Flow accelerator device for enhancing ventilation and smoke extraction and uses thereof

Abstract

The present disclosure provides a flow accelerator device comprising an inverted aerofoil-shaped cross-section formed by one or more panels (41, 42), defining a leading edge (5), trailing edge (7), upper surface, and lower surface, where the lower surface extends further than the upper surface. Mechanically connected to a base (3) fixed upstream of a duct, the device generates low pressure within the duct to enhance air extraction. By leveraging aerodynamic principles, the device increases airflow efficiency in chimneys, fireplaces, ventilation towers, and similar structures. Its application includes buildings such as residential houses, offices, and industrial facilities, providing effective airflow management and smoke extraction. The flow accelerator operates passively, requiring no external power, making it a sustainable solution for improving indoor air quality and smoke removal while maximizing energy efficiency.

Description

D E S C R I P T I O NFLOW ACCELERATOR DEVICE FOR ENHANCING VENTILATION AND SMOKE EXTRACTION AND USES THEREOFTECHNICAL FIELD

[0001] The present disclosure relates to a flow accelerator device for improving ventilation and smoke extraction. Specifically, the present disclosure is applicable to systems where airflow management is required, such as ventilation ducts, chimneys, fireplaces, and ventilation towers. The present disclosure utilizes aerodynamic principles to create low-pressure zones for facilitating the extraction of air or smoke from a duct. This device is particularly suited for energy-efficient airflow enhancement in residential, commercial, and industrial applications.BACKGROUND

[0002] The ventilation requirements of buildings arise from the natural deterioration of indoor air quality caused by occupancy and use. Improving this air quality is essential to enhance the comfort and well-being of occupants. Sometimes, the quality of indoor air is considerably degraded not just by the daily activities of their users, but by processes of biochemical degradation of materials used in their construction and furnishing, or even by the radioactive disintegration of elements present in the stones used in their construction or in the foundation soils (e.g., radon gas resulting from the radioactive disintegration of radium and which, when present in high concentrations, can have damaging effects in the health of building users).

[0003] High concentrations of water steam can also make the indoor air unhealthy as, once again, the adequate ventilation of spaces proves fundamental to "sweep away" the water particles suspended in the air, lowering their concentration to acceptable levels. In order to promote ventilation in buildings, everyday techniques and procedures as simple as opening windows to allow natural ventilation are usually executed.

[0004] Sometimes, there is also the provision of small ventilation openings in walls and both floor and roof slabs, which are strategically positioned to ensure "sweeping" flows that aerate spaces. However, the natural ventilation of spaces executed solely in this manner is not always sufficient or, due to climate reasons, is not always possible, which is why expensive and energy-intensive means, such as air conditioning, are often used to aid in the ventilation processes. The ventilation of small spaces, such as bathrooms, basements, or storage rooms, is also difficult because, due to the location of some of these spaces in the interior of buildings, it is not always possible to provide a window to the outside or, if possible, the size of these openings is not always generous.

[0005] In order to promote the ventilation of these spaces, mechanical devices, such as exhaust fans or extractors, are usually used. These usually work electrically, which implies electricity consumption every time these devices are activated. Their working principles are usually based on the artificial creation of low-pressure zones that "suck in" the air particles at higher pressure inside ducts and spaces, allowing the air to circulate and ventilation to take place. To this end, these devices often have a rotating fan or a rotating drum with an electrically driven shaft and it is through the movement of these fans and drums that the differences in pressure are created. These same devices are often associated with chimneys to enhance their smoke extractions, compensating for deficiencies in the natural extraction through their ducts.

[0006] As an alternative to mechanically driven devices with circuits, wind-driven devices, known as wind-driven ventilators / wind roof ventilators / turbine ventilators, have been commercialized for many years. These devices have a rotating hood with several blades that allow it to rotate according to the force exerted by the wind. As it rotates, a low-pressure zone is generated and the vacuum effect produced allows the air contained upstream of the device to be "sucked in".

[0007] The present disclosure also uses the wind as the "motor" for the entire gas extraction process, and therefore constitutes an alternative wind-driven ventilators.

[0008] Conventional natural ventilation systems currently known in the art generally rely on passive architectural or mechanical solutions such as solar chimneys, static or rotary extractors, discharge outlets equipped with grilles, and ducts operating on thebasis of thermal draft. These systems typically exploit temperature differentials or basic pressure differences to induce airflow through a building, and in some cases incorporate rotating elements driven directly by wind action.

[0009] From the aforementioned, it can be understood that mechanical means requiring mainly electrical energy sources are often used to compensate for deficiencies in the natural ventilation processes of buildings, small spaces or chimneys, for example. The disadvantages of using such devices are mainly related to the amount of energy consumed and with the initial costs of acquisition of these kinds of devices, whose mechanical component usually increases their price.

[0010] Accordingly, there is a need for a device that facilitates ventilation and smoke extraction without energy consumption and at a low acquisition cost. Such a device should leverage external wind to create low-pressure zones that enable the extraction of air from an upstream duct. To achieve this, the device can utilize an inverted aerofoil shape, operating based on the principles of aerodynamics and fluid mechanics. Furthermore, to minimize dependency on wind direction, the device must incorporate a mechanism that ensures proper alignment with the prevailing wind direction at any given moment.

[0011] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.GENERAL DESCRIPTION

[0012] The present disclosure describes an air flow accelerator device with the shape of an aerofoil, in which one of its embodiments comprises a flow accelerator which includes one or more upper panels with an inverted aerofoil-shaped cross-section, positioned downstream of a given duct, the length of the surface between the leading edge and the trailing edge of which is greater on the lower surface than on the upper surface, mechanically connected to a base with a fixed relative position with respect to a given upstream duct.

[0013] The present disclosure relates to a passive flow accelerator device for enhancing ventilation or smoke extraction of a duct, in particular chimneys, ventilation towers, or similar airflow conduits, without requiring electrical energy consumption.

[0014] The device comprises an aerodynamic body having an inverted aerofoil profile, mechanically connected to a base fixed at or upstream of a duct inlet and positioned above said inlet. When exposed to ambient wind, the aerodynamic body interacts with the external airflow so as to generate a pressure depression at the duct inlet, thereby promoting airflow extraction from the duct. Surprisingly the present solution improves airflow or smoke extraction from a duct in an energy-efficient manner using a passive device without moving mechanical extraction components.

[0015] The present solution provides passive ventilation and smoke extraction device capable of generating stable and significant suction under low and variable wind conditions, in particular at wind speeds of 2 m / s or lower, while avoiding moving parts, electrical energy consumption and directional instability, and while achieving airflow rates comparable to mechanically driven ventilation systems.

[0016] The term flow accelerator device designates a passive aerodynamic device configured to enhance airflow or smoke extraction from a duct by converting kinetic energy of an external airflow into a pressure depression at a duct inlet.

[0017] An inverted aerofoil cross-section refers to an aerofoil profile oriented such that, during operation, a region of reduced static pressure is generated on a side of the profile facing a duct inlet, thereby promoting suction at said inlet.

[0018] The expression one or more panels refers to one or several rigid structural elements which, when assembled, jointly define the aerodynamic shape of the inverted aerofoil cross-section.

[0019] The terms leading edge and trailing edge respectively designate the upstreamfacing edge and the downstream-facing edge of the aerofoil cross-section with respect to an incoming airflow.

[0020] The upper surface and lower surface refer to the opposing aerodynamic surfaces extending between the leading edge and the trailing edge, wherein the lowersurface extends further than the upper surface in a chordwise direction so as to modify the pressure distribution around the aerofoil.

[0021] The chord length refers to the straight-line distance between the leading edge and the trailing edge of the inverted aerofoil cross-section.

[0022] The term camber refers to the maximum deviation of the mean line of the aerofoil cross-section from the chord line, expressed as a percentage of the chord length.

[0023] The term relative thickness refers to the maximum thickness of the aerofoil cross-section measured perpendicular to the chord line and expressed as a percentage of the chord length.

[0024] The base is a structural element configured to mechanically support the aerodynamic body and to be fixed to a structure at or near a duct inlet, including a chimney, ventilation duct, or similar airflow conduit.

[0025] The expression upstream of a duct inlet refers to a position external to the duct and located in the region from which air enters the duct during extraction.

[0026] The vertical distance from the duct inlet refers to the distance measured along a vertical axis between a reference plane at the duct inlet opening and a reference point of the aerodynamic body.

[0027] The angle of attack refers to the angle between a chord line of the inverted aerofoil cross-section and a direction of an incident airflow.

[0028] The Reynolds number refers to a dimensionless parameter calculated based on the chord length of the aerofoil cross-section, the velocity of the incident airflow, and the kinematic viscosity of air.

[0029] A pressure depression at the duct inlet refers to a reduction of static pressure measured at or immediately adjacent to the duct inlet relative to ambient atmospheric pressure.

[0030] The expression configured to cooperate with an internal geometry of the duct means that the flow accelerator device is arranged to function in conjunction with theshape and dimensions of the duct so as to enhance airflow extraction without requiring active mechanical or electrical components.

[0031] In another proposed embodiment, the flow accelerator device comprises one or more upper panels with a cross-section in the shape of an inverted aerofoil, with a geometry according to the geometry of one or the combination of at least two of the following geometries: straight; trapezoidal; elliptical; arrow; negative arrow; folded arrow; delta; folded delta; ogival; any aerodynamic geometry capable of generating, when exposed to wind in the Reynolds number range from 70,000 to 550,000, a lift coefficient Cl of at least 0.5 and a lift-to-drag ratio Cl / Cd of at least 4 and with a frontal section that develops according to a shape or a combination of at least two of the following shapes: in positive dihedral; in negative dihedral; in gull; or in any other shape accepted in aeronautics.

[0032] In yet another embodiment, the flow accelerator device comprises:- a rotating base that allows full rotation, in the plan in which it is contained, of the upper panel or panels with an inverted aerofoil-shaped cross section. - at least one fin, in vertical or inclined position, directly connected to the panel or panels with an inverted aerofoil-shaped cross section, or by means of one or more connecting rods.

[0033] In yet another proposed embodiment, the flow accelerator device comprises:- a fairing limited at the bottom by a base and at the top by at least one upper panel with an inverted aerofoil-shaped cross section.- at least one opening positioned below the leading edge, protected or not by a grid of various shapes.- at least one opening positioned below the trailing edge, protected or not by a grid of various shapes.- at least one opening, with any aerodynamic geometry capable of generating, when exposed to wind in the Reynolds number range from 70,000 to 550,000, a lift coefficient Cl of at least 0.5 and a lift-to-drag ratio Cl / Cd of at least 4, communicating with the upstream duct.

[0034] In yet another proposed embodiment, the flow accelerator device comprises a connecting part to the upstream duct capable of making the transition, preferably with a reduction in the cross-sectional area, between the section of the upstream duct and the section of the opening communicating with the upstream duct.

[0035] The aim of the present disclosure is to present a low-cost solution with no need for energy consumption to accelerate gas flow. It has obvious applications in ventilation and gas extraction systems and can, among others, integrate natural ventilation systems in buildings, integrate small space ventilation systems, and be used to enhance chimney smoke extraction. The present disclosure can have multiple embodiments, all of which have in common the use of one or more aerofoil profiles in an inverted position in relation to what happens in aeronautics.

[0036] The principle of operation of the present disclosure involves concepts of fluid mechanics and aeronautics. The device presented herein is placed at the end of a duct and should be positioned in a place subjected to air flows outside the duct, such as the flows naturally generated by the wind. When subjected to interaction with the wind, the inverted aerofoil profile of the present disclosure makes it possible to create a low-pressure zone immediately above the end of the duct it serves. Because the air contained in the duct is at a higher pressure than the pressure of the air passing immediately below the surface of the inverted aerofoil (and immediately above the end of the duct), in accordance with the principle of Bernoulli (according to which the movement of air is results from the difference in pressure, moving from higher pressure points to lower pressure points), the air contained in the duct is "sucked in" by the device according to the present disclosure, forcing its exit from the duct, improving the ventilation / extraction of circulated air.

[0037] In fact, the operation of the present disclosure takes advantage of aerofoilshaped sections. An aerofoil is a profile designed to cause variations in the amount of movement of the gaseous particles that interact with it. In aviation, for example, the aerofoil is the cross-section of the wing. Its shape "cuts" the air at its leading edge, dividing the air mass into a lower mass, whose particles travel along the lower surface of the aerofoil at a given speed v, at a given pressure p,, and an upper mass, whose particles travel along the upper surface of the same aerofoil at a speed vsand at apressure ps. It happens that the aerofoil has a longer upper surface than its lower surface, which means that the air masses that interact with the aerofoil travel different distances above and below the aerofoil. Thus, an air particle which travels along the contact with the upper surface of the wing travels a greater distance (ds) than the distance travelled by a particle that travels along the contact with the lower surface of the same wing (d,j.

[0038] However, the two particles travel different distances in the same time period, as they arrive at the trailing edge at the same time. This means that the air particle traveling along the upper surface of the wing is travelling at a higher speed than the particle that travels along its lower surface (vs> v,j. On the other hand, according to Bernoulli's principle, lower fluid velocity corresponds to higher pressure, while higher fluid velocity corresponds to lower pressure. As a result, the pressure acting on the lower surface of the wing (p,) is higher than the pressure acting on its upper surface (ps). This pressure differential results in a force that sustains the flight of the aircraft, which is as great as the speed at which the air is displaced.

[0039] Building on the fundamental principles governing aerofoil operation, the present disclosure employs an aerofoil profile in a manner opposite to its conventional use in aeronautics. In aeronautics, the aerofoil's largest surface faces upward to generate a region of lower pressure above it. In contrast, the present disclosure aims to create a low-pressure zone immediately above the terminus of a duct to enhance air extraction. To achieve this, the aerofoil is positioned downstream of the duct in an inverted orientation, with its largest surface facing downward.

[0040] Owing to the inversion of the aerofoil's position in relation to its traditional position in aeronautics, the logic of velocity (v), pressure (p) and distance (d) differentials is inverted. Based on fluid mechanics, this profile generates pressure differences in the air flow between the upper and lower parts of the profile, guaranteeing negative pressures at the terminus of the duct it overlaps. In this case, the upper surface has a shorter distance (ds) than the lower surface of the profile (d,j. As previously described, the particles in the air flow that go around the panel have different speeds, since the distance travelled is also different.

[0041] Once again, using Bernoulli's principle, since the distance is greater, the speed at the bottom is higher and so the pressure is lower. It follows that:di > dsVi > vsPi <Ps.

[0042] The device described can acquire different configurations, but always with the aim of providing and enhancing the "chimney effect" in the air ducts it serves. There is, however, the difficulty of permanently enhancing the depression created by the inverted aerofoil. Wind is a natural phenomenon due to the differences in pressure and temperature between air masses and its direction is fickle. For pressures to be as low as possible, it is important that the air passing through the aerofoil profile does so at the highest possible speed. To achieve this, it is imperative that the leading edge of the aerofoil is perpendicular to the wind direction at any time. In order to achieve this, the present disclosure also includes, in several of its embodiments, an articulated base which allows the aerofoil to rotate in the horizontal plane and one or more vertical or inclined fins which, similarly to what happens with an aircraft in the field of aeronautics, allow the aerofoil to be stabilized in the desired position, assuming the direction taken by the wind.

[0043] The exclusive reliance on wind energy aligns the present disclosure with principles of sustainability, providing an environmentally friendly solution that reduces dependence on non-renewable energy sources. The possibility of integrating discarded parts from different sectors of industry, such as, depending on the scale, parts produced by the aeronautical industry or sections of wind blades for larger applications, also allows the present disclosure to benefit from circular economy logic.

[0044] Conventional natural ventilation systems known in the art generally rely on passive architectural or mechanical solutions such as solar chimneys, static or rotary roof extractors, discharge openings provided with grilles, or ducts operating predominantly on the basis of thermal draft. While such systems may provide a certain degree of airflow under favourable conditions, they are typically limited in efficiency at low wind speeds, exhibit directional dependency, or require moving parts that introduce noise, vibration and maintenance requirements.

[0045] Furthermore, none of the known solutions employs a three-dimensional aerodynamic aerofoil specifically configured to generate a localised region of reduced pressure by wind action and arranged in coordinated interaction with an internal conical ventilation duct. In particular, the prior art fails to disclose a device in which the external aerodynamic geometry, the internal duct geometry and the architectural geometry of the building are designed as an integrated aerodynamic device.

[0046] More specifically, the known art does not teach or suggest a ventilation arrangement for a building of circular plan in which the geometry of the structure, the shape of the internal duct and an external aerofoil cooperate to simultaneously enhance the chimney effect, the internal Venturi effect within the duct, and the external Venturi effect induced by wind flowing over the aerofoil, while remaining responsive to wind from any direction without the need for active orientation mechanisms.

[0047] As a result, existing systems do not achieve stable suction under weak wind conditions, do not provide continuous performance under changing wind directions, and frequently require mechanical assistance to reach acceptable ventilation rates, leading to increased energy consumption, noise generation and maintenance.

[0048] The disclosed technology overcomes these limitations by providing a flow accelerator device capable of significantly improving natural airflow extraction while operating exclusively on ambient wind and thermal effects. Experimental and simulated results demonstrate an increase in natural ventilation airflow of approximately 40% to 60% compared to equivalent systems without the aerodynamic aerofoil. This enhanced extraction effect enables a reduction of approximately 70% to 90% in the energy required for mechanical ventilation, or in certain operating regimes allows mechanical ventilation to be eliminated entirely.

[0049] The device remains operational and stable at wind speeds as low as 2 m / s, ensuring effective ventilation even under weak wind conditions commonly encountered in urban environments. In preferred embodiments, the device operates without any mandatory moving parts, thereby minimising wear, reducing maintenance requirements and eliminating failure modes associated with rotary extractors.

[0050] The device is particularly well suited for buildings with circular or rotationally symmetric floor plans, which naturally distribute wind loads uniformly and cooperate aerodynamically with the external aerofoil to achieve omnidirectional performance. The external aerodynamic element further exhibits structural and aerodynamic synergy with internal conical ventilation ducts, reinforcing both the chimney effect and the Venturi-induced pressure reduction within the duct.

[0051] Additionally, the geometry of the aerofoil and its positioning relative to the duct opening provide inherent protection against rain, snow and the ingress of birds or debris, without the need for additional protective elements. Compared to rotary or turbine-based ventilators, the device produces significantly lower noise and vibration levels, improving occupant comfort and reducing structural fatigue.

[0052] The enhanced performance of the disclosed device does not result from a mere juxtaposition of known aerodynamic effects, but from a synergistic interaction between the inverted aerofoil geometry, the calibrated external Venturi gap, the internal conical duct and the vertical height of the duct, whereby the combined pressure depression exceeds the sum of the individual contributions.

[0053] By combining architectural geometry, internal duct design and external aerodynamic shaping into a single passive system, the disclosed technology enables continuous, stable ventilation operation on a 24-hour basis without energy consumption, representing a substantial technical advance over the known state of the art.

[0054] An aspect of the present disclosure relates to a flow accelerator device, for enhancing ventilation or smoke extraction of a duct, comprising: an inverted aerofoilshaped cross-section formed by one or more panels, the one or more panels defining a leading edge (5), a trailing edge (7), an upper surface and a lower surface; and wherein the leading edge, the trailing edge, and the one or more panels are configured such that the lower surface extends further than the upper surface; and wherein, the flow accelerator device is mechanically connected to a base (2) that is fixed to an upstream of a duct, for generating a low-pressure therein to facilitate air extraction.

[0055] An aspect of the present disclosure relates to a flow accelerator device for enhancing ventilation or smoke extraction of a duct, comprising: an inverted aerofoilshaped cross-section, formed by one or more panels, the one or more panels defining a leading edge, a trailing edge, an upper surface and a lower surface; wherein the leading edge, the trailing edge, and the one or more panels are configured such that the lower surface extends further than the upper surface; and wherein, the flow accelerator device is mechanically connected to a base that is fixed to an upstream of a duct, for generating a low-pressure therein to facilitate air extraction; wherein the inverted aerofoil-shaped cross-section comprises a camber from 2% to 4% of the chord length of the aerofoil cross-section and a relative thickness from 12% to 18% of said chord length; wherein the inverted aerofoil -shaped cross-section is positioned above a duct inlet at a vertical distance from 0.1 to 0.3 times of the duct diameter; wherein the inverted aerofoil-shaped cross-section is configured to operate at an angle of attack from 5° to 12° and within a Reynolds number range from 70,000 to 550,000 such that, when exposed to ambient wind of at least 2 m / s, the inverted aerofoil-shaped crosssection generates a pressure depression of at least 2 Pa at the duct inlet; the device being configured to cooperate with an internal duct geometry to enhance airflow extraction without electrical energy consumption, representing a passive solution and at least a 60% reduction in energy consumption.

[0056] In an embodiment the inverted aerofoil-shaped cross-section has a geometry selected from one or a combination of at least two of the following geometries: straight, trapezoidal, elliptical, arrow, negative arrow, folded arrow, delta, folded delta, ogival, variable geometry, or similar.

[0057] In an embodiment at least a frontal section of the flow accelerator device develops in a shape or a combination of at least two of the following shapes: positive dihedral, negative dihedral, gull shape, or similar.

[0058] In a further embodiment the flow accelerator device comprises an aerofoil support connecting the one or more panels of the flow accelerator device to the base.

[0059] In an embodiment the flow accelerator device comprises a rotational base configured to allow articulated rotation of the flow accelerator device in a horizontal plane, for maintaining the leading-edge perpendicular to a prevailing wind direction.

[0060] In a further embodiment the rotational base includes a flat top surface, for supporting the inverted aerofoil, having an outlet.

[0061] In an embodiment the flow accelerator device comprises a nozzle fitted into the outlet of the flat top surface of the rotational base.

[0062] In an embodiment the outlet nozzle comprises a bended end.

[0063] In a further embodiment the bended end comprises a deflection flap for optimizing airflow direction.

[0064] In a further embodiment the outlet has an upward protruding "V" cut or inverted "V" cut termination.

[0065] In an embodiment the flow accelerator device comprises at least one vertical fin for stabilizing the orientation of the flow accelerator device to the wind direction, optionally wherein the at least one fin is connected to one or more panels of the flow accelerator device via a vertical fin connecting rod.

[0066] In an embodiment the flow accelerator device comprises a fairing limited at a bottom by the rotational base and at a top by the one or more panels.

[0067] In a further embodiment the fairing comprises frontal and rear openings, for allowing air flow, optionally further comprising a frontal protection grid and a rear protection.

[0068] Another aspect of the present disclosure relates to the use of the flow accelerator device, positioned at the top of a chimney, a fireplace, an installation tower, a ventilation tower, or any similar structure for facilitating airflow management.

[0069] In an embodiment, the device is installed on a building having a substantially circular plan, wherein the rotational symmetry of the structure cooperates with the aerofoil geometry to provide omnidirectional wind responsiveness without active control.

[0070] Another aspect of the present disclosure relates to the use of the flow accelerator device in buildings, including residential houses, office buildings, industrial facilities, tourism buildings, and similar structures, for enhancing ventilation or smoke extraction

[0071] Other aspects and advantages of the present disclosure can be better understood by looking at its detailed description which includes reference to the attached figures, which are intended to be analysed together with the textual descriptions.

[0072] The present disclosure can, however, be embodied in many different ways and should not be understood as limited to the embodiments set out here; on the contrary, these embodiments are provided only by way of illustration and not as a limitation.BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of the present disclosure.

[0074] In order to make it easier to understand the present disclosure of the flow accelerator device, figures are attached, which represent embodiments that, however, are not intended to limit the scope of the present disclosure.

[0075] Repeated reference numerals indicate identical elements across the embodiments for clarity and conciseness. Moreover, previously described reference numerals are reused where applicable, while additional elements are introduced as needed.

[0076] Figure 1 illustrates a three-dimensional representation of the flow accelerator device in one of its embodiments, in the shape of an inverted aerofoil placed on top of a chimney. The reference numerals correspond to the following:(1) Chimney;(2) Base of the flow accelerator device;(3) Rotational base;(4) Duct Terminus;(5) Aerofoil leading edge;(6) Aerofoil (inverted);(7) Aerofoil trailing edge;(8) Aerofoil support;(9) Vertical fin connecting rod;(10) Vertical fin;(11) Rotational axis of the rotational base.

[0077] Figure 2a shows a three-dimensional representation of another embodiment of the flow accelerator device disposed at the top of a chimney, in which it can be seen, in three-dimensional section, the inside of the chimney duct and the transverse geometry of the inverted aerofoil that makes up this embodiment of the said flow accelerator device. The additional reference numerals correspond to the following:(12) Rotational base flat top;(13) Outlet;(14) Duct cross-section reduction part (i.e. the nozzle);(15) Narrowing of the section.

[0078] Figure 2b illustrates the same embodiment of the flow accelerator device illustrated in Figure 2a, positioned at the top of a chimney, in which the interior of the chimney duct and the cross-sectional geometry of the inverted aerofoil that materializes the flow accelerator device can be seen in a two-dimensional section.

[0079] Figure 3a illustrates another embodiment of the flow accelerator device, positioned at the top of a chimney, where the area where low pressures are generated is delimited and protected. The additional reference numerals correspond to the following components:(16) Frontal protection grid;(17) Fairing.

[0080] Figure 3b represents the same embodiment of the flow accelerator device illustrated in Figure 3a, seen from a 3-dimensional perspective, from below. The additional number in this figure corresponds to:(18) Rear protection grid.

[0081] Figure 3c illustrates a three-dimensional representation of the same embodiment of the flow accelerator device placed at the top of a chimney seen in Figures 3a and 3b, in which it is possible to see, in three-dimensional section, the inside of the chimney duct and the transverse geometry of the inverted aerofoil that makes up this embodiment of the flow accelerator.

[0082] Figure 3d shows a two-dimensional, cross-sectional representation of the same embodiment of the flow accelerator device placed at the top of a chimney seen in Figures 3a, 3b and 3c. This figure highlights the air flows involved in the flow acceleration phenomena. The additional reference numerals correspond to the following:(19) Upper surface of the aerofoil (inverted);(20) Lower surface of the aerofoil (inverted);(21) Low pressure zone;(22) Flow confluence zone;(23) Flow that comes from the duct;(24) Aerofoil (inverted) upper flow;(25) Aerofoil (inverted) lower flow.

[0083] Figure 3e shows a three-dimensional representation of another embodiment of the flow accelerator device placed at the top of a chimney. Here, it can be seen, in three-dimensional section, the inside of the chimney duct and the transverse geometry of the inverted aerofoil that makes up this embodiment of the flow accelerator, which has the particularity of having a bended outlet that changes its geometry from illustration i) to illustration ii). The additional reference numerals correspond to the following components:(43) Outlet with bended end;(44) Outlet with bended end and deflection flap;(45) Deflection flap.

[0084] Figure 3f illustrates a two-dimensional cross-section representation of the embodiment seen in illustration ii) of Figure 3e of the flow accelerator device. The additional reference numeral corresponds to:(46) Detailed view of the outlet with bended end and deflection flap.

[0085] Figure 4a shows another embodiment of the flow accelerator device, in which the inverted aerofoil-shaped panel responsible for generating depressions and consequently accelerating the flow, has a longitudinal "V" shape (or positive dihedral). In this three-dimensional representation, the additional reference numeral corresponds to:(26) V-shaped aerofoil (inverted) or positive dihedral.

[0086] Figure 4b shows another embodiment of the flow accelerator device, in which the inverted aerofoil-shaped panel responsible for generating depressions and consequently accelerating the flow, has a longitudinal "V" shape (or positive dihedral) and the air flow outlet of the duct ends with a "V" cut before the air flow crosses with the outside air flow that passes under the flow accelerator panel. In this three-dimensional representation, the additional reference numeral corresponds to:(27) Outlet with V cut termination.

[0087] Figure 4c illustrates another embodiment of the flow accelerator device, in which the inverted aerofoil-shaped panel responsible for generating depressions and consequent flow acceleration, has a longitudinal "V" shape (or positive dihedral) and where the exit zone of the flow that comes from the duct is protected by fairings and protective grids. Figure 4d represents a lower three-dimensional view of the same embodiment of the flow accelerator device shown in figure 4c.

[0088] Figure 4e shows a three-dimensional sectional view of the same embodiment of the flow accelerator device placed at the top of a chimney seen in Figures 4c and 4d.

[0089] Figure 5a illustrates another embodiment of the flow generator device in the form of an inverted aerofoil with an inverted "V" longitudinal shape (or negative dihedral). The additional reference numerals correspond to:(28) Inverted V-shaped aerofoil (inverted) or negative dihedral;(29) Outlet with inverted cut termination.

[0090] Figure 5b illustrates another embodiment of the flow accelerator device using a panel in the shape of an inverted aerofoil profile with an inverted "V" longitudinal shape (or negative dihedral), and in which the flow exit zone coming from the duct is protected by fairings and protective grilles.

[0091] Figure 5c shows the same embodiment of the flow accelerator device shown in Figure 5b, from a lower three-dimensional perspective.

[0092] Figure 5d illustrates a three-dimensional representation of the same embodiment of the flow accelerator device seen in Figures 5b and 5c, in which it is possible to see, in a three-dimensional section, the end of the chimney duct and the internal appearance of the flow confluence area of the system, as well as part of the inverted "V" aerofoil that makes up this embodiment of the flow accelerator device.

[0093] Figure 6 illustrates an example of the application of one of the embodiments in which the flow accelerator device is realized, namely its application on the top of a chimney connected to a fireplace. The following situations are illustrated: i) Three-dimensional view of fireplace, chimney and flow accelerator device; ii) Three-dimensional cross-sectional view of the fireplace, chimney and flow accelerator device; and iii) Two-dimensional cross-section of fireplace, chimney and flow accelerator device, wherein the additional reference numerals correspond to:(31) Fireplace;(32) Fireplace internal duct;(33) Flow accelerator device with single inverted aerofoil panel.

[0094] Figure 7 shows an example of the application of one of the embodiments of the flow accelerator device, namely its application as an extractor for a ventilation duct. In this figure, the additional reference numerals correspond to:(34) Flow accelerator device with inverted V-shaped inverted aerofoil;(35) Ventilation duct;(36) Installation tower for the flow accelerator device;(37) Slab.

[0095] Figure 8 shows an embodiment of the present disclosure which consists in a single inverted aerofoil, capable of rotation and directable according to the wind direction at any moment, placed at the top of an inner central ventilation tower that is somewhere in an exemplificative four-storey building. The additional reference numerals correspond to: (38) Four-storey building;(39) Ventilation tower;(40) Connection base to the flow accelerator device;(41) Large single inverted aerofoil panel;(42) Fin of the large single inverted aerofoil panel.DETAILED DESCRIPTION

[0096] With reference to the figures, some of the embodiments of the present disclosure are now described in more detail, as well as other aspects and advantages that the flow accelerator device makes possible by using principles of physics and fluid mechanics, such as Bernoulli's theorem or the Venturi effect. It will be focused the technical advantages of the device and the environmental advantages of using it, as it allows gas flows to be drawn off (for ventilation purposes, for example) in a completely natural way, without the need for electrical or mechanical systems, or any other operating principle that requires energy from non-renewable sources. The model presented is merely an example and can be varied.

[0097] The present disclosure relates to a flow accelerator device for improving ventilation and smoke extraction.

[0098] The flow accelerator device now described comprises an aerofoil having a defined profile geometry configured to interact with ambient wind flow in order to generate a region of reduced pressure above the inlet of a duct, thereby enhancing air extraction through said duct.

[0099] In an embodiment, the aerofoil profile geometry is characterised by a relative camber, defined as the maximum deviation of the mean camber line from the chordline, ranging between 2% and 4% of the chord length. Such a low to moderate camber ensures stable aerodynamic behaviour under variable and turbulent wind conditions typically encountered in urban environments, reduces the risk of oscillation or premature stall at low angles of attack, and provides effective performance at wind speeds from 2 m / s to 8 m / s.

[0100] In an embodiment, the aerofoil further comprises a relative thickness, defined as the ratio between the maximum profile thickness and the chord length, comprised from 12% to 18%. Preferable relative thickness values from 12% to 15% provide a high lift-to-drag efficiency, while thicknesses up to 18% offer increased structural rigidity without substantially degrading the aerodynamic flow over the profile. The aerofoil may correspond to a symmetric or cambered profile, including but not limited to profiles of the NACA family, such as NACA 4412, NACA 2412, NACA 0012 or NACA 0015, profiles of the NACA 23xx series, or Clark-Y type profiles, without being limited to any specific family, provided the above-mentioned geometric constraints are satisfied.

[0101] During operation, the aerofoil is arranged to operate at an angle of attack comprised from 5° to 12°, preferably from 6° to 10°. Within this interval, a stable low-pressure region is generated over the duct opening, while avoiding flow separation. Experimental evaluations indicate that angles of attack from 5° to 8° provide moderate lift with very low drag, whereas angles from 8° to 12° yield near-maximum lift coefficients prior to the onset of stall.

[0102] Under typical operating conditions corresponding to urban wind speeds from 2 m / s to 8 m / s, the aerofoil exhibits a minimum lift coefficient Cl of at least 0.5, preferably from 0.6 to 1.0, and a drag coefficient Cd not exceeding 0.15, preferably from 0.05 to 0.12. The resulting aerodynamic efficiency, defined by the ratio Cl / Cd, is therefore equal to or greater than 4.0, and preferably from 6.0 to 10.0, ensuring effective suction generation with limited aerodynamic losses.

[0103] In an embodiment, the aerofoil has an aspect ratio, defined as the ratio between the span and the chord length, comprised from 3 to 6. This range represents a compromise between aerodynamic efficiency and mechanical robustness, as higheraspect ratios increase lift generation but reduce structural resistance to wind loads, whereas excessively low aspect ratios increase induced drag and turbulence.

[0104] The aerofoil is dimensioned to operate within a Reynolds number range from 70,000 to 550,000, ensuring stable aerodynamic behaviour over the expected operating envelope. The Reynolds number Re is given by the relation Re = p v c / p, where p is the air density, v is the wind velocity, c is the chord length and p is the dynamic viscosity of air. For air at standard conditions, with density p = 1.204 kg / m3and dynamic viscosity p = 1.8 x 10“5Pa-s, and for chord lengths between 0.5 m and 0.8 m, Reynolds numbers from 70,000 to 120,000 are obtained at wind speeds of 2 m / s, values from 200,000 to 350,000 at wind speeds of 5 m / s, and values up to 550,000 at wind speeds of 8 m / s.

[0105] In an embodiment, the flow accelerator device according to claim 1, wherein the inverted aerofoil cross-section is dimensioned and positioned such that, for an incident airflow velocity from 2 m / s to 15 m / s and a chord length from 0.15 m to 1.2 m, the Reynolds number calculated based on air properties under standard atmospheric conditions lies within the range from 70,000 to 550,000.

[0106] In an embodiment, the aerofoil is positioned above the inlet of the duct at a vertical distance comprised from 0.1 to 0.3 times the duct diameter, thereby forming an external Venturi-type aerodynamic constriction. For a duct diameter of approximately 2 m, this corresponds to a vertical spacing from 0.2 m to 0.6 m. Smaller gaps intensify the Venturi effect but may promote recirculation, while larger gaps reduce the induced suction. The selected range ensures an optimal balance between pressure reduction and flow stability.

[0107] Assembly tolerances are defined to preserve aerodynamic performance. The angular alignment tolerance of the aerofoil relative to the intended angle of attack does not exceed ±1°. Lateral positioning tolerances between supporting elements do not exceed ±5 mm, and variations in the vertical gap relative to the duct inlet do not exceed ±10 mm without significantly affecting suction performance. Under aerodynamic loading, torsional deformation of the aerofoil is limited to a maximum of 2° to 4°.

[0108] In embodiments wherein the aerofoil is mounted on a rotatable base allowing passive alignment with the wind direction, the rotational mechanism is configured such that the static friction torque does not exceed 1.0 N-m, preferably remaining from 0.5 to 1.0 N-m. The force required to initiate rotation is preferably from 3 N to 10 N, thereby ensuring smooth alignment even at low wind speeds while preventing oscillatory behaviour under turbulent conditions.

[0109] The horizontal projection area of the aerofoil exceeds the cross-sectional area of the duct inlet, such that the airflow over the suction side of the aerofoil generates a pressure reduction over the entire duct opening, avoids stagnant zones, and promotes uniform suction across the duct section.

[0110] In terms of global performance, the aerofoil is considered functional when it generates an additional aerodynamic pressure drop of at least 2 Pa at wind speeds equal to or greater than 2 m / s. The induced airflow through the duct is increased by at least 20% relative to an equivalent system without the aerofoil, with preferred increases between 40% and 60%. The resulting aerodynamic assistance leads to a reduction of at least 60% in the mechanical ventilation power required to achieve a given airflow rate. Directional stability is maintained such that lateral oscillations remain below 5° under turbulent wind conditions.

[0111] Overall, the aerofoil comprises a camber from 2% to 4% of the chord and a relative thickness from 12% to 18%, operates at angles of attack from 5° to 12°, and delivers lift and drag coefficients of Cl > 0.5 and Cd < 0.15, respectively, with an aerodynamic efficiency Cl / Cd exceeding 4. Installed at a vertical distance from 0.1 to 0.3 times the duct diameter, and optimised for Reynolds numbers from 70,000 to 550,000, the device provides a stable and efficient aerodynamic suction enhancement suitable for urban wind conditions, with controlled tolerances and passive alignment capability where applicable.

[0112] Figure 1 illustrates a possible embodiment of the present disclosure in which a flow accelerator device is visible at the top of a chimney (1), used as a means of extracting smoke to improve its draft. In this possible embodiment, the flow accelerator device is made up of a panel in the shape of an inverted aerofoil (6). The base of the flow accelerator device (2) is fixed to the top of the chimney (1) and isattached to it. At the same time, it serves as the base for the rotational base (3) of the panel, which has an axis (11) along the entire length of its lower surface, allowing it to rotate 360^ in relation to the base of the flow accelerator device (2) and the chimney (1). In order to support the inverted aerofoil (6) and connect it with the rotating base (3), at least one (two in this illustration) aerofoil support (8) extends from it.

[0113] Starting preferably from the aerofoil support (8) there is at least one vertical fin connecting rod (9) which has the function of supporting the vertical fin (10). The wind interacts with the panel in the shape of an inverted aerofoil (6), first contacting it at its aerofoil leading edge (5), then running over its entire upper and lower surface and ending the interaction when it passes the aerofoil trailing edge (7). As the wind is an atmospheric phenomenon whose direction varies from moment to moment, the illustrated device works regardless of the wind's direction, as at least one vertical fin (10), together with the possibility of rotating the rotational base (2) at any angle around the rotational axis of the rotational base (11), allows it to align itself with the wind's direction at any moment.

[0114] Once aligned with the wind direction, the inverted aerofoil (6) panel has its leading edge (5) perpendicular to the wind direction, which maximizes the device's performance as a depression generator and flow accelerator, allowing it, as a result of the interaction with the external wind that passes under its lower surface, to "sweep" the flow of gases coming from the duct terminus (4). Once again, it should be noted that Figure 1, like all the others in this document, are merely illustrative and not limiting, so the inverted aerofoil panel can take on other configurations, such that the leading edge angle is not perpendicular to the wind direction (reducing the panel's drag), or the vertical fin takes on different shapes and is repeated in different numbers to those illustrated. The illustrated device can also be equipped with electrical mechanisms to change the angle of the leading edge (5) by tilting the inverted aerofoil (6) panel by rotating the aerofoil support (8).

[0115] Figure 2a illustrates another embodiment the flow accelerator device through a three-dimensional cutaway representation of it positioned at the top of a chimney (1). This figure shows the base of the flow accelerator device (2), fixed to the chimney (1), which supports the rotational base (3), contacting it via the rotational axis of therotational base (11). This axis allows the entire assembly above the rotational base (3) to rotate through 360^ in the plane in which it is contained.

[0116] This assembly, which is supported by the rotational base, includes, among others, the inverted aerofoil (6) panel, illustrated with its leading (5) and trailing (7) edges, and the vertical fin (10). It should also be noted that in the illustrated embodiment, the rotational base (3) has a flat top (12), which helps to stabilize the air flow generated by the wind passing over the lower surface of the inverted aerofoil (6). On this flat top there is a negative shape that constitutes the outlet (13) of the rotational base, into which fits the termination of an additional component of the system which is the duct cross-section reduction part (i.e. the nozzle) (14). The purpose of this part is to channel the flow of gases from the duct to the outlet (13) of the rotational base, ensuring the transition between the sections of the duct and the nozzle which, as well as having different dimensions, can also have different cross-sectional shapes. This part can have the most varied dimensions and shapes, but it is always advisable to have a narrowing of the section (15), as this sudden narrowing of the section takes advantage of another physics concept, the Venturi principle.

[0117] In this narrowing, the velocity of the circulated flow increases, since, according to the above principle and the continuity equation (flow (Q) = Velocity (V) x Section area (A)), the circulated flow, by remaining constant, involves an increase in the flow velocity in the transition zone to the zone of the part with a smaller crosssection. In this way, the duct cross-section reduction part (i.e. the nozzle) (14) will also be responsible for improving the duct's exhaust.

[0118] The same embodiment illustrated in Figure 2a is shown in a two-dimensional cross-section in Figure 2b. Visible are the walls of the chimney (1), the base of the flow accelerator device (2), the rotational base (3) with its flat top (12), the rotational axis of the rotational base (11), the aerofoil support (8), the vertical fin connecting rod (9) and the vertical fin (10). Also visible is the inverted aerofoil (6) panel, with its leading edge (5) and trailing edge (7), showing the inverted positioning of this aerofoil in relation to the positioning it adopts in the aeronautical environment. The duct crosssection reduction part (i.e. the nozzle) (14) is also visible, as well as its narrowing of the section (15). Note that the duct cross-section reduction part (i.e. the nozzle) (14) isfixed and does not touch the rotational base (3), which, because it has a negative shape in the rotational base's outlet (13), can rotate freely without touching the duct cross-section reduction part (i.e. the nozzle) (14).

[0119] Figure 3a shows another possible embodiment for the flow accelerator device, consisting of a simple inverted aerofoil. In this design, the confluence zone of the air flows coming from the duct and the wind passing underneath the inverted aerofoil is surrounded by a fairing (17) whose purpose is to protect the interaction zone of these flows, guaranteeing minimal interference in the phenomena of the creation of depressions and suction of the air flow coming from inside the duct that leaves it through the outlet (13) of the rotational base. This flow confluence zone between the inverted aerofoil (6) panel and the rotational base flat top (12), protected by the fairing (17), also has a wind inlet zone just below the leading edge (5) and an outlet zone for the flows gathered from the wind and the gases coming out of the duct positioned just below the trailing edge (7).

[0120] These inlet and outlet areas are protected by grids whose function is to protect the flow confluence area from nesting and from the entry of any unwanted object into that area or into the duct. Visible in Figure 3a is only the front protection grid (16), which, like the wind inlet area it protects, is delimited at the bottom by the rotational base (3), at the top by the inverted aerofoil (6) panel and by the fairing (17) at the sides. With functions already explained above and also visible in Figure 3a, are a chimney (1) where this embodiment of the device is positioned; the base of the flow accelerator device (2); the rotational axis of the rotational base (11); the inverted aerofoil support (8), which in this case can even be dispensed with if the fairing (17) is strong enough to support the inverted aerofoil (6) panel; the vertical fin connecting rod (9) and the vertical fin (10).

[0121] Another three-dimensional view of the embodiment illustrated in Figure 3a is shown in Figure 3b. This view shows the base of the flow accelerator device (2); the rotational base (3); the leading edge (5); the inverted aerofoil (6) panel; the trailing edge (7), the inverted aerofoil support (8); the vertical fin connecting rod (9); the vertical fin (10); the lower part of the rotational base flat top (12); the rotational base outlet (13) and the fairing (17). Also visible in Figure 3b is the rear protection grid (18)with functions in all respects similar to those already described for the front protection grid (16) already described in the detailed analysis of Figure 3a.

[0122] Figure 3c shows the same embodiment of the present disclosure illustrated in Figures 3a and 3b, which is now represented in a two-dimensional section at the top of a chimney (1), revealing its cross-section. With functions already explained above, the components of the present disclosure are visible: the base of the flow accelerator device (2); the rotational base (3); the duct terminus (4); the leading edge (5); the inverted aerofoil-shaped (6) panel; the trailing edge (7), the inverted aerofoil support (8); the vertical fin (10); the rotational axis of the rotational base (11); the rotational base flat top (12); the outlet (13) of the rotational base; the Duct cross-section reduction part (i.e. the nozzle) (14); the narrowing of the section (15); the frontal protection grid and the rear protection grid (18). It can be seen from this illustration that the flow confluence zone is better protected in this possible embodiment of the present disclosure. Figure 3c also shows that another of the functions of the flow accelerator device referred to in the present disclosure is that, through its inverted aerofoil-shaped panel (6), it protects the inside of the duct from which it facilitates the extraction of the flows circulating there from the action of the rain, similar to what happens with the common "hats" and roofs of chimneys and ducts.

[0123] The illustration in Figure 3d takes advantage of the embodiment shown in Figures 3a, 3b and 3c to better explain the mechanics of the present disclosure. In this two-dimensional representation of a cross-section of the top of a chimney (1) where the flow accelerator system is applied, the various gas flows that interact in the present disclosure are represented. Thus, considering that the wind is blowing in a certain direction, the entire assembly above the base of the flow accelerator device (2) rotates around the rotational axis of the rotational base (11) (with the exception of the Duct cross-section reduction part (i.e. the nozzle) (14)), which is achieved by combining the 360^ rotation capacity of the axis (11) with the alignment produced by the interaction of the wind with the vertical fin (10) connected to the rest of the assembly by the fin connecting rod (9). In fact, the device's ability to align itself with the direction the wind is blowing at any given moment is of vital importance in ensuring that the leading edge (5) of the inverted aerofoil (6) panel is in a positionapproximately perpendicular to the direction taken by the wind, which enables the phenomena of pressure reduction and flow acceleration. In this way, the flow created by the wind (which blows in the direction shown by the arrows representing the horizontal flow) splits into two different flows when it touches the leading edge (5) of the inverted aerofoil (6) panel. One of the flows passes over the inverted aerofoil (6) panel - aerofoil upper flow (24) and is represented by the trajectories above the inverted aerofoil (6) panel.

[0124] The other flow from the outside wind, represented by the trajectory lines passing under the aerofoil, "cuts" the aerofoil from below - aerofoil lower flow (25). An air particle traveling in the aerofoil upper flow (24) and traversing the entire upper surface of the aerofoil (19) does so over a shorter distance (length measuring the contour of the upper surface of the inverted aerofoil, between the leading edge (5) and the trailing edge (7)) than an air particle traveling in the aerofoil lower flow (25) and traversing the entire lower surface of the inverted aerofoil (20). It happens that, as they both leave the leading edge (5) at the same moment in time, both the particle traveling along the upper contour of the aerofoil and the particle traveling along its lower contour arrive at the trailing edge (7) at the same time. For this to happen, the speed at which the particle traveling along the lower surface of the inverted aerofoil travels must be greater than the speed of the particle traveling along the upper surface of the aerofoil.

[0125] As it has been already seen in the Brief Description, according to Bernoulli's theorem, a higher velocity also corresponds to a lower pressure, so the inverted position of the aerofoil causes depressions in its lower part, which promotes the phenomenon of suction of the flow circulating in the duct below and which reaches the flow confluence zone (22) when it leaves the outlet (13) of the rotational base (3). This phenomenon of creating depressions is further enhanced by the abrupt narrowing of the section that occurs shortly after the air flow cuts the aerofoil at its leading edge (5) and passes the frontal protection grid (16), since when the aerofoil lower flow (25) passes the smaller cross-section between the lower surface of the aerofoil (20) and the rotational base flat top (12), a low pressures zone (21) is created, which contributes to the acceleration of the aerofoil lower flow (25). This flow acceleration caused by thenarrowing of the section is also explained by the Venturi effect and the continuity equation, given that, since the flow rate is constant, a reduction in section must invariably correspond to an increase in speed. The same effect is produced in the upward flow from the duct, which enters the Duct cross-section reduction part (i.e. the nozzle) (14) with a certain cross-sectional area and then experiences a sudden narrowing of the section (15), which also accelerates the particles traveling in this flow. The combination of all these phenomena means that somewhere at the flow confluence zone (22), the upward flow that comes from the duct (23), already accelerated at the narrowing of the section (15), changes direction and is accelerated again when it interacts with the aerofoil lower flow (25), creating a phenomenon of "suction" of this upward flow that comes from the duct (23) and improving the exhaust of the duct.

[0126] Figure 3e illustrates another two possible embodiments of the present disclosure that, although similar to the embodiments shown in Figures 3a, 3b, 3c and 3d, differs from them, mainly by the shape of the outlet. Illustration i) shows an outlet with bended end (43) as the way to expel the flows coming from the ventilation duct. This inverted aerofoil (6) device exhibits, among others, the vertical fin (10), the rotational axis of the rotational base (11) and the rotational base (3), allowing it to rotate and assume wind's direction at anytime. However, the outlet has a bended end close to the flat top of the rotational base (12). Its function is to direct the vertical flow, coming from the Duct cross-section reduction part (i.e. the nozzle) (14) and accelerated in the narrowing of the section (15), in such a way that slightly deflects the trajectory of the particles inside that vertical flow. This slight deflection allows those particles to interact with the particles traveling in the external wind flow, finding them with a soft angle than what happens by using a regular outlet (13), avoiding turbulent phenomena inside the aerofoil-based flow accelerator device. Illustration ii) shows a slightly different nozzle, also with bended end, but with a small lengthened zone, showing a deflection flap (45), that is the outlet with bended end and deflection flap (44). The way it works is pretty similar to the way that illustration i) embodiment works, but the lengthened deflection flap (45) closes the angle the wind flows and ductflows find each other, smoothing even more the desirable laminar regime the flows travel inside the flow accelerator device.

[0127] Figure 3f illustrates a two-dimensional cross-section view of the Figure 3e illustration ii) embodiment, focusing a detailed view of the outlet with bended end and deflection flap.

[0128] Figure 4a illustrates another embodiment of the flow accelerator device, this time using a panel in the shape of an "V"-shaped aerofoil or positive dihedral (26). This illustration shows the flow accelerator device used as a means of improving the draft of a chimney (1), to which it is attached by means of the base of the flow accelerator device (2), in contact with which is the rotational base (3), which has complete freedom of rotation. The inverted "V" or positive dihedral aerofoil (26) panel, whose leading edge (5) and trailing edge (7) develop in a "V" shape, is fixed and supported by the inverted aerofoil support (8). From the aerofoil or, alternatively, from the rotational base (3), extends the vertical fin of the connecting rod (9), which extends to the point where the vertical fin (10) is with the purposes already described. The "V"-shaped or positive dihedral inverted aerofoil (26) panel has advantages over the inverted aerofoil (6) panel seen in previous figures, since its "V" configuration guarantees a greater area of contact with the outside wind within the same width, which guarantees a greater area for creating depressions, maximizing the suction (and exhaust) capacity achieved in the duct that ends immediately below.

[0129] Another embodiment of the present disclosure that uses a panel in the shape of an inverted "V" or positive dihedral aerofoil (26) can be seen in Figure 4b. In this figure, the device of the present disclosure is used as a means of improving the draft of a chimney (1), featuring, like other forms of realization of the present disclosure already illustrated, a base of the flow accelerator device (2), on which the entire assembly above rotates, consisting of the rotational base (3) with its flat top (12), from which the support of the inverted aerofoil (8) departs. The V-shaped inverted aerofoil or positive dihedral (26) panel has a V-shaped leading edge (5) and trailing edge (7). The vertical fin (10), which ensures the correct orientation of the device in relation to the wind at any given moment, is connected to the panel in the shape of an inverted "V" aerofoil or positive dihedral (26) via the vertical fin connecting rod (9). The noveltyin this design is the existence of a duct outlet with a "V" cut termination (27), whose function is simply to "shape" the flow of gases coming from the chimney (1) or any duct, to the shape of the aerofoil-shaped panel that is superimposed and which provides the flow acceleration phenomena that allow the upward flow coming from the chimney (1) or duct to be "swept away". This duct outlet with "V" cut termination (27) can take on other configurations than the one illustrated, namely through shapes that make it conformal with the rotational base (3) (which modifies the flat top of the rotational base (12)), with the aim of minimizing possible turbulence phenomena when the wind flow comes into contact with this nozzle. This allows the flow regime to be laminar rather than turbulent, which also facilitates the air extraction phenomena from the conduit that is wanted to be created.

[0130] Figure 4c illustrates another embodiment of the flow accelerator device. In this other version of the system, the flow interaction zone is protected by a fairing (17), which extends from the rotational base (3) and from its flat top (12) to the inverted "V" or positive dihedral aerofoil panel (26), and which is located between the leading edge (5) and the trailing edge (7) of this same panel. The air flow from the wind enters the flow interaction zone through the intake protected by the front protection grid (16), interacting with the gas flow coming out of the outlet (13) of the rotational base, then exiting through an outtake protected by the rear protection grid (18). As with other embodiments of the system, the whole assembly can rotate around the base of the flow accelerator device (2), fixed to the chimney (1), to take better advantage of the wind direction at any given moment, which is guaranteed by the existence of the vertical fin (10), whose function and mode of operation has already been explained.

[0131] Another view of the embodiment of the flow accelerator device illustrated in Figure 4c can be seen in Figure 4d, which represents this design from a three-dimensional perspective seen from below. This illustration shows the base of the flow accelerator device (2); the rotational base (3); the rotational base flat top (12); the outlet (13) of the rotational base; the fairing (17); the rear protection grid (18); the inverted "V" or positive dihedral aerofoil panel (26); its leading edge (5) and trailing edge (7); the vertical fin connecting rod (9) and the vertical fin (10).

[0132] Figure 4e shows a three-dimensional cross-sectional view of the embodiment of the flow accelerator device shown in Figures 4c and 4d, applied to the top of a chimney (1). Visible are the base of the flow accelerator device (2); the rotational base (3); the rotational axis of the rotational base (11); the rotational base flat top (12); the outlet (13) of the rotational base; the Duct cross-section reduction part (i.e. the nozzle) (14); the narrowing of the section (15); the frontal protection grid (16); the fairing (17); the rear protection grid (18); the inverted "V" or positive dihedral aerofoil panel (26); its leading edge (5) and trailing edge (7); the vertical fin connecting rod (9) and the vertical fin (10). In this illustration, the flow interaction zone is particularly visible, comprising the bottom of the rotational base (3) and its flat top (12) and the top of the inverted "V" or positive dihedral aerofoil panel (26) and the inner limits of the front protection grid (16), the rear protection grid (18) and the fairing (17).

[0133] Another embodiment of the present disclosure is shown in Figure 5a. This figure shows a flow accelerator device installed at the top of a chimney (1), fixed by the base of the flow accelerator device (2). This embodiment has the particularity of making use of a different configuration of aerofoil panel, the inverted "V"-shaped or negative dihedral aerofoil panel (28), whose leading edge (5) and trailing edge (7) have an inverted "V" development. This configuration, as is the case with the embodiments of the present disclosure which make use of the positive "V"-shaped or positive dihedral inverted aerofoil panel (26) shown in Figures 4a, 4b, 4c, 4d and 4e, has advantages over the inverted aerofoil panel (6), because, due to its "V" configuration, it guarantees, within the same width of contact with the outside wind, a greater area of contact with it, which ensures a greater area for creating depressions, maximizing the suction capacity (and exhaust) achieved in the duct that ends immediately below. Also visible in Figure 5a is the duct outlet with inverted "V" cut termination (29). This component develops from the rotational base flat top (12) and its function is very similar to that of the V-shaped outlet (27) described in Figure 4b, i.e. to "shape" the flow of gases coming from the chimney (1) or any duct, to the shape of the aerofoilshaped panel that it overlaps and which enhances the flow acceleration phenomena that allow the upward flow coming from the chimney (1) or duct to be "swept". This duct outlet with an inverted "V" cut termination (29) can take on other configurationsthan the one illustrated, for example through shapes that make it conformal to the rotational base (3) (which modifies the flat top of the rotational base (12)), minimizing possible turbulence phenomena when the wind flow comes into contact with this nozzle and avoiding to turn a laminar flow regime into a turbulent flow regime. As with other embodiments of the present disclosure, the panel in the shape of an inverted "V"-shaped aerofoil or negative dihedral (28) is attached to the rotational base (3) by means of at least one aerofoil support (8). From this panel (or, alternatively, from the rotating base (3)) extends the vertical fin connecting rod (9) and the vertical fin (10), with the functions already described in the description of other embodiments.

[0134] Figure 5b illustrates another possible design for the flow accelerator device, consisting of an inverted "V"-shaped aerofoil or negative dihedral panel. In this embodiment, the confluence zone of the air flows coming from the duct and the wind passing underneath the inverted aerofoil is protected by a fairing (17) which protects the interaction zone of these flows, ensuring minimal interference in the phenomena of creating depressions and suction of the air flow coming from inside the duct and leaving it through the outlet (13) of the rotational base. This flow confluence zone is between the inverted "V"-shaped aerofoil or negative dihedral (28) panel and the rotational base flat top (12) and is circumscribed in the space between the fairing (17), the frontal protection grid (16), through which the wind flow is admitted, and the rear protection grid, through which the confluent flows exit. Also visible in Figure 5b are the base of the flow accelerator device (2); the rotational base (3); the leading edge (5) and trailing edge (7) of the inverted aerofoil; the vertical fin connecting rod (9) and the vertical fin (10).

[0135] Another view of the embodiment of the flow accelerator device illustrated in Figure 5b is shown in Figure 5c, which depicts the aforementioned embodiment from a three-dimensional perspective seen from below. This illustration shows the base of the flow accelerator device (2); the rotational base (3); the inverted "V"-shaped aerofoil or negative dihedral (28) panel; the leading edge (5); the trailing edge (7); the rotational base flat top (12); the fairing (17); the rear protection grid (18); the vertical fin connecting rod (9) and the vertical fin (10). Also visible is the Duct cross-sectionreduction part (i.e. the nozzle) (14) and its narrowing of the section (15). This part is fitted in the negative shape delimited by the outlet (13) of the rotational base.

[0136] Figure 5d shows a three-dimensional cross-sectional view of the embodiment of the flow accelerator device shown in Figures 5b and 5c, applied to the top of a chimney (1). Visible are the base of the flow accelerator device (2); the rotational base (3); the rotational axis of the rotational base (11); the rotational base flat top (12); the outlet (13) of the rotational base (13); the Duct cross-section reduction part (i.e. the nozzle) (14); the narrowing of the section (15); the frontal protection grid (16); the fairing (17); the rear protection grid (18); the inverted "V"-shaped or negative dihedral panel (28); its leading edge (5) and trailing edge (7); the vertical fin connecting rod (9) and the vertical fin (10). In this illustration, the flow interaction zone is clearly visible, comprising the bottom of the rotational base (3) and its flat top (12) and the top of the inverted "V"-shaped aerofoil or negative dihedral panel (28) and the inner limits of the frontal protection grid (16), the rear protection grid (18) and the fairing (17).

[0137] Figure 6 illustrates an application example of one of the embodiments flow accelerator device can assume. Here, this device consists of a flow accelerator device with single inverted aerofoil panel (33), which is positioned at the top of a fireplace (31) chimney (1). When the fireplace (31) is lit, the smoke circulating in its internal duct (32) is accelerated by the pressure differential provided by the Duct cross-section reduction part (i.e. the nozzle) (14) and the flow accelerator device with single inverted aerofoil panel (33), which improves the flow of smoke from the fireplace (31). The example is shown in three-dimensional perspective (i)); in cross-section in three-dimensional perspective (ii)) and in two-dimensional cross-section (iii)).

[0138] Figure 7 shows another example of another embodiment of the flow accelerator device, this time materialized in a flow accelerator device with an inverted "V"-shaped inverted aerofoil (34) panel. In this example, a ventilation duct (35), rectangular in section, which runs along the ceiling of any room in any building, has an extraction terminal which makes use of the present disclosure. The ventilation duct (35) terminal is connected by a Duct cross-section reduction part (i.e. the nozzle) (14) to a flow accelerator device with inverted "V"-shaped inverted aerofoil (34) panel. The combination of these two elements ((14) and (34)) causes negative pressuredifferentials that accelerate the flow of air circulating in the ventilation duct (35), ensuring its ventilation. It should be noted that the flow accelerator device with inverted V-shaped inverted aerofoil panel (34) is elevated by an installation tower (36) in relation to the height of the roof slab (37), giving it a higher position. This installation tower (36) appears as a way of increasing the height difference between the flow accelerator device with inverted "V" shaped inverted aerofoil panel (34) and the roof slab (37) in order to enhance the interaction of the wind with the device of the present disclosure, reducing interference that the slab may have with the wind flow, mainly deflection and drag phenomena caused by the wind.

[0139] Another embodiment of the flow accelerator device can be seen in Figure 8. This figure shows an exemplificative four-storey building (38) in which there is a ventilation system whose ventilation flows go somehow towards an inner central ventilation tower (39). At the top of this ventilation tower (39), and acting as a mean of extraction of the gas flows that move inside the forementioned ventilation tower (38), there is the flow accelerator device which, in this embodiment, is composed by a large single inverted aerofoil panel (41). It is placed on the top of a steady connection base to the flow accelerator device (40) that ensures the connection of the flow accelerator device to the ventilation tower (39) of the building. Due to the interaction with external wind, the already analysed phenomena responsible for the creation of depressions and for the exhaust of the gas flows coming from the ventilation tower, take place inside the confluence zone, below the inverted aerofoil panel, which the intake, protected by the frontal protection grid (16), allows the wind to enter. Just like the other shown embodiments, this flow accelerator device is able to rotate according to the wind direction at any time, given that the device can be correctly oriented due to its rotational axis of the rotational base (11) and can be driven by the fin of the large single inverted aerofoil panel (42). Due to the large scale of the embodiment, strategies of circular economy can be undertaken to produce the flow accelerator device. Parts of dismantled aircraft, like sections of the wings and winglets and fins can be used to make up the large single inverted aerofoil panel (41) and the fin of the large single inverted aerofoil panel (42), respectively. For the large single inverted aerofoil panel (41), sections of dismantled wind blades can also be incorporated.

[0140] In order to evaluate the performance of the flow accelerator device, a series of measurements and comparative simulations were carried out under conditions representative of natural and assisted ventilation in buildings. The experimental framework was defined so as to ensure equivalence with commonly used systems of the prior art and to allow a meaningful performance comparison.

[0141] The tests and simulations were conducted considering wind velocities between 2 m / s and 8 m / s, a vertical ventilation duct having a diameter of 2.00 m, and an internal conical duct section presenting a taper from 1% to 3% per floor. The temperature difference between the interior and exterior environments was set from 3°C to 7°C. The building configuration corresponded to a three-storey structure having an effective height of 7.5 m. The external aerodynamic element consisted of an aerofoil having a relative thickness of 15% and operating at an angle of attack of 8°. All scenarios were directly compared with ventilation systems widely used in the known state of the art and installed under equivalent boundary conditions.

[0142] For the purposes of comparison, three main categories of conventional extractors were analysed. A first category consisted of static roof extractors of the so-called "mushroom" type, comprising fixed elements without an aerodynamic profile. Such systems typically generate a pressure depression in the range of approximately 0.5 Pa to 1.2 Pa and provide naturally assisted airflow rates from about 40 m3 / h to 80 m3 / h, while exhibiting very limited responsiveness under low wind conditions. A second category comprised traditional vertical solar chimneys, which rely primarily on solar radiation to induce airflow. These systems typically generate pressure depressions from approximately 1 Pa to 3 Pa and airflow rates from about 70 m3 / h to 100 m3 / h, with performance strongly dependent on solar irradiation and significantly reduced during cloudy conditions or at night. A third category included rotary wind-driven extractors of the turbine type, which may generate pressure depressions from approximately 2 Pa to 4 Pa and airflow rates from about 80 m3 / h to 120 m3 / h, but which require regular maintenance, generate audible noise and vibrations, and show reduced effectiveness at wind speeds below approximately 3 m / s.

[0143] The comparative analysis demonstrates that none of the known passive solutions is capable of generating a pressure depression exceeding approximately 5 Pain a purely passive manner, operating efficiently at very low wind speeds, combining an aerofoil-type aerodynamic profile with an internal conical duct and a circular building geometry, maintaining directional stability without the use of motors, or achieving airflow rates comparable to those delivered by mechanical fans in the range of approximately 30 W to 60 W.

[0144] Measurements and simulations performed for the disclosed technology were based on realistic aerodynamic profiles, including NACA 4412, NACA 0015 and Clark-Y profiles, integrated with an internal conical duct and an external Venturi gap. The results demonstrate a substantial improvement in aerodynamic performance relative to the known state of the art.

[0145] For a wind speed of 4 m / s, the aerodynamic depression generated by the aerofoil alone reached values in the range of approximately 7 Pa to 9 Pa. At a wind speed of 6 m / s, the measured or simulated aerodynamic depression exceeded these values significantly, reaching levels that are between two and five times higher than those achieved by conventional rotary extractors under comparable conditions.

[0146] When considering the combined pressure depression resulting from the interaction of the chimney effect, the internal Venturi effect and the external aerodynamic effect, the total available pressure depression reaches unprecedented values for a passive system. By way of example, for a wind speed of 4 m / s in a three-storey building, the chimney effect contributes approximately 4 Pa to 6 Pa, the internal Venturi effect contributes approximately 0.05 Pa to 0.18 Pa, and the aerodynamic effect generated by the aerofoil contributes approximately 7 Pa to 9 Pa, resulting in a total combined depression that cannot be achieved by any known passive ventilation system.Table 1 - Measured / simulated flow rates.

[0147] The resulting airflow rates, that can be seen on Table 1, further highlight the technical advantages of the disclosed technology. Under minimum wind conditions of 2 m / s, the device provides a pressure depression of approximately 2 Pa to 3 Pa and an airflow rate between approximately 120 m3 / h and 150 m3 / h, thereby surpassing all reference systems of the prior art even at very low wind speeds. At a wind speed of 4 m / s, the available pressure depression increases to approximately 11 Pa to 15 Pa, corresponding to airflow rates of approximately 200 m3 / h to 230 m3 / h. At wind speeds of 6 m / s, the pressure depression exceeds 20 Pa and the airflow rate reaches approximately 260 m3 / h to 320 m3 / h. Under such conditions, the system operates with a performance comparable to that of a mechanical ventilation fan rated between approximately 30 W and 60 W, while consuming no electrical energy.Table 2 - Normalised comparison with the known state of the art.<

[0148] A normalised comparison with the known state of the art, as illustrated in Table 2, confirms these results. Conventional static extractors typically provide maximum pressure depressions of approximately 1 Pa to 2 Pa and airflow rates of 40 m3 / h to 80 m3 / h. Solar chimneys achieve depressions of up to approximately 3 Pa and airflow rates of up to approximately 110 m3 / h, with strong dependence on solar radiation. Rotary wind extractors achieve depressions of up to approximately 4 Pa and airflow rates of up to approximately 120 m3 / h, but perform poorly at low wind speeds and require moving parts. In contrast, the disclosed technology achieves pressure depressions in the range of approximately 15 Pa to 20 Pa and airflow rates between approximately 200 m3 / h and 320 m3 / h, while maintaining high efficiency at wind speeds below 3 m / s, requiring no solar radiation, operating without mandatory moving parts, generating very low noise levels, consuming no power, and exhibiting excellent adaptation to wind direction through passive stabilisation and optional rotation. The device is furthermore fully compatible with buildings of circular plan, in contrast with the limited or non-existent compatibility of the known solutions.

[0149] The experimental and comparative results clearly demonstrate that the disclosed technology generates between three and five times more pressure depression than passive extractors of the prior art, operates efficiently under very low wind conditions where conventional systems fail, and delivers airflow rates exceeding those of known systems by approximately 100% to 300%. The device enables a reduction in mechanical ventilation energy consumption of approximately 70% to 90%, a level not achieved by any existing passive device. The unique synergy between the three-dimensional aerofoil, the internal conical duct, the circular building geometry, the calibrated Venturi gap, the chimney effect and the passive omnidirectionalorientation produces a combined technical effect that is neither disclosed nor suggested in any known publication or patent.

[0150] The data therefore demonstrate that the device exhibits a surprising and non-obvious performance that would not be predictable for a person skilled in the art. No prior document teaches or suggests that an aerofoil positioned at a calibrated distance above a vertical duct could generate such high levels of static pressure depression, produce airflow rates comparable to electrically driven fans, operate efficiently at very low wind speeds, and maintain stable omnidirectional behaviour without the use of motors.

[0151] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0152] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above-described embodiments are combinable.

[0153] The following dependent claims further set out particular embodiments of the disclosure.

Claims

C L A I M S1. A flow accelerator device for enhancing ventilation or smoke extraction of a duct, comprising:an inverted aerofoil-shaped cross-section, formed by one or more panels, the one or more panels defining a leading edge, a trailing edge, an upper surface and a lower surface;wherein the leading edge, the trailing edge, and the one or more panels are configured such that the lower surface extends further than the upper surface; and wherein,the flow accelerator device is mechanically connected to a base that is fixed to an upstream of a duct, for generating a low-pressure therein to facilitate air extraction;wherein the inverted aerofoil-shaped cross-section comprises a camber from 2% to 4% of the chord length of the aerofoil cross-section and a relative thickness from 12% to 18% of said chord length;wherein the inverted aerofoil-shaped cross-section is positioned above a duct inlet at a vertical distance from 0.1 to 0.3 times of the duct diameter;wherein the inverted aerofoil-shaped cross-section is configured to operate at an angle of attack from 5° to 12° and within a Reynolds number range from 70,000 to 550,000 such that, when exposed to ambient wind of at least 2 m / s, the inverted aerofoil-shaped cross-section generates a pressure depression of at least 2 Pa at the duct inlet;the device being configured to cooperate with an internal duct geometry to enhance airflow extraction without electrical energy consumption, representing a passive solution and at least a 60% reduction in energy consumption.

2. The flow accelerator device according to the previous claim, wherein the inverted aerofoil-shaped cross-section has a geometry selected from one or a combination of at least two of the following geometries: straight, trapezoidal, elliptical, arrow, negative arrow, folded arrow, delta, folded delta, ogival or variable geometry.

3. The flow accelerator device according any of the previous claims, wherein at least a frontal section of the flow accelerator device develops in a shape or a combination of at least two of the following shapes: positive dihedral, negative dihedral, gull shape.

4. The flow accelerator device according any of the previous claims, further comprising an aerofoil support connecting the one or more panels of the flow accelerator device to the base.

5. The flow accelerator device according to any of the previous claims, further comprising a rotational base configured to allow articulated rotation of the flow accelerator device in a horizontal plane, for maintaining the leading edge perpendicular to a prevailing wind direction.

6. The flow accelerator device according to the previous claim, wherein the rotational base includes a flat top surface, for supporting the inverted aerofoil, having an outlet.

7. The flow accelerator device according to the previous claim, further comprising a nozzle fitted into the outlet of the flat top surface of the rotational base.

8. The flow accelerator device according to claims 6 or 7, wherein the outlet nozzle comprises a bended end.

9. The flow accelerator device according to the previous claim wherein the bended end further comprises a deflection flap for optimizing airflow direction.

10. The flow accelerator device according to any of the claims 6-9, wherein the outlet has an upward protruding "V" cut or inverted "V" cut termination.

11. The flow accelerator device according to any of the previous claims, further comprising at least one vertical fin for stabilizing the orientation of the flow accelerator device to the wind direction, optionally wherein the at least one fin isconnected to one or more panels of the flow accelerator device via a vertical fin connecting rod.

12. The flow accelerator device according to any of the previous claims, further comprising a fairing limited at a bottom by the rotational base and at a top by the one or more panels.

13. The flow accelerator device according the previous claim, wherein the fairing comprises frontal and rear openings, for allowing air flow, optionally further comprising a frontal protection grid and a rear protection.

14. Chimney, a fireplace, an installation tower and / or a ventilation tower, the flow accelerator device according to any of the preceding claims, for enhancing ventilation and / or smoke extraction.

15. Use of the flow accelerator device according to any of the preceding claims as an airflow enhancer for ventilation and / or smoke extraction in a building; namely residential houses, office and tourism buildings, or industrial facilities.

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