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DESCRIPTION

Technical field of the invention

This invention concerns an installation for electricity generation that exploits a unidirectional or bidirectional flow of a fluid, air in particular. This type of installation includes:

- a conduit through which the fluid (air) flows; - a turbine located inside the conduit, causing the rotation of electrical generators, after being activated by such fluid

Prior art

One example of the application of such type of in installation are the systems that exploit - by means of marine structures for absorption - the wave energy to generate alternating or variable airflows, which are then exploited to convert the mechanical (wave) energy into electricity.

The flows through such installations are generally bidirectional, in that they cyclically reverse the direction they flow through the turbine. For this reason, the installations are often equipped with Wells turbines, or similar turbines, which are able to keep the same rotation direction despite reversal of fluid current.

In any case, besides the possible bi- directionality, the fluid current flowing through such installations usually varies very irregularly in time.

Technically, well-known installations are equipped with the so-called variable blade angle turbines, which have systems that can rotate the blades around the respective radial axles, in order to vary the incidence angle of fluid current on the blade silhouettes, thereby enabling to adjust the turbine operation to the variations of external conditions, and above all, to the variation of the loads applied.

However, such well-known systems are effective if the working point is accurate and properly identified, and in steady feeding conditions.

Object and summary of the invention

This invention aims at overcoming the aforementioned setbacks.

In particular, this invention aims at creating an installation that is able to operate effectively even in such conditions in which the fluid current is not steady, and varies irregularly.

These aims are achieved by means of an installation with the features indicated in the claims below.

Claims are an integral part of the technical instructions concerning the invention that are provided in this document.

Short description of the drawings

Further features and advantages of the invention shall be highlighted in the description below, which refers to the drawings enclosed, provided by way of (non-restrictive) example:

figure 1 represents a schematic view in a partial cross section of the installation described herein; in the upper part of the figure the installation' s elements are depicted in a first operating condition, while in the lower part of the figure they are depicted in a second operating condition;

- figure 1A represents a view in cross section of a detail of figure 1;

- figures 2 and 3 represent perspective schematic views, with partial cross sections, of the installation in figure 1, in two different operating conditions respectively;

- figures 4 and 5 represent a cross section view of the installation in figure 1 according to the A-A line, in the two different operating conditions of figures 2 and 3;

figures 6 and 7 represent two cross section views, similar to the views of figures 2 and 3, but with an alternative implementation of the installation described herein;

- figure 8 shows schematically the operation of the splitter of the installation described herein;

- figure 9 represents a chart of the normalized operating efficiency of the installation described herein, according to the discharge coefficient and to the rotational speed of the turbine rotor;

- figure 10 represents schematically an example of the control circuit of the installation described herein .

Detailed description of the invention

The following description features several details related to the evolution, supplied to clarify the functions of the invention devices. Such functions can be executed by using one or more devices described herein, or with other methods, components or materials, etc. In other cases, well-known material structures or operations are not shown or described in detail, to draw the attention on the various aspects of implementation .

References used herein are only for convenience purposes, therefore they do not define the protective scope of the extent of the various forms of implementation .

As we said at the beginning, the function of the installation described herein is to generate electricity from a unidirectional or bidirectional flow of a fluid, air in particular, flowing through a conduit .

In general, with reference to figures from 1 to 8, the installation described herein includes a conduit 2, through which the unidirectional or bidirectional flow of the fluid flows, and a turbine located inside the conduit 2, whose rotor 4 is configured to rotate as a consequence of the action of the fluid on it.

In case of applications with bidirectional flow, the turbine can have a rotor that maintains the same rotation direction, despite the reversal of the direction of the fluid. This type is well known as for technical aspects; in this case, for instance, the turbine can be a Wells-type turbine.

Turbine 4 is connected to an electrical generator 3 that converts the turbine kinetic energy into electricity .

Note that figures from 1 to 8 are schematic figures;

their aim is to clarify the key features of the installation descried herein, and they do not illustrate the various details of the installation, which can be created according to the common know-how of the technical sector concerned. In addition, the installation can also have a multi-stage turbine that is equipped, for instance, with multiple rotors and/or statoric impellers for the pre-rotation of fluid current, and/or a system of interfaces with the atmosphere.

As previously shown, this type of installation may be implemented in systems that exploit the wave energy of the sea to generate forced air flows that are used as working fluid for electricity generation. Note that the installation described herein may also be used in any other system requiring the conversion of the mechanical energy of a fluid into electricity. Therefore, the example of application indicated herein is not to be considered in a restrictive way, as for the installation described herein.

The installation described includes at least one splitter or an inertia regulating device, of the types described below.

In general, the splitter is configured to vary the flow section of the fluid through the turbine. The inertia regulating device, instead, is configured to vary the inertia of the turbine group; by "turbine group" we mean the set of elements that co-rotate with the turbine rotor.

As we will explain below, such devices enable to control the operation mode of the installation according to the changes in the operating conditions.

The installation described herein preferably includes both devices, yet even the use of only one of these is always beneficial, as you will see below.

The splitter

The splitter' s function is to change the flow cross section of the fluid through the turbine 4. This device is able to work on both unidirectional and bidirectional fluid currents.

In various forms of implementation, as well as in those illustrated, the device includes a first and a second splitter group, located at the opposite sides of the turbine. Both groups include a deflector 14 configured to determine - along with the internal wall of the conduit 2 - a ring-shaped flow cross section in the turbine, indicated in figures with the "S" reference. In particular, the deflector 14 includes a central portion 14A, coaxial to the rotation axle of rotor 4, as well as surface 14B mounted on the central, mobile portion between two ends, so as to vary the "S" cross section width between a maximum value (see figure 4) and a minimum value (see figure 5) . In particular, surface 14B takes on - in its first end - a cylindrical shape (see figures 2 and 6), which corresponds to a maximum width value of the "S" cross section, and in the second end, a truncated conical shape corresponding to a minimum width value (see figures 3 and 7) .

Surface 14B may be made of hard or flexible material, or a combination of hard and flexible materials. To this respect, figures 1-3 and figures 6-7 show, respectively, two options to make surface 14B.

In various forms of implementation, including the one shown in figures 1-3, this surface is composed of a set of segments 16 arranged around the central portion 14A and hinged to it, and a set of membranes 18 that link the respective internal sides of the pairs of adjacent segments. Segments 16 may oscillate between a closed configuration (shown in figure 2 and in the upper part of figure 1), in which they define the cylindrical shape indicated above, and a maximum opening configuration (shown in figure 3 and in the lower part of figure 1), in which they define - along with the membranes 18 - the aforementioned truncated conical shape. Membranes 18 are made of a flexible and elastic material, and their sizes vary when they are operating, following the motion of segments and covering the space that results from the estrangement of the latter.

The system that activates mobile segments 16 (not shown in figures) preferably envisages a lever mechanism activated by a rotary or linear actuator T, shown schematically in figure 8. In any case, the system concerned may also envisage other types of means . In various alternative forms of implementation, such as the one shown in figures 6 and 7, surface 14B is defined by a single flexible and elastic membrane, mounted on a mobile frame (not visible) that moves it between the two conditions shown in figures 6 and 7, in a similar way to the one described with reference to figures 2 and 3.

Note that the device concerned may envisage one splitter group in the implementations in which the flow is only unidirectional.

The splitter described above allows the axial velocity of the fluid to be regulated in the turbine, due to the variation of the ring-shaped "S" section obtained by regulating the position of surface 14B of the two splitter groups. The latter operate synchronously to define - at the opposite sides of the turbine - flow "S" cross sections with the same width.

Figure 8 shows schematically an example of how such device operates. The left-hand side figure shows the installation in a condition in which the axial velocity of the fluid is optimal for the operation of the installation (V=Vott) . In this case, surface 14B is in its closed configuration of figures 2 and 6, and identifies the maximum width of section SI. In the right-hand figure, the installation is in a condition in which the axial velocity of the fluid is lower than the optimal velocity (V < Vott) . In this case, surface 14B is regulated in an open position, so that the flow of air is narrowed up to the ring-shaped S2 section, whose sizes determine a fluid velocity equal to the optimal (V" = Vott. ) .

Clearly, the device concerned may be operated to determine any variation of axial velocity of the fluid, according to the various operation requirements.

The inertia regulating device As previously mentioned, the inertia regulating device varies the moment of inertia of the turbine group .

With reference to figure 1, the device concerned includes one or more eccentric masses 22, connected in rotation to the rotor shaft by means of a connection mechanism 24 that enables to vary the radial distance of such masses from the rotation axle of the rotor.

This device also includes an organ 26 for the activation of such mechanism; it acts on such mechanism by interposing bearings 28 that disconnect the organ 26 from the rotation of the masses 22. The organ 26 is therefore able to vary - by means of mechanism 24 - the radial distance of masses 22 independently from their rotational speed, and therefore, independently from the rotational speed of the turbine rotor.

The distance variation of masses 22 from the rotation axle of the rotor clearly changes the value of the overall inertia moment of the turbine group.

Therefore, the device concerned - by simply modifying the moment of inertia of the turbine group by activating the organ 26 - may play a role in the installation operation, to vary the rotational speed of the rotor, or, instead, to prevent any variation of the velocity when the external operating conditions change (for instance, a variation of loads applied to the turbine group) .

In various forms of preferred implementation, the mechanism 24 includes a first and a second lever 24A, 24B, that are joined together. The first lever 24A is also joined with a pivot 24A' carried by the turbine rotor, whereas the second lever is joined with a pivot 24B' carried by a mobile element 26A of the organ 26 through the interposition of bearings 28. The organ 26 is preferably a linear actuator, for example a cylindrical actuator or a nut and lever actuator, whose mobile element 26A is controlled in a translation movement along a rectilinear direction, in the example shown, that is parallel to the rotation axle of the rotor. As you can see in figure 1, the activation of element 26A by the actuator 26 results in a translation of pivot 24B' , which in turns varies the joint angle of the two levers 24A and 24B, thereby causing a shift of mass 22, either approaching (see figure 1 in the upper part of the figure) or distancing itself (see figure 1, in the lower part of the figure) from the rotation axle of the rotor. In various forms of implementation, that are preferable, as well as in the one shown, mass 22 is arranged on the edge of the second lever 24B and the joint pivot of the two levers corresponds to half the length of the second lever.

Installation operation

The devices described above allow the operating mode of the installation to be controlled, in order to maintain high efficiency when operating conditions change .

In this respect, figure 9 shows a chart that represents the trend of maximum efficiency that the installation can achieve (normalized so that in the chart the maximum efficiency takes a value of 1) according to the parameter called "discharge coefficient φ", which is defined by the ratio between the axial velocity of the fluid and the velocity of the blade being hit by the fluid.

The chart highlights that an efficient energy conversion occurs for discharge coefficients between 0.07 and 0.2; in such operating condition the machine efficiency is close to the maximum achievable, for each fluid velocity/blade reached. On the other hand, the machine efficiency decreases for coefficient φ values lower than 0.07, namely conditions in which the fluid velocity is too low as compared to the blade velocity, as well as for coefficient values greater than 0.2, namely conditions in which fluid velocity is too high as compared to the blade velocity.

As discussed above, in the typical implementations of the installation described herein, the flow through conduit 2 varies very irregularly in time. Similarly, during the operation, the loads applied to the turbine group can also vary. Both circumstances lead the aforesaid coefficient φ to distance itself from the value interval corresponding to an efficient operation of the installation, thereby worsening its efficiency.

To contrast such problem, the installation described herein is to activate the splitter and the inertia regulating device described above to vary the axial velocity of the fluid and the moment of inertia of the turbine group, respectively, in order to maintain the coefficient on values that correspond to optimal

operation efficiency (e.g. within the interval of

values indicated above with reference to the example of

figure 9 ) .

To this aim, with reference to figure 10, the installation described herein includes a set of sensors 101, 102, 103, aimed at detecting the operating conditions of the installation (e.g. upstream and downstream the turbine, axial velocity of the fluid, rotational speed of the rotor, etc.), and a control unit 100 (shown schematically in figure 1) . The latter controls and coordinates the two devices (as shown in the figure, the actuator T of the splitter and the actuating organ 26 of the inertia regulating device) according to the conditions detected, so as to maintain the coefficient φ on pre-set values. In particular, for instance in case of an excessive reduction of the coefficient φ, the control unit can act on the actuator T in order to increase - through surface 14B - the axial velocity of the fluid, and/or to activate the organ 26 in order to increase the moment of inertia of the turbine group and therefore reduce the rotational speed of the rotor. In case of an excessive increase of coefficient φ, the control unit may activate the actuator T in order to reduce - through surface 14B - the axial velocity of the fluid and/or to activate the organ 26 so as to decrease the moment of inertia of the turbine group, thereby increasing the rotational speed of the rotor. Evidently, the use of only one of the two devices described herein enables to effectively control the operation of the installation.

Obviously, without prejudice to the principle of this invention, the details for the construction and the forms of implementation may vary, even remarkably, compared to what has been explained here, by way of (non-restrictive) example. This change shall not move away from the scope of the invention, as specified in the claims enclosed.