Rotor for hydrokinetic turbine and respective hydrokinetic turbine

Abstract

Rotor (1 ) for hydrokinetic turbine (99), and relative hydrokinetic turbine (99), wherein the rotor (1 ) comprises a central shaft (2) and one or more blades (3) integral with the central shaft (2), wherein each blade (3) comprises a first end portion (31 ), adjacent to the central shaft (2), and a second end portion (32), opposite to the first end portion (31 ), wherein each blade (3) comprises a working surface (4) that develops at least at the second end portion (32) and is intended to be impacted by an operating fluid having an advancing direction (100) to generate a thrust on the blade (3), and wherein each blade (3) comprises a back portion (6) facing opposite to the working surface (4) and having a tapered development moving away from the working surface (4).

Description

[0001] DESCRIPTION

[0002] Title: ROTOR FOR HYDROKINETIC TURBINE AND RESPECTIVE HYDROKINETIC TURBINE

[0003] Technical field of the invention

[0004] The present invention relates to a rotor for a hydrokinetic turbine and a respective hydrokinetic turbine.

[0005] State of the art

[0006] In the context of electricity generation, hydrokinetic turbines are known, that is, devices structured to convert the kinetic energy of a flow of water, such as the flow of a river or the motion of waves or tides, into rotational mechanical energy. Such rotational mechanical energy is typically used to generate electricity, for example through a generator connected to the shaft of the turbine.

[0007] Summary of the invention

[0008] With the term "rotor" is meant the movable part, typically rotating around its own axis, of a driving machine, such as a hydrokinetic turbine.

[0009] With the terms "perpendicular" and "orthogonal" are meant respectively a substantial perpendicularity and a substantial orthogonality between two elements, comprising both the ideal case in which such elements are arranged with respect to each other to form a right angle, and more frequent cases in which the two elements are arranged with respect to each other to form an angle that deviates from the right angle (e.g. included in a range of ±15°, more preferably of ±10°, with respect to the right angle) but in any case in a way that is negligible or not relevant for the functioning of the present solution.

[0010] With the term "parallel" is meant a substantial parallelism between two elements, comprising both the ideal case in which such elements are arranged with respect to each other to form a null angle, and more frequent cases in which the two elements are arranged with respect to each other to form an angle that deviates from the null angle (e.g. included in a range of ±15°, more preferably of ±10°, with respect to the null angle) but in any case in a way that is negligible or not relevant for the functioning of the present solution.

[0011] The terms "radial" and "axial" are used with reference respectively to a direction perpendicular and to a direction parallel to the axis of rotation of the central shaft of the rotor.

[0012] The term "circumferential" is used with reference to an annular development centered on the axis of rotation of the central shaft of the rotor. In the aforementioned context of electricity generation, the Applicant has found that the known hydrokinetic turbines have certain drawbacks and / or can be improved in one or more aspects.

[0013] For example the Applicant has found that the known hydrokinetic turbines can be improved in terms of performance, for instance, in the efficiency of electric energy generation.

[0014] The Applicant has therefore addressed the problem of improving the performance of a hydrokinetic turbine, for example in terms of efficiency of electricity generation and / or output.

[0015] According to the Applicant the aforementioned problem is solved by a rotor for a hydrodynamic turbine, and a respective hydrokinetic turbine, in accordance with the appended claims and / or having one or more of the following features.

[0016] According to one aspect the invention concerns a rotor for a hydrokinetic turbine.

[0017] Preferably said rotor comprises a central shaft and one or more blades integral to said central shaft. Preferably each blade has development with at least one radial component with respect to said central shaft.

[0018] Preferably each blade comprises a first end portion, adjacent to said central shaft, and a second end portion, opposite to said first end portion along said development of said blade.

[0019] Preferably each blade comprises a working surface which develops at least in correspondence of said second end portion, said working surface being intended to be struck by an operating fluid having an advancing direction to generate a thrust onto said blade.

[0020] Preferably each blade comprises a back portion facing away from said working surface.

[0021] Preferably said back portion has tapered development moving away from said working surface.

[0022] According to another aspect, the invention concerns a hydrokinetic turbine comprising a support frame and the rotor according to the present invention rotatably fixed to said support frame.

[0023] Preferably said turbine further comprises means for generating electric energy (e.g. alternator) connected to said rotor for generating electric energy from a rotation of said rotor about an axis of said central shaft.

[0024] According to the Applicant, the working surface of each blade, intended to be struck by the operating fluid (e.g. a water flow) with a given advancing direction for generating a thrust on the blade, represents the blade surface portion which, through the interaction with the fluid, allows the blade to be set into rotation and consequently the central shaft around its own axis to produce rotational mechanical energy to be typically converted into electric energy.

[0025] In the use of a hydrokinetic turbine, therefore during the rotation of the rotor around the axis of the central shaft by the action of the moving operating fluid, the Applicant observes that the back portion of the blade represents a portion of the blade that contrasts, in general, the flow motion of the operating fluid, thereby opposing the rotation of the rotor. This occurs, for example, in the case of a rotor fully immersed in the fluid (e.g. immersed hydrokinetic turbines), wherein the back portion of the blade is necessarily moving, during the rotation of the rotor, with direction opposite to the motion direction of the operating fluid for at least a portion of rotation of the blade, or also in the case of a rotor only partially immersed (e.g. semi-immersed hydrokinetic turbines), wherein the back portion substantially represents the first portion of the blade to come into contact with the operating fluid during the descent of the blade into the fluid as a result of the rotation of the central shaft. Without wishing to be bound by any theory, the Applicant considers that in both of the aforementioned cases the back portion, by resisting the motion of the fluid, generates a counterthrust that opposes the desired rotation of the rotor, resulting, ultimately, in a decrease in the efficiency in the generation of electric energy.

[0026] According to the Applicant therefore the back portion having tapered development moving away from the working surface allows to obtain a profile having desired hydrodynamic characteristics and therefore capable of reducing the resistance that the back portion of the blade opposes to the fluid. In other words, the back portion with tapered development allows to realize a back edge capable of cutting the water in the aforementioned cases wherein the back portion is contrasting the flow of the fluid, and therefore of limiting the hydrodynamic resistance of the back portion of the blade.

[0027] In this way it is therefore possible to reduce the slowing effect of the rotor due to the motion of the blades when moving contrary to the direction of the fluid, improving the overall performance of the turbine, for example in terms of efficiency of generation of electric energy.

[0028] The present invention, in one or more of the aforementioned aspects, can comprise one or more of the following preferred features.

[0029] Preferably said central shaft comprises an axis, typically a central axis of symmetry of said central shaft and around which the central shaft rotates. Preferably said radial component od development of each blade is a main development component of each blade. In other words, each blade has main development along the radial direction. In this way, the interaction with the operating fluid is improved.

[0030] Preferably said working surface comprises at least one concave portion with concavity facing opposite to said advancing direction of the operating fluid. In the present context it is meant that the concavity of the concave portion of the working surface presents a direction opposite to the advancing direction of the fluid for at least one operational angular position (preferably a continuous range of operational angular positions) of the blade in its rotational trajectory around the axis of the central shaft during the rotation of the rotor, that is an angular position or range of angular positions in which the blade generates rotational mechanical energy under the action of the operating fluid. In this way the resistance to the fluid offered by the working surface is increased, to the benefit of the performance.

[0031] Preferably said concave portion comprises a first curvature along an axial direction. In other words the concave portion of the working surface presents a curvature moving parallel to the axial direction. In this way the interaction with the operating fluid is enhanced.

[0032] Preferably said concave portion comprises a second curvature along a radial direction. In other words the concave portion of the working surface presents a curvature (also) moving parallel to the radial direction, for example moving away from the central shaft. In this way the interaction with the operating fluid is enhanced.

[0033] Preferably said concave portion has constant section, more preferably with substantially C-shaped form, moving along a tract of generating line with curved form lying on a plane (substantially) perpendicular to said axial direction (that is to said axis of said central shaft). Preferably said substantially C-shaped section realizes said first curvature and said tract of generating line with curved form realizes said second curvature. Without wishing to be bound by any theory, the Applicant has found that such shape of the concave portion of the working surface allows to obtain desired characteristics of conversion of the force of the fluid into rotational mechanical energy.

[0034] Preferably said concave portion coincides with said working surface. In other words the concave portion of the working surface substantially entirely occupies the working surface. In this way the performance is further improved.

[0035] Preferably said working surface develops with continuity from said first end portion to said second end portion of said blade. In this way the entire radial development of the blade is exploited to generate mechanical energy, to the benefit of the performance.

[0036] Preferably said back portion is at least partially placed, more preferably (substantially) entirely, at said working surface. In this way the hydrodynamic profile of the blade is further improved.

[0037] Preferably said back portion develops with continuity from said first end portion to said second end portion of said blade. In this way, the hydrodynamic profile of the blade is further improved.

[0038] Preferably said tapered development of said back portion defines a back edge having development with at least one radial component. In this way it is suitably shaped according to the main development of the blade.

[0039] Preferably said back edge has main development along the radial direction. In this way the cutting effect of the back portion on the operating fluid is further facilitated.

[0040] Preferably each blade has a respective plane of symmetry arranged orthogonally to said axis of said central shaft. In this way the shape of the blade is highly rationalized.

[0041] Preferably a thickness of each blade measured between said working surface and said back edge has a first (monotonically) increasing trend up to a maximum moving along said radial direction from said first end portion of the blade. Preferably said thickness of each blade has a second (monotonically) decreasing trend moving along said radial direction from said maximum to said second end portion. In other words each blade presents a thickening at an intermediate portion thereof when moving radially along the development of the blade from the first end portion to the second end portion. In this way on one hand the structure of the blade is reinforced and on the other, in combination with the development with radial component of the back edge, a substantially pointed profile is realized with further improvement of the hydrodynamic characteristics of the back portion (to the advantage of even lower resistance of the blade to the fluid).

[0042] Preferably said maximum is located closer to said second end portion of said blade with respect to said first end portion. In other words the thickening of the blade is arranged closer to the free end of the blade. Without wishing to be bound by any theory, in this way the rotational inertia of the blade is improved, to the further benefit of the performance (e.g. rotational speed uniformity once a steady rotational speed is reached, even with potential variations in flow / speed of the fluid -within a certain limit-).

[0043] Preferably said rotor comprises a plurality of blades distributed along a whole useful axial development of said central shaft. In this way the arrangement is rational.

[0044] By "useful axial development" of the shaft, it is meant an axial length of the shaft disposed directly in correspondence with the operating fluid (i.e. the length of the shaft that can be used to position blades). In other words, any extensions of the central shaft beyond the channel / river opening on which the turbine is arranged are not considered.

[0045] Preferably said plurality of blades comprises two or more groups of blades.

[0046] Preferably each group of blades comprises a respective plurality of blades arranged mutually in sequence along said axial direction, more preferably for substantially said entire useful axial development of said central shaft.

[0047] Preferably each group of blades is angularly equispaced from remaining groups of blades of said plurality of blades with respect to said axis of said central shaft. In other words, in the presence of two groups of blades, they are arranged with an angle between them of approximately 180°, in the case of three groups of blades, the mutual angle is approximately 120°, and so on. In this way the weight of the blades is homogeneously distributed along the shaft and / or the tracts of the rotational trajectory of the rotor in which there are blades operating in the fluid (i.e. blades generating mechanical rotational energy) are rationally distributed.

[0048] Preferably said respective plurality of blades of each group of blades is arranged along said axial direction following a portion of line having development (along said shaft) with at least one circumferential component. In other words the blades of each group are arranged on the shaft so as not to be mutually aligned in a purely axial manner, but progressively more offset with respect to said direction (e.g. taking the first blade of a given group as reference). In this way the performance of the turbine is further improved since it is possible to ensure that there is substantially always at least one blade operating in the fluid during the rotation of the rotor.

[0049] Preferably said portion of line has a helical development with respect to said axis of said central shaft. Such development has proven to be highly advantageous for achieving what is described above.

[0050] Preferably said helical development has constant pitch. In this way, the construction of the rotor is simplified.

[0051] By "pitch of the helical development" is meant a distance between two distinct points belonging to the helical development and aligned with each other along a same generating line.

[0052] Preferably a pitch of said helical development is greater than or equal to 2.5, more preferably greater than or equal to 3, times said useful axial development of said central shaft, and / or less than or equal to 5.5, more preferably less than or equal to 5, times the useful axial development of said central shaft. In this way, the efficiency of energy generation of the rotor is further improved.

[0053] Preferably (for each group) a ratio between an axial distance between consecutive blades belonging to the same group (e.g. taken at the center of the blade) and said useful axial development of the central shaft is greater than or equal to 8%, more preferably greater than or equal to 10%, and / or less than or equal to 20%, more preferably less than or equal to 15%. In this way the efficiency of energy production of the rotor is improved by optimizing the tightness of the blades with respect to the useful development of the central shaft, for example by avoiding blades that are either too loosely spaced (inefficient) or too tightly spaced (also inefficient as they generate a blockage to the operating fluid that would not impact the next blade group in the desired manner).

[0054] Preferably a ratio between an axial width of each blade (e.g. of said working surface, more preferably of the concave portion) and said useful axial development of the central shaft is greater than or equal to 3%, more preferably greater than or equal to 4%, and / or less than or equal to 7%, more preferably less than or equal to 6%. In this way the efficiency of the rotor is improved, for example by avoiding blades that are too thin (not sufficiently robust, inefficient) and blades that are too wide (which can create fluid blocking effects in a manner similar to what is described above).

[0055] Preferably (for each group) a ratio between an axial distance between consecutive blades of the same group and a radial height of the blade is greater than or equal to 20%, more preferably greater than or equal to 25%, and / or less than or equal to 40%, more preferably less than or equal to 35%. In this way the efficiency of energy production of the rotor is improved, for example by optimizing the draft of the blade while reducing the perturbative effects in the fluid that one blade can generate on adjacent blades.

[0056] Preferably said turbine is a river turbine.

[0057] Preferably said turbine is with axis horizontal and transverse (with respect to the advancing direction of the operating fluid).

[0058] Preferably said support frame is shaped so as to be able to move said rotor with respect to said operating fluid along a direction having at least one vertical component, more preferably a purely vertical direction. To this end, the support frame can for example comprise lifting means (e.g. hydraulic pistons, etc.) in order to lift vertically the rotor with respect to the fluid. In this way it is possible to vary the height of the rotor and / or the degree of immersion thereof, for example in response to variations in the flow rate of the operating fluid (typically confined in a riverbed or artificial channel), even to the extent of being able to completely remove the rotor from the fluid, for example for avoiding possible damage in case of floods and / or inundations due to impacts with debris carried by the operating fluid.

[0059] In one embodiment said support frame is rigidly fixed to the ground.

[0060] Preferably the support frame comprises a first portion.

[0061] In one embodiment the support frame coincides with said first portion.

[0062] Preferably said rotor is rotationally fixed to said first portion (only) at a first axial end of said central shaft.

[0063] In one embodiment said support frame is floating in said operating fluid.

[0064] Preferably said support frame comprises a second portion.

[0065] In one embodiment said rotor is rotationally fixed to said second portion at a second axial end of said central shaft opposite to said first axial end.

[0066] Brief description of the Figures

[0067] Figure 1 schematically shows a perspective view of a hydrokinetic turbine according to the present invention; figure 2 schematically shows a further perspective view of the turbine of figure 1 ; figure 3 shows a top view of the turbine of figure 1 , figure 4 shows a detail of the turbine of figure 1 .

[0068] Detailed description of some embodiments of the invention

[0069] The characteristics and advantages of the present invention will be further clarified by the following detailed description of some embodiments, provided by way of example and not limitation, of the present invention, with reference to the accompanying figures.

[0070] In the figures with the number 99 a hydrokinetic turbine according to the present invention is globally indicated.

[0071] By way of example the turbine 99 comprises a support frame 90 and a rotor 1 for hydrokinetic turbine according to the present invention.

[0072] By way of example the rotor 1 is rotationally fixed to the support frame 90.

[0073] By way of example the turbine 99 is a river turbine with axis horizontal and transverse. In other words an axis of rotation of the rotor 1 is arranged horizontally and transversely to an advancing direction 100 of an operating fluid (not shown) flowing and acting to rotate the rotor 1 .

[0074] By way of example the axis of rotation of the rotor 1 coincides with an axis of a central shaft 2 of the rotor, that is typically a central symmetry and rotation axis of the central shaft. For example, as shown in the figures, the hydrokinetic turbine 99 can be installed at a channel, either artificial or natural, within which the aforesaid operating fluid, typically water, flows.

[0075] By way of example the support frame 90 is stably and rigidly fixed to the ground and comprises a first portion 91 and a second portion 92 arranged on opposite sides of the central channel.

[0076] By way of example the rotor 1 is rotationally fixed to both the first 91 and the second portion 92 of the support frame 90, at respectively a first and a second end portion of the central shaft 2 of the rotor 1 , axially opposite to each other (that is arranged on opposite sides along an axial direction 200 parallel to the axis of the central shaft 2).

[0077] In one embodiment, not shown, the support frame can be entirely or partially floating in the operating fluid. For example only one, or both the first 91 and the second portion 92 of the support frame can be floating (the other being possibly fixed to the ground).

[0078] In one embodiment, not shown, the support frame can consist of only a single portion coinciding with one between the first and the second portion. Such single portion can be fixed to the ground or floating.

[0079] Exemplarily the support frame 90 has a lattice structure, each portion 91 , 92 being formed by a pair of perforated plates joined to each other by a plurality of rigid rods.

[0080] Exemplarily each of the first portion 91 and second portion 92 has a concave shape with concavity facing downward (e.g. towards the ground).

[0081] Exemplarily the support frame 90 is shaped to be able to move the rotor 1 with respect to the operating fluid along a vertical direction. To this end the support frame 90 can for example comprise, typically at each of the first 91 and second portion 92, lifting means (not shown, e.g. hydraulic pistons, etc.) to be able to vertically lift the rotor 1 with respect to the operating fluid.

[0082] Exemplarily the hydrokinetic turbine 99 also comprises means for generating electric energy (not shown, e.g. comprising at least one generator) connected to the rotor 1 for generating electric energy from the rotation of the rotor 1 around an axis (e.g. central symmetry axis) of the central shaft 2.

[0083] Exemplarily the rotor 1 comprises the central shaft 2 and a plurality of blades 3 integral with the central shaft 2.

[0084] Exemplarily each blade 3 has main development along a radial direction 300 with respect to the central shaft 2. Exemplarily each blade 3 has a respective symmetry plane (not shown) disposed orthogonally to the axis of the central shaft 2. Exemplarily each blade 3 comprises a first end portion 31 , adjacent to the central shaft 2, and a second end portion 32, opposite to the first end portion 31 along the main development of the blade 3.

[0085] Exemplarily each blade 3 comprises a working surface 4 which develops at least at the second end portion 32, the working surface 4 being intended to be struck by the operating fluid having an advancing direction to generate a thrust on the blade 3.

[0086] Exemplarily the working surface 4 comprises at least one concave portion 5 with concavity facing opposite to the advancing direction 100 of the operating fluid. In the present context and in the figures it is intended that the concavity of the concave portion 5 of the working surface 4 faces opposite to the advancing direction of the operating fluid for a continuous interval of operative angular positions of the blade 3 in its rotational trajectory around the axis of the central shaft 2 during the rotation of the rotor, wherein said interval of angular positions is one in which the blade generates mechanical rotational energy under the action of the operating fluid. Exemplarily such interval of operative angular positions coincides with an interval of angular positions of the blade when the blade is arranged substantially at a lower height than a height of the central shaft.

[0087] Exemplarily the concave portion 5 coincides with the entire working surface 4 and comprises a first curvature along the axial direction 200 and a second curvature along a radial direction 300. In other terms the concave portion 5 of the working surface 4 (that is exemplarily the entire working surface) exemplarily presents a first curvature when moving parallel to the axial direction 200 and a second curvature also when moving parallel to the radial direction 300, for example moving away from the central shaft.

[0088] More in detail the concave portion 5 exemplarily has constant section with substantially C-shaped form moving along a tract T of generating line (figure 4, in dashed line) with curved form lying on a plane (not shown) perpendicular to the axis of the central shaft 2. Exemplarily the section with substantially C-shaped form realizes the above-mentioned first curvature and the tract T of generating line of curved form realizes the above- mentioned second curvature.

[0089] Exemplarily the working surface 4 develops with continuity from the first end portion 31 to the second end portion 32 of the respective blade 3.

[0090] Exemplarily each blade 3 further comprises a back portion 6 facing in the opposite direction with respect to the respective working surface 4.

[0091] Exemplarily the back portion 6 is arranged substantially entirely at the working surface 4, more in detail developing exemplarily continuously from the first end portion 31 to the second end portion 32 of the respective blade 3.

[0092] Exemplarily the back portion 6 has tapered development moving away from the working surface 4 of the respective blade 3.

[0093] Exemplarily the tapered development of the back portion 6 defines a back edge 61 having development with at least one radial component. Exemplarily the back edge 61 has main development along the radial direction 300.

[0094] Exemplarily a thickness of each blade 3 measured between the working surface 4 and the back edge 61 has a first increasing trend up to a maximum 62, moving along the radial direction 300 from the first end portion 31 of the blade 3, and a second decreasing trend moving along the radial direction 300 from the maximum 62 to the second end portion 32. In other words each blade comprises a thickening at an intermediate portion thereof moving radially along the development of the blade 3 from the first end portion 31 to the second end portion 32.

[0095] Exemplarily the maximum 62 is arranged in a position closer to the second end portion 32 of the respective blade 3 with respect to the first end portion 31 . In other words the thickening of the blade is arranged closer to the free end of the blade 3 (see for example figure 4).

[0096] Exemplarily the plurality of blades 3 of the rotor 1 is distributed along an entire useful axial development SA of the central shaft 2.

[0097] Exemplarily the plurality of blades 3 is constituted by four groups G of blades 3, each group G of blades 3 comprising exemplarily a respective plurality of blades 3 arranged in sequence with one another along the axial direction 200 for substantially the entire useful axial development SA of the central shaft 2.

[0098] Exemplarily each group G of blades 3 is angularly equispaced from the remaining groups G of blades 3 of the plurality of blades with respect to the axis of the central shaft 2. In detail the four groups G of blades 3 are exemplarily arranged with an angle between them of about 90° (centered on the axis of the central shaft 2).

[0099] Exemplarily the respective plurality of blades of each group G of blades 3 is distributed along the axial direction 200 following a portion of line L (shown in figure 2 for only one group G of blades) having a development with at least one circumferential component. More in detail the portion of line L exemplarily has a constant-pitch helical development (not shown) around the axis of the central shaft 2.

[0100] Exemplarily the pitch of the helical development of the portion of line L is approximately 4 times the useful axial development SA of the central shaft 2.

[0101] Exemplarily a ratio between an axial distance D between consecutive blades 3 belonging to the same group G (e.g. taken at the center of the blade) and the useful axial development SA of the central shaft 2 is approximately 12%, and a ratio between the axial width W of each blade 3 (e.g. of the concave portion) and the useful axial development SA of the central shaft 2 is approximately 5%.

[0102] Exemplarily a ratio between the axial distance D between consecutive blades of the same group G and a radial height H of the blade is approximately 33%.

[0103] In use the hydrokinetic turbine 99 allows the production of electric energy from the mechanical energy of rotation of the rotor 1 thanks to the action of the moving operating fluid on the blades 3 of the rotor 1 . Exemplarily the turbine 99 is operatively of the semisubmerged type, meaning that the rotor 1 is not entirely submerged in water but only partially, limited to the respective blades 3 when they are in a substantially lower portion of their respective rotational trajectory around the axis of the central shaft 2.

Claims

CLAIMS1 . Rotor (1 ) for hydrokinetic turbine (99), said rotor (1 ) comprising a central shaft (2) and one or more blades (3) integral with said central shaft (2), wherein each blade (3) has development with at least one radial component with respect to said central shaft (2), wherein each blade (3) comprises a first end portion (31 ), adjacent to said central shaft(2), and a second end portion (32), opposite to said first end portion (31 ) along said development of said blade (3), wherein each blade (3) comprises a working surface (4) which develops at least at said second end portion (32), said working surface (4) being intended to be struck by an operating fluid having an advancing direction (100) to generate a thrust onto said blade (3), wherein each blade (3) comprises a back portion (6) facing away from said working surface (4), and wherein said back portion (6) has tapered development moving away from said working surface (4).

2. Rotor (1 ) according to claim 1 , wherein said radial component of development of each blade (3) is a main development component of each blade (3), and wherein said working surface (4) comprises at least one concave portion (5) with concavity facing opposite to said advancing direction (100) of the operating fluid.

3. Rotor (1 ) according to claim 2, wherein said concave portion (5) comprises a first curvature along an axial direction (200) and a second curvature along a radial direction (300).

4. Rotor (1 ) according to claim 2 or 3, wherein said concave portion (5) has constant section with substantially C-shaped form moving along a tract (T) of generating line with curved form lying on a plane substantially perpendicular to said axial direction (200).

5. Rotor (1 ) according to any one of claims from 2 to 4, wherein said concave portion (5) coincides with said working surface (4), wherein said working surface (4) develops with continuity from said first end portion (31 ) to said second end portion (32) of said blade(3), wherein said back portion (6) is at least partially placed at said working surface (4), and wherein said back portion (6) develops with continuity from said first end portion (31 ) to said second end portion (32) of said blade (3).

6. Rotor (1 ) according to any one of the previous claims, wherein said tapered development of said back portion (6) defines a back edge (61 ) having development with at least one radial component, wherein a thickness of each blade (3) measured between said working surface (4) and said back edge (61 ) has a first increasing trend up to a maximum (62) moving along a radial direction (300) from said first end portion (31 ) of the blade (3), and a second decreasing trend moving along said radial direction (300) fromsaid maximum (62) to said second end portion (32), and wherein said maximum (62) is located closer to said second end portion (32) of said blade (3) with respect to said first end portion (31 ).

7. Rotor (1 ) according to any one of the previous claims, comprising a plurality of blades (3) distributed along a whole useful axial development (SA) of said central shaft (200), wherein said plurality of blades (3) comprises two or more groups (G) of blades (3), each group (G) of blades (3) comprising a respective plurality of blades (3) arranged mutually in sequence along an axial direction (200), and wherein each group (G) of blades (3) is angularly equispaced from remaining groups (G) of blades (3) of said plurality of blades with respect to an axis of said central shaft (2).

8. Rotor (1 ) according to claim 7, wherein blades of said respective plurality of blades (3) of each group (G) of blades (3) are arranged mutually in sequence along said axial direction (200) for substantially said whole useful axial development (SA) of said central shaft (2), wherein said respective plurality of blades (3) of each group (G) of blades (3) is distributed along said axial direction (200) following a portion of line (L) having development with at least one circumferential component, wherein said portion of line (L) has helical development with respect to said axis of said central shaft (2), wherein said helical development has constant pitch greater than or equal to 2.5 times said useful axial development (SA) of said central shaft (2), and less than or equal to 5.5 times the useful axial development (SA) of the central shaft (2).

9. Hydrokinetic turbine (99) comprising a support frame (90) and the rotor (1 ) according to any one of the previous claims rotatably fixed to said support frame (90), wherein said hydrokinetic turbine (99) further comprises means for generating electric energy connected to said rotor (1 ) for generating electric energy from a rotation of said rotor (1 ) about an axis of said central shaft (2).

10. Hydrokinetic turbine (99) according to claim 9, wherein said turbine (99) is a river turbine with axis horizontal and transverse with respect to said advancing direction (100) of said operating fluid, and wherein said support frame (90) is configured for being able to move said rotor (1 ) with respect to said operating fluid along a direction having at least one vertical component.

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