EP3722605A1 - Fluid flow generator - Google Patents

Abstract

The application relates to a flow generator (1), comprising a housing (2) which encloses a cavity (3) for receiving a fluid, a nozzle opening (4) through which the cavity (3) is in fluid communication with an outer space (5) of the housing (2) is located, a deformable membrane (6) and an actuator (7), having at least one actuator segment, the actuator (7) being set up to deform the membrane (6) in such a way that a through the nozzle opening (4) flowing flow of the fluid from the cavity (3) into the outer space (5) or from the outer space (5) into the cavity (3) is generated. A complete outline of the actuator (7) comprises at least two discrete outlines of the at least one actuator segment.

Description

The application relates to a flow generator.

Flow generators are known from the prior art, by means of which flows can be generated in a surrounding fluid by enlarging or reducing a cavity. If a volume flow through a certain cross-section, for example the cross-section of a nozzle opening, is periodic or at any rate variable over time, but the mean value of the volume flow through the cross-section is zero, then the flow generator is also referred to as a synthetic jet actuator (SJA).

When using flow generators, it is often desirable to generate the largest possible volume flows and / or flow velocities. For example, SJAs can be used to influence flows in the In the vicinity of wings, rotors and other air-conducting elements of vehicles, wind turbines, etc., for cooling electronic or electrical components or for propulsion. For such applications, high volume flows and / or flow velocities are necessary. Furthermore, a cost-saving design of the flow generator and suitability for low-wear operation and a long service life are important.

The present patent application is therefore based on the task of proposing a flow generator with the properties mentioned.

Accordingly, a flow generator with the features of claim 1 is proposed. Preferred embodiments and further developments result from the features of the subclaims.

A flow generator of the proposed type comprises a housing which encloses a cavity for receiving a fluid, a nozzle opening through which the cavity is in fluid communication with an exterior of the housing, a deformable membrane and an actuator having at least one actuator segment. The actuator is designed to deform the membrane in such a way that a flow of the fluid flowing through the nozzle opening from the cavity into the outer space or from the outer space into the cavity is generated. A complete outline of the actuator comprises at least two discrete outlines of the at least one actuator segment.

Each actuator segment is or comprises a segment consisting of a continuous material area. Each of the actuator segments is set up so that an electrical voltage can be applied to the actuator segment to generate a force acting on the membrane. Outside each actuator segment or between each two actuator segments, a material from which the continuous material areas of the actuator segments are made is interrupted. There may be gaps between the actuator segments. The gaps can, but need not, be completely or partially filled with another material. The actuator segments can, however, also adjoin one another.

The complete outline of the actuator can be defined as one or more outlines of a projection of the actuator onto the membrane, the outlines comprising projections of each of the actuator segments onto the membrane and running wherever the projections of the continuous material areas of the actuator segments end on the membrane.

A discrete contour line can be understood to be a contour line that is closed, that is to say begins at a point on the contour line and ends at the same point, and does not cross itself or intersect or touch itself.

A complete contour of the actuator comprising at least two discrete contour lines of one or more of the actuator segments can thus be given, for example, by the fact that the actuator has two or more actuator segments arranged in a planar manner next to one another. Each of the actuator segments then contributes a discrete outline to the complete outline.

An actuator that has several actuator segments - hereinafter also referred to as a segmented actuator - can have the advantage that an actuator with a larger area and / or a lower resonance frequency can be produced than would be possible with an actuator that only has one Has actuator segment - hereinafter also referred to as a continuous actuator. A larger membrane can thus be deformed accordingly and / or a larger deflection of the membrane can be achieved, which can lead to a larger volume flow and / or a larger flow velocity. Mechanical stresses, which in the long term can lead to cracks and / or breaks in the actuator, for example, are also reduced, which reduces wear and tear and increases the service life and maintenance intervals. Furthermore, a segmented actuator of a given area can be manufactured more cheaply and more simply than a continuous actuator.

At least one of the actuator segments can have at least one central recess. Such an actuator segment then has at least two discrete contour lines, one of which runs on an outer edge of a projection of the actuator segment and at least one on an edge of the at least one central recess. The at least one central recess can, but need not, be arranged centrally in the at least one actuator segment. A special case of such an actuator is an actuator with exactly one actuator segment which has exactly one central recess; In this special case too, the actuator segment (and thus the actuator) has two discrete contours.

Such an actuator can have the advantage over an actuator whose actuator segments do not have central cutouts that the resonance frequency can also be reduced in this way and / or the membrane deflection can be increased, which in turn can lead to higher volume flows and / or flow velocities. In this case, too, there may be reduced wear and tear and an increased service life and / or maintenance intervals.

At least one of the actuator segments can be a piezo element. Such an actuator segment can consist of a piezoelectric, for example a ceramic piezoelectric. Since such piezoelectrics are often susceptible to fractures and / or cracks as a result of mechanical stresses and since large-area piezoelectric actuator segments cannot be produced, or can only be produced with considerable effort and expense, the advantages mentioned above are clearly evident. Other types of actuator segments are also possible, for example electrodynamic or electrostatic actuator segments or actuator segments consisting of a shape memory alloy, for which the above-mentioned advantages can also apply.

At least one of the actuator segments can be circular, circular, elliptical, triangular, trapezoidal, rectangular, square, circular segment-shaped or circular ring segment-shaped. With such shapes of the actuator segments, different shapes of the actuator can be realized which implement the above-mentioned advantages of segmented actuators or of actuator segments with a central recess, and / or which are advantageously adapted to the shape of the membrane.

The actuator can have at least two actuator segments and / or, for example, a maximum of thirty actuator segments. This shows the advantages realize a segmented actuator with a comparatively low complexity of the arrangement. Alternatively, the actuator can of course also have only one or even more than thirty actuator segments - with the corresponding advantages of particularly low complexity or particularly large possible area.

The actuator can have a diameter and / or a side length of at least 35 mm, preferably at least 80 mm, and / or an area of at least 9 cm ² , preferably at least 50 cm ² , and / or a thickness of at most 1 mm, preferably at most 0 .5 mm. Correspondingly large volume flows and / or flow velocities can be achieved with appropriately dimensioned actuators, which can be implemented with the features described above. Of course, the actuator can also be smaller than the dimensions mentioned, which enables a particularly cost-effective and low-wear design with improved performance compared to actuators of the same size according to the prior art.

The fluid flowing through the nozzle opening when the membrane is deformed can have a volume of at least 0.45 cm ³ . Such deformation volumes and / or volume flows and / or flow velocities can be advantageous for a wide variety of uses of the flow generator, for example for influencing flow, cooling or driving.

The deformable membrane can be designed to be deformable in alternating directions with a frequency between 10 Hz and 10 kHz, preferably between 500 Hz and 2 kHz. An alternating deformation of the membrane with frequencies in this or also another range can enable a continuous generation of the flow. The deformable membrane can also be designed to be deformed with a variably adjustable frequency, whereby a variable adjustment of the volume flow and / or the flow velocity which is advantageous for applications can be possible.

The frequency can be a resonance frequency of the actuator and / or the membrane and / or a resonator formed by the flow generator. By operating the actuator at the resonance frequency, a maximum deflection with the corresponding advantages of a maximum volume flow and / or a maximum flow velocity can be achieved, with the resonance frequency in the case of the flow generator described here being particularly low, which entails the further advantages described above can bring.

The nozzle opening can be arranged on a side surface of the housing which is arranged perpendicularly or almost perpendicularly to the membrane. Such an arrangement of the nozzle opening can make it possible, for example, to arrange several flow generators in a space-saving manner with nozzle openings lying close to one another, which enables, for example, an advantageous generation of the flow with few gaps and / or a high total volume flow.

The nozzle opening can, however, also be arranged on a cover surface of the housing opposite the membrane. With such an arrangement, for example, a diameter of the nozzle opening can be selected with great flexibility.

The flow generator can be set up so that a liquid, in particular water or oil or a cooling liquid, can be used as the fluid. Thus, the flow generator can be used particularly advantageously for cooling, driving or influencing flows in liquids, for example in the vicinity of surfaces or flow-guiding elements of watercraft.

Additionally or alternatively, the flow generator can be set up so that a gas, in particular air, can be used as the fluid. The flow generator can thus be used particularly advantageously, for example, for influencing flows in gases, for example in the vicinity of wings, rotors and other surfaces or air-conducting elements of aircraft or wind turbines or surfaces of land vehicles.

• Fig. 1 einen Querschnitt durch einen Strömungserzeuger der beschriebenen Art,
• Fig. 2 eine Aufsicht der Membran und des Aktors des in Fig. 1 gezeigten Strömungserzeugers,
• Fig. 3 eine Aufsicht der Membran und des Aktors einer weiteren Ausführungsform eines Strömungserzeugers.

Exemplary embodiments are described below with reference to FIGS. 1 to 3 explained. They show, each in schematic form,

• Fig. 1 a cross section through a flow generator of the type described,
• Fig. 2 a plan view of the membrane and the actuator of the in Fig. 1 shown flow generator,
• Fig. 3 a plan view of the membrane and the actuator of a further embodiment of a flow generator.

The in Fig. 1 The flow generator 1 shown comprises a housing 2 which encloses a cavity 3 for receiving a fluid. The housing 2 consists of a thermosetting polymer, but can also consist of a different material, for example a metal. The housing 2 is made of one part, but can be composed of several individually manufactured parts.

The cavity 3 has approximately the shape of a flat cylinder, with a top surface 11 of the cylinder bulging in the shape of a dome. However, the cavity 3 can also have other shapes, for example the shape of a flat cuboid.

A deformable membrane 6 is arranged in the cavity 3 opposite the top surface 11. According to the shape of the cavity 3, the membrane 6 is round. The membrane 6 can, however, also have other shapes, for example it can be rectangular or square. The membrane 6 consists of a polymer, other materials also being possible as an alternative, such as metals, metal alloys or ceramics.

The membrane is attached in a form-fitting manner on its outer circumference by a circumferential recess in the housing 2. The membrane can, however, also be mounted in a fixed or flexible manner in another way, for example it can be fastened in a force-locking manner by clamping several housing parts onto one another.

On the circumferential side surface 10, that is, between the top surface 11 and the Diaphragm 6 is arranged a nozzle opening 4 which is arranged perpendicular to the diaphragm 6 and which passes through the wall of the housing 2. The cavity 3 is in fluid communication with an outer space 5 of the housing through the nozzle opening 4. The nozzle opening 4 can also be arranged at other points of the housing 2, for example on the cover surface 11 arranged opposite the membrane 6. The nozzle opening 4 has a cylindrical shape, but can also be shaped differently, for example conical or cuboid.

Furthermore, the flow generator 1 comprises an actuator 7, set up to deform the membrane 6 in such a way that a flow of the fluid flowing through the nozzle opening 4 is generated from the cavity 3 into the outer space 5 or from the outer space 5 into the cavity 3.

As in Fig. 2 shown, the actuator 7 is formed from an actuator segment 8 which is connected to the membrane 6 over a large area. The connection can be established, for example, by gluing, soldering or by means of one or more connecting elements. The actuator segment 8 is a piezo element consisting of a ceramic piezoelectric which is deformed when a voltage is applied in such a way that a force acts on the membrane 6 that is suitable for deforming the membrane 6. Alternatively, the actuator segment 8 can also be a different type of actuator segment, for example an electrodynamic or electrostatic actuator or a shape memory alloy.

The actuator segment 8 is embodied in the shape of a circular ring, that is to say as a circular element with a circular central recess 12 which is arranged in the center of the actuator segment 8. The actuator segment 8 can also have a different shape, for example it can be elliptical, rectangular or square. The recess 12 can also have a different shape, for example an elliptical, rectangular or square shape, and / or be arranged off-center. The actuator segment 8 can also have several recesses 12.

Due to the circular design of the actuator segment 8 with the central recess 12, a complete outline of the actuator 7 comprises two discrete outlines 9 and 9 'of the actuator segment 8, the outline 9 being given by an outer outline of the actuator segment 8 and the outline 9' by an inner outline of the actuator segment 8, i.e. an outline of the recess 12.

The actuator segment 8 shown can, for example, have a thickness of 0.2 mm and a diameter of 50 mm, the central recess 12 a diameter of 10 mm, which corresponds to an area of the actuator of approximately 18.0 cm ² . Other thicknesses, diameters and surfaces are also possible.

The deformable membrane 6 can be designed to be deformable in alternating directions with a frequency of, for example, approximately 1.5 kHz, which can be a resonance frequency, and a flow velocity of approximately 120 m / s with a nozzle area of, for example, 7 mm ² produce. Depending on the possible variations of different dimensions and properties, other performance characteristics can of course also be achieved, for example lower or higher frequencies or flow velocities.

The actuator 7 of a further example of a flow generator 1 has - as in FIG Fig. 3 shown - eight actuator segments 8, which are planar arranged next to each other and connected to the membrane 6 flat. The actuator segments 8 are designed in the shape of a circular ring segment and together result in a circular ring which is interrupted in areas between the actuator segments 8. The actuator segments 8 can also be shaped differently, for example circular, triangular, trapezoidal or circular segment-shaped. Individual actuator segments 8 can also have different shapes and / or can be combined in the most varied of ways to form an overall shape. As mentioned above, other types of actuator segments besides piezo elements are also possible.

Due to the segmented design of the actuator 7 with the eight actuator segments 8, a complete outline of the actuator 7 comprises eight discrete outlines 9, 9 'etc. of the actuator segments 8, the outline 9 being given by an outer outline of a first actuator segment 8, the outline 9 'Given by an outer contour line of a second actuator segment 8 is etc.

The actuator 7 can also have a different number of actuator segments 8, for example at least three and / or at most thirty actuator segments 8, or only two or more than thirty actuator segments 8.

The circular ring approximately formed by the circular ring segment-shaped actuator segments 8 can, for example, have a thickness of 0.2 mm and a diameter of 100 mm, the central recess 12 a diameter of 20 mm, which corresponds to an area of the actuator of approximately 75.4 cm ² . Other thicknesses, diameters and surfaces are also possible.

The deformable membrane 6 can be designed to be deformable in alternating directions at a frequency of, for example, approximately 500 Hz, which can be a resonance frequency, and to generate a flow velocity of over 100 m / s, for example. Depending on the possible variations of different dimensions and properties, other performance characteristics can also be achieved, for example lower or higher frequencies or flow velocities.

Due to the design and materials of the flow generator 1 shown and described by way of example, a liquid, in particular water, oil or a cooling liquid, or a gas, in particular air, can be used as the fluid.

List of reference symbols

1

Flow generator

2

casing

3

cavity

4th

Nozzle opening

5

Outside space

6th

Deformable membrane

7th

Actuator

8th

Actuator segment

9.9 '

Outlines

10, 10 '

Side face

10 '

Side face

11, 11 '

Top surface

12

Recess

Claims (11)

Flow generator (1), comprising
a housing (2) which encloses a cavity (3) for receiving a fluid,
a nozzle opening (4) through which the cavity (3) is in fluid communication with an outer space (5) of the housing (2),
a deformable membrane (6) and
an actuator (7) having at least one actuator segment (8), the actuator (7) being designed to deform the membrane (6) in such a way that a flow of the fluid flowing through the nozzle opening (4) out of the cavity (3) into the outer space (5) or from the outer space (5) into the cavity (3) is generated,
characterized by
that a complete outline of the actuator (7) comprises at least two discrete contour lines (9, 9 ') of the at least one actuator segment (8). Flow generator (1) according to claim 1, wherein at least one of the actuator segments (8) has at least one central recess (12). Flow generator (1) according to one of the preceding claims, wherein the actuator (7) has at least two actuator segments (8) arranged in planar side by side. Flow generator (1) according to one of the preceding claims, wherein at least one of the actuator segments (8) is circular, circular, elliptical, triangular, trapezoidal, rectangular, square, circular segment or circular ring segment. Flow generator (1) according to one of the preceding claims, wherein at least one of the actuator segments (8) is a piezo element. Flow generator (1) according to one of the preceding claims, wherein the actuator (7) has at least two actuator segments (8) and / or at most thirty actuator segments (8) and / or more than thirty actuator segments (8). Flow generator (1) according to one of the preceding claims, wherein the actuator (7) has a diameter and / or a side length of at least 35 mm and / or an area of at least 9 cm ² and / or a thickness of at most 1 mm. Flow generator (1) according to one of the preceding claims, wherein the fluid flowing through the nozzle opening (4) when the membrane (6) is deformed has a volume of at least 0.45 cm ³ . Actuator (1) according to one of the preceding claims, wherein the deformable membrane is set up to be deformable in alternating directions with a frequency between 10 Hz and 10 kHz. The flow generator (1) according to any one of the preceding claims, wherein the nozzle opening (4) is located on a side surface (10) of the housing (2) that is perpendicular or almost perpendicular to the membrane (6) or on a top surface (11) opposite the membrane (6) ) of the housing (2) is arranged. Flow generator (1) according to one of the preceding claims, set up so that a liquid, in particular water or oil or a cooling liquid, can be used as the fluid and / or set up so that a gas, in particular air, can be used as the fluid.

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