SE434977B - An apparatus for increasing the flow speed of a liquid or gaseous medium - Google Patents

Abstract

An apparatus for increasing the flow speed of a liquid or gaseous medium such as water or air and for recovering the kinetic energy of the medium therefrom, consisting of a series of concentrically outside each other and substantially symmetrically arranged annular members separated by slots, whereby said members in the direction from the outside towards the longitudinal axis of the apparatus, which coincides with the flow direction of the medium, have successively and substantially symmetrically decreasing dimensions in the direction of the longitudinal axis for the formation of an inlet opening acting as an accelerator for the medium with annular slots for removal of turbulent medium from the inlet opening, and for the formation of an outlet opening acting as a diffuser for the medium, wherein said annular members are successively thinner for the formation of sharp edges directed outwards from the longitudinal axis of the apparatus; the kinetic energy of the medium is recovered by a propeller or a turbine, placed coaxially with the longitudinal axis, in the central part of the apparatus. <IMAGE>

Description

_.._., -_-..._, ._. ._. .V 7900241-6 2 'to extract wind energy in an economical way when the wind speed is less than a value of approximately 5 m / second.

Since the average wind speed is usually estimated at 5 - 7 m / second, there are long periods of time when no wind power can be extracted at all.

There is thus a need for a device with which one can increase the wind speed in such a way that an economical extraction of the kinetic energy of the wind is made possible. An improved device for this purpose is provided according to the present invention.

Theoretical calculations for the extraction of wind power have been performed by Betz, who set up the following formula for the extractable power (P): P = x S x A x W3 x C NIH where 9 denotes the density of the air, A denotes the cross-sectional area of the air flow, W denotes the wind speed and C is a constant, which indicates the part of the wind energy that can be converted to axial power in a generator. It appears from this formula that the removable power is directly proportional to the cube on the wind speed.

The formula clearly shows that an increase in wind speed is particularly important for achieving a maximum increase in the extractable power.

The invention thus relates to an improved device with the aid of which one can increase the air velocity while reducing the cross-sectional area of the flowing air. Theoretically, according to the invention, one can increase the air velocity from a low velocity, e.g. 4 m / second, at a very high speed, for example up to 300 m / second.

The present invention is a further development of the invention described in the patent ... (p. 7801112-9). The device described in the patent relates only to an accelerator, i.e. a device in which a flowing medium such as wind is concentrated while increasing the velocity of the medium. According to the present invention, such an accelerator is combined with a so-called so-called accelerator. In the present context, diffuser means a device which allows the air (medium) passed through a propeller placed after the accelerator to obtain as large an undisturbed expansion volume as possible. In order to improve the properties of the diffuser, according to the invention the air (medium) which has passed through the turbulence diverting channels described in the above-mentioned patent is used, which can thus have a higher energy than the surrounding medium, so that in the flow direction after the propeller a relatively large volume with lower pressure. In normal cases, with a stand-alone propeller, a so-called awake of smaller dimensions. If only one diffuser is used in connection with a propeller, said wake can be improved somewhat in relation to a free propeller. At maximum, the diffuser angle with air as medium can be made to amount to about 7 ° before the air flow releases from the walls of the diffuser. When this happens, a drastic reduction in the removable effect occurs.

According to the present invention, the diffuser angle can be significantly increased without the air flow "releasing".

The device according to the invention is described in more detail with reference to the accompanying drawings, in which figure 1 shows a cross section through a device according to the invention and figure 2 shows a cross section of a modified embodiment of the device according to the invention.

The accelerator / diffuser according to the invention has circular cross-sections everywhere and, as mentioned above, the drawing figures show a section through the center of the device, ie. along its longitudinal axis.

The device shown in Figure 1 consists of a series of concentrically superimposed substantially symmetrically superimposed annular elements 1-4, which also have columns 5-7. elements 1-4 have, in the direction from the outside towards the longitudinal axis of the device, which coincides with the flow direction of the medium, successively and substantially symmetrically decreasing dimensions in the direction of the longitudinal axis to form a substantially conical inlet opening 8 acting as an accelerator for the medium, wherein the annular elements have rounded, aerodynamically shaped leading edges with intermediate annular slots for discharging turbulent medium from the inlet opening and for forming an outlet opening 9 acting as a diffuser for the medium, wherein the annular elements are thinned into aerodynamically shaped tips directed outwards from the longitudinal axis intermediate annular gaps flowing medium. The kinetic energy of the flowing medium is recovered using one or more propellers or turbines 10 located coaxially with the longitudinal axis in the central part of the device.

The device according to the invention thus constitutes a combination of an accelerator and a diffuser. The part facing the wind (medium) is formed with rounded profiles on the annular elements and the gaps located between them divert the turbulent air formed at the various stages of acceleration and friction towards the rounded profiles. The wind speed is thus built up step by step and largely corresponds to the stepwise decreasing area around the center line.

The diffuser is substantially designed as a cone with the tip against the smallest cross-sectional area of the accelerator and its function is to allow expansion of the medium after its passage of the propeller or turbine. The turbulent air which is separated in the accelerator part through the slit openings has, despite its turbulence, a higher energy than the surrounding medium and this air is passed through the slits to the diffuser part according to the invention, where it is given a radially outward movement to increase wake and propeller. as large an expansion space as possible.

The air passing through the device receives in the diffuser part a rotation due to the action of the propeller and an improved power of the device can be obtained by providing the slots 5-7 with screen means (not shown), which give it through the gaps flowing the air a rotation which coincides with and thereby amplifies the rotation which the air has obtained after passage of the propeller, whereby an amplified diffuser effect is obtained (so-called drum effect).

Figure 2 shows a modification of the device shown in figure 1 and this is characterized in that it has in the passage path of the medium or air a central body 11 with circular cross-sections, the longitudinal axis of which coincides with the longitudinal axis of the device. The middle body 11 consists of a plurality of parts 12-14, preferably as many parts as the number of annular elements in the device, of which the front 12 is substantially teardrop-shaped with the tip directed backwards, the latter partly entering a subsequent, likewise substantially teardrop-shaped part 13 but with an annular gap 15 therebetween for receiving turbulent medium which passes through the part 13 and out into a central body terminating, at first a convex part 14, which likewise adjoins the preceding part 13 with a ring shaped gap 16, in which turbulent medium passes into the part 14, which ends rearwardly pivoted out conically, whereby air passing through the middle body parts 13 and 14 is discharged at the end of the conical part at the greatest distance from the longitudinal axis in the diffuser part. In this way, the diffuser effect can be further enhanced. As can be seen from Figure 2, the accelerator part can be shortened as desired by the dashed lines in the upper half of the figure. In the embodiment according to Figure 2, the propeller or turbine means are not shown. According to a particular embodiment, however, the part 14 can be made rotating on its longitudinal axis and on its substantially conical mantle surface is provided with turbine means.

The number of steps or parts 1-4 of the device can of course be varied. A suitable number is, however, primarily for practical reasons, within the range 2 - 6, in particular 3 - 4. The device according to the invention is of course mounted on a stand or the like, which is rotatably mounted in the horizontal plane so that the device inlet opening can be set against the flowing medium, usually the wind. These parts of the device according to the invention are of a completely conventional nature and are not shown or described in more detail.

Practical experiments have been carried out with a device according to the invention, essentially of the embodiment described in Figure 1.

In this case, the rotation of a free-standing, free-running propeller has been compared with the rotational speed of a propeller inserted in an accelerator / diffuser according to the invention. In the experiments a propeller with a diameter of 19 cm and a pitch of 6 cm was used. The table below indicates the speeds achieved at specified wind speeds.

Chart.

Freestanding propeller: Wind speed Speed 3 - 4 m / so - looo R / m 5 m / s 26OQ R / m Propeller in combination.with a device essentially according to figure 1: Wind speed 'Speed 3 - 4 m / s 3,400 R / m 5 m / s _ 4,900 R / m As can be seen from the numerical values in the table above, at a wind speed as low as 3 - 4 m / second a 3 - 4 doubling of the propeller speed is obtained. At a wind speed of 5 m / second, a doubling of the propeller speed is largely obtained.

This means that the removable power is 8-fold.

Claims (4)

7900241-6 PATENT REQUIREMENTS Device 'for increasing the flow rate in a liquid or gaseous medium such as water or air and comprising a series, concentrically about a longitudinal axis, annularly arranged annular elements (1-4), enclosing a central channel in connection to which is placed a device for extracting the kinetic energy of the medium, preferably one or more turbines (10), which elements (1-4) are separated from each other by slots (5-7), and each of which has one towards the intended inlet side of the medium facing the front end edge, which is mainly located in an axial plane to the longitudinal axis with the axial plane of the front edges gradually shifted relative to each other, and partly a rear end edge facing the intended outlet side, characterized in that the elements (1-4) front end edges, which are offset rearwardly in the direction of flow nicks calculated from the outermost to the innermost element, so that the inlet opening formed by the front edges of the elements obtains an ice The flow direction tapered conform thereby forming an accelerator has such a rounded surface that a substantially laminar flow arises across the surface and that the gaps between the steps are narrow and so adapted that substantially only the part of the medium which, despite the surface properties form a turbulent flow is drained while the main part of the medium, thus showing a laminar flow, is transferred to the front edge surface of the inner angular element until the central channel is reached, and that the angular elements (1-4) at their rear end edges are thinned to tips known per se so aerodynamically designed that the medium leaves the rear end edge under substantially laminar flow, which tips for discharge backwards, outwards of the flowing medium are directed out of the longitudinal axis, whereby a diffuser is formed. Device according to claim 1, characterized in that the radially outwardly facing sides of the ring-shaped elements (1-4) in the accelerator part of the device near the respective front end edge form a convex curve extending in the flow direction of the medium with increasing distance from the length of the device. axis, while the outwardly facing sides of the diffuser part of the device next to the respective rear end edge at least in the case of the inner elements (2-4) have a curvature which in the flow direction of the medium 'at first constitutes a smooth continuation of the curvature of the accelerator part but then assumes a concave shape with U, v9oo241-6 __.._.-.... - __ increasing distance from the longitudinal axis, and that the inwardly facing sides of the elements (1-4) have a shape which is mainly adheres to the shape of the outside of the nearest adjacent element, so that said gaps (5'-7) become substantially evenly thick. 3. Device according to claim 1 or 2, characterized in that the slits (5-7) are provided with shielding means which give a medium flowing through the slits a rotation which coincides with and thereby reinforces the rotation. after the passage of the device (10) for recovering the kinetic energy of the medium. in Device according to one of Claims 1 to 3, characterized by a device (11) centrally located in the longitudinal axis, the cross sections of which are circular and which consist of a plurality of parts (12-14), preferably as many as the number of annular elements in the device. , namely a front part (12), which is substantially teardrop-shaped with the tip directed backwards in the direction of flow, the latter partly entering a subsequent likewise substantially teardrop-shaped part (13) but with an annular gap (15) therebetween for receiving turbulent medium, which passes through the part (13) and out into a central body terminating, initially convex part (14), which likewise adjoins the preceding part (13) with an annular gap (16), into which turbulent medium passes in in the part (14), which ends rearwardly pivotally conically, whereby medium passing through the middle body is discharged at the end of the conical part at the greatest distance from the longitudinal axis of the diffuser part.