Turbine

Abstract

Disclosed is a turbine comprising a series of blades 10 and an aperture, where in the blades are reversibly expandable and compressible, the diameter of the aperture formed by the blades being adjustable by reversibly expanding or contracting the blades. The blades may be positioned tangentially to the central axis of the turbine. The blades may be crescent shaped, there may be more than one form of blade, there may be two series of blades 12,14, each series having a different form, the two series of blades may intersect at an angle. The turbine may be used in a system which includes a fuel source, electromagnetic source or charged particle source.

Description

Field of the Invention The present invention relates to a turbine and systems for implementing the turbine. In particular, the turbine is reversibly expandable and compressible so that conditions can be altered as required. Background of the Invention Engines typically use turbines in high temperature environments once gas has passed through a combustion chamber. As such conventional turbines are subject to very high temperatures and pressures, they must be designed predominantly for performance under such conditions. The present invention, however, seeks to provide a turbine to act as a compressor and throttle, in a lower temperature operating environment. This lower operating temperature opens the possibility of designing the turbine for additional uses. Summary of the Invention Aspects and embodiments of the present invention are set out in the appended claims. These and other aspects and embodiments of the invention are also described herein. According to a first aspect, there is provided a turbine comprising a series of blades and an aperture, wherein the series of blades is reversibly expandable and compressible and wherein a diameter of the aperture is adjustable by reversibly expanding or compressing the series of blades. The reversibly expandable and compressible nature of the turbine advantageously provides control over its properties - for example, how it interacts with gases passing through. The turbine may alternatively be referred to as a ‘guide’ and / or a ‘flow guide’. The turbine is preferably rotatable but may not be rotated in all implementations. The blades may alternatively (and interchangeably) be referred to as ‘plates’. Preferably, the blades of the series of blades are positioned tangentially to a central axis of the turbine. In some implementations, the blades may have a crescent shape and are arranged such that the convex edges are positioned radially distal from a or the central axis of the turbine. Preferably, the series of blades comprises a first series of a first blade form and a second series of a second blade form. The first series of blades preferably engages at an angle with the second series of blades to form the turbine. In some implementations, the first series of blades may be located at a greater radial distance from a or the central axis of the turbine than the second series of blades. In other words, the first series of blades may be located radially outside of I outwardly from the second series of blades (in particular, the centres of the first series of blades may be located radially outwards from the centres of the second series of blades). However, the inner edges of the first series of blades may typically be located radially inwards from (or relative to) the outer edges of the second series of blades. Typically, the outer (convex) curved edge of the first series of blades may have a larger radius of curvature than the inner (concave) curved edge. This may preferably be in a ratio of 1.3:1. The inner (concave) curved edge of the second series of blades may have a larger radius of curvature than the outer (convex) edge. This may preferably be only slightly larger, for example in the ratio of 1.05:1. In preferable implementations, the radius of curvature of the convex edge of the first series of blades is equal to the radius of curvature of the concave edge of the second series of blades. By way of example, this may be 112.5 mm. Preferably, the concave edge of the first series of blades comprises a series of slots configured to engage with a series of slots on the convex edge of the second series of blades. Preferably, the first series of blades comprises on each blade a number of slots equal to the number of blades of the second series of blades, and the second series of blades comprises on each blade a number of slots equal to the number of blades of the first series of blades. In preferable implementations, each slot of the first series of blades is configured to engage with a slot on a different blade of the second series of blades and each slot of the second series of blades is configured to engage with a slot on a different blade of the first series of blades. That is to say, that, for each blade, each of the series of slots engages with a different blade of the other series of blades (i.e. the second series of blades or first series of blades, as appropriate). In some implementations, at least some of the series of blades comprises a protrusion at either end. Preferably all of the series of blades comprises a protrusion at either end. As used herein, the term ‘at either end’ preferably connotes at both ends. The ‘ends’ preferably refers to the location where the convex edge meets the concave edge. Preferably, the turbine further comprises a third series of blades, wherein the third series of blades are arranged in a circular formation perpendicular to a or the central axis of the turbine, to form the aperture. The third series of blades are preferably connected to at least one of the first and second series of blades. More preferably, the third series of blades are preferably connected to and moveable by at least one of the first and second series of blades. Preferably the third series of blades are fixedly connected to at least one of the first and second series of blades and the blades of the third series of blades are moveable relative to one another to thereby adjust the diameter of the aperture upon reversibly expanding or compressing the first and second series of blades. This can advantageously enable control of the size of the aperture. In some implementations, the blades of the third series of blades may have a radius of curvature equal to the radius of curvature of the convex edge of the first series of blades, and preferably equal to the radius of curvature of the concave edge of the second series of blades. The third series of blades are preferably configured as tear-shaped. The diameter of the third series of blades is preferably equal to the width from the apex and parallel to one straight edge. In some implementations, at least a portion of the series of blades are metal. In some implementations, a first portion of the series of blades are metal and a second portion are formed of an electrically insulating dielectric. The turbine may preferably further comprise an entrance structure and an exit structure, wherein the exit structure supports the aperture. The entrance structure and exit structure may be moveable relative to one another, thereby to expand or compress the turbine. In particular, the first series of blades and the second series of blades may change angle relative to one another (while remaining engaged via the slots). The expanding and compressing of the turbine preferably changes the size of the aperture. The entrance structure may further comprise a funnel. According to a further aspect, there is provided a system comprising a fuel source; an engine and the turbine as described above, in the description and figures, wherein the turbine is located between the fuel source and the engine such that fuel from the fuel source passes through the turbine to enter the engine. According to a further aspect, there is provided a system comprising an electromagnetic wave source and the turbine as described above, in the description and figures, wherein the electromagnetic wave source transmits an electromagnetic wave through the turbine. According to a further aspect, there is provided a system comprising a charged particle source and the turbine as described above, in the description and figures, wherein the charged particle source transmits a beam of charged particles through the turbine. The charged particle source may preferably comprise at least one discharge point. In some implementations, the system may further comprise a charge accumulator, preferably configured to receive charge from a series of charged particle sources. The invention extends to methods and / or apparatus substantially as herein described with reference to the accompanying drawings. Any apparatus feature as described herein may also be provided as a method feature, and vice versa. Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa. Furthermore, any, some and / or all features in one aspect can be applied to any, some and / or all features in any other aspect, in any appropriate combination. It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and / or supplied and / or used independently. Brief Description of the Figures One or more aspects will now be described, by way of example only and with reference to the accompanying drawings having like-reference numerals, in which: Figure 1 is an illustration of a turbine; Figure 2A shows a first component plate of the turbine of Figure 1; Figure 2B shows a second component plate of the turbine of Figure 1; Figure 2C shows a third component plate of the turbine of Figure 1; Figure 3 shows an end schematic view of an aperture formed by the turbine; Figure 4 shows the turbine in a first configuration; Figure 5A shows the turbine in a second configuration; Figure 5B shows an end schematic view of the aperture in a closed configuration; Figure 6 shows a schematic exemplary implementation of the turbine; Figure 7 shows a further exemplary implementation of the turbine; Figure 8 shows a yet further exemplary implementation of the turbine; Figure 9 shows an exemplary implementation the arrangement of Figure 8; Figure 10A shows a side view of a first implementation of a source and acceleration component configuration; Figure 10B shows an end view of the source and acceleration component configuration of Figure 10A; Figure 11A shows a side view of a second implementation of a source and acceleration component configuration; Figure 11B shows an end view of the source and acceleration component configuration of Figure 11A; Figure 12 shows a yet further exemplary implementation of the turbine; Figure 13 shows an exemplary arrangement of charge sources; Figure 14A shows an exemplary apparatus for facilitating arrangement of charge sources; and Figure 14B shows a cut-through perspective illustration of the apparatus of Figure 14A. Detailed Description Turbine Figure 1 shows a cross section of an assembled turbine 10. The turbine 10 is formed as a turbine comprising a series of interconnecting plates 12,14, each of which is positioned tangential to a central axis (C in Figure 1). The turbine shape comprises two types of plates: an outer plate 12 and an inner plate 14. The plates form the ‘blades’ of the turbine, and so will be referred to interchangeably as ‘blades’ and ‘plates’. In the preferable illustrated embodiment, there are a total of thirty blades forming the central body of the ‘turbine’ shape, fifteen of the outer plates 12 and fifteen of the inner plates 14. Figure 2A shows a plan view of an outer plate 12 and Figure 2B shows a plan view of an inner plate 14. The outer plates 12, as illustrated in Figure 2A, are formed as a crescent shape flat plate (typically having a thickness of a few millimetres, for example 0.3 to 3 mm). The outer (convex) curved edge of the crescent shape has a larger radius of curvature than the inner (concave) curved edge. Along the inner (concave) curved edge there is a series of slots 120. At the central portion, where the width of the overall crescent shape is greatest, the slots 120 extend to approximately one quarter to one third of the overall width of the plate 12, while at the ends, where the width is smallest, the slots extend to approximately half of the width. In the illustrated embodiment, there are fifteen of each type of plate, and -correspondingly - there are fifteen slots 120 in each plate 12. This is because each of the slots 120 is configured to receive an inner plate 14. At each of the two ends of the crescent shape of the outer plates 12, there is a tab 122 which extends approximately radially outwards from the main body of the plate 12. Adjacent each tab 122 and separated by the outermost slots 126 (so between the outermost slots 126 and the adjacent slots at each end) is a further projection 124 extending inwardly from the inner concave curved surface. The tabs 122 and projections 124 are configured to secure the engagement of the outer plates 12 and inner plates 14 to form the interconnected shape of the turbine 10. Additionally, there is a further formation 128 near the outer edge of the plate 12, typically near the centre of the main body of the plate 12. This further formation 128 is configured to facilitate attachment of the plate 12 to a spoke (not shown), which in turn is connected to an outer ring (again, not shown). Akin to a bicycle wheel, the spoke and outer ring can turn relative to the central axis, C; the attachment of the spoke to the plate 12 means that the turbine 10 can similarly be turned relative to the central axis, C. In the illustrated embodiment, the formation 128 is formed as an aperture having a circular section and a horizontal rectangular section joined by a horizontal rectangular section; however, the formation 128 may take other forms, which can also facilitate a secure connection between the plate 12 and at least one spoke. The inner plates 14, as illustrated in Figure 2B, are also formed as a crescent shape flat plate (typically having a thickness of a few millimetres, for example 0.3 to 3 mm). The inner (concave) curved edge has a larger radius of curvature than the outer (convex) edge. Preferably the inner curved edge has the same radius of curvature as the outer curved edge of the outer plates 12; this means that, when the turbine 10 is assembled, the outer edge of the outer plates 12 has the same radius of curvature as the inner edge of the inner plates 14. Along the outer (convex) curved edge of the crescent shape are a series of slots 140. Again, at the central portion, where the width of the overall crescent shape is greatest, the slots 140 extend approximately one quarter to one third of the overall width of the plate 14, while at the ends, where the width is smallest, the slots extend to approximately half of the width. Similarly, as the illustrated embodiment of the turbine 10 comprises fifteen inner plates 12 and fifteen outer plates 14, there are fifteen slots 140 on each of the inner plates 14. Each of the slots 140 are configured to receive one of the outer plates 12. At the ends of the crescent shape of each inner plate 14 there is a finger 146 projecting inwardly (at approximately a right angle to the surface of the inner concave edge at that location). These fingers 146 are configured to be connectable to a power energy and / or charge source, such as a capacitor. Alternatively, the connections via the fingers 146 facilitate discharge from the plates (for example, charge may accumulate in the case that the plate is moving through an electric field and / or as result of radiation passing through the turbine 10). One or both of the fingers 146 may be connected at the same time; and this connection may be by connected wires or, preferably, a commutator and / or brush arrangement at each end, which avoids difficulties of wires becoming tangled when the turbine 10 is spinning. Between the outermost slots 142 and the adjacent slots are outwardly extending projections 144. Optionally, the inner plates 14 also comprise a formation 148 configured to connect to a spoke, in a similar manner to that as described above in respect of the outer plate 12. The inner plates 14 and outer plates 12 are joined together by fitting the slots 122 and 142 together (i.e. within one another). Each of the set of slots 122 on each outer plate 12 is connected to a slot 142 on a different inner plate 12; and each of the set of slots 142 on each inner plate 14 is connected to a slot 122 on a different outer plate 12. In particular, the outermost slots 126 of the outer plates 12 engage with the outermost slots 142 of the inner plates 14. As these outermost slots 126, 142 on the two types of plates extend across approximately half the width of each plate in that region, this leads to a deep engagement of the slots and consequently the plates at the ends, helping to secure the connection. The security of the connection is enhanced by the projections 124 of the outer plates 12 and the projections 144 of the inner plates 14 both extending in a direction towards the connection point. This arrangement causes the outer plates 12 to be positioned tangentially to the central axis C in a first orientation and the inner plates to be positioned tangentially to the central axis C in a second orientation, and together they form an arrangement akin to a ‘basket-weave’ to form the turbine 10. The outer plates 12 and the inner plates 14 can be seen to ‘twist’ within the turbine in opposite directions. For example, twist in a clockwise direction can be referred to as ‘female’ and twist in an anti-clockwise direction as ‘male’. The turbine 10 is configured to be rotatable, the rotation being driven via spokes connecting the blades to a rotating outer ring. In some implementations, however, the turbine 10 can be used stationary. At a first end of the turbine 10, the tabs 122 of the outer plates are connected via support pins 22 to a plate 24 of an entrance aperture 20. The pins 22 hold the turbine 10 in position relative to the entrance aperture 20, through which a relevant stream or radiation beam passes to enter the turbine 10. There is typically further provided at this location a focuser 40, which is shaped as a funnel with the narrow end entering the turbine 10. At the opposite end of the turbine 10, the tabs 122 of the outer plates 12 are connected by support pins 36 to aperture plates 32 within an exit component 30. A plan view of the shape of the aperture plates 32 is shown in Figure 2C; the aperture plates 32 are a flat plate having a tear drop shape with a generally circular main body. Preferably the radius of curvature of the circular portion of the body of the aperture plates 32 is equal to the radius of curvature of the outer curved edge of the outer plates 12 and the inner curved edge of the inner plates 14. Each of the aperture plates 32 is positioned such that its flat surface is perpendicular to central axis C of the turbine 10. As the main body of the aperture plates 32 is positioned radially outwardly from the central axis C, it can be advantageous that the radius of curvature of the main body is equal to the curvature of the outer edge of the outer plates 12 and the inner edge of the inner plates 14. Figure 3 illustrates an end view of the aperture 30, looking down along the central axis C of the turbine 10. Each of the plates 32 is surrounded by and the supported by an iris 34 within an outer support ring 38. Each of the aperture plates 32 forms a segment of the exit aperture, defining the diameter A of the aperture. The ‘basket-weave’ arrangement of the turbine 10 means that the turbine is collapsible and expandable; this movement changes the positioning of the tabs 122 of the outer plates 12, which changes the relative positioning of the aperture plates 32 via the support pins 36. In this manner, the diameter A of the exit aperture can be adjusted. The turbine 10 can be collapsed to a fully flat arrangement i.e. the outer plates 12 and the inner plates 14 are all within the same plane. The basket-weave arrangement of the turbine 10 is further configurable such that it can be ‘flipped’ i.e. it can be collapsed and then expanded in the opposite direction. This has the effect that the set of outer plates 12 change the orientation with which they twist. Similarly, the inner plates 14 also change the orientation with which they twist. Figure 4 shows a first arrangement of the turbine 10 in a relatively ‘compressed’ or ‘collapsed’ state, in which the inner plates 14 and outer plates 12 are at a relatively large tangential angle to the central axis C. This configuration can be achieved by moving the exit component 30 closer to the entrance aperture 20 (or vice versa). In this configuration, the diameter of the exit aperture is relatively large, as is illustrated by the aperture diameter labelled A’ in Figure 4. In the extreme, the turbine 10 can be ‘collapsed’ to a fully compressed state, in which the inner plates 14 and outer plate 12 are at least very close to perpendicular to the central axis C (other connections permitting) and the entrance aperture 20 and exit component 30 are brought close to one another. Figure 5A shows a second arrangement of the turbine 10 in a relatively ‘expanded’ state, in which the tangential angle between the inner plates 14 and outer plates 12 to the central axis C is relatively small. This configuration can be achieved by moving the exit component 30 further away from the entrance aperture 20 (or vice versa). In this arrangement, the tabs 122 of the outer plates 12 are in relatively close proximity to one another, leading to the exit aperture having a relatively small diameter (as indicated by A” in Figure 5A). In the extreme, the turbine 10 can be ‘closed’ by extending it to such an extent that the aperture plates 32 of the exit aperture 30 come together, closing the aperture i.e. the diameter A of the aperture becomes zero. This is shown in Figure 5B, which illustrates an end view of the turbine, showing the aperture in a closed configuration. Such an arrangement can be used in, for example, a ramjet. The outer plates 12 and inner plates 14 are typically made of an electrically conducting material such as a metal, for example copper or tungsten. The plates are preferably annealed to improve the electrical conductivity; this can be achieved by a heating anneal process followed by quenching in Argon. The outer plates 12 and the inner plates 14 are electrically insulated from one another. There are typically provided electrically insulating dielectric components (e.g. ‘inserts’) at the point of the connection between the outer plates 12 and inner plates 14, for example made of a ceramic material, which can act to insulate the outer plates 12 from the inner plates 14. In some implementations, however, some of the blades are made of a dielectric material, for example a ceramic or a polycarbonate. By way of example, adjacent blades may alternate between metal and dielectric; outer blades 12 may be metal and inner blades 14 dielectric, or vice versa, etc. The pins 22, 36 connecting and supporting the blades are comprised of or coated in an electrically insulating material. The aperture plates 32 and / or the focuser 40 are typically made of a dielectric material such as polycarbonate; this can aid in focusing the stream of material such as a fuel mixture, while not hindering the passage of radiation waves. An arrangement in which the turbine 10 can be ‘flipped’ can be advantageous for enabling the properties of the turbine to be altered. ‘Flipping’ the blade arrangement of the turbine 10 changes the ‘twist’ of the outer blades 12 and the inner blades 14, this can be used to alter the performance of the turbine 10. For example, altering the direction of the blades can cause a vortex of air (or other gas) created by the movement of the blades to be formed in the other orientation (i.e. the opposite direction of rotation). In implementations in which the blades comprise a combination of electrically conducting and electrically insulating materials, flipping the orientation of the blades can alter the electrical properties of the turbine 10. For example, the outer blades 12 may be electrically conducting and the inner blades 14 electrically insulating, and flipping the turbine 10 means the outer blades 12 are arranged in the opposite orientation (i.e. opposite direction of twist). In order to facilitate the turbine 10 being able to be flipped to the opposite orientation, the connections via the via support pins 22 to a plate 24 of an entrance aperture 20 and the connections via support pins 36 to the exit component 30 can be configured to be disconnectable and reconnectable (i.e. reversibly connectable). Furthermore, the spokes may be connected to and moveable over an arc-shaped outer shape (for example a sphere) to facilitate the full range of movement of the plates. In use, the turbine 10 may be stationary or it may be rotated. The particular implementation is typically dependent on the environment in which the turbine 10 is being used. For example, if being used in water or on land, then the turbine 10 is typically used spinning / rotating. If the turbine 10 is used in a low-pressure atmosphere, for example in space, then the turbine 10 is typically used stationary / static. At atmospheric pressure, the turbine 10 may be used in a spinning or stationary manner. The outer plates 12 and the inner plates 14 are both positioned tangentially to the central axis C, but at different orientations. If the turbine 10 is rotated, the outer blades 12 and the inner blades 14 cause any gas (such as air) to be moved at a tangential direction, forming a vortex. Different arrangements of the turbine 10 (e.g. the extent to which the blades 12, 14 are extended or compressed) lead to different air flows through the turbine 10 as well as different diameters A of the exit aperture. The arrangement and movement of the turbine 10 and of the surrounding components can determine whether air is moved outwards or inwards when rotated. Typically, the ratio of volume between the outer edges of the outer plates 12 and between the inner edges of the inner plates 14 is 5:1; this can mean, depending on the arrangement, the gas can be compressed or expanded by movement inwards or outwards, caused by rotation of the plates. If the air is moved outwards, the vortex flow creates a vacuum within the central axis C of the turbine 10, the size of which can be controlled by the extension or compression of the turbine 10. This vacuum can be utilized to draw in and compress fuel and air mixtures. The extent of expansion or compression of the turbine 10 can control the extent of compression of a fuel mixture and the width of the exiting stream. In other implementations, the turbine 10 can be used to compress air, which can give rise to a vortex within the centre, around the central axis C. Alternatively, the turbine 10 can be used simply as effective cooling through moving gas, such as air. Furthermore, when the turbine 10 is rotated, the electrically conducting plates form an effective waveguide for radiation waves passing through. As the shape of the turbine 10 tapers from the entrance aperture 20 to the exit component 30, the waveguide can focus (i.e reduce divergence) of the beam of such radiation waves. Characteristics of the waveguide are altered by different combinations of electrically conducting and insulating blades. The focus and / or width of the exiting wave can be altered by altering the size of the aperture A, which is achieved by extending or compressing the turbine 10 (by moving the entrance aperture 20 and the exit component 30 relative to one another). The combination of concentrating fuel mixtures and focusing radiation waves to a concurrent point can advantageously provide a means of providing enhanced efficiency turbine engines. Alternatively, the control of gas (such as air) by the turbine 10 can be used simply to provide effective cooling to devices utilizing focused radiation beams. Exemplary systems An overview of exemplary systems in which the turbine 10 may be implemented are provided below. Figure 6 shows a simple schematic system implementing the turbine 10. This comprises a fuel source 50 (typically comprising a mixture of fuel and oxygen) which is passed through the turbine and condensed, to then pass out from the turbine 10 through the exit aperture. In particular, the fuel mixture passes from the fuel source 50 in to and through the entrance aperture 20. It is drawn in this direction and into the turbine 40 due to the vacuum created within the central cavity of the turbine 40 by the rotational movement of the blades 12, 14 creating a vortex. The fuel mixture then passes through the focuser 40, which acts as a first step of focusing the jet of fuel mixture. It then passes through the central cavity of the turbine 10, the vortex within which further acts to focus the supply jet. The jet then passes out through the exit aperture of the exit component 30 as a focused jet, and onto where it is to be used. The extent to which the jet is focused, and consequently the speed with which it exits the exit aperture, can be controlled by the configuration of the turbine (the extent to which it is compressed or extended). The rotational movement of the blades 12, 14 can further assist in cooling the system and thereby keeping temperatures low. It can be advantageous to keep temperatures low in the turbine 10 so as to prevent or at least minimize thermal fatigue of the metal. This can help to ensure that the system remains functional for a longer time period. Figure 7 shows how the system of Figure 6 may be incorporated into a larger device. In this case, the condensed fuel mixture exits the turbine 10 and then enters an engine 120, in which it can be combusted. In some optional implementations, an outer turbine fan 130 may be provided to assist in cooling the air around the turbine 10. In this implementation, the turbine 10 acts as an effective and efficient throttle for the engine 120. The compression and focus of the fuel mixture can increase burn efficiency. The extendable and compressible arrangement of the turbine 10 advantageously means that the fuel mixture speed and compression is adjustable. Figure 8 shows a further simple schematic system implementing the turbine 10, as it can be used for guiding and focusing a radiation beam. This system comprises a radiation source 60, from which a beam of radiation extends and enters the turbine 10. The radiation beam may, for example, be an electromagnetic wave such as microwaves or it may be a stream of charged particles. The beam enters the entrance aperture 20 and passes through the turbine 10. The conducting (e.g. metal) blades of the turbine 10 create an effective waveguide, typically gently tapering and therefore focusing the beam. The extent of the tapering and the width of the exiting beam is determined by the configuration of the turbine 10 (i.e. the extent to which it is compressed or extended). The particular configuration of the turbine 10 may typically be chosen in dependence on the properties of the relevant radiation, for example wavelength. Figure 9 shows an exemplary system for exciting a beam of charged particles, which are then transmitted through the turbine. The system comprises at least one capacitor bank 70, which is chargeable by external devices. In typical implementations, eight capacitor banks may be used but this can of course be varied according to each use case. The capacitor bank 70 is connected to a first charge distributor 80A, which is located adjacent to a second charge distributor 80B. These charge distributors 80A, 80B are formed of a conductor surrounded by an insulating layer, for example metal surrounded by silicon carbide. The second charge distributor 80B is in connection with a charged particle source 90 and collector 100. The charged particle source 90 arrangement comprises a series of charge generators 92 provided on frame 94 extending from a central column 96. The central column 96 runs along the central axis and has an insulating outer layer, from which the frame 94 extends generally radially outwards. The frame 94 typically comprises a series of extending arms 942 which each carry at least one holder 944 for holding a charge generator 92. Each charge generator 92 as illustrated comprises a sphere 922 located on one end of a shank 924, the other end of the shank 924 having a pointed end 926. The sphere 922 is not essential, and in some embodiments, the generator 92 may be formed in a different arrangement without the sphere 922. The shank 924 is approximately parallel to the central axis C of the turbine 10, and in the illustrated embodiment the spheres 922 are located at the end closest to the turbine 10. The charge generators 92 are typically in connection with the capacitor bank 70 and / or the charge distributors 80A, 80B, which create a voltage in the charge generators 92. When the voltage is sufficiently high, discharge (e.g. Corona discharge or brush discharge) occurs from the pointed end 426. The opposite end being formed as a sphere 922 can be beneficial as it can prevent discharge from occurring at that end, and so it occurs preferentially at the pointed end 426. In some implementations, the charge generators 92 may be Van der Graaf generators, and the spheres 922 of the Van der Graaf generators comprise ion sources. In such a case, the field of the Van der Graaf generator 92 accelerates the charged particles away from the sphere 922. The pointed end 926 of the shank 924 acts as a point for discharge, which directs the charged particles along a line approximately perpendicular to the central axis C and in a direction away from the turbine 10. The charged particles accelerated by the series of charge generators 92 are directed towards an electrically conductive disc 100, typically made of copper and located between the charged particle source 90 and the charge distributors 80A, 80B. This leads to an accumulation of charge on the disc 100, the disc therefore acting as a charge accumulator. The disc 100 is in connection with an electrically conducting central component within the central column 96, which can conduct the charge. Typically, the movement of charge is enhanced by placing the central column 96 within an electric field. At the end of the central column 96 furthest from the disc 100 and adjacent the turbine 10 is a pointed tip 98. The concentration of charge on the tip 98 can lead to ionization of the gas creating charge particles which are then repelled in a stream away from the tip 98, passing into the turbine 10. In order to maximize the charge accumulated on the disc 100, it can be beneficial to arrange the charge generators 92 in a manner which provides good spatial efficiency; in other words, that they are well spread out, but all have a direct clear line to the disc 100. This is typically achieved by spatial arrangement and / or typically there is relative rotation between the disc 100 and the holders 94 (and so also the charge generators 92 held by the holders 94) to enhance the spread of charge. Figures 10A and 10B illustrate a first exemplary arrangement for achieving this and Figures 11A and 11B illustrate a second exemplary arrangement. The relative rotation of the disc 100 and the holders 94 further means that, soon after a stream of charged particles hits the disc 100, a different portion of the disc 100 then becomes aligned with the relevant holder 94. It is sufficient that there is relative motion between the disc 100 and the holders 94, i.e. only one may need to be rotating. However, it is typically preferable that the disc 100 rotates in a first direction and the holders 94 rotate in the opposite direction, as this can mean that each holder 94 is aligned with a greater spread of portions of the disc 100 over a particular time interval. Figures 10A and 10B illustrate an arrangement in which the central column 96 comprises three sections, which each carry a set of two holders 94. As such, the holders 94 are distributed along the central column 96, as can be seen in the schematic illustration of Figure 10A. The holders 94 are then preferably distributed around the axis B of the column 96, as can be seen in Figure 10B. In this illustrated embodiment, each of the holders 94 carries two generators 92. Overall, the generators 92 are positioned on the holders 94 at different radial distances from the axis B. Figures 11A and 11B show an alternative arrangement of the charged particle source components 90. In this implementation, again the central column 96 comprises three sections, which each carry a set of holders 94. However, in this configuration the holders 94 have different configurations. Some holders comprise simply an arm 942 which carries a single charge generator 92. One layer of charge generators 92 however are held on a plate 946. Again, the generators 92 are distributed around the axis B at different angles and different radial distances; this can provide good distribution across the surface area of the disc 100. Figure 10A, 10B, 11A and 11B only show representative possible arrangements; of course, different numbers of holders 94 and generators 92 may be used in different configurations. Figure 12 shows a further exemplary system, which, in addition to and adjacent to the electrically conductive disc 100, comprises a further electrically conductive disc 102. This further disc 102 provides further capacity for charge accumulation. Typically, the disc 100 and the further disc 102 are electrically connected, but in some implementations they may be electrically insulated from one another, such that sparks occur (e.g. via arc or spark discharge) between the disc 100 and the further disc at sufficient charge levels. In some implementations, a shield (not illustrated) is further provided so that the sparks can be stopped when desired. By way of example, the shield may be formed of an electrically insulating material (i.e. having high dielectric strength) and be insertable between the disc 100 and further disc 102 and reversibly removeable. As a further example, the shield may comprise intermittent apertures, which can be rotated such that a particular region can be shielded or exposed as desired. In some implementations (not illustrated), there may further be provided a laser which causes a laser beam to be alternatively or additionally transmitted along the central axis C. For example, this can provide energy to a system, such as a system for combustion of a condensed fuel mixture beyond the turbine 10. Alternatively (or additionally), the turbine 10 can further be used to collimate the laser light, again this can be controlled by adjusting the extension or compression of the turbine 10. Charge source arrangement Figure 13 illustrates an arrangement for directing a stream of charged particles, such as those passed through a turbine 10 as described above. In particular, Figure 13 illustrates four sources of different charges, S1 to S4, arranged around and directed towards a single point. Each of the sources S1 to S2 are arranged approximately 90 degrees to one another. The first source S1 and the second source S2 are located adjacent to one another (i.e. 90 degrees to one another) and both emit positive charge. The third source S3 and the fourth source S4 are located adjacent to one another (i.e. 90 degrees to one another) and opposite to sources S1 and S2 (i.e. S3 is 180 degrees from the first source S1 and 90 degrees from the second source S2; and S4 is 180 degrees from the second source S2 and 90 degrees from the first source S1). Both the third source S3 and fourth source S4 emit negative charge. Arranging the charges in this quadrature configuration and directing them all to a single point can advantageously create a high-energy spark at that central point. Figures 14A and 14B illustrate an exemplary apparatus which helps to facilitate the charge source arrangement as illustrated in Figure 13 and described above. In particular, Figure 14a shows a schematic top-view, which includes line A-B across the centre of the apparatus 1000. Figure 14b shows a schematic cross-sectional view, on which the line A-B is indicated for reference. The apparatus 1000 comprises four ports 1002, 1004, 1006 and 1008, which are configured to receive the four charge sources, S1 to S4. The apparatus 1000 is formed as a sphere, and the four ports 1002, 1004, 1006 and 1008 are located evenly around the diameter of the sphere (i.e. they are 90 degrees apart from one another). Simply by way of example, the first source S1 may be located at the first port 1002, the second source S2 located at the second port 1004, the third source S3 located at the third port 1006, and the fourth source S4 located at the fourth port 1008. Between each of the ports 1002, 1004, 1006 and 1008 and a central cavity 1010 there are provided channels 1012, 1014, 1016, 1018 along which the charge can travel. The charge can then meet at the central point located within the central cavity 1010. Alternatives and modifications In some implementations, the turbine may have a number different to fifteen of each type of blade, and then - consequently - that same number of slots in each of the outer blades 12 and inner blades 14. Simply by way of example, there may be ten inner blades 14, ten outer blades 12 and ten aperture plates 32; in such a case each of the inner blades 14 comprise ten slots 142 and each of the outer blades 12 comprise ten slots 126. Preferably the numbers of each type of blade are equal, but in some embodiments there may be a greater number of inner or outer blades. The number of slots on one type of blade (inner or outer) preferably corresponds to the number of the other type of blade (inner or outer). The number of aperture plates 32 typically corresponds to the number of the blade type to which they are attached (for example, the outer blades); however, in some cases the aperture plates 32 may be connected to every other or every third etc. outer or inner blade; in such a case the number of aperture plates 32 will not equal the number of the other type(s) of plates / blades. In some implementations, a Van der Graaf generator may be used in a simpler arrangement to accelerate charge particles in directly towards the turbine 10, without the additional component of the disc 100. Other methods of propagating charged particles or electromagnetic radiation waves, as are well known, may also of course be used. In order to alter the extension and compression of the turbine, the exit component 30 and entrance aperture 20 must be moveable relative to one another along the central axis C. Typically, only the exit component 30 is moveable while the entrance aperture 20 has a fixed location. However, in some implementations both components may be moveable. Alternatively, the outer support ring 38 of the exit component 30 may be fixed, while the entrance aperture is moveable along the central axis C towards and away from (this causing movement of the aperture blades 32 within the outer support ring 38). As mentioned previously, the turbine 10 may be implemented as part of a ramjet. The turbine 10 can expand to make the aperture of the exit component 30 close completely (i.e. aperture A goes to zero, as illustrated in Figure 5B), and then be compressed such that the aperture opens up again, allowing air through and providing thrust. 5 In a further implementation, the turbine 10 can be used as a static mixer. In particular, in such an implementation, the turbine 10 can be held stationary, for example, in a liquid such as water. The opposing twists of the outer blades 12 and inner blades can cause effective mixing of a stream of liquid passing through the turbine 10. It can further create a vortex in the fluid flow, akin to stirring a liquid. io It should be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention. Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination. Reference numerals appearing in the claims are by way of illustration only and shall have 15 no limiting effect on the scope of the claims.

Claims

1. A turbine comprising a series of blades and an aperture, wherein the series of blades is reversibly expandable and compressible and wherein a diameter of the aperture is adjustable by reversibly expanding or compressing the series of blades.

2. The turbine of claim 1, wherein the blades of the series of blades are positioned tangentially to a central axis of the turbine.

3. The turbine of claim 1 or 2, wherein the blades have a crescent shape and are arranged such that the convex edges are positioned radially distal from a or the central axis of the turbine.

4. The turbine of any preceding claim, wherein the series of blades comprises a first series of a first blade form and a second series of a second blade form.

5. The turbine of claim 4, wherein the first series of blades engages at an angle with the second series of blades to form the turbine.

6. The turbine of claim 4 or 5, wherein the first series of blades are located at a greater radial distance from a or the central axis of the turbine than the second series of blades.

7. The turbine of claim 6 when dependent on claim 3, wherein the radius of curvature of the convex edge of the first series of blades is equal to the radius of curvature of the concave edge of the second series of blades.

8. The turbine of claim 6 or 7 when dependent on claim 3, wherein the concave edge of the first series of blades comprises a series of slots configured to engage with a series of slots on the convex edge of the second series of blades.

9. The turbine of claim 8, wherein the first series of blades comprises on each blade a number of slots equal to the number of blades of the second series of blades, and the second series of blades comprises on each blade a number of slots equal to the number of blades of the first series of blades.

10. The turbine of claim 8 or 9, wherein each slot of the first series of blades is configured to engage with a slot on a different blade of the second series of blades and each slot of thesecond series of blades is configured to engage with a slot on a different blade of the first series of blades.

11. The turbine of claim 5 or any of claims 6 to 10 when dependent on claim 5, wherein at least some of the series of blades comprises a protrusion at either end.

12. The turbine of any preceding claim, further comprising a third series of blades, wherein the third series of blades are arranged in a circular formation perpendicular to a or the central axis of the turbine, to form the aperture.

13. The turbine of claim 12, wherein the third series of blades are connected to at least one of the first and second series of blades.

14. The turbine of claim 13, wherein the third series of blades are fixedly connected to at least one of the first and second series of blades and the blades of the third series of blades are moveable relative to one another to thereby adjust the diameter of the aperture upon reversibly expanding or compressing the first and second series of blades.

15. The turbine of any of claims 12 to 14, wherein the blades of the third series of blades have a radius of curvature equal to the radius of curvature of the convex edge of the first series of blades, and preferably equal to the radius of curvature of the concave edge of the second series of blades.

16. The turbine of any preceding claim, wherein at least a portion of the series of blades are metal.

17. The turbine of claim 16, wherein a first portion of the series of blades are metal and a second portion are formed of an electrically insulating dielectric.

18. The turbine of any preceding claim, further comprising an entrance structure and an exit structure, wherein the exit structure supports the aperture.

19. The turbine of claim 18, wherein the entrance structure and exit structure are moveable relative to one another, thereby to expand or compress the turbine.

20. The turbine of claim 18 or 19, wherein the entrance structure further comprises a funnel.

21. A system comprising a fuel source; an engine and the turbine of any of claims 1 to 20, wherein the turbine is located between the fuel source and the engine such that fuel from the fuel source passes through the turbine to enter the engine.

22. A system comprising an electromagnetic wave source and the turbine of any of claims 1 5 to 20, wherein the electromagnetic wave source transmits an electromagnetic wave through the turbine.

23. A system comprising a charged particle source and the turbine of any of claims 1 to 20, wherein the charged particle source transmits a beam of charged particles through the turbine.io 24. The system of claim 23, wherein the charged particle source comprises at least one discharge point.

25. The system of claim 23 or 24, further comprising a charge accumulator, preferably configured to receive charge from a series of charged particle sources.

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