GB2141183A - Aeolian motor - Google Patents

Abstract

The aeolian motor comprises a rotor having blades 5 adapted to rotate about an axis 2 substantially parallel to the direction of the windflow and bound externally by a tubular element 7a and internally by a tapered element 8 adapted to duct the inflowing air towards the blades 5. Spokes may be provided between the blades and hub 3. Element 8 may be a stationary member not rotating with the rotor. <IMAGE>

Description

SPECIFICATION Aeolin motor particularly for use with low speed winds This invention relates to an Aeolian motor particularly conceived to utilize low speed winds as well as irregular winds.

As is known, the goal of deriving rotary energy from the wind has been pursued possibly for thousands of years, and many systems have been devised through the epochs to achieve that goal; very well known are, for instance, windmills.

More modern Aeolian or wind motors, created to fight the energy crisis determined by the currently high cost of oil, are fairly sophisticated machines based on,extensive studies of aerodynamics and employing propellers or rotating wings generally defining one or more sets of blades. Among these Aeolian motors, the most widely used ones are those having a set of blades arranged for rotation about a substantially horizontal and parallel axis to the windflow direction, for the positioning of said blades there being provided either appendages or extensions or tail planes which, in a vane-like fashion, constantly hold the blades to face in the direction of the windflow.Many devices are also available for exploiting the energy supplied by the Aeolian motor blades, although such devices will not be discussed hereinafter because foreign to the scope of this invention.

A common feature with all the current technical solutions for the utilization of wind energy is the following: the airflow impinges directly on the blades without undergoing any prior treatments and, when a higher power output is required, the only method used is that of increasing the blade area exposed to the wind.

Such prior technical solutions, which are satisfactory in the increase of fairly strong and constant winds, become inadequate in areas of prevailing light winds, and generally in the case of light and moderate winds. In fact, in such cases as these, currently available Aeolian motors cannot start to rotate because the low wind speed is in practice unable to overcome the rotational inertia of the motors themselves.

Another disadvantage of conventional Aeolian motors, with low speed wind conditions, is the following.

It is known that propeller blades require to be set at an angle, in proportion with the wind speed and peripheral or rotational speeds of the blades. Where the blade aspect ratio is high, the blades are twisted proportionally with the distance from the rotation axis. In practice, the twist is dictated, for each cross-section of the helix or blade by the direction of the apparent wind speed as obtained by composing the true wind speed with the peripheral speed of the blade section being considered.

It will be apparent from Fig. 1 of the accompanying drawings that the lower is the true wind speed B, the larger becomes the angle a between said true speed B and apparent speed A, with a consequent increase of the inclination of the helix or blade with respect to the direction of the rotation axis.

As a consequence of said inclination, the aerodynamic force F, which is substantially perpendicular to the blade in question, develops a small component F' in the direction of rotation of the propeller, with resulting poor utilization of the wind action. Moreover, with said inclination also grows the aerodynamic drag force R, since the component R' of the latter increases which opposes the component F' of the force F. Nor should it be neglected that the bending force applied to the blades also increases.

In actual practice, the above-cited phenomena make Aeolian motors virtually useless in the case of low speed winds. If the wind low speeds are accompanied, as is often the case, by substantial irregularity of the winds themselves, it follows that Aeolian motor cannot ensure even the slightest smoothness of operation, the rotational momentum gained with low speed winds being entirely inadequate to overcome such irregularities.

In view of the above situation, and of the considerable importance of the utilization of Aeolian energy from the power generation standpoint, it is a primary object of this invention to solve the technical problem of providing an Aeolian or wind motor which is capable of successfully utilize even low speed winds.

Another object of this invention is to provide an Aeolian motor as indicated, which is simple construction-wise and compact in size, that is capable of solving the above technical problem without involving specially sophisticated technological approaches or the provision of particularly large blades or propellers.

A further object of the invention is to provide peculiar embodiments of said Aeolian motor which are advantageous per se and represent a technical step forward.

According to one aspect of the invention, these and other objects, such as will be apparent hereinafter, are achieved by an Aeolian motor, particularly conceived to utilize low speed winds, of the type which comprises a rotor having a plurality of blades adapted to rotate about a substantially parallel axis to the direction of the windflow, characterized in that said blades are shaped and arranged to form an annular ring of blades bound externally by a tubular element and internally by a tapered element effective to duct the air impinging thereof toward said annular ring of blades.

The tapered element may either be rigid with the blades and jointly rotate therewith, or it may be stationary. In this latter case separate supporting means are provided for the tapered element. The same applies also to the tubular element.

Further features and advantages of the invention will be appparent from the following description of some preferred but not limitative embodiments thereof, as illustrated by way of example in the accompanying drawings, where: Figure 1 illustrates schematically the forces which are active on a blade section of an Aeolian motor; Figures 2 and 3 are respectively a lateral section and front view of a first embodiment of a rotor according to this invention; and Figure 4 is a lateral section of a second embodiment of the inventive rotor for an Aeolian motor.

Making reference to the drawing figures, and in particular to Figs. 2, 3, and 4, a rotor 1 is shown being mounted on a shaft 2 by means of a hub 3 having a flange 3a. Between the shaft 2 and hub 3, bearings 4 are provided. In all cases, the construction of the hub 3 may be any desired one, as may the construction of the shaft 2 and members connected thereto, not shown.

The rotor 1 of this invention includes, in both its embodiments shown, a plurality of blades 5 arranged to have a limited radial extension and form an annular ring of blades 6 (Fig. 3) which is closed and bound both externally and internally.

In fact, the blade ring set 6 is bound externally by a tubular element 7 preferably made rigid with the blades 5, and internally by a tapered element or nose 8 having its tip arranged to meet the oncoming flow of air.

Advantageously, the tapered element or nose 8 is also rigid with the blades 5. Otherwise supporting means may be provided for the nose 8, which is thereby made stationary as a modification.

In the embodiment shown in Figs. 2 and 3, the tubular element 7 is simply cylindrical, and the connection between the blades 5 and hub 3 is implemented with the aid of simple spokes 9 attached, at one end, to the hub 3 and, at the other end, to the final cylindrical portion of the tapered element or nose 8.

In the embodiment shown in Fig. 4, said tubular element is indicated at 7a, and has a flared configuration substantially converging toward the tapered element or nose 8. Moreover, the latter is attached directly to the hub 3 which is designed to have a substantial length.

Finally, and preferably, the blades 5 of the rotor 1 are non-twisted, as shown in Fig. 3.

The operation of the inventive Aeolian motor, and in particular of the rotor 1, will be quite apparent from the above description of its construction.

As shown best in Figs. 2 and 4, the tapered element or nose 8 defines, in combination with the tubular element 7, a converging duct, wherethrough, as is known, the flow of air will be spontaneously accelerated, to compensate for the reduced passage section with respect to the larger inlet section. This speed increase compensates for and obviates the losses due to the narrow passage section, because, as is known, the power to be derived in theory from an airflow is proportional to the cube of the speed of the airflow.

As a result, even in the presence of load losses due to deflection of the airflow, an airflow at a comparatively high speed is achieved past the blades 5, even with light or moderate winds.

The comparatively high speed attained by forming said annular duct convergent, is also useful for another reason: with reference to the diagram of Fig. 1, the increased wind speed leads to the formation of relatively small angles a, with attendant straightening of the blades 5 and increase of the component F' of the aerodynamic force F, as well as reduction of the component R' of the aerodynamic drag R.

The construction, virtually in a single piece, of the tubular element 7 or 7a, blade ring set 6, and tapered element or nose 8, minimizes the irregularities of the airflow and enables a very simple construction of the rotor 1.

Thus, the invention achieves its objects, as well as several important advantages. Among these, and additionally to the ones mentioned hereinabove, the increased wind speed past the blades 5 and improved efficiency of the blades as regards the ratio of the utilized aerodynamic force F' to the aerodynamic drag R', the following are worth mentioning.

Thank to the reduced size of the blades, which are arranged at the narrowest zone of the convergent annular duct, the differentials between the peripheral speeds of the two blade ends are minimized, and consequently the blade' twist can be eliminated. Moreover, by enclosing the blades between concentrical rings, tip vortices are eliminated which would as a rule deduct from the efficiency of the blades.

Furthermore, the rotor has a high flywheel stability, both on account of the blades having been moved to the periphery thereof, thus concentrating the masses where speed is at a maximum, and because said tubular element will add its own mass to that of the blade set.

Nor the fact should be ignored that the tubular element or outer ring, being entirely projection-free can protect the blades against impact and reduce their potential hazard.

Lastly, the simplicity of the construction is to be pointed out, which has of preference the blades and their surrounding elements constructed as a single piece.

The rotor according to this invention makes it possible to utilize relatively low speed and even irregular winds; even light winds can produce an optimal action owing to their relatively higher speed past the blades, while the flywheel stability provided will readily take up the irregularities in the wind action.

The invention so conceived is susceptible to many modifications and variations without departing from the scope of the instant inventive concept.

Moreover, all of the details may be replaced with technically equivalent elements.

In practicing the invention, the materials used, as well as the dimensions, may be any selected ones to meet individual requirements.

Claims (9)

1. An Aeolian motor particularly conceived to utilize low speed winds, of the. type which comprises a rotor having a plurality of blades adapted to rotate about a substantially parallel axis to the direction of the windflow, characterized in that said blades are shaped and arranged to form an annular ring of blades bound externally by a tubular element and internally by a tapered element effective to duct the air impinging thereon toward said annular ring of blades.

2. An Aeolian motor according to Claim 1, characterized in that said tubular element, said annular ring of blades, and said tapered element are made rigid to one another and jointly rotatable about said substantially parallel axis to the direction of the windflow.

3. An Aeolian motor according to Claim 1, characterized in that said tubular element is cylindrical.

4. An Aeolian motor according to Claim 1, characterized in that said tubular element is made substantially convergent toward said tapered element.

5. An Aeolian motor according to Claim 1, characterized in that said blades are connected by means of spokes to a coaxial hub with said shaft, bearings being provided between said hub and said shaft.

6. An Aeolian motor according to Claim 2, characterized in that said rotor is supported on said shaft through a hub enclosing said shaft and extending to rigidly engage with said tapered element.

7. A motor according to Claim 1, wherein said tapered element is supported stationary.

8. A motor according to Claim 1, wherein said tubular element is supported stationary.

9. A motor according to the preceding claims, substantially as herein described and illustrated with reference to the accompanying drawings.