WO2000001576A2

WO2000001576A2 - A device for generating an aerodynamic force by differentially accelerating the fluid in the two sides of a surface

Info

Publication number: WO2000001576A2
Application number: PCT/BR1999/000057
Authority: WO
Inventors: Eduardo Bittencourt Sampaio
Original assignee: Eduardo Bittencourt Sampaio
Priority date: 1998-07-06
Filing date: 1999-07-05
Publication date: 2000-01-13
Also published as: AU4594999A; WO2000001576A3; BR9806466A

Abstract

The present invention refers to a device which accelerates the fluid (in which the device is immersed) differentially immediately below and immediately above a surface (1). This acceleration can be obtained through a convergent/divergent channel, resulting in a greater fluid velocity in one of the faces of the surface. As greater speeds means lower pressures, there is a resulting force acting upon the surface. This force can be used to lift airplanes, helicopters, autogyros, or other aircraft in the air. Also it can be used to power sailboats, being a suitable replacing for the traditional sails. The convergent and divergent channels can assume several configurations, the two main categories being: a convergent (or divergent) channel in which the convergence occurs in the cross-sectional plane; and a convergent (or divergent) channel in which the convergence occurs in the horizontal plane, thus requiring a 3D geometry to represent the device. The former is illustrated in figures 1-5, while the later in figures 7-12. The concept object of this invention can also be used to design an aerodynamic brake, in which the low pressure jet stream leaving the convergent channel (11) can be blown over the top of the structure (12), thus increasing the drag force.

Description

Title: "A DEVICE FOR GENERATING AN AERODYNAMIC FORCE BY DIFFERENTIALLY ACCELERATING THE FLUID IN THE TWO SIDES OF A SURFACE".

Field ol tne invention:

The present invention refers to an aerodynamic device and effects on moving bodies on the atmosphere through which they move. More particularly the invention refers to a device on which air (or any fluid) is accelerated over one of the faces of a lifting surface, by means of a convergent or divergent channel. Being the air at different velocities above and bellow the said surface, a differential pressure is generated, thus resulting in an aerodynamic force.

Background of the Invention:

An example of an aerodynamic device of the prior art, which produces an aerodynamic force as a result of its movement, is a common airfoil, which is used as the cross section of most aircraft wings. Although many configurations have been studied through the years, the corresponding lift coefficients are always limited to relatively small values. Therefore in order to generate enough lift to sustain an aircraft in the air, either a lot of wing area or greater speed are needed. Whilst the former has structural and weight disadvantages, the later requires more runaway for take off and landing. The objective of this invention is to suggest a new concept for aerodynamic devices so that larger lift coefficients (even at the cost of greater drag) can be obtained, allowing the use of either shorter runaways or lower operational speeds for the aircraft.

Helicopters also would take advantage of the present invention since it would require either shorter rotor blades or lower rotational speeds.

In another field of application, a sailboat uses the air speed to generate an aerodynamic force, which is the responsible for the boat movement. If greater lift coefficients are achieved, less area and consequently smaller mast can be used to generate the same propulsion force. The smaller height of the proposed device compared to presently used sail-mast assembly would result in less momentum for the same force generated, which would significantly reduce the pitch movements of the boat.

Summary of the Invention:

The present invention refers to a device which accelerates the fluid (in which the device is immersed) differentially immediately bellow and immediately above a surface.

This acceleration can be obtained through a convergent/divergent channel, resulting in a greater fluid velocity in one of the faces of the surface. As greater speeds means lower pressures, there is a resulting force acting upon the surface.

For a better understanding of the present device, consider the simplest device using this concept, which consists of a convergent channel which accelerates the fluid flowing immediately above a lifting surface, under which free stream is allowed to flow (without any alteration in its speed). Roughly, if the convergent channel is designed to change the fluid speed by a factor of three, we would have a dynamic pressure of -p.(3.v)²/2 in the upper face of the surface and a dynamic pressure of -

in the lower face, thus resulting in a lift coefficient equal to 8, which is much bigger then those obtainable with common airfoils. Generally speaking, if we manage to design a channel capable of accelerate the fluid by a factor K, and this accelerated fluid is let to flow over a surface under which the fluid speed is not altered, we theoretically obtain a lift coefficient equal to (K² - 1), as can be easily verified.

Unfortunately there are practical limitation to the factor K that can be obtained, and to the area over which this factor can be sustained, since the fluid lose velocity and disperse as it moves away from the channel output.

In another embodiment, the channel is convergent in the horizontal plane. In this case, however, the area over which the fluid is accelerated is smaller than that of the first embodiment proposed. We still have a lift force, since the decrease in pressure in one face is dependent on the square of the acceleration factor (K²) while the decrease in area is proportional to K.

With these and other objects in view, which will become apparent to one skilled in the art as the description proceeds and more particularly defined in the attached claims, the device will be described with reference to accompanying drawings. Brief Description of the Drawings:

The accompanying drawings illustrate embodiments of the invention in which:

- figure 1 is a cross section of one possible embodiment showing the main components of the device, these being the convergent channel - formed by the upper element and the front part of the lower element - and the surface over which the fluid at higher speed (or lower pressure) is blown - formed by the rear part of the lower element - thus originating a lift force;

- figure 2 is a cross section of another embodiment showing the divergent channel - formed by the lower element and the front part of the upper element - and the surface under which the fluid at lower speed is blown - formed by the rear part of the upper element - again originating a lift force;

- figure 3 is a cross section of still another embodiment showing a combination of a convergent channel which blows high speed fluid at the upper side of the surface (main element) and a divergent channel which blows low speed fluid at the lower side of the said surface, thus originating a lift force;

- figure 4 is a cross section of another embodiment in which the upper element forming the convergent channel is a leading edge of a common airfoil;

- figure 5 is a cross section of a similar embodiment in which successive convergent channels are used to increase the useful area of the surface by accelerating the fluid as it tends to disperse and lose speed downstream;

- figure 6 is a perspective view illustrating how the cross section shown in figure 4 could be used in autogyros (or gyroplanes);

- figure 7 is a top view of another embodiment showing a different configuration for the converging channel - the convergence now lies in another plane (the horizontal plane). In this figure several convergent channels are formed between symmetrical airfoils, which are mounted over the lifting surface (which can be either a plane or have an airfoil shape to still increase the lift force);

- figure 8 is a perspective view of the same device illustrated in figure 7; - figure 9 is a top view of an embodiment similar to the one shown in figure 7, but using asymmetrical airfoils instead. In this figure, just one convergent channel is illustrated;

- figure 10 is a perspective view of the same device illustrated in figure 9;

- figure 11 is a top view of an embodiment in which asymmetrical airfoils are used to form several alternating convergent divergent channels. Note that for the convergent channels, the surface on which the differential pressure is impressed is located on the under side, while for the divergent channels, on the upper side;

- figure 12 is a perspective view of the same device illustrated in figure 11;

- figure 13 is a cross section of a device in which the concept is used to generate a drag force, rather than a lift force. This is an interesting application of the invention in the design of parachutes and aerodynamic brakes;

Detailed Description of the Invention:

For a better understanding of the present invention, a detailed description thereof is now made, with reference to the accompanying drawings.

One embodiment of the aerodynamic device is shown in figure 1. The device comprises a main (lower) element 1 and an upper element 2. The front part (leading edge) of the lower element 1 and the upper element 2 form a convergent channel, in which the fluid is accelerated. As it gains speed it lose pressure according to Bernoulli's law. Since this accelerated (low pressure fluid) is blown over the surface (formed by the rear part of 1) while nothing is done with the fluid blown under the said surface (thus preserving the same far field pressure), a differential pressure is generated thus giving rise to a lift force. If the fluid speed at the channel output is greater than the far field speed by a factor of K, the differential pressure is expect to be (K² - 1). .v²^. The factor K does not remain the same over the whole surface, since the fluid disperse and lose velocity downstream. Although a closed formula for the lift coefficient is difficult to achieve, the above explained give us a rough order estimation of what can be expected.

Another embodiment of the device is shown in figure 2. Instead of a convergent channel, this embodiment uses a divergent channel formed by the lower element 3 and the front part (leading edge) of the main (upper) element 1. The retarded fluid (negative acceleration) is blown under the surface (formed by the rear part of 1). Since this retarded fluid is at high pressure, a lift force is generated which acts on the surface. The rough order calculations remain the same as in above paragraph, but the K factor is now lower than 1 and the force still is in the upward direction.

The embodiment of figure 3 shows a device using a combination of a divergent and a convergent channel, as explained in the above paragraphs. A high-speed (low-pressure) fluid is blown over the main element 1, while a low speed (high-pressure) fluid is blown under the main element The convergent channel is formed by the front part of the main element 1 and the upper element 2, while the former and the lower element 3 form the divergent channel.

Figure 4 illustrates one embodiment in which the upper element 2 forming the convergent channel is a leading edge of a common airfoil. An increase in drag is expected in this configuration, since a wake is formed behind the upper element 2.

In all the embodiments shown in this document, successive (cascaded) channels may be applied, in order to avoid dispersion of the fluid as it moves away from the first channel. In this sense, at some distance behind the first channel, another one could be used to accelerate again the fluid, increasing the effectively used area of the surface (main element). Behind mis second channel, another one could be used and so on.

Figure 5 illustrates the above explained, applied to the device of figure 4. The successive channels are formed by the elements 2 and the main surface 1.

Although the device illustrated in figure 4 has an increased drag force comparatively to other devices, it may be used with success in autogyros, since it presents a much bigger drag when the fluid reaches the back of the upper element 2 than when it reaches its front. Figure 6 illustrates one application of this invention in autogyros. A rotation free structure is formed by blades 2 (with cross section identical to that of the upper element shown in figure 4) which are fixed on the central axis 4, this axis being free to rotate relatively to the main surface 1. Since the drag impressed on the blades depends on the direction of the air speed relatively to the blades, when a fluid (air) is moving in relation to the device, the blades tends to rotate, which, accordingly to what has been explained throughout this document, generates lift. This is similar to what happens with common blade autogyro, where the air speed gives the blades a rotational movement, thus generating a lift force.

Figure 7 and 8 illustrate another embodiment showing a different configuration for the converging channel - the convergence now lies in another plane (the horizontal plane). In this figure several convergent channels are formed between symmetrical airfoils 5, which are mounted over the lining surtace 1 (which can be either a plane or have an airfoil shape to still increase the lift force). Although the effective area (over which the fluid is accelerated) has decreased, we still have a resultant lift, since the decrease in the dynamic pressure at the upper face of the surface depends on the square of the K factor, while the decrease in area is proportional to K.

Figure 9 and 10 illustrate an embodiment similar to the one shown in figure 7, but using asymmetrical airfoils 6 instead. As asymmetrical airfoils were used, it is impossible to have two or more adjacent convergent channel, as before (with symmetrical airfoil).

This has motivated the solution shown in figure 11 and 12. In this embodiment asymmetrical airfoils 6 are used to form several alternating convergent/divergent channels.

Note that for the convergent channels 7, the surface 8 on which the differential pressure is impressed is located on the under side, while for the divergent channels 9, the surface 10 is on the upper side.

An interesting application of the invention in the design of parachutes and aerodynamic brakes is shown in figure 13. Here the concept is used to generate a drag force, rather than a lift force. After passing through the convergent channel 11, the accelerated fluid (low pressure) is blown over the top of the main structure of the parachute 12. The convergent channel is formed by the main element (12) and the top element (13). Others elements 14 can be used to form successive channels, for the same reasons explained before.

Claims

1. Aerodynamic lift generator, comprising a convergent channel formed by the front part of a main element (1) and an upper element (2), and a surface over which the pressure differential develops (I ).

2. Aerodynamic lift generator, comprising a divergent channel formed by the front part of a main element (1) and a lower element (3), and a surface over which the pressure differential develops (1).

3. Aerodynamic lift generator, comprising a convergent channel (formed by the front part of a main element (1) and an upper element (2)), a divergent channel (formed by the front part of a main element (1) and a lower element (3)), and a surface over which the pressure differential develops (1).

4. Aerodynamic lift generator in accordance with claim 1, in which the upper element has a common airfoil leading edge shape, as in figure 4.

5. Aerodynamic lift generator in accordance with claim 1, 2, 3, and 4, in which successive elements (2) are used to form several (cascaded) channels.

6. Aerodynamic lift generator comprising a rotation free structure formed by blades (2) (with cross section in accordance to claims 1, 2, 3, or 4) which are fixed on the central axis (4), this axis being free to rotate relatively to the main surface (1).

7. Aerodynamic lift generator, in which the convergent channel is formed by symmetrical airfoils (5) mounted perpendicularly the surface (1), in such a way that the convergence now lies in the horizontal plane, as shown in figure 7.

8. Aerodynamic lift generator in accordance with claim 7, in which asymmetrical airfoils (6) are used to form the convergent channel.

9. Aerodynamic lift generator, in which alternating convergent (7) / divergent (9) channels are used, as shown in fiaure 11. and 12.

10. Aerodynamic brake, in which a convergent channel (11) formed by the main element (12) and a top element (13) accelerates the fluid (air) and blows this high speed fluid over the top of the device (12), over which successive convergent channels (cascaded) may be formed by several top elements (14).