This invention relates to technical means used in aerodynamics and hydrodynamics for controlling the flow velocity of fluid media and can be used in the power industry and in other technical fields for controlling the flow velocity of fluid media.

Known is (RU Patent 2281883) is an air braking device comprising nozzles and technical means for obtaining the desired properties of air. Said known device is also provided with a means for energy excitation of air; the case of the device contains a vertically installed ascending air flow accelerator consisting of at least two convergent nozzles having a pressure-sealed connection between them; each nozzle is introduced, either rigidly or an with axial degree of freedom, into the next nozzle in sequence to form at least one plane between said two nozzles which plane comprises input valves on its wall and a means for energy excitation of air; the cavities comprise pressure gages; in the top part of said device, the air flow supplied from the accelerator is branched and directed via air ducts towards two or more vertical output nozzles arranged at 180° to the vertical direction and towards one or more horizontal nozzles; air flows supplied from the accelerator can be controlled with the velocity sensors of the device itself in three directions and the flow velocity at the output of all the nozzles; furthermore, the device comprises air duct louver servo units and a device control unit. Disadvantage of said known device is its narrow application range.

Also known is (RU Patent 2059839) is a combustion engine exhaust flow accelerator with an ejector comprising an exhaust pipe connected to the exhaust system via an adapter at one side and extending to the atmosphere through a pipe bell, and an accelerator unit installed between said adapter and the inner surface of said pipe bell. Said accelerator unit is conical in shape and is installed behind said adapter along the pipe axis, its cone point being co-directed with the exhaust flow; the outer side of said cone has exhaust gas flow channels and additional channels for secondary ejected air, wherein the cross-section shape of said flow channels transforms from triangular to dovetail one as one moves from the cone point to the butt-end, and the triangular cross-sections are obtained by splitting the cross-section area of said flow channels into n sections (n > 2); said ejector is formed by an annual slot between the inner side of said pipe bell at its connection with the cone butt-end and the outer surfaces of said flow channels and said additional channels for secondary ejected air, and said pipe bell is a truncated cone in shape with a rounded front face towards the gas flow direction. Preferably, said flow channels are arranged helically and connected to the surfaces of said cone, said pipe bell and said adapter. The output cross-section of said pipe bell is typically a Laval nozzle.

Disadvantage of said known device is its narrow application range as it is only suitable to automotive applications.

Also known is a combustion engine exhaust flow accelerator with an ejector comprising an exhaust pipe connected to the exhaust system via an adapter at one side and extending to the atmosphere through a pipe bell, the output cross-section of said pipe bell being a Laval nozzle. Said accelerator is a faceted cone installed behind said adapter coaxially with said output pipe, the outer side of said cone has exhaust gas flow channels in the form of a set of thin- walled small- diameter pipes the bottom parts of which are supported by the cone facets and the top parts are supported by the pipe bell.

Disadvantage of said known device is its narrow application range as it is only suitable to automotive applications.

The object of this invention is to provide for local acceleration of a fluid flow thereby expanding the applications of natural and technical low kinetic energy fluid flows in various field of engineering.

It is suggested to achieve said object by using a flow accelerator comprising at least one working element in the form of a polyhedron at least two facets of which are preferably parallel, wherein each of said parallel facets is a circle or a polygon circumscribing a circle, further wherein the diameters of said circles are not equal; if said circles are sectioned by a plane containing the line connecting the centers of said circles wherein said line lies in said plane, then the point O in which the plane intersects the smaller diameter circle and which is accepted as the origin of a two-dimensional coordinate system, wherein the X-axis OX lies in said plane parallel to said line connecting the centers of said circles and the Y-axis OY is perpendicular to the X-axis in said plane and is directed away from the line connecting the centers of said circles, and the point M in which the plane intersects the larger diameter circle are located at the same side of said plane relative to said line connecting the centers of said circles, and the points O and M are in such a relationship that the coordinates of the point M in said plane are above the X-axis OX and to the right of the Y-axis OY in the area limited at one side by the arc AB of the circle of radius R ₁ = 0.6D, where D is the diameter of the smaller circle, at another side by the segment BC of a line parallel to the X-axis OX and is located at the distance 0.7D above the X-axis, at the third side by the arc CE of the circle of radius R ₂ = 2.0D and at the fourth side by the segment EA of a line parallel to the X-axis OX and is located at the distance 0.1D above the X-axis, wherein the centers of the circles of radii Ri and R ₂ are on the positive semi-axis of the Y- axis OY at the distances 0.6D and 0.2D from the origin of coordinates O, respectively. Figure 1 shows the cross-sections of the smaller and the larger diameter circles by the plane passing through the centers of those circles. The points O and O ¹ are the intersection points of the plane and the smaller diameter circle. The distance between the points O and O' is the diameter of the smaller circle equal to D. The point O is the origin of the two-dimensional coordinate system. The points M and M' are the intersection points of the plane and the larger diameter circle. The distance between the points M and M ¹ is the diameter of the larger circle. The dashed line KK ¹ is the line connecting the centers of said circles. The arc AB is formed by the Ri radius circle and the arc CE is formed by the R ₂ radius circle. The line segments BC and EA are formed by lines located at the distances of 0.7D and O. ID from the X-axis OX, respectively. The point M is located inside the polygon ABCE. Said polygon is preferably a truncated pyramid or a truncated cone, and more preferably the cone element of said truncated cone is concave towards the cone central line. The shape of said concave line (parabola, hyperbola, polygonal line etc.) has been experimentally shown to have but a little effect on said technical result, but the most preferable embodiment is the arc OM of circle as shown in Fig. 1. Preferably, the line connecting the centers of the smaller and the larger diameter circles that are circumscribed by the above polygons is the symmetry axis of the device and is co-directed with the incident flow. Said technical result is achieved for any types of polygons.

Said flow accelerator may further comprise a cylindrical element or a polyhedron circumscribing said cylindrical element and being tangent with the surface of a polyhedron which is the smaller diameter circle or a polygon circumscribing said smaller diameter circle.

Figure 2 shows one option of an abutment connection between said cylindrical element or the polyhedron circumscribing said cylindrical element and the polyhedron of said element which is preferably a truncated cone the cone element of which is the arc OM obtained by intersecting with the plane containing the line connecting the symmetry axes of said cone and said cylindrical element forming the basis of an additional polyhedron wherein said line lies in that plane. The dashed line TT ¹ in Fig. 2 is the line connecting the symmetry axes of said cone and said cylindrical element. Here OMM'O ¹ is the section of the truncated cone polyhedron by the plane, and OVV ¹ O' is the section of the cylindrical element by the plane. The arrows in Fig. 2 show one of the incident flow directions coincident with the symmetry axis of the device for this connection option.

Said technical result can alternatively be achieved by using a flow accelerator comprising at least one working element having a polygonal shape at least two facets of which are preferably parallel, wherein each of said parallel facets is a circle or a polygon circumscribing a circle, further wherein the diameters of said circles are not equal, but one of these diameters is equal to the diameter of the smaller circle; if said circles are sectioned by a plane containing the line connecting the centers of said circles wherein said line lies in said plane, then the point O in which the plane intersects the smaller diameter circle and which is accepted as the origin of a two- dimensional coordinate system, wherein the X-axis OX lies in said plane parallel to said line connecting the centers of said circles and the Y-axis OY is perpendicular to the X-axis in said plane and is directed away from the line connecting the centers of said circles, and the point N in which the plane intersects the larger diameter circle are located at the same side of said plane relative to said line connecting the centers of said circles, and the points O and N are in such a relationship that the coordinates of the point N' in said plane are above the X-axis OX and to the right of the Y-axis OY in the area limited at one side by the arc FG of the circle of radius R ₃ = 0.5D, where D is the diameter of the smaller circle, at another side by the segment GH of a line parallel to the X-axis OX and is located at the distance 0.4D above the X-axis, at the third side by the arc HJ of the circle of radius R ₄ = 1.6D and at the fourth side by the segment JF of a line parallel to the X-axis OX and is located at the distance 0.05D above the X-axis, wherein the centers of the circles of radii R ₃ and R ₄ are on the positive semi-axis of the Y-axis OY at the distances 0.5D and 1.6D from the origin of coordinates O, respectively. Figure 3 shows the cross-sections of the smaller and the larger diameter circles by the plane passing through the centers of those circles. The points O and O' are the intersection points of the plane and the smaller diameter circle. The distance between the points O and O' is the diameter of the smaller circle equal to D. The point O is the origin of the two-dimensional coordinate system. The points N and N' are the intersection points of the plane and the larger diameter circle. The distance between the points N and N' is the diameter of the larger circle. The dashed line PP ¹ is the line connecting the centers of said circles. The arc FG is formed by the R ₃ radius circle and the arc HJ is formed by the R ₄ radius circle. The line segments GH and JF are formed by lines located at the distances of 0.4D and 0.05D from the X-axis OX, respectively. The point M is located inside the polygon FGHJ.

Said polygon is preferably also a truncated pyramid or a truncated cone, and more preferably the cone element of said truncated cone is concave towards the cone central line. The shape of said concave line (parabola, hyperbola, polygonal line etc.) has been experimentally shown to have but a little effect on said technical result, but the most preferable embodiment is the arc ON of circle as shown in Fig. 3. Preferably, the line connecting the centers of the smaller and the larger diameter circles that are circumscribed by the above polygons is the symmetry axis of the device and is co-directed with the incident flow. Said technical result is achieved for any types of polygons. Figure 4 shows one option of an abutment connection between said first and second polyhedrons which are preferably truncated cones the cone element of which is the arc obtained by intersecting with the plane containing the line connecting the symmetry axes of said cones wherein said line lies in that plane. Here OMMO ¹ is the section of the first truncated cone by the plane, and ONN ¹ O ¹ is the section of the second truncated cone by the plane. The dashed line TT' in Fig. 4 is the line connecting the symmetry axes of said cones which is the symmetry axis of the device and coincident with the incident flow direction for this connection option.

Figure ,5 shows one option of an abutment connection between the first polyhedron which is preferably a truncated cone the cone element of which is an arc, a cylindrical element abutting to said first polyhedron, and the second polyhedron which is preferably a truncated cone the cone element of which is an arc of a circle, said second polyhedron abutting to said cylindrical element, sectioned by a plane containing the line connecting the symmetry axes of said truncated cones wherein said line lies in that plane. OMM ¹ O ¹ is the section of the first truncated cone by the plane, OVVO' is the section of the cylindrical element by the plane, and VNN ¹ V is the section of the second truncated cone by the plane. The dashed line TT ¹ in Fig. 5 is the line connecting the symmetry axes of said truncated cones and said cylindrical element which is the symmetry axis of the device and coincident with the incident flow direction for this connection option.

Any of the above elements may comprise an additional polyhedron located between the polyhedron forming said element and its symmetry axis. Said polyhedron is preferably a truncated pyramid and more preferably a truncated cone the cone element of which is a parabola, a hyperbola, or a polygonal line.

Figure 6 shows one option of a connection between the first polyhedron which is preferably a truncated cone the cone element of which is an arc of a circle. Here OMMO ¹ is the section of the first truncated cone by the plane, and OUUO' is the section of the embedded truncated cone by the plane. It is valid that 0.3D < L < 3.0D. The larger diameter of the embedded truncated cone is smaller than the larger diameter of the outer truncated cone.

Figure 7 shows a structure comprising two abutting elements one of which comprises an additional polyhedron.

The flow accelerator design suggested herein may have different applications.

In one application related to the power industry the device can be used in the designing of wind or hydropower plants.

Wind power plants are widely used in high yearly average wind speed. Typically, all wind turbine manufacturers design their items for a wind speed of above 10-11 mps. Therefore developing wind power plants with a design wind speed of 5-6 mps gives broad opportunities for building wind power plants in most regions of the world. On the other hand, flow acceleration in the windwheel plane allows using smaller wind power plants while retaining the output power or largely, by 9-12 times, increasing the power of existing plants.

The device can be used in wind or hydropower plants where the windwheel or the water turbine axis is parallel to the incident flow axis (horizontal axis plants). Then the device allows increasing the incident flow velocity by 2.28 times. The windwheel or the water turbine is installed normal (or at a small angle) to the flow, and its rotation causes the electric machine (e.g. a current generator) to convert the kinetic energy of the flow in the windwheel installation point to electric power.

In wind or hydropower plants with the axis horizontal but normal to the incident flow, the windwheel or the water turbine is installed so the wheel rotates in the highest speed zone.

The device can also be used in vertical axis turbines and can simultaneously solve the two main problems of the existing vertical axis turbines, i.e. the high flow velocity required to start the machine and the blades overcoming the resistance of the flow passing through the windwheel or the water turbine. If the device is used with a vertical axis turbine operating with a 5 mps incident flow, a higher flow velocity (e.g. 11 mps) can be achieved in the wheel area. When the flow passes this area, leaves the device and slows down to the surrounding flow, it will reenter the device from the opposite side where the flow velocity is lower, e.g. almost equal to or for some process parameters even lower than that of the incident flow. The blades in that turbine area will have to overcome a significantly smaller resistance of the slowed down flow passing through them than if the velocity of the passing flow was equal to that of the incident flow. The combined effect, i.e. the reduction of the incident flow velocity required to start the windwheel or water turbine and the increase in the flow velocity at the front blades along with the reduction of the flow velocity after passing the wheel, largely increases the efficiency of vertical axis turbines. Along with power industry applications (in windwheels and water turbines for accelerating the incident flow and thus either increasing the output power of same-sized turbines or efficient operation of same-sized turbines at lower incident flow velocities), it can also be used in other fields of engineering where it is required either to increase the local velocity of flows or the quantity of fluid media (air, liquid etc.) passing through a limited diameter channel.

The use of this device often allows collecting the flow from an area greater than that of the device itself. This means that if the device is submerged into a steady state flow and a pressure differential is developed between the area in front of the device and inside the device, the device collects much more of the working media than a standard pipe would.

This invention can be illustrated with the following example.

A standard 20 m rotor installed power 50 kW windwheel is capable of producing 7-8 kW at 5 mps wind speed and/or 45-50 kW at 10 mps wind speed. The implementation of the device in a same-size rotor windwheel will provide for an output power of 75-80 kW at 5 mps wind speed and/or more than 500 kW at 10 mps wind speed, the current generator being upgraded accordingly.

When the flow accelerator according to this invention was implemented for a 5 mps incident air flow with an up to 20% turbulence and a typical energy carrier vortex size of up to 1 m, an average flow velocity of 10.9-11.4 mps was obtained.