Electrical machine

Abstract

An axial flux electrical machine comprises a first flux generating assembly, a second flux generating assembly, a shaft and a speed controller. The shaft has an axis of rotation. Each of the first flux generating assembly and the second flux generating assembly is rotationally located on the shaft in axial juxtaposition to one another, with the first flux generating assembly being axially separated from the second flux generating assembly by a separation distance. The speed controller is configured to modify a magnetic field generated by either of the first flux generating assembly and the second flux generating assembly so as to control a rotational speed of the electrical machine.

Claims

1. An axial flux electrical machine comprising: a first flux generating assembly; a second flux generating assembly; a shaft having an axis of rotation; and a speed controller, wherein each of the first flux generating assembly and the second flux generating assembly is rotationally located on the shaft in axial juxtaposition to one another, the first flux generating assembly being axially separated from the second flux generating assembly by a separation distance, and the speed controller being configured to modify a magnetic field generated by either of the first flux generating assembly and the second flux generating assembly so as to control a rotational speed of the electrical machine; and wherein the speed controller comprises a control plate, the control plate being configured to generate a control magnetic field in opposition to a first magnetic field generated by the first flux generating assembly.

2. The axial flux electrical machine as claimed in claim 1, wherein the first flux generating assembly comprises one or more winding portions and the second flux generating assembly comprises one or more magnetic portions, the one or more winding portions corresponding to a respective one of the one or more magnetic portions.

3. The axial flux electrical machine as claimed in claim 1, wherein the first flux generating assembly comprises a plurality of first flux generating portions, and the second flux generating assembly comprises a plurality of second flux generating portions, the plurality of first flux generating portions comprises an alternating circumferential array of magnetic portions and winding portions, and the plurality of second flux generating portions comprises an alternating circumferential array of magnetic portions and winding portions.

4. The axial flux electrical machine as claimed in claim 1, wherein the first flux generating assembly comprises a plurality of first flux generating portions, and the second flux generating assembly comprises a plurality of second flux generating portions, each of the plurality of first flux generating portions being the same and being selected from the group consisting of induction machine portions, permanent magnet portions, synchronous wound field portions and switched reluctance portions, and each of the plurality of second flux generating portions being the same and being selected from the group consisting of induction machine portions, permanent magnet portions, synchronous wound field portions and switched reluctance portions.

5. The axial flux electrical machine as claimed in claim 1, wherein the control plate is positioned adjacent to the first flux generating assembly.

6. The axial flux electrical machine as claimed in claim 1, wherein the control plate is positioned between the first flux generating assembly and the second flux generating assembly.

7. An axial flux electrical machine comprising: a first flux generating assembly; a second flux generating assembly; a shaft having an axis of rotation; and a speed controller, wherein each of the first flux generating assembly and the second flux generating assembly is rotationally located on the shaft in axial juxtaposition to one another, the first flux generating assembly being axially separated from the second flux generating assembly by a separation distance, and the speed controller being configured to modify a magnetic field generated by either of the first flux generating assembly and the second flux generating assembly so as to control a rotational speed of the electrical machine, wherein the speed controller comprises a control portion and an actuating portion, the actuating portion being configured to axially move the first flux generating assembly relative to the second flux generating assembly to thereby change the separation distance, in response to a control signal generated by the control portion.

8. A propulsion system comprising: a machine body having an upstream end and an opposite downstream end; an axial flux electrical machine comprising: a first flux generating assembly; a second flux generating assembly; a shaft having an axis of rotation; and a speed controller, wherein each of the first flux generating assembly and the second flux generating assembly is rotationally located on the shaft in axial juxtaposition to one another, the first flux generating assembly being axially separated from the second flux generating assembly by a separation distance, and the speed controller being configured to modify a magnetic field generated by either of the first flux generating assembly and the second flux generating assembly so as to control a rotational speed of the electrical machine; a plurality of first fan blades arranged in a circumferential array around an outer circumference of the first flux generating assembly; and a plurality of second fan blades arranged in a circumferential array around an outer circumference of the second flux generating assembly, wherein the axial flux electrical machine is positioned at the downstream end of the machine body such that a fluid flow passing over the machine body, from the upstream end to the downstream end, is successively drawn through the first fan blade array and the second fan blade array to thereby entrain the flow passing over the surface of the machine body and thereby to accelerate the flow.

9. The propulsion system as claimed in claim 8, wherein the machine body is an aircraft.

10. A method of controlling a rotational speed of an axial flux electrical machine, the method comprising the steps of: providing a first rotatable flux generating assembly and a second rotatable flux generating assembly; positioning the first rotatable flux generating assembly and the second rotatable flux generating assembly in axial juxtaposition on a shaft; providing excitation energy to one of the first rotatable flux generating assembly and the second rotatable flux generating assembly; and using a speed controller to vary a magnetic field generated by one of the first flux rotatable generating assembly and the second rotatable flux generating assembly, thereby controlling the rotational speed of the electrical machine, by: positioning a control plate adjacent to the first flux rotatable generating assembly; generating a control magnetic field from the control plate, the control magnetic field being in opposition to a first magnetic field generated by the first rotatable flux generating assembly; and varying the control magnetic field in response to a user input, thereby controlling the rotational speed of the electrical machine.

11. The method as claimed in claim 10, wherein the step of positioning the control plate adjacent to the first rotatable flux generating assembly comprises the step of: positioning the control plate between the first rotatable flux generating assembly and the second rotatable flux generating assembly.

12. A method of controlling a rotational speed of an axial flux electrical machine, the method comprising the steps of: providing a first rotatable flux generating assembly and a second rotatable flux generating assembly; positioning the first rotatable flux generating assembly and the second rotatable flux generating assembly in axial juxtaposition on a shaft; providing excitation energy to one of the first rotatable flux generating assembly and the second rotatable flux generating assembly; and using a speed controller to vary a magnetic field generated by one of the first flux rotatable generating assembly and the second rotatable flux generating assembly, thereby controlling the rotational speed of the electrical machine; wherein the first rotatable flux generating assembly is axially separated from the second rotatable flux generating assembly by a separation distance, and the step of using the speed controller to vary a magnetic field generated by one of the first rotatable flux generating assembly and the second rotatable flux generating assembly, comprises the steps of: providing a control portion that generates a control signal in response to a user input; and providing an actuating portion that is configured to axially move the first rotatable flux generating assembly relative to the second rotatable flux generating assembly to thereby change the separation distance, in response to the control signal, the change in separation distance resulting in a change to a magnetic field generated by one of the first rotatable flux generating assembly and the second rotatable flux generating assembly, thereby controlling the rotational speed of the electrical machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There now follows a description of an embodiment of the disclosure, by way of non-limiting example, with reference being made to the accompanying drawings in which:

(2) FIG. 1 shows a schematic part-sectional view of an axial flux electrical machine according to a first aspect of the disclosure;

(3) FIG. 2 shows a schematic part-sectional view of a boundary layer propulsion system according to a second aspect of the disclosure;

(4) FIG. 3 shows a schematic cross-sectional view of a an axial flux electrical machine according to a first aspect of the disclosure; and

(5) FIGS. 4A to 4D show schematic views of a mechanical actuator providing the relative axial movement between the first and second flux generating assemblies;

(6) FIGS. 5A to 5D show schematic views of a hydraulic actuator providing the relative axial movement between the first and second flux generating assemblies;

(7) FIG. 6 shows an elevational view of an aircraft comprising a boundary layer propulsion system according to the second aspect of the disclosure; and

(8) FIG. 7 shows an alternative arrangement of FIG. 6.

(9) It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

(10) Referring to FIGS. 1 to 3, 4A to 4D, and 5A to 5D, an axial flow electrical machine according to a first embodiment of the disclosure is designated generally by the reference numeral 100, and a boundary layer propulsion system according to a second embodiment of the disclosure is designated generally by the reference numeral 200.

(11) In the following description, the boundary layer propulsion system 200 is described in the context of an aircraft propulsor. However, the boundary layer propulsion system 200 may equally be applied to a marine vessel propulsor, an underwater vessel or another arrangement in which a body is to be propelled through a fluid.

(12) The axial flow electrical machine 100 comprises a first flux generating assembly 110, a second flux generating assembly 120, a shaft 130, and a speed controller 140.

(13) The first flux generating assembly 110 and the second flux generating assembly 120 are mounted co-axially in axial sequence on the shaft 130. The first flux generating assembly 110 and the second flux generating assembly 120 are in axial juxtaposition to one another. The first flux generating assembly 110 is rotationally mounted on a bearing assembly 116. The second flux generating assembly 120 is rotationally mounted on a bearing assembly 126.

(14) The speed controller 140 is arranged to modify a magnetic field that is generated by either of the first flux generating assembly 110 or the second flux generating assembly 120 to thereby control a rotational speed of the electrical machine 100.

(15) In the context of the present disclosure, the axial flux electrical machine 100 comprises two free rotating elements, namely the first and second flux generating assemblies 110,120. Consequently, in operation the first and second flux generating assemblies 110,120 will rotate in opposite directions to one another. In other words, the first and second flux generating assemblies 110,120 will contra-rotate.

(16) In the present arrangement the first flux generating assembly 110 comprises a plurality of windings 114 in the form of a repeating circumferential array of first coils 114A, second coils 114B, and third coils 114C. The second flux generating assembly 120 is formed as an induction cage 124A.

(17) This structure of the first and second flux generating assemblies 110,120 is illustrated in FIG. 3. The left hand view of FIG. 3 (Section A-A) is a sectional view looking forwards (or upstream) onto the first flux generating assembly 110. Likewise, the right hand view of FIG. 3 (Section B-B) is a sectional view looking rearwards (or downstream) onto the second flux generating assembly 120.

(18) In the arrangement of FIG. 1, the speed controller 140 is a control plate 142 that is configured to generate a magnetic field that can combine additively or subtractively with the magnetic field that is generated by the first flux generating assembly 110 to modify the rotational speed of the electrical machine 100.

(19) In an alternative arrangement (not shown) the control plate 142 may be positioned between the first flux generating assembly 110 and the second flux generating assembly 120. In this alternative arrangement, the control plate 142 may be configured to modify the magnetic field that is generated by either or both of the first flux generating assembly 110 and the second flux generating assembly 120.

(20) A further alternative technique for modifying the magnetic field that is generated by either of the first flux generating assembly 110 or the second flux generating assembly 120 is to vary the axial separation distance 136 between the first flux generating assembly 110 and the second flux generating assembly 120.

(21) FIGS. 4A to 4D illustrate a first scheme for varying the separation distance 136 between the first and second flux generating assemblies 210,220. A control portion 246 is connected to an actuation portion 248. The control portion 246 generates a control signal dependent upon the desired change in rotational speed of the axial flux electrical machine 110. This control signal passes to the actuating portion 248 to cause a change in the separation distance 136, and hence a change in the rotational speed of the axial flux electrical machine 100.

(22) As shown in FIG. 4A, the first flux generating assembly 210 is positioned on a static bearing unit 248E that is fixed to a static anchor 248A. This allows the first flux generating assembly 210 to rotate but constrains it axially.

(23) The second flux generating assembly 220 is located by a rotor positioning screw 248B that is concentric with the static bearing unit 248E. The second flux generating assembly 220 is positioned on a sliding bearing unit 248F, which enables the second flux generating assembly 220 to rotate about the same axis as the first flux generating assembly 210.

(24) In addition, the first flux generating assembly 210 and the second flux generating assembly 220 are located on guide elements 248D. The guide elements 248D ensure that the relative movement of the first and second flux generating assemblies 210,220 is precisely co-axial.

(25) Rotation of the rotor positioning screw 248B in a first direction as shown in FIG. 4A results in the separation distance 136 being increased as shown in FIG. 4B. This increase in the separation distance 136 will decrease the magnetic field interaction between the first and second flux generating assemblies 210,220 and hence will decrease the rotational speed of both the first and second flux generating assembles 210,220.

(26) Conversely, rotation of the rotor positioning screw 248B in an opposite second direction as shown in FIG. 4C results in the separation distance 136 being reduced as shown in FIG. 4D. This reduction in the separation distance 136 will increase the magnetic field interaction between the first and second flux generating assemblies 210,220 and hence will increase the rotational speed of both the first and second flux generating assembles 210,220.

(27) An alternative second scheme for varying the separation distance 136 between the first and second flux generating assemblies 110,120 is illustrated in FIGS. 5A to 5D. As outlined above, a control portion 346 is connected to an actuating portion 348 to cause a change in the separation distance 136.

(28) As shown in FIG. 5A, the first lux generating assembly 310 is mounted on a static bearing unit 348E. In this arrangement, the static bearing unit is axially fixed to a hydraulic ram cylinder 348A. In this way, the first flux generating assembly 310 is free to rotate but is axially constrained.

(29) The second flux generating assembly 320 is attached to a ram cylinder 348B and is axially secured by an end flange 348C. The second flux generating assembly 320 is positioned on a sliding bearing unit 348F. In this way, as the ram cylinder 348B translates axially, the second flux generating assembly 320 is able to freely rotate co-axially with the first flux generating assembly 310.

(30) FIGS. 4A to 4D and FIGS. 5A to 5D illustrate two techniques for varying the separation distance 136 between the first and second flux generating assemblies 110,120. The skilled person will appreciate that any further alternative arrangement for varying this separation distance 136 may be used.

(31) Referring to FIGS. 2 and 3, a boundary layer propulsion system according to a second embodiment of the disclosure is designated generally by the reference numeral 200. Features of the boundary layer propulsion system 200 which correspond to those of the axial flow electrical machine 100 have been given corresponding reference numerals for ease of reference.

(32) The boundary layer propulsion system 200 has an axial flux electrical machine 100 that is positioned in a tail section of a fuselage 210 of an aircraft (not shown completely). The fuselage 210 has an upstream end 212 and an opposite downstream end 214. The axial flus electrical machine 100 is positioned at the downstream end 214 of the fuselage 210.

(33) In this arrangement, the first flux generating assembly 110 is positioned upstream of the second flux generating assembly 120, with the speed controller 140, in the form of a control plate 142, being positioned upstream of the first flux generating assembly 110.

(34) As outlined above, in an alternative configuration the speed controller 140 may take the form of a mechanical system (illustrated in FIGS. 4A to 4B) or a hydraulic system (illustrated in FIGS. 5A to 5B).

(35) The first flux generating assembly 110 has an outer circumference 112. Arranged around this outer circumference 112 in a circumferential array is a plurality of first fan blades 220. Each first fan blade 220 is secured to the outer circumference 112 by means of a first blade attachment point 222.

(36) Likewise, the second flux generating assembly 120 has an outer circumference 122. Arranged around this outer circumference 122 in a circumferential array is a plurality of second fan blades 230. Each second fan blade 230 is secured to the outer circumference 122 by means of a first blade attachment point 232.

(37) In the present arrangement the first and second blade attachment points 222,232 are formed with a pyriform cross-sectional profile. In an alternative arrangement, the first and second blade attachment points 222,232 may be formed with a fir tree cross-sectional profile or another cross-sectional profile suitable for fan blade retention.

(38) In use the contra-rotation of the first and second fan blades 220,230 draws an air flow 240 therethrough, whilst also entraining a boundary layer flow 242 passing over the surface 216 of the fuselage 210.

(39) FIG. 6 shows an aircraft 302 comprising a boundary layer propulsion system 200 that has been mounted at the tail of the fuselage of the aircraft. The boundary layer propulsion system 200 comprises a downstream array of first fan blades 220 axially adjacent to an upstream array of second fan blades 230. In the arrangement of FIG. 6, the first fan blades 220 are the same as the second fan blades 230.

(40) FIG. 7 shows an alternative arrangement of an aircraft 310 comprising a tail-mounted boundary propulsion system 200. In the arrangement of FIG. 7 the first fan blades 220 have a larger diameter than the second fan blades 230.

(41) In still further arrangements, the arrays of first fan blades 220 and second fan blades 230 may have alternative geometrical arrangements.

(42) Various example embodiments of the invention are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the invention. Various changes may be made to the invention described and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), or scope of the present invention. Further, it will be appreciated by those with skill in the art that each of the individual variations described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope of the present inventions. All such modifications are intended to be within the scope of claims associated with this disclosure.

(43) The invention includes methods that may be performed using the subject devices. The methods may comprise the act of providing such a suitable device. Such provision may be performed by the end user. In other words, the providing act merely requires the end user obtain, access, approach, position, set-up, activate, power-up or otherwise act to provide the requisite device in the subject method. Methods recited herein may be carried out in any order of the recited events which is logically possible, as well as in the recited order of events.

(44) Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

(45) The foregoing description of various aspects of the disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person of skill in the art are included within the scope of the disclosure as defined by the accompanying claims.