EP2459871A2 - Aerogenerator with free internal flow rotor - Google Patents

Aerogenerator with free internal flow rotor

Info

Publication number
EP2459871A2
EP2459871A2 EP10754561A EP10754561A EP2459871A2 EP 2459871 A2 EP2459871 A2 EP 2459871A2 EP 10754561 A EP10754561 A EP 10754561A EP 10754561 A EP10754561 A EP 10754561A EP 2459871 A2 EP2459871 A2 EP 2459871A2
Authority
EP
European Patent Office
Prior art keywords
rotor
blades
airfoil
way
rotation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10754561A
Other languages
German (de)
French (fr)
Inventor
Mario Rosario Chiarelli
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Atzeni Davide
Bolognesi Paolo
Massai Andrea
Russo Giovanni
Original Assignee
Atzeni Davide
Bolognesi Paolo
Massai Andrea
Russo Giovanni
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Atzeni Davide, Bolognesi Paolo, Massai Andrea, Russo Giovanni filed Critical Atzeni Davide
Publication of EP2459871A2 publication Critical patent/EP2459871A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/06—Rotors
    • F03D3/061—Rotors characterised by their aerodynamic shape, e.g. aerofoil profiles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/005—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor  the axis being vertical
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/04—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor  having stationary wind-guiding means, e.g. with shrouds or channels
    • F03D3/0436—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor  having stationary wind-guiding means, e.g. with shrouds or channels for shielding one side of the rotor
    • F03D3/0472—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor  having stationary wind-guiding means, e.g. with shrouds or channels for shielding one side of the rotor the shield orientation being adaptable to the wind motor
    • F03D3/049—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor  having stationary wind-guiding means, e.g. with shrouds or channels for shielding one side of the rotor the shield orientation being adaptable to the wind motor with converging inlets, i.e. the shield intercepting an area greater than the effective rotor area
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/06—Rotors
    • F03D3/062—Rotors characterised by their construction elements
    • F03D3/066—Rotors characterised by their construction elements the wind engaging parts being movable relative to the rotor
    • F03D3/067—Cyclic movements
    • F03D3/068—Cyclic movements mechanically controlled by the rotor structure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/06—Controlling wind motors  the wind motors having rotation axis substantially perpendicular to the air flow entering the rotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/20—Rotors
    • F05B2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
    • F05B2240/301—Cross-section characteristics
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2250/00—Geometry
    • F05B2250/20—Geometry three-dimensional
    • F05B2250/23—Geometry three-dimensional prismatic
    • F05B2250/232—Geometry three-dimensional prismatic conical
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/70—Adjusting of angle of incidence or attack of rotating blades
    • F05B2260/72—Adjusting of angle of incidence or attack of rotating blades by turning around an axis parallel to the rotor centre line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/70—Adjusting of angle of incidence or attack of rotating blades
    • F05B2260/79—Bearing, support or actuation arrangements therefor
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/74—Wind turbines with rotation axis perpendicular to the wind direction

Definitions

  • the present invention refers to the technical field relative to the machines suitable for the exploitation of the energy of a fluid mass in movement (for example, air or water) .
  • the invention concerns a high efficiency aero-generator with vertical-axis rotor.
  • aero-generators are widely used to produce electric energy thanks to the transformation of the mechanical energy of the rotor set in movement by the air flow that collides with it.
  • a transfer of energy of the flow that causes the rotation of the blades is obtained which, rotating, produce mechanical energy.
  • the rotation of the blades can then be transmitted to appropriate electrical generators or to mechanical devices.
  • the efficiency of an aero-generator is defined as the relation between the instantaneous mechanical power available on the axis of the rotor and the instantaneous power of the fluid mass that collides with the rotor itself and depends on the configuration of the rotor itself.
  • a first example of aero-generator concerns the horizontal-axis aero-generators, which have a maximum efficiency of about 45%-50%.
  • the supporting elements which are typically constituted by straight or twisted blades, present problems of structural stability that increase when the dimensions of the blades is greater and that influence the performance.
  • the pitch of the blades is in fact reduced to avoid dynamic overstress to the detriment of the productivity of the machine itself.
  • the pressure gradients that are produced on the blade along its extension, and in particular in the area of the free end are the cause of a non negligible noise.
  • a complex airfoil like in the case airfoil used in the turbo-machinery sector, for example, not only has a very variable thickness along the chord and therefore with the upper surface and the lower surface of very different shapes between them, but it is also normally characterized by a very curved skeleton (the middle line between upper surface and lower surface) .
  • the airfoil is univocally defined by different parameters, among which the polynomial equations that define the upper surface and the lower surface, together with the polynomial equation that defines the skeleton of the airfoil.
  • such equations can also be described in a particularly efficient manner by means of SPLINE, BSPLINE o NURBS functions.
  • some basic characterizing elements are the mathematical function that represents the progress, along the chord, of the radius of curvature of the skeleton (middle radius of curvature R) , the mathematical function that defines the skeleton itself and the mathematical function that defines the percentage thickness (t/c) of the airfoil along the chord.
  • a profile can therefore be considered as of low curvature when, for example, of the said parameters the middle radius of curvature R exceeds some threshold values or the maximum value of the percentage thickness t/c remains below some threshold values.
  • airfoils of low curvature can be considered as the profiles wherein, basically, the following are verified: a) the ratio between the coordinate Ymax of the skeleton and the chord C is below 0.2; b) the percentage thickness (t/c) is uniform or, along the chord, always remains below 0.15; c) the function that represents the middle radius of curvature R of the skeleton presents a variation interval with an absolute minimum point above 0.35 and, at the same time, an absolute maximum point above 2.2 (these last values to be intended as referred to a unitary chord) .
  • a wind turbine 10 is described realized through a plurality of plates 12 that, in pairs, comprise among them a rotor system 14.
  • the rotor system comprises a circular roof 16 and a circular base 18 between which a plurality of blades result comprised arranged in a circumferential manner so as to realize a free internal volume within which the air flow can flow freely without encountering obstacles.
  • the rotor system 14 is connected in a rotatable manner between two consecutive plates 12 through a rotatory pivot that connects the roof
  • the rotor system 14 can freely rotate with respect to the two plates within which it results comprised, leaving the said internal volume free from obstacles for the circulating flow.
  • a plurality of stators 30 are then arranged in a fixed position in a circumferential manner with respect to the plate 12 so as to appropriately shield the blades from wind flows that would obstacle the rotation of the rotor
  • the configuration of the pre-chosen blades does not present a specific airfoil but is substantially constituted by a bent flat plate of a subtle and uniform thickness.
  • the curvature is low and the pitch angle improper .
  • the rotor (I' ) comprises an upper bulkhead (3) and a lower bulkhead (2) connected between them through a plurality of blades (1) .
  • the blades have also a predetermined airfoil and are further distanced among them to allow the passage (entry/exit) through the chamber (20) of a circulating flow, for example air.
  • the blades are also arranged according to a predetermined blade pitch angle so that, when in use, when the flow collides with the chamber (20), the flow can go into the chamber (20) from a side undergoing a first deviation and go out from the opposite side further undergoing a second deviation in such a way as to generate lift on a greater number of blades and cause a rotation of the rotor (I' ) .
  • the blades have an airfoil with high curvature and are arranged according to a blade pitch angle comprised between a range that varies from 30° to 60°, preferably between 37° and 52°.
  • the skeleton (80) of the airfoil must be such as to result that can be represented through a polynomial function at least of the sixth degree wherein, further, the ratio between the maximum coordinate Ymax of the skeleton and the Chord (Ymax/Corda) is comprised within a range that varies from 0.2 to 0.5.
  • R of the skeleton along the chord must vary within an interval comprised between a minimum of 0.25 and a maximum of 2.2.
  • the mathematical function (90), or curve, representing the percentage thickness (t/c) of the airfoil must foresee an absolute maximum (only maximum value of the curve) variable within a range between 0.15 and 0.35 and arranged in a zone substantially comprised between the 10% and the 20% of the chord.
  • the present rotor can further comprise a flow recovery device (200) hinged around the axis (7) in such a way as to convey into the chamber (20) the flow going into the device (200) .
  • the conveyance device can comprise an entry section (201) and an exit section (202) , of a smaller area with respect to the entry section, in such a way that the air flow conveyed along the said recovery device increases its speed along the path towards the rotor.
  • the recovery device can comprise two hinge arms (204) to connect the device to the rotor (1') through two shafts (7', 7") and at least a tab (203), preferably two opposed tabs, connected to the said arms in the hinge point and that extend posteriorly to the exit section so as to be able to self-orientate on the basis of the direction of the flow that collides with it.
  • the recovery device can comprise a system of servo-controlled orientation in case the posterior tabs are not present.
  • the exit section (202) can have a shape that substantially traces the external profile of the rotor (I' ) in such a way that the device is placed close to the rotor itself.
  • the recovery device (200) can also comprise two or more internal channels (210', 210'') into which the fluid is directed towards the exit section (202), the said channels being configured in such a way as to direct the fluid in a substantially tangential manner to the airfoil of the blades that face each channel.
  • the exit section can substantially trace half of the external profile of the rotor.
  • adjustment means can be included to change the blade pitch angle of the blades.
  • the said adjustment means can comprise according to a possible solution:
  • a circular crown (410) at least partially dented and concentric to the blades;
  • Two gear wheels (400) preferably diametrically opposed, each one connected in the pivoting point of a blade in such a way by which the rotation of the said wheel (400) rigidly drags in rotation the blade, changing its blade pitch angle.
  • the wheels (400) are meshed with the circular crown (410) in such a way that the rotation of the crown (410), through the setting in rotation of the control wheels (401), causes the rotation of the blades through the wheels (400).
  • all the blades are reciprocally connected through the leading edge by hinged arms (501) in such a way that the rotation of the wheels (400) is rigidly transmitted to all the remaining blades, causing an equivalent change of blade pitch angle.
  • the adjustment means can comprise a pair of irreversible actuators (500) fixed to the ends of two blades diametrically opposed, together with the connection system of all the blades with hinged arms (501) .
  • the bulkheads (2, 3) can be configured in such a way that their surface that faces the internal chamber (20) of the rotor is shaped, instead of flat, so as to progressively restrict the internal volume of the chamber, producing a pressure reduction and an increase of the speed of the flow inside the rotor.
  • FIG. 1 and figure 2 show respectively a view of the whole of an aero-generator provided with a rotor 1' in accordance with the invention
  • FIG. 3 shows a plan section of the rotor 1' so as to highlight the path of the flow going into and going out of the rotor;
  • FIG. 4 shows, for clarity purposes, an axonometric view of the rotor of figure 3;
  • FIG. 12 Figures from 5 to 12 show graphics on the basis of the position along the chord wherein the airfoil of the invention is represented, the relative skeleton, the polynomial equations that represent upper surface and lower surface, together with a progress (always adimensionalized on the basis of the chord) of the radius of curvature of the skeleton and, last, again the skeleton and the percentage thickness (t/c) with the relative polynomial equations;
  • Figure 15 shows a known formula for the calculation of the radius of curvature of a flat line that defines a generic geometrical airfoil
  • FIG. 25 to 27 Figures from 25 to 27 show a flow recovery device in accordance with the present invention.
  • Figure 28 shows a stator
  • Figure 29 shows an airfoil, as described, having mobile surfaces
  • Figures 30 and 31 show systems to render the blade pitch angle variable.
  • the blades 1 of the rotor 1' being part of the aero-generator are described.
  • the blades result interposed between an upper bulkhead 3 and a lower bulkhead 2 and directly connected to them by one of their ends in such a way as to realize an internal chamber 20, for example cylindrical, (see also figure 3 or figure 4) .
  • a vertical supporting base 12 realized by a tower 12 of a tubular or pylon structure, supports the rotor group 1' through a rotatable shaft V assembled idle on the tower through a support provided with bearings 8. In such a manner, the rotor 1' is free to rotate with respect to the tower around the said axis 7.
  • the supporting base 12 also supports, in a rotatable manner, a dented wheel 6.
  • the dented wheel 6 is arranged in axis with the rotor 1' through a connection to the rotatable shaft 7' in such a way that the rotation of the rotor 1' is transmitted to the wheel through the shaft.
  • a spacer 5 is arranged between wheel and rotor.
  • the wheel 6 engages with gear wheels belonging to a power generator group 9 arranged on a support 10 rigidly fixed to the tower 12. In such a manner, the rotation of the rotor 1' is transmitted to the generator 9 through the wheel 6, causing the production of current.
  • a control and electrical efficiency board 13 and a base 14 complete the structure.
  • FIG. 2 A second possible embodiment is described in figure 2 and is identical to the preceding one except for some aspects that will be described below.
  • some mass-balance weights 50 are comprised and arranged in correspondence of the upper and lower bulkhead so as to better balance the rotation of the rotor 1' .
  • the tower includes an internal axial housing so as to hold a power generator group 109 arranged in axis with the rotor 1'.
  • a joint 16 is included that connects the axis of the rotor 1' to the axis of the power generator group 109.
  • a braking support 15 is included for a brake 17 and a Planetary gearbox 18.
  • the preferred configuration of the invention comprises an internal volume 20 free from any structural element.
  • the rotation shaft 7' is connected directly to the lower bulkhead in such a way as to avoid that it extends inside the chamber 20.
  • Such a solution is naturally advantageous since the circulating air flow in the chamber does not encounter obstacles that might reduce the energy.
  • the generation of the torque is obtained thanks to the action of the lift forces that develop on the blades.
  • Such lift forces are correlated to the deviation of the fluid current, and therefore to the variation of the quantity of motion of the flow that is verified both outside and inside the rotor itself.
  • the fluid current impacts against the front blades of the rotor 1' (that is the blades that are at that moment opposite the flow) and undergoes a first deviation during the entry into the internal free volume. Inside the volume 20 the flow proceeds freely until it impacts against the back blades, thus undergoing a second deviation in exit.
  • the deviation of the overall fluid current is therefore correlated to the lift forces that are generated on the supporting blades of the rotor and therefore on the basis of the form of the airfoil and of the blade pitch angle.
  • figure 5 shows a base airfoil with high curvature used in accordance with the invention.
  • the said airfoil has been found to be surprisingly a high efficiency airfoil for the case in question.
  • the graphic shows an interpolation of the upper surface points 60 whose coordinates have been adimensionalized with respect to the length of the chord C and an interpolation of the upper surface points 70 always with coordinates adimensionalized with respect to the chord.
  • the sequence of circular points 80 provides the geometrical description of the skeleton calculated as the average of the coordinates Y of the upper surface and the lower surface.
  • the equations that represent, through a polynomial of the sixth degree, the said curves of the upper surface 60 and the lower surface 70, are shown.
  • Figure 6 shows the curve, with relative equation of polynomial of the sixth degree, relative to the said skeleton 80 together with the graphic 100 that represents the evolution of the radius of curvature R of the said skeleton, from now onwards called, for simplicity purposes, middle radius of curvature R (100) .
  • the figure in question highlights how the curve representing the middle radius of curvature 100 (always adimensionalized with respect to the chord of the airfoil) is comprised within a range of values, being the minimum equal to 0.3 in the front zone of the airfoil (about 15% of the chord) and the maximum equal to 1.2 in the back zone of the airfoil (about 80% of the chord) .
  • the same graphic also shows the evolution of the percentage thickness 90 (t/c) along the chord, which presents a maximum of 0.2, while the ratio between the Ymax of the skeleton and the chord is of about 0.3.
  • the graphics that follow show percentage variations (-25%, +50% e +75%) in order to obtain, starting from the optimal airfoil, other airfoils with high curvature with high aerodynamic features.
  • figures 7 and 8 show a range of variation of the airfoil with high curvature with a reduction of the quote Y of the points of the upper surface and of the lower surface of 25%.
  • Figure 7 therefore shows an Ymax, adimensionalized with respect to the chord, of about 0.2.
  • Figure 8 shows an evolution of the middle radius of curvature R of the curve of the skeleton interpolated whose minimum has a value of about 0.3 (front part of the airfoil at about the 10% of the chord) and a maximum of about 1.4 (back zone of the airfoil at about 80% of the chord) .
  • the same figure shows a ratio (t/c) with absolute maximum of about 0.15.
  • figures 9 and 10 show an increase of the 50% in the coordinates Y relative to the points representing upper surface and lower surface with an Ymax, adimensionalized with respect to the chord, of about 0.45.
  • the middle radius of curvature of the skeleton has a minimum of about 0.3 in the central zone of the airfoil and a maximum of about 1.65 in the front zone.
  • the ratio (t/c) presents an absolute maximum of about 0.3.
  • figures 11 and 12 show a variation of the airfoil with an increase of the 75% in the coordinates Y relative to the points representing upper surface and lower surface.
  • the adimensionalized Ymax is of 0.5
  • the middle radius of curvature presents a minimum of 0.25 in the central zone of the airfoil and a maximum of 2,20 in the front zone.
  • the ratio (t/c) presents an absolute maximum of about 0.35.
  • the middle radius of curvature R has been calculated according to the formula written for easy reading in figure 15.
  • the formula well known in the background art, indicates that the reciprocal of the radius of curvature (1/R) is equal to the ratio between a numerator and a denominator.
  • the numerator includes the second derivative of the function v(x), which mathematically describes the line of which to calculate the radius of curvature (in this case v(x) is the equation of the skeleton) preceded by the minus sign (to obtain positive values of R)
  • the denominator includes the sum of the coefficient one with the squared first derivative of the said function and all the denominator raised to three halves.
  • a skeleton (80) that can be represented through a polynomial function at least of the sixth degree wherein, further, the ratio between the maximum coordinate Ymax of the skeleton and the Chord (Ymax/Corda) is comprised within a range variable from 0.2 to 0.5;
  • t/c a percentage thickness (t/c) of the airfoil whose representing function comprises an absolute maximum variable within a range between 0.15 and 0.35 and arranged in a zone substantially comprised between the 10% and the 20% of the chord.
  • the middle radius of curvature R presents two maximum points, not necessarily absolute, respectively at about the 30% of the chord and at about the 80% of the chord.
  • Figure 13 and figure 14 show, always in accordance with the invention, a range of blade pitch angles for the assembly of the said airfoils with high curvature and that further optimize the efficiency of the rotor.
  • Figures 16 and 17 show a solution of aero-generator, as previously described, with the blades of the rotor arranged in such a way as to form a cylindrical internal chamber 20.
  • Figures 21 and 22 show a solution with a spherical rotor 1'
  • the subsequent figures 23 and 24 show a solution with semispheric or semielliptical rotor 1' .
  • a flow recovery device 200 arranged on the rotor 1' in such a way as to optimize the conveyance of the air flow inside the chamber 20, reducing the lateral leaks due to, for example, the rotation itself of the rotor.
  • Figure 25 schematizes the recovery device that comprises an entry section 201 of the air and an exit section 202 for the air. Always figure 25 shows the two back tabs 203 that allow a self-adjustment of the device 200 on the basis of the direction of the wind.
  • the shaft 7' finishes on the lower bulkhead on the opposite side to that of incidence of the blades, while a further shaft 1' ' (both of rotational axis 7) results emerging from the upper bulkhead always on the opposite side to that of incidence of the blades.
  • the conveyor can thus be hinged to the said shafts through two arms 204 in such a way as to result rotatable as well with respect to the axis 7.
  • Figure 26 shows a top view that clearly highlights how the recovery device reduces its transversal area from the entry section 201 towards the exit section 202 so as to capture a greater quantity of flow and convey it into the chamber 20. Moreover, figure 26 highlights how the exit section 202 substantially follows the external profile of the rotor 1' in such a way as to be able to be arranged close to the blades.
  • the entry section is able to convey a great quantity of air flow which, above all, by means of the tapering of section, increases its speed.
  • the recovery device can further comprise inside channels 210 that substantially direct the flow according to such an angle by which the flow surrounds the blades positioned in front of the rotor so that these result mainly supporting.
  • Figure 27 in fact shows how the channel 210' conveys the flow according to such an entry direction (see arrow in figure) such that the flow surrounds in a substantially tangential manner the airfoil of the blades that face the said channel. Otherwise, the said blades would be braking since the flow would impact orthogonally to the airfoil itself.
  • Always figure 27 shows the entry of the flow that is conveyed along the blades into the channel 210' ' .
  • the conveyance device 200 can be in all the configurations arranged at a distance of 0.05 up to 1.5 times the radius of the rotor 1' from the external profile of the rotor.
  • Figure 28 shows, as an alternative to the conveyor, a simple stator, self-adjustable as well on the basis of the direction of the wind.
  • the stator comprises a directional wing 300, arranged superiorly, and a front shielding part 301 and a back conveyance part 302 in such a way as to shield the blades that would be braking on the basis of the direction of the wind.
  • the stator is assembled in a rotatable manner on the rotor 1' around the axis 7.
  • Figure 29 shows, as per all the configurations of airfoil described, the profile can include mobile parts in order to further vary the form.
  • the airfoil of the blades can be fixed or modifiable in the front and/or back part in the same way as what has been realized for aircraft wings.
  • the curvature can be varied through an adjustment system, inserted in the two end bulkheads that activates the eventual front (slat) and back (flap) mobile surfaces.
  • figure 30 and figure 31 show systems for the variation of the blade pitch angle.
  • figure 30 shows a rotation obtainable through the use of gear wheels 400 and of a partially dented crown 410
  • figure 31 shows the use of two actuators 500.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Wind Motors (AREA)
  • Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
  • Lubricants (AREA)

Abstract

The present invention concerns an innovative rotor (1') for an aero-generator comprising an upper bulkhead (3), a lower bulkhead (2) and a rotational axis (7) around which the rotor is rotatable. A plurality of blades (1) are connected by one of their end to the upper bulkhead (3) and by the opposed end to the lower bulkhead (2) in such a way as to form an internal chamber (20), rotatable around the said rotational axis (7). The blades, of a predetermined airfoil, further result distanced among them to allow the passage through the chamber (20) of a flow, preferably an air flow, and are arranged according to a certain blade pitch angle in such a way that, in use, when the flow collides with the chamber (20), it can go into the chamber (20) from a side undergoing a first deviation and go out from the opposite side further undergoing a second deviation, generating lift on the blades that it collides with and therefore causing a rotation of the rotor (1'). In accordance with the invention, the blades have an airfoil with high curvature and are further arranged according to an angle of incidence comprised within a variable range between 30° and 60°, preferably between 37° and 52°, in such a way as to increase the lift forces.

Description

TITLE
AEROGENERATOR WITH FREE INTERNAL FLOW ROTOR
Technical Field
The present invention refers to the technical field relative to the machines suitable for the exploitation of the energy of a fluid mass in movement (for example, air or water) .
In particular, the invention concerns a high efficiency aero-generator with vertical-axis rotor.
Background Art
As it is known, aero-generators are widely used to produce electric energy thanks to the transformation of the mechanical energy of the rotor set in movement by the air flow that collides with it. In that sense, by making the fluid impact against the supporting surfaces of the machine (blades) a transfer of energy of the flow that causes the rotation of the blades is obtained which, rotating, produce mechanical energy. The rotation of the blades can then be transmitted to appropriate electrical generators or to mechanical devices.
The efficiency of an aero-generator is defined as the relation between the instantaneous mechanical power available on the axis of the rotor and the instantaneous power of the fluid mass that collides with the rotor itself and depends on the configuration of the rotor itself.
A first example of aero-generator concerns the horizontal-axis aero-generators, which have a maximum efficiency of about 45%-50%. Although the efficiency of these machines is quite high, the supporting elements, which are typically constituted by straight or twisted blades, present problems of structural stability that increase when the dimensions of the blades is greater and that influence the performance. At high speeds of the wind the pitch of the blades is in fact reduced to avoid dynamic overstress to the detriment of the productivity of the machine itself. Last, the pressure gradients that are produced on the blade along its extension, and in particular in the area of the free end, are the cause of a non negligible noise.
Such technical inconveniences are in part reduced in the case of vertical-axis aero-generators, of which there exist different examples in literature (ex. Savonius Rotor, Darrieus Rotor, H-Rotor) , even if they generally present an efficiency not superior to the 35%.
Nevertheless, in general, among these types of aero- generators, some of them (Savonius and H-Rotor) comprise blades with extremely simple airfoils, to the point that they can be assimilated to a simple bent flat plate, while others (Darrieus) comprise blades realized with airfoils that are usually of the NACA or NREL type and anyway of a not particularly complex design.
A complex airfoil, like in the case airfoil used in the turbo-machinery sector, for example, not only has a very variable thickness along the chord and therefore with the upper surface and the lower surface of very different shapes between them, but it is also normally characterized by a very curved skeleton (the middle line between upper surface and lower surface) . In particular, the airfoil is univocally defined by different parameters, among which the polynomial equations that define the upper surface and the lower surface, together with the polynomial equation that defines the skeleton of the airfoil. In the background art, such equations can also be described in a particularly efficient manner by means of SPLINE, BSPLINE o NURBS functions. Alternatively, some basic characterizing elements are the mathematical function that represents the progress, along the chord, of the radius of curvature of the skeleton (middle radius of curvature R) , the mathematical function that defines the skeleton itself and the mathematical function that defines the percentage thickness (t/c) of the airfoil along the chord.
On the basis of the preceding considerations, a profile can therefore be considered as of low curvature when, for example, of the said parameters the middle radius of curvature R exceeds some threshold values or the maximum value of the percentage thickness t/c remains below some threshold values.
In particular, airfoils of low curvature can be considered as the profiles wherein, basically, the following are verified: a) the ratio between the coordinate Ymax of the skeleton and the chord C is below 0.2; b) the percentage thickness (t/c) is uniform or, along the chord, always remains below 0.15; c) the function that represents the middle radius of curvature R of the skeleton presents a variation interval with an absolute minimum point above 0.35 and, at the same time, an absolute maximum point above 2.2 (these last values to be intended as referred to a unitary chord) .
Current vertical-axis aero-generators present, generally, either very simple airfoils, that can be assimilated to straight flat plates or otherwise bent (in that case both the leading edge and the trailing edge of the airfoil are identical and the thickness is nearly constant along al the chord of the airfoil) , or airfoils that present the characteristic of being of low curvature on the basis of the preceding definition. Moreover, the blade pitch angles are not optimal, causing an effect wherein the fluid does not surround tangentially the airfoil of the blades but, on the contrary, collides with it transversally, thus reducing the lift effects and increasing those of drag.
One of such cases is, for example, shown in
US2003/0209911, wherein a wind turbine 10 is described realized through a plurality of plates 12 that, in pairs, comprise among them a rotor system 14. The rotor system comprises a circular roof 16 and a circular base 18 between which a plurality of blades result comprised arranged in a circumferential manner so as to realize a free internal volume within which the air flow can flow freely without encountering obstacles. The rotor system 14 is connected in a rotatable manner between two consecutive plates 12 through a rotatory pivot that connects the roof
16 and a plate 12 and the base 18 to the underlying plate.
In such a manner, the rotor system 14 can freely rotate with respect to the two plates within which it results comprised, leaving the said internal volume free from obstacles for the circulating flow.
A plurality of stators 30 are then arranged in a fixed position in a circumferential manner with respect to the plate 12 so as to appropriately shield the blades from wind flows that would obstacle the rotation of the rotor
14.
As it is well highlighted in the designs, the configuration of the pre-chosen blades does not present a specific airfoil but is substantially constituted by a bent flat plate of a subtle and uniform thickness.
Moreover, the curvature is low and the pitch angle improper .
Disclosure of invention
It is therefore the aim of the present invention to provide a new type of aero-generator wherein the rotor is configured in such a way as to solve at least in part the above-mentioned inconveniences.
In particular, it is the aim of the present invention to provide a new type of rotor wherein the airfoil of the blades and their pitch angle is such as to significantly increase the efficiency to values well above the 35% currently obtainable.
These and other aims are obtained with the present rotor (I' ) for aero-generator as per claim 1.
The rotor (I' ) comprises an upper bulkhead (3) and a lower bulkhead (2) connected between them through a plurality of blades (1) . The blades, together with the bulkheads, form an internal chamber (20) , rotatable around a rotational axis (7) . The blades have also a predetermined airfoil and are further distanced among them to allow the passage (entry/exit) through the chamber (20) of a circulating flow, for example air. The blades are also arranged according to a predetermined blade pitch angle so that, when in use, when the flow collides with the chamber (20), the flow can go into the chamber (20) from a side undergoing a first deviation and go out from the opposite side further undergoing a second deviation in such a way as to generate lift on a greater number of blades and cause a rotation of the rotor (I' ) .
In accordance with the invention, the blades have an airfoil with high curvature and are arranged according to a blade pitch angle comprised between a range that varies from 30° to 60°, preferably between 37° and 52°.
In such a manner, it has been experimentally verified that the lift action of the blades, and therefore the overall efficiency, are extremely improved, exceeding by far the standard efficiency value of 35%.
In particular, advantageously, it has been discovered that an airfoil with high curvature with the following range of geometrical characteristics increases the efficiency significantly.
The skeleton (80) of the airfoil must be such as to result that can be represented through a polynomial function at least of the sixth degree wherein, further, the ratio between the maximum coordinate Ymax of the skeleton and the Chord (Ymax/Corda) is comprised within a range that varies from 0.2 to 0.5.
The mathematical function (100) , or curve, which represents the progress of the middle radius of curvature
R of the skeleton along the chord, must vary within an interval comprised between a minimum of 0.25 and a maximum of 2.2.
The mathematical function (90), or curve, representing the percentage thickness (t/c) of the airfoil must foresee an absolute maximum (only maximum value of the curve) variable within a range between 0.15 and 0.35 and arranged in a zone substantially comprised between the 10% and the 20% of the chord.
Advantageously, the present rotor can further comprise a flow recovery device (200) hinged around the axis (7) in such a way as to convey into the chamber (20) the flow going into the device (200) .
In particular, the conveyance device can comprise an entry section (201) and an exit section (202) , of a smaller area with respect to the entry section, in such a way that the air flow conveyed along the said recovery device increases its speed along the path towards the rotor.
Advantageously, the recovery device can comprise two hinge arms (204) to connect the device to the rotor (1') through two shafts (7', 7") and at least a tab (203), preferably two opposed tabs, connected to the said arms in the hinge point and that extend posteriorly to the exit section so as to be able to self-orientate on the basis of the direction of the flow that collides with it.
Alternatively, the recovery device can comprise a system of servo-controlled orientation in case the posterior tabs are not present.
Advantageously, the exit section (202) can have a shape that substantially traces the external profile of the rotor (I' ) in such a way that the device is placed close to the rotor itself.
Advantageously, in all the described configurations, the recovery device (200) can also comprise two or more internal channels (210', 210'') into which the fluid is directed towards the exit section (202), the said channels being configured in such a way as to direct the fluid in a substantially tangential manner to the airfoil of the blades that face each channel.
In that case, advantageously, the exit section can substantially trace half of the external profile of the rotor.
Advantageously, adjustment means can be included to change the blade pitch angle of the blades.
Advantageously, the said adjustment means can comprise according to a possible solution:
- A circular crown (410) at least partially dented and concentric to the blades;
- At least one, preferably two rotatable control gear wheels (401) coupled internally to the crown in such a way that the rotation of the said control wheels (401) causes the rotation of the circular crown (410) and;
- Two gear wheels (400) , preferably diametrically opposed, each one connected in the pivoting point of a blade in such a way by which the rotation of the said wheel (400) rigidly drags in rotation the blade, changing its blade pitch angle.
Moreover, the wheels (400) are meshed with the circular crown (410) in such a way that the rotation of the crown (410), through the setting in rotation of the control wheels (401), causes the rotation of the blades through the wheels (400). Last, further, all the blades are reciprocally connected through the leading edge by hinged arms (501) in such a way that the rotation of the wheels (400) is rigidly transmitted to all the remaining blades, causing an equivalent change of blade pitch angle.
As an alternative, advantageously, the adjustment means can comprise a pair of irreversible actuators (500) fixed to the ends of two blades diametrically opposed, together with the connection system of all the blades with hinged arms (501) .
Advantageously, in all the described configurations, the bulkheads (2, 3) can be configured in such a way that their surface that faces the internal chamber (20) of the rotor is shaped, instead of flat, so as to progressively restrict the internal volume of the chamber, producing a pressure reduction and an increase of the speed of the flow inside the rotor.
Brief description of drawings
Further features and advantages of the present aero- generator, according to the invention, will result clearer with the following description of some embodiments, made to illustrate but not to limit, with reference to the annexed drawings, wherein:
- Figure 1 and figure 2 show respectively a view of the whole of an aero-generator provided with a rotor 1' in accordance with the invention;
- Figure 3 shows a plan section of the rotor 1' so as to highlight the path of the flow going into and going out of the rotor;
- Figure 4 shows, for clarity purposes, an axonometric view of the rotor of figure 3;
- Figures from 5 to 12 show graphics on the basis of the position along the chord wherein the airfoil of the invention is represented, the relative skeleton, the polynomial equations that represent upper surface and lower surface, together with a progress (always adimensionalized on the basis of the chord) of the radius of curvature of the skeleton and, last, again the skeleton and the percentage thickness (t/c) with the relative polynomial equations;
— Figures 13 and 14 show optimal blade pitch angles;
— Figure 15 shows a known formula for the calculation of the radius of curvature of a flat line that defines a generic geometrical airfoil;
— Figures from 16 to 24 show other embodiments of rotor 1' in accordance with the invention;
— Figures from 25 to 27 show a flow recovery device in accordance with the present invention.
— Figure 28 shows a stator;
— Figure 29 shows an airfoil, as described, having mobile surfaces;
— Figures 30 and 31 show systems to render the blade pitch angle variable.
Description of one preferred embodiment
With reference to figure 1 and figure 2, an aero- generator is described in accordance with the invention.
Structurally, with reference to figure 1, the blades 1 of the rotor 1' being part of the aero-generator are described. The blades result interposed between an upper bulkhead 3 and a lower bulkhead 2 and directly connected to them by one of their ends in such a way as to realize an internal chamber 20, for example cylindrical, (see also figure 3 or figure 4) .
Always figure 1 highlights a careening closure cover 4 arranged on the upper bulkhead 3.
A vertical supporting base 12, realized by a tower 12 of a tubular or pylon structure, supports the rotor group 1' through a rotatable shaft V assembled idle on the tower through a support provided with bearings 8. In such a manner, the rotor 1' is free to rotate with respect to the tower around the said axis 7.
The supporting base 12 also supports, in a rotatable manner, a dented wheel 6. In particular, the dented wheel 6 is arranged in axis with the rotor 1' through a connection to the rotatable shaft 7' in such a way that the rotation of the rotor 1' is transmitted to the wheel through the shaft. A spacer 5 is arranged between wheel and rotor.
As always shown in figure 1, the wheel 6 engages with gear wheels belonging to a power generator group 9 arranged on a support 10 rigidly fixed to the tower 12. In such a manner, the rotation of the rotor 1' is transmitted to the generator 9 through the wheel 6, causing the production of current.
A control and electrical efficiency board 13 and a base 14 complete the structure.
A second possible embodiment is described in figure 2 and is identical to the preceding one except for some aspects that will be described below. In particular, in accordance with such a solution, some mass-balance weights 50 are comprised and arranged in correspondence of the upper and lower bulkhead so as to better balance the rotation of the rotor 1' .
The tower includes an internal axial housing so as to hold a power generator group 109 arranged in axis with the rotor 1'. To that aim, a joint 16 is included that connects the axis of the rotor 1' to the axis of the power generator group 109. In particular, interposed between joint 16 and generator group 109 a braking support 15 is included for a brake 17 and a Planetary gearbox 18.
As clearly shown in figure 4, for example, and also in figure 3, the preferred configuration of the invention comprises an internal volume 20 free from any structural element. In particular, the rotation shaft 7' is connected directly to the lower bulkhead in such a way as to avoid that it extends inside the chamber 20. Such a solution is naturally advantageous since the circulating air flow in the chamber does not encounter obstacles that might reduce the energy.
In use, the generation of the torque is obtained thanks to the action of the lift forces that develop on the blades. Such lift forces are correlated to the deviation of the fluid current, and therefore to the variation of the quantity of motion of the flow that is verified both outside and inside the rotor itself.
In particular, as shown in figure 3, the fluid current impacts against the front blades of the rotor 1' (that is the blades that are at that moment opposite the flow) and undergoes a first deviation during the entry into the internal free volume. Inside the volume 20 the flow proceeds freely until it impacts against the back blades, thus undergoing a second deviation in exit. The deviation of the overall fluid current is therefore correlated to the lift forces that are generated on the supporting blades of the rotor and therefore on the basis of the form of the airfoil and of the blade pitch angle.
In accordance with a first aspect of the invention, figure 5 shows a base airfoil with high curvature used in accordance with the invention. The said airfoil has been found to be surprisingly a high efficiency airfoil for the case in question. The graphic shows an interpolation of the upper surface points 60 whose coordinates have been adimensionalized with respect to the length of the chord C and an interpolation of the upper surface points 70 always with coordinates adimensionalized with respect to the chord. The sequence of circular points 80 provides the geometrical description of the skeleton calculated as the average of the coordinates Y of the upper surface and the lower surface. In the graphic of figure 5 the equations that represent, through a polynomial of the sixth degree, the said curves of the upper surface 60 and the lower surface 70, are shown.
Figure 6 shows the curve, with relative equation of polynomial of the sixth degree, relative to the said skeleton 80 together with the graphic 100 that represents the evolution of the radius of curvature R of the said skeleton, from now onwards called, for simplicity purposes, middle radius of curvature R (100) . The figure in question highlights how the curve representing the middle radius of curvature 100 (always adimensionalized with respect to the chord of the airfoil) is comprised within a range of values, being the minimum equal to 0.3 in the front zone of the airfoil (about 15% of the chord) and the maximum equal to 1.2 in the back zone of the airfoil (about 80% of the chord) .
The same graphic also shows the evolution of the percentage thickness 90 (t/c) along the chord, which presents a maximum of 0.2, while the ratio between the Ymax of the skeleton and the chord is of about 0.3.
The graphics of figure 5 and of figure 6 and the relative equations (appropriately numbered with reference to the curve they represent in the graphics) therefore define completely the optimal airfoil of the invention.
The graphics that follow show percentage variations (-25%, +50% e +75%) in order to obtain, starting from the optimal airfoil, other airfoils with high curvature with high aerodynamic features.
In particular, figures 7 and 8 show a range of variation of the airfoil with high curvature with a reduction of the quote Y of the points of the upper surface and of the lower surface of 25%. Figure 7 therefore shows an Ymax, adimensionalized with respect to the chord, of about 0.2. Figure 8 shows an evolution of the middle radius of curvature R of the curve of the skeleton interpolated whose minimum has a value of about 0.3 (front part of the airfoil at about the 10% of the chord) and a maximum of about 1.4 (back zone of the airfoil at about 80% of the chord) . The same figure shows a ratio (t/c) with absolute maximum of about 0.15.
Likewise, figures 9 and 10 show an increase of the 50% in the coordinates Y relative to the points representing upper surface and lower surface with an Ymax, adimensionalized with respect to the chord, of about 0.45.
In particular, the middle radius of curvature of the skeleton has a minimum of about 0.3 in the central zone of the airfoil and a maximum of about 1.65 in the front zone.
The ratio (t/c) presents an absolute maximum of about 0.3.
Last, figures 11 and 12 show a variation of the airfoil with an increase of the 75% in the coordinates Y relative to the points representing upper surface and lower surface. In particular, (figure 11) the adimensionalized Ymax is of 0.5, while the middle radius of curvature (figure 12) presents a minimum of 0.25 in the central zone of the airfoil and a maximum of 2,20 in the front zone. Last, the ratio (t/c) presents an absolute maximum of about 0.35.
In all the cases described, the middle radius of curvature R has been calculated according to the formula written for easy reading in figure 15. The formula, well known in the background art, indicates that the reciprocal of the radius of curvature (1/R) is equal to the ratio between a numerator and a denominator. The numerator includes the second derivative of the function v(x), which mathematically describes the line of which to calculate the radius of curvature (in this case v(x) is the equation of the skeleton) preceded by the minus sign (to obtain positive values of R) , while the denominator includes the sum of the coefficient one with the squared first derivative of the said function and all the denominator raised to three halves.
In accordance with the present invention, high efficiency has been discovered to be obtained with very curved airfoils whose geometrical characteristics are comprised within the following ranges:
a skeleton (80) that can be represented through a polynomial function at least of the sixth degree wherein, further, the ratio between the maximum coordinate Ymax of the skeleton and the Chord (Ymax/Corda) is comprised within a range variable from 0.2 to 0.5;
a middle radius of curvature R of the skeleton whose curve that represents it varies along the chord within an interval comprised between an absolute minimum of 0.25 and an absolute maximum of 2.2;
a percentage thickness (t/c) of the airfoil whose representing function comprises an absolute maximum variable within a range between 0.15 and 0.35 and arranged in a zone substantially comprised between the 10% and the 20% of the chord.
Moreover, the middle radius of curvature R presents two maximum points, not necessarily absolute, respectively at about the 30% of the chord and at about the 80% of the chord.
Figure 13 and figure 14 show, always in accordance with the invention, a range of blade pitch angles for the assembly of the said airfoils with high curvature and that further optimize the efficiency of the rotor.
For blade pitch angles it is understood the angle comprised between the straight line 31 passing through the centre of the cylinder 20 and the hinge point 30 of the airfoil with respect to the two said lower and upper bulkheads and the straight line 32 that joins the leading edge and the trailing edge of the airfoil.
As indicated in figure 13 and 14, experimental data have shown an optimization of the efficiency for blade pitch angles comprised between 30° and 60° and preferably between 37° and 52° .
Figures 16 and 17 show a solution of aero-generator, as previously described, with the blades of the rotor arranged in such a way as to form a cylindrical internal chamber 20.
The subsequent figures 18, 19 and 20 show a solution of aero-generator with tronco-conical rotor.
Figures 21 and 22 show a solution with a spherical rotor 1' , while the subsequent figures 23 and 24 show a solution with semispheric or semielliptical rotor 1' .
Always in accordance with the invention, it can also be included, for all the described configurations, a flow recovery device 200 arranged on the rotor 1' in such a way as to optimize the conveyance of the air flow inside the chamber 20, reducing the lateral leaks due to, for example, the rotation itself of the rotor. Figure 25 schematizes the recovery device that comprises an entry section 201 of the air and an exit section 202 for the air. Always figure 25 shows the two back tabs 203 that allow a self-adjustment of the device 200 on the basis of the direction of the wind. To that aim, it is foreseen, as described, that the shaft 7' finishes on the lower bulkhead on the opposite side to that of incidence of the blades, while a further shaft 1' ' (both of rotational axis 7) results emerging from the upper bulkhead always on the opposite side to that of incidence of the blades. The conveyor can thus be hinged to the said shafts through two arms 204 in such a way as to result rotatable as well with respect to the axis 7.
Figure 26 shows a top view that clearly highlights how the recovery device reduces its transversal area from the entry section 201 towards the exit section 202 so as to capture a greater quantity of flow and convey it into the chamber 20. Moreover, figure 26 highlights how the exit section 202 substantially follows the external profile of the rotor 1' in such a way as to be able to be arranged close to the blades.
In accordance with such a solution, the entry section is able to convey a great quantity of air flow which, above all, by means of the tapering of section, increases its speed.
The recovery device, as shown in figure 27, for example, can further comprise inside channels 210 that substantially direct the flow according to such an angle by which the flow surrounds the blades positioned in front of the rotor so that these result mainly supporting. Figure 27 in fact shows how the channel 210' conveys the flow according to such an entry direction (see arrow in figure) such that the flow surrounds in a substantially tangential manner the airfoil of the blades that face the said channel. Otherwise, the said blades would be braking since the flow would impact orthogonally to the airfoil itself. Always figure 27 shows the entry of the flow that is conveyed along the blades into the channel 210' ' .
The use of the channels therefore allows to realize a conveyor that substantially traces half of the external profile of the rotor unlike, for example, what is represented in figure 26.
The conveyance device 200 can be in all the configurations arranged at a distance of 0.05 up to 1.5 times the radius of the rotor 1' from the external profile of the rotor.
Figure 28 shows, as an alternative to the conveyor, a simple stator, self-adjustable as well on the basis of the direction of the wind. The stator comprises a directional wing 300, arranged superiorly, and a front shielding part 301 and a back conveyance part 302 in such a way as to shield the blades that would be braking on the basis of the direction of the wind. The stator is assembled in a rotatable manner on the rotor 1' around the axis 7.
Figure 29 shows, as per all the configurations of airfoil described, the profile can include mobile parts in order to further vary the form. In particular, the airfoil of the blades can be fixed or modifiable in the front and/or back part in the same way as what has been realized for aircraft wings. The curvature can be varied through an adjustment system, inserted in the two end bulkheads that activates the eventual front (slat) and back (flap) mobile surfaces.
Last, figure 30 and figure 31 show systems for the variation of the blade pitch angle. In particular, figure 30 shows a rotation obtainable through the use of gear wheels 400 and of a partially dented crown 410, while figure 31 shows the use of two actuators 500.
In both figures the direct control of the incidence is executed in correspondence of only two blades, while all the blades result connected reciprocally, in correspondence of the leading edge, with arms 501 hinged to the two ends .
In the particular case of figure 30, besides, the rotation of the partially dented crown 410 is obtained through the setting in rotation of conducting wheels 401 controlled by an appropriate external engine, not represented in the figure for simplicity purposes.

Claims

1. A rotor (I' ) for an aero-generator comprising:
- An upper bulkhead (3) ;
- A lower bulkhead (2);
- A rotational axis (7) and;
- A plurality of blades (1) connected by one of their ends to the upper bulkhead (3) and by the opposite end to the lower bulkhead (2) in such a way as to form an internal chamber (20), rotatable around the rotational axis (7), the said blades being among them distanced to allow the passage through the chamber (20) of a flow, preferably an air flow, and being further arranged according to a predetermined blade pitch angle and having a predetermined airfoil so that, in use, when the flow collides with the chamber (20) , it can go into the chamber (20) from a side having a first deviation and go out from the opposite side further having a second deviation in such a way as to generate lift on the blades and cause a rotation of the rotor (I' ) and
characterized in that the blades have an airfoil (60, 70) with high curvature and that, further, are arranged according to a blade pitch angle comprised within a variable range between 30° and 60°, preferably between 37° and 52°, so as to increase the lift.
2. A rotor (I' ) , according to claim 1, wherein the airfoil of the said blades with high curvature is defined by:
- A skeleton (80) that can be represented through a polynomial function at least of the sixth degree wherein, further, the ratio between the maximum coordinate Ymax of the skeleton and the Chord (Ymax/Corda) is comprised within a range variable between 0.2 and 0.5;
- A middle radius of curvature R (100) of the skeleton having the mathematical function that represents it along the chord variable within an interval of values comprised between a minimum of 0.25 and a maximum of 2.2;
- A percentage thickness (t/c) (90) of the airfoil by which the mathematical function that represents it comprises an absolute maximum variable between 0.15 and 0.35 and placed in a zone substantially comprised between the 10% and the 20% of the chord.
3. A rotor (1'), according to claim 2, wherein the progress of the curve representing the middle radius of curvature R is function of the first derivative of the curve representing the skeleton (80) of the airfoil (60, 70) and of the second derivative of the curve representing the skeleton of the airfoil.
4. A rotor (I' ) , according to one or more of the preceding claims from 1 to 3, wherein the said airfoil with high curvature presents a curve representing the middle radius of curvature R having two maximum points, not necessarily absolute, respectively at about the 30% of the chord and at about 80% of the chord.
5. A rotor (I' ) , according to one or more of the preceding claims, wherein upper surface (60) and lower surface (70) of the airfoil are substantially represented by polynomials at least of the sixth degree whose equations coincide with the ones shown in the graphic of figure 5.
6. A rotor (1'), according to claim 1, wherein the said rotational axis (7) is a vertical axis.
7. A rotor (I' ) , according to one or more of the preceding claims, wherein is further provided a vertical rotation shaft (7') of axis (7) for connecting in a rotatable manner the rotor to a supporting base (12), the shaft being connected to the lower bulkhead (2) on the opposite side to that of connection of the blades in such a way as to not extend into the chamber (20) .
8. A rotor (1'), according to one or more of the preceding claims, wherein a flow recovery device (200) is further comprised, hinged around the axis (7) of the rotor (I' ) in such a manner as to convey into the chamber (20) the flow going into the device (200) , the said recovery device comprising an entry section (201) and an exit section (202) of an area inferior with respect to the entry section, in such a way that the air flow conveyed along the said recovery device increases its speed along the path towards the rotor.
9. A rotor (I' ) , according to claim 8, wherein the said recovery device comprises two hinge arms (204) for connecting the device to the rotor (I' ) through two shafts (7', 7") and at least a tab (203), preferably two opposed tabs, connected to the said arms in the hinge points and that extend posteriorly to the exit section in such a way as to be able to be self- oriented on the basis of the direction of the flow that collides with it.
10. A rotor (1'), according to claim 8, wherein the recovery device comprises a servo-controlled orientation system.
11. A rotor (1'), according to one or more of the preceding claims from 8 to 10, wherein the exit section (202) has an airfoil that substantially traces the external profile of the rotor (I' ) in such a way that the device is arranged close to the rotor itself.
12. A rotor (1'), according to one or more of the preceding claims from 8 to 11, wherein the said recovery device (200) comprises two or more internal channels (210', 210'') into which the fluid is directed towards the exit section (202), the said channels being configured in such a way as to direct the fluid in a substantially tangential manner to the airfoil of the blades that face each channel.
13. A rotor (1'), according to claim 12, wherein the exit section (202) substantially traces half of the external profile of the rotor.
14. A rotor (1'), according to claim 1, wherein adjustment means are comprised to change the blade pitch angle of the blades.
15. A rotor (1'), according to claim 14, wherein the said adjustment means comprise:
- A circular crown (410) at least partially dented and concentric to the blades;
- At least one, preferably two rotatable control gear wheels (401) internally coupled to the crown in such a way that the rotation of the said control wheels (401) causes the rotation of the circular crown (410) and;
- Two gear wheels (400) , preferably diametrically opposed, each one connected in the hinging point of a blade in such a manner that the rotation of the said wheel (400) rigidly drags in rotation the blade, changing its blade pitch angle;
and wherein the said wheels (400) are meshed with the circular crown (410) in such a way that the rotation of the said crown (410), through the setting in rotation of the control wheels (401) , causes the rotation of the blades connected to the wheels (400) and wherein, further, all the blades are reciprocally connected through the leading edge by hinged arms (501) in such a way that the rotation of the wheels (400) is transmitted rigidly to all the remaining blades, causing an equivalent change of blade pitch angle.
16. A rotor (1'), according to claim 14, wherein the said adjustment means comprise a pair of irreversible actuators (500) fixed at the ends of two blades diametrically opposed, together with the connecting system of all the blades with hinged arms (501) .
17. A rotor (1'), according to claim 1, wherein the said bulkheads (2, 3) have a surface, that faces the internal chamber (20) of the rotor, shaped so as to restrict progressively the internal volume of the chamber, producing a reduction of pressure and an increase in the speed of the flow inside the rotor.
18. An aero-generator comprising a supporting base (12) and a rotor (1') as per one or more of the preceding claims from 1 to 17, arranged vertically in a rotatable manner on the supporting base in such a way as to be able to rotate around a vertical axis (7) and wherein, further, an electric current generator (9; 109) is comprised, connected to the rotor in such a way that the rotation of the rotor causes the production of current through the generator.
EP10754561A 2009-07-31 2010-07-30 Aerogenerator with free internal flow rotor Withdrawn EP2459871A2 (en)

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IT1397762B1 (en) 2013-01-24

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