Device for accelerating a fluid current

Abstract

Device for accelerating a fluid current, comprising : an enclosure having axial symmetry around a central axis oriented along a reference direction, which defines therein a first cavity and comprises, in order along the central axis an inlet portion having a central opening open outwardly in a direction opposite to the reference direction, a first divergent portion having a plurality of first side openings open outwardly, a first convergent portion, and a first confluence portion having a plurality of first confluence openings open radially outwardly and an outlet opening open outwardly in the direction of the reference direction; an inner body having axial symmetry around the central axis and housed within the first cavity, which comprises, in order along the central axi s a second divergent portion positioned at least partially within the first divergent portion, a second convergent portion positioned at least partially within the first convergent portion, and a second confluence portion, which is hollow and is positioned at least partially within the first confluence portion, which defines therein a second cavity, and which has a plurality of second confluence openings radially open towards the first cavity, wherein the inner body has a plurality of inner channels extending between respective second side openings formed in the second divergent portion and the second cavity, wherein an annular gap is defined that narrows proceeding along the reference direction within the first cavity, between the enclosure and the inner body; a plurality of sleeves, wherein each sleeve extends through a corresponding first side opening and has a first end arranged outside the enclosure and oriented at least partially opposite to the reference direction, and a second end facing a corresponding second side opening.

Description

[0001] DEVICE FOR ACCELERATING A FLUID CURRENT

[0002] The present invention relates to a device for accelerating a fluid current, and in particular a wind current, in order to subsequently exploit it for the production of electrical energy.

[0003] In the field of wind energy exploitation, it is well known that the power extractable by means of a wind turbine strongly depends on the speed of the wind current in which the turbine is immersed. More specifically, it is known that the extractable power P by means of a turbine immersed in a fluid current, having a density p and a speed v, can be calculated using Betz' s law, based on the area A swept by the turbine blades and on a performance coefficient ?, as follows:

[0004] P = -1flpAv3

[0005] Therefore, it becomes apparent that, for example, by doubling the speed v of the fluid current moving the turbine blades, under otherwise equal conditions, an extractable power P that is eight times greater is obtained. For this reason, wind turbines are usually installed in geographical areas where wind speed is particularly high, in particular for example in mountainous areas or offshore; however, such location makes the installation and maintenance of the turbines themselves complex and costly. Furthermore, the above- mentioned geographical areas are usually characterized by inconsistent, although intense, winds, and this inevitably limits the total amount of extractable energy over a reference period of time.

[0006] Currently, it is instead economically disadvantageous to exploit wind energy in areas characterized by wind currents which, although constant, have a relatively low speed, since the extractable power is too limited.

[0007] An object of the present invention is to overcome the above-mentioned drawbacks, and in particular to allow the exploitation of wind energy even in geographical areas characterized by wind currents having limited speed .

[0008] A further object of the present invention is to allow the exploitation of wind energy by wind turbines with limited footprint, that are quiet, cost-effective, and easy to install and maintain.

[0009] These and other results are achieved according to the present invention by making a device according to claim 1.

[0010] Further features of the invention are the subject of the dependent claims.

[0011] The present invention will now be described, by way of illustration but not limitation, according to its preferred embodiments, with reference to the figures of the attached drawings, in which:

[0012] - Figure 1 is a perspective view of a device according to the invention;

[0013] - Figure 2 is a front view of Figure 1;

[0014] - Figure 3 is a perspective view of a section of Figure 2 taken along line III-III;

[0015] - Figure 4 is a sectional view of the device according to the invention in an alternative embodiment;

[0016] - Figure 5 is an enlarged view of the detail of Figure 4 within circle V.

[0017] With reference to Figure 1, number 1 indicates, as a whole, a device configured to accelerate a fluid current, and in particular a wind current.

[0018] The device 1 comprises first of all an outer enclosure 2, which has axial symmetry around a central axis A oriented along a reference direction X. The enclosure 2 defines therein a first cavity 20 (visible in Figure 3) , and comprises in order along the reference direction X an inlet portion 21, a first divergent portion 22 (i.e. , such that the respective cross-section increases proceeding along the reference direction X) , a first convergent portion 23 (i.e. , such that the respective cross-section narrows proceeding along the reference direction X) , and a first confluence portion 24.

[0019] The inlet portion 21 has a central opening 25 open outwardly in a direction opposite to the reference direction X, such that a fluid current moving along the reference direction X can enter the first cavity 20 through the central opening 25. The first divergent portion 22 has a plurality of first side openings 26 open outwardly. The first confluence portion 24 has a plurality of first confluence openings 27 open radially outwardly, and an outlet opening 28 open outwardly in the direction of the reference direction X.

[0020] In an alternative embodiment, visible in Figures 4 and 5, the first confluence portion 24 is composed of a plurality of wing profiles 270 separated from each other; in such case, each first confluence opening 27 is defined between two adjacent wing profiles 270. It has indeed been observed that such solution allows to further increase the speed of the primary flow 7, which will be described below.

[0021] With reference to Figure 3, the device 1 further comprises an inner body 3, which is housed within the first cavity 20 and also has axial symmetry around the central axis A. The inner body 3 comprises in order along the reference direction X a second divergent portion 30, a second convergent portion 31, and a second confluence portion 32, which is hollow.

[0022] The inner body 3 is positioned within the first cavity 20 such that the second divergent portion 30 is positioned at least partially within the first divergent portion 22, that the second convergent portion 31 is positioned at least partially inside the first convergent portion 23, and that the second confluence portion 32 is positioned at least partially inside the first confluence portion 24. In this way, in the first cavity 20 between the inner surface of the enclosure 2 and the outer surface of the inner body 3, and more specifically between the first divergent portion 22 and the second divergent portion 30 and between the first convergent portion 23 and the second convergent portion 31, an annular gap 4 is defined, that narrows proceeding along the reference direction X.

[0023] The second confluence portion 32 defines therein a second cavity 33 and has a plurality of second confluence openings 34 which open radially towards the first cavity 20, more specifically towards the portion of the first cavity 20 defined within the first confluence portion 24. The inner body 3 further comprises a plurality of inner channels 35 which extend through the second divergent portion 30 and the second convergent portion 31 between respective second side openings 36 formed on the surface of the second divergent portion 30 and the second cavity 33: in this way, the second cavity 33 is f luid-dynamically connected to the first cavity 20 both through the inner channels 35 and through the second confluence openings 34.

[0024] In an alternative embodiment, visible in Figure 4, the inner body 3 does not comprise a second confluence portion, and the inner channels 35 end in respective rear openings that open directly towards the first cavity 20 at the first confluence portion 24. Even in such embodiment, therefore, a fluid-dynamic connection is formed between the terminal part of the inner channels 35 and the first cavity 20 at the first confluence portion 24.

[0025] The device 1 further comprises a plurality of sleeves 5 (or short tubes) . Each sleeve 5 extends through a corresponding first side opening 26 (i.e. , through the enclosure 2 at the first divergent portion 22) , and comprises a first end 50 and a second end 51, both open and opposite to each other. In particular, the first end 50 is arranged outside the enclosure 2 and is oriented at least partially opposite to the reference direction X, while the second end 51 faces a corresponding second side opening 36 of the inner body 3. In this way, a fluid current moving along the reference direction X can enter the sleeves 5 through the respective first ends 50 and enter the inner channels 35 through the second ends 51. Due to such configuration, by arranging the device 1 such that the central axis A is oriented substantially in the direction of movement of the fluid current to be accelerated, the following are generated:

[0026] - a primary flow 7 entering the first cavity 20 through the central opening 25, being accelerated along the gap 4, and arriving in the first confluence portion 24; and

[0027] - a plurality of secondary flows 8 entering the sleeves 5 through the respective first ends 50, proceeding along the inner channels 35, and exiting from the rear openings, thereby arriving in the second cavity 33 of the second confluence portion 32, if present.

[0028] The accelerated primary flow 7 that arrives within the first confluence portion 24 is characterized by low pressure (due to high speed) , and therefore draws both the secondary flows 8 exiting from the rear openings and the fluid being outside the enclosure 2, through the first confluence openings 27, since both are characterized by a higher pressure. It has been observed that this causes further acceleration and an increase in the flow rate of the fluid contained in the first confluence portion 24. From the outlet opening 28, a single flow exits, in which the primary flow 7, the secondary flows 8, and the outer fluid drawn through the first confluence openings 27 have merged; such single flow is particularly accelerated, i.e. , characterized by a speed significantly higher than that of the initial fluid current.

[0029] It has further been observed that the sleeves 5 allow to obtain highly laminar and minimally turbulent secondary flows 8: this allows to fully exploit the kinetic energy of the secondary flows 8 and to obtain a more intense acceleration of the fluid contained in the first confluence portion 24.

[0030] The single flow exiting from the outlet opening 28 can therefore be exploited for the production of electrical energy, for example by using a wind turbine in the case where the fluid current is a wind current. Since the exiting flow is significantly accelerated compared to the initial fluid current, the device 1 allows fluid currents characterized by low speed to be also exploited to extract energy, and thus particularly to position wind turbines even in geographical areas characterized by wind currents of limited intensity, if properly coupled with corresponding devices 1 according to the invention .

[0031] Furthermore, given the capability of accelerating the fluid current, it is possible to use wind turbines that are compact, and therefore quieter, more cost-effective, and easier to install and maintain, while still achieving economically advantageous exploitation of wind energy. Preferably, each sleeve 5 has a countersink at the first end 50: the first end 50 thus has an inner cross-section that narrows as it proceeds towards the second end 51. It has indeed been observed that such feature allows the generation of even more laminar secondary flows 8. Furthermore, each sleeve 5 can have an inner crosssection that narrows as it proceeds from the first end 50 towards the second end 51 over the entire length of the sleeve 5 itself: such feature also allows to obtain particularly laminar secondary flows 8.

[0032] Preferably, the first side openings 26 are formed on the first divergent portion 22 such that they are arranged equally spaced from each other along a first circumference centred on the central axis A, and the second side openings 36 are formed on the second divergent portion 30 in the same number as the first side openings 26 and are arranged equidistant from each other on a second circumference centred on the axis A. It has indeed been observed that such configuration ensures that the secondary flows 8 do not create turbulence among themselves, not even when exiting through the rear openings. Further preferably, there are four first side openings 26 and four second side openings 36, between which four sleeves 5 extend. It has indeed been observed that such solution particularly minimizes turbulence .

[0033] Preferably, the inner surface of the enclosure 2 defined by the first divergent portion 22 and the first convergent portion 23, and the outer surface of the inner body 3 defined by the second divergent portion 30 and the second convergent portion 31, are curved. It has indeed been observed that such shape allows to obtain a particularly laminar and minimally turbulent primary flow 7, which in turn also allows to fully exploit the kinetic energy of the primary flow 7 itself.

[0034] With reference to Figure 2, the device 1 can further comprise introduction means 6 actuatable to facilitate the inlet of the primary flow 7 into the first cavity 20 through the central opening 25. Indeed, it has been observed that it can be advantageous, for a limited initial period of time, to force the inlet of the fluid current into the first cavity 20, until the device 1 is capable of autonomously drawing the fluid current and generating the primary flow 7. The introduction means 6 can consist, for example, of a fan 6 positioned in the inlet portion 21 or in the first divergent portion 22.

[0035] The present invention has been described, by way of illustration, but not of limitation, according to its preferred embodiments, but it is understood that variations and / or modifications can be made by a person skilled in the art, without thereby departing from the related scope of protection as defined in the attached claims .

Claims

CLAIMS1) Device (1) for accelerating a fluid current, comprising :- an enclosure (2) having axial symmetry around a central axis (A) oriented along a reference direction (X) , which defines therein a first cavity (20) and comprises in order along the central axis (A) an inlet portion (21) having a central opening (25) open outwardly in a direction opposite to the reference direction (X) , a first divergent portion (22) having a plurality of first side openings (26) open outwardly, a first convergent portion (23) and a first confluence portion (24) having a plurality of first confluence openings (27) open radially outwardly and an outlet opening (28) open outwardly in the direction of the reference direction (X) ;- an inner body (3) having axial symmetry around the central axis (A) and housed within the first cavity (20) , which comprises in order along the central axis (A) a second divergent portion (30) positioned at least partially within the first divergent portion (22) , and a second convergent portion (31) positioned at least partially within the first convergent portion (23) , wherein the inner body (3) has a plurality of inner channels (35) extending between respective second side openings (36) formed in the second divergent portion (22) and respective rear openings f luid-dynamically connected to the first cavity (20) at the first confluence portion (24) , wherein in the first cavity (20) between the enclosure (2) and the inner body (3) an annular gap (4) is defined which narrows when proceeding along the reference direction (X) ;- a plurality of sleeves (5) , wherein each sleeve (5) extends through a corresponding first side opening (26) and has a first end (50) arranged outside the enclosure (2) and oriented at least partially opposite to the reference direction (X) and a second end (51) facing a corresponding second side opening (36) .2) Device (1) according to claim 1, wherein the first end (50) of each sleeve (5) has a countersink that converges when proceeding towards the corresponding second end (51) .3) Device (1) according to claim 2, wherein each sleeve (5) has an inner section that narrows as it proceeds from the first end (50) towards the second end (51) .4) Device (1) according to any one of the preceding claims, wherein the first side openings (26) are formed on the first divergent portion (22) so as to be equidistant from each other and arranged on a first circumference centred on the central axis (A) , and wherein the second side openings (36) are formed on the second divergent portion (30) in the same number as the first side openings (26) and so as to be equidistant from each other and arranged on a second circumference centred on the central axis (A) .5) Device (1) according to claim 4 comprising four sleeves (5) , the first divergent portion (22) having four first side openings (26) , and the second divergent portion (30) having four second side openings (36) .6) Device (1) according to any one of the preceding claims, wherein the first divergent portion (22) and the first convergent portion (23) have a curved inner surface, and the second divergent portion (30) and the second convergent portion (31) have a curved outersurface, the gap (4) being defined between the inner surface and the outer surface.7) Device (1) according to any one of the preceding claims, further comprising introduction means (6) actuatable to favour the inlet of the fluid current into the first cavity (20) through the central opening (25) .8) Device (1) according to claim 7, wherein the introduction means (6) comprise a fan (6) arranged in the inlet portion (21) or in the first divergent portion (22) .9) Device (1) according to any one of the preceding claims, wherein the inner body (3) comprises a hollow second confluence portion (32) , which is at least partially positioned inside the first confluence portion (24) , which defines a second cavity (33) therein, and which has a plurality of second confluence openings (34) radially open towards the first cavity (20) , and wherein the rear openings are open towards the second cavity (33) .10) Device (1) according to any one of claims 1 to 8, wherein the rear openings are open directly towards the first cavity (20) .11) Device (1) according to any one of the preceding claims, wherein the first confluence portion (24) is composed of a plurality of wing profiles (270) separated from each other, and wherein each first confluence opening (27) is defined between two adjacent wing profiles (270 ) .

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