[0001] This patent application claims the priority of the French patent application FR 19/09335 filed on August 222020, which is incorporated herein by reference.

Domain of the invention

[0002] present invention relates to turbine, propeller and fan blades and similar devices that are used to move a fluid medium, to move in a fluid medium, or to be moved by a fluid medium.

Background of the invention

[0003] The propellers are known from hundreds of years and are used in many different ways.

[0004] A propeller blade (airplane or ship), rotor (helicopter) or wind turbine is a bearing surface rotating about an axis. It is an aerodynamic or hydrodynamic device intended to transform a motive energy in acceleration of the fluid in which it moves or conversely to transform the energy of displacement of the fluid.

[0005] In marine, aviation and wind uses; the propeller consists of a minimum of one single blade up to many blades joined by the central part called hub. It behaves like a wing whose aerodynamic force decomposes in torque. The blade end has a higher linear speed than the blade sections, more in the center, it is necessary to distribute the traction force without deformation of the hub.

[0006] A typical wind turbine is shown in figures 1 and 2, wherein the rotor consists of three blades (5) joined by the hub (4), which rotor is hold to the nacelle (3). Both rotor and nacelle (3) are on the top of a mast (1) fixed on the ground (1). Wind turbines (or propellers) usually feature a hub cover or “nose”.

[0007] Now, the current rotors are fragile, noisy, complex to produce, costly and not that safe.

Summary of the invention

[0008] The inventor has elaborated a new rotor design, made of one single piece having two distinct areas -i.e. a passive one and an active one-, which is efficient, silent, safe and low cost. [0009] A two-bladed axial flow fan rotor consisting of a unique diametral member having a constant concavo-convex transverse curvature throughout the diametral of the rotor is disclosed in patent GB 876852. Now, the concavo-convex transverse curvature includes the central or hub portion (8) thereof.

[0010] As compared to this rotor, the rotors of the invention are solid and simple to produce.

[0011] Moreover, the rotor of the invention provides good aerodynamic performance. It works like two parallel rotors, yet perfectly balanced and synchronized.

[0012] Accordingly, a first object of the invention is directed to a rotor comprising:

[0013] 1) at least one rectangular piece (6) having:

[0014] ο a length (L) between 2 and 8 times its width (W);

[0015] ο an opening (7) at its center;

[0016] ο a central or hub portion (8) surrounding the center opening (7), having a substantially flat surface; and

[0017] ο two similar, but oppositely pitched, blade portions (9) on either side of the central portion;

[0018] 2) at least one assembly part; and

[0019] 3) at least one spacer;

[0020] Wherein said rectangular piece (6) comprises two mounting strips (10), which are:

[0021] ο on both sides of the central opening (7) of the piece;

[0022] ο both rectangular;

[0023] ο equidistant and parallel to the two long edges of the rectangular piece (6);

[0024] ο Equidistant from the central opening (7) and at a distance to the center of the rectangular piece (6) corresponding to at least one to five fold the central opening (7) diameter; [0025] ο both comprised in the central or hub portion (8) with one short edge of each mounting strip in the same plane space than the central or hub portion (8);

[0026] ο both mounting strips (10) surface forming an angle comprised between 5° to 30° with the central or hub portion (8) surface; and

[0027] ο both forward or both backward of the central or hub portion (8) surface;

[0028] Wherein the central or hub portion (8) has a diamond-shaped form of which:

[0029] ο the diagonals meet at the center of the rectangular piece (6),

[0030] ο two opposite summits are each in the middle of each of the two opposite long edges of the rectangular piece (6), and

[0031] ο the two other opposite summits are each in the middle of each of the two opposite short edges of the rectangular piece (6); or are each equidistant from the two long edges of the rectangular piece (6) and at the same distance from the middle of the nearest short edge of the rectangular piece (6), said same distance corresponding to 15% of the length (L) of the rectangular piece (6) or less, with a cut between each of these two summits and the middle of the nearest rectangular piece (6) short edge; preferably said cut is terminated near the central or hub portion (8) by a clearance hole (so as to prevent cracking induced by the vibration), whereas the two angles generated by the cut within the short edges of the rectangular piece (6) are also preferably rounded;

[0032] Wherein each of the two blade portions (9) is composed of two surfaces (11):

[0033] ο a forward surface, which is forward of the central or hub portion (8) surface;

[0034] ο a backward surface, which is backward of the central or hub portion (8) surface;

[0035] ο each of these surfaces (11) having an angle comprised between 5° to 30° with the central or hub portion (8); and

[0036] ο each of them sharing a side with the diamond— shaped form of the central or hub portion (8); and [0037] Wherein said assembly part makes the connection between both mounting strips (10); and

[0038] Wherein said spacer is connected on the central opening (7), between the rectangular piece (6) and the assembly part.

[0039] A second object is directed to a rectangular piece (6) as defined previously.

[0040] A third object is directed to the use of a rotor as defined previously in a wind turbine, a boat propeller, a gyrocopter propeller, a mixing impeller or an airflow system fan which can be a comfort fan such as a ceiling fan, a ducted ventilation or extraction fan, an anti frost protection fan, etc.

[0041] A fourth object is directed to a wind turbine comprising such a rotor.

[0042] A fifth object is directed to a boat propeller comprising such a rotor.

[0043] A sixth object is directed to a plane propeller comprising such a rotor.

[0044] A seventh object is directed to a gyrocopter propeller comprising such a rotor.

[0045] A eighth object is directed to a mixing impeller comprising such a rotor.

[0046] A ninth object is directed to a ceiling fan comprising such a rotor.

[0047] Figures description:

[0048] The figure 1 shows a typical wind turbine.

[0049] The figure 2 shows a cut metal sheet so as to obtain a rotor of the invention.

[0050] The figure 3 shows the folding of such a metal sheet.

[0051] The figure 4 shows the obtained rectangular piece (6).

[0052] The figure 5 shows different assembly part designs.

[0053] The figure 6 shows a specific embodiment of a rotor according to the invention.

[0054] Detailed description

[0055] Preferably, the rectangular piece’s design is symmetrical with respect to its center. [0056] The rectangular piece (6) of the rotor is like that since it is the simplest to manufacture. Now, such rectangular piece (6) can have angles that have been rounded.

[0057] This rectangular piece (6) material has to support the rotor constraints.

[0058] The rectangular piece can correspond to a single piece or to associated pieces -e.g. 2 assembled pieces-. Preferably, the rectangular piece (6) is a single piece.

[0059] As such, it can be made of well known material such as metal (e.g. steel such as stainless steel), plastic, or composite (e.g. carbon fibers).

[0060] Now, it can be even envisaged to use wood (e.g. plywood).

[0061] Preferably, this rectangular piece (6) is made of metal, and most preferably, is made of steel -e.g. stainless steel-. In this case, this piece is made from a sheet metal by a simple pressing (e.g. using a hydraulic press) or preferably cut by laser, plasma, water jet or punching.

[0062] Now, if the rectangular piece (6) is made of plastic or composite, it can be 3D printed or molded.

[0063] The rectangular piece (6) thickness depends on its dimensions -i.e. length and width-, on the nature of its material, and also on its use. Preferably, the rectangular piece (6) will have a uniform thickness.

[0064] Advantageously, the rectangular piece (6) has a length (L) between 4 and 6 times its width (W), preferably about 5 times its width (W).

[0065] In relation with the central or hub portion (8), its surface is comprised between 50% and 75% of the two blades portions (9) surface, preferably between 55% and 65% of the two blades portions (9) surface.

[0066] Advantageously, this central or hub portion (8) is or can be covered with a spherical or conical nose.

[0067] Accordingly, the rotor comprises a nose covering the central or hub portion (8) surface, preferably at least 30% of its surface. This nose can be spherical or conical.

[0068] In relation to a turbine function, the nose will direct more flow to the two blade portions corresponding to the active surface. Now, and in relation to propeller function, the nose will help to avoid air turbulence. [0069] In relation with the opening (7) at the center of the rectangular piece (6), it is preferably a circular opening (7).

[0070] Depending on its use, the opening (7) at the center may not have the same function - i.e. rotation axis in case of propeller, or mounting element for wind turbines-.

[0071] The dimension of said opening (7) depends on the dimension of the rectangular piece (6), essentially its length. The longer the rectangular piece (6) is, the bigger diameter the central opening (7) has.

[0072] Typically, the central opening (7) diameter is comprised between 0.5 and 10 cm, preferably between 1 and 5 cm.

[0073] In relation with the two surfaces of each of the two blade portions (9), each of them has an angle comprised between 10° to 20° with the central or hub portion (8), preferably an angle of about 15° with the central or hub portion (8).

[0074] Preferably, each surface of the two blade portions (9) has a rounded angle at its summit corresponding to one of the summit of the rectangular piece (6).

[0075] Now, the rounded angles of the two trailing edges have preferably a significantly larger diameter than the one of rounded angles of the two leading edges.

[0076] Depending on the rotor use, the rectangular piece (6) may have specific characteristics.

[0077] In case of a wind turbine, the rectangular piece (6) must be as efficient as possible. The skilled person can simply determine the best thickness depending on the desired dimension for the wind turbine.

[0078] As an example, the thickness of a stainless steel is of at least 1 millimeter for a 0.25 meter rotor diameter, of at least 1.5 millimeter for a 0.5 meter rotor diameter, of at least 2 millimeters for 1 meter rotor diameter, and of at least 3 millimeters for a 2.5 meters rotor diameter.

[0079] In relation now with a boat propeller, the rectangular piece (6) must be more robust to resist water flow. Again, the skilled person can simply determine the best thickness depending on the desired dimension for this boat propeller.

[0080] As an example, the thickness of a stainless steel is of at least 4 millimeter for a 0.25 meter rotor diameter, of at least 5 millimeter for a 0.5 meter rotor diameter, of at least 6 millimeters for 1 meter rotor diameter, of at least 10 millimeters for a 2.5 meters rotor diameter.

[0081] For such a use, the central opening (7) allows both the passage of the propeller shaft and contributes to its association with it.

[0082] In relation with the two mounting strips (10), they are there to facilitate the rotor assembly and also contribute to the rotor’s rigidity.

[0083] Preferably, the mounting strips (10) are positioned in the diamond-shape form of the central or hub portion (8).

[0084] As mentioned previously, one short edge of each mounting strip (10) is in the same plane space than the central or hub portion (8); whereas the three other edges are not. In a sheet metal, the three other edges of the mounting strips (10) are cut by laser, plasma, water jet or punching. Then, the mounting strips (10) are bent on the short edge being in the same plane space than the central or hub portion (8) in order to obtain an angle comprised between 5° and 30° with the central or hub portion.

[0085] The two mounting strips (10) are equidistant from the central opening (7) and at a sufficient distance to the center of the rectangular piece (6) so as to preserve a central part of the central or hub portion (8) comprising the central opening (7) untouched, which central part is called the bridge (12). Preferably, two mounting strips (10) are at a distance to the center of the rectangular piece (6) corresponding to at least two to three fold the central opening (7) diameter.

[0086] The mounting strips (10) ideal width is between 15 and 25% of the width of the rectangular piece (6), and preferably about 20% of the width of the rectangular piece.

[0087] The assembly part can be made of well known material such as metal (e.g. steel such as stainless steel), plastic, or composite (e.g. carbon fibers). Now, it can be even envisaged to use wood (e.g. plywood).

[0088] Preferably, this assembly part is made of metal, and most preferably, is made of steel - e.g. stainless steel-. In this case, this piece is made from a sheet metal and cut by laser, plasma, water jet or punching. [0089] Now, if the assembly part is made of plastic or composite, it can be 3D printed or molded.

[0090] By connecting the two mounting strips, the assembly part contributes to the rigidity of the rotor of the invention.

[0091] Preferably, the assembly part comprises curvatures so as to match mounting strips angle.

[0092] If the assembly part is made of metal, said curvatures are obtained by folding the metal sheet.

[0093] The assembly part can be welded or screwed to the mounting strips (10).

[0094] In a preferred embodiment, the assembly part is screwed to the mounting strips (10).

[0095] In this case, the mounting strips (10) and the assembly part comprised mounting holes enabling their connection by screws or rivets.

[0096] Concerning the spacer connected on the central opening (7), between the rectangular piece (6) and the assembly part, it also contributes to the rigidity of the rotor of the invention.

[0097] Depending on the rotor use, the spacer can take different and distinct forms.

[0098] In case of a wind turbine, the spacer can be an electric generator. Now, the electric generator can be replaced by a transmission system that can operate a pump or another device.

[0099] In case of a propeller, such as a boat propeller, the spacer allows the passage of the propeller shaft and its association with the rotor of the invention. In this case, the spacer is a hollow cylindrical part. This spacer can be made of well known material such as metal (e.g. steel such as stainless steel), plastic, or composite (e.g. carbon fibers).

[0100] In a preferred embodiment, the spacer is screwed to the assembly part and to the rectangular piece (6), preferably to the bridge (13).

[0101] In this case, the assembly part and the rectangular piece (6), preferably the bridge (13), comprise mounting holes enabling the connection by screws to the spacer.

[0102] Now, the rotor design can be customized for some applications to integrate specific assembly features (assembly holes, etc.). [0103] An embodiment of the invention will now be described as a non-limiting example, with reference to the appended schematic drawings wherein:

[0104] Fig. 2 illustrates a 2D cutting plan of the rectangular piece on a metal sheet.

[0105] Figure 3 illustrates the folding of the metal sheet of figure 2

[0106] Figure 4 illustrate the obtained rectangular piece from the rotor of the invention.

[0107] The figure 2 illustrates the cuts that can be achieved on a rectangular piece (6) in order to obtain the bridge (12) and to prepare the two mounting strips (10) and also the surfaces corresponding to the central or hub portion (8) and each of the two surfaces (11) of each of two blade portions (9). The cuts of the mounting strips are preferably terminated by a clearance hole (so as to prevent cracking induced by the vibration).

[0108] This figure 2 also illustrate the drilling or cuts that can be achieved to obtain the central opening (7) and also the mounting holes (13).

[0109] The figure 3 illustrates the folds to be done on the piece of figure 2 so as to obtain a rectangular piece (6) according to the invention.

[0110] All of the surfaces (11) of the two blade portions (9) are folded with the same angle according to the dotted lines in figure 3 and in the direction indicated by the arrows. On this figure 3, 11a is folded upward, l ib downward, 11c upward, l id downward, whereas both mountings strip 10 are folded downward.

[0111] The direction of bending of the surfaces determines the rotation direction of the rotor (when the rotor is actuated by a fluid) or the direction of the generated flow (when the rotor is actuated by a motor). In the figure, the bending presented makes it possible to obtain a wind turbine with anti-clockwise rotation (observer facing the nose of the wind turbine) which will be in synergy with the Coriolis Effect in the northern hemisphere.

[0112] Both mounting strips (10) are folded downward with the same angle and according to the dotted lines in figure 3 and in the direction indicated by the arrows.

[0113] The figure 4 shows different views of the obtained rectangular piece of the invention.

[0114] The figure 5 different assembly part designs.

[0115] On the figure 6, the rectangular piece (6) is associated with the assembly part, which are both associated with a spacer corresponding to an electric generator. [0116] The performance of a 2.5 diameter rotor of the invention with a lkW generator is tested according to the guidelines disclosed in international standard IEC 61400-12-1. Those guidelines allow determining the power performance by two important factors which are the power curve and its estimated annual energy production (AEP).

[0117] The power curve is a powerful tool to estimate the power extraction. In fact, it enables to quantify the relation between the incoming wind and the output power of the wind turbine. Its value is obtained by collecting simultaneous measurements of wind speed and power output at the test site for a period that is long enough to establish a significant database over a range of wind speeds and under varying wind and atmospheric conditions.

[0118] Regarding the (AEP), it corresponds to the quantity of energy that can be produced during one year. Thus, it is also an important feature for economic considerations. Its value is obtained by applying the measured power curve to reference wind speed frequency distributions, assuming 100% availability.

[0119] In relation with the test equipment, a meteorological mast is necessary so as to measure wind speed and other parameters such as the wind direction, the temperature and the air pressure. This meteorological mast is located upwind the turbine, in the direction from which most valid wind is expected to come from. The height of the meteorological mast corresponds to the one of the wind turbine. It shall be positioned at a distance from the wind turbine of between 2 and 4 times the rotor diameter D of the wind turbine. In the present case, the meteorological mast is ideally located at 6.25 m from the wind turbine.

[0120] The test equipment also includes:

[0121] - a cup anemometer on the meteorological mast for measuring the wind speed. This cup anemometer is calibrated before and recalibrated after the measurement campaign.

[0122] - a reference anemometer on the meteorological mast in order to ensure that the primary anemometer does not change its calibration during the test.

[0123] - a wind vane for measuring the wind direction on the meteorological mast.

[0124] - an air temperature sensor on the meteorological mast.

[0125] - an air pressure sensor on the meteorological mast.

[0126] - an air humidity sensor on the meteorological mast.

[0127] - a lightning rode to protect the meteorological mast. [0128] - a data acquisition system is a digital system having a sampling rate per channel of at least 1 Hz. The calibration and accuracy of the data system shall be verified by injecting know signal at the transducer ends and comparing these inputs against the recorded readings.

[0129] - a power transducer for determining the output power by measuring the current and voltage on each phase. The accuracy of it shall meet the requirements of IEC 60688 and shall be class 0.5.

[0130] In relation with the measurement procedure, the obtained data are averaged over periods of 10 minutes. These averaged values are the ones used for the analysis, together with their corresponding standard errors..

[0131] The IEC power curve is then derived from the normalized values using so-called method of bins, i.e. the data is split into wind speed intervals of a width of 0.5 m/s each. For each interval i, bin averages of wind speed Vi and power output Pi are calculated.

[0132] For the power curve to be complete, or reliable, each bin must include at least 30 min of sampled data and the entire measurement must cover a minimum period of 60 h (requirements for small wind turbines).

[0133] Based on the IEC procedure, the AEP can be derived by integrating the measured power curve to a reference distribution of wind speed for the test site, assuming a given availability of the wind turbine. The AEP is a central feature for economic considerations.