reverse turn at the end of the propeller to offset the whole pressure area, but after cavitating and at a speed of 30 knots, the pressure at the end of the propeller will not turned reversely and the pressure distribution area is larger than that before cavitating and at a speed of 20 knots. Contrasting the pressure distribution area of the propeller in FIG. 8 with the thrust distribution of the propeller in FIG. 7, it can be found that the size of the pressure area can be homologized with the surface of the thrust.

While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention.

Claims

1. An all speed range propeller comprising a propeller hub and a plurality of propeller blades, said propeller blades having their shafts symmetrically connected with said propeller hub, each said propeller blade having an upper surface and a lower surface, said upper surface and said lower surface having a junction of their front half section formed into a wing front edge, said upper surface and said lower surface having a junction of their rear half section formed into a wing rear edge; and characterized by,

each said propeller blade divided into a first region and a second region in a direction from said propeller hub to an outer end, said first region and said second region different in wing structure and said each said propeller blade radially combined on said propeller hub, wing cross-sectional area of said second region smaller than that of said first region, in speed ranges that common ships navigate most frequently said all speed range propeller able to lower influence of cavitation produced due to different speed ranges, said all speed range propeller able to maintain high efficiency in use when operated in different speed ranges.

2. The all speed range propeller as claimed in claim 1, wherein said upper surface of said first region is formed with an upper convex portion extending from said wing front edge to said wing rear edge while a rear half section of said lower surface of said first region is formed with a lower convex portion stretching toward said wing rear edge, and said upper surface and said lower surface of said second region are formed with at least one concave portion.

3. The all speed range propeller as claimed in claim 1, wherein a front half section of said upper surface of said second region is formed with an upper even-smooth portion and a rear half section is formed with an upper concave portion extending toward said wing rear edge, a front half section of said lower surface of said second region formed with a lower even-smooth portion, a rear half section of said lower surface of said second region formed with a lower convex portion extending toward said wing rear edge.

4. The all speed range propeller as claimed in claim 2, wherein a rear half section of said upper surface of said second region is formed with an upper concave portion stretching toward said wing rear edge and a front half section of said lower surface of said second region is formed with a lower concave portion extending toward said wing rear edge, letting said second region generally formed into a S-shaped wing structure.

5. The all speed range propeller as claimed in claim 1, wherein each said propeller blade is further formed with a central region having an upper surface and a lower surface connected between said first region and said second region with great curvature change.

6. An all speed range propeller comprising a propeller hub and plural propeller blades having their shafts symmetrically connected with said propeller hub, each said propeller blade having an upper surface and a lower surface, said upper surface and said lower surface having a junction location of their front half section formed into a wing front edge, said upper surface and said lower surface having a junction location of their rear half section formed into a wing rear edge; and characterized by,

each said propeller blade divided into a first region and a second region from said propeller hub to an outer end, said first region and said second region different in wing structure, said propeller blades radially combined with said propeller hub, wing cross-sectional area of said second region being smaller than that of said first region, said upper surface of said first region of said all speed range propeller having a location adjacent to said wing rear edge defined to be an upper apex, said lower surface of said first region having a location adjacent to said wing rear edge defined to be a lower apex, cavitation bubbles formed at said upper apex and said lower apex of said first region when said all speed range propeller is rotated at intermediate and high speed ranges, said cavitation bubbles formed into a cavitation bubble area stretching toward said wing rear edge, said upper surface of said second region having a location adjacent to said wing rear edge defined to be a lower convex surface where cavitation bubbles are formed, said cavitation bubbles formed into a cavitation bubble area stretching toward said wing rear edge.

7. An all speed range propeller comprising a propeller hub and plural propeller blades that have their shafts symmetrically connected with said propeller hub, each said propeller blade having an upper surface and a lower surface, said upper surface and said lower surface having a junction of their front half section formed into a wing front edge, said upper surface and said lower surface having a junction location of their rear half section formed into a wing rear edge; and characterized by,

each said propeller blade divided into a first region and a second region from said propeller hub to an outer end, said first region and said second region different in wing structure, said propeller blades radially combined with said propeller hub, wing cross-sectional area of said second region smaller than that of said first region, lift coefficient of a unit area of each said propeller blade becoming great when said all speed range propeller is rotated at low and intermediate speed ranges, able to lessen area of each said propeller blade.