The present disclosure relates generally to electric machines adapted for use with gas turbine engines, and more specifically to air cooling the rotors of such electric machines.
Gas turbine engines are used to power aircrafts, watercrafts, power generators, and the like. Gas turbine engines typically include a compressor, a combustor, and a turbine. The compressor compresses air drawn into the engine and delivers high pressure air to the combustor. In the combustor, fuel is mixed with the high pressure air and is ignited. Products of the combustion reaction in the combustor are directed into the turbine where work is extracted to drive the compressor and, sometimes, an output shaft. Left-over products of the combustion are exhausted out of the turbine and may provide thrust in some applications.
Gas turbine engines may be used in a hybrid electric propulsion system used to power the aircraft. The hybrid electric propulsion system has an electric machine powered directly or indirectly form the gas turbine engine. The electric machine is configured to power a propeller for providing thrust for the aircraft.
Electric machines generate heat during use and may need to be cooled during operation of the system. Separate external fans may be used to cool the electric machine; however, the external fans add weight to the aircraft and result in components of the electric machine being modified to provide the cooling air therein. A lightweight, non-intrusive component of the electric machine to cool the magnetic rotor drum is desired.
The present disclosure may comprise one or more of the following features and combinations thereof.
An electric machine adapted for use in an aircraft propulsion system may include a shaft, a magnetic rotor drum, and a rotor hub. The shaft may extend along an axis and be configured to rotate about the axis. The magnetic rotor drum may include a rotor drum body and a plurality of magnets arranged circumferentially about the axis and coupled with the rotor drum body for rotation therewith. The rotor hub may interconnect the shaft and the rotor drum body and moves air surrounding the electric machine in response to rotation of the shaft about the axis to cool the shaft and the magnetic rotor drum.
In some embodiments, the rotor hub may have air-moving means for drawing air axially along the shaft toward the rotor drum body at a first radial distance to transfer heat from the shaft to the air and for urging the air axially away from the rotor drum body at a second radial distance greater than the first radial distance. The air-moving means may include a rotor end cap and an impeller. The rotor end cap may extend radially between the shaft and the rotor drum body of the magnetic rotor drum. The impeller may extend axially away from the rotor end cap and away from the magnetic rotor drum.
In some embodiments, the rotor hub may further include a baffle. The baffle may extend circumferentially around the shaft. The baffle may be spaced apart radially from the shaft and spaced apart axially from the rotor end cap so that the air is drawn axially along the shaft at the first radial distance in a passage defined radially between the baffle and the shaft. The air may be urged axially away from the magnetic rotor drum at the second radial distance along a radial outer face of the baffle.
In some embodiments, the impeller may include a plurality of discrete protrusions. The plurality of discrete protrusions may be spaced apart circumferentially around the axis.
In some embodiments, the rotor drum body of the magnetic rotor drum may be formed to include a hollow cavity therein. The rotor end cap may encase an axial end of the rotor drum body to block fluid communication with the hollow cavity through the axial end of the rotor drum body.
In some embodiments, the air-moving means may include a cooling passage and a plurality of fan blades. The cooling passage may extend axially through the shaft and open into a hollow cavity. The plurality of fan blades may extend radially between and interconnect the shaft and the rotor drum body of the magnetic rotor drum. In this way, rotation of the shaft about the axis may cause the plurality of fan blades to draw the air axially along the shaft in the cooling passage toward the magnetic rotor drum and into the hollow cavity at the first radial distance. Additionally, rotation of the shaft about the axis may cause the plurality of fan blades to urge the air between the plurality of fan blades axially away from the magnetic rotor drum at the second radial distance.
In some embodiments, the shaft may include a first segment and a second segment. The second segment may be spaced apart axially from the first segment.
In some embodiments, the magnetic rotor drum may be located axially between the first segment and the second segment of the shaft. The first segment may be formed to define the cooling passage that is in fluid communication with the hollow cavity. In some embodiments, the second segment of the shaft may be formed without a passage in fluid communication with the hollow cavity.
In some embodiments, the shaft, the rotor drum body of the magnetic rotor drum, and the rotor hub may be integrally formed. The shaft, the rotor drum body of the magnetic rotor drum, and the rotor hub may be integrally formed as a single, one-piece component.
According to another aspect of the present disclosure, an electric machine adapted for use in an aircraft propulsion system may include a shaft extending along an axis, a magnetic rotor drum, and a rotor hub. The shaft may be configured to rotate about the axis. The magnetic rotor drum may include a rotor drum body and a plurality of magnets arranged circumferentially about the axis and coupled with the rotor drum body for rotation therewith. The rotor hub may extend radially between and interconnect the shaft and the rotor drum body.
In some embodiments, the rotor hub may have a plurality of blades. The plurality of blades may be configured to draw air axially along the shaft toward the magnetic rotor drum at a first radial distance and to urge the air axially away from the magnetic rotor drum at a second radial distance different than the first radial distance in response to rotation of the shaft about the axis.
In some embodiments, each of the blades may have a fan blade length and a fan blade chord length. A fan blade ratio of the fan blade length to the fan blade chord length may be about 1. In some embodiments, the plurality of blades may be airfoil shaped.
In some embodiments, the rotor hub may further include a rotor end cap. The rotor end cap may extend radially between and interconnect the shaft and the rotor drum body of the magnetic rotor drum. The plurality of blades may extend axially away from the rotor end cap and away from the magnetic rotor drum. In some embodiments, the rotor end cap may block fluid communication with a hollow cavity through an axial end of the rotor drum body.
In some embodiments, the rotor hub may further include a baffle. The baffle may extend circumferentially around the shaft. The baffle may be spaced apart radially from the shaft and spaced apart axially from the rotor end cap to direct the air along the shaft, around the baffle, and along an outside of the baffle.
In some embodiments, the shaft may be formed to include a cooling passage. The cooling passage may extend axially through the shaft and open into a hollow cavity. The plurality of blades may extend radially between and interconnect the shaft and the rotor drum body of the magnetic rotor drum. In this way, rotation of the shaft about the axis may cause the plurality of blades to draw the air axially through the cooling passage and into the hollow cavity and urge the air between the plurality of blades axially away from the magnetic rotor drum.
In some embodiments, the shaft may include a first segment and a second segment. The second segment may be spaced apart axially from the first segment. The rotor drum body mat be located axially between the first segment and the second segment of the shaft. The first segment may be formed to define the cooling passage that is in fluid communication with the hollow cavity.
In some embodiments, the second segment of the shaft may be formed without a passage in fluid communication with the hollow cavity. The second segment may be formed without a passage in fluid communication with the hollow cavity to block fluid communication through the shaft into the hollow cavity.
In some embodiments, the shaft, the rotor drum body of the magnetic rotor drum, and the rotor hub may be integrally formed. The shaft, the rotor drum body of the magnetic rotor drum, and the rotor hub may be integrally formed as a single, one-piece component.
According to another aspect of the present disclosure, a method may include providing an electric machine having a shaft, a magnetic rotor drum, and a rotor end cap. The magnetic rotor drum may include a rotor drum body and a plurality of magnets. The rotor drum body may extend circumferentially around an axis to define a hollow cavity within the rotor drum body. The plurality of magnets may be arranged circumferentially about the axis and may be coupled with the rotor drum body for rotation therewith.
In some embodiments, the method may further include rotating the electric machine. The electric machine may be rotated such that a plurality of blades included in the rotor end cap draws air axially along the shaft toward the rotor drum body at a first radial distance to transfer heat from the shaft to the air and urges the air axially away from the rotor drum body at a second radial distance greater than the first radial distance. In some embodiments, drawing the air axially along the shaft may include drawing the air between a baffle and the shaft.
These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.
An aircraft 10 having an electric machine 20 in accordance with the present disclosure is shown, for example, in
The electric machine 20 includes a case 22, a stator 24 coupled with the case 22, and a rotor assembly 26 supported by the case 22 as shown in
The electric machine 20 generates heat during use, which may cause the temperature of the rotor assembly 26 to increase without any active cooling. This may reduce the operating life of the electric machine 20. Other rotor cooling systems may use external fans to actively cool the electric machine 20. However, the external fan structure adds weight to the system 16.
Therefore, the rotor assembly 26 of the electric machine 20 includes a rotor hub 32 having air moving means for moving air surrounding the motor toward and away from the rotor assembly 26 of the rotor assembly in response to rotation of the rotor assembly 26 about the axis 11. The air transfers heat from a shaft 28 and a magnetic rotor drum 30 included in the rotor assembly 26 to cool the shaft 28 and the magnetic rotor drum 30.
The air moving means includes a rotor end cap 42A, 42B and an impeller 44A, 44B as shown in
In the illustrative embodiment, the air moving means includes a rotor end cap 42A, 42B and an impeller 44A, 44B and a baffle 46A, 46B for each side of the magnetic rotor drum 30 as shown in
Rotation of the shaft 28 causes the impellers 44A, 44B to draw the air surrounding the electric machine 20 axially along the shaft 28 toward the rotor drum body 34 of the magnetic rotor drum 30, as suggested by arrows 38A, 38B. The air flowing axially along the shaft 28 toward the rotor drum body 34 transfers heat from the shaft 28 to the air. The heated air is then urged axially away from the rotor drum body 34 of the magnetic rotor drum 30, as suggested by arrows 40A, 40B. In the illustrative embodiment, the air moving means draws air axially along the shaft 28 toward the rotor drum body 34 at a first radial distance R1 and urges the air axially away from the rotor drum body 34 at a second radial distance R2 greater than the first radial distance R1.
The rotor hub 32 includes a baffle 46A, 46B that extends circumferentially around the shaft 28 to prevent mixing of the two air flows 38A, 38B or 40A, 40B. Mixing of the air flows 38A, 38B or 40A, 40B may reduce the cooling efficiency.
The baffle 46A, 46B is spaced apart radially from the shaft 28 so as to form a passage 48A, 48B radially therebetween as shown in
In the illustrative embodiment, the rotor hub 32 includes a baffle 46A, 46B for each end of the shaft 28. Each baffle 46A, 46B extends circumferentially around one end of the shaft 28 and is spaced apart radially from the shaft 28 so as to form the passages 48A, 48B radially therebetween.
Turning again to the electric machine 20, the electric machine 20 is powered directly or indirectly from the gas turbine engine 18 and/or one or more batteries. The gas turbine engine 18 combusts compressed air and fuel to produce rotational mechanical power. The rotational mechanical power produced by the gas turbine engine may be directly transferred to the electric machine 20 to drive rotation of the electric machine 20, as contemplated for the illustrative embodiment.
In other embodiments, the rotational mechanical power is used to drive rotation of a generator to produce electrical energy. The electrical energy from the generator may be transmitted to the electric machine 20 to drive rotation of the electric machine 20 and/or may be transmitted to the one or more batteries for storage and use by the electric machine 20 at a later time.
The electric machine 20 includes the case 22, the stator 24, and the rotor assembly 26 as shown in
The rotor assembly 26 includes the shaft 28, the magnetic rotor drum 30, and the rotor hub 32 as shown in
The rotor hub 32 is formed with the air moving means for drawing air surrounding the electric machine 20 axially along the shaft 28 toward the magnetic rotor drum 30 (as suggested by arrows 38A, 38B) to transfer heat from the shaft 28 to the air and for urging the heated air axially away from the rotor drum body 34 of the magnetic rotor drum 30 (as suggested by arrows 40A, 40B) as shown in
The rotor hub 32 includes the rotor end caps 42A, 42B, the impellers 44A, 44B, and the baffles 46A, 46B as shown in
At one end of the shaft 28, the first rotor end cap 42A extends between the shaft 28 and the rotor drum body 34 of the magnetic rotor drum 30 and the first impeller 44A extends axially away from the first rotor end cap 42A. The first baffle 46A arranged around the shaft 28 to define a first passage 48A.
At the other end of the shaft 28, the second rotor end cap 42B extends between the shaft 28 and the rotor drum body 34 of the magnetic rotor drum 30 and the second impeller 44B extends axially away from the second rotor end cap 42B. The second baffle 46B arranged around the shaft 28 to define a second passage 48B.
In the illustrative embodiment, the rotor end caps 42A, 42B and the impellers 44A, 44B provide the air moving means. Rotation of the shaft 28 causes the impellers 44A, 44B to draw the air surrounding the electric machine 20 axially along the shaft 28 through the passages 48A, 48B toward the rotor drum body 34, as suggested by arrows 38A, 38B. The air flowing through the passages 48A, 48B transfers heat from the shaft 28 to the air. Simultaneously, as the air exits the passages 48A, 48B, the impellers 44A, 44B urge the heated air axially away from the magnetic rotor drum 30 along the radial outer face 46AF, 46BF of each of the baffles 46A, 46B, as suggested by arrows 40A, 40B.
Each of the rotor end caps 42A, 42B encases an axial end 34A, 34B of the rotor drum body 34 to close off a hollow cavity 56 of the rotor drum body 34 as shown in
In the illustrative embodiment, the shaft 28, the rotor drum body 34 of the magnetic rotor drum 30, and the rotor end caps 42A, 42B are integrally formed as a single, one-piece component. In other embodiments, the shaft 28, the rotor drum body 34 of the magnetic rotor drum 30, and the rotor end caps 42A, 42B may be formed separately and assembled.
Each of the impellers 44A, 44B includes a plurality of discrete protrusions 50A, 50B as shown in
In illustrative embodiment, the blades 50A, 50B are integrally formed with the respective rotor end cap 42A, 42B and are spaced apart circumferentially around the axis 11 as shown in
Each of the blades 50A, 50B has a fan blade length and a fan blade chord length as shown in
In the illustrative embodiment, a fan blade ratio of the fan blade length to the fan blade chord length is about 1. In other embodiments, the fan blade ratio may be about 0.9. In other embodiments, the fan blade ratio may be between about about 0.9 and 1.1
The shape of the blades 50A, 50B may be altered to increase the cooling of the shaft 28 and rotor drum body 34. Additionally, the direction angle of each of the impellers 44A, 44B may be altered to increase the cooling of the shaft 28 and rotor drum body 34.
In the illustrative embodiment of
Each of the baffles 46A, 46B is spaced apart radially from the shaft 28 and spaced apart axially from the respective rotor end cap 42A, 42B so that the air is drawn axially along the shaft 28 at the first radial distance R1 in the passages 48A, 48B and the air is urged axially away from the magnetic rotor drum 30 at the second radial distance R2 along the radial outer face 46AF, 46BF of the baffles 46A, 46B. The radial distances R1, R2 may be varied by altering the diameter and thickness of the baffles 46A, 46B. In the illustrative embodiment, each of the baffles 46A, 46B is spaced apart axially from the respective rotor end cap 42A, 42B so as to define an inlet opening 52A, 52B and an outlet opening 54A, 54B for the passage 48A, 48B as shown in
A method of cooling the electric machine 20 includes rotating the shaft 28 of the electric machine 20 to cause the plurality of blades 50A, 50B included in the impellers 44A, 44B to draw air axially along the shaft 28 toward the rotor drum body 34 at the first radial distance R1 to transfer heat from the shaft 28 to the air. Rotation of the shaft 28 also causes the plurality of blades 50A, 50B included in the impellers 44A, 44B to urge the air axially away from the rotor drum body 34 at the second radial distance R2.
In the illustrative embodiment, the method includes drawing the air between the baffles 46A, 46B and the shaft 28. Rotation of the shaft 28 causes the plurality of blades 50A, 50B included in the impellers 44A, 44B to draw air through the inlet openings 52A, 52B axially along the shaft 28 in the passages 48A, 48B toward the rotor drum body 34. As the air exits through the outlet openings 54A, 54B of the passages 48, 48B, the impellers 44A, 44B urge the air axially away from the rotor drum body 34.
Another embodiment of an electric machine 220 in accordance with the present disclosure is shown in
The electric machine 220 includes a case (not shown), a stator 224, and a rotor assembly 226 as shown in
The rotor assembly 226 includes a shaft 228, the magnetic rotor drum 230, and a rotor hub 232 as shown in
The rotor hub 232 is formed with the air moving means for drawing air surrounding the electric machine 220 axially along the shaft 228 toward the rotor drum body 234 (as suggested by arrows 238A, 238B) to transfer heat from the shaft 228 to the air and for urging the heated air axially away from the rotor drum body 234 of the magnetic rotor drum 230 (as suggested by arrows 240A, 240B) as shown in
The rotor hub 232 includes a cylindrical body 242 and a plurality of fan blades 244A, 244B. The cylindrical body 242 extends around the axis 11 to define a hollow cavity 256. The plurality of fan blades 244A, 244B that extend radially between the shaft 228 and the cylindrical body 242 to draw air axially along the shaft 228 toward the rotor drum body 234 to transfer heat from the electric machine 220 and urge the air axially away from the rotor drum body 234. The plurality of fan blades 244A, 244B draws the air toward the rotor drum body 234 at the first radial distance R1 and urges the air axially away from the rotor drum body 234 at the second radial distance R2 greater than the first radial distance R1 as shown in
The shaft 228 is formed to include a cooling passage 248 that extends axially through the shaft 228 and opens into the hollow cavity 256 of the cylindrical body 242 of the rotor hub 232 as shown in
In the illustrative embodiment, the shaft 228 includes a first segment 228A and a second segment 228B that are each coupled with rotor hub 232 on opposite sides of the rotor hub 232 as shown in
Either the first segment 228A or the second segment 228B may be formed with the cooling passage 248 that is in fluid communication with the hollow cavity 256. In the illustrative embodiment, the first segment 228A is formed to define the cooling passage 248, while the second segment 228B is formed without a cooling passage that extends therethrough and fluidly opens into the hollow cavity 256. The cooling passage 248 extends through a radial center 228C of the shaft 228 in the illustrative embodiment.
In the illustrative embodiment, the rotor hub 232 includes first and second sets of fan blades 244A, 244B as shown in
Like the plurality of first fan blades 244A, the plurality of second fan blades 244B also moves air surrounding the electric machine 220 in response to rotation of the shaft 228 about the axis 11. The plurality of second fan blades 244B urges the air between the plurality of second fan blades 244B axially away from the magnetic rotor drum 230 at the second radial distance R2.
Each of the blades 250A, 250B has a fan blade length and a fan blade chord length. The fan blade length is the length of the blade 250A, 250B from a base of the blade 250A, 250B to a tip of the blade 250A, 250B. The chord length is the length of the blade 250A, 250B from a leading edge to a trailing edge of the blade 250A, 250B.
In the illustrative embodiment, a fan blade ratio of the fan blade length 51 to the fan blade chord length is about 1. In other embodiments, the fan blade ratio may be about 0.9. In other embodiments, the fan blade ratio may be between about about 0.9 and 1.1
In the illustrative embodiment, the cooling passage 248 and the plurality of first and second fan blades 244A, 244B provide the air moving means. Rotation of the shaft 228 causes the plurality of first fan blades 244A to draw the air surrounding the electric machine 220 axially along the shaft 228 in the cooling passage 248 toward the rotor drum body 234 and into the hollow cavity 256, as suggested by arrows 238A, 238B. The air flowing through the cooling passage 248 transfers heat from the shaft 228 to the air. Simultaneously, as the air exits the cooling passage 248, the plurality of first and second fan blades 244A, 244B urge the air in the hollow cavity 256 axially away from the magnetic rotor drum 230, as suggested by arrows 40A, 40B.
In the illustrative embodiment, the shaft 228 and the rotor hub 232 are formed as a single, one-piece component as shown in
The cylindrical body 242 includes a ring 260 and at least one key feature 262, 264 as shown in
A method of cooling the electric machine 220 includes rotating the shaft 228 of the electric machine 220 to cause the plurality of fan blades 244A, 244B to draw air axially along the shaft 228 toward the rotor drum body 234 at the first radial distance R1 to transfer heat from the shaft 228 to the air. Rotation of the shaft 228 also causes the plurality of fan blades 244A, 244B to urge the air axially away from the rotor drum body 234 at the second radial distance R2.
In the illustrative embodiment, the method includes drawing the air along the shaft 228 in the cooling passage 248. Rotation of the shaft 228 causes the plurality of fan blades 244A, 244B to draw air through the cooling passage 248 into the hollow cavity 256. As the air exits into the hollow cavity 256, the plurality of fan blades 244A, 244B urge the air axially away from the rotor drum body 234 on either side of the rotor drum body 234.
The present disclosure relates to an electric machine 20, 220 with integrated cooling to the rotor assembly 26 as shown in
Other electric machine may include external fans as a separate structure. However, the external fans add additional weight. Therefore, the present disclosure relates to active cooling means which is integrated into the rotor assembly 26, 226 of the electric machine 20, 220 to optimize performance of the electric machine 20, 220.
In the illustrative embodiment of
As the rotor assembly 26 rotates, the air is driven to flow as the rotor drum body 34 to dissipate heat from the plurality of magnets 36, which reduces the temperature of the rotor assembly 26. Therefore, no external pumping means is needed to move cooling air into the rotor assembly 26, which also helps reduce the overall weight and complexity of the electric machine 20.
The impellers 44A, 44B are coupled to the rotor end caps 42A, 42B to draw cooling air through the inlet openings 52A, 52B as shown in
As the rotor assembly 26 rotates, air is drawn from the inlet openings 52A, 52B and flows along the shaft 28 in the cooling passages 48A, 48B to transfer heat and cool the rotor assembly 26. The flow is then directed radially outwards by the impellers 44A, 44B to dissipate the heat from the permanent magnets 36. The flow direction then changes and flows away from the magnetic rotor drum 30 radially outward of the baffles 46A, 46B.
The impellers 44A, 44B may be a non-magnetic material and coupled to the rotor end caps 42A, 42B. In this way, the impellers 44A, 44B may not influence the electromagnetic performance of the magnetic rotor drum 30. The impellers shape and direction angle may be optimized to further enhance the cooling of the rotor assembly 26.
In the illustrative embodiment of
In the illustrative embodiment, the shaft 28, the rotor drum body 34, and the rotor end caps 42A, 42B may be formed by CNC machining or milling. Similarly, the shaft 228, the cylindrical body 242, the blades 244A, 244B may be formed as a single-piece component by CNC machining or milling.
For the purposes of the present disclosure, the modifier about means±1% of the given value. Of course, greater or lesser deviation is contemplated and may be used in processed method within the spirit of this disclosure.
While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.