DK201770222A1

DK201770222A1 - A Wind Turbine with Improved Heat Exchanger

Info

Publication number: DK201770222A1
Application number: DKPA201770222A
Authority: DK
Inventors: Jesper Nyvad; Eswararao Anjuri; Michael Lykke Heiredal
Original assignee: Vestas Wind Sys As
Priority date: 2017-03-28
Filing date: 2017-03-28
Publication date: 2018-05-07

Abstract

A wind turbine comprising: a nacelle; a hub supported by the nacelle and rotatable relative to the nacelle; a plurality of blades connected to the hub and extending from the hub; an external heat exchanger mounted on the nacelle and spaced from the hub in a downstream direction; wherein at least one turbulator is mounted on the hub and/or on the nacelle upstream of the heat exchanger.

Description

<¹θ> DANMARK

0°) DK 2017 70222 A1

PATENTANSØGNING

(12)

Patent- og

Varemærkestyrelsen (51) Int.CI.: F03D 80/60 (2016.01) (21) Ansøgningsnummer: PA 2017 70222 (22) Indleveringsdato: 2017-03-28 (24) Løbedag: 2017-03-28 (41) Aim. tilgængelig: 2018-04-30 (71) Ansøger: VESTAS WIND SYSTEMS A/S, Hedeager 42, 8200 Århus N, Danmark (72) Opfinder: Jesper Nyvad, Bredkær Grønnevej 7, 8250 Egå, Danmark

EswaraRao Anjuri, D.No. 7-44-110, Old Local Office Street, Bypass Road, Vishakhapatnam (Dt.), 531162

Tagarapuvalasa, Indien

Michael Lykke Heiredal, Skovparken 54, 8240 Risskov, Danmark (74) Fuldmægtig: Vestas Wind Systems A/S IPR Department, Hedeager 42, 8200 Århus N, Danmark (54) Benævnelse: A Wind Turbine with Improved Heat Exchanger (56) Fremdragne publikationer:

US 2006/0113804 A1

WO 2014/023835 A1

WO 2013/104777 A2

WO 2014/037080 A1

DE 102013201871 A1 (57) Sammendrag:

Fortsættes ...

DK 2017 70222 A1

A Wind Turbine with Improved Heat Exchanger

Technical Field

The present invention relates to a wind turbine with an external heat exchanger. In particular, flow turbulators are mounted upstream of the heat exchanger to improve the flow of air through the heat exchanger.

Background

Wind turbines are used to generate electrical energy from kinetic energy in the wind. A horizontal axis wind turbine comprises a nacelle which contains components such as a gearbox, generator, transformer and convertor. During operation of the wind turbine these components need to be kept within certain temperature levels to avoid overheating. To this end, it is known such as from WO2010/085960 that a heat exchanger can be provided on an exterior surface of the nacelle in order to cool equipment within the nacelle.

It is an object of this invention to improve the cooling performance of a heat exchanger on the nacelle of a wind turbine.

Summary of Invention

According to a first aspect of the present invention there is provided a wind turbine comprising: a nacelle; a hub supported by the nacelle and rotatable relative to the nacelle; a plurality of blades connected to the hub and extending from the hub; an external heat exchanger mounted on the nacelle and spaced from the hub in a downstream direction; wherein at least one turbulator is mounted on the hub and/or on the nacelle upstream of the heat exchanger.

The turbulator may be mounted on the hub between two blades extending from the hub. Preferably, a height of the turbulator is between 5% and 50% of a diameter of the hub. The height of the turbulator is measured in a direction substantially perpendicular to a rotational axis of the hub. The height of the turbulator may be between 5% and 60% of a diameter of the blade root where the blade attaches to the hub. Preferably, the turbulator comprises a vane which extends substantially perpendicular to the surface on which it is mounted.

DK 2017 70222 A1

Preferably, the heat exchanger is mounted at a downstream end of the nacelle. Preferably, the heat exchanger is mounted on a roof of the nacelle. The heat exchanger may extend substantially perpendicular to the surface of the nacelle on which it is mounted.

Preferably, the turbulator comprises a pair of vanes. Preferably, the turbulator comprises a vortex generator.

According to a second aspect of the present invention there is provided a method of cooling components in a wind turbine nacelle, the wind turbine comprising: a nacelle, a hub supported by the nacelle and rotatable relative to the nacelle and a plurality of blades connected to the hub and extending from the hub; the method comprising: providing an external heat exchanger on the nacelle and spaced from the hub in a downstream direction, the heat exchanger comprising a cooling circuit in fluid communication with the components to be cooled; providing at least one flow turbulator mounted on the hub and/or on the nacelle upstream of the heat exchanger.

Preferably, the method further comprises operating the wind turbine such that the turbulator mixes airflow downstream of the turbulator.

Brief description of the drawings

In order that the present invention may be more readily understood, examples of the invention will now be described, by way of example only, and with reference to the following Figures, in which:

Figure 1 is a perspective view of a wind turbine;

Figure 2 is a cross section view of a nacelle and a hub;

Figure 3 is an enlarged view of Figure 2;

Figure 4 is a cross section view of a nacelle and a hub schematically showing airflow;

Figure 5 is a front perspective view of hub and a nacelle according to an example of the present invention;

Figure 6 is a plan view of the hub and nacelle of Figure 5;

Figure 7 is a plan view of a hub and nacelle according to an example of the present invention;

Figures 8a to 8d are example of turbulators.

DK 2017 70222 A1

Detailed description of the invention

Figure 1 shows a horizontal axis wind turbine 10. The wind turbine 10 comprises a tower 12 supporting a nacelle 14 to which a rotor 16 is mounted. The rotor 16 comprises a plurality of wind turbine blades 18 that extend radially from a central hub 20. In this example, the rotor 16 comprises three blades.

The wind turbine 10 is a horizontal axis wind turbine. When wind exceeds a minimum level the rotor 16 will rotate in a substantially perpendicular direction to the wind direction. The wind turbine blades 18 are configured to interact with the passing air flow to produce lift that causes the rotor 16 to spin generally within a plane defined by the blades 18. The wind turbine is an upwind turbine, that is the rotor 16 is in front (i.e. upwind) of the tower 12 and the nacelle 14 so that the rotor faces into the oncoming wind.

The term “upstream” and “downstream” are used in this disclosure in a conventional sense, i.e. upstream is the direction in which the wind is coming from. The terms “upstream” and “downstream” still mean the same when referring to positions of components on the nacelle even when the wind turbine is non-operational, i.e. upstream is toward the front of the turbine and downstream is toward the rear of the turbine.

Figure 2 shows a cross section through the nacelle 14. The nacelle 14 comprises an outer housing defined, at least in part, by a nacelle roof 26, a rear wall 28, and a pair of sidewalls 30 (only one sidewall 30 is visible in Figure 1). The rear wall 28 of the nacelle 14 faces a direction opposite from the hub 20 and wind turbine blades 18.

Generally the blades 18 are mounted to a metallic hub and the metallic hub is surrounded by a lightweight fibreglass aerodynamic spinner which is exposed to the oncoming wind. For simplicity, in this disclosure the term “hub” encompasses the spinner.

In this example the nacelle comprises a gearbox 24 and a generator 25 which generate significant amounts of heat in use. When these components are heated, the overall efficiency of power generation of the wind turbine may be decreased. Therefore, the components in the nacelle are cooled to ensure that the heat does not adversely affect power generation and/or damage the components.

The wind turbine comprises a cooling device configured to remove the heat generated during operation of the wind turbine. In this example the cooling device is a heat exchanger

DK 2017 70222 A1 provided on the outside of the nacelle 14. Air flows through the heat exchanger 22 which cools a fluid flowing through panels of the heat exchanger which is used to cool the heat generating components in the nacelle. Preferably, the heat exchanger 22 operates as a tree-flow cooling device wherein wind is encouraged to pass over the panels of the heat exchanger to cool the fluid flowing in the panels without the assistance of fans or other actuators requiring power from the generator 25.

In this example, the heat exchanger 22 projects upwardly from the nacelle roof 26. However, in other examples, the heat exchanger 22 may be arranged on a sidewall 30 of the nacelle or even on the bottom surface of the nacelle. In still further examples, a heat exchanger may be arranged on the nacelle roof 26 and further heat exchangers arranged on the nacelle sidewalls 30. What is important is that the heat exchanger is positioned on an exterior of the nacelle and air flows through the heat exchanger to cool the fluid within the heat exchanger.

The heat exchanger is disposed generally perpendicular to the nacelle surface on which it is mounted in order to maximize a flow area in the path of wind flowing past the nacelle 14. However, in other examples the heat exchanger 22 may be disposed at a non-perpendicular angle to the nacelle surface on which it is mounted. The heat exchanger is provided toward the rear of the nacelle, such as in the rear 15% of the nacelle length.

For the heat exchanger 22 to operate effectively a certain mass flow of air is required to pass through the heat exchanger, to cool the fluid in the heat exchanger. An increased air mass flow through the heat exchanger 22 will increase the cooling effect of the heat exchanger.

Referring to Figure 2 in particular, it can be seen that the air that passes through the heat exchanger 22 has travelled past the rotating hub 20 and the rotating blades 18. The effect of the air flowing past the hub and the blades means that the air flow downstream of the rotor 16 is turbulent and will separate from the roof 26 of the nacelle. In particular, the hub 20 is a bluff body and the blades 18 where they attach to the hub 20 have a root section 18a which has cylindrical (or elliptical) cross section so that airflow behind the rotor 16 is highly separated and three dimensional in nature.

Figure 3 is a close up view of the intersection between the hub 20 and the nacelle 14, in this example there is a step 30 down from the hub to the nacelle. The step 30 also contributes to the turbulent flow over the roof 26 of the nacelle 14.

DK 2017 70222 A1

Figure 4 shows schematically that the airflow over the roof 26 of the nacelle 14 has separated as shown by the line 32 and that there are recirculation regions indicated by the curved arrows. It will be appreciated that the flow is in fact three dimensional and so Figure 4 is highly schematic. The end result is that the boundary layer over the nacelle roof 26 has separated from the nacelle surface and there are recirculation zones with high turbulence over the nacelle 14. This reduces the mass flow of air passing through the heat exchanger 22. Hence, the efficiency of the heat exchanger 22 is reduced.

Figures 5 and 6 show how the wind turbine is provided with turbulators in order to increase the mass flow of air passing through the heat exchanger. Figure 5 shows a partial perspective view of the wind turbine from the front and Figure 6 shows a partial plan view of the wind turbine.

In the example shown in Figures 5 and 6 the hub 20 is equipped with a turbulators 40 which are provided between the blades. The turbulators 40 comprise vanes 40a, 40b arranged in a pair. However, as will be discussed below, other arrangements and positions of turbulators are possible.

The wind turbine of Figures 5 and 6 is a three bladed turbine, hence three turbulators 40 are provided spaced at angles of 120 degrees about the circumference of the hub 20. The turbulators 40 project outwards from the hub 20, that is in a direction perpendicular to the rotational axis of the hub. The function of the turbulators is to improve the flow downstream of the hub 20 so that the mass flow of air through the heat exchanger 22 is increased.

The turbulators 40 are passive flow devices and they minimise the three dimensional flow behaviour downstream of the hub 20 and increase the air flow passing through the heat exchanger 22, thereby increasing the efficiency of the heat exchanger. The turbulators 40 act as flow mixers by transferring momentum from the free stream flow above the hub 20 to the boundary layer over the hub, thereby energising the boundary layer over the hub and downstream of the hub over the nacelle 14. By energising the boundary layer over the hub 20 and the nacelle 14, the flow will be more streamlined and in effect more uniform. In particular, the three dimensional nature of the flow will be reduced and the size and intensity of any recirculation zones will be reduced. This means that a higher mass flow of air passes through the heat exchanger 22 improving the performance of the heat exchanger.

The turbulators 40 are designed to mix boundary layer flow and the free stream flow above the boundary layer. To this end, the turbulators generate vortices from their vanes to achieve

DK 2017 70222 A1 this mixing and they thus act as vortex generators which are well known aerodynamic devices. As is well known in the field of aerodynamics, the boundary layer is the portion of the flow above the hub/nacelle where viscosity and friction forces are significant. The free stream flow is above the boundary layer where viscous forces are insignificant. Due to the rotation of the hub and the blades the free stream flow may not be a laminar flow, instead it may be a turbulent flow. However, even if the free stream flow is turbulent it can still be mixed with the boundary layer flow to prevent the boundary layer from detaching from the nacelle surface.

A particular advantage of the turbulators 40 is that they are passive devices, i.e. they do not require any external power. Therefore, the performance of an existing heat exchanger can be improved without having to incorporate any powered pumps or fans or the like.

It has been found by simulations on a 3MW turbine that the provision of turbulators 40 on the hub 20 can increase the average mass flow of air through the heat exchanger 22 by around 25%. This provides a number of advantages which include:

• Compared to a conventional wind turbine, the wind turbine of the invention can be operated for longer periods of time without the need for power derating due to overheating components. This reduces the cost of energy due to continuous operation of wind turbine at high temperatures.

• The heat exchanger can be smaller compared to a conventional turbine, thereby reducing cost and weight.

• An existing turbine can be uprated (for example the nominal power rating is increased from 3.0MW to 3.3MW) without having to increase the size of the heat exchanger to account for the extra heat generated at the higher power rating. The turbulators can be retrofitted to an existing wind turbine which provides a quick and straightforward way of increasing the cooling efficiency of the heat exchanger.

Figure 7 shows an example where two turbulators 40 are provided on the nacelle 14, in particular on the roof 26 of the nacelle. The turbulators 40 are mounted on the nacelle downstream from the hub 20 and upstream from the heat exchanger 22 (not shown in Figure 7), in other words the turbulators are provided between the hub and the heat exchanger. When mounted on the nacelle the turbulator operate in the same way as when mounted on the hub, that is they mix air from the free stream flow above the nacelle with the boundary layer on the nacelle to energise the flow to reduce three dimensional behaviour in the flow

DK 2017 70222 A1 field. As noted above, the will increase the mass flow of air passing through the heat exchanger.

Preferably, the turbulators will be mounted as far forward on the nacelle as possible (that is immediately downstream of the hub) so that they have the greatest influence on the flow. In Figure 7 two turbulators are shown, each comprising a pair of fins. However, other numbers of turbulators may be provided on the nacelle, such as one, or a plurality of turbulators such as three, or more.

It may be beneficial to mount the turbulators on the nacelle if there is a lack of available space on the hub. On the other hand, when the turbulators are mounted on the hub they will rotate with the rotor which will increase their effectiveness at mixing free stream flow with the boundary layer flow. In an example not shown in the Figures, the turbulators may be provided on both the nacelle and the hub.

Figures 8a to 8d show different arrangements of turbulators which can be used on the hub and/or on the nacelle. In Figure 8a, two vanes 40a and 40b form a counter-rotating vortex generator arrangement. In Figure 8b, two vanes 40a and 40b form a co-rotating vortex generator arrangement. In Figure 8c, the turbulator 40 is formed from a single vane angled with respect to the rotational axis of the rotor. Figure 8d shows an example where the vanes are formed as triangles which increase in height in a downstream direction. In addition, the vanes of any of Figures 8a to 8d may be formed in the shape of a triangle or trapezoidal.

An important parameter of the turbulators 40 is the height of the vanes. The height of the vanes (see “h” in Figure 8a) should at least match or be greater than the thickness of the boundary layer over the hub. In an example the height of the turbulator is between 5% and 50% of the diameter of the hub. The height of the turbulator may also be related to the diameter of the blade at its root, and the height may between 5% and 60% of the blade root diameter, A length “I” of the vanes may be between 1 to 5 times the of the height of the vanes.

Preferably, the turbulators are arranged at an angle to the rotational axis of the rotor. This angle may be between 5 degrees and 30 degrees. The turbulator may be divergent in the downstream direction as shown, or they may be convergent in the downstream direct (not shown).

DK 2017 70222 A1

Figures 5 and 6 showed a single pair of vanes 40a, 40b mounted on the hub 20 between each blade. However, other configurations are possible such as a single vane (i.e. Figure 8c) or a plurality of turbulators each comprising two vanes, such as two pairs or more between each blade. Also, as shown in Figures 5 and 6 the turbulators are mounted in line with the blades. However, depending on the geometry of the hub 20 and the space available they could be mounted upstream of the blades or downstream of the blades.

The turbulators 40 may be formed from any suitable material which can maintain its shape without being deformed or damaged by the wind. For example, the turbulators may be formed from aluminium or for reduced weight they may be formed from a composite, such as glass fibre reinforced plastic. The turbulators 40 may be mounted on the hub or the nacelle using conventional methods, such as mechanical fixings (e.g. bolts, rivets) or by adhesive bonding. If the outer surface of the hub or nacelle is formed from fibre glass the turbulators could be integrally moulded with the hub or nacelle.

As shown in the Figures, the heat exchanger 22 is mounted on the nacelle roof 26. However, as noted previously, the heat exchanger 22 could be mounted on the sidewalls or even the underside of the nacelle. In these cases, if the turbulators 40 are provided on the nacelle, they will be arranged on the nacelle sidewall or the underside of the nacelle.

DK 2017 70222 A1

Claims

1. A wind turbine comprising: a nacelle;

a hub supported by the nacelle and rotatable relative to the nacelle;

a plurality of blades connected to the hub and extending from the hub;

an external heat exchanger mounted on the nacelle and spaced from the hub in a downstream direction;

wherein at least one turbulator is mounted on the hub and/or on the nacelle upstream of the heat exchanger.

2. I I Claims Nos.:

because they relate to parts of the patent application that do not comply with the prescribed requirements to such an extent that no meaningful search can be carried out, specifically:

2/5

DK 2017 70222 A1

I $5 i

<<

§ $$ i

3/5

DK 2017 70222 A1 «a?aa^w>^s\\\vv\x\\>»»>X»V+>\>>>N.s\vsw-w « DK 2017 70222 A1

DK 2017 70222 A1

5/5

IMmsH Fatent aw Trare^ank Öma

SEARCH REPORT - PATENT Application No. PA 2017 70222 1. 1 1 Certain claims were found unsearchable (See Box No. I). 2. 1 1 Unity of invention is lacking prior to search (See Box No. II). A. CLASSIFICATION OF SUBJECT MATTER F 03 D 80/60 (2016.01) According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED PCT-minimum documentation searched (classification system followed by classification symbols) IPC/CPC: F03D. CPC: Y02E Documentation searched other than PCT-minimum documentation DK, NO, SE, FI: IPC-classes as above. Electronic database consulted during the search (name of database and, where practicable, search terms used) EPODOC, WPI, TXTE C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant for claim No. X US 2006/0113804 Al (COSTIN) 2006.06.01, paragraphs 0019 - 0025 and the 1-5, 8,9, 11, 12 figures. X WO 2014/023835 Al (YOUWINENERGY GMBH) 2014.02.13, paragraphs 1,2,5-9, 11, 12 0037 - 0047 and the figures. X WO 2013/104777 A2 (YOUWINENERGY) 2013.07.18, paragraphs 0047 - 0051 1,2,5-9, 11, 12 and the figures. A WO 2014/037080 Al (HYDAC COOLING GMBH) 2014.03.13 1-12 A DE 102013201871 Al (SENVION SE) 2014.08.21 10 1 1 Further documents are listed in the continuation of Box C. * Special categories of cited documents: P Document published prior to the filing date but later than the A Document defining the general state of the art which is not priority date claimed. considered to be of particular relevance. T Document not in conflict with the application but cited to D Document cited in the application. understand the principle or theory underlying the invention. E Earlier application or patent but published on or after the filing date. ^X Document of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive L Document which may throw doubt on priority claim(s) or which is _{when ώ document is taken alone}. cited to establish the publication date of another citation or other special reason (as specified⁵» Y Document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is ”°” Document referring to an oral disclosure, use, exhibition or other combined with one or more other such documents, such ^means' combination being obvious to a person skilled in the art. Document member of the same patent family. Danish Patent and Trademark Office Date of completion of the search report Helgeshøj Allé 81 29 August 2017 DK-2630 Taastrap Denmark Authorized officer Dmitri Burdykin Telephone No.+45 4350 8000 Facsimile No. +45 4350 8001 ^{1 ele}P^{hone No}· +^{45 4350 8311}

Search Report

SEARCH REPORT - PATENT Application No. PA 2017 70222 C (Continuation). DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant for claim No.

Search Report

SEARCH REPORT - PATENT Application No. PA 2017 70222 Box No. I Observations where certain claims were found unsearchable

This search report has not been established in respect of certain claims for the following reasons: !·□ Claims Nos.:

because they relate io subject matter not required to be searched, namely:

2. A wind turbine according to claim 1, wherein the turbulator is mounted on the hub between two blades extending from the hub.

3. A wind turbine according to claim 1 or claim 2, wherein a height of the turbulator is between 5% and 50% of a diameter of the hub.

4. A wind turbine according to anyone of the preceding claims, wherein the height of the turbulator is between 5% and 60% of a diameter of the blade root where the blade attaches to the hub.

5. A wind turbine according to any one of the preceding claims, wherein the turbulator comprises a vane which extends substantially perpendicular to the surface on which it is mounted.

6. A wind turbine according to any one of the preceding claims, wherein the heat exchanger is mounted at a downstream end of the nacelle.

7. A wind turbine according to any one of the preceding claims, wherein the heat exchanger is mounted on a roof of the nacelle.

8. A wind turbine according to any one of the preceding claims, wherein the heat exchanger extends substantially perpendicular to the surface of the nacelle on which it is mounted.

9. A wind turbine according to any one of the preceding claims, wherein the turbulator comprises a pair of vanes.

DK 2017 70222 A1

10. A wind turbine according to any one of the preceding claims, wherein the turbulator comprises a vortex generator.

5 11. A method of cooling components in a wind turbine nacelle, the wind turbine comprising: a nacelle, a hub supported by the nacelle and rotatable relative to the nacelle and a plurality of blades connected to the hub and extending from the hub; the method comprising:

providing an external heat exchanger on the nacelle and spaced from the hub in a

10 downstream direction, the heat exchanger comprising a cooling circuit in fluid communication with the components to be cooled;

providing at least one flow turbulator mounted on the hub and/or on the nacelle upstream of the heat exchanger.

15 12. A method according to claim 11, further comprising operating the wind turbine such that the turbulator mixes airflow downstream of the turbulator.

DK 2017 70222 A1

3. I I Claims Nos.: because of other matters.

Box No. II Observations where unity of invention is lacking prior to the search

The Danish Patent and Trademark Office found multiple inventions in this patent application, as follows:

Search Report

SEARCH REPORT - PATENT Application No. PA 2017 70222 SUPPLEMENTAL BOX Continuation of Box [.]

Search Report