Propulsion device for applying thrust to a fluid
The propulsion device improves thrust generation and efficiency by incorporating radially arranged propulsion elements and guide elements, reducing resistance and cavitation, and minimizing vibrations.
Patent Information
- Application Number
- JP2024575424
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-19
- Filing Date
- 2023-12-11
- Publication Date
- 2025-07-17
- Estimated Expiration
- 2043-12-11
AI Technical Summary
Conventional screw propellers exhibit high rotational resistance, low energy efficiency, susceptibility to cavitation, undesirable vibrations, and significant slip, which reduces their performance and efficiency.
A propulsion device with a central hub and radially projecting propulsion structures featuring front, rear, and intermediate elements, along with outer and inner guide elements, which enhance thrust generation while minimizing radial flow and cavitation, and reduce resistance and vibrations.
The propulsion device achieves high efficiency with low axial and circumferential resistance, concentrated axial flow, reduced cavitation, and minimal noise and vibrations, enhancing overall performance.
Smart Images
Figure 2025522744000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure generally relates to the field of propulsion devices for generating thrust in fluids. The propulsion devices disclosed herein can be used in various applications, such as the propulsion of marine vessels and aerial vehicles including drones, and the generation of forced fluid flows such as fans, blowers, and liquid pumps.
Background Art
[0002] Conventional screw propellers typically include a rotating hub and two or more blades fixed to the hub and protruding radially therefrom. The blades are arranged at a pitch such that they describe a helical spiral similar to a screw line.
[0003] Such conventional screw propellers typically have a relatively high rotational resistance, resulting in a high motor load and low energy efficiency. In addition, conventional screw propellers are susceptible to cavitation, which can damage the blades, cause undesirable vibrations, and generate noise. Furthermore, such conventional screw propellers typically exhibit a significant amount of slip, further reducing energy efficiency.
[0004] Patent Document 1 discloses a screw propeller including a hub and a plurality of radial support main blades fixed to the hub. Each main blade is connected to a first auxiliary blade disposed in front of the main blade and a second auxiliary blade disposed behind the main blade. The tips of the main blade and the auxiliary blades extend radially beyond the connection portion of the main blade and the auxiliary blades.
Prior Art Documents
Patent Documents
[0005]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0006] An object of the present invention is to provide an improved propulsion device for generating thrust in a fluid.
[0007] Another object is to provide a propulsion device that exhibits high efficiency.
[0008] A further object is to provide a propulsion device that generates axial flow with a relatively small separation.
[0009] Yet another object is to provide a propulsion device that exhibits a relatively low resistance to a fluid.
[0010] Yet another object is to provide a propulsion device that prevents cavitation.
[0011] A further object is to provide a propulsion device that has relatively little slip.
Means for Solving the Problems
[0012] In general, all terms used in the claims should be interpreted according to their ordinary meanings in the technical field, unless explicitly defined otherwise in this specification. All references to "an / a / the element, apparatus, component, means, step, etc." should be construed openly as referring to at least one example of the element, apparatus, component, means, step, etc., unless otherwise specified. The steps of any method disclosed in this specification need not be performed in the exact order disclosed, unless otherwise specified.
[0013] According to a first aspect, the present disclosure provides a propulsion device as recited in appended claim 1. The propulsion device is arranged to exert a thrust force on a fluid. The propulsion device has a front end portion and a rear end portion, and includes a central hub that rotates about a longitudinal axis extending between the front end portion and the rear end portion, and at least two propulsion structures that project radially from the hub and are evenly distributed on the circumference of the hub. Each propulsion structure includes a front propulsion element that extends radially from a front inner end portion to a front outer end portion, and a rear propulsion element that extends radially from a rear inner end portion to a rear outer end portion. An outer guide element extends from the front outer end portion to the rear outer end portion at a position at a radial outer guide element distance from the rotational axis, and an inner guide element extends from the front inner end portion to the rear inner end portion at a position at a radial inner guide element distance from the rotational axis. An elongated front distance member and an elongated rear distance member extend radially from the hub to the inner guide element. At least one intermediate propulsion element is disposed between the front propulsion element and the rear propulsion element and extends radially from the inner guide element to the outer guide element. The longitudinal projections of the front propulsion element, the intermediate propulsion element, and the rear propulsion element at least partially overlap. The outer circumferences of the inner guide element, the front distance member, the rear distance member, and the hub define an open space that allows free passage of the fluid.
[0014] By providing a propulsion device with an intermediate propulsion element extending from an inner guide element disposed at a distance in the radial direction from a hub, the propulsion device provides an additional thrust generating surface at the peripheral portion of the propulsion device. The thrust generating region disposed at the peripheral portion of the propulsion device provides higher thrust and lower resistance in the axial and tangential directions than the blade region at the central portion of a conventional screw propeller. Therefore, the intermediate propulsion element improves the efficiency of the propulsion device by increasing the thrust while maintaining a low resistance. Inner guide elements and outer guide elements extending longitudinally between all the propulsion elements in one propulsion structure reduce the radial flow and promote the generation of axial flow. As a result, the axial component of the flow generated by the propulsion device increases while keeping the lateral separation of the flow low. This also contributes to improving the efficiency of the propulsion device. The outer guide element and the inner guide element also enhance the rigidity of the propulsion device, so that the propulsion elements can be made relatively thin and vibrations can be reduced. The outer guide element further reduces cavitation at the peripheral portion of the propulsion element, and thus reduces the wear of the propulsion element as well as noise and other vibrations.
[0015] This propulsion device has been demonstrated to be highly efficient, with low resistance in both the axial and circumferential directions, highly concentrated axial flow, small lateral separation, little cavitation generation, and low levels of noise and other vibrations.
[0016] In one embodiment of the propulsion device, the longitudinal projections of the front propulsion element, the intermediate propulsion element, and the rear propulsion element completely overlap. As a result, the axial resistance is further reduced.
[0017] The lengths of the axial projections of the chord lines of the front, rear, and intermediate propulsion elements may be essentially constant. Therefore, the axial projection of the propulsion element shows a rectangular or rhombic shape. This makes it possible to increase the effective propulsion element area while maintaining a short chord line. This increases the thrust while minimizing cavitation.
[0018] The maximum chord line of each of the front, rear, and intermediate propulsion elements may be a short chord line. Such a short chord line is defined by the NACA standard nomenclature. Accordingly, the propulsion element has a relatively short circumferential extension in the action region radially outside the inner guide element, thereby reducing cavitation.
[0019] The inner guide element distance (IG) can be at least 40% of the outer guide distance (OG). This means that the intermediate propulsion element is arranged at a sufficient distance from the axis of rotation in order to impart a large thrust against the resistance.
[0020] The outer guide element may protrude rearward from the rear outer end. And the protruding portion of the outer guide element provides a so-called winglet that efficiently reduces cavitation.
[0021] The outer guide element and the inner guide element can exhibit a substantially constant longitudinal cross-section that is convex outward. This reduces the circumferential resistance.
[0022] The outer guide element and the inner guide element can exhibit a substantially constant longitudinal cross-section that is concave inward. This further reduces the circumferential resistance.
[0023] The radius of curvature of the convex or concave shape may be substantially equal to the radial distance from the axis of rotation to each of the outer guide element and the inner guide element. This also reduces the circumferential resistance.
[0024] The distance between the leading edge and the trailing edge of each of the front propulsion element, the rear propulsion element, and the intermediate propulsion element may be essentially constant. This also enables a large acting propulsion element area while keeping the chord line relatively short.
[0025] The front distance member and the rear distance member may be aligned longitudinally.
[0026] The front distance member and the rear distance member can be arranged to extend radially from the front inner end and the rear inner end toward the hub, respectively.
[0027] Each propulsion structure can include a plurality, preferably two or three intermediate propulsion elements. This further enhances the advantage of arranging the acting propulsion element region at the peripheral portion of the propulsion device.
[0028] The propulsion device may include two propulsion structures spaced 180° apart in the circumferential direction, three propulsion structures spaced 120° apart in the circumferential direction, four propulsion structures spaced 90° apart in the circumferential direction, five propulsion structures spaced 72° apart in the circumferential direction, or six propulsion structures spaced 60° apart in the circumferential direction.
[0029] Further objectives and advantages of the propulsion device according to the first, second, and third aspects will become apparent from the following description of the exemplary embodiments and the appended claims.
[0030] Next, with reference to the accompanying drawings, aspects and embodiments will be described as an example.
Brief Description of the Drawings
[0031]
Figure 1
[0032]
Figures 2a-c
[0033]
Figure 3
[0034]
Figure 4
Mode for Carrying Out the Invention
[0035] Detailed Description Hereinafter, aspects of the present disclosure will be described more fully with reference to the accompanying drawings, in which specific embodiments of the invention are shown.
[0036] However, these aspects can be embodied in many different forms and should not be construed as limited. Rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of all aspects of the invention to those skilled in the art. Like reference numerals refer to like elements throughout the specification.
[0037] The propulsion devices shown in all of FIGS. 1 to 4 are intended for ship propulsion. Other embodiments not shown within the scope of the present disclosure can be used for other applications, such as the propulsion of airships including drones, and the generation of forced fluid flows such as fans, blowers, and pumps.
[0038] The marine propulsion device according to the embodiment shown in FIGS. 1 to 2c includes a central hub 10 that rotates about a central axis of rotation A. In the illustrated example, the hub 10 is arranged to pass exhaust gas from an outboard engine or an inboard engine (not shown) into the interior of the hub. The hub is a conical end taper from the front end 11 to the rear end 12. The hub 10 includes a central bore 13 that extends longitudinally from the front end 11 to the rear end 12. A sleeve member 14 that is splined on the inner cylindrical side extends in the central direction through the bore 13. The sleeve member 14 is fixed to the inner wall of the bore 13 by four radial struts 15 such that an annular flow path for discharging exhaust gas is formed in the bore 13 around the sleeve member 14.
[0039] The propulsion device further includes two propulsion structures 20 that are fixed to the circumferential surface of the hub 10 and are spaced 180° apart. Both propulsion configurations are the same, and only one will be described below for simplicity.
[0040] Each of the propulsion structures 20 includes a front propulsion element 30, a rear propulsion element 40, and an intermediate propulsion element 50. The front propulsion element 30 includes a front inner end 31 and a front outer end 32. Correspondingly, the rear propulsion element 40 includes a rear inner end 41 and a rear outer end 42.
[0041] The outer guide element 60 extends parallel to the rotation axis A from the front outer end 32 to the rear outer end 42. The outer guide element 60 is disposed at a position radially outward from the rotation axis A by a distance OG of the outer guide element. The outer guide element 60 projects axially a short distance behind the rear propulsion element 40, forming a winglet 61 that projects rearward.
[0042] The inner guide element 70 extends parallel to the rotation axis A from the front inner end 31 to the rear inner end 41. The inner guide element 70 is fixed to the outer periphery of the hub by an elongated front distance member 35 and an elongated rear distance member 45. The distance members 35, 45 each extend radially from the hub to the inner guide element 70. In the illustrated example, the front distance member 35 forms a radially inward extension of the front propulsion element 30, and the rear distance member forms a radially inward extension of the rear propulsion element 40. However, in other embodiments not shown, the distance members may be disposed at other longitudinal positions of the inner guide element as long as the inner guide element 70 is held at a position radially away from the hub 10.
[0043] The inner guide element 70 is disposed at a position radially inward from the rotation axis A by a distance IG of the inner guide element. The inner guide element distance IG is shorter than the outer guide distance OG but larger than the maximum outer diameter of the hub 10. That is, the inner guide element 70 is disposed between the outer periphery of the hub and the outer guide element 60 in the radial direction. In the illustrated example, the inner guide element distance IG is about 60% of the outer guide element distance OG. The inner guide element distance IG is preferably 40% to 75% of the outer guide element distance OG.
[0044] The radially outer surface of the outer guide element 60 is convex with a radius of curvature that is essentially equal to the outer guide element distance OG. The radially inner surface of the outer guide element 60 is concave with a radius of curvature that is essentially equal to the outer guide element distance OG.
[0045] Similarly, the inner guide element 70 has an outer convex surface and an inner concave surface, both of which exhibit a radius of curvature that is essentially equal to the inner guide element distance IG. This reduces the circumferential resistance of the propulsion device.
[0046] The intermediate propulsion element 50 is disposed at the longitudinal center between the front propulsion element 30 and the rear propulsion element 40 and extends radially from the inner guide element 70 to the outer guide element 60. The intermediate propulsion element 50 has an intermediate inner end 51 fixed to the inner guide 70 and an intermediate outer end 52 fixed to the outer guide 60.
[0047] From the above description, it is understood that the front distance member 35, the rear distance member 45, the outer periphery of the hub 10, and the inner guide element 70 define an open space through which a fluid (in this case water) can flow freely without imposing axial or circumferential resistance when the propulsion device rotates.
[0048] The front propulsion element 30, the rear propulsion element 40, and the intermediate propulsion element 50 exhibit essentially the same shape. In each of the propulsion elements 30, 40, 50, the leading edge is disposed essentially parallel to the trailing edge. Further, the axial projection of the propulsion element is essentially diamond-shaped. Additionally, the circumferential widths of the propulsion elements 30, 40, 50, the inner guide element 70, and the outer guide element 60 are essentially equal.
[0049] The circumferential widths of the propulsion elements 30, 40, 50 can also be represented by the length of the chord line (or chord) extending through each propulsion element from the leading edge to the trailing edge, and the axial projection of this chord line. In the propulsion device according to the present disclosure, it is possible to obtain a satisfactory thrust while keeping the chord line and its axial projection shorter than those of a conventional screw propeller. This is a great advantage because a short or small chord line reduces the risk of cavitation. The chord lines of the propulsion elements 30, 40, 50 are preferably shown to be so-called short chord lines or small chord lines according to the NACA standard terminology.
[0050] FIG. 3 shows a second embodiment of a propulsion device including a hub 110 and three propulsion structures 120 arranged at 120° intervals along the outer periphery of the hub 110.
[0051] FIG. 4 shows a third embodiment of a propulsion device including a hub 210 and four propulsion structures 220 arranged at 90° intervals along the outer periphery of the hub 210.
[0052] In the embodiments shown in FIGS. 3 and 4, the hubs 110, 210 and the respective propulsion structures 120, 220 are essentially equal to the hub 10 and the propulsion structure 20 shown in FIGS. 1 to 2c, and the description will not be repeated here.
[0053] In an embodiment not shown, each propulsion structure may include two or more intermediate propulsion elements arranged between a front propulsion element and a rear propulsion element. Even in such a case, the intermediate propulsion elements extend radially between an inner guide element arranged at a distance from the hub and an outer guide element, and this outer guide element extends between the outer ends of the front propulsion element and the rear propulsion element. In such an embodiment, each propulsion structure includes a total number of working propulsion elements equal to the sum of the intermediate propulsion elements arranged between the inner guide element and the outer guide element plus two.
[0054] In an embodiment not further illustrated, each propulsion structure may include two or more elongate spacer members that couple an inner guide element to the hub.
[0055] In all of the propulsion structures shown and described above, it is preferable that all of the propulsion elements of the propulsion structure are longitudinally aligned and completely overlap longitudinally.
[0056] Aspects of the present disclosure have been described above mainly with reference to some of its embodiments and examples thereof. However, as will be readily understood by those skilled in the art, other embodiments than those disclosed above are also equally possible within the scope of the invention as defined by the appended claims.
Claims
1. A propulsion device for applying a thrust to a fluid, comprising a central hub (10, 110, 210) having a front end portion (11) and a rear end portion (12), and rotating about a rotational axis (A) extending longitudinally between the front end portion (11) and the rear end portion (12); at least two propulsion structures (20, 120, 220) protruding radially from the hub (10, 110, 210) and evenly distributed on the circumference of the hub (10, 110, 210), each propulsion structure (20, 120, 220) comprising: - a front propulsion element (30) extending radially from a front inner end portion (31) to a front outer end portion (32); - a rear propulsion element (40) extending radially from a rear inner end portion (41) to a rear outer end portion (42); - an outer guide element (60) extending from the front outer end portion (32) to the rear outer end portion (42) at a position of a radial outer guide element distance (OG) from the rotational axis (A); - an inner guide element (70) extending from the front inner end portion (31) to the rear inner end portion (41) at a position of a radial inner guide element distance (IG) from the rotational axis (A); - an elongated front distance member (35) and an elongated rear distance member (45), the distance members (35, 45) extending radially from the hub (10) to the inner guide element (60); - at least one intermediate propulsion element (50) disposed between the front propulsion element (30) and the rear propulsion element (40) and extending radially from the inner guide element (70) to the outer guide element (60); - the longitudinal projections of the front propulsion element (30), the intermediate propulsion element (50), and the rear propulsion element (40) at least partially overlapping; - the inner guide element (70), the front distance member (35), the rear distance member (45), and the outer circumference of the hub (10) defining an open space allowing free passage of the fluid. A propulsion device.
2. The propulsion device according to claim 1, wherein the longitudinal projections of the front propulsion element (30), the intermediate propulsion element (50), and the rear propulsion element (40) completely overlap.
3. The length of the axial projection of the chord line of the front propulsion element (30), the length of the axial projection of the chord line of the rear propulsion element (40), and the length of the axial projection of the chord line of the intermediate propulsion element (50) are substantially constant. The propulsion device according to claim 1 or 2.
4. The maximum chord of each of the front propulsion element (30), the rear propulsion element (40), and the intermediate propulsion element (50) is a short chord defined by extending over a maximum of 60% of the angular range. The propulsion device according to any one of claims 1 to 3.
5. The inner guide distance (IG) is at least 40%, preferably 40% to 75%, of the outer guide distance (OG). The propulsion device according to any one of claims 1 to 4.
6. The outer guide element (60) protrudes rearward from the rear outer end (42). The propulsion device according to any one of claims 1 to 5.
7. The outer guide element (60) and / or the inner guide element (70) has an outwardly convex and essentially constant longitudinal cross-section. The propulsion device according to any one of claims 1 to 6.
8. The outer guide element (60) and / or the inner guide element (70) has an inwardly concave and essentially constant longitudinal cross-section. The propulsion device according to any one of claims 1 to 7.
9. The radius of curvature of the convex or concave shape is essentially equal to the radial distance (OG, IG) from the rotation axis (A) to each of the outer guide element (60) and / or the inner guide element (70). The propulsion device according to claim 7 or 8.
10. The distance between the leading edge and the trailing edge of each of the front propulsion element (30), the rear propulsion element (40), and the intermediate propulsion element (50) is essentially constant along the radial extension of the propulsion elements (30, 40, 50). The propulsion device according to any one of claims 1 to 9.
11. The front distance member (35) and the rear distance member (45) are longitudinally aligned. The propulsion device according to any one of claims 1 to 10.
12. The front distance member (35) and the rear distance member (45) are arranged as radial extensions from the front inner end (31) and the rear inner end (41) respectively towards the hub (10). The propulsion device according to any one of claims 1 to 11.
13. The propulsion device according to any one of claims 1 to 12, wherein each propulsion structure comprises a plurality, preferably two or three intermediate propulsion elements.
14. The propulsion device according to any one of claims 1 to 13, comprising two propulsion structures (20) spaced 180° apart from each other in the circumferential direction, three propulsion structures (120) spaced 120° apart from each other in the circumferential direction, four propulsion structures (220) spaced 90° apart from each other in the circumferential direction, five propulsion structures spaced 72° apart from each other in the circumferential direction, or six propulsion structures spaced 60° apart from each other in the circumferential direction.
Citation Information
Patent Citations
Improvements in screw propellers and the like
GB188206A
Aircraft propeller construction
US2344266A
JP40352C1