AU2011318255A1

AU2011318255A1 - Swimflow generator

Info

Publication number: AU2011318255A1
Application number: AU2011318255A
Authority: AU
Inventors: Pieter Jan De Geeter
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-10-21
Filing date: 2011-10-21
Publication date: 2013-09-12
Also published as: WO2012051671A1

Abstract

An apparatus (111) for generating a flow current (118) across part of the upper surface of a swimming pool, for a swimmer to swim against, is disclosed. The apparatus has a radial impeller (121) with a plurality of vanes (123) disposed about a central horizontal axis and contained within a cylindrical body (113) having a horizontal outlet slot (119) spaced above and substantially parallel to the central horizontal rotational axis. The slot (119) communicates with a horizontal duct (117) depending from the circumference of the cylindrical body (113) to direct the flow of water. The apparatus (111) has an intake (133) at each end (131) of the radial impeller (121), and the vanes (123) of the radial impeller (121) are curved (135) toward the direction of rotation at each end of the radial impeller to provide axial thrust to assist in drawing water into each intake.

Description

WO 2012/051671 PCT/AU2011/001348 SWIMFLOW GENERATOR Field of the Invention This Invention relates to the generation of a flow or current in a body of water for a swimmer to swim against in a swimming pool, for exercise and fitness purposes. 5 Background Art A steady current in a water reservoir or pool is commonly created by nozzles from which the water is ejected at high speed. This requires a high back pressure; for example, to generate a flow over a width of - say - a 1.0 m and depth of - say 0.25 m (roughly twice the cross sectional body area of an adult human) at a 10 velocity of - say - 1 r/s would require a flow rate (Q) of around 0.25 m 3 per second. The velocity of 1 m/s Is chosen since that slightly exceeds the average sustainable speed through the water of an adult swimmer. It can be shown that the ejection velocity (v) of typical pool/spa nozzles is at least 15 10 m/s. The required pressure head (H) required to generate such velocity equals v*v/(2*g) In which g represents gravitational acceleration. This renders an H value larger than approximately 5 m water column. The net power (P) required to generate the required flow rate (0) follows from P = 20 d*g*Q*H in which d is the density of the water in kg per m3. Consequently the required net power P equals 1000*9.8*0.25*5 watts, amounting to around 12.5 kW. At current motor/pump efficiencies this would result in an energy demand of around 20 kW. This would be unaffordable for most pool owners and, over time, is likely to become restricted by Government regulation, in order to minimise 25 power demand and associated greenhouse gas production at the generating power station. Instead it would be preferable and beneficial to create the required flow rate by circulating the pool water at minimum pressure head build-up. This can be done 30 by means of propeller, screw or impeller systems. However, the water emanating from such systems has as strong rotary 'corkscrew' motion. This means that in 1 WO 2012/051671 PCT/AU2011/001348 addition to the water's kinetic energy in the main flow direction it also contains a high degree of rotational energy. This is highly unpleasant for the swimmer. As a consequence the water's rotary energy needs to be dissipated by means of vanes, baffles or screens. Each of these generate their own energy loss caused 5 by skin drag and form drag. As a consequence the energy demand of these systems is still relatively high, and not substantially lower than for nozzle systems. The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the 10 discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge as at the priority date of the application. It is an object of the invention to provide current flow generation In a swimming 15 pool in a manner which overcomes the aforementioned problems, or at least provides an alternative and improved arrangement. Throughout the specification unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood 20 to imply the Inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Throughout the specification unless the context requires otherwise, the word "include" or variations such as "includes" or "including", will be understood to 25 imply the inclusion of a stated integer or group of integers but not the exclusion of any other Integer or group of Integers. Disclosure of the Invention In accordance with the invention there is provided an apparatus for generating a flow current across part of the upper surface of a swimming pool, for a swimmer 30 to swim against, said apparatus having a radial Impeller with a plurality of vanes disposed about a central horizontal axis and contained within a cylindrical body having a horizontal outlet slot spaced above and substantially parallel to said central horizontal rotational axis extending along and from an upper extent of said 2 WO 2012/051671 PCT/AU2011/001348 cylindrical body and communicating with a horizontal duct depending from the circumference of the cylindrical body to direct the substantially horizontal flow of water, said apparatus having an intake at each end of said radial impeller, and the vanes of said radial Impeller being curved toward the direction of rotation at each 5 end of the radial impeller to provide axial thrust to assist in drawing water into each intake. In effect the radial impeller is a hybrid radial axial impeller. It has been found that this arrangement provides an unexpected gain in efficiency of an Impeller without 10 such curvature provided at the ends introducing an element of axial flow to the impeller operation. Preferably the Impeller has a central axle located along the central rotational axis of the Impeller, and the vanes of said impeller are stood off the central axle, so 15 that a void is provided between the vanes and the central axle in a low pressure zone of the impeller during operation. Preferably said radial impeller is configured for low pressure high volume operation. 20 In accordance with the invention there Is provided an apparatus, driven by an extemal electrical or hydraulic power source, fixed to the side of a swimming pool or other body of water, comprising an hydraulic cyclone with horizontal axis, contained within a partially closed housing as indicatively shown in FIG. 1, which, 25 during operation, draws in water in equal measure at both ends as indicated in FIG 2 whIlst, at the same time, ejecting the water radially as indicated in FIG 3, with each of the apparatus' blades curved at largest possible radius to prevent flow separation as indicated in FIG 4c so as to ensure that the apparatus' outflow has low turbulence intensity, minimal 'cork screw' flow rotation and largely parallel 30 flow lines, fanning out vertically and horizontally to such extent that the swimmer is fully contained within the body of the flow, as indicated in FIG 5 and FIG 6. Preferably the apparatus is provided with variable outflow rate, adjustable to the speed of the swimmer, in order to ensure that even at 'full speed' the swimmer 35 would not be able to reach the apparatus. a3 WO 2012/051671 PCT/AU2011/001348 Preferably the apparatus is provided with an external buoyancy chamber(s) in order. to enable it to slide up or down along vertical, or steeply inclined, rods or slides, enabling it to maintain a constant depth of immersion at varying water level. 5 Preferably the apparatus is provided with a rotationally adjustable flow deflector plate (16) in order to (a) adjust the elevation of the lower flow boundary (17) and the associated flow velocity (18) at a distance (19) most comfortable to swimmer (20) and/or to (b) make it possible to increase the depth of submergence of the 10 apparatus, to prevent air from being sucked into it. Preferably the apparatus is, in conjunction with its power generator, portable, enabling it to be manually transferred to, and operated in, other swimming pools or bodies of water, at minimal effort or cost. (if any) is Brief Description of the Drawings A preferred embodiment of the invention will now be described in the following description of a swimming pool flow current generator made with reference to the drawings, In which: 20 Figure 1 is a cut-away cross-section view through the swimming pool flow current generator showing the curvature in the blades of the impeller at the most distant end; Figure 2a is a view from above showing the direction of force imparted 25 during operation of the Impeller; Figure 2b is an end view showing the direction of force imparted during. operation of the impeller; 30 Figure 3 Is a cut-away cross-section view showing out-flow from the swimming pool flow current generator; 4 WO 2012/051671 PCT/AU2011/001348 Figure 4a, 4b and 4c are various flow vector models illustrating important principles of the Invention; Figure 5 is a side elevation showing the swimming pool flow current 5 generator installed in a swimming pool and in use; Figure 6 is a top plan view of the swimming pool flow current generator installed in a swimming pool and in use; 10 Figure 7 is an isometric view showing a single blade of the Impeller attached to its central axle; Figure 8 is a perspective view showing the swimming pool flow current generator with an alternative mount for a swimming pool and showing a is drive motor; and Figure 9 is an isometric view showing the impeller. Best Mode(s) for Carrying Out the Invention A novel, far more efficient way to generate the required flow rate in a swimming 20 pool flow current generator, at low energy demand, is by means of a cyclone with horizontal axis in the form of a swimming pool flow current generator 111 as indicated generally in figures 1 and 8. The swimming pool flow current generator 111 has a cylindrical body 113 with a 25 near horizontally disposed outlet 115 provided by a horizontal duct 117 depending from the circumference of the cylindrical body 113 to direct a substantially horizontal flow of water 118 from the outlet 115. The duct 117 communicates with a slot 119 in and extending entirely across the cylindrical body 113 through which water is urged by an impeller 121. 30 The impeller 121 Is a radial impeller with five vanes 123 disposed about a central horizontal axis provided by a central axle 125. The vanes 123 of the impeller 121 are stood off the central axle on mounting posts 127, so that a void 129 is 5 WO 2012/051671 PCT/AU2011/001348 provided between the vanes 123 and the central axle 125, in a low pressure zone of the impeller during operation. The Impeller 121 fills the cylindrical body 113. The slot 119 extends along an 5 upper extent of said cylindrical body 113, parallel with and above the central axle 125, so that water is expelled outwardly from the top of the cylindrical body 113, and directed by the duct 117 across part of the upper surface of a swimming pool, for a swimmer to swim against. 10 The cylindrical body 113 is open at each end 131, providing an intake 133 at each end 131 to allow inflow of water. To assist inflow of water, the ends 135 of each vane 123 of the Impeller 121 are curved in a forward direction (curved forwardly in the direction of rotation of the Impeller 121), so that the Impeller functions as an axial impeller at each end, while functioning as a radial Impeller with respect to 15 the outlet 115. With this arrangement, in effect the radial impeller is a hybrid radial axial impeller. It has been found that this arrangement provides an unexpected gain in efficiency of an Impeller without such curvature provided at the ends introducing an element of axial flow to the impeller operation, as will be discussed further In this description. The impeller is configured for low pressure 20 high volume operation. While the swimming pool flow current generator 111 may be mounted in a swimming pool in any conventional mechanical way, one example is illustrated- in figure 9. L-shaped arms 141 mount to the top of the duct 117, and are intended 25 to have their horizontal portions 145 bolted to a concrete pad 146 or the like at the side of the swimming pool. Drive is provided by an electric motor and gearbox 147, via belts 149 and pulleys 151. The impeller generates a straight outflow pattern with minimal rotary 'corkscrew' 30 motion (if any). Overall energy loss is minimized by the special curvature shaping of the cyclone's blades as shown in figure 4c, and figures 1, 7 and 9. This, in combination -with the fact that no rotational energy is produced, minimizes the energy demand of the swimming pool flow current generator 11. For example: for a cyclone with a flow ejection area of -say- 0.8 m * 0.125 m the required ejection 35 speed (ve) as required to generate a flow rate of -say- 0.25 m3/s follows from ve 6 WO 2012/051671 PCT/AU2011/001348 = 0.25/(0.8 * 0.125 ) = 2.5 m/s, rendering a kinetic energy head (H) of ve*ve/(2*g), amounting to approx. 0.3 m. pressure head. Required net power (P) then follows from: P=d*g*Q*H amounting to around 0.75 5 kW. At a -worst case- aggregate motor/cyclone efficiency of around 50% this renders an energy demand in the order of 1.5 kW (at affordable cost to the average pool owner) The hydraulic principles of operation will now be discussed. A fully submerged 10 cyclone (1) shown schematically in fig. 2a, requires open ends (2) to ensure that, during rotation of its rotor (*) the radial outflow (3) generated by the centrifugal force Is 'replenished' by axial inflow (4) from both ends. (*) not shown The rotor's revolution rate (n) follows from the expression n = ve/(2*pi*r) in which 15 ve is the exit velocity at the outer edge of the rotor. At ve is -say- 2.5 m/s and r is -say- 0.20 m. the rotational speed of the rotor is around 2 revolutions per second. If the rotor were not enclosed the water would be radially ejecting from the entire circumference of the cyclone, as shown in fig. 2b. As energy demand is 20 proportional to the size of the flow ejection area it is important to enclose most of the cyclone, except for the designated outflow slot (5) indicatively shown in fig. 3. The outflow rate (6) is proportional to the revolution rate of the rotor and to the volume of water 'trapped' between adjoining rotor blades (7) and (8). 25 In the case of -say- 5 rotor blades, a rotation rate of -say- 2 revolutions per second and a rotor length of -say- 0.8 m the trapped volume of water (9) of around 0.025 m3 is displaced during 1/5 revolution of the rotor (during a time period of 1/(2*5) = 0.1 s).This renders an outflow rate (Qe) of 0.025 / 0.1 = 0.25 m3/s. To satisfy the so-called continuity condition, this outflow is matched by 30 equal axial inflow rate (Qi) at both ends of the cyclone. Inflow area (Ai) at both ends equals 2 * (0.25*pi*Dr^2) in which Dr is the cyclone's rotor diameter. For Dr is -say- 0.40 m total Inflow area (Al) Is approximately 0.25 m2. Consequently the mean inflow velocity (vi) amounts to Qi 35 / Ai = 1 m/s (approx.) 7 WO 2012/051671 PCT/AU2011/001348 As shown in fig. 4a, the rotor's revolving speed (10) and inflow velocity (11) render a resulting flow vector (12) at a large angle (13) to blade (14), causing a substantial wake (15) with a high degree of turbulence behind each blade. 5 This greatly reduces the hydrodynamic efficiency of the cyclone. As a consequence its energy demand would be substantial. To minimize the size of the wake(s) and associated energy demand it is necessary to curve the rotor blades to an angle equal to the approach angle (13) of the resulting flow vector (12) 10 Radius (R) should not be small, as this would cause substantial flow separation and associated wake formation and indicated in fig. 4b. Instead, flow separation can be largely prevented by maximizing said radius as Indicated in fig. 4c. 15 An Important feature of the Invention Is the fact that the direction of flow vector (12) and associated, optimized, radius (R) of the blades is independent of the revolving speed of the cyclone's rotor and associated outflow rate. This Iq due to the fact that any increase in outflow rate (to accommodate a faster swimmer) would render a similar increase in inflow rate. This implies that the energy 20 efficiency of the cyclone is constant, Independent from rotational speed and associated outflow velocity (24) Note that during rotation the outer edge of the blades moves faster than the inner edge, in linear proportion to radial distance from the rotor's axis. This implies that 25 angle (13) of the blade's end would need to vary accordingly, rendering a skewed blade profile. This can be prevented by adopting the 'mid blade' value of angle (13) over its full 'height'. It can be shown that associated loss of energy efficiency of the cyclone Is minimal. 30 The invention includes various additional -novel- features described as follows, (with reference to fig. 5). Firstly: rather than rigidly fixing the cyclone (1) to the side of the water body it could be made detachable and constructed at such low weight that it can be 35 easily moved from one water body to another, carried by -at most- two persons. 8 WO 2012/051671 PCT/AU2011/001348 Second: a -rotationally adjustable- flow deflector plate (16) can be added to adjust the elevation of the lower flow boundary (17) and the associated flow velocity (18) at a distance (19) most comfortable to swimmer (20). By increasing the Inclination 5 angle of the plate it would also be possible to increase the depth of submergence of the cyclone in order to prevent air from being sucked in. Third: to allow for varying water level in the pool or water body, the cyclone (1) can be made to float, by means of buoyancy chamber (21) and/or by adding light 10 weight material with a density lower than water. As a consequence the floating assembly would be able to follow any variation in water level (22) by sliding up or down along upright(s) (23) which are attached to the side of the pool. Fourth: the electric motor powering the cyclone could be provided with a variable is speed option. This would make it possible to vary the ejection velocity (24) of the water. The motor can be located outside the pool or water body or can be attached to -or mounted on- the cyclone body. The invention entails the development of a hydraulic cyclone for generating a 20 sufficiently strong non-rotary current with low level of turbulence for use in swimming pools and other water bodies, at affordable investment- and operational cost.

Claims

1. An apparatus, driven by an external electrical or hydraulic power source, fixed to the side of a swimming pool or other body of water, comprising of an hydraulic cyclone with horizontal axis, contained within a partially closed S housing as indicatively shown In FIG. 1, which, during operation, draws in water in equal measure at both ends as indicated in FIG 2 whilst, at the same time, ejecting the water radially as indicated in FIG 3, with each of the apparatus' blades curved at largest possible radius to prevent flow separation as indicated in FIG 4c so as to ensure that the apparatus' outflow 10 has low turbulence intensity, minimal 'cork screw' flow rotation and largely parallel flow lines, fanning out vertically and horizontally to such extent that the swimmer Is fully contained within the body of the flow, as Indicated in FIG 5 and FIG 6.

2. An apparatus as claimed in claim I with variable outflow rate, adjustable to 15 the speed of the swimmer, in order to ensure that even at 'full speed' the swimmer would not be able to reach the apparatus.

3. An apparatus as claimed in claim 1 and/or claim 2, provided with external buoyancy chamber(s) in order to enable it to slide up or down along vertical, or steeply inclined, rods or slides, enabling it to maintain a constant 20 depth of Immersion at varying water level.

4. An apparatus as claimed in claim 1 and/or claim 2 and/or claim 3 with a rotationally adjustable flow deflector plate (16) in order to (a) adjust the elevation of the lower flow boundary (17) and the associated flow velocity (18) at a distance (19) most comfortable to swimmer (20) and/or to (b) make 25 it possible to increase the depth of submergence of the apparatus, to prevent air from being sucked into it.

5. An apparatus as claimed in claim 1 and/or claims 2 through 4, which, in conjunction with its power generator, is portable, enabling it to be manually transferred to, and operated in, other swimming pools or bodies of water, at 30 minimal effort or cost. (if any)

6. An apparatus for generating a flow current across part of the upper surface of a swimming pool, for a swimmer to swim against, said apparatus having a 10 WO 2012/051671 PCT/AU2011/001348 radial impeller with a plurality of vanes disposed about a central horizontal axis and contained within a cylindrical body having a horizontal outlet slot spaced above and substantially parallel to said central horizontal rotational axis extending along and from an upper extent of said cylindrical body and 5 communicating with a horizontal duct depending from the circumference of the cylindrical body to direct the substantially horizontal flow of water, said apparatus having an intake at each end of said radial impeller, and the vanes of said radial impeller being curved toward the direction of rotation at each end of the radial impeller to provide axial thrust to assist in drawing 10 water into each intake.

7. An apparatus as claimed in claim 6 wherein the impeller has a central axle located along the central rotational axis of the impeller, and the vanes of said impeller are stood off the central axle, so that a void is provided between the vanes and the central axle in a low pressure zone of the 15 impeller during operation.

8. An apparatus as claimed in claim 6 or 7 wherein said radial impeller is configured for low pressure high volume operation.

9. An apparatus substantially as herein described with reference to the drawings. 20