Electric motor generator system with a plurality of magnet portions abutting an inwardly facing surface of a shaft

Abstract

An electric motor generator system has a hollow rotatable shaft, a coil spar, and a plurality of magnet portions. The hollow rotatable shaft has a central longitudinal axis. The coil spar comprises one or more coil assemblies and is positioned concentrically within the hollow rotatable shaft. Each of the magnet portions is shaped to conform to a radially inwardly facing surface of the shaft. Each of the plurality of magnet portions abuts conformally against the radially inwardly facing surface of the shaft between the radially inwardly facing surface and the or each coil assembly.

Claims

1. An electric motor generator system comprising: a hollow rotatable shaft having a central longitudinal axis; a coil spar positioned concentrically within the hollow rotatable shaft and comprising one or more coil assemblies; and a plurality of magnet portions each shaped to conform to a radially inwardly facing surface of the shaft; wherein each of the plurality of magnet portions abuts conformally against the radially inwardly facing surface of the shaft between the radially inwardly facing surface and the or each coil assembly; and wherein the plurality of magnet portions extends continuously around a complete circumference of the radially inwardly facing surface of the shaft.

2. The electric motor generator system as claimed in claim 1, wherein the one or more coil assemblies are positioned on a radially outwardly facing surface of the coil spar.

3. The electric motor generator system as claimed in claim 1, wherein the shaft has a working length (L), the plurality of magnet portions extending along the entirety of the working length (L); the shaft has an outer diameter (D); and a ratio of L/D is greater than approximately 2.

4. The electric motor generator system as claimed in claim 1, wherein the coil spar is provided with a plurality of cooling holes that are adjacent to the or each coil assembly.

5. The electric motor generator system as claimed in claim 4, wherein a centre bore of the coil spar is provided with a cooling fluid, and the plurality of cooling holes directs the cooling fluid onto the or each coil assembly.

6. The electric motor generator system as claimed in claim 1, wherein a radially outwardly facing surface of the coil spar is crenelated, the crenellated surface comprises an axial sequence of crenels and merlons, and the or each coil assembly is positioned on a radially outwardly facing surface of a corresponding one of the merlons.

7. The electric motor generator system as claimed in claim 6, further comprising at least three bearing assemblies spaced along the hollow shaft, and wherein each bearing assembly provides for rotational support between the radially inwardly facing surface of the shaft and the radially outwardly facing surface of the coil spar.

8. The electric motor generator system as claimed in claim 7, wherein a spacing between adjacent bearing assemblies is less than an outer diameter of the shaft.

9. The electric motor generator system as claimed in claim 7, wherein the bearing assemblies are equi-spaced along the shaft.

10. The electric motor generator system as claimed in claim 1, wherein the coil spar is rotatable about the central longitudinal axis.

11. The electric motor generator system as claimed in claim 10, wherein the shaft rotates in a first rotational direction, and the coil spar rotates in a second rotational direction opposite to the first rotational direction.

12. A gas turbine engine comprising an electric motor generator system as claimed in claim 1.

Description

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 a turbofan gas turbine engine incorporating an electric motor generator system according to a first embodiment of the present disclosure;

(3) FIG. 2 shows a schematic part-sectional view of the electric motor generator system of FIG. 1; and

(4) FIG. 3 shows a schematic part-sectional view of an electric motor generator system according to a second embodiment of the present disclosure.

(5) 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

(6) Referring to FIGS. 1 and 2, an electric motor generator system according to a first embodiment of the disclosure is designated generally by the reference numeral 100.

(7) In the context of the present disclosure, the electric motor generator system 100 is integrated into a turbofan gas turbine engine 102. The turbofan engine 102 comprises a fan assembly 103 and a core gas turbine engine 105, both positioned within a casing 104. The electric motor generator system 100 is positioned within the centre shaft of the core gas turbine engine 105.

(8) Although in the following detailed description the electric motor generator system 100 is described with reference to a turbofan gas turbine engine, it is to be understood that the electric motor generator system 100 may form part of any suitable rotating machinery such as, for example, marine propulsion drives, industrial power transfer drives, and other motive power transfer arrangements.

(9) The electric motor generator system 100 comprises a hollow rotatable shaft 110, a coil spar 150 comprising coil assemblies 130, and a plurality of magnet portions 140. The shaft 110 has a central longitudinal axis 112.

(10) Each of the magnet portions 140 is shaped to conform to a radially inwardly facing surface 114 of the shaft 110. The magnet portions 140 abut against the radially inwardly facing surface 114 of the shaft 110. In the present embodiment, the magnet portions 140 extend around the complete circumference 116 of the radially inwardly surface 114 of the shaft 110. In this way, the magnet portions 140 line the radially inwardly facing surface 114 of the shaft 110.

(11) In the present arrangement, the shaft 110 is formed from a ferritic steel and acts as a magnetic yoke thus increasing torque density. In an alternative arrangement the rotor poles can be formed as a Halbach array, which can reduce the magnetic fields in the yoke and thus increase the torque density of the motor generator system.

(12) In the present arrangement, the magnet portions 140 are secured within the shaft by virtue of the geometrical placement of the magnet portions 140 around the circumference 116 of the radially inwardly surface 114 of the shaft 110. In operation, the centrifugal loading generated by the rotation of the shaft 110 provides an additional force securing the magnet portions 140 in place against the radially inwardly surface 114 of the shaft 110.

(13) Each of the coil assemblies 130 is positioned in axial sequence along an axial length of the coil spar 150. The coil spar 150 is accommodated within the hollow shaft 110. The coil spar 150 is positioned concentrically with the shaft 110. The shaft 110 encloses the coil spar 150. The shaft 110 is rotatable relative to the stationary coil spar 150 by means of bearing assemblies 124. The coil spar 150 is provided with a torque reaction mount 162.

(14) The coil spar 150 has a radially outwardly facing surface 154. The radially outwardly facing surface 154 is provided with crenellations 160. In the present arrangement the crenellations 160 extend in an axial direction such that each individual crenellation 160 extends circumferentially around the radially outwardly facing surface 154 of the coil spar 150.

(15) The crenellations 160 comprise an axial sequence of crenels 164 and merlons 166. Each of the crenels 164 extends radially outwardly of each of the merlons 166.

(16) Each coil assembly 130 is accommodated on a radially outwardly facing surface of a corresponding one of the merlons 166.

(17) In the embodiment shown in FIGS. 1 and 2, a bearing assembly 180 is positioned at each of the merlons 166. Each of the bearing assemblies 180 provides rotational support between the radially inwardly facing surface 114 of the shaft 110, and the radially outwardly facing surface 154 of the coil spar 150.

(18) The bearing assemblies 180 are spaced along the axial length of the shaft 110 at the spacing of the crenellations 160. In the present arrangement, each of the bearing assemblies 180 is spaced along the axial length of the hollow shaft 110 with approximately equal spacing between adjacent bearing assemblies 180.

(19) The mechanical linkage between the shaft 110 and the coil spar 150, provided by the bearing assemblies 180 ensures that if the shaft 110 deforms due to bending loads then the coil spar 150 will adopt the same deformed shape. In other words if the shaft 110 exhibits hogging due, for example, to centrifugal loading, then the coil spar 150 will adopt a correspondingly hogged shape. This means that a clearance between the radially inwardly facing surface 114 of the shaft 110, and the coil spar 150 will remain constant irrespective of the geometrical shape adopted by the shaft 110.

(20) The shaft 110 has a working length (L) 118 which is the axial length along the shaft 110 over which extends the opposing coil assemblies 130 and magnet portions 140. The shaft 110 has an outer diameter (D) 120. Consequently, the electric motor generator system has an L/D ratio that is greater than approximately 2.

(21) In operation, the coil spar 150 is held in a stationary position via the torque reaction mount 162. The relative rotation between the shaft 110 and the coil spar 150 enable the motor generator system to generate electrical power. This electrical power is transmitted from the motor generator system 100 via the electrical power output 134.

(22) Referring to FIG. 3, an electric motor generator system according to a second embodiment of the disclosure is designated generally by the reference numeral 200. Features of the electric motor generator system 200 which correspond to those of electric motor generator system 100 have been given corresponding reference numerals for ease of reference.

(23) The electric motor generator system 200 has a shaft 110 enclosing a coil spar 250. The shaft 110 comprises a plurality of magnet portions 140 attached to a radially inwardly facing surface 114 of the shaft 110.

(24) The coil spar 250 comprises a radially outwardly facing surface 254 having a crenellated profile in the axial direction. The crenellations 260 comprise an axial sequence of crenels 264 and merlons 266. Each of the crenels 264 extends radially outwardly of each of the merlons 266.

(25) The coil spar 250 comprises coil assemblies 230, with each coil assembly 230 positioned on a radially outwardly facing surface of a respective one of the merlons 266.

(26) The coil spar 250 is provided with a plurality of cooling holes 256. The cooling holes 256 are positioned adjacent to each coil assembly 230.

(27) The coil spar 250 has a centre bore 258 through which passes a flow 272 of cooling fluid 270. The cooling fluid 270 flows axially along the centre bore 258 and then flows radially outwardly through the cooling holes 256 and thence onto each coil assembly 230.

(28) As with the previous embodiment, a bearing assembly 280 is positioned at each of the merlons 266. Each of the bearing assemblies 280 provides rotational support between the radially inwardly facing surface 114 of the shaft 110, and the radially outwardly facing surface 254 of the coil spar 250.

(29) The bearing assemblies 180 are spaced along the axial length of the shaft 110 at the spacing of the crenellations 260. In the same way as described above for the previous embodiment, the arrangement of bearing assemblies 280 ensures that any bending of the shaft 110 is conformally transferred the coil spar 250. This in turn maintains a radial clearance between the radially inwardly facing surface 114 of the shaft 110, and the coil spar 250 at a constant pre-determined value.

(30) In the embodiment shown in FIG. 3, the shaft 110 rotates in a first direction 290, while the coil spar 250 rotates in a second direction 292, with the first direction 290 and the second direction 292 being opposite to one another. This increases the relative rotational speed between the shaft 110 and the coil spar 250, which in turn increases the electrical power output of the system 200 when in a generator configuration.

(31) In the present arrangement, the cooling fluid 170 is the lubricant fluid that is used to provide lubrication and heat transfer within the gas turbine core engine.

(32) In the present detailed description, the electric motor generator system 100 is described with reference to its application as an electric generator that is integrated into a turbofan gas turbine engine. However, the electric motor generator system 100 may equally function as an electric motor integrated in a gas turbine engine. Alternatively, the electric motor generator system 100 may be applied to other rotating systems as described above, either as an electric generator or as an electric generator.

(33) Various example embodiments of the disclosure 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 disclosure. Various changes may be made to the disclosure described and equivalents may be substituted without departing from the scope of the disclosure. 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), spirit or scope of the present disclosure. 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 disclosure. All such modifications are intended to be within the scope of claims associated with this disclosure.

(34) 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.

(35) 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.