WO2025116876A1

WO2025116876A1 - High-efficiency new blade profile for reducing radial and axial forces

Info

Publication number: WO2025116876A1
Application number: PCT/TR2024/051442
Authority: WO
Inventors: Tanya HÖKELEK
Original assignee: De Ta Proje Muehendislik Makina Enerji Danismanlik Elektrik Arge Imalat UertIthIhrSanVe TicAS
Current assignee: De Ta Proje Muehendislik Makina Enerji Danismanlik Elektrik Arge Imalat UertIthIhrSanVe TicAS
Priority date: 2023-11-30
Filing date: 2024-11-29
Publication date: 2025-06-05
Anticipated expiration: 2026-05-30

Abstract

The present invention relates to rotor blades that can be used effectively and advantageously in energy-generating or energy-consuming machines and systems operating based on aerodynamic and hydrodynamic principles, and specifically to blade profiles for use in propellers, fans and turbines, that extend their lifespan by reducing the axial and radial force effect on them In a preferred embodiment of the invention, pressure force and flow-directing bladelets (20) are provided on blade surfaces, each having arranged at an optimized angle such as perpendicularly or at a certain angle to the upper and lower surfaces of the blades (10, 12) and perpendicular or at a certain angle relative to the leading edge. In double blades with twin or hybrid profiles, some of the bladelets (20) on the lower surface of the upper blade (12) can be integrally combined with corresponding bladelets (20) on the upper surface of the lower blade (10), forming a solid intermediate bladelet structure (22).

Description

DESCRIPTION

HIGH-EFFICIENCY NEW BLADE PROFILE FOR REDUCING RADIAL AND AXIAL FORCES

Technical Field

The present invention relates to blades used in systems operating based on aerodynamic and hydrodynamic principles. The invention specifically relates to blade profile assemblies for use in fans, propellers and turbines of energy-generating or energy-consuming machines and systems.

Prior Art

Aerodynamic and hydrodynamic machines and systems are complex structures utilized for energy conversion. Predominantly based on the principles of fluid dynamics, these systems can be broadly classified into two main categories: energy-generating and energy-consuming systems.

Energy-generating systems include wind turbines and hydroelectric power plants, which convert the kinetic energy of wind or the potential energy of water into mechanical energy, and subsequently into electrical energy. Nuclear power plants utilize thermal energy to generate steam, which is then converted into electricity through steam turbines. Similarly, natural gas cycle power plants fall under this category. Energy-consuming systems, on the other hand, transform electrical or chemical energy into air, gas, or water flow. Devices such as centrifugal pumps, piston and gear pumps, axial and radial fans are examples of this category. On the other hand, the primary target of internal combustion engines is the transfer of mechanical energy.

The efficiency and success of these systems critically depend on the design of the blades used in turbines and fans, and their profile designs. Currently, there is a variety of blade and profile designs available for systems operating on aerodynamic and hydrodynamic principles. While the blade profiles used for fans and turbines operating based on aerodynamic principles are called "aerofoil" or "airfoil", the term "hydrofoil" is generally used for propellers and blade profiles operating based on hydrodynamic principles, such as ships, submarines and water turbines. Particularly, axial fans utilized in cooling towers are designed to operate in a configuration parallel to the ground; and owing to their substantial structural dimensions, the blades of these axial fans, as well as those of wind turbines, are considerably heavy. During operation, these blades are subjected to high radial and axial forces. This leads to structural challenges, significantly impacting the integrity and efficiency of the blades in both axial fans and wind turbines.

The blade profiles used in turbines and fans are similar to those used in aircraft wings. However, unlike in turbines and fans, there is no rotational movement in aircraft wings, which means they are straight without any twist.

Due to the convex curvature on the upper surface of the airfoil, air flows faster there than on the lower surface. This means the air speed is higher on the upper surface, resulting in lower pressure compared to the lower surface. Consequently, a directional pressure force occurs from the lower surface to the upper surface.

The wings are under the influence of two forces: The lift force acting perpendicular to the airflow, and the drag force parallel to the airflow. In turbines and fans, which involve rotational movement, blade profiles must be engineered according to relative speed. Unlike aircraft wings, where the angle of attack is consistent along the wing length, turbine and fan blades require varying angles of attack at each point. This necessitates a twist along the blade. Such a twist angle is variable, not a fixed value. When facing the turbine and fan, with both sets of blades rotating clockwise from left to right, the twist direction of turbine blades is opposite to that of fan blades. In turbines, the angle of attack of the rotor (propeller) relative to its rotation plane is twisted counterclockwise from the center to the blade tip , as seen from the blade tip, whereas in fans, the twist is applied in a clockwise direction. The twist direction in both turbines and fans also varies depending on their respective rotation directions..

In turbines and fans, the attack angles and degrees of twist of the blades have a significant impact on system efficiency and durability. Particularly in wind turbines and axial fans, the challenges arising from blade designs negatively impact the overall performance and sustainability of the systems. This results in composite forces that both create torque in the direction of rotation and also strain the blades in the opposite direction. This situation causes complex stresses along the blade root and length, and the drag forces work against the direction of rotation, reducing the efficiency of wind turbines and fans.

Patent no. US10094358B2 discloses double-bladed airfoil designs specifically for wind turbines, where higher aerodynamic efficiencies and equipment life can be achieved owing to the improved blade profile configuration according to the invention.

Although valuable solutions have been found in prior art applications, there remains a continual need for innovative and effective blade designs to further enhance the efficiency and applicability of aerodynamic and hydrodynamic systems. Further improvements in blade-profile design in critical energy conversion systems such as propellers, axial fans, and wind turbines will play a central role in technological advancements in these fields. Such improvements, by further increasing the efficiency of energy conversion, are set to offer significant innovations that will yield considerable economic and environmental benefits.

Brief Description of the Invention

The primary object of the present invention is to provide improved rotor blades that address the problems and demands in the aforesaid conventional applications, suitable for use effectively and advantageously in all propellers, fans and turbines.

Another object of the invention is to provide safer and more efficient operation of the blades by generating pressure forces in the opposite direction to the axial and radial forces occurring on the propeller, turbine, and fan blades..

Another important object of the invention is to provide hybrid blades, capable of incorporating single or multiple blade profiles and bladelets, for versatile applications in various aerodynamic and hydrodynamic systems introducing higher compatibility and performance efficiency in various system configurations.

Still, another object of the invention is to provide solutions for the noise problem caused by the fluid striking duct wall, for example, in fan blades, and the related issues that result in the fan motor to consume excessive energy. In order to achieve these objectives, the present invention provides an improved blade-profile assembly for use in fans, propellers, and turbines, comprising at least one blade connected to and extending outward from a central hub, which is a component of a rotor assembly, the blades being configured to rotate about the central axis of the rotor; the profile of each blade (10) comprising a lower surface, an upper surface, a trailing edge, and a leading edge.

In this blade-profile assembly, there is provided at least one bladelet arranged on at least one of the upper and lower surfaces of each blade, at a certain distance from the leading edge, positioned either perpendicularly or at a certain angle relative to the upper and/or lower surfaces of the blade, and perpendicularly or at a certain angle relative to the leading edge.

The blade-profile assembly can include a single blade or double blade profile, the latter of which has two blades on top of each other with a certain gap therebetween and can be formed in twin or various hybrid structures and profiles. In the double blade profile, a solid intermediate bladelet profile can be formed by combining the bladelet on the lower surface of the upper blade with the corresponding bladelet on the upper surface of the lower blade.

Furthermore, the preferred embodiment of the invention provides a hybrid blade that can consist of one or multiple profiles.

The profiles (side cross section) of said blade and bladelet both comprise, a leading edge surface part, a trailing edge surface part, an upper surface with at least two different geometric parts, and a lower surface with at least two different geometric parts. The upper surface of the profile comprises at least a convex part defined by a first ellipse and two different concave parts defined by second and third ellipses, respectively, along a chord direction thereof; while the lower surface comprises at least a convex part defined by a fourth ellipse and a concave part defined by a fifth ellipse, or a convex part defined by another ellipse.

The single or double blade profile includes a blade root for positioning on the hub. Once the blade root is attached to the hub, an angle of attack is set to the leading edge of blades, relative to the rotation plane. Each blade profile tapers from a larger cross-section at the part connected to the hub to a smaller cross-section at the blade tip, maintaining its form despite the change in size. Each blade profile has a radiused tip surface edge.

In this blade-profile assembly, the aerodynamic effect created by the indentation on the lower surface of the upper blade in double blades results in a decrease in air speed and an increase in pressure, thereby creating a pressure force in the direction of rotation and upward for the blade. This aerodynamic effect also occurs on the lower blade.

In a preferred embodiment, for example in axial fan applications, when the rotor rotates clockwise, the twist angle of the fan blades is set clockwise from the center to the blade tip. In another embodiment, for example in turbine applications, when the rotor rotates clockwise, the twist angle of the turbine blades is set counterclockwise from the center to the blade tip.

Thus, the invention provides a system generating pressure forces in turbine and axial fans in the opposite direction to the axial and radial forces, thereby reducing the axial and radial forces and ensuring that the blades operate both safely and more efficiently.

Brief Description of Figures

These and other objects, aspects, structural and characteristic features, advantages, and embodiments of the present invention will become more apparent from- and will be understood more clearly by reference to- the following detailed description and the associated figures.

Figure 1 is a front perspective view illustrating the main components of a preferred bladeprofile assembly according to one embodiment of the invention.

Figure 2a is a front perspective view illustrating the main components of another blade-profile assembly, with four profiles and each having two twin blades, according to another embodiment of the invention.

Figure 2b illustrates an enlarged view of the tip of a blade in Figure 2a.

Figure 3 is the front perspective view of a blade-profile assembly- with a multiple guiding bladelet configuration- in an alternative preferred embodiment of the invention. Figure 4 is a representative view of the twist angle in a single blade-profile assembly.

Figure 5 illustrates the angle of the leading edge of the fan blades in a double blade-profile assembly relative to the plane of rotation.

Figure 6a is a side cross-sectional view of a blade profile according to the preferred embodiment of the invention.

Figure 6b is a side cross-sectional view of a second blade profile according to another embodiment of the invention.

Figure 6c is a partial side cross-sectional view of a bladelet profile in a preferred double-blade- assembly.

While the invention is described herein by way of example for several embodiments and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the embodiments or drawings described. It should be understood, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used in this specification, expressions such as "may" are used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, words such as "include", "there is", "have", "contain" and "exist" also mean "comprise", but not limited to.

The components or elements corresponding to the reference numbers in the figures are listed below:

10 Single blade(s)

12 Second blade in a double-blade assembly

14 Blade tip (side profile cross-section)

14a Second blade tip (side profile cross-section)

20 Bladelet(s) 22 Solid intermediate bladelet profile combining two blades

24 Bladelet tips (upper profile cross-section)

30 Propeller/blade hub

40 Blade root

50 Blade twist angle

60 Angle of the blade leading edge with the plane of rotation

70 Radius blade tip

Y1 Leading edge surface of the blade profile

Y2 Upper second surface

Y3 Upper third surface

Y4 Upper fourth surface

Y5 Trailing edge surface of the blade profile

Y6 Lower first surface of the blade profile

Y7 Lower second surface

Y8 Lower third surface

Y9 Lower alternative first surface

Y10 Lower alternative second surface

Y11 Leading edge surface of bladelet profile

Y12 Upper second surface

Y13 Upper third surface

Y14 Trailing edge surface of the bladelet profile

Y15 Lower first surface of bladelet profile

Y16 Lower second surface

Y17 Lower third surface

Detailed Description of the Invention

Figure 1 illustrates a perspective view of the main components of a blade-profile assembly according to the invention, for use in fans and turbines, which are devices engineered to move fluid or to convert kinetic energy from a fluid into mechanical energy. In a preferred embodiment of the invention, the blade profile assembly comprises four single blades (10), and two pairs of (twin) bladelets (24) positioned vertically on both the upper and lower surfaces of each blade (10). The blades (10) are typically long, slender components that extend outward from a central hub (30). Each blade preferably has a twisted structure along its length. The side cross-section form of the blade profile is indicated by the reference number "14," and the cross-section form of the bladelet profile is indicated by the reference number "24".

In another embodiment of the invention, as shown in Figures 2a and 2b, the blade profile assembly preferably comprises four profiles (of double-blades) (10, 12), each profile having two twin blades, and each blade (10 or 12) consisting of two pairs of separate bladelets (20) positioned vertically on the upper and lower surfaces thereof (10 or 12), an opposing pair of which being an integrated intermediary bladelet (22) between the upper and lower blades. In an alternative embodiment, the bladelets (20, 22) can be positioned at a certain angle, either perpendicular or optimized relative to the blade surfaces and the leading edge.

Each blade is designed with a specific geometric shape, or profile structure, to efficiently interact with the fluid (e.g., air or water), referred to as "aerofoil" or "hydrofoil" depending on the fluid. Within the scope of the invention, this structure is generally termed a "blade profile," with the side cross-sectional view represented by reference numbers "14, 14a." (as seen from the blade end). Although the dimensions of this profile and cross-section (14, 14a) can vary along the length of the blade (10, 12), its form remains the same for the given blade. Similarly, the side cross-sectional view of "bladelet profile" is generally represented by reference number "24." The dimensions of this bladelet profile and cross-section (24) can vary depending on its position on the blade (10, 12), but its cross-sectional shape remains the same.

Figures 6a-6c show more detailed cross-sectional forms of the blades and bladelets, with their unique design and profile structure configured for directing air flow in fans for cooling or ventilation, and for converting fluid energy into mechanical energy in turbines. In fans, these blades function by pushing air in a certain direction, while in turbines, they capture the kinetic energy of the fluid and convert it into mechanical energy, which can then be transformed into electrical energy. For turbines operating in water or underwater vehicles, these blade profiles perform a similar function, directing water flow to optimize energy production and movement efficiency.

As shown in Figure 6a, a blade profile (14) comprises a leading edge surface part, a trailing edge surface part, an upper surface with three different geometric parts, and a lower surface with three different geometric parts. In a preferred arrangement, the upper surface of this profile includes, relative to the blade cord, at least a convex part (Y2) defined by a first ellipse and two different concave parts (Y3, Y4) defined by second and third ellipses, respectively. The lower surface includes, relative to the blade cord, at least a convex part (Y6) defined by a fourth ellipse, a concave part (Y7) defined by a fifth ellipse, and a convex part (Y8) defined by a sixth ellipse.

In other words, the blade profile (14) shown in Figure 6a, has a leading edge surface part (Y1) to meet incoming air flow, for example in turbines. Two successive different upper surfaces (Y2, Y3) facilitate the generation of lift force as the blade passes over the air flow. In fan blades, the curvature between these points, which sweeps the fluid, indicates an optimized convexity for aerodynamic performance. The maximum length part (Y4) is critical for the structural integrity of the profile. The narrowing trailing edge surface part (Y5) minimizes turbulence. Successive lower surface parts (Y6, Y7, Y8) are formed to complement the upper surface to promote effective lift. The lower surface completes reaching the trailing edge with a transformation from convex to concave, which affects the pressure distribution, in the first two surface sections (Y6 and Y7), and again with a slight convex transition (Y8).

In another embodiment, the blade profile form shown in Figure 6b, differing only on the lower surface (Y9, Y10), presents a more linear contour compared to the previous blade profile (of Figure 6a). Figure 6c shows a partial perspective view of the profiles of four separate bladelets (20) in the double blade (10, 12) profile, where all bladelets on the first and second blades have the same profile cross-section. Despite the apparent size differences, the upper profile cross section (24) of the vertical bladelet (20) arranged on the first blade (10) is notably very similar in shape to the upper profile cross section (14) of the blade (10) shown in Figure 6a. Other airofoils with different side cross section (24) can also be used for the bladelet embodiments.

Figure 3 shows a front perspective view of a hybrid blade and bladelet arrangements with guiding features in an alternative preferred embodiment according to the invention. There are provided three pairs of bladelets (20) on each blade (10, 12) and two pairs of opposing bladelets between the blades (10, 12) are combined and form two integrated solid intermediate bladelets (22), close to the blade tips. Here, the lower blade (10) and upper blade (12) are not twin but have different blade profile cross-sections (Figures 6a and 6b).

The number and position of the bladelets (20) may vary depending on the rotor speed and blade length. Thus, bladelets (20) can be located on both surfaces of the blade (10, 12) or on one surface only. In a preferred embodiment, the blade root (40) is inserted between the caps in the hub (30) and secured with U bolts after giving the blade a certain angle of attack from the blade tip (Figure 1, Figure 4). The hub is then fixed to the reducer shaft, motor shaft, or if driven by belt and pulley, to the pulley shaft using a keyed tube.

The blades are designed based on reference values such as rotation speed, air speed and air flow rate, taking into account the direction of rotation. That is, the change in the angle of attack (twist, Figure 4) along the blade is calculated, and accordingly, solid modeling is performed, followed by model manufacturing. By taking a mold from the model, the target products are produced in the mold, preferably with composite material, to ensure that all blades are the same size.

The operation of the blade profile assembly of the present invention will be described using an axial fan example. When the electric motor rotates the hub (30), moving the blades (10, 12), and the blades (rotor) start rotating, the following aerodynamic events occur according to principles of fluid mechanics:

As the fan blade (10) rotates, it passes through the stagnant fluid (air). In the double (twin) blade (10, 12) profile, air at the leading edge Y1 of both blade profiles (14, 14a) first contacts the Y2 surface, then the Y3 surface, and finally the Y4 surface. Similarly, air at the leading edge Y1 first contacts the Y6 surface, then the Y7 surface, and finally the Y8 surface. As the blade rotates, air on the Y2, Y3, and Y4 surfaces is swept and leaves the blade in the direction of the twist angle (50), thereby imparting motion to the fluid. On the other side, the fluid slides along theY6 surface and reaches the Y7 surface. The Y7 surface is concave towards the blade cord. In this area of the Y7 surface, the fluid expands, slowing down and increasing pressure. The fluid then moves from the Y8 surface to the Y5 trailing edge. Similarly, the air coming from the Y4 surface reaches the Y5 trailing edge and leaves the blade. The Y2 and Y6 surfaces are convex relative to the blade cord, creating a hump where the fluid flows fast and the pressure drops. Pressure forces from the high pressure on the Y7 surface to the low pressure on the Y2 and Y6 surfaces are created. These pressure forces create directional resultant forces on both the Y1 leading edge and the Y2 surface. The composite pressure force towards the Y1 surface creates an aerodynamic force in the direction of blade rotation, reducing the energy used by the rotor. The resultant forces occurring towards the Y2 and Y3 surfaces create an upward force resultant on the blade, thereby reducing the axial forces of the blade. This also reduces the stresses on the blade root (40) caused by the weight of the blade and axial forces while the rotor is operating, thereby extending the life of the blade.

The aerodynamic phenomenon occurring in the hybrid blade, which is another embodiment of the invention, is the same as in the twin profile above, but the Y9 and Y10 surfaces in the lower profile are convex (Figure 6b). The choice between a hybrid profile and a twin profile depends on the size of the blade. Twin profiles are used in systems with high-pressure differences, while hybrid profiles are used where high flow rates are desired.

In these arrangements, both the twin-profile blades and the hybrid-profile blades have their leading edges positioned at an angle (60) relative to the plane of rotation (Figure 5). This is to change the direction of the fluid flowing out of the rotor center at an angle due to the twist angle (50) (Figure 4) and to allow the fluid to enter the duct wall at a lower angle.

On the other hand, regarding the bladelet (20, 22) arrangements as the pressure force and flow guiding components in the twin and hybrid profiles function as follows:

The guiding bladelets (20, 22) having the form of the twin blade profile (10) (as illustrated in Figure 6) are arranged on the upper and lower surfaces of the axial fan blades at a certain height, preferably perpendicular and without twist. The number of bladelets varies depending on the length of the blade. The bladelet (20) beneath the upper blade and the bladelet (20) on top of the lower blade are combined (22). Thus a more rigid, complete and effective structure is obtained by connecting the lower and upper blades (10, 12) to each other. The angle of attack is determined by the circumferential speed and direction at the point where the bladelet is positioned. Different blade profiles may also be used. When the rotor rotates, the fluid swept from the surfaces of the axial fan blades (10, 12) exits outward from the rotor center at an angle due to the twist. This angled outflow (air) hits the duct walls, creating noise and leading to loss of efficiency. Some of this effect was eliminated by the angle given to the leading edge of the blades and the rotation plane.

Due to the Y11 surface of the bladelet (20) positioned perpendicular to the surfaces of the axial fan blades (10, 12), the fluid flowing from the fan blade surfaces is directed partly to Y12 surface and the rest to Y15 surface. The fluid leaves the bladelet after moving from surface Y12 to Y13, and then to Y14. On the other side, the fluid coming to Y15 surface passes through surfaces Y16 and Y17 and leaves the bladelet from Y14 surface. Y12 and Y15 surfaces are convex, while Y16 surface is concave. The fluid speeds up and pressure drops on surfaces Y12 and Y15. Since Y16 surface is concave, it causes an expansion, slowing the fluid and increasing pressure. A pressure force is created from the high pressure on Y16 towards the low-pressure areas on Y12 and Y15. Resultant pressure forces directed to the rotor center occur on the Y12 surface. Additionally, on surface Y15, pressure forces occur in the direction of blade rotation. Since the resultant pressure forces are towards the center of the rotor, they reduce the centrifugal force by acting in the opposite direction to the centrifugal force. Meanwhile, Meanwhile, the fluid coming on the bladelets is directed away and prevented from hitting the duct wall, thus eliminating noise and reducing energy consumption. The fan blades feature a radiused edge (70) at their tips. This radius (70) is the arc from the center to the radius of the blade's tip rotation circumference. Thus, no air blockage occurs between the duct and the fan tip.

In cooling towers with small diameters operating at low flow and pressure, it is possible to use one blade of the twin blades, for example. The rotor designed in this way is intended for use in narrow spaces. The same aerodynamic principles apply to this blade as well. The same twin and hybrid blades can function as turbine blades with the twist angle being given exactly the opposite. Again, the same aerodynamic principles apply as in the fan blades, increasing the turbine's efficiency and reducing the axial and radial forces acting on the blades.

All these blades can be manufactured from materials such as wood, aluminum, metal, and alloys, as well as composite materials, providing ease of manufacturing. In this specification, the expressions "arrangement", "configuration", "embodiment"" or

"application," qualified by "one," "another," or "other," are used interchangeably. These expressions do not necessarily refer to the same arrangement, and certain features, structures, or characteristics mentioned in one may be combined with those mentioned in another where appropriate.

Similarly, the descriptions made with reference to specific elements in the figures, such as the top and bottom of the profile or the position and placement of the blade and bladelet, are only for ease of understanding and should not be considered limiting to the scope of the invention. As the person skilled in the art would readily understand, these can vary depending on the axial, vertical, or angled placement of a blade, for example. Similarly, individual examples of fans, turbines, or propellers with various configurations serving different purposes should not be considered limiting to the scope of the invention, as the main aspect of the invention is its distinctive blade and bladelet structure and profile arrangement, adaptable to all conveniently.

Claims

1. A blade-profile assembly for use in fans, propellers and turbines, comprising at least one blade (10) connected to and extending outward from a central hub (30), which is a component of a rotor assembly, the blades being configured to rotate about the central axis of the rotor; the profile of each blade (10) comprising a lower surface, an upper surface, a trailing edge, and a leading edge; characterized by comprising; at least one bladelet (20) arranged on either or both the upper and lower surfaces of each blade (10), positioned at a certain distance from the leading edge.

2. The blade-profile assembly according to claim 1, characterized in that the position of said bladelet (20) is either perpendicular or at a certain angle relative to the upper and/or lower surfaces of the blade (10), and perpendicular or at a certain angle relative to the leading edge.

3. The blade-profile assembly according to the claim 1 or 2, characterized by comprising a double blade profile having an upper blade (10) with a lower surface and a lower blade (12) with an upper surface, the bladelet (20) on the lower surface of the upper blade (10) being aligned and combined with the corresponding bladelet (20) on the upper surface of the lower blade (12), together forming a solid bladelet intermediate profile section (22) therebetween.

4. The blade-profile assembly according to any one of the preceding claims, characterized in that the profile (14, 14a) of the blade (10, 12) comprises a leading edge surface part (Y1), a trailing edge surface part (Y5), an upper surface (Y2, Y3 and/or Y4) consisting of at least two different geometric parts, and a lower surface (Y6, Y7, Y8 or Y9, Y10) consisting of at least two different geometric parts.

5. The blade-profile assembly according to claim 4, characterized in that the upper surface of the profile (14, 14a) of the blade (10, 12) comprises at least a convex part (Y2) defined by a first ellipse and two different concave parts (Y3, Y4) defined by second and third ellipses, respectively, along a chord direction thereof; and that the lower surface of the profile (14, 14a) comprises at least a convex part (Y6 or Y9) defined by a fourth ellipse and a concave part (Y7) defined by a fifth ellipse and/or a convex part (Y8 or Y10) defined by another ellipse.

6. The blade-profile assembly according to any one of the preceding claims, characterized in that the profile (22, 24) of the bladelet (20) comprises a leading edge surface part (Y11), a trailing edge surface part (Y14), an upper surface (Y12, Y13) consisting of at least two different geometric parts, and a lower surface (Y15, Y16, and/or Y17) consisting of at least two different geometric parts.

7. The blade-profile assembly according to any of the preceding claims, characterized in that said single blade (10) or double-blade profile (10, 12) comprises a blade root (40) to be connected to said hub (30).

8. The blade-profile assembly according to any of the preceding claims, characterized by the blades (10, 12) having an angle (60) between the leading edge of the blade and the plane of rotation, following the attachment of the blade root (40) to the hub (30)

9. The blade-profile assembly according to any of the preceding claims, characterized in that the profile (14, 14a) of the blade (10, 12) tapers from a larger cross-section at the part connected to the hub (30) via the blade root (40) to a smaller cross-section at the tip where the blade extends outward.

10. The blade-profile assembly according to any of the preceding claims, characterized in that each blade (10, 12) has a radiused tip surface edge (70).

11. The blade-profile assembly according to any of the preceding claims, characterized in that when the rotor rotates clockwise for axial fan applications, the fan blades (10, 12) have a twist angle (50) in a clockwise direction from the center to the blade tip.

12. The blade-profile assembly according to any of the preceding claims, characterized in that when the rotor rotates clockwise for turbine applications, the turbine blades (10, 12) have a twist angle counterclockwise from the center to the blade tip.

13. The blade-profile assembly according to any of the preceding claims, characterized in that the blade profile is manufactured from materials selected from the group consisting of composite materials, wood, aluminum, iron or their alloys.