WO2012038243A2

WO2012038243A2 - Air-cooled generator

Info

Publication number: WO2012038243A2
Application number: PCT/EP2011/065323
Authority: WO
Inventors: Stefan Baumeister; Simon Andreas Frutiger; Benjamin Jordan
Original assignee: Alstom Hydro France
Priority date: 2010-09-21
Filing date: 2011-09-05
Publication date: 2012-03-29
Also published as: CN103109442A; WO2012038243A3; CA2811534A1; CN103109442B; EP2619882A2; CH703820A1; US20130217317A1

Abstract

The invention relates to an air-cooled generator, through which cooling air flows in order to dissipate lost heat, wherein the cooling air flows across interfaces (23) acting as cooling surfaces and in the process takes up the heat from said interfaces (23). With minimal cooling air usage, the heat transfer is maximized by providing the interfaces (23) with spatially distributed local elevations (24) which enlarge the cooling surface and the heat transmission coefficient. In particular, local elevations in the form of pyramid-shaped or truncated pyramid-shaped bodies (24, 26, 29) are preferred.

Description

AIR-COOLED GENERATOR

TECHNICAL AREA

The present invention relates to the field of rotary electric machines. It relates to an air-cooled generator according to the preamble of claim 1.

STATE OF THE ART

In air-cooled generators all losses incurred in the form of heat on the cooling medium, such as cooling air, must be dissipated. Here, different surfaces of the generator serve to transfer the losses by convection to the cooling medium (the cooling air). An adaptation of the surface geometry fundamentally improves this transition. The aim of the cooling is to prevent the temperatures of the generator elements during operation from exceeding an agreed temperature. If the output of the heat loss of the generator can be improved, either lower temperatures of the generator parts are to be expected, or, conversely, equal temperatures of the generator parts can be achieved with a lower volume flow of the cooling air, resulting in lower ventilation losses.

For certain regions, the surfaces have already been optimized, for example by cooling fins, which increase the active surface area. In this type of surface adaptation, the direction of the flow of the cooling medium is of great importance. Due to the design but not all cooling surfaces of

Generators are optimally flown. In a generator, as disclosed, for example, in document EP 740 402 A1, such cooling surfaces are typically located in the region of the pole coils of the rotor. Fig. 1 shows in a

Detail in perspective view of several poles 1 1 of such

Generator 10, which are fastened by means of corresponding Polklauen 13 on the rotor, not shown. Each of the poles 1 1 has a pole coil 12. The individual poles 1 1 are separated in the circumferential direction by pole gaps 14 from each other. The basis of the temperature calculation in air-cooled machines is the following physical formula:

Q = A AT

where:

Q = heat flow [W]

α = heat transfer coefficient [W / m ² K]

A = cooling surface [m ² ]

ΔΤ = temperature difference [K]

As a rule, the losses or heat losses Q which have to be dissipated are known. ΔΤ represents the target value of the design

Temperature difference between the cooling medium and the cooling surface of the body to be cooled and the temperature of the cooling medium is fixed, can be inferred to the temperature of the body to be cooled. It remains the heat transfer coefficient and the cooling surface, which can be influenced. The simplest cooling geometry is a smooth surface. Although this geometry is independent of the direction of flow, it has the minimum possible

Surface. In addition, the losses that can be dissipated per unit area, only moderately high. If one deviates from the conventional geometries for improving the cooling, such as the cooling fins in various designs (see FIGS. 4 and 5), the problem arises that the design does not always make the flow "ideal" for the geometry and thus 4 shows a perspective view of a detail of an interface 17, which has parallel elongated ribs 18 which are separated from one another by recessed interspaces 19. The cross-sectional contour is rectangular meander-shaped 3 shows a perspective view of a section of an interface 20, which has parallel elongated ribs 21 which are separated from one another by recessed interspaces 22. The cross-sectional contour is sawtooth-shaped If these interfaces 1 7 and 20 are used as cooling surfaces, the ribs 18 and 21 act as cooling fins, their effect depends strongly on the flow direction of the overflowing

Cooling medium off.

FIGS. 6 and 7 make it clear that, in the case of a faulty flow, the

Cooling ribs 18 and 21 (flow direction transverse to the cooling fins) can come to areas, namely the recessed spaces 19 and 22, in which the flow rates are very low or recirculations or

Dead water, because the majority of the flow over the spaces between slides away. In both cases, this means that there is hardly one left

Mass transfer of the cooling medium in these regions comes. In the case of Although recirculation retains some heat transfer coefficient, both cases lead to a sharp increase in the temperature of the cooling medium. Looking at the formula given above for the calculation of the

Heat transfer, so a small temperature difference ΔΤ inevitably leads to a sharp decrease in heat dissipated. Conversely, this means that the surface temperature must increase in order to dissipate the same amount of heat.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to provide an air-cooled generator which avoids the disadvantages described and in particular thereby

characterized in that with a minimum volume flow of cooling air maximum heat dissipation from the inside of the generator is achieved.

The object is solved by the entirety of the features of claim 1. The inventive generator, which is flowed through to dissipate heat loss of cooling air, wherein the cooling air sweeps over surfaces acting as cooling surfaces and thereby absorbs heat from these interfaces, characterized in that the interfaces arranged distributed with the cooling surface increasing local elevations are provided.

An embodiment of the invention is characterized in that the local elevations to form a pattern uniformly over the

Cooling surface are distributed.

In particular, the local surveys can take the form of simple

have geometric bodies.

According to a development, the local surveys in the form of cones or truncated cones. Another development is characterized in that the local

Elevations have the shape of cylinders or cuboids. According to a particularly preferred development, the local

The form of pyramids or truncated pyramids.

A surface equipped with pyramidal or pyramidal elevations not only promotes the turbulence of the cooling medium passing past, but also prevents or reduces the formation of a thermal boundary layer in the wall region by deflecting flowing cooling medium away from the surface to be cooled, thereby mixing promotes the coolant perpendicular to the flow direction. Another embodiment of the invention is characterized in that the generator comprises a rotor having a plurality of poles, which are separated from each other by pole gaps and which are each provided with a pole coil, and that provided with the local elevations cooling surfaces in the

Pole back region are arranged.

A further embodiment of the invention is characterized in that the generator comprises a rotor with a plurality of poles, which are separated from each other by pole gaps and are each provided with a pole coil, and that provided with the local elevations cooling surfaces in the

Ventilation of the pole coils are arranged.

BRIEF EXPLANATION OF THE FIGURES The invention will be described below with reference to embodiments in the

Connection with the drawing will be explained in more detail. Show it a perspective view of a section of a generator rotor having a plurality of poles, which are cooled by means of flowing cooling air; the pole gaps of the rotor, which are important for the cooling, according to FIG. 1; the important for the cooling entries for the ventilation of the pole coils; in perspective a section of a

Boundary surface with parallel cooling fins and meander-shaped rectangular cross-sectional contour; in perspective a section of a

Interface with parallel fins and sawtooth cross-sectional contour; the effect of Fehlanströmung an interface according to FIG. 4; the effect of Fehlanströmung an interface according to FIG. 5; a perspective view of the section of a suitable as a cooling surface interface with local elevations in the form of pyramids with a rectangular base according to an embodiment of the invention; in different sub-figures other types of local

Elevations in the form of simple geometric bodies according to other embodiments of the invention.

WAYS FOR CARRYING OUT THE INVENTION In the Kühloberflachengeometrie, which is the basis of the present invention, the following aspects are considered: On the one hand is as high as possible

Heat transfer coefficient achieved in a constant mass transfer near the surface to be cooled. On the other hand, an enlargement of the

Achieved cooling surface. In addition to these three positive points, the

Cooling effect should be as independent as possible of the flow conditions.

All this is achieved by the cooling surface is provided with local elevations, which are distributed over the surface so that largely independent of the flow direction of the cooling air flowing above a uniformly high heat transfer between the cooling surface and cooling air.

In Fig. 8 is a detail of a as a perspective view

Cooling surface suitable interface with local elevations in the form of pyramids 24 with a rectangular (for example, square) base and

corresponding spaces according to an embodiment of the

Invention reproduced. Size (base and height) and shape of the individual pyramids 24 as well as the number and density or positioning of the individual pyramids 24 to each other (location of the interstices) can be adjusted within wide limits the cooling needs and space in the area to be cooled in order to optimize Result. However, the pyramid shape is by no means limited to the use of pyramids or stumps with a quadrangular layout. Of course, pyramidal bodies can be used with triangular or polygonal base. Also, it does not necessarily have to be a regular pyramid, that is, not all the side edges of the

Pyramid or the pyramid stump be the same length.

By reshaping the surface geometry in the mentioned manner, areas with very low flow velocities are bypassed. Since, as shown in Fig. 8, the individual pyramids 24 by their regular, with

Spaces provided arrangement are almost completely flowed around, This leads to increased turbulence in the region of the interface or cooling surface 23. On the one hand results in a good heat transfer coefficient α and on the other hand, a markedly improved mixing of the cooling medium at the surface. Sites where the cooling medium could heat up excessively, are thus avoided. By the increased

Heat transfer coefficient α and the increased cooling surface also increases the dissipated heat loss Q at the same cooling surface temperature.

Conversely, the surface temperature increases at the same time

losses to be deducted.

A significant advantage of the pyramid structure is also due to a further effect. In contrast to other locally shaped elevations, a pyramid structure, as exemplified in FIG. 8, not only increases the available heat transfer area and the turbulence of the flowing cooling medium, but also promotes the same

Mass transfer between near - wall and far - wall layers of the

Cooling medium, so it contributes to a mixing of the same perpendicular to the flow direction. By the cooling medium flows against the side surfaces of the pyramidal body (24, 26, 29), it is deflected away from the wall to be cooled. It forms one of the surface to be cooled

directed flow component out, in the wake of fresh cool medium is brought to the wall. In this way, the

Training a thermal boundary layer obstructed or avoided. Unlike in the case of laterally flowed-on ribs (see FIG. 7), no dead water forms in the pyramidal bodies according to the invention.

To be able to exploit this advantage, according to an advantageous

Embodiment three- or quadrangular pyramidal projections preferred and arranged the same so that a side surface perpendicular to

Main flow direction is aligned.

The previous statements related to local elevations in the form of a pyramid 24. However, it is quite possible within the scope of the invention, to use other geometries. 9, for example, on cones 25 (FIG. 9a) or truncated cones are thought of. Pyramids 26 with a triangular base and truncated pyramid stumps 29 are shown in FIGS. 9b and 9e.

On the other hand, cubes, cylinders 27 (FIG. 9c), cubes 28 (FIG. 9d) and other prisms could advantageously be used as basic elements for the

Kühloberflächengeometrie be considered, in which case, however, the previously explained additional benefits of a pyramidal surface structure, namely the reduced formation of a thermal boundary layer, not occur.

2, in particular the pole gap regions 15 of the generator 10, for example at one or more pole coil or pole body surfaces, and according to FIG. 3 the rear ventilation of the pole coils 12.

LIST OF REFERENCE NUMBERS

10 generator (air-cooled)

1 1 pole

12 pole coil

13 pole claw

14 pole gap

15 pole-back region

16 ventilation entry

17,20,23 interface (cooling surface)

18:21 rib

19.22 interval (recessed)

24 pyramid (with rectangular base)

25 cones

26 pyramid (with triangular base)

27 cylinders 28 cuboid

29 truncated pyramid

Claims

1 . Air-cooled generator (10), which is flowed through to dissipate heat loss of cooling air, wherein the cooling air over cooling surfaces acting as cooling surfaces (23) and thereby absorbs heat from these interfaces (23), characterized in that the interfaces (23) distributed with arranged, the Kühloberfläche enlarging local elevations (24-29) are provided.

2. Generator according to claim 1, characterized in that the local elevations (24-29) are distributed uniformly over the cooling surface (23) to form a pattern.

3. Generator according to claim 1 or 2, characterized in that the local elevations have the form of simple geometric bodies.

4. Generator according to claim 3, characterized in that the local elevations in the form of pyramids (24, 26) or truncated pyramids (29).

5. Generator according to claim 4, characterized in that the

Pyramids (24, 26) or truncated pyramids (29) have a quadrangular base.

6. Generator according to claim 5, characterized in that the

Pyramids (24, 26) or truncated pyramids (29) have a rectangular base.

7. Generator according to claim 4, characterized in that the

Pyramids (24, 26) or truncated pyramids (29) have a triangular base, in particular formed as a tetrahedron.

8. Generator according to claim 4, characterized in that a flowed-side surface of the pyramid (24, 26) or of the truncated pyramid (29) is aligned transversely to the main flow direction of the cooling medium.

9. Generator according to claim 6 and 8, characterized in that a longer side edge of the pyramid (24, 26) or of the truncated pyramid (29) is arranged transversely to the main flow direction of the cooling medium.

10. Generator according to claim 3, characterized in that the local

Elevations in the form of cones (25) or truncated cones.

1 1. Generator according to claim 3, characterized in that the local elevations in the form of cylinders (27) or cuboids (28).

12. Generator according to any one of claims 1 -1 1, characterized in that the generator (10) comprises a rotor having a plurality of poles (1 1) which are separated from each other by pole gaps (14) and each provided with a pole coil (12) and that the cooling surfaces provided with the local elevations (24 - 29) are arranged in the pole gap region (15), for example on one or more pole coil or pole body surfaces.

13. Generator according to any one of claims 1 -1 1, characterized in that the generator (10) comprises a rotor having a plurality of poles (1 1) which are separated from each other by pole gaps (14) and each provided with a pole coil (12) are, and that provided with the local elevations (24 -29) cooling surfaces in the region of the rear ventilation (16) of the pole coils (12) are arranged.