CN116961289A - Method and apparatus for cooling a rotor assembly - Google Patents

Abstract

A method of cooling rotor winding end turns extending from a rotor core includes coupling a collar to a rotatable shaft of the rotor core. The collar has: a first wall facing the rotor core; a second wall spaced apart from and opposite the first wall; a third wall defining a set of apertures therethrough between the first wall and the second wall; a first cavity cooperatively defined by the first, second, and third walls, having a first opening opposite the third wall; a fourth wall that constrains the third wall; a second cavity cooperatively defined by the second, third and fourth walls, the second cavity defining a second opening opposite the second wall. The first and second cavities are in fluid communication and the rotor winding end turns are receivable into the second cavity. The method includes directing a coolant into a first cavity and delivering the coolant to a second cavity.

Description

Method and apparatus for cooling a rotor assembly

Cross Reference to Related Applications

The present application claims the benefit of indian patent application No. 202211023026 filed on 3 months 19 of 2022 and U.S. patent application No. 17/883,655 filed on 8 months 9 of 2022, which are incorporated herein by reference in their entireties.

Technical Field

The invention relates to a method and apparatus for cooling a rotor assembly.

Background

Electric machines such as electric motors or generators are used in energy conversion. Such motors operate by interaction of magnetic fields and current carrying conductors generate force or power, respectively. Typically, an electric motor converts electrical energy into mechanical energy. Instead, the generator converts mechanical energy into electrical energy. For example, in the aircraft industry, it is common to combine a motor mode and a generator mode in the same electric machine, wherein the electric machine in motor mode functions as a starting engine and as a generator according to the mode.

Regardless of the mode, the electric machine typically includes a rotor having rotor windings that are driven to rotate by a rotating source, such as a mechanical machine or an electric machine, which for some aircraft may be a gas turbine engine. Heat is generated in the rotor due to the flow of current through the windings and there is a varying magnetic field in the rotor, resulting in a temperature rise in the rotor. It is desirable to cool the rotor to protect the electric machine from damage and to increase the electric machine power density to allow more power from the smaller physical size electric motor.

Disclosure of Invention

Technical solution 1. A rotor assembly for an electric machine, comprising:

a rotor core defining a set of circumferentially spaced, axially extending slots thereon;

a set of rotor windings disposed within the slots having an axial winding portion extending axially along the rotor core and defining a set of rotor winding end turns extending axially beyond the rotor core to define an overhang having upper and lower surfaces connected by ends;

a coil receiving collar coupled to the rotor core, the coil receiving collar comprising:

a first wall member facing the rotor core;

a second wall member axially spaced apart from and opposed to the first wall member;

a third wall member extending from the first wall member to the second wall member, the third wall member defining a set of first apertures therethrough;

a first cavity cooperatively defined by the first, second, and third wall members, the first cavity having a first opening opposite the third wall member;

a fourth wall member spaced apart from and restraining the third wall member opposite the third wall member;

A second cavity cooperatively defined by the second, third, and fourth wall members, the second cavity having a second opening opposite the second wall member;

wherein the first cavity is in fluid communication with the second cavity and the overhang is receivable into the second cavity via the second opening; and is also provided with

Wherein the overhang is disposed in the second cavity and the first cavity is in fluid communication with the second cavity.

The rotor assembly according to any preceding claim 2, wherein the third wall member is disposed to face the lower surface, the second wall member is disposed to face the end portion, and the fourth wall member is disposed to face the upper surface.

Claim 3 the rotor assembly of any preceding claim, further comprising a rotatable shaft, wherein the first and second wall members are coupled to the rotatable shaft at respective ends distal to the third wall member.

Claim 4 the rotor assembly of any preceding claim, wherein the rotatable shaft defines at least one coolant passage in fluid communication with the first cavity.

Claim 5 the rotor assembly of any preceding claim, wherein the first wall member further comprises a first aperture defined therethrough and the second wall member comprises a second aperture defined therethrough, and wherein the rotatable shaft is received through the first and second apertures.

Claim 6 the rotor assembly of any preceding claim, wherein the third wall member is capable of separating the first cavity from the second cavity.

Claim 7 the rotor assembly of any preceding claim, wherein the first cavity is in fluid communication with the second cavity via the set of first apertures.

The rotor assembly of any preceding claim, wherein the first cavity comprises at least one of a first channel defined on the first wall member and a second channel defined on the second wall member.

Claim 9 the rotor assembly of any preceding claim, wherein the overhang defines a passageway extending within the second cavity between the third wall member and the fourth wall member.

Claim 10 the rotor assembly of any preceding claim, wherein the passageway is in fluid communication with the set of first apertures.

Claim 11 the rotor assembly of any preceding claim, wherein the second wall member defines a set of circumferentially spaced apart second apertures defined therethrough, the second apertures being in fluid communication with the second cavity.

Technical solution claim 12, a coil-receiving collar coupleable to a rotatable shaft of an electric machine having a rotor core including a set of rotor winding end turns extending therefrom, the coil-receiving collar comprising:

a first wall member facing the rotor core;

a second wall member axially spaced apart from and opposed to the first wall member;

a third wall member extending from the first wall member to the second wall member, the third wall member defining a set of first apertures therethrough;

a first cavity cooperatively defined by the first, second, and third wall members, the first cavity having a first opening opposite the third wall member;

a fourth wall member spaced apart from and restraining the third wall member opposite the third wall member;

a second cavity cooperatively defined by the second, third, and fourth wall members, the second cavity having a second opening opposite the second wall member;

Wherein the first cavity is in fluid communication with the second cavity and the rotor winding end turns are receivable into the second cavity via the second opening.

Technical solution the coil-receiving collar of any preceding technical solution, wherein the first cavity is defined at least in part by at least one of a first channel defined on the first wall member and a second channel defined on the second wall member.

Technical solution the coil-receiving collar of any preceding technical solution, wherein the first wall member further includes a first aperture defined therethrough, the second wall member includes a second aperture defined therethrough, the first and second apertures sized to receive the rotatable shaft therethrough.

Technical solution the coil-receiving collar of any preceding technical solution, wherein the first and second apertures are defined at ends of the first and second walls, respectively, distal to the third wall member.

The coil-receiving collar of any preceding claim, wherein the rotor winding end turns define a passageway therebetween extending within the second cavity between the third wall member and the fourth wall member.

Claim 17 the coil-receiving collar of any preceding claim, wherein the passageway is in fluid communication with the set of first apertures.

The coil-receiving collar of any preceding claim, wherein the second wall member defines a set of circumferentially spaced apart second apertures defined therethrough, the second apertures being in fluid communication with the second cavity.

The method of cooling a set of rotor winding end turns extending from a rotor core of a rotor assembly, comprising:

coupling a coil-receiving collar to a rotatable shaft of the rotor assembly, the coil-receiving collar having: a first wall member facing the rotor core; a second wall member axially spaced apart from and opposed to the first wall member; a third wall member extending from the first wall member to the second wall member, the third wall member defining a set of first apertures therethrough; a first cavity cooperatively defined by the first, second, and third wall members, the first cavity having a first opening opposite the third wall member; a fourth wall member spaced apart from and restraining the third wall member opposite the third wall member; a second cavity cooperatively defined by the second, third, and fourth wall members, the second cavity having a second opening opposite the second wall member, wherein the first cavity is in fluid communication with the second cavity and the rotor winding end turns are received into the second cavity via the second opening;

Directing a fluid coolant flow to the first cavity;

delivering the fluid coolant flow radially outwardly toward the second cavity; and

the fluid coolant flow is conveyed radially outwardly through the rotor winding end turns.

Technical solution the method according to any of the preceding technical solutions, further comprising: the fluid coolant flow is directed axially outward toward a set of stator windings by the coil receiving collar via a gap defined between the coil receiving collar and the rotor core.

Drawings

In the drawings:

FIG. 1 is an isometric view of a gas turbine engine having a generator according to aspects described herein.

Fig. 2 is an isometric view of an exterior of the generator of fig. 1 according to various aspects described herein.

FIG. 3 is a schematic cross-sectional view of the generator of FIG. 2 taken along line III-III of FIG. 2, in accordance with aspects described herein.

Fig. 4 illustrates a partially exploded isometric view of a rotor assembly and a coil-receiving collar for the generator of fig. 3, in accordance with various aspects described herein.

Fig. 5 illustrates a perspective view of a coil-receiving collar of the rotor assembly of fig. 4, in accordance with aspects described herein.

Fig. 5A illustrates a cross-sectional view taken along line VA-VA of the coil-receiving collar of fig. 5, in accordance with various aspects described herein.

Fig. 6 illustrates an enlarged cross-sectional view of a coil-receiving collar of the rotor assembly of fig. 4, in accordance with various aspects described herein.

FIG. 7 illustrates an exemplary method of cooling rotor winding end turns according to aspects described herein.

Detailed Description

Aspects of the present disclosure may be implemented in any environment in which an electric motor is used, whether the electric motor provides driving force or generates electricity. For the purposes of this specification, such electric motors will be generally referred to as electric machines, electric machine assemblies, or similar language, which means that one or more stator/rotor combinations may be included in the machine. Although the present description is mainly directed to a motor that provides power generation, it is also applicable to a motor that provides driving force or a motor that provides both driving force and power generation. Furthermore, while the present description is directed primarily to an aircraft environment, aspects of the present disclosure may also be applicable in any environment in which an electric machine is used. Accordingly, a brief overview of the contemplated environment should facilitate a more comprehensive understanding.

While the various elements of a "set" will be described, it will be understood that the "set" may include any number of the corresponding elements, including only one element. As used herein, the term "axial" or "axially" refers to a dimension along a longitudinal axis of a generator or along a longitudinal axis of a component disposed within the generator.

As used herein, the term "radial" or "radially" refers to a dimension extending between a central longitudinal axis, an outer circumference, or a circular or annular member disposed thereon. The use of the terms "proximal" or "proximally" by itself or in combination with the terms "radial" or "radially" refers to movement in a direction toward the central longitudinal axis or a component being relatively closer to the central longitudinal axis than another component.

All directional references (e.g., radial, axial, upper, lower, upward, downward, left, right, lateral, front, rear, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use thereof. Joinder references (e.g., attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a series of elements and relative movement between elements unless otherwise indicated. As such, a connective reference does not necessarily infer that two elements are directly connected and in fixed relation to each other.

As used herein, a "wet" cavity generator includes a cavity that houses a rotor and a stator, the cavity being exposed to free liquid coolant (e.g., coolant that is free to move within the cavity). In contrast, in a "dry" cavity generator, the rotor and stator may be cooled by coolant contained in a fluid-tight passageway (e.g., not free to move around the cavity).

The exemplary figures are for illustrative purposes only, and the dimensions, positions, order, and relative sizes reflected in the figures herein may vary.

FIG. 1 illustrates a gas turbine engine 10 having an Auxiliary Gearbox (AGB) 12 and a motor or generator 14 according to aspects of the present disclosure. The gas turbine engine 10 may be a turbofan engine (such as General Electric GEnx or CF6 series engines) commonly used in modern commercial and military aviation, or it may be a variety of other known gas turbine engines, such as a turboprop or turboshaft engine. The AGB 12 may be coupled to a turbine shaft (not shown) of the gas turbine engine 10 by a mechanical power output 16. The gas turbine engine 10 may be any suitable gas turbine engine used in modern aviation, or it may be a variety of other known gas turbine engines, such as a turboprop or turboshaft engine. The type and details of the gas turbine engine 10 are not germane to the present disclosure and will not be further described herein. Although generator 14 is shown and described, aspects of the disclosure are not limited thereto and may include any electric machine such as, but not limited to, a motor or generator.

FIG. 2 more clearly illustrates a non-limiting example of the generator 14 and its housing 18 according to aspects of the present disclosure. The generator 14 may include a clamping interface 20 for clamping the generator 14 to the AGB 12 (not shown in FIG. 2). A plurality of electrical connections may be provided on the exterior of the generator 14 to provide electrical power transfer to and from the generator 14. The electrical connection may further be connected by a cable to an electrical power distribution node of an aircraft having the gas turbine engine 10 to provide power to various items on the aircraft, such as lights and seat back monitors. The generator 14 may include a liquid coolant system for cooling or dissipating heat generated by components of the generator 14 or by components proximate to the generator 14 (one non-limiting example of which may be the gas turbine engine 10). For example, the generator 14 may include a liquid cooling system that uses oil as a coolant.

The liquid cooling system may include a cooling fluid inlet port 82 and a cooling fluid outlet port 84 for controlling the supply of coolant to the generator 14. In one non-limiting example, the cooling fluid inlet port 82 and the cooling fluid outlet port 84 may be used to cool at least a portion of a rotor or stator of the generator 14. The liquid cooling system may also include a second coolant outlet port 91 shown at the rotatable shaft portion of the generator 14. Alternatively, as a non-limiting example, the liquid cooling system may include a rotatable shaft coolant inlet port 94 or a generator coolant outlet port 95. Although not shown, aspects of the present disclosure may also include other liquid cooling system components, such as a liquid coolant reservoir fluidly coupled with the cooling fluid inlet port 82, the rotatable shaft coolant inlet port 94, the cooling fluid outlet port 84, or the generator coolant outlet port 95, and a liquid coolant pump that forcibly supplies coolant through the ports 82, 84, 94, 95, or the generator 14.

The non-limiting interior of the generator 14 is best seen in fig. 3, which is a cross-sectional view of the generator 14 shown in fig. 2 taken along line III-III. Rotatable shaft 40 is located within generator 14 and is the primary structure for supporting the various components. Rotatable shaft 40 may have a single diameter or may vary in diameter along its length. Rotatable shaft 40 is supported by spaced bearings 42 and 44 and is configured to rotate about an axis of rotation 41. Several elements of the generator 14 have a stationary part and a rotating part, wherein the stationary part is fixed relative to the housing 18, and wherein the rotating part is arranged on the rotatable shaft 40 or is rotatably fixed relative to the rotatable shaft 40. Examples of these elements may include a main machine 50, an exciter 60, and a Permanent Magnet Generator (PMG) 70 housed within a main machine cavity 51. The corresponding rotating components include the main machine rotor 52, the exciter rotor 62, and the PMG rotor 72, respectively, and the corresponding stationary components include the main machine stator 54 or stator core, the exciter stator 64, and the PMG stator 74. In this manner, the main machine rotor 52, the exciter rotor 62, and the PMG rotor 72 are disposed on the rotatable shaft 40 and co-rotate with the rotatable shaft 40. The stationary components may be mounted to any suitable portion of the housing 18 and include the main machine stator 54, the exciter stator 64, and the PMG stator 74. Collectively, the stationary components define an interior through which and relative to which the rotatable shaft 40 extends.

It will be appreciated that the main machine rotor 52, exciter rotor 62, and PMG rotor 72 may have a set of rotor poles, and the main machine stator 54, exciter stator 64, and PMG stator 74 may have a set of stator poles. The set of rotor poles may generate a set of magnetic fields relative to the set of stator poles such that rotation of the rotor magnetic fields relative to the stator poles generates electrical currents in the respective stator components.

At least one of the rotor poles and the stator poles may be formed from a core with posts and wires wound around the posts to form windings, wherein the windings have at least one end turn. The illustrated aspects of the present disclosure include at least one set of stator windings 90 disposed longitudinally along the housing 18, i.e., parallel to the housing 18 and the axis of rotation 41. The set of stator windings 90 may also include a set of stator winding end turns 92 that extend axially beyond opposite ends of the longitudinal length of the main machine stator 54.

The components of the generator 14 may be any combination of known generators. For example, the host 50 may be a synchronous or asynchronous generator. In addition to the accessories shown in this regard, there may be other components that need to operate for a particular application. For example, in addition to the electromechanical accessories shown, there may be other accessories driven from the same rotatable shaft 40, such as a liquid coolant pump, a fluid compressor, or a hydraulic pump.

As explained above, the generator 14 may be oil cooled and thus may include a cooling system 80. The cooling oil may be used to dissipate heat generated by the electrical and mechanical functions of the generator 14. The cooling system 80 using oil may also provide lubrication of the generator 14. In the illustrated aspect, the generator 14 may be a liquid cooled wet cavity cooling system 80 that includes a cooling fluid inlet port 82 and a cooling fluid outlet port 84 for controlling the supply of cooling fluid to the cooling system 80. The cooling system 80 may also include, for example, a cooling fluid reservoir 86 and various cooling passages. The rotatable shaft 40 may provide one or more channels or paths for a coolant or fluid coolant flow 85 (schematically shown as arrows) for the main machine rotor 52, exciter rotor 62, and PMG rotor 72, and a rotor shaft cooling fluid outlet 88, such as a second coolant outlet port 91, in which residual, unused, or unused oil may be discharged from the rotatable shaft 40. For example, the rotatable shaft 40 may define a first radial coolant passage 144 (shown in fig. 6).

In a non-limiting example of the generator 14, the fluid coolant flow 85 may be further distributed, directed, exposed, sprayed, or otherwise deposited onto a set of stator windings 90, a set of stator winding end turns 92, or onto alternative or additional components. In this example, the fluid coolant flow 85 may flow radially outward from the rotatable shaft 40 toward a set of stator windings 90 or a set of stator winding end turns 92. In this sense, the coolant may cool a corresponding set of stator windings 90 or a set of stator winding end turns 92.

Fig. 4 illustrates an isometric partially exploded view of the rotor assembly 96 of the main electric machine 50. The rotor assembly 96 may define a first axial end 102 and an opposing second axial end 104 axially spaced from the first axial end 102. As shown, the rotor assembly 96 may include a rotor core 100, such as a laminated rotor core 100, rotatably coupled to the rotatable shaft 40 to co-rotate with the rotatable shaft 40 and support at least one rotor pole 106. The rotor assembly 96 may also include a coil receiving collar 150.

In the illustration of fig. 4, an aspect is shown that includes four rotor poles 106. Other aspects are not so limited, and rotor assembly 96 may alternatively have fewer than four rotor poles 106, or more than four poles 106, without departing from the scope of the present disclosure, and the aspects may be applicable to rotor assemblies 96 having any desired number of rotor poles 106. Each rotor pole 106 may include a set of electrically conductive rotor lines or rotor windings 110 wound around a portion of rotor core 100. For example, in a non-limiting aspect, the rotor core 100 may define a set of slots 108 thereon. The slots 108 may include respective longitudinal axes extending axially along the rotor core 100. The slots 108 may be circumferentially spaced apart from one another. In a non-limiting aspect, slots 108 may be disposed around the perimeter of rotor core 100. The slots 108 may be sized to receive respective rotor windings 110 therein. The rotor windings 110 disposed within the slots 108 may define axial winding portions 111 extending axially along the rotor core 100, and rotor winding end turns 112 extending axially beyond the rotor core 100. In the perspective view of the illustrated example, slots 108 may be located below a set of rotor windings 110. While rotor winding 110 or rotor winding end turns 112 may refer to a set of windings or end turns, an end turn may comprise only one of a set of rotor windings 110, or only a portion of a set of rotor windings 110 that extends axially beyond rotor core 100, such as only at first axial end 102 or second axial end 104.

A set of rotor winding end turns 112 may include respective rings or arcuate curved portions 113, the rings or arcuate curved portions 113 being arranged to extend axially beyond the rotor core 100 to define respective overhangs (overhangs) 114, the overhangs 114 having upper and lower surfaces 114a, 114b (see fig. 6) connected by ends 114 c.

In a non-limiting aspect, the overhangs 114 may define respective channels 116 extending therethrough. For example, in a non-limiting aspect, each respective channel 116 may have a width defined by the width and spacing between slots 108, or the width and spacing between rotor winding end turns 112, or both. The rotor winding end turns 112 may define a corresponding set of radially extending rotor end turn passages 156 disposed therebetween. Each rotor end turn passage 156 may define a radially extending passage between rotor windings 110. For example, in a non-limiting aspect, the rotor end turn passages 156 may include respective channels 116 that extend through the curved portions 113 defined by the respective rotor winding end turns 112. At each opposing axial end 102, 104, a set of rotor winding end turns 112 may be at least partially supported or contained by a coil receiving collar 150.

As will be described in greater detail herein, the coil receiving collar 150 may provide a balanced support structure to contain radially outward movement or radially inward movement or both of the rotor winding end turns 112 while facilitating the conveyance of the fluid coolant flow 85 to the rotor winding end turns 112. In a non-limiting aspect, a coil-receiving collar 150 may be provided at either axial end 102, 104 of the rotor assembly 96. For example, in some aspects, a single coil-receiving collar 150 may be provided at one end of the rotor assembly 96. In other non-limiting aspects, respective coil-receiving collars 150 may be provided at both the first end 102 and the opposing second end 104 of the rotor assembly 96. In these aspects, the respective receiving collars 150 disposed at the opposed first and second ends 102, 104 may be substantially similar or different, as desired for the rotor assembly 96.

A respective coil receiving collar 150 may be rotatably coupled to each end of the rotatable shaft 40 of the rotor assembly 96. For example, a respective coil-receiving collar 150 may be coupled to one end (e.g., the first axial end 102 or the second end 104) of the rotor assembly 96. In other aspects, the respective coil-receiving collars 150 may be coupled to the rotatable shaft 40 at both the first axial end 102 and the second axial end 104 of the rotor assembly 96.

A non-limiting aspect of the coil receiving collar 150 is depicted in fig. 5 and 5A, and will be described with simultaneous reference to fig. 5 and 5A. In a non-limiting aspect, the coil-receiving collar 150 may comprise a generally annular structure. The coil housing collar 150 may include a first wall member 151, a second wall member 152, a third wall member 153, a fourth wall member 154, a first cavity 171, and a second cavity 172. A first hole 161 may be defined through the first wall member 151 and a second hole 162 may be defined through the second wall member 152. The third wall member 153 may define a set of first apertures 163 therethrough.

The first wall member 151 may be disposed to face the rotor core 100. The second wall member 152 is axially spaced from the first wall member 151 to define a first cavity 171 therebetween. The third wall member 153 may extend from the first wall member 151 to the second wall member 152. In a non-limiting aspect, the first wall member 151 and the second wall member 152 may support the third wall member 153. The fourth wall member 154 may circumscribe the third wall member 153 and be spaced apart from the third wall member 153 to define a second cavity 172 therebetween. The first cavity 171 may have a first open end 171a, and the second cavity 172 may have a second open end 172a. In a non-limiting aspect, the third wall member 153 may separate the first cavity 171 from the second cavity 172. In a non-limiting aspect, the third wall member 153 may partially define a first cavity 171 and a second cavity 172. The first open end 171a may be opposite the third wall member 153, and the second open end 172a may be opposite the second wall member 172.

In a non-limiting aspect, one or more of the first wall member 151, the second wall member 152, the third wall member 153, and the fourth wall member 154 may define an annular structure. The first wall member 151 may define an axially inner surface 151a and an opposing axially outer surface 151b. The first wall member 151 may include a circumferential third surface 151c (e.g., defining a first aperture 161) disposed between the axially inner surface 151a and the axially outer surface 151b. The second wall member 152 may define an axially inner surface 152a and an opposing axially outer surface 152b. The second wall member 152 may include a circumferential third surface 152c (e.g., defining a second bore 162) disposed between the axially inner surface 152a and the axially outer surface 152b. The fourth wall member 154 may define a radially inner surface 154a and an opposing radially outer surface 154b. The third wall member 153 may define a radially inner surface 153a and an opposing radially outer surface 153b. In a non-limiting aspect, the third wall member 153 can be coupled to the axially outer surface 151b of the first wall member 151 at a first end and to the axially inner surface 152a of the second wall member 152 at a second, opposite end.

In a non-limiting aspect, the third wall member 153 can define an annular structure. In a non-limiting aspect, the first apertures 163 defined through the third wall member 153 may be circumferentially spaced apart from one another. A set of first apertures 163 may be in fluid communication with the first cavity 171 and the second cavity 172. For example, a set of first apertures 163 may extend radially from the radially inner surface 153a to the opposite radially outer surface 153b. In this manner, the first cavity 171 may be in fluid communication with the second cavity 172 via a set of first apertures 163.

In some non-limiting aspects, the second wall member 152 may define a set of second apertures 167 therethrough. Similarly, in a non-limiting aspect, a set of second apertures 167 may be circumferentially spaced apart from one another. A set of second apertures 167 may be in fluid communication with the second cavity 172 and the exterior of the coil-receiving collar 150. For example, a set of second apertures 167 may extend axially from an axially inner surface 152a to an opposing axially outer surface 152b.

In a non-limiting aspect, the first wall member 151 may define a set of cutouts or first passages 181 defined thereon in fluid communication with the rotatable shaft 40. For example, a set of first passages 181 may extend radially from the third surface 151c of the first wall member 151 (i.e., facing the rotatable shaft 40) to the radially inner surface 153a of the third wall member 153. Each first passage 181 may define a first radially inner end 181a and a first radially outer end 181b. The first radially inner end 181a may be defined at the third surface 151c of the first wall member 151 and the corresponding first radially outer end 181b may be defined proximal to the radially inner surface 153a of the third wall member 153. In a non-limiting aspect, the first passages 181 may be circumferentially spaced apart from one another. In some aspects, the first passage 181 may be formed as a set of grooves on the axially outer surface 151b of the first wall member 151. In this way, the first passage 181 may increase or enlarge the size of the first cavity 171. In some aspects, a set of first passages 181 may be disposed in fluid communication with a set of first apertures 163.

Additionally or alternatively, in a non-limiting aspect, the second wall member 152 may define a set of cutouts or second channels 182 in fluid communication with the rotatable shaft 40. For example, a set of second channels 182 may extend radially from the third surface 152c of the second wall member 152 (i.e., facing the rotatable shaft 40) to the radially inner surface 153a of the third wall member 153. Each second passage 182 may include a second radially inner end 182a and a second radially outer end 182b. The second radially outer end 182a may be defined at the third surface 152c of the second wall member 152, and the corresponding second radially outer end 182b may be defined proximal to the radially inner surface 153a of the third wall member 153. In a non-limiting aspect, the second channels 182 may be circumferentially spaced apart from one another. In some aspects, the second channel 182 may be formed as a set of grooves on the axially inner surface 152a of the second wall member 152. In this way, the second channel 182 may increase or enlarge the size of the first cavity 171. In some aspects, a set of second passages 182 may be disposed in fluid communication with a set of first apertures 163.

In a non-limiting aspect, the third wall member 153 may be disposed between and extend between the first wall member 151 and the second wall member 152. In a non-limiting aspect, the second wall member 152 can be coupled to the fourth wall member 154. The fourth wall member 154 may be radially spaced apart from the third wall member 153 and constrain the third wall member 153. In a non-limiting aspect, the first wall member 151 and the second wall member 152 can be arranged substantially orthogonal to the third wall member 153 or the fourth wall member 154, or both.

The second cavity 172 may define a first radial length LR1. In a non-limiting aspect, the first radial length LR1 can be based on a distance between the radially outer surface 153b of the third wall member 153 and the radially inner surface 154a of the fourth wall member 154. Additionally, in a non-limiting aspect, the second cavity 172 may define a first axial length LA1. In a non-limiting aspect, the first axial length LA1 may be based on a distance between the axially inner surface 152a of the second wall member 152 and the open end 172a of the second cavity 172. In some aspects, the first axial length LA1 and the first radial length LR1 may be configured to cooperatively define a volume or space sized to operably receive the rotor winding end turns 112 or overhangs 114 therein.

It will be appreciated that aspects as disclosed herein are not limited to any particular number of rotor poles, and that the aspects may be applicable to rotor assemblies 96 having any desired number of poles.

FIG. 6 illustrates a portion of the rotor assembly 96 of FIG. 4 for a better understanding of the cooling system 80 and the fluid coolant flow 85 from the rotatable shaft 40 to a set of rotor winding end turns 112 and a set of stator winding end turns 92. As will be described in greater detail herein, the fluid coolant flow 85 may be directed or carried to the rotor winding end turns 112 via the coil receiving collar 150.

As shown, the first cavity 171 may be disposed at least partially beneath the rotor winding end turns 112. In this example, "below …" means a relative position radially closer to the rotational axis 41 of the rotatable shaft 40. In a non-limiting aspect, the fourth wall member 154 may be configured to at least partially overlie the rotor winding end turns 112. In this example, "overlying" means a relative position radially further away from the rotational axis 41 of the rotatable shaft 40.

For example, the overhang 114 defined by the curved portion 113 of the rotor winding end turn 112 may be received through the second open end 172a and at least partially disposed within the second cavity 172. In this manner, the overhang 114 may be at least partially supported or contained by the coil-receiving collar 150. In a non-limiting aspect, the third wall member 153 may be disposed to face the lower surface 114b, the second wall member 152 may be disposed to face the end 114c, and the fourth wall member 154 may be disposed to face the upper surface 114a.

The rotatable shaft 40 defines a first coolant conduit 140 that is fluidly connected to a coolant source 165. The coolant source 165 may be, but is not limited to, a cooling fluid inlet port (see fig. 2 and 3). The direction or position of the coolant source 165 is not limited by the illustration, and is contemplated in any position fluidly coupled to the first coolant conduit 140. It is further contemplated that additional conduits, pumps, valves, or other devices may be included to fluidly connect coolant source 165 and first coolant conduit 140.

The first and second apertures 161, 162 may be sized to receive the rotatable shaft 40 therethrough and receive the fluid coolant flow 85 therefrom. The coil receiving collar 150 may be fixedly coupled to the rotatable shaft 40 using one or more bolts, screws, pins, keys, or other known fasteners. In other non-limiting aspects, the coil-receiving collar 150 may be coupled to the rotatable shaft 40 via an interference fit engagement, a friction fit engagement, or a press fit engagement between the coil-receiving collar 150 and the rotatable shaft 40. For example, the third surface 151c of the first wall member 151 or the third surface 152c of the second wall member 152, or both, may be fixedly coupled to the rotatable shaft 40. Other aspects are not so limited, and it is contemplated that coil-receiving collar 150 may be rotatably coupled to rotatable shaft 40 by any desired attachment mechanism. It will be appreciated that when so coupled, rotation of the rotatable shaft 40 will result in rotation of the coil receiving collar 150.

In operation, the fluid coolant flow 85 may enter the rotatable shaft 40 of the rotor assembly 96 via the inlet port 82 (see fig. 2 and 3). The rotatable shaft 40 may at least partially define a first coolant conduit 140 through which the fluid coolant flow 85 may flow radially outward from the rotational axis 41 due to centrifugal force effects of the rotatable shaft 40. The first radial coolant passage 144 may fluidly couple the first coolant conduit 140 and the coil receiving collar 150 by extending radially through the rotatable shaft 40.

In operation, the coil receiving collar 150 may receive the fluid coolant flow 85 from the first radial coolant passage 144 via the first cavity 171. In a non-limiting aspect, the fluid coolant flow 85 can collect or accumulate on the first wall member 151 or the second wall member 152, or both. As such, the first cavity 171, the first wall member 151, the second wall member 152, or a combination thereof, operatively define a coolant reservoir. The fluid coolant flow 85 may then be centrifugally transported to a set of first orifices 163.

The fluid coolant flow 85 may further pass through the first apertures 163 (i.e., radially from the radially inner surface 153a to the opposing radially outer surface 153 b) and thus be carried from the first cavity 171 to the second cavity 172 via a set of the first apertures 163.

In this manner, the fluid coolant flow 85 may be received by the rotor winding end turns 112, with the rotor winding end turns 112 disposed in the second cavity 172 and coupled in fluid communication with the first apertures 163 to operatively receive the fluid coolant flow 85 from the first apertures 163.

As shown, the rotor winding end turns 112 may include a set of rotor end turn passages 156. As used herein, a set of radial rotor end turn passages 156 refers to a set of radially extending passages defined between the rotor windings 110. In a non-limiting aspect, a set of rotor end turn passages 156 may fluidly couple the second cavity 172 to the coolant outlet 169. For example, in a non-limiting aspect, the rotor end turn passages 156 may include respective channels 116 (see FIG. 4) that extend through the curved portions 113 defined by the respective rotor winding end turns 112. In some aspects, a respective channel or passage 156 may extend radially from the third wall member 153 to the fourth wall member 154.

In one non-limiting example, the second cavity 172 may be configured to overlie the set of first apertures 163 such that coolant fluid discharged from the first apertures 163 is received by the second cavity 172. The second cavity 172 may be configured to direct the fluid coolant flow 85 received from the first cavity 171 via the set of first apertures 163 in a radial and/or axial direction. As such, the fluid coolant flow 85 is reliably delivered radially from the first cavity 171 to the second cavity 172 and, thus, to the rotor winding end turns 112 or radial rotor end turn passages 156.

In a non-limiting aspect, a gap or coolant outlet 169 may be cooperatively defined by the coil-receiving collar 150 and the rotor core 100. In a non-limiting aspect, the coolant outlet 169 may be in fluid communication with a set of rotor end turn passages 156. The coolant outlet 169 may be disposed at an outer circumference 170 of the rotor assembly 96. Alternatively, the coolant outlets 169 may define nozzles (not shown) configured to direct the fluid coolant flow 85 toward a set of stator windings 90 or a set of stator winding end turns 92 (see FIG. 3). The coolant outlet 169 may be at least partially defined by the insulating layer 128, in contact with the insulating layer 128, or coupled to the insulating layer 128, the insulating layer 128 being axially located between at least a portion of the rotor core 100 and the coil receiving collar 150.

In operation, the fluid coolant flow 85 may be centrifugally carried from the first apertures 163 to the rotor end turn passages 156. The fluid coolant flow 85 may then be carried toward the coolant outlet 169, such as in an axially inward direction (e.g., toward the rotor core 100).

In this manner, the coolant outlet 169 may receive the fluid coolant flow 85 from the second cavity 172. For example, in a non-limiting aspect, the second cavity 172 may be in fluid communication with the coolant outlet 169 via the radially inner surface 154a of the fourth wall member 154 such that rotation of the rotatable shaft 40 about the rotational axis 41 causes the fluid coolant flow 85 to pass radially through the rotor winding end turns 112 and to be discharged radially outward from the rotor assembly 96.

In operation, in a non-limiting aspect, a set of second apertures 167 may additionally provide cooling air or oil mist to the rotor winding end turns.

During operation of generator 14, the magnetic field generated by the set of main machine rotor windings 110 generates electrical power in main machine stator windings 90 relative to the rotation of the set of main machine stator windings 90. This magnetic interaction further generates heat in a set of main machine rotor windings 110 and main machine stator windings 90. According to aspects described herein, the fluid coolant flow 85 may enter the rotatable shaft 40 of the rotor assembly 96 via the inlet port 82. The rotatable shaft 40 may at least partially define a first coolant conduit 140 through which fluid may flow radially outward from the rotational axis 41. The fluid coolant flow 85 may then be axially discharged into a passageway defined in the rotor core 100. Additionally or alternatively, fluid from the first coolant conduit 140 may pass through the first radial coolant passage 144 to be received radially by the coil receiving collar 150 and distributed to the first cavity 171.

The fluid may continue to flow radially outward through the first cavity 171 and through the first apertures 163 and to the radial rotor end turn passages 156 passing between the rotor winding end turns 112, thereby transferring heat from the set of rotor windings 110 into the fluid coolant flow 85 by conduction. This heat transfer by conduction may remove heat from rotor windings 110 into coolant 85. The coolant 85 may drain radially from the radial rotor end turn passages 156 into the second cavity 172, where the coolant 85 may further collect at the radially inner surface 154a of the fourth wall member 154. The radially inner surface 154a of the fourth wall member 154 may redirect the fluid coolant flow 85 to the coolant outlet 169 where the fluid coolant flow is further discharged radially outward to contact a set of host stator windings 90. This contact further removes heat from the main machine stator windings 90 by transferring the heat into the fluid coolant flow 85.

FIG. 7 illustrates a method 700 of cooling a rotor assembly 96 having rotor winding end turns 112 defining a set of radial rotor end turn passages 156 of the rotor assembly 96. Although the method is described with reference to rotor assembly 96 and coil-receiving collar 150 of fig. 4-6, other aspects are not limited in this regard.

The method may begin at step 710 by rotatably coupling the coil-receiving collar 150 having a first cavity 171 in fluid communication with a second cavity 172 to the rotatable shaft 40 such that the first cavity 171 is in fluid communication with the rotatable shaft 40 and the rotor winding end turns 112 are at least partially enclosed by the second cavity 172.

The method 700 includes directing a fluid coolant flow 85 to the coil containment collar 150 at step 720. Non-limiting examples of directing the fluid coolant flow 85 through the coil receiving collar 150 may include directing the fluid coolant flow 85 radially from the first coolant conduit 140, through the first radial coolant passage 144, and into the first cavity 171. Another non-limiting example of directing the fluid coolant flow 85 to the coil receiving collar 150 may include directing the fluid coolant flow 85 radially through the first radial coolant passage 144 to the first cavity 171.

In a non-limiting aspect, the method may include delivering the fluid coolant flow 85 radially outward to the second cavity 172 through the coil containment collar 150 at step 730. Non-limiting examples of conveying the fluid coolant flow 85 radially outward toward the second cavity 172 may include directing the fluid coolant flow 85 through a set of first apertures 163 to the second cavity 172.

In other non-limiting aspects, the method 200 may include delivering the fluid coolant flow 85 radially outward to the rotor winding end turns 112 at step 740. Non-limiting examples of delivering the fluid coolant flow 85 radially outward to the rotor winding end turns 112 may include directing the fluid coolant flow through a set of rotor end turn passages 156 defined by the rotor winding end turns 112.

At step 750, the method may include draining or directing the fluid coolant flow 85 from the end turn passages 156 to the coolant outlet 169. The fluid coolant flow 85 is permitted to flow radially outward from the rotor assembly 96 toward the set of stator windings 90 by the channeling from the end turn passages 156 to the coolant outlets 169.

A set of radial rotor end turn passages 156 are in thermally conductive relationship with a set of rotor winding end turns 112 so that heat from a set of rotor winding end turns 112 is transferred by conduction to the fluid coolant flow 85. Conduction of heat to the fluid coolant flow 85 and the heat conduction relationship described herein may result in the fluid coolant flow 85 removing heat from the rotor assembly 96.

The present disclosure also contemplates many other possible aspects and configurations than those shown in the above-described figures. For example, one aspect of the present disclosure contemplates coolant conduits extending along an alternative portion or length of a set of rotor windings 110. In another example, the windings or coolant conduits may also include an intervening thermally conductive layer to facilitate heat conduction while, for example, avoiding conductive relationships between the respective components. In addition, the design and placement of various components such as valves, pumps, or conduits may be rearranged so that many different in-line configurations may be achieved.

The depicted sequence is for illustration purposes only and is not meant to limit the method 200 in any way, as it should be understood that portions of the method may occur in a different logical order, additional or intervening portions may be included, or the described portion of the method may be split into multiple portions, or the described portion of the method may be omitted without detracting from the described method.

Aspects disclosed herein provide methods and apparatus for cooling a set of rotor windings or a set of rotor winding end turns during motor operation (e.g., motor or generator operation). One advantage that may be achieved in the above aspects is that the above aspects have significantly improved heat conduction to remove heat from a set of rotor windings or a set of rotor winding end turns. Improved heat transfer between a set of rotor winding end turns and coolant conduits coupled to the coolant channels provides for heat removal from the rotor winding end turns to the coolant in a much more efficient manner.

Increased heat dissipation of the rotor winding end turns allows for higher speed rotation, which may otherwise generate too much heat. Higher speed rotation may result in improved power generation or improved generator efficiency without increasing generator size. The described aspects with fluid passages for wet cavity machines also enable cooling of stator windings or end turn sections, which further reduces heat loss from the motor. The reduced heat loss in the motor allows for higher efficiency and greater power density of the generator.

Reliability is an important feature in designing aircraft components. The end assemblies described above may provide additional physical stability and improved cooling for the rotor end windings. The stability and cooling provided by the coil receiving collar allows for improved performance and reliability.

To the extent not yet described, the different features and structures of the various aspects may be used in combination with one another as desired. One feature cannot be shown in all aspects and is not intended to be interpreted as it cannot, but rather does so for simplicity of description. Thus, the various features of the different aspects may be mixed and matched as desired to form new aspects, whether or not explicitly described. This disclosure covers combinations or permutations of features described herein.

This written description uses examples to disclose aspects of the disclosure, including the best mode, and also to enable any person skilled in the art to practice aspects of the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Additional aspects of the disclosure are provided by the subject matter of the following clauses:

A rotor assembly 96 for an electric machine 14, comprising: a rotor 100 core defining a set of circumferentially spaced, axially extending slots 108 thereon; a set of rotor windings 110 disposed within the slots 108, having an axial winding portion 111 extending axially along the rotor core 100, and defining a set of rotor winding end turns 112, the set of rotor winding end turns 112 extending axially beyond the rotor core 100 to define an overhang 114 having an upper surface 114a and a lower surface 114b connected by an end 114 c; a coil receiving collar 150 coupled to the rotor core 100, the coil receiving collar 150 comprising: a first wall member 151 facing the rotor core 100; a second wall member 152 axially spaced apart from and opposed to the first wall member 151; a third wall member 153 extending from the first wall member 151 to the second wall member 152 defining a set of first apertures 163 through the third wall member 153; a first cavity 171 cooperatively defined by the first wall member 151, the second wall member 152, and the third wall member 153, the first cavity 171 having a first opening 171a opposite to the third wall member 153; a fourth wall member 154 that is spaced apart from the third wall member 153 in opposition and that constrains the third wall member 153; a second cavity 172 cooperatively defined by the second wall member 152, the third wall member 153, and the fourth wall member 154, the second cavity 172 having a second opening 172a opposite the second wall member 152; wherein the first cavity 171 is in fluid communication with the second cavity 172, and the overhang 114 is receivable into the second cavity 172 via the second opening 172a; and wherein the overhang 114 is disposed in the second cavity 172 and the first cavity 171 is in fluid communication with the second cavity 172.

The rotor assembly 96 according to the preceding clause, wherein the third wall member 153 is disposed to face the lower surface 114b, the second wall member 152 is disposed to face the end 114c, and the fourth wall member 154 is disposed to face the upper surface 114a.

The rotor assembly 96 of any one of the preceding clauses further comprising a rotatable shaft 40, wherein the first and second wall members 151, 152 are coupled to the rotatable shaft 40 at respective ends distal to the third wall member 153.

The rotor assembly 96 of any of the preceding clauses, wherein the rotatable shaft 40 defines at least one coolant passage 144 in fluid communication with the first cavity 171.

The rotor assembly 96 of any one of the preceding clauses, wherein the first wall member 151 further includes a first aperture 161 defined therethrough, the second wall member 152 includes a second aperture 162 defined therethrough, and wherein the rotatable shaft 40 is received through the first aperture 161 and the second aperture 162.

The rotor assembly 96 according to any one of the preceding clauses, wherein the third wall member 153 separates the first cavity 171 from the second cavity 172.

The rotor assembly 96 of any of the preceding clauses, wherein the first cavity 171 is in fluid communication with the second cavity 172 via the set of first apertures 163.

The rotor assembly of any one of the preceding clauses, wherein the first cavity 171 comprises at least one of a first channel 181 defined on the first wall member 151 and a second channel 182 defined on the second wall member 152.

The rotor assembly 96 according to any one of the preceding clauses, wherein the overhang 114 defines a passageway 116 extending within the second cavity 172 between the third wall member 153 and the fourth wall member 154.

The rotor assembly 96 of any one of the preceding clauses, wherein the passageway 116 is in fluid communication with the set of first apertures 163.

The rotor assembly 96 according to any one of the preceding clauses, wherein the second wall member 152 defines a set of circumferentially spaced apart second apertures 167 defined therethrough, the second apertures being in fluid communication with the second cavity 172.

A coil-receiving collar 150 coupleable to a rotatable shaft 40 of an electric machine 14, the electric machine 14 having a rotor core 100, the rotor core 100 including a set of rotor winding end turns 112 extending therefrom, the coil-receiving collar 150 comprising: a first wall member 151 facing the rotor core 100; a second wall member 152 axially spaced apart from and opposed to the first wall member 151; a third wall member 153 extending from the first wall member 151 to the second wall member 152 defining a set of first apertures 163 through the third wall member 153; a first cavity 171 cooperatively defined by the first wall member 151, the second wall member 152, and the third wall member 153, the first cavity 171 having a first opening 171a opposite to the third wall member 153; a fourth wall member 154 that is spaced apart from the third wall member 153 in opposition and that constrains the third wall member 153; a second cavity 172 cooperatively defined by the second wall member 152, the third wall member 153, and the fourth wall member 154, the second cavity 172 having a second opening 172a opposite the second wall member 152; wherein the first cavity 171 is in fluid communication with the second cavity 172 and the rotor winding end turns 112 are receivable into the second cavity 172 via the second opening 172 a.

The coil receiving collar 150 of any of the preceding clauses, wherein the first cavity 171 is defined at least in part by at least one of a first channel 181 defined on the first wall member 151 and a second channel 182 defined on the second wall member 152.

The coil receiving collar 150 of any of the preceding clauses, wherein the first wall member 151 further includes a first aperture 161 defined therethrough, the second wall member 152 includes a second aperture 162 defined therethrough, the first and second apertures 161, 162 being sized to receive the rotatable shaft 40 therethrough.

The coil receiving collar 150 of any of the preceding clauses, wherein a first aperture 161 and a second aperture 162 are defined at the ends of the first wall 151 and the second wall 152, respectively, distal to the third wall member 153.

The coil receiving collar 150 according to any one of the preceding clauses, wherein the rotor winding end turns 112 define a passageway 116 therebetween, the passageway 116 extending within the second cavity 172 between the third wall member 153 and the fourth wall member 154.

The coil receiving collar 150 according to any one of the preceding clauses, wherein the passageway 116 is in fluid communication with the set of first apertures 163.

The coil receiving collar 150 according to any one of the preceding clauses, wherein the second wall member 152 defines a set of circumferentially spaced apart second apertures 167 defined therethrough, the second apertures being in fluid communication with the second cavity 172.

A method 700 of cooling a set of rotor winding end turns 112 extending from a rotor core 100 of a rotor assembly 96, comprising: coupling a coil-receiving collar 150 to the rotatable shaft 40 of the rotor assembly 96, the coil-receiving collar 150 having: a first wall member 151 facing the rotor core 100; a second wall member 152 axially spaced apart from and opposed to the first wall member 151; a third wall member 153 extending from the first wall member 151 to the second wall member 152 defining a set of first apertures 163 therethrough; a first cavity 171 cooperatively defined by the first wall member 151, the second wall member 152, and the third wall member 153, the first cavity 171 having a first opening 171a opposite to the third wall member 153; a fourth wall member 154 that is spaced apart from the third wall member 153 in opposition and that constrains the third wall member 153; a second cavity 172 cooperatively defined by the second, third and fourth wall members 152, 153, 154, the second cavity 172 having a second opening 172a opposite the second wall member 152, wherein the first cavity 171 is in fluid communication with the second cavity 172 and the rotor winding end turns 112 are received into the second cavity 172 via the second opening 172 a; directing a fluid coolant flow 85 to the first cavity 171; delivering the fluid coolant flow 85 radially outwardly toward the second cavity 172; and delivering the fluid coolant flow 85 radially outward through the rotor winding end turns 112.

The method 700 of any of the preceding clauses, further comprising: through the coil receiving collar 150, the fluid coolant flow 85 is directed axially outward toward a set of stator windings 90 via a gap 169 defined between the coil receiving collar 150 and the rotor core 100.

Claims (10)

1. A rotor assembly (96) for an electric machine (14), comprising:

a rotor core (100) defining a set of circumferentially spaced, axially extending slots (108) thereon;

a set of rotor windings (110) disposed within the slots (108) having an axial winding portion (111) extending axially along the rotor core (100) and defining a set of rotor winding end turns (112), the set of rotor winding end turns (112) extending axially beyond the rotor core (100) to define an overhang (114) having an upper surface (114 a) and a lower surface (114 b) connected by an end (114 c);

a coil-receiving collar (150) coupled to the rotor core (100), the coil-receiving collar (150) comprising:

a first wall member (151) facing the rotor core (100);

a second wall member (152) axially spaced apart from and opposed to the first wall member (151);

a third wall member (153) extending from the first wall member (151) to the second wall member (152), the third wall member (153) defining a set of first apertures (163) therethrough;

A first cavity (171) cooperatively defined by the first wall member (151), the second wall member (152), and the third wall member (153), the first cavity (171) having a first opening (171 a) opposite the third wall member (153);

a fourth wall member (154) that is spaced apart from the third wall member (153) in opposition and that constrains the third wall member (153);

a second cavity (172) cooperatively defined by the second wall member (152), a third wall member (153), and a fourth wall member (154), the second cavity (172) having a second opening (172 a) opposite the second wall member (152);

wherein the first cavity (171) is in fluid communication with the second cavity (172), and the overhang (114) is receivable into the second cavity (172) via the second opening (172 a); and is also provided with

Wherein the overhang (114) is disposed in the second cavity (172) and the first cavity (171) is in fluid communication with the second cavity (172).

2. The rotor assembly (96) of claim 1 wherein the third wall member (153) is disposed to face the lower surface (114 b), the second wall member (152) is disposed to face the end (114 c), and the fourth wall member (154) is disposed to face the upper surface (114 a).

3. The rotor assembly (96) of claim 1 further comprising a rotatable shaft (40), wherein the first and second wall members (151, 152) are coupled to the rotatable shaft (40) at respective ends distal to the third wall member (153).

4. A rotor assembly (96) as set forth in claim 3 wherein said rotatable shaft (40) defines at least one coolant passage (144) in fluid communication with said first cavity (171).

5. A rotor assembly (96) as set forth in claim 3 wherein said first wall member (151) further includes a first aperture (161) defined therethrough and said second wall member (152) includes a second aperture (162) defined therethrough and wherein said rotatable shaft (40) is received through said first aperture (161) and second aperture (162).

6. The rotor assembly (96) of claim 1 wherein the third wall member (153) is configured to separate the first cavity (171) from the second cavity (172).

7. The rotor assembly (96) of claim 1 wherein said first cavity (171) is in fluid communication with said second cavity (172) via said set of first apertures (163).

8. The rotor assembly of claim 1, wherein the first cavity (171) comprises at least one of a first channel (181) defined on the first wall member (151) and a second channel (182) defined on the second wall member (152).

9. The rotor assembly (96) of claim 1 wherein said overhang (114) defines a passageway (116) extending within said second cavity (172) between said third wall member (153) and said fourth wall member (154).

10. The rotor assembly (96) of claim 7 wherein said passageway (116) is in fluid communication with said set of first apertures (163).