This invention relates to an energy conversion turbine unit, for acting as an energy-generating turbine or generator. 3

Energy conversion turbine units are very well known in a number of applications. For example, water turbines are known, which can be mounted in ducts, such as the Francis turbine. Alternatively, turbines comprising propellers mounted on a central hub can be used, for example for engaging flowing water or air flow. Such generators comprising propellers are well known in the form of wind turbines. Although a wide variety of wind turbine designs are known, employing both horizontal axis turbines and vertical axis wind turbines, large horizontal axis three or four bladed wind turbines have become familiar as commercial energy generating units. However, such units have a disadvantage in that they cannot operate when the wind exceeds a certain maximum speed. Above this speed, there is a danger of precession of the hub, which can lead to damage to the turbine.

The present invention is concerned with energy conversion turbine units for engaging free flowing fluid streams, such as water or air such as wind streams, which can operate under high fluid flow conditions.

The inventor has realised that an energy conversion turbine unit for engaging a free flowing fluid can be operated at high speed if the blades are supported at their periphery in an annular rotor, which is rotatably mounted in a nacelle.

Accordingly, the present invention provides an energy conversion turbine unit for converting free-flowing dynamic stream energy into rotation, comprising a nacelle, an annular stator element and an annular rotor element rotatably mounted in the stator element, stream-engaging blades extending radially inwardly from the annular rotor into a flow duct defined therein.

Dynamic flow of liquids, gases or a combination of both is converted into a different form of energy by transforming the force of free-flowing streams into a rotation force by the revolving motion of the blades attached to the turbine rotor. The efficiency of the turbine is measured by its ability to produce energy and this is dependant on the design of the turbine propeller and the rotor unit as a whole.

The free flowing dynamic stream may comprise any suitable fluid, for example liquid or gas. For example, it may comprise a flow of water or a flow of air, for example wind flow. The present invention is suitable for engaging a stream of such fluid which is already flowing, for example the wind or a tidal flow.

The present invention is intended for engagement with a body of free flowing fluid which extends in the direction normal to its flow direction for a distance which is larger than the corresponding dimension of the energy conversion turbine unit. This is in contrast to duct-mounted turbine units which engage the whole of the flowing stream.

Preferably, the present invention provides a horizontal axis turbine.

A problem typically encountered by free-flowing energy conversion turbines such as existing wind energy extracting turbines, is that energy conversion from free-flowing fluid streams is limited because energy extraction implies decrease of fluid velocity. This decrease of kinetic energy of the free-flowing fluid stream cannot fall down to zero, it should continue travelling but as the turbine is an obstruction to the fluid flow some fluid may not pass through the turbine and may simply flow around it.

To maximise design efficiency the present invention proposes to integrate both blades (e.g. propeller) and hub within the turbine rotor shaft in order to streamline the design and maximise efficiency by reducing negative effects of drag and friction.

The new design of the nacelle and turbine unit as a whole and the rotor in particular creates a slippery profile which reduces the negative effects of drag and improves the velocity of flow, maintaining the kinetic energy of the stream through the turbine unit while generating the maximum rotational speed.

In the present application, the reference to a "nacelle" means a unit for engagement with a free flowing fluid, the dimension of the body of free flowing fluid in a direction normal to the flow direction being greater than the dimension of the nacelle in the direction normal to the flow direction.

Preferably, the nacelle is streamlined. That is, the outer profile of the nacelle preferably curves smoothly or does not increase or decrease in dimension normal to the flow direction. Preferably, the outer profile has no step increases or decreases in the dimension normal to the flow direction. Preferably, the dimension normal to the flow direction of the outer profile of the nacelle increases from the upstream end of the nacelle to a maximum and then decreases again in the downstream direction.

Preferably, the nacelle is of length in the flow direction at least equal to its maximum dimension in the direction normal to the direction of flow and preferably at least 1.5 times the dimension in the direction normal to the direction of flow. This is found to give particularly good streamlining.

A fairing may be provided at the upstream end or downstream end, or both, to improve streamlining.

The blades of modern large wind turbines become very long and their rotational speed decreases making it difficult to achieve a required tip speed ratio. This implies that the part of the blade close to the root or the rotor hub will operate at a very low speed ratio, thus producing rotational wake-related losses. As a general rule, the upper 1/3 of the blade close to its tip generates 2/3 of the power for the whole blade. The lower 1/3 of the blade closest to the hub is almost unproductive in nominal conditions.

Preferably the blades of the present invention are shorter than conventional wind turbines as this increases their rotational speed and helps to maintain a tip speed ratio, which allows the upper part of the blade to be attached to the rotor and produce rotational wake-related gains.

The annular stator element preferably comprises permanent magnets, electro magnets and/or windings for taking electrical energy generated by rotation of the rotor. Such magnets, electro magnets and windings may be of any conventional design as will be known to the person skilled in the art. There may be a further set of windings at a first position in the flow direction and a second set of windings in a second position in the flow direction. This will allow the twisting forces in the axial direction to be effectively resisted.

The stator preferably extends for a substantial distance in the axial direction. Preferably, its axial extent is at least equal to its diameter. Preferably, it is at least 1.5 times its diameter.

The rotor preferably extends for a substantial distance in the axial direction. Preferably, its axial extent is at least equal to its diameter. Preferably, it is at least 1.5 times its diameter.

The inner surface of the annular stator may be of constant diameter or it may decrease or increase (or both) in the axial direction. It may decrease or increase smoothly or in steps. Where the diameter of the stator increases or decreases, reference above to the ratio of the axial length to the diameter will be taken with respect to the maximum diameter.

The annular rotor element may comprise electro magnets, permanent magnets or windings. Preferably, it only comprises permanent magnets, so there is no need to make electrical connections to the rotor. The design of windings may be of any conventional form. They may be formed of a conventional conductor or superconductor material

The flow duct defined inside the annular rotor may be of constant diameter or it may decrease or increase (or both) in the axial direction. It may decrease or increase smoothly or in steps. Where the diameter of the stator increases or decreases, reference above to the ratio of the axial length to the diameter will be taken with respect to the maximum diameter.

Preferably, the flow duct decreases from an upstream end to a minimum dimension and then increases. Preferably, the blades extend into the flow duct at or near the part of minimum dimension.

The radially inwardly extending blades of the rotor element may have any suitable shape. They may correspond to the blade design of conventional wind turbines. Alternatively, they may comprise blade members of substantial axial extent. For example, they may extend in the axial direction for a distance at least equal to their radius and preferably equal to at least 1.5 times their radius. They may have leading edges or trailing edges which are normal to the flow direction or at an angle to the flow direction. There may be any suitable number of stream engaging blades, for example at least two, more preferably at least three.

The stream engaging blades may extend to the centreline of the flow duct. They may meet at their inward ends. They may be connected together for extra strength. They may meet at a centre body, for example a streamlined shape.

The maximum diameter of the flow duct defined by the rotor element preferably comprises between 0.5 and 0.75 of the maximum external dimension in the direction normal to the flow of the nacelle.

The flow duct may be bounded substantially completely by the rotor. Alternatively, there may be a section upstream of the rotor. There may be a section downstream of the rotor. Either of these sections may comprise fixed blades projecting axially inwardly, for example to create or arrest rotational movement of the fluid in the duct, as appropriate.

Similarly, the rotor may comprise a portion in which the flow is engaged by blades and a portion in which the flow is not engaged by blades, in order to obtain stable flow.

The rotor may be rotatably mounted by any suitable bearing design. It may be mounted on peripheral bearings or there may be an axial bearing in the middle. Peripheral bearings are preferred, as they will not require structures which interrupt the flow duct within the rotor. Preferably, there is a plurality of bearings, spaced apart from one another in the axial direction. Preferably the rotor unit will rotate resting on magnetic suspension bearings thus further reducing negative effects of friction.

In a preferred embodiment, the present invention provides an energy conversion turbine unit comprising a turbine generator for converting free flowing dynamic stream energy into rotation force, the generator comprising a nacelle and a propeller element which sits housed in a tubular duct rotor, which is suspended on a magnetic force field, that rotates about an axis inside a tubular duct stator.

The invention will now be described solely by way of example and with reference to the accompanying drawings in which:

Brief Description of the Drawings

Figure 1 is a schematic, part sectional isometric view of a first embodiment of energy conversion turbine unit of the present invention.

Figure 2 is a schematic cross-section through the axis of Figure 1.

Figure 3 is an end view of Figure 1.

Figure 4 is a rear view of Figure 1.

Figure 5 is an enlarged partial view of Figure 1.

Figure 6, and

Figure 7 show views of the blades.

Figure 8 is schematic part sectional view of Figure 1 , showing magnetic suspension bearings.

Figure 9 is a part sectional view of the magnetic bearing.

Figure 10 shows a schematic isometric view of the magnetic bearing.

Figure 11 is a schematic isometric view of the unit, showing the positions of the magnetic suspension bearings with respect to the stator and rotor.

Figure 12 shows an isometric view of a winding of the unit.

Figure 13 is a further schematic part sectional isometric view showing positions of magnetic poles.

Figure 14 is a schematic isometric view showing the windings in place on the stator.

Figure 15 is a schematic, part sectional isometric view of a second embodiment of energy conversion turbine unit of the present invention.

Figure 16 is a schematic cross-section through the axis of Figure 15. Figure 17 is an end view of Figure 15. Figure 18 is a rear view of Figure 15.

Detailed Description of the Drawings

The Figures show an embodiment of an energy conversion turbine unit according to the present invention. It is suitable for use as a wind turbine. In

practice it can be mounted in any suitable manner, for example on a tower or support column at a suitable high for engaging optimum wind speed.

Fig. 1 shows a nacelle N, a horizontal shaft unit H, the dynamic inflow W causing propeller R to rotate.

Fig. 2 shows a sectional view of nacelle N, horizontal shaft unit H, the dynamic inflow Wi generating the rotation of propeller R and depicting the dynamic outflow Wo.

Figs. 1 and 2 also show that the outer shape of the nacelle has an aerodynamic shape for minimising drag. In Fig. 1, a fairing F can be seen at the upstream end of the nacelle. The contour of the fairing is shown by the pattern lines FP, which show that the fairing has an annular aerodynamic shape.

In use, the horizontal shaft unit will comprise a stator assembly SA and rotor assembly RA, as described further below.

In can also be seen that the nacelle is of length in the direction of flow (axial direction) which is at least 1.5 times the maximum dimension in the direction normal to the direction of flow (radial direction), and nearly twice the maximum dimension in the radial direction. It can also be seen that the flow duct occupied by the propeller R is of dimension in the radial direction about half the maximum dimension of the nacelle in the radial direction. It can also be seen that the propeller occupies approximately half the volume of the flow duct, a flow chamber FC being defined upstream of the propeller for optimum flow characteristics.

Fig. 3 shows the front view Hf of nacelle N, horizontal shaft unit H, and propeller R.

Fig. 4 shows the rear view Hb of nacelle N, horizontal shaft unit H, and propeller R.

Fig. 5 shows the horizontal shaft unit H, the dynamic inflow W generating the rotation of propeller R and rotor assembly RA.

Fig. 6 shows propeller R from angle of view R1. Fig. 7 shows propeller R from angle of view R2.

Fig. 8 shows the horizontal shaft unit H, the dynamic inflow W generating the rotation of propeller R and rotor assembly RA, arrows indicate the position of Magnetic suspension bearings MB1 and MB2 axially spaced apart.

It should be noted that there are two electro magnetic bearings MB1 and MB2 to provide optimum support for the rotor.

Fig. 9 shows the cutaway view of magnetic bearing MB ₅ with the magnet M1 exerting magnetic force north N directed outwards toward magnet M2 that is also exerting magnetic force north N inwards toward magnet M1 thus creating an air cushion between magnets M1 and M2.

Fig. 10 shows the magnetic suspension bearing MB with arrows indicating the positions of magnets M1 and M2 relative to cutaway view Fig2, and arrows indicating the position of stator SR and rotor RT of the magnetic suspension bearing MB within the horizontal shaft unit H on Fig1.

Fig. 11 shows the internal view of horizontal shaft unit H, illustrating the positions of stator assembly SA, rotor assembly RA and superconducting wire unit SU. The superconducting wire unit SU can be replaced by conventional windings, for example of copper or other suitable material if desired. The wire unit SU provides windings for generating an electro magnetic force to interact with the magnetic field of the rotor assembly RA.

Fig. 12 shows the superconducting wire unit SU and arrows indicating the positions of laminated core LC on the unit SU and on stator assembly SA of horizontal shaft unit H on Fig1. Fig2 also shows the armature windings AW with arrows indicating the position of AW on the superconducting wire unit SU and on stator assembly SA of horizontal shaft unit H on Fig1.

Fig. 13 again shows the internal view of horizontal shaft unit H, illustrating the positions of rotor assembly RA and stator assembly SA. Magnet assembly MS of the rotor assembly RA has arrows indicating the positions of the magnetic poles north N and south S attached to the rotor assembly RA.

Fig. 14 shows the rotor assembly RA and stator assembly SA inside the coil of superconducting wire unit SU.

On Fig. 1 illustrates nacelle N containing a horizontal shaft unit H guides the dynamic inflow W representing wind flow, gas flow, liquid flow or a mixture of both, which travels along the length of the shaft interior causing propeller R to rotate.

The dynamic inflow Wi, Fig. 2 enters the opening at the front of horizontal shaft unit H, see Fig. 3, exerts a force onto propeller R causing it to rotate, see Figs. 6 and 7 and drives outflow Wo to exit the rear of unit H, see Fig. 4.

The outer tips of propeller R are attached to the inside edge of rotor assembly RA, Fig. 5. The rotor assembly RA sits inside the rotor RT of magnetic suspension bearings MB1 and MB2 see Fig. 8. Rotor RT rotates inside stator SR, Fig. 10 suspended on a magnetic field see Fig. 9.

The outer portion of rotor assembly RA has 4 magnets MS attached with the North Pole N and South Pole S opposite each other Fig. 13. The outer portion of stator assembly SA, Fig. 11 is positioned surrounding and enclosing rotor assembly RA, Fig. 11 and Fig. 13.

δ

The superconducting wire unit SU, Fig. 12 is positioned on the outer portion of stator assembly SA, Fig. 11. Armature windings AW and laminated core LC make up the superconducting wire unit SU, Fig. 12 which is positioned on the outer portion of stator assembly SA, Fig. 11.

The magnets MS attached to the rotor assembly RA rotate inside the coil of superconducting wire unit SU and produce an electric current; see Fig. 13 and Fig. 14.

Figure 15 is a schematic, part sectional isometric view of a second embodiment of energy conversion turbine unit of the present invention.

Much of the design is similar in construction and function to the design of figure 1 and will not be described further. Similar parts are given similar references to Figure 1.

However, it can be seen that the flow duct defined by the rotor has a smoothly curving profile in the axial direction, which decreases from the upstream end to a minimum diameter approximately in the middle of the duct and then increases again to the downstream end. This provides a venturi shape, with an accelerated flow at the minimum diameter portion. Five blades, in the form of a propeller shape, extend radially inwardly from the rotor at the minimum diameter portion and meet in a streamlined centre body.

The present invention has been described above by way of example only and modifications can be made within the invention.