EP1844537A1

EP1844537A1 - Motor device with thermosiphon cooling of its superconductive rotor winding

Info

Publication number: EP1844537A1
Application number: EP06704299A
Authority: EP
Inventors: Bernd Gromoll
Original assignee: Siemens AG
Current assignee: Rolls Royce Deutschland Ltd and Co KG
Priority date: 2005-02-02
Filing date: 2006-01-18
Publication date: 2007-10-17
Also published as: WO2006082138A1; CN101111985B; KR100914344B1; KR20070091035A; DE102005004858A1; CN101111985A; US20080164782A1

Abstract

The motor device comprises a motor (2) with a rotor (5) rotating about an axis (A), the superconductive winding (10) of which is coupled to a central refrigerant cavity (12) via a winding support (9) in a thermally conductive manner. The rotor cavity (12) forms a tube system, together with the line sections (22) laterally connected thereto and a condenser chamber (18) of a refrigeration unit (15), located outside the motor (2), in which a refrigerant (k, k') circulates as result of a thermosiphon effect. According to the invention, the refrigerant supply to the central rotor cavity (12) is maintained, even with inclined positions (δ) of the rotor (5), when the rotor cavity (12) is provided with a lining (25) from a porous material, preferably a sintered metal, of high thermal conductivity.

Description

description

Machine setup with thermosyphon cooling of its superconducting rotor winding

The invention relates to a machine device

with a rotor rotatably mounted about a rotation axis and surrounded by a stator, which has at least one rotor winding whose superconductive conductors are thermally coupled to a central, axially extending cylindrical rotor cavity,

- With a located outside the rotor, stationary refrigeration unit with a condenser space and - running between the central rotor cavity and the condenser space of the refrigeration unit, tubular conduit parts.

In this case, the rotor cavity, the tubular conduit parts and the condenser space form a closed conduit system in which a refrigerant can circulate or circulate by utilizing a thermosiphon effect. A corresponding machine device is disclosed in DE 100 57 664 A1.

Since 1987, metal oxide superconductor materials with transition temperatures T _c of more than 77 K have been known. These materials are therefore also referred to as high (high) -T _c superconductor materials or HTS materials and in principle allow a cooling technology with liquid nitrogen (LN ₂ ).

With conductors using such HTS materials, attempts are also being made to create superconducting windings of machines. However, it has been found that hitherto known HTS conductors have a relatively low current carrying capacity in magnetic fields with inductions in the tesla range. This often requires that the conductors of such windings, despite the inherently high transition temperature T _{c of} the used Materials still need to be at a temperature below 77 K temperature level, for example between 10 and 50 K supported ^¬ th to be able to carry so significant at high field strengths occurring flows. Such a temperature level is significantly higher than 4, 2 K, the boiling point of the liquid helium (LHe), cooled with the known metallic superconductor materials with comparatively low transition temperature T _c , called low (low) -T _c materials or LTS materials become .

For cooling windings with HTS conductors in the temperature range below 77 K, preference is given to using refrigeration systems in the form of so-called cryocoolers with a closed He pressure gas circuit. Such cryocoolers are in particular of the Gifford McMahon or Stirling type or are designed as so-called pulse tube coolers. They also have the advantage that their cooling capacity is virtually available at the push of a button and the handling of cryogenic liquids is avoided. When using such refrigeration systems, the superconducting winding is cooled indirectly only by heat conduction to a cold head of a corresponding refrigerator (cf., for example, also "Proc. 16 ^th Int Cryog. Engig. Conf. (ICEC 16)", Kitakyushu, JP, 20.-24.05.1996, Elsevier Science, 1997, pages 1109 to 1129).

A corresponding cooling technique is also provided for the rotor of an electric machine which can be removed from the aforementioned DE 100 57 664 A1. The rotor contains a rotating winding of HTS conductors, which are located in a thermally conductive winding carrier. This winding support is equipped with a central, extending in the axial direction, cylindrical rotor cavity, connect to the side leading out of the winding support tubular tubular parts. These line parts lead into a geodetically higher condenser space of a refrigeration unit and together with this condenser space and the central rotor cavity form a closed single-pipe Line system. This piping system contains a refrigerant that circulates using a so-called thermosiphon effect. In this case, in the condenser space condensed refrigerant is passed through the tubular conduit parts in the central rotor cavity, where it absorbs heat and at least partially evaporated because of the thermal coupling to the winding support and thus to the HTS winding to be cooled. The vaporized refrigerant then passes back over the same line parts in the condenser space, where it is condensed back. The cooling capacity required for this purpose is provided by a chiller whose cold head is thermally coupled to the condenser space. The return flow of the refrigerant toward the parts of the chiller acting as a condenser is driven by a slight overpressure, which forms in the central rotor cavity acting as the evaporator part. This overpressure generated by the formation of gas in the evaporator section and the liquefaction in the condenser space leads to the desired refrigerant return flow. The corresponding circulation is also called natural convection.

Instead of this known single-pipe thermosyphon piping system in which the liquid and the gaseous refrigerant flow through the same pipe parts, two-pipe piping systems for a refrigerant circulation using a thermosiphon effect are known (see, for example, WO 00 / 13296 A). In this case, an additional tube for the gaseous refrigerant must be provided in the region of the hollow shaft of the ^rotor .

In the known machines with thermosiphon cooling thus the transport of the refrigerant takes place solely by utilizing the natural convection, so that no further pumping systems are required. If one wants to use such a machine device on ships or off-shore devices, it is often necessary to use static imbalances, a so-called "trim", of up to ± 5 ° and / or with dynamic ship were to be calculated from up to ± 7, 5 ° in the longitudinal direction. Consequently, in order to obtain approval of a classification society for a ship's mission, the cooling system of such a machine device must ensure reliable cooling. However, if one wishes to allow the abovementioned inclinations of the machine, there is the danger that a region of the tubular conduit parts between the central rotor cavity and the refrigeration unit will be located lower in geodetics than the central rotor cavity itself. The consequence of this is that under the influence of gravity, the refrigerant can no longer reach the rotor cavity to be cooled. A cooling of the machine and thus their operation would not be guaranteed.

To counter this danger, the following suggestions are known, among others:

- A simple solution would be to arrange so inclined the machine against ^¬ to the horizontal that even with maximum hypothetical trim or oscillation amplitude in the thermosiphon line system a slope toward the central rotor cavity is still present. A correspondingly inclined arrangement is undesirable, especially in the case of larger machine lengths, for reasons of a large amount of space then required, especially in shipbuilding.

In principle, the refrigerant can also be forcibly ^circulated by a pump system. However, this requires a out.The ^¬ cher amount of equipment is required, especially when the refrigerant is to be located at a temperature level of examples game, 25 to 30 K. Such Umwälzan ^¬ conditions also require significant losses and can hardly meet the life of shipbuilding with its long maintenance intervals.

Object of the present invention is, therefore, a comprehensive engine with an associated refrigeration unit machines ^¬ device having the above-mentioned features to the effect to design that even with realistic to be assumed slanting /. Imbalances of their rotor, as they can occur when used on ships or off-shore facilities, yet in the central rotor cavity a sufficient cooling effect can be achieved by the refrigerant.

This object is achieved with the given in claim 1 to ^¬ measures. Accordingly, the cen- rale rotor cavity should in Ma ^¬ schin unit with the features mentioned be at least partially provided with a lining made of a porous material of high thermal conductivity, forms the accessible for the refrigerant, capillary ^¬ similar structures or cavities.

The lining according to the invention of the inner wall of a winding carrier enclosing the rotor cavity, which serves as a thermally conductive bridge between the rotor cavity and the superconducting winding, then has the particular advantage that, even with the axis inclined, due to the capillary action, a sufficiently uniform distribution of the cold ^¬ temittels over the surfaces or. Walls of structures or cavities is reached. Such a refrigerant distribution is also supported during operation by the rotation of the structures or cavities. In this way, a good wetting of the porous material is to ensure. Since this material should have a sufficiently high thermal Leitfä ^¬ ability, can be a good thermal coupling arrival of the guarantee to be cooled conductors to the refrigerant.

Advantageous developments of the removable from claim 1 machine device can be found in the dependent claims.

Thus, the porous material may preferably be a

Sintered material, in particular from or with copper (Cu), han ^¬ do. Under a sintered material is in this context understood any material of high thermal conductivity, which is formed by powder metallurgy by pressing and heating while still has a sufficient for the required Kapil ^¬ larity porosity.

The lining of the rotor cavity made of the sintered material may in particular be pressed or shrunk into this. With appropriate methods can be easily realized the desired lining.

Thus, the lining of the porous material may in particular have a porosity of at least 3%, preferably at least 10%, so as to offer for the required capillary action a sufficiently large surface wettable with the refrigerant.

In particular, lining materials whose thermal conductivity is at least 100 W per (meter · Kelvin) at the operating temperature of the superconductive material are to be preferred. In particular, copper (Cu) material readily satisfies this condition because its thermal conductivity has a value greater than the claimed minimum value.

Instead of a liner with a sintered material also ei ^¬ ne is correspondingly porous coating possible.

Further advantageous embodiments of the machine device according to the invention will become apparent from the dependent claims not mentioned above.

For a supplementary explanation of the invention reference will now be made to the drawing, on the basis of which a preferred embodiment of a machine device is described further. This shows in a schematic representation the single figure is a longitudinal section through a fiction, ^¬ designed according to the machine unit.

Machine devices according to the invention each comprise a machine or a machine. a motor and an associated Kälteein ^{¬ unit} . The embodiment of such a machine indicated below with reference to the figures may in particular be a synchronous motor or a generator. The machine comprises a rotating, superconducting winding, which in principle allows the use of metallic LTS material or oxidic HTS material. The latter material is preferably used as the basis for the following embodiment. With appropriate conductors, the winding may consist of a coil or a system of coils in a 2-, 4- or other multipolar arrangement. The basic structure of a corresponding synchronous motor is apparent from the figure, starting from the known from the aforementioned DE 100 57 664 Al embodiment of such a machine.

The designated 2 machine comprises a fixed, located at room temperature outer housing 3 with a stator ^¬ winding 4. Within the outer housing and enclosed by the stator winding ^¬ 4 a rotor 5 is rotatably mounted about a rotation axis A in bearings 6. These bearings may be conventional mechanical bearings or else magnetic bearings ^¬ act. The rotor further comprises a vacuum vessel 7, in which z. B. hollow cylindrical, torque-transmitting suspension elements 8 a winding support 9 is mounted with a HTS winding 10. In this winding support is concentric with the axis of rotation A extending in the axial direction central rotor cavity 12 is present, for example, has a cylindrical shape. The winding support is designed vacuum-tight with respect to this cavity. He seals it on one side of the rotor, the ge from this page by means of a solid axial rotor shaft part 5a ^¬ is superimposed. On the opposite side is the central one Rotor cavity 12 connected to a lateral cavity 13 with a comparatively smaller diameter. This lateral cavity leads from the region of the winding carrier outwardly out of the region of the outer housing 3. A this lateral cavity 13 enclosing, in one of

Bearing mounted, tubular rotor shaft part is denoted by 5b.

For an indirect cooling of the HTS winding 10 via heat-conducting parts of the winding support 9, a refrigeration unit generally designated 15 is provided, of which only a cold head 16 is indicated in more detail. With this in itself most ^¬ th refrigeration unit may involve a cryocooler from the Gifford-McMahon type or, in particular, a regenerative cryocooler such. B. a pulse tube cooler or a split-tube

Stirling coolers act. In this case, the cold head 16 and thus all essential, other parts of the refrigeration unit outside the rotor 5 and. whose outer casing 3.

The cold part of, for example, a few meters laterally of the rotor 5 arranged cold head 16 is in a vacuum vessel 23 via a heat transfer body 17 in good thermal contact with a refrigerant condensation unit having a condenser 18. To this condenser, a vacuum-insulated, stationary heat pipe 20 is attached sen Schlos ^¬ which projects laterally in an axial region in the lateral co-rotating cavity 13 or the central rotor cavity 12th For sealing the heat pipe 20 with respect to the lateral cavity 13, a sealing device 21, which is not further detailed in the figure, is used with at least one sealing element which can be designed as a ferrofluid seal and / or a labyrinth seal and / or a gap seal. Via the heat pipe 20 and the lateral cavity 13 is the central rotor cavity 12 with the heat exchange region of the condenser 18 to the gas-tight seals outside abge ^¬ connected. The between the central rotor cavity 12 and the condenser 18 extending, tubular parts, which serve to receive a refrigerant, are generally referred to as line parts 22. These conduit parts, together with the condenser space 18 and the central rotor cavity 12, are considered to be a conduit system.

These spaces of this line system are filled with a refrigerant, which is selected depending on the desired operating temperature of the HTS winding 10. Thus, for example, are water ^¬ material (condensation temperature 20, 4 K at atmospheric pressure), neon (condensation temperature 27, 1 K at atmospheric pressure), nitrogen (condensation temperature 77, 4 K at atmospheric pressure) or argon (condensation temperature 87, 3 K at atmospheric pressure) in question , Also, mixtures of these gases can be provided. The circulation of the refrigerant takes place under utilization of a so-called thermosiphon effect. For this purpose, the refrigerant is condensed on a cold surface of the cold head 16 in the region of the condenser space 18. Subsequently, the so ver ^¬ flows flüssigte, with k designated refrigerant through the cable ^¬ parts 22 in the central rotor cavity 12. The transport of the condensate occurs while under the influence of gravity.

To this end, may be slightly (by ei ^¬ nige few degrees) in relation to the rotational axis A inclined advantageously the heat pipe 20 so as to flow out of the liquid refrigerant k from the open end 20a of the tube to support the twentieth The liquid refrigerant is then evaporated ver ^¬ inside the rotor. The vaporous refrigerant is denoted by k ^Λ . This refrigerant vaporized with the absorption of heat then flows through the interior of the line parts 22 back into the condenser 18. In this case, the return flow is fanned by a slight overpressure in acting as an evaporator rotor cavity 12 in the direction of the condenser 18 through the emergence caused by gas in the evaporator and the liquefaction in the condenser space. Since the circulation of the liquefied refrigerant from the condenser space 18 into the central rotor cavity 12 and the return flow of the evaporated refrigerant k ^Λ from this rotor cavity back to the condenser space in the from the condenser 18, the line Share 22 and the rotor cavity 12 formed tubular conduit system is carried out, can be spoken of a single-pipe system with a circulation of the refrigerant k, k ^Λ using a thermosiphon effect. Of course, it is also possible to use known multitube line systems for the machine device according to the invention, which enable a circulation of the thermosyphon.

As can also be seen from the figure, may, for a single 2 set the machine to vessels or off-shore facilities, a misalignment occur, in which the axis of rotation A ge ^¬ genüber the horizontal H at an angle δ is inclined by a few degrees. Then, although there is still a condensation of the refrigerant in the condenser 18; However, the refrigerant can no longer reach the central rotor cavity 12, so that then the line parts 22 in particular in the near-axis region gradually filled with liquid refrigerant k. In a relatively small filling quantity of refrigerant Leitungssys ^¬ tems with the rotor interior may then respectively. the rotor cavity 12 run dry and is therefore no longer cooled. With a larger filling amount of the line system, the return flow of the gaseous refrigerant k ^{Λ is} blocked in the line parts 22 to the condenser 18 after a certain time by accumulated liquid refrigerant. A safe cooling of the rotor resp. his superconducting

Winding in this case is also not tet longer be quietest ^¬.

For this reason, as is apparent from the figure, according to the invention, on the inside of the winding support 9, a special lining 25 made of a sufficiently porous Mate ^{¬ material} , preferably made of a sintered material. Its thickness D is generally between 0, 1 and 2 mm. Such a sintered material is selected for the embodiment. It is thus to be ensured that, even in imbalance due to capillary forces in the sintered material, the refrigerant k is uniformly distributed on the inner surface. shares, so that it is to ensure a uniform evaporation and thus cooling. The liner 25 should also made of a material with high thermal conductivity such. B. which consist of copper. It should be at least 100 W - In ^"1 - K ^{" 1} at a selected operating temperature of the superconducting material used. Preferably, the minimum value should be 400 W (m K) ^{^ 1} . For example, Cu sintered material has a value of thermal conductivity at a temperature of 30 K of about 3000 W rrT ¹ K ^-1 (see "Gmelin's Handbook of Inorganic Chemistry: Copper, Part A").

8.Auf.1955, page 957). The liner 25 has a good thermal contact with the winding body 9, the z. B. can be achieved by a shrink connection or by pressing.

A corresponding lining may also be present in the form of a layer which is achieved by coating the inner surface of the carrier body 9 with a material. In this case, a sufficiently porous structure must be ensured so that the required capillary forces can be effective.

The porosity of the lining 25 resp. its material should be at least 3% thereof, preferably at least 10% gen Betra ^¬. In operation with inclined axis rotation, the lining then causes a uniform distribution of the liquid

Refrigerant k, wherein the distribution of the refrigerant on the walls or surfaces of the created with the structures or cavities refrigerant paths is additionally supported by the centrifugal forces occurring.

The inventive liner is so uniform heat dissipation loss of the hollow cylinder over the entire inner surface both in the operating state and at Rota ^¬ tion can be in operation independently of the inclination of the motor axis A ensure. Of course, the refrigerant must k or. ^Enclosed parts or containers to be protected against heat. For their thermal insulation, therefore, a vacuum environment is expediently provided, wherein optionally in the corresponding vacuum spaces additionally insulating such. B. Super insulation or insulation foam can be provided. In the figure, the vacuum enclosed by the vacuum vessel 7 is designated by V. It also surrounds the lateral cavity 13 enclosing, up to the seal 21 extending pipe. The heat pipe 20 and the condenser 18 and the heat transfer body 17 enclosing vacuum is denoted by V ^Λ . Optionally, in the surrounding the rotor 5, enclosed by the outer housing 3 interior 27, a negative pressure can be generated.

Claims

claims

1. Machine Setup

with a rotor (5) rotatably mounted about a rotation axis (A) and surrounded by a stator, which has at least one rotor winding (10) whose superconductive conductors are coupled in a heat-conducting manner to a central, axially extending cylindrical rotor cavity (12), - with a located outside the rotor (5), ortsfes ^¬ th refrigeration unit (15) having a condenser (18) and

- With between the central rotor cavity (12) and the condenser space (18) of the refrigeration unit (15) extending, tubular line parts (22) wherein the rotor cavity (12), the tubular conduit parts (22) and the condenser (18) a closed ^{Form a} conduit system in which a refrigerant (k, k ') can circulate or utilize a thermosiphon effect, characterized in that the central rotor cavity (12) at least partially with a lining (25) made of a porous material of high thermal Conductivity is provided, for the refrigerant (k, k ') accessible, capillary ^¬ like structures or cavities forms.

2. Machine device according to claim 1, characterized in that the porous material is a sintered material.

3. Machine device according to claim 2, characterized by a copper sintered material.

4. Machine device according to one of the preceding claims, characterized by a pressed or einge ^¬ shrunken lining (25).

5. Machine device according to claim 1, characterized by a porous coating as a lining (25).

6. Machine device according to one of the preceding claims, characterized by a porosity of the lining (25) of at least 3%, preferably at least 10%.

7. Machine device according to one of the preceding claims, characterized in that the porous material has a thermal conductivity at the operating temperature of the superconducting conductor of at least 100 W / (m-K).

8. Machine device according to claim 7, characterized in that the value of the thermal conductivity of the porous material at the operating temperature of the superconductive conductor corresponds at least to that of the pure copper.

9. Machine device according to one of the preceding claims, characterized by superconductive conductors of the rotor ^¬ winding (10) with high-T _c -Supraleitermaterial.