ELECTRIC MACHINE WITH INTEGRATED COOLING SYSTEM

Abstract

An electric machine includes a housing having cylindrical outer walls including a stator portion and a cooling system portion adjacent to the stator portion. The electric machine includes a rotor drive shaft protruding coaxially with the cylindrical outer walls of the electric machine from the front of the electric machine, and a rotor coupled to the rotor drive shaft and arranged coaxially within the stator portion of the cylindrical outer walls of the machine housing. At least one air inlet is formed in the cylindrical outer walls of the machine housing between the stator portion and the cooling system portion. At least one air guide vane extends from the air inlet into a hollow volume of the rotor forming a cooling air duct from the air inlet past the inner surface of the rotor and back to the inner surface of the cooling system portion.

Claims

1. An electric machine with an integrated cooling system, the electric machine comprising: a machine housing having cylindrical outer walls, the outer walls including a stator portion at a front and a cooling system portion at a back, the cooling system portion lying adjacent to the stator portion; a rotor drive shaft protruding coaxially with the cylindrical outer walls of the electric machine from the front of the electric machine; a rotor coupled to the rotor drive shaft and positioned coaxially within the stator portion of the cylindrical outer walls of the machine housing; at least one air inlet formed in the cylindrical outer walls of the machine housing between the stator portion and the cooling system portion; and at least one air guide vane extending from the air inlet into a hollow volume of the rotor, the at least one air guide vane forming a cooling air duct from the air inlet past an inner surface of the rotor and back to an inner surface of the cooling system portion.

2. The electric machine according to claim 1, further comprising: a heat exchanger integrated into outer walls of the cooling system portion.

3. The electric machine according to claim 2, wherein the heat exchanger includes radially or diagonally oriented airflow deflectors, allowing air to stream through the outer walls of cooling system portion in a location of the heat exchanger.

4. The electric machine according to claim 2, wherein the heat exchanger is integrated into at least one ring segment of the cylindrical outer walls of the cooling system portion, the at least one ring segment spanning over between about 90 and about 360 of the cylindrical outer walls.

5. The electric machine according to claim 1, further including: an airflow separation baffle member located concentrically with outer walls of the cooling system portion within the cooling system portion, the airflow separation baffle member forming an airflow ring between an outer surface of the airflow separation baffle member and the inner surface of outer walls of the cooling system portion.

6. The electric machine according to claim 5, wherein the airflow separation baffle member protrudes at least partially into the hollow volume of the rotor.

7. The electric machine according to claim 5, wherein the airflow separation baffle member encloses a liquid reservoir configured to hold a heat exchanger fluid.

8. The electric machine according to claim 1, wherein the machine housing includes an axial airflow outlet at the back of the cylindrical outer walls.

9. An electric propulsion system for an airborne vehicle, the electric propulsion system comprising: an engine nacelle; a propeller fan installed in the engine nacelle; an electric machine according to claim 1, the electric machine being operable as an electric motor; and a fan shaft coupled to the propeller fan, the rotor drive shaft of the electric machine being connected to the fan shaft.

10. The electric propulsion system according to claim 9, further comprising: a core housing installed within the engine nacelle, the core housing forming a first airflow duct between an inner surface of the engine nacelle and an outer surface of the core housing and a second airflow duct between an inner surface of the core housing and an outer surface of the machine housing of the electric machine.

11. An airborne vehicle, comprising an electric propulsion system according to claim 9.

12. An electric energy generation system for a wind turbine, the electric energy generation system comprising: an engine nacelle; a turbine fan installed in the engine nacelle; an electric machine according to claim 1, the electric machine being operable as an electric generator; and a fan shaft coupled to the turbine fan, the rotor drive shaft of the electric machine being connected to the fan shaft.

13. The electric energy generation system according to claim 12, further comprising: a core housing installed within the engine nacelle, the core housing forming a first airflow duct between an inner surface of the engine nacelle and an outer surface of the core housing and a second airflow duct between an inner surface of the core housing and an outer surface of the machine housing of the electric machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The disclosure herein will be explained in greater detail with reference to exemplary embodiments depicted in the drawings as appended.

[0024] The accompanying drawings are included to provide a further understanding of the disclosure herein and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the disclosure herein and together with the description serve to explain the principles of the disclosure herein. Other embodiments of the disclosure herein and many of the intended advantages of the disclosure herein will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

[0025] FIG. 1 schematically illustrates a cross-sectional view of an engine nacelle of an electric propulsion system having an electric machine according to some embodiments of the disclosure herein.

[0026] FIG. 2 schematically illustrates a cross-sectional view of an electric machine according to other embodiments of the disclosure herein that could be used in an electric propulsion system as shown in FIG. 1.

[0027] FIG. 3 schematically illustrates a cross-sectional view of an electric machine according to other embodiments of the disclosure herein that could be used in an electric propulsion system as shown in FIG. 1.

[0028] In the figures, like reference numerals denote like or functionally like components, unless indicated otherwise. Any directional terminology like top, bottom, left, right, above, below, horizontal, vertical, back, front, and similar terms are merely used for explanatory purposes and are not intended to delimit the embodiments to the specific arrangements as shown in the drawings.

DETAILED DESCRIPTION

[0029] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the disclosure herein. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0030] FIG. 1 shows a schematic illustration of a cross-sectional view through an engine nacelle 16. The engine nacelle 16 may be that of an electric propulsion system generally designated 10 having an electric machine 1. Alternatively, the electric machine 1 may be part of an electric energy generation system 10 and the engine nacelle 16 may be a wind turbine nacelle. The electric machine 1 may be operated as an electric motor, i.e. an electrical machine that converts electrical energy into mechanical energy. The electric machine 1 may also be operated as an electric generator, i.e. an electrical machine operating in the reverse direction to an electric motor, thereby converting mechanical energy into electrical energy.

[0031] FIGS. 2 and 3 show alternative variations of the electric machine 1 that may be used as a core component within the engine nacelle 16 of the electric propulsion system 10 or the electric energy generation system 10 instead of the electric machine 1 explicitly shown in FIG. 1. It should be understood that distinct features of the variations shown in FIGS. 2 and 3 may be incorporated in the electric machine 1 of FIG. 1 and vice versa. Combinations of features taken from one of the FIG. 2 or 3 with other features taken from the electric machine of FIG. 1 may be used as well.

[0032] The electric machine 1 generally includes a machine housing having cylindrical outer walls. These outer walls include a stator portion 2 at the front (without limitation of generality shown to the left-hand side of the drawings) and a cooling system portion 6 at the back (without limitation of generality shown to the right-hand side of the drawings). The cooling system portion 6 lies adjacent to the stator portion 2, i.e. the cooling system portion 6 and the stator portion 2 are part of a commonly formed cylindrical shell, only interrupted by one or more air inlets 8 formed within the outer walls of the machine housing between the stator portion 2 and the cooling system portion 6.

[0033] The stator portion 2 may have stator coils or stator windings to be connected to an electric energy storage 19 of the system 10. The electric machine 1 is formed in an in-runner configuration, meaning that there is a rotor 3 coupled to a rotor drive shaft 4, the rotor 3 being generally arranged coaxially within the hollow defined by the stator portion 2 of the machine housing. The rotor 3 may also have magnets, magnetizable coils or windings as appropriate for the type of electric machine.

[0034] The rotor drive shaft 4 protrudes coaxially with the cylindrical outer walls of the electric machine 1 from the front of the electric machine 1. This rotor drive shaft 4 may be coupled to a fan shaft connecting to a turbine fan 11 (in case of a wind turbine) or a propeller fan 11 (in case of an electric propulsion system for an aircraft) mounted to a fan rotor hub 14. The propeller or turbine fan 11 may be held in place by support members 12, for example a combined fan stator and support struts, structurally coupling a core housing 15 within the engine nacelle 16. The core housing 15 serves to encapsulate the engine 1 within the nacelle 16. The core housing 15 forms a first airflow duct A1 between the inner surface of the engine nacelle 16 and the outer surface of the core housing 15. A second airflow duct A2 leads between the inner surface of the core housing 15 and the outer surface of the machine housing of the electric machine 1. The dimensioning of the core housing 15 in relation to the machine housing of the electric machine on one hand and the nacelle 16 on the other hand may be chosen such that the ratio between the amount of air passing through the first and second airflow duct, respectively, is controlled as desired. Moreover, there may be adjustable nozzles (not explicitly shown in FIG. 1) installed at or in the support structure 12 so that the ratio between airflow through the two airflow ducts A1 and A2 may be adjusted as desired. It may also be possible to provide an at least partial or complete blockage of the airflow duct A2 at the end of the passage between the cooling system portion 6 and the core housing so that most of the air or all air flowing through the airflow duct A2 is forced through the heat exchanger 5. This could be arranged for by providing ring-shaped blockage elements on the support structure element 18 which interconnects the core housing, the nacelle 16 and the cooling system portion 6 at its aft end. The ring-shaped blockage elements may be partially open for an airflow streaming through or may entirely shut off the outlet between the outer surface of the cooling system portion 6 and the inner surface of the core housing 15 at the aft end of the electric machine Additionally, blower elements 13 may be provided in the airflow duct A2 which act as an airflow booster for air streaming through the airflow duct A2.

[0035] Air streaming through the second airflow duct A2 passes on the outside of the machine housing and partially streams radially through the one or more air inlets 8. This partial stream serves as cooling airflow for the rotor. It is guided towards the front past the rotor and cools the rotor components on its way. To that end, there is at least one air guide vane 7 that extends from the air inlet 8 into a hollow volume of the rotor 3. The air guide vane 7 forms a cooling air duct from the air inlet 8 past the inner surface of the rotor 3 and back to the inner surface of the cooling system portion 6. The airflow, having reached the end of the air guide vane 7 within the hollow volume of the rotor 3, is turned by 180 and flows to the back until it reaches the cooling system portion 6.

[0036] A heat exchanger 5 is integrated into the outer walls of the cooling system portion 6. The main cooling air flow may enter the heat exchanger 5 from the outside surface of the outer walls of the machine housing may join the rotor cooling airflow to leave the assembly axially through the rear at an axial airflow outlet at the back of the cylindrical outer walls of the machine housing. The heat exchanger 5 may also be split in two or more distinct cooling loops for different components. For example, a first cooling loop of the heat exchanger 5 may be used for cooling the stator parts of the electric machine 1 with a first cooling fluid, while a second cooling loop of the heat exchanger 5 may be used for cooling power electronics components using a second cooling fluid of different type than the first cooling fluid. Further cooling loops may also be used for other heat sources such as the electric energy storage 19 of FIG. 1.

[0037] As most of the heat dissipation may be expected to happen in the stator and/or in power electronics components, the heat exchanger 5 may give off heat from the stator and/or the power electronics components. The airflow through the heat exchanger 5 may be radial or diagonal. To that end, the heat exchanger 5 may include radially or diagonally oriented airflow deflectors. The airflow deflectors allow air to stream from the second airflow duct A2 through the outer walls of cooling system portion 6 where the heat exchanger 5 is located. Diagonally running airflow may lead to fewer losses through flow deflection, but might be more complicated to manufacture.

[0038] The heat exchanger 5 is integrated into at least one ring segment of the cylindrical outer walls of the cooling system portion 6. This ring segment may span over about 360 of the cylindrical outer walls. Alternatively, there may be more than one ring segment, each ring segment spanning over only a portion of 360 of the cylindrical outer walls. It may also be possible to integrate a heat exchanger 5 in only parts of the outer walls, such as for example spanning about 90 of the cylindrical outer walls. Such configuration may be advantageous if there is additional need for installation space, for example for electric connections or pipework for the fluid pipes for the heat exchanger 5.

[0039] As shown in FIGS. 1, 2 and 3, different airflow separation baffle members 9 may be located concentrically with the outer walls of the cooling system portion 6 within the cooling system portion 6. For example, in FIG. 2, the airflow separation baffle member 9 is located entirely within the cooling system portion 6. The airflow separation baffle member 9 allows forming an airflow ring between the outer surface of the airflow separation baffle member 9 and the inner surface of the outer walls of the cooling system portion 6, thereby guiding air streaming back from the air guide vanes 7 towards the inner surfaces of the heat exchanger 5. The airflow separation baffle member 9 aids in creating the necessary airflow velocity difference between the inner side and the outer side of the heat exchanger 5 to have air pass through the heat exchanger 5.

[0040] As illustrated in FIG. 1, the airflow separation baffle member 9 may also at least partially protrude into the hollow volume of the rotor 3. For example, the airflow separation baffle member 9 may enclose a liquid reservoir R that is configured to hold a heat transfer fluid for use in the heat exchanger 5. Also, the airflow separation baffle member 9 may enclose other pumping equipment for use with the heat exchanger 5.

[0041] The airflow separation baffle member 9 may also close off the back of the machine housing, as illustrated in FIG. 3, so that the rotor cooling air is forced through the heat exchanger 5 back to the second airflow duct A2. This may be advantageous if the rotor needs only little cooling and air radially entering the air inlet 8 is sufficiently cool after having cooled the rotor to cool the stator and/or power electronics components as well. Such a configuration may be favorable for wind turbines aiding in producing a more laminar and stable airflow at the back of the electric machine 1.

[0042] The airflow separation baffle member 9 may be coupled to supporting members 17, 18 at the back of the engine nacelle 16 to mechanically stabilize and support the machine housing within the nacelle 16.

[0043] The integrated cooling system equipment can be installed with or without shielding. Additional flow guides might help to improve air flow distribution and protect the cooling system equipment, particularly the heat exchanger 5, from the environment. In the case of encapsulated equipment, outside (colder, lower pressure) air could be routed to the cooling equipment for additional cooling. As the cooling system is located close to the electric machine 1, there is less need for extensive piping, thereby reducing weight of the electric machine 1 and balancing pressure distribution in the fluid pumping system of the heat exchanger 5. Also, the proximity of the liquid reservoir R as tank for heat exchanger fluid leads to less entrapped coolant volume, further reducing the necessary tank size and weight.

[0044] As any of the electric machines 1 as depicted in FIG. 1, 2 or 3 may be mounted as a unit in an engine nacelle 16, there is no need for breaking open or re-connecting the cooling circuit, therefore eliminating the danger of foreign object damage to the cooling customer. However, if required, the cooling system could be accessed from the rear, for example if required for on-wing maintenance in an electric propulsion system for an airborne vehicle.

[0045] Airflow by the fan 13 (or turbine 13) is not impeded by the installation of the cooling system. The electric machine 1 may be installed closely to the fan casing 15 so that cantilever forces are reduced substantially. The cooling system the components of which are generally lighter than components of the electric machine are shifted to the rear of the machine 1, thereby reducing dynamic forces even further.

[0046] In the foregoing detailed description, various features are grouped together in one or more examples or examples with the purpose of streamlining the disclosure. It is to be understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents. Many other examples will be apparent to one skilled in the art upon reviewing the above specification. In particular, the embodiments and configurations described for the systems and aircraft infrastructure can be applied accordingly to the aircraft or spacecraft according to the disclosure herein and the method according to the disclosure herein, and vice versa.

[0047] The embodiments were chosen and described in order to best explain the principles of the disclosure herein and its practical applications, to thereby enable others skilled in the art to best utilize the disclosure herein and various embodiments with various modifications as are suited to the particular use contemplated. In the appended claims and throughout the specification, the terms including and in which are used as the plain-English equivalents of the respective terms comprising and wherein, respectively. Furthermore, a or one does not exclude a plurality in the present case.

[0048] While at least one example embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the example embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a, an or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.