Electrical machine and thermal turbomachine

Abstract

The invention relates to an electrical machine (1) having a rotor, a stator (3) and a stator sleeve (4) surrounding the stator (3), wherein a cooler (5) which can be supplied with cooling air is arranged on the outer circumference of the stator sleeve (4) and, together with a housing part (6) of the electrical machine (1), delimits an axial gap (8) into which a cooling air outlet (7) of the cooler (5) opens. According to the invention, at least one cooling air channel (10) formed in the housing part (6) is located opposite the cooling air outlet (7) at the axial gap (8), via which cooling air channel (10) the cooling air outlet (7) is connected to a region to be cooled that is arranged further radially inward. The invention further relates to a thermal turbomachine (2) having an electrical machine (1) according to the invention.

Description

[0001] R.415066

[0002] - 1 -

[0003] Description

[0004] Electric machine and thermal turbomachine

[0005] The invention relates to an electric machine with the features of the preamble of claim 1. Furthermore, the invention relates to a thermal turbomachine with an electric machine according to the invention. The thermal turbomachine may, in particular, be an air compressor.

[0006] Preferred application areas are fuel cell systems in which thermal turbomachines are used for air compression.

[0007] State of the art

[0008] The electrochemical reaction in the fuel cells of a fuel cell system requires a certain air mass flow rate and a certain pressure level. The air supplied to the fuel cells is therefore compressed beforehand using a thermal turbomachine. The thermal turbomachine can be single-stage or multi-stage, as well as single- or multi-flow. Furthermore, it can be coupled with an exhaust turbine for energy recuperation.

[0009] The drive system of a thermal turbomachine comprises an electric machine with a rotor and a stator. The rotor is connected to a drive shaft on which a compressor impeller and, if applicable, a turbine impeller are mounted. The shaft is typically rotatably mounted via two radial bearings and one axial bearing. To ensure the oil-free operation required in fuel cell systems, these bearings are designed as gas or air bearings. The load-bearing capacity of the air bearing is achieved by an air cushion in the bearing gap. During operation, friction occurs in the bearing gap, generating heat. Additional heat is introduced via the electric machine. This heat must be dissipated. R.415066

[0010] - 2 -

[0011] Air, previously compressed by the thermal turbomachine, can be used to dissipate heat. Since the air heats up considerably during compression, it is first cooled. A cooler is integrated into the thermal turbomachine for this purpose. The air cooled by the cooler can then be supplied as cooling air to the areas requiring cooling, particularly the bearings and the rotor and / or stator of the electric machine. Routing the cooling air from the cooler to the areas requiring cooling is problematic because the available installation space is limited. Furthermore, the necessary insulation clearances to the live components of the electric machine must be maintained.

[0012] The present invention is therefore concerned with the objective of optimizing the cooling air flow in a thermal turbomachine.

[0013] To solve the problem, an electric machine with the features of claim 1 is proposed. Advantageous embodiments of the invention are described in the dependent claims. Furthermore, a thermal turbomachine is described.

[0014] Disclosure of the invention

[0015] The invention proposes an electric machine comprising a rotor, a stator, and a stator sleeve surrounding the stator. A cooler, capable of supplying cooling air, is arranged on the outer circumference of the stator sleeve. This cooler, together with a housing part of the electric machine, defines an axial gap into which a cooling air outlet of the cooler opens. According to the invention, at least one cooling air channel formed in the housing part is located opposite the cooling air outlet at the axial gap. The cooling air outlet is connected to a region to be cooled, located further radially inside the housing part, via this channel.

[0016] The at least one cooling air channel formed in the housing part enables radial cooling air flow and thus ensures the connection of the cooler's cooling air outlet to a further radially inwardly located area to be cooled. Since the at least one cooling air channel is integrated into the housing part, its formation does not require any additional installation space; rather, it utilizes the available space. R.415066

[0017] - 3 - The available installation space is utilized. Because at least one cooling air channel is located opposite the cooling air outlet of the cooler at the axial gap, it is positioned outside the outer diameter of the stator. In this way, the necessary insulation distances are maintained.

[0018] When the electric motor is used in a thermal turbomachine, at least one cooling air channel formed in the housing allows cooling air to flow from a radially outer cooler to the radially inner bearings of a shaft connected to the rotor of the electric motor. This ensures effective cooling of the bearings. Furthermore, the waste heat from the electric motor can be dissipated via this cooling air channel.

[0019] Preferably, the at least one cooling air channel is designed as a groove or recess open towards the axial gap. This means that the cooling air channel is not enclosed on all sides, but open towards the cooler. This simplifies the manufacture of the at least one cooling air channel, especially if the at least one cooling air channel is molded into the housing part during its manufacture or subsequently incorporated into the housing part, for example by milling.

[0020] Preferably, the at least one cooling air duct opens into an annular duct. The cooling air can be distributed circumferentially via the annular duct. The annular duct is arranged radially inside the cooling air duct, so that the cooling air is distributed circumferentially over the outer diameter of the stator sleeve or the stator, or in an area between them. In this way, effective cooling of the electric machine, particularly the stator, can be achieved.

[0021] The annular channel is preferably bounded axially on one side by an end face of the stator sleeve and on the other side by the housing part. This ensures that the annular channel lies outside the outer diameter of the stator. Preferably, the housing part has a circumferential recess in the area of ​​the annular channel that widens the annular channel, so that the formation of the annular channel does not require any additional installation space. Alternatively or additionally, the end face of the stator sleeve can have a recess. R.415066

[0022] - 4 -

[0023] As a further development measure, it is proposed that the at least one cooling air duct formed in the housing section be bounded by a duct wall that, at least in sections, has a curved shape to direct the cooling airflow. The curved shape of the duct wall allows the cooling air flowing through the duct to be redirected in a flow-optimized manner. This redirection is intended to facilitate the entry of the cooling air into the annular duct. Alternatively or additionally, it is proposed that the at least one cooling air duct be bounded by a duct wall that runs substantially tangentially, at least in sections. This measure allows the cooling airflow to be directed in a specific circumferential direction, thus defining the flow direction of the cooling air in the annular duct.

[0024] Furthermore, it is proposed that a geometry be formed within the at least one cooling air duct for steering and / or dividing the cooling airflow. By steering the cooling airflow, it can be directed to a specific area. By dividing the cooling airflow, partial flows can be created that are directed to different areas for cooling. For example, the cooling airflow can be divided into a first partial flow and a second partial flow using the geometry. These can then be further steered by the geometry so that, upon entering the annular duct, the first partial flow passes through the annular duct in a first flow direction and the second partial flow passes through the annular duct in a second flow direction. To steer the partial flows, the geometry can have angled side walls, forming ramps over which the partial flows are directed in their respective flow directions.The geometry can have side walls that diverge towards the annular channel, thus widening the geometry in that direction. Preferably, the geometry is arranged centrally within the at least one cooling air channel, so that the cooling air partial flows created by the geometry are at least approximately equal in size. If this is not desirable, for example, if one area needs to be cooled more than another, this can be achieved by an asymmetrical shape and / or arrangement of the geometry.

[0025] Advantageously, the flow cross-sectional area of ​​the at least one cooling air duct is at least half the size of the flow cross-sectional area of ​​the R.415066.

[0026] - 5 -

[0027] Cooler. If multiple cooling channels are provided, the sum of the cross-sectional area of ​​the multiple cooling channels must be at least half the cross-sectional area of ​​the cooler. This ensures that a sufficient amount of cooling air leaves the cooler and is supplied to the area to be cooled. A cross-sectional area of ​​at least one cooling air channel that is at least equal to or even larger than the cross-sectional area of ​​the cooler is particularly advantageous, enabling even more efficient cooling.

[0028] According to a preferred embodiment of the invention, the housing part is made of metal, preferably aluminum. Manufacturing it from metal increases the robustness of the housing part. Manufacturing it from aluminum ensures high robustness while maintaining a low weight of the housing part.

[0029] Preferably, the housing part is a casting, and the at least one cooling air channel is molded into the casting. As a casting, the housing part can be manufactured simply and cost-effectively. Furthermore, complex geometries can be achieved using the mold. This simplifies the formation of the at least one cooling air channel. Additionally, subsequent machining of the housing part to create the at least one cooling air channel is eliminated. Material is also saved.

[0030] Alternatively, the at least one cooling air channel can be integrated into the housing component using a material-removing process, such as milling. In this case, the housing component containing the at least one cooling air channel can be manufactured using conventional methods, allowing the use of existing equipment. Furthermore, an existing, conventionally manufactured housing component can be retrofitted.

[0031] Since the proposed electric machine can be used particularly in a thermal turbomachine, a thermal turbomachine with a compressor impeller and / or turbine impeller arranged on a shaft, as well as an electric machine according to the invention for driving the shaft, is further proposed. The cooling of the thermal R.415066 can be achieved with the aid of the electric machine according to the invention.

[0032] - 6 -

[0033] The turbomachine can be improved, both on the compressor side and on the turbine side, provided the thermal turbomachine has a turbine.

[0034] In a further development of the invention, it is therefore proposed that the housing part having at least one cooling air channel is arranged in the area of ​​the compressor impeller and / or the turbine impeller.

[0035] A preferred embodiment of the invention is described in more detail below with reference to the figures. These show:

[0036] Fig. 1 shows a longitudinal section through an electric machine according to the invention in the area of ​​a cooling air duct for connecting a cooling air outlet of a cooler to an area to be cooled and

[0037] Fig. 2 shows a cross-section through the electric machine of Figure 1 in the area of ​​the cooling air duct.

[0038] Detailed description of the drawings

[0039] Figure 1 shows an electric machine 1, which in this case serves to drive a thermal turbomachine 2. The illustrated electric machine 1 comprises a rotor (not shown), a stator 3, and a stator sleeve 4 surrounding the stator 3. Air, which has been previously compressed by the thermal turbomachine 2, is used to cool the thermal turbomachine 2. Since this air is heated considerably by the compression process, it must be cooled to ensure effective cooling of the thermal turbomachine 2. Therefore, a cooler 5 is arranged on the outer circumference of the stator sleeve 4, to which the air previously compressed by the thermal turbomachine 2 is supplied for cooling.

[0040] The cooler 5 and the stator sleeve 4 are surrounded by a housing part 6 of the electric machine 1. This results in an axial gap 8 between the cooler 5 and the housing part 6. A cooling air outlet 7 of the cooler 5, located at its end face, opens into this gap. Since the axial gap 8 is very narrow, neither distribution nor guidance of the cooling air can occur through it.

[0041] - 7 - are achieved. The cooling air outlet 7 of the cooler 5 is therefore opposite at least one cooling air channel 10 at the axial gap 8, which is formed in the housing part 6. Since the cooling air channel 10 runs essentially radially, this connects the cooling air outlet 7 to a further radially inner area, in this case to an annular channel 12. The cooling air is then distributed circumferentially via this channel. The annular channel 12 is bounded axially on one side by an end face 11 of the stator sleeve 4 and on the other side by the housing part 6. The housing part 6 has a circumferential recess 9 for this purpose. A further circumferential recess 13 is provided in the end face 11 of the stator sleeve 4, so that the annular channel 12 is widened by this recess.

[0042] As can be seen in Figure 1, the at least one cooling air channel 10 formed in the housing part 6 opens into the annular channel 12 outside an outer diameter AD of the stator 3. The outer diameter AD of the stator 3 is, more precisely, the outer diameter of an overmolding 17 of the stator 3. In this way, a radial distance a is maintained between the cooling air channel 10 and the outer diameter AD, which corresponds at least to a required insulation distance.

[0043] As can be seen particularly in Figure 2, the at least one cooling air duct 10 is designed as a groove in the housing part 6, open towards the cooler 5 or the cooling air outlet 7. A geometry 15 is arranged within the cooling air duct 10, which divides the cooling air flow 16 passing through the cooling air duct 10. To obtain approximately equal partial flows, the geometry 15 is arranged centrally. The shape of the geometry 15, which widens towards the annular channel 12, simultaneously directs the partial flows, thus facilitating their entry into the annular channel 12. For further direction of the partial flows, the cooling air duct 10 is bounded on both sides by channel walls 14, which run approximately tangentially and are rounded in transition areas. Upon entering the annular channel 12, a first partial flow is thus directed in one flow direction and a second partial flow in the other flow direction.

Claims

R.415066 - 8 - Claims 1. Electric machine (1) with a rotor, a stator (3) and a stator sleeve (4) surrounding the stator (3), wherein a cooler (5) which can be supplied with cooling air is arranged on the outer circumferential side of the stator sleeve (4), which together with a housing part (6) of the electric machine (1) defines an axial gap (8) into which a cooling air outlet (7) of the cooler (5) opens, characterized in that at least one cooling air channel (10) formed in the housing part (6) is opposite the cooling air outlet (7) at the axial gap (8), via which the cooling air outlet (7) is connected to a further radially inwardly arranged area to be cooled.

2. Electric machine (1) according to claim 1 , characterized in that the at least one cooling air channel (10) is designed as a groove or recess open towards the axial gap (8).

3. Electric machine (1) according to claim 1 or 2, characterized in that the at least one cooling air channel (10) opens into an annular channel (12), which is preferably limited in the axial direction on one side by an end face (11) of the stator sleeve (4) and on the other side by the housing part (6).

4. Electric machine (1) according to claim 3, characterized in that the housing part (6) has a circumferential recess (9) in the area of ​​the annular channel (12) which widens the annular channel (12).

5. Electric machine (1) according to one of the preceding claims, characterized in that the at least one cooling air duct (10) is bounded by a duct wall (14) which, for the purpose of directing the cooling airflow, is arc-shaped and / or substantially tangential. R.415066 - 9 - 6. Electric machine (1) according to one of the preceding claims, characterized in that a geometry (15) is formed within the at least one cooling air duct (10) for steering and / or dividing the cooling airflow, which is preferably arranged centrally.

7. Electric machine (1) according to one of the preceding claims, characterized in that the flow cross-sectional area of ​​the at least one cooling air channel (10) is at least half as large as the flow cross-sectional area of ​​the cooler (5).

8. Electric machine (1) according to one of the preceding claims, characterized in that the housing part (6) is made of metal, preferably of aluminium.

9. Electric machine (1) according to one of the preceding claims, characterized in that the housing part (6) is a casting and the at least one cooling air channel (10) is molded into the casting.

10. Electric machine (1) according to one of claims 1 to 8, characterized in that the at least one cooling air channel (10) has been introduced into the housing part (6) in a material removal process, for example in a milling process.

11. Thermal turbomachine (2) comprising a compressor impeller and / or turbine impeller arranged on a shaft and an electric machine (1) according to one of the preceding claims for driving the shaft.

12. Thermal turbomachine (2) according to claim 11 , characterized in that the housing part (6) having at least one cooling air channel (10) is arranged in the area of ​​the compressor impeller and / or the turbine impeller.

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