WO2013080192A1 - Cyclonic vertical axis wind turbine with a wind guide - Google Patents

Abstract

Impinging wind air is injected in form of a plurality of regularly distributed streams of accelerated air, all with a horizontal component of velocity that has a substantially constant angle of incidence on the surface of a traveling rotor blade (7) and a vertical component that has an angle of inclination in respect of the axis of the rotor space (2) toward an open end thereof. A regular distribution of these injected air streams, around preferably the whole circumference of the rotor space (2) as well as along its whole axial extension, generates and sustains a swirling motion of the air "biased" in a given axial direction, enhancing absorption by the rotor (6) of most of the available kinetic energy. Contravening common practice with inner multi-blade rotors and outer air diverters, the rotor blades (7) preferably have a concave leading surface and a convex trailing surface besides helicoidally extending along the rotor shaft (10). Convexity of the trailing surface of the rotor blades is instrumental to keep incidence of the injected air normal to the surface of a curved blade traveling across the injection window of each air stream. Equivalence of the two torque production modes: direct thrust on the blade surface and aerodynamic lift, is substantially achieved in the inner rotor space, and a favorably significant pressure difference between the inner rotor space and outside air is also created. Most preferably, a feathering, wind intercepting collector (8) may be deployed, free to swing around the stationary tubular honeycomb structure of the air distributing stator (1) in positioning itself leeward of it. The inward surface of the feathering collector (8) facing toward the honeycomb stator (1) has a cross sectional profile with a central cusp (8') traveling at a clearance distance as small as feasible from the honeycomb structure of the stator (1). The air intercepted by the windward intakes of the two air spaces that flank the portion of the tubular honeycomb stator directly taking the wind, is progressively deflected to flow through leeward flow sectors (4) of the tubular honeycomb enhancing a substantial symmetry and speed of the air vortex that moves the rotor (6).

Description

CYCLONIC VERTICAL AXIS WIND TURBINE WITH A WIND GUIDE

TECHNICAL FIELD

This disclosure relates in general to Aeolian generators and in particular to vertical axis wind turbines (VAWTs). DISCUSSION OF PRIOR ART AND BACKGROUND

Betz's limit, the physical-mathematical deduction of which is well known, represents the maximum theoretical efficiency of an ideal rotor of surface S absorbing energy from a fluid of density p flowing at a certain velocity v¾ (the equivalent for the efficiency of the Carnot cycle for a thermal machine). By defining the efficiency coefficient C_e as the ratio between the power P absorbed by the rotor and the maximum theoretically available power P_max

the value of such a limit value of efficiency equals:

C_e =— =— = 59.26% (2)

P 27 obtained in correspondence of a ratio between the incident velocity of the fluid v¾ and the exit velocity from the rotor v_out equal to one third {Betz's Condition):

L- ₌I ₍₃₎

Modern rotors achieve a peak efficiency coefficient C_e in the interval from 0.4 to 0.5, and hardly surpass 70-80% of the theoretical Betz's limit efficiency. Traditional wind turbines have a plurality of blades extending from a horizontal shaft directly coupled to the rotor of an electrical machine, normally contained in a nacelle sustained at the top of a high rising tower (also for best exploiting the wind, the velocity of which notably increases with height from the ground). These characteristics represent also a limit to the realization of wind generators more powerful than those deployed so far because of an uneconomical stretching out of static and dynamic requirements. The largest machines have a rotor diameter of 70 m and tower height of 130 m. For such a machine, the diameter at the base of the tower may be over 20 m, which implies the realization of complex and costly foundations. Moreover, sophisticated safety systems must be deployed in order to cope with wind gusts of exceptional strength. The location of the alternator and of mobile parts exposed to wear from the atmospheric agents implies high maintenance costs.

Vertical axis wind turbines of the so-called Savonius type have been conceived and deployed since 1920 and more recently also of the so-called Darrieus and Windside types, however their significantly lower efficiency C_e = 0.3 compared to traditional horizontal axis turbines has restricted their use in the mini-Aeolian and micro-Aeolian segments of the wind generator industry.

Nevertheless, vertical axis turbines have the advantage of independence from the wind direction, a greater tolerance of strong wind regimes even in presence of turbulences and a reduced noise emission.

The lower efficiency is in part due to the fact that, differently from the traditional horizontal axis turbines, the blades of which have an airfoil (wing) profile for exploiting the airlift effect, in the vertical axis turbines the blades have generally a much less efficient shape (typically of a sail for stern winds or of a helical turbine blade) and a generally more important "passive" phase due to blades traveling windward for a good part of their revolution (practically acting as air-brakes), thus limiting exploitation of only a positive torque difference, and because part of the available kinetic energy of wind air hitting the rotor blades is expended in producing air vortexes that disperse with a large amount of residual swirl and/or turbulences in free air.

Innumerable attempts to lessen these problems have followed the approach of increasing the number of mobile parts, detracting from sturdiness and reliability, or of shielding from the wind the blades during their upwind travel, which implies the need of orienting the turbine depending on the wind direction, thus detracting many of the advantages of the vertical axis.

AU2006233265-A1 describes a fixed tower for converting wind energy in electricity with a vertical axis turbine.

EP1350952-A1 describes a vertical axis turbine having a hollow cylindrical rotor with vertically extending concave blades at its periphery, having an impervious part of their concavity (kinetic energy absorbing portion) and an air pervious part (for reducing its braking effect when moving upwind), surrounded by a control stator composed of radial vanes with air deflecting curved inner edge portion and preferably with an outer edge of variable geometry. The circular control stator is confined between a circular truncated cone basement, housing an electrical generating machine driven by the wind turbine, and an inverted truncated cone circular cover, which is elastically displaceable up-and- down by changing wind pressure, for acting upon gravity biased flaps in the radial flow conduits between adjacent radial vanes. Most of the intercepted wind air stream strikes horizontally the vertical cylindrical rotor and the control stator, apart from a minor release of air through openings at the upper end of the hollow cylindrical rotor, any effect of which would equally affects all the rotor blades.

EP1367257-A2 describes a vertical axis turbine having a rotor with vertical blades confined in a housing composed of differently oriented baffle walls, among which a first convex windward surface wall shrouds the rotor blades moving in an upwind direction and cooperates with a second baffle wall that inverts the direction of the air diverted by the first baffle wall, and a third baffle wall diverts wind air towards the rotor blades. The multiple baffle housing must be aligned with the wind direction mechanically or by remote control. The intercepted wind air stream is led to strike horizontally the vertical multi-blade rotor with inhomogeneous effects on opposed equally-shaped blades.

CN101387265-A describes a vertical axis turbine having a cylindrical rotor with vertical concave blades held in a casing having a wind intake opening which is oriented windward by a dedicated horizontal cantilever finned tail of the pivot-sustained turbine assembly. A convex windward surface baffle wall of the casing shrouds the rotor blades moving in an upwind direction, to reduce passive power. The intercepted wind air stream strikes horizontally the vertical cylindrical rotor.

WO2011032249- Al describes an improved core structure of hollow helical blade rotor of an open rotor type (Darrieus) wind turbine with a rather complex inner helical vanes cooperating with axially spaced stacks of parallel disks for enhancing maintenance of an air vortex generated in the core space by the outer helical blades and thus recover some kinetic energy spent by in creating it. The intercepted wind air stream is led to strike horizontally the vertical rotor. US20110006542-A1 describes a plurality of different fluid diverting implements adapted to a helical turbine rotor that are allegedly combinable to some extent according to needs. Among the disclosed implements there is also a shrouding casing for preventing air to impinge on upwind moving helical blades of the rotor while the intercepted wind air stream is led to strike horizontally on the vertical helical blade rotor.

US20100143096-A1 describes a vertical axis turbine set on a turntable platform at the top of a tower having a casing that is oriented by dedicated cantilever finned tails such to orient a wind intake toward the wind direction of provenience. Intercepted wind air is led by parallel fed curved vertical walls of gradually increasing length (and thence of hardly uniform distributive effect) such to reach also leeward portions of a multi-vane stator diverting the incoming air streams to strike upper impeller blades and lower impeller blades of opposite twist, of one or preferably two identical turbine rotors. The two sections of opposite twist of the rotor impeller expel the horizontally impinging air upward and downward, respectively, which is then ducted by the casing to exit in a horizontal downwind direction, streaming along the turbine orienting fins.

US6015258, US6740989, US2006275105-A1, US2007296219-A1, US20020047276- Al and US5391926 are other publications on the subject of vertical axis wind turbines. GENERAL DESCRIPTION OF THE INVENTION

To the above discussed limitations and penalizing characteristics of vertical axis wind turbines, the applicant has found a surprisingly effective solution, of simple and reliable implementation and that does not materially subtract any of the intrinsic characteristics and advantages of this class of wind turbines.

The novel Aeolian (wind) generator of this disclosure may be qualified as "cyclonic" (in short hand referred to by a phonetic acronym CEG) because contrary to prior art architectures of VAWTs, where the intercepted wind air stream is generally led to transversally impinge on a vertical cylindrical rotor, in the novel VAWT of this disclosure, a rotor, generally having several blades that extend for the whole axial length of the rotor, is moved by a swirling stream of air axially moving toward an open end (air discharge) of an inner space of cylindrical symmetry containing the rotor, into which intercepted wind air is injected in form of a plurality of regularly distributed streams of accelerated air, all with a horizontal component of velocity that has a substantially constant angle of incidence on the blade (i.e. an incidence angle that substantially remains constant as the blades travel across one of the injected streams) and with a vertical component that has an angle of inclination in respect of the axis of the rotor space toward the open end thereof. These conditions, coupled with a regular distribution of these injected air streams around a good part or preferably the whole circumference of the rotor space as well as along its whole axial extension, cooperate in generating and sustaining an air vortex "biased" in a design axial direction (for example downward), minimizing turbulence. This has been found to minimize energy losses and enhance absorption by the rotor of a greater amount of the kinetic energy available in the impinging wind air. The rotor blades have a cross sectional airfoil profile adapted to exploit a thrust onto the blade surface that is stricken by contiguously injected substantially identical accelerated air streams, regularly distributed around the whole circumference, as well as an aerodynamic lift force by the circular motion of the air in the rotor space and, according to the preferred embodiment wherein the blades extend helicoidally along the rotor axle, even a further push by the downward-biased motion component of the swirling air stream. Thus, to the output power may concur not only accelerated air thrust on the blades as in common vertical axis wind turbines, but also a substantially constant aerodynamic lift force acting on the blades and eventually even a vacuum effect due to a pressure gradient that is created between the inner rotor space and the outside zone of air discharge from the turbine, as will be explained later.

Only for ease of expression this description refers to vertical axis and directions, to top and bottom or alike expressions, proper for a vertical axis application, typical of an Aeolian (wind) power generator exploiting surface winds, but this must not be intended to limit utility and scope of this invention to such geodetic orientation because other orientations are possible.

Basically, the inner space containing the rotor (rotor space) is defined by a surrounding fixed (stationary), multi-tier honeycomb- like structure having an overall tubular shape, which, in functional terming, may be referred to as "air distributing stator" or shortly "stator". In a cross sectional view, the stator may have a generally circular inner perimeter and a generally polygonal outer perimeter.

The inner space of cylindrical symmetry may have a constant cross sectional area (e.g. a cylindrical rotor space) or it may have any gradually varying cross sectional area (e.g. a truncated cone rotor space). Of course, the rotor blades will correspondingly have a constant width or a gradually varying width in a radial direction, such for their edges to safely travel at the smallest clearance distance from the surrounding stationary, honeycomb-like, structure of the stator. Although a truncated cone shaped rotor and rotor space may, on one hand, reduce a marginal pressure drop contribution, under certain prevailing wind conditions this could be overcompensated by an enhanced aerodynamic lift force and this design choice could be rewarding for applications that contemplate a prevalence of exceptionally strong wind speed regimes.

Along its axial length, the tubular honeycomb structure of the air distributing stator may be seen as modularly divided by annular truncated cone tier-diaphragms (plates) present at a regular distance of separation from one another, starting from a first conical plate or truncated cone plate as the others but the central hole of which is occluded by a cap, preferably having an inverted cone shape of conicity identical to that of the conical tier diaphragms of the surrounding honeycomb stator, in order to seal at one end, normally at the top end, the rotor space. Occlusion of the end of the rotor space and absence of any empty space where air might escape off conically slanted ends of the rotor blades may alternatively be accomplished by fixing a conical end cap to conically slanted ends of the rotor blades or terminating a molded monolithic rotor with a conical end cap.

The transverse annular diaphragms of the honeycomb stator are all conical such that the annular modules have a constant height and are all slanted in the same axial direction. Therefore, the velocity of the impinging wind air that flows there through toward the inner rotor space assumes a vertical component before reaching it.

The annular volume of each module defined between the conical surfaces of two consecutive annular tier-diaphragms, is circumferentially divided by curving walls (baffles) in a number of identical curving sectors or flow conduits of constant height, of circumferential air distribution and injection into the rotor space. The cross sectional area of the flow conduits gradually decreases toward the inward end of the conduit, thus deflecting and accelerating the air that enters the curving conduit in its movement toward the inner rotor space.

Although the tangential and vertical components of injection velocity of the distinct accelerated air streams exiting the respective flow sectors lead to the generation and sustainment of a swirling motion of the air "biased" in a given axial direction, by virtue of the peripheral pressure gradient of the vortex generated in the inner rotor space, deployment of a relatively lightweight feathering wind intercepting collector is highly beneficial to enhance efficiency and power yield. The feathering wind collector is normally free to swing around the stationary tubular honeycomb structure of the air distributing stator, at a distance from the outer surface thereof, for positioning itself leeward of the stator, practically "covering" the leeward side of it.

The inward surface of the feathering collector facing toward the honeycomb stator has a cross section profile with a central cusp, preferably it may have the shape of a symmetric cardioid, intending with this a real-world approximation to such a mathematically defined curve, the central cusp of which projects inward as far as traveling at a clearance distance as small as safely feasible from the honeycomb structure of the stator. The feathering collector defines two air spaces between it and the air distributing stator that are open to the wind, along diametrically opposite flanks of the tubular honeycomb structure of the stator, respectively, and separated by the central cusp of the collector. The air intercepted by such windward intakes of the two air spaces, flanking the portion of the tubular honeycomb stator directly taking the wind, is progressively deflected to flow through leeward flow sectors (conduits) of the tubular honeycomb to be finally injected as well as sucked into the inner rotor space by the peripheral pressure gradient of the vortex therein, with horizontal and vertical velocity components of the injected air streams similar to those of the flow sectors of the portion of the tubular honeycomb stator directly exposed to the wind or not shrouded by the feathering collector. Therefore, also the injected air streams of the leeward side sectors cooperate with those of the windward sectors in generating and sustaining a downward swirling (cyclonic) flow of the intercepted wind air with a substantial symmetry of front and rear semicircular regions of the vortex in the rotor space that moves the rotor.

The feathering collector may generally have a semi-cylindrical outer wall, with or without a leeward biasing fin, and preferably at the upper and lower ends thereof there should preferably be flange-like parts, for example in form of semicircular crown pieces, adapted to occlude significant escape throughways of the intercepted wind air. The feathering collector may be sustained, at both the lower and upper ends, on low friction rolls or wheels travelling in circular tracks on horizontal planes of an appropriate fixed structure. For example the annular tier-diaphragms at the top and bottom ends of the tubular honeycomb structure of the stator, may be purposely made with a robust horizontally extending flange-like part with a circular guides into which may rest and run cantilever-held wheels of the feathering collector, securely retained into the channel-like guides by appropriate stoppers or any equivalent retention fixture. Alternatively, the feathering collector may be sustained and retained on the same static structure (single steel pole or a latticework tower) that sustains the honeycomb stator or even by a dedicated ancillary structure without any direct mechanical coupling with the stator-rotor assembly.

Such a lightweight feathering wind collector is the part most stressed by exceptionally strong wind blows and its structure and retention means must comply with regulatory safety specifications. Therefore, specially for large size turbines, it may even have a composite structure comprising a metal or fiber reinforced rigid framework, with support wheels or rollers securely connected thereto, suited to hold in shape a windblown stress resistant textile sheet, having battens adapted to snap off upper and lower retention channels of the rigid framework, or even predefined weakened lines along which eventually rupture in case of hurricane level winds in order to relieve excessively high mechanical stresses on the structure holding the CEG at the desired height from the ground.

Of course, in case of a gradually varying cross sectional area of the inner rotor space, the fixed, honeycomb structure of the stator may assume a similarly varying outer profile for retaining a sufficient length of the curving flow conduits to produce an effective acceleration of the air streaming there through, and even the feathering wind collector may assume a similarly varying cross sectional profiles of inward and outer surfaces for maintaining a relatively constant quantity of air that is intercepted and deflected inward by the central cusp, at different elevation levels. As will be remarked along the ensuing detailed description and analysis of exemplary embodiments, making reference to the attached drawings, the architecture of the turbine of this disclosure lends itself to be designed in a way to be composed of any number of elements or modules of practically identical geometry. Moreover, through extremely simplified relationships to the nominal power rating of the turbine, numerosity, dimensional ratios and angles of incidence may be quickly established for the requested nominal power rating.

For sake of simplicity, mathematical analysis and detailed description of embodiments will generally refer to a canonical and simple cylindrical rotor and rotor space configuration, though they hold, mutatis mutandis, also for configurations with a gradually varying cross sectional area of the rotor space.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a partially exploded three-dimensional schematic illustration of a wind generator according to an exemplary embodiment of this invention.

Fig. 2 is a simplified geometric representation of the stationary honeycomb-like structure of collection-deflection- injection of air in an inner space containing the rotor.

Fig. 3 is a geometric construction illustrating important parameters of the horizontal cross-section of a radial flow conduit of the stationary honeycomb- like structure. Fig. 4 is a simplified horizontal cross sectional view of the outer feathering collector and of the underlying honeycomb-like structure of the air distributing stator.

Fig. 5 is a detail geometric construction that illustrates the convergent orientation of idealized air streamlines at the exit of a radial flow conduit, in correspondence of a rectilinear tract of extension of the cycloid arc main part of the generally curving side walls of the conduit, upon approaching its exit toward the inner rotor space.

Fig. 6 shows the different orthogonal components of velocity of the incident air at the intakes of windward radial flow conduits of the tubular honeycomb-like stator in function of the respective angle of incidence of the wind.

Fig. 7 shows one pair of helicoidally extending rotor blades. Fig. 8 illustrates the cross sectional profile of a rotor blade hit by the air stream injected in the inner rotor space and the impact on its convex surface of the components of velocity of air while the blade rotates.

Fig. 9a shows the composed tangential velocities of air produced by the oriented accelerated air streams that are injected in correspondence of the distinct front sectors directly taking the wind, in absence of rotor blades and the resultant accelerated swirling air stream in the rotor space these front streams produce. Fig. 9b highlights in a schematic manner the effect of the outer feathering collector in duplicating the same composition of tangential velocities of air produced by the oriented accelerated air streams that are injected through the distinct leeward sectors.

DETAILED DESCRIPTION AND THEORETICAL ANALYSYS OF EXEMPLARY EMBODIMENTS

The ensuing description of embodiments has solely illustrative purposes and is not to be intended as limiting the scope of the claimed invention, which may be practiced in innumerable different embodiments, making alternative design choices such as modifying the number of annular stator modules and/or of radial flow conduits per module, the number and shape of the rotor blades, the ratio between horizontal and vertical components of velocity of air injected into the inner rotor space, the profiles of the inner rotor space, of the axially extending edges of the blades and of the outer feathering collector and other fabrication choices, though remaining within the scope of this invention as defined in the annexed claims. Curvature of the flow conduits of the multi-tier honeycomb stator

Referring to Fig 1, the vertical side walls (baffles) 4 that delimit each flow conduit or flow sector 5 of each annular module of the tubular multi-tiers honeycomb stator 1, approximate for a good portion of their length two identical arcs of a cycloid or of a parabola, or a real-world approximation of such mathematically defined curves. This type of curvature is found to minimize turbulence in the accelerating air stream and a possible explanation for the cycloid choice is offered herein below.

Starting from peculiarities of motion of a point-like mass on a vertical plane under gravity, and from mathematically verified validity of the findings also when accelerated motion takes place frictionless on a horizontal plane. In the construction of Fig. 3, the arc of cycloid comprised between point A and point B has the parametrical equation: x =— (O + sin O) y =— (l + cos 0) (4) where < θ <— is the angle formed with the vertical direction by the vector radius of the point P, at the border of the generator circle, which describes the arc when the circle rolls without slipping, along the abscissa axis. Differentiating equations (4) in respect to the angle θ , it is found that the speed along the trajectory forms an angle a with the horizontal starting direction given by: dy _ Θ

- arctan (5) dx 2

Through a curving flow sector (conduit) having an initial square cross sectional area of side length D and where the vertical side walls of which may be assumed to be two cycloid arcs, converging with an angle of about 30° formed by the respective tangent lines at every point of the arcs, the flow of air entering the largest, initially square cross sectional intake is subjected to an acceleration by the tunnel effect, inversely proportional to the narrowing of the flow cross sectional area that, in first approximation, progresses linearly according to the straight line t of Fig. 3; the equation describing it being:

The air velocity increment, in function of the angle θ , is proportional to the sine of the angle a =— within the considered interval 0 < Θ <— :

^& 2 2 v(0) = v_e oc sin- (V)

The stream-lines within each flow conduit or sector of the air distributing stator, preferably enter the inner rotor space with an inclination on the horizontal plane toward the right side of the radius of the rotor space generally comprised between 40° and 50°, preferably of about 45°. This in combination with a coordinately designed profile of the surface of the rotor blades and other theoretically founded features is found to dramatically increase efficiency. An almost equivalent effect may be obtained also with baffles curved in an arc of parabola instead of an arc of cycloid. As a matter of fact, the numeric value of Betz's limit: 16/27, can be viewed as the product of two numbers, Λ/2 / 2 = cos(45°) times (2V2 /3)³ = cos³ φ , where φ is the angle whose sine is 1/3 (re: relation (3), Betz's Condition) and the third power draws attention to the cube of the speed in the expression of the energy carried by the wind.

Stationary honeycomb-like tubular structure (Stator)

Referring to Fig. 1, the cyclonic wind generator has a fixed tubular multi-tier honeycomb structure (stator) 1 that, in a layout view, has a circular inner perimeter and a polygonal outer perimeter. In the considered example, the structure comprises four identical annular modules delimited by annular truncated cone diaphragms 3. Each annular module is divided in twelve curved sectors 5, assuming a general outer aspect of a dodecagonal prism with an axial hole defining an inner cylindrical space 2, adapted to accommodate the rotor 6, as better observable in Fig. 2. The letter D indicates the length of the sides of the polygon of the outer perimeter of the structure (i.e. the width of the air intake of a flow conduit). In the illustrated embodiment, the height of each module is made equal to its width D at the outer air intake. This choice has the advantage of simplifying the analysis by having a unique parameter and its uniqueness is also useful to the designer for more readily defining all the related proportions when scaling the turbine for the required nominal power rating, as will become evident in the ensuing description.

The flow sectors 5 (twelve for the illustrated embodiment) are defined by identical vertical sidewalls (baffles) 4 (of constant height D according to the above considerations and design choice) are curving for most of their extension, starting from the outer or intake edge, preferably in form of either a cycloid arc, as depicted in Fig. 3, or an arc of parabola or a real-world approximation to such a mathematically defined curves,. In the considered sample embodiment of Fig. 3, the parametric equations of the horizontal cross section of a sidewall or baffle 4, from point A to point B, has the equations (4). The innermost tract BB' is a rectilinear extension of the cycloid arc portion ¾B of the baffle, which forms an angle of 45° with the vertical axis. The counter-opposed annular surfaces of tier diaphragms of the tubular honeycomb structure that define an annular module there between or in other words the bottom and top, respectively, of each curving flow conduit or sector of the module, may be those of annular truncated cone plates 3, solidly connected to support risers 9 of the tubular honeycomb stator 1 , the conicity of which, in the illustrated embodiment, makes for an angle φ of inclination of the conical plates from the horizontal plane, such that simp = i and cos<p =—^- ( φ = 19° 28' 16"). Alternatively, the counter-opposed annular truncated cone surfaces could be of modularly stackable identical injection molded pieces with dovetail fixtures for a stator assembly employing tie rods for compressing the stacked injection molded honeycomb components between top and bottom compression plates, solidly connected to support struts.

Referring to the construction of Fig. 2, one gets the following geometrical proportions:

sin E-T¹ ₌ ,^l±^ _Rj i .93 l 852. ⁾ (8) 12 2

d = 2r sin— » 0.564333 £> (10) 12

Α = ίΐ₊£Ί₈ί^ηφ = ίΐ₊ « Ο.297566 · Ζ⁾ (1 1) where R is the radius of the circumscriptive circle of the outer polygonal perimeter of the stator, r is the radius of the inner cylindrical space (in this embodiment), d is the width of the flow conduits or sectors at their outlet, and h is the difference of elevation between the outer intake and the inward outlet of the air flow conduits across the tubular honeycomb stator. Feathering wind collector

Referring to the exploded, three dimensional schematic representation of Fig. 1, a feathering wind collector 8 may be axially pivoted atop the fixed stator structure and/or held in any equivalent manner adapted to broadly shroud, at a distance and for approximately half a circumference, the leeward side of the honeycomb stator 1, under ordinary working conditions of the turbine. Although similar shapes may also work properly, the inward (windward) surface of the feathering wind collector 8 has preferably a cross sectional profile shape of a symmetrical cardioid or a real-world approximation to such a mathematically defined curve, the central cusp 8' of which projects inward as far as traveling at a clearance distance as small as safely feasible from the honeycomb structure 1. The feathering collector defines two air spaces between it and the air distributing stator open to the wind, along diametrically opposite flanks of the tubular honeycomb structure of the stator, separated by the central cusp 8' of the wind collector. The phantom profile of the wind collector 8, traced with interrupted lines, shows its real working position.

The air intercepted into such windward intakes of the air spaces, flanking the portion of the tubular honeycomb stator 1 directly exposed to the wind, is progressively deflected to flow through the leeward flow sectors 5 (shrouded by the semi-circumferentially extending feathering collector) of the tubular honeycomb stator 1 , to be finally injected into the inner rotor space, with horizontal and vertical velocity components of the injected air streams of equivalent magnitudes, in a mirror-like manner to those of the streams exiting the flow sectors of the portion of the tubular honeycomb stator 1 taking directly the wind (i.e. not shrouded by the feathering collector). Therefore, every stream of injected air cooperates in generating and sustaining the downward swirling (cyclonic) motion of the accelerated air that because of an enhanced constancy of its tangential speed around the whole circumference and for the whole height of the rotor space, promotes constancy of the torque that is applied on all the rotor blades 7. The preferred shape of the feathering collector 8, and particularly of its inward surface, found to be most effective, is that shown in the geometrical construction of Fig. 4, of an arc of cardioid, the describing equation of it being: x² + y² - 2ax = a² x² + y² ^ (12) with

In Fig. 4, the arc is limited by the two end points P(R, 2R) and Q(R, -2R) .

By virtue of its shape and of its mechanical restraints, the collector 8 is able to position itself by the effect of the wind thrust in an ideal position and deflect progressively the intercepted wind air along the two air spaces into the leeward flow sectors of the tubular honeycomb stator with substantially uniform distribution, to be finally injected in the inner rotor space in a mirror-like manner as the air flowing through the sectors of the windward portion of the tubular honeycomb stator 1 , the intakes of which directly intercept the wind. An attendant action of the wind collector is that of nullifying the edge effect which would tend to reduce the effective area of wind interception of the exposed portion of the tubular honeycomb stator and to raise the minimum wind velocity required for starting to move the idling rotor. Preferably, bottom and top of the two air spaces should be at least partially occluded by similar roof and floor parts, for example in form of semicircular crown pieces. In the simplified schematic illustration of Fig. 1, the feathering collector 8 , drawn as pivotally restrained at 14 along the axis of rotation of the turbine, may be sustained and restrained at its base to prevent flections. For example, at the base of the collector 8 there may be low friction revolving wheels or rollers 17 engaged into a circular run track channel 12.

The freely feathering collector 8 may eventually be forcibly turned and locked in a position facing toward the wind direction for shrouding stator and rotor from the wind and allowing maintenance operations even in presence of wind blows. Velocity of injection of air in the inner rotor space

At normal wind regimes, the air density p may be considered constant while traversing the tubular honeycomb stator 1, flowing in the plurality of curving flow sectors or conduits 5. Being constant mass and volumetric flow rate, one has m = pSv = const , therefore v_e - S = v_t - s (14) where v_e is the external wind speed (speed of the air at the intake of a flow conduit), v_;. is the injection air speed at the exit of the flow conduit, S = D² is the cross sectional area at the external intake of every conduit, s is the cross sectional area at the exit, with S and s orthogonal to the stream-lines. Calculation of s is rather simple, being, for the exemplary embodiment analyzed, the direction of the flow lines of the injected air stream constantly at 45° from the radial direction.

Referring to the geometrical construction of Fig. 5, about the inner end (traced with a heavy line) of anyone of the flow sectors 5 of the stator, the lines of extension of the vertical side walls (baffles) of the flow conduit meet at a point E into the rotor space. Indicating with A and B the ends of the arc of circumference of the inner rotor space of cylindrical symmetry, the following geometric relationships hold:

ABE = AEB =— AB = AE = d EB = ED = d (15) sought surface area orthogonal to the stream lines has, as a projection of it, the = / , representative of the tube of flow, that is s = D l = D d i— 0.511793 £> (16)

Thence, v. = -v « 1.953915 · ν (17) Therefore, the velocity on injection of the air is almost twice that of the wind. Available power is proportionately greater and the useful surface of incidence is proportionately smaller.

Surface of incidence According to a noteworthy aspect of the novel turbine of this disclosure, the blade surface is made to remain substantially orthogonal to the flow lines of the air jets while traveling in front of any flow sector outlet. As depicted in Fig.5, taking into account the flow lines of an injected air stream, the orthogonal projection of a rotor blade intercepting them would be an arc of circumference centered in E. The length of this arc varies with the angular position of a blade of radius r rotating in a counterclockwise direction around the rotor axis at O, being the arcs of orthogonal projection of the desired surface "confined" by the bounds EB and AE of the flow tube and by the arc ¾ of the profile of the rotor space of cylindrical symmetry. The sought arc length of the desired blade surface varies from zero when the edge of the blade travels over point B to a maximum represented by the arc — d « 0.523599 · d , for becoming zero

6

again when traveling past point E. Its mean length will be intermediate between 0 and 0.5236 times d and, by calculation, is found to be:

l' = d£- s 0.347792 - (18)

Being D the height of each flow sector (conduit) and of a correspondent portion of an impacted blade, the effective surface of incidence, considering equation (10), has an area of injection into the inner rotor space given by

4 = 0.347792 - d - Z) = 0.196271 - Z)² (19) Theoretically available wind power

The surface of each annular module directly exposed to the wind of the tubular honeycomb stator is independent from the orientation of its prismatic outer surface, and, for the two limit positions depicted in Fig. 6, measures

A = D\ D + 2D cos

A 3.732051 -D¹ (20) and indicating with N the number of identical annular modules of the tubular honeycomb structure, in function of the wind speed v_e , the available power due to wind pressure over the front of the structure (i.e. facing windward) is

Numerically, given p = 1.16 Kg/m , D = 1.2 m and N = 4, for a wind speed of 10 m/s, the available power would be

12.4680 kW (21b)

In the inner rotor space, each flow sector contributes to the available power by an amount tied to the inclination of its intake cross sectional area from the wind direction. Referring to Fig. 6, and in consideration of the relation (17) between v_t and v_e , one has: if > v (22)

/ ⁾ pND¹ - 0.950966 - (23) (^0> v - pND¹ - 0.1830135 - (24)

2 The available power in the inner rotor space is the sum of all contributions if" = X f^] = if ' + 2i + 2T ^] (25)

Numerically, given p = 1.16 Kg/m³, D = 1.2 m and N = 4, for a wind speed of 10 m/s, the available power would be if" = 12.4680 kW (25b)

As expected, the available power in the inner rotor space, neglecting viscosity of air and related frictional phenomena, is the same as that hitting the exterior of the tubular honeycomb stator directly exposed to the wind.

Convertible power in the inner rotor space

The injection velocity of air v_t may be decomposed in a horizontal component,

, and in a vertical component,

, respectively:

(*) ^ .^v_e = 1.842169 - v_e (26) v_e = 0.651305 - v_e (27)

Assuming to be in condition of neglecting frictional forces acting on the rotor, work on rotor blades, in a direction laying in the plane orthogonal to the axis of rotation, is done exclusively by the horizontal component

. By substituting it into (22), (23) and (24), and considering the projection of the outlet surface area of the flow conduit orthogonal to the horizontal component of the air velocity, 4 cos^- , the power transferred to the rotor, by summing as in (25), is

1 π

P =— pNA_i cos— 1 + 2| cos— + 2 cos—

' 2 4 6 J 3 ^~ [ν,^(¾)Τ (28)

Thence:

Considering null the braking effect of blades traveling toward the wind source and negligible other energy losses due to turbulence, non-adiabatic kinetic energy transfer and internal frictional forces, the efficiency of the wind turbine coincides with the Betz's limit.

Aerodynamic lift effect by the swirling motion of air in the inner rotor space

In absence of a rotor, the air injected in the inner space of cylindrical symmetry, not impacting on any blade moves straight ahead as far as intersecting the stream exiting the next flow channel at a constant angle of about 30° (in the preferred embodiment considered) and merges with it, summing vectorially their respective velocities. The modulus of the resultant tangential velocity that would be created in the rotor space, in correspondence of the respective pair of adjacent flow sectors of the windward side of the honeycomb stator is proportionately represented by the heavily traced arrows depicted in the partial (front side) geometrical construction drawing of Fig. 9a. The modulus may be calculated through elementary geometrical considerations that, for the sequence of the front side sectors, give

Passing from a flow sector directly exposed to the wind to the next, the tangential speed of the air increases as far as passing from sector ¾ to S3, when ceases the contribution of these windward flow sectors of the stator.

A rotor blade traveling by the six phases of speed increment would be subject to acceleration at every line of merging of injected streams of accelerated air, except at the last step where it is subject to a deceleration. The power associated to these accelerations by "air lift" may be easily calculated on the basis of the following considerations of general validity.

Be v_b the tangential velocity of air on the trailing side of a rotor blade and v_a the velocity on the leading side of it, with v_a > v_b orthogonal to the blade surface. Thence, the pressure gradient and kinetic energy available are respectively given by:

By differentiating the kinetic energy change and considering the flow rate expression at constant density m = pAv , the associated power P becomes:

P = E = - m (vl - vl ) = -pAv (vl - vl (34)

On the other hand, from dynamical considerations one has that:

P = F v - ■ mAv■ v = pAv (v (35) dt

By equating (34) and (35), the mean speed value is found:

Therefore, the aerodynamic lift power is

Here A_l indicates the cross sectional area of the whirl, or the surface portion of each single blade (for one module of the stator) orthogonal to the flow, that is affected by a pressure gradient between its opposite side surfaces. The area A_l will have height D and depth equal to the thickness of the envelope of the streamlines relative to the tangential motion of the air that, in first approximation, would be the BC segment in the geometrical construction of Fig. 9a (i.e. half of the segment AB ) or more exactly reduced by the nominal thickness of the boundary layer of laminar flow:

4 = sin · -^= ) · ^{d D} = 0.2575915 · d D = 0.1453674 D² (38) where Re = ^P ^ ή^η(π /12) v^. _{= 44455} ^ ^ R_ey_noi₍j'_s number, having considered a μ -η

dynamical viscosity of air μ = 1.82· 10^"5 N-s/m² , an external velocity of the air v_e of 10 m/s, and taken the dimensionless parameter η = 4.91 from Blasius's theory for the boundary layer over a planar surface.

The surface area of incidence on a blade A_l , over which acts the pressure gradient, is smaller than the area of incidence A_i considered in the previous chapter because in the air-lift mechanism only a fraction of the air injected through any flow sector reaches the stream of air injected through the next flow sector, merging with it and producing an accelerated air stream. In particular the edge of the blade would not experience any pressure gradient (same tangential air speed on leading and trailing surfaces of the blade), which qualitatively explains why A, < A_i .

By applying (37) for calculating the available power P_l ⁽ⁿ⁾ in traveling by successive flow sectors, S_n and S_n+l , where v_b = v(S_n) and v_a = v(S_n+l) , one gets:

(39)

9lV2 25Λ/6 91 2Υ ^ 25Λ/ /67 Υ

= - PN4 (43)

64 32 64 32

Summing the six contributions, the last of which is negative, the total available power in form of air lift becomes:

^max ₌ ^ p^(») = - pNA 6.883212 · (45) using for speed the value

given by (26). Numerically, given p = 1.16 Kg/m³, D = 1.2 m and N = 4, for a wind speed of 10 m/s, would be equal to:

12.4680 kW (45b)

The result obtained for the aerodynamic lift mechanism perfectly matches the values of given by (21b) and (25b) for the direct thrust mechanism. This affirms an equivalence of the two torque production modes in the inner rotor space of the novel wind turbine of this disclosure, that makes even a rotor with a single straight and perfectly radial blade rotate smoothly. It should be remarked that, contrary to the assumption made for calculating the virtually convertible power in terms of pressure gradients, that is the absence of rotor blades in the inner space, the available power if , expressed by (25), calculated according to standard considerations of a thrust imparted to the blades by the impinging accelerated air streams, rests on the assumption that the rotor be composed of a number of blades equal to the number of flow sectors. Consequently, for a lower number of blades, one or more of the terms (22), (23) and (24) will be null and the total convertible power theoretically calculated for this mechanism of energy transfer would proportionately decrease as far as becoming null in absence of blades.

It may be demonstrated that for a number of blades greater than zero and lesser than the number of flow sectors through an annular module of the tubular honeycomb stator and assuming that the actual number of blades be spaced at the same angular distance from each other, any thrust contribution that is missed because of any "absent" blade (from the number equal to that of the flow sectors), is compensated by the augmented aerodynamic lift contribution on the blades actually present.

The effects that have just been illustrated for the windward or front side flow sectors of a honeycomb stator standing by itself in the wind, may be greatly enhanced by deploying a feathering wind collector of this disclosure. The action of the feathering collector, as schematically illustrated in Fig. 9b, is that of substantially duplicating a scheme of accelerated air injection through the leeward or rear flow sectors of the honeycomb stator, similar to that through the windward flow sectors.

Thus, the available power inside the rotor space is theoretically doubled and the generated vortex is reinforced in a mirror like manner also through the leeward flow sectors of the tubular honeycomb stator, producing a vortex of substantial circular symmetry in the rotor space.

The passive power attributable to a braking action of rotor blades traveling upwind is virtually canceled without the use of passive air diverters or of implements failing to ensure uniformity of effect over the whole circumference of the turbine rotor, which induces turbulences and disrupt or hold back from achieving a desirable circular symmetry of any air vortex, as it occurs in known WAVTs.

For the intended purely illustrative purpose of this detailed description of an exemplary embodiment twelve flow sectors were considered for the stator 1 and six identical and regularly spaced blades for the rotor though any of these numbers or both may be different, normally comprised between twelve and twenty four for the number of flow sectors of a module and one and twelve or even greater for the number of rotor blades (it has been experimentally verified that even a rotor with a single blade remains able to rotate smoothly because of the self-sustaining axially biased air vortex that self- generates and sustains itself in the rotor space by the combined actions of the tubular multi tiers honeycomb stator and of the feathering collector).

For the preceding analysis of the efficiency of the turbine in converting wind energy into mechanical energy to hold true at least in an economically significant measure with a real-world rotor, the air exiting a flow sector should ideally act on a blade with the same intensity for the whole angular distance traveled in sweeping the outlet flow area of the conduit 5. In other words, the relative inclination between the blade surface and the streamlines of the injected air should remain constant while the outer edge of the blade travels the full arc of circumference of an outlet to the next one, and also constant for the whole radial width of the blade (which may not necessarily reach as far as the surface of a central shaft of the rotor as will be explained later).

This double condition of constancy is hardly compatible with and achievable with the known VAWT architectures, generally characterized by a concave wind-taking profile.

Example of effective blade profile

Contrary to common VAWTs, where the blades receive the stream of accelerated wind air on their concave side, in the novel turbine of this disclosure, it is preferable that they receive the evenly distributed streams of accelerated wind air on their convex side. Therefore, contravening common practice, the blades preferably have a concave leading surface and a convex trailing surface. This because in the novel turbine of this disclosure where any up-wind travel (braking-phase) of the rotating blades is eliminated, the air injected in the rotor space has a swirling motion in spiraling down (like water down toward a drain hole) toward the open end of the inner space of cylindrical symmetry, and the rotor blades, besides being stricken by the air like in common VAWTs, are dragged along the swirling motion of the air. Of course, the rotor will rotate even if the blades were straight flat paddles or canonically disposed with a convex leading surface and a concave trailing surface, though with a sensibly reduced efficiency.

For better appreciating the above remarked peculiarity, consider decomposing the horizontal velocity component

of the injected air in a tangential v_L and a radial v_D component, as depicted in the geometrical construction on a cross sectional profile of a blade of Fig. 8.

Because of the chosen parameters for the analyzed embodiment, the two components have the same modulus, being the velocity of injection inclined by 45° from the radial direction: V_l = v_D = v^w cos (46)

The angular velocity at which the rotor will be forced to rotate by the tangential component is ώ =— , where r is the radius of rotation of the blade. In time t the blade r

rotates by an angle Θ = cot =— t . Simultaneously, along the radial axis, air travels a tract r

y = v_at = v I = r() . Therefore, the air that moves in the radial direction will hit the blade at its initial incidence point O(x=0, y=0) if the blade, after rotating by an angle Θ, intersects the radius at the point P(x=0, y=rff). This means that when the edge of the blade is at the point O, its generic point at ordinate y must be at an abscissa given by: x = - r - )tan0 . Thus the equation that describes the ideal blade profile is: x = -(r - y) tan— (47) r or, in parametric form: x = - τ(1 - θ) ίΆπθ y = rQ (48) with 0≤ Θ < 1

In view of the fact that in the turbine of this disclosure air acts prevalently on the part of the blades farthest from the axis of rotation (i.e. from a central shaft), and that the tangential speed of the air decreases in approaching the axis of rotation (the eye of the cyclone) at which it becomes practically null, not necessarily the blades should extend as far as the shaft ( Θ < 1 ), but may be fastened to it by several radially extending slender cantilever connectors in order to further reduce their weight beyond what may be accomplished by making them as thin and lightweight as possible though complying with strength and rigidity figures set by their mechanical design.

Preferably though not strictly necessary, the blades are not straight but extend in the axial direction helicoidally. In the embodiment considered, the longitudinal blade profile has an angle of inclination from a horizontal plane equal to 90°-φ = 70° 3 44" (circumference angle). As exemplified for a pair of opposite blades 7 and 7' in Fig. 7, each blade is a helix that winds for about 1/5 of a full turn around the axis of rotation for a total axial length of equivalent to the total height of the four stacked modules that compose the tubular honeycomb stator surrounding them, according to the architecture illustrated in Fig. 1. Generally, the blades may extend helicoidally for the whole height of the multi-tier honeycomb stator through a twist angle that may be comprised between 50° and 90°.

Pressure gradient

In the illustrated embodiment of Fig. 1, the inner cylindrical space or rotor space 2 internal to the tubular honeycomb stator 1, accommodating the rotor 6, is occluded at the top by a cap 3' that closes the central hole of the first truncated cone, annular diaphragm plate 3, and the out flow of air from the rotor space 2 takes place through the bottom. In fact, a function of the tubular honeycomb stator 1 is also that of confining the injected air, swirling in the inner rotor space, by virtue of the pressure gradient that is created between the outer air (at the intake interface of the flow sectors) and the air in the inner rotor space (at the injection interface of the flow sectors) of the tubular honeycomb because of the lesser speed of the incoming wind air compared to the tangential velocity of the air vortex within the inner rotor space.

Generally, in the cyclonic wind generator of this disclosure, differently from common VAWTs, the Betz's assumption of absence of sideway dispersion of the idealized stream-tube {Continuity Condition) is substantially met. Air that misses the impact with a blade does not escape but remains within the radius of action of the rotor blades, accompanying them in their rotation, while descending or raising toward the open end (of air discharge) of the rotor space, to the exterior with a spiraling motion, the axial speed of which, in the analyzed example, is given by the vertical (downward) component of the velocity of injection of the air into the rotor space 2 (re: equation 27): v^(/> = - _v = 0.651305 · ν

3 s

The presence of several helix blades that occlude the whole turn around the axis, leaving no "through sight" between the blades when looking at the rotor from an axial position, prevents that air may flow out without coming to act on any of the blades.

This contribution to useful power may be calculated by observing that the residual velocity of air inside the rotor space amounts to 65.13% of the velocity of air freely streaming below the outlet, which has a flow sectional area of nr¹ 3.733944 - D² (49)

The discharge flow creates a pressure gradient between the discharge zone and the air at the outer intake surface of the tubular honeycomb stator that accelerates the flow of air through the whole turbine structure and in particular its down flow in the rotor space, and also such an increase of kinetic energy is at least in part given to the rotor blades. The available pressure gradient power is obtained by applying equation (37) with

Numerically, given p = 1.16 Kg/m³, D = 1.2 m and N = 4, for a wind speed of 10 m/s, this power equals:

P_f = 0.4942 kW (50b) Such a pressure gradient power represents an additional contributive work on rotor blades potentially equivalent to more than 4% of the total available power, as separately calculated for a classical, direct air thrust on blades mechanism and for an aerodynamic lift mechanism on the blades. This attendant additional contribution to the convertible power compensates for the kinetic energy of discharged air not absorbed by the rotor and thence still having a residual swirl and axial velocity components, by exerting a vacuum effect that accelerates wind air collected by the wind turbine, and may theoretically allow to surpass the efficiency Betz's limit in a VAWT built according to this invention, and in the worst case significantly compensate non idealities such as turbulences, non-adiabatic kinetic energy transfer and frictional forces, making possible to achieve a real efficiency closer to said limit.

Scalability and ancillary aspects

If the length of the sides a regular polygonal surface of the exterior of the stator 1 is made equal to the height D of each annular module (i.e. of every flow conduit 5) of the tubular honeycomb stator structure (re: Figs. 1 and 2), such a design parameter may be used for defining most of the geometrical proportions and even the nominal power rating of the turbine.

The power that may theoretically be delivered by the Cyclonic Aeolian Generator (CEG) of the example described, in function of such a basic parameter D, air density p, and wind speed v_e , is given by P_tot = 9.45 · p£⁾²v' . Compared to a classical horizontal axis, three blades wind generators, at the same wind speed, the CEG delivers the same power with a surface exposed to the wind ( A_tot = 30.9 · D² ) equal to 79.6% of the rotor surface of the classical turbine, a ratio that in terms of production becomes even more favorable because the CEG is able to exploit weaker wind regimes as well as winds of intensity much higher than the technical safety limit of classical wind turbines.

Although, an even number of blades and/or of sides of the polygonal outer surface of the stator 1 may facilitate the job of designers, they may be in odd numbers, safeguarding though uniformity of distribution of torque and of air streams. Choosing to exemplarily create an anticlockwise vortex in the rotor space is out of obsequiousness to the renown Coriolis effect in our boreal hemisphere, although its role is really negligible among the other dynamical components.

Referring to the out of scale sketch of Fig. 1, the rotor shaft or a torque shaft 10 coaxially coupled to the end of the latter, extends down preferably inside a protective sleeve, reaching the interior of a power room or weather-proof cabinet 11 built (on solid foundations) in sight or underground for reducing visual impact of the installation, to be customarily held in a thrust bearing. The primary rotor shaft may be held in a bottom thrust bearing and in a top bearing, both rigidly connected to the stator structure 1 for ensuring, in any condition of stress of a typically tall structure, a constant and smallest clearance distance from the longitudinal edges of the rotor blades.

Materials of construction may in part depend from dimensions a thence from the nominal power rating of the CEG. Pillars and upright raisers, stiffeners, struts, beams, connection brackets and other elements of construction of the tall sustaining structure may generally be of steel. The tubular honeycomb stator 1, the cap 3', the rotor blades 7 may be made of lightweight materials like aluminum alloys, titanium, glass or carbon reinforced plastic, eventually of translucent aspect like a glass reinforced resin, PMMA and others. If deployed, the feathering collector 8, is the element that is particularly stressed by strong wind gusts and its structure and the elements of support and retention must be suitably designed to withstand them. Fiber reinforced plastic is preferred because of its unsurpassed resistance/weight ratio. For large size turbines, the feathering collector may even be structured in a composite manner: for example, a stress resistant flexible textile fabric (as used for making sails) is laid on and secured to a lightweight though suitably stiffened backing framework (for example by battens introduced in spaced parallel full-height pouches sewn in the fabric, the ends of which are respectively retained in channeled upper and bottom members of the rigid framework) such to make the fabric assume and keep a functional cardioid shape. The stiff lightweight framework may be made of fiber reinforced resin provided with or incorporating suspension wheels, at least at the extreme four corners of it and in correspondence of its central cusp, adapted to travel on bottom and upper circular guides. Circular capping flanges or undercuts ensure retention of the collector while the battened wind deflecting fabric offers a simple and effective stress relief element by making the side ends of the two wings of battened fabric secured at its middle to the cusp of the feathering wind collector, pulled by several tie ropes wound on multi-throats winches at the respective side ends of the rigid backing framework. Thus, the battened fabric wings may be fully extended and tensioned by turning the winches provided with a ratchet-wheel pawl mechanism that may be designed to snap-release tension whenever a maximum limit pressure acting on the collector fabric is surpassed (e.g. in the event of hurricane strength gusts). The wind pressure itself will then cause the two battened fabric wings to retract behind the leeward side of the honeycomb stator-rotor assembly of the turbine thus relieving the stress on the feathering collector structure. After the exceptional event, the two battened fabric wings may be re-extended and tensioned again by turning the respective winches. This option offers an effective and simple alternative to the deployment of alternative implements, for example a semi-cylindrical (or of other compliant cylindrical symmetry) guard element, normally held unobtrusively over the outer surface of the collector, adapted to be slidable around for completely hiding the stator into a cylindrical shroud of reduced coefficient of resistance, whichever be the point of origin of the expected gusts.

Of course, the machine illustrated in the drawings and analyzed in detail, could be alternatively designed to work in an upside down position such to generate an upward vortex rather than a downward vortex in the rotor space that would be closed at its bottom for an upward discharge of the air, eventually inverting the orientation of the baffles for retaining an anticlockwise rotation (Coriolis docet). In locations where a significant descending component in the prevalent winds is a rare condition, the upward discharge would further reduce noise and avoid any inconvenient on the ground.

The features of the embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the description.

Claims

1. A cyclonic Aeolian generator comprising:

a) a stationary tubular, honeycomb structure or stator (1) with cross- sectional inner circular perimeter and polygonal outer perimeter, axially divided in annular modules by truncated cone annular diaphragms (3) spaced at regular intervals starting from a first end diaphragm, delimiting an inner space (2) of cylindrical symmetry, occluded at the end corresponding to said first end diaphragm, each of said annular modules being divided by curving walls or baffles (4) in N curving flow sectors or conduits (5) of constant height and with a cross sectional flow area gradually decreasing toward said inner rotor space (2), all with a same radial slant;

b) a rotor (6) in said inner cylindrical rotor space (2) , having a number of blades (7) comprised between 1 and N.

2. The Aeolian generator of claim 1 , further comprising a wind collector (8), pivot-held or sustained in a feathering mode, free to rotate around said stator (1) for self-positioning itself over the leeward side of said honeycomb stator (1), and having an inward surface, a cross sectional profile of which has a central cusp (8') projecting inward as far as traveling around the honeycomb stator (1) at a clearance distance as small as possible.

3. The Aeolian generator of claim 1 , wherein a cross sectional profile of said curving walls or baffles (4) is an arc of a cycloid or parabola for at least part of its extension; the flow sectors (5) delimited by the baffles (4) injecting air streams into said inner rotor space (2) with a direction that, on a transversal plane, makes an angle with the radius comprised between 40° and 50°.

4. The Aeolian generator of claim 1 , wherein the conicity of said truncated cone annular diaphragms (3) determining said radial slant of the flow sectors (5) makes the air streams injected into said inner rotor space (2) to have a direction that, on a plane parallel to the rotor axis, makes an angle φ comprised between 16° and 24° with a projection of the axis on the plane.

5. The Aeolian generator of claim 1 , wherein said rotor (6) has blades (7), fastened to or projecting off a shaft (10) coaxial to the tubular honeycomb stator (1), having a convex trailing surface on which accelerated air injected in the rotor space (2) through said curving flow conduits or sectors (5) impinges, and helicoidally extending for the whole length of the rotor space (2) with a twist angle of the extreme edge of the blades around the shaft comprised between 50° and 90°.

6. The Aeolian generator of claim 1 , wherein said feathering wind collector (8) has a semi-circumferential base, the side ends of which reach diametrically opposite angular positions relative to the coaxial tubular honeycomb stator (1) and are spaced from it by a radial distance such to present intake areas (A_{l s} A₂) of collection of wind air alongside diametrically opposite flanks of the tubular honeycomb stator (1), the sum of which equals or exceeds the geometric projection area of the tubular honeycomb stator (1) on a plane orthogonal to the direction of provenience of the wind.

7. The Aeolian generator of claims 2 and 3, wherein the speed component

( ) of the injected air streams on the transversal plane makes an angle of 45°with the radius and the speed component (

) on a plane parallel to the rotor axis makes an angle φ of 19° 28' 16" with a projection of the axis on the plane, produced with a conicity of the truncated cone diaphragms (3) of 24° 24'.

8. The Aeolian generator of claim 6, wherein the ratio between the outlet flow area at the inward end of air injection into said inner rotor space (2) of each curved flow conduit or sector (5) and its intake area at the outward surface of the tubular honeycomb stator (1) is equal to 1 - (ΐ +π / 4) sin n; / 12) cos(p .

9. The Aeolian generator of claim 1 , wherein the number of curved flow conduits or sectors is comprised between 12 and 24, and the number of rotor blades is comprised between 6 and 18.

10. The Aeolian generator of claim 2, wherein said curving baffles (4) with cross sectional profile of a cycloid or a parabola arc that delimit laterally said curving flow conduits or sectors (5) have a rectilinear terminal tract towards their outlet into the inner space (2) containing the rotor (6).

11. The Aeolian generator of claim 1 , wherein said feathering wind collector (8) has a composite structure comprising a rigid shaping framework provided with or incorporating suspension and travel wheels or rollers (17) at upper and lower side corners and in correspondence of said central cusp (8') of the framework, along a semi- circumferential base member and semi- circumferential upper member of the framework, and a stress resistant textile fabric laid on and secured to said shaping framework.

12. A method of driving in rotation, in a rotor space of cylindrical symmetry, closed at one end and open at the other end, a curved blade radially projecting from a rotor shaft and extending along an axial tract of the shaft of an Aeolian generator, said curved blade having a concave side surface and a convex side surface, comprising the steps of:

a) generating an air vortex spiraling toward said open end of the rotor space by injecting into said rotor space multiple accelerated wind air streams regularly distributed around the whole circumference and along the axial extension of said rotor space, and all directed with either an inclination to the right or to the left of the radius on a cross sectional plane and with an inclination toward said open end on a plane parallel to the shaft axis;

b) arranging said curved blade with its convex side surface trailing in its motion impinged in succession by said injected air streams and said concave side surface leading in the direction of rotation.

13. The method of claim 11, wherein the angle of inclination in respect of the radius on a cross sectional plane is comprised between 40° and 50° and the angle of inclination on a plane parallel to the shaft axis is comprised between 16° and 24°.

14. The method of any of the claims 1 1 or 12, wherein said blade extends helicoidally for the whole length of said rotor space (2) with a twist angle of the extreme edge of the blade around the shaft axis comprised between 50° and 90°.