Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03D—WIND MOTORS
  • F03D13/00—Assembly, mounting or commissioning of wind motors; Arrangements specially adapted for transporting wind motor components
  • F03D13/20—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D27/00—Foundations as substructures
  • E02D27/32—Foundations for special purposes
  • E02D27/42—Foundations for poles, masts or chimneys
  • E02D27/425—Foundations for poles, masts or chimneys specially adapted for wind motors masts
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
  • E04H12/00—Towers; Masts or poles; Chimney stacks; Water-towers; Methods of erecting such structures
  • E04H12/02—Structures made of specified materials
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
  • E04H12/00—Towers; Masts or poles; Chimney stacks; Water-towers; Methods of erecting such structures
  • E04H12/02—Structures made of specified materials
  • E04H12/08—Structures made of specified materials of metal
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
  • F05B2260/00—Function
  • F05B2260/96—Preventing, counteracting or reducing vibration or noise
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
  • F05B2280/00—Materials; Properties thereof
  • F05B2280/60—Properties or characteristics given to material by treatment or manufacturing
  • F05B2280/6003—Composites; e.g. fibre-reinforced

Definitions

• the present invention relates to a support member for a rotor and nacelle assembly, and a wind turbine.
• Modern wind turbines are usually designed with 3 rotor blades. Every time one of the rotor blade passes in front of the wind turbine tower there will be a slight change in loading on the blade due to a normally slightly reduced wind speed in front of the tower. In other words, the tower is interfering with the free wind. It is also normal, especially for large wind turbines with large rotors such as offshore wind turbines, that the wind speed is different at different positions of the rotor swept area for shorter or longer periods of time. This could for instance be caused by slow changing turbulence effects or surface boundary layer friction effects due to ocean waves, causing the wind speed to be reduced closer to the surface of the sea.
• each blade will typically experience a repeating change of wind loads for each revolution of the rotor. This will result in an impulse loading (that can be either a reduction in load or an increase in load) from the blade which is transferred via the rotor hub and further through the nacelle, tower and ultimately into the wind turbine foundation and results in fatigue in different elements of the wind turbine.
• an impulse loading that can be either a reduction in load or an increase in load
• this impulse load will “happen” 3 times for every revolution of the rotor.
• the frequency of this impulse load phenomena is therefore 3 times higher than the rotor frequency and often referred to as the 3 per revolution frequency, or just 3P frequency (given in hertz, or Hz).
• the wind turbine tower will have a natural frequency (also known as eigenfrequency) in bending. Fore-aft or side-to-side motion of the nacelle may cause the tower and as such, the wind turbine to sway (bend) back and forth with its natural frequency.
• This bending natural frequency will be decided by the tower stiffness and size, and influenced by the stiffness of the foundation to which the tower is mounted on, the mass of the tower and the effected parts of the foundation as well as the mass on top of the tower, i.e. the rotor and nacelle assembly (RNA). This frequency will be referred to as the wind turbine combined natural bending frequency.
• the tower will experience large structural vibrations which will cause extreme fatigue loading on both the tower and the foundation structure. This may also be the case if the combined natural bending frequency is close to the IP blade loading frequency, or any multiples of IP and 3P frequencies.
• the invention in a first aspect, relates to a support member for a rotor and nacelle assembly with walls comprising: a first portion comprising a first material; and a second portion comprising a second material, wherein the first and second portions are connected together; wherein the first portion is located above the second portion; and wherein the first portion has a bending stiffness that is higher than the bending stiffness of the second portion.
• first and second portions are connected together to form the support member.
• the first portion is formed at least of 50%, 60%, 70%, 80%, 90%, 95%, or 99% from the first material.
• the first material may have a modulus of elasticity that is at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200% or 500% higher than the modulus of elasticity of the second material
• the second portion may be a unitary component.
• the plurality of segments may comprise at least a segment with a first material and at least a segment with a second material, wherein the at least two materials have different moduli of elasticity.
• the plurality of segments of the second portion may be arranged in an axial direction of the support member.
• the rated wind speed is the wind speed at which the wind turbine is substantially reaching its full power, i.e it’s rated power, normally around 11-15 m/s.
• the torsional stiffness of the second portion may be determined such that at least a 1st combined natural torsion mode frequency of the support member is arranged between a three per revolution (3P) frequency and a six per revolution (6P) frequency of a wind turbine rotor at rated wind speed.
• the invention relates to a support member for a rotor and nacelle assembly with walls comprising: a first portion comprising a first material; and a second portion comprising a second material, where in the first and second portions are connected together to form the support member; wherein the first portion is located above the second portion; and wherein the first portion has an apparent modulus of elasticity that is higher than the modulus of elasticity of the second portion.
• Apparent modulus of elasticity or apparent bending stiffness will here have the meaning of the effective combined modulus of elasticity or bending stiffness when several materials are mixed or working together, such as for example in a glassfiber reinforced plastic.
• Fig. l is a front view of a first embodiment of the support member
• Fig. 3 is a perspective view of a wind turbine
• Fig. 4 is a front view of the third embodiment of the support member
• Fig. 5 is a cross section view of a detail of the third embodiment of the support member
• Fig. 6 is a front view of a fourth embodiment of the support member
• Fig. 11 shows the 1 st , 2 nd , 3 rd and 4 th bending mode frequencies for the combined system illustrated in fig. 10 related to the axes defined in fig. 10.
• Fig. 12 shows a wind turbine tower 1 st bending mode shape related to the axes defined in fig. 10.
• Fig. 13 shows a wind turbine tower 2 nd bending mode shape related to the axes defined in fig. 10.
• the 2 nd mode shape is similar to the first mode shape but differs in the azimuth direction.
• Fig. 14 shows a wind turbine tower 3 rd bending mode shape related to the axes defined in fig. 10.
• Fig. 15 shows a wind turbine tower 4 th bending mode shape related to the axes defined in fig. 10.
• each blade will typically experience a repeating change of wind loads for each revolution of the rotor. This will cause in an impulse loading (that can be either a reduction in load or an increase in load) from the blade which is transferred via the rotor hub and further through the nacelle, tower and ultimately into the wind turbine foundation and results in fatigue in different elements of the wind turbine.
• an impulse loading that can be either a reduction in load or an increase in load
• IP one per revolution
• this impulse load will “happen” 3 times for every revolution of the rotor.
• the frequency of this impulse load phenomena is therefore 3 times higher than the rotor frequency and often referred to as the 3 per revolution frequency, or just 3P frequency (given in hertz, or Hz), or independently of the number of blades, the blade tower passing frequency.
• a wind turbine can have any number of blades and for a 2 bladed wind turbine the corresponding blade tower passing frequency would be 2P frequency.
• a wind turbine rotor is normally designed to spin with a substantially constant operational angular speed (co rated), expressed in radians per second, when the rated wind speed is reached.
• co rated operational angular speed
• the rated wind speed is the wind speed at which the rated (maximum) output power is reached.
• the rotor angular speed can also be expressed as a frequency, namely the rotor frequency, in rotations per minute (RPM) or rotations per second (Hz).
• the 3P blade frequencies and the tower combined natural frequency always will have to be designed with a separation, typically 5-15% separation is regarded as sufficient.
• the tower frequencies are normally sought to be designed to be lower than the 3P blade frequency. I.e. the tower must then be “soft enough” to be vibrating slower than the 3P frequency. This type of design is often referred to as “soft-stiff’ design.
• the alternative is to make the tower stiffer and make sure that the tower vibrates with a higher frequency than the 3P frequency. This is referred to as a “stiff-stiff’ tower design.
• a stiff-stiff tower design has the disadvantage that the tower will then have to be made with thicker steel plates, or alternatively using materials with higher stiffness than steel such as carbon reinforced epoxy laminates, resulting in a considerably heavier tower, for example if only steel is used or a more costly tower, for example if carbon composite is used.
• the bending stiffness of a cross section of any kind is dependent on both the material’s modulus of elasticity (Young’s modulus) as well as the second moment of area of the cross section in question,
• the bending stiffness (BS) of a hollow circular pipe, i.e. of a typical wind turbine tower, can be written as;
• FIG. 10 illustrates a wind turbine comprising a tower with a second portion 3 of composite material mounted on a third portion 100 comprising a monopile.
• the 1 st , 2 nd , 3 rd and 4 th bending mode frequencies for the combined system in fig. 10 are illustrated in fig. 11, and related to the axes defined in fig. 10.
• the different bending mode shapes of the wind turbine in fig. 10 are illustrated in figs. 12 to 15.
• G is the shear modulus
• J is the mass moments of inertia of the point mass
• Js is the mass moment of inertia of the pipe
• L is the length of the pipe (or tower in a wind turbine installation).
• the shear modulus can be tailored in a composite structure by choosing the amount of 45 degrees layers versus the 0 degrees layers (axial direction) during the lay-up of the reinforcement fibers before laminating with epoxy or other resin types.
• a support member 5 of a wind turbine is illustrated.
• the support member 5 comprises a tower 6 and a foundation 4.
• the support member comprises a first portion 2 and a second portion 3.
• the wind turbine further comprises a rotor and nacelle assembly (see Fig. 3), placed on top of the first portion 2 of the support member 5.
• the first and second portions 2,3 are connected together, for example by bolts.
• the first portion 2 of the support member 5 is a hollow cylinder substantially made of steel.
• the second portion 3 of the support member 5 is a hollow cylinder substantially formed from a glass fiber reinforced epoxy which has a considerably lower bending stiffness than steel for the same strength.
• the foundation 4 is substantially made of steel.
• the support member and the wind turbine combined natural frequency can be tailored to suite any needs, especially to be lower than the blade frequency of the wind turbine.
• the length of the second portion will result in a softer tower with a lower combined natural bending frequency, even if the total height of the wind turbine tower and foundation is kept unchanged. I.e. as long as the second portion has a lower bending stiffness than the first portion above it, the length of the second portion can be used to reduce, and therefore tune, the combined natural bending frequency of the tower and foundation to a lower frequency.
• Fig.3 illustrate a wind turbine 1 comprising a floating foundation 4, a tower 6 and a rotor and nacelle assembly 7.
• a support member 5 of a wind turbine is illustrated.
• the support member 5 comprises a tower 6 and a foundation 4.
• the support member comprises a first portion 2 and a second portion 3.
• the wind turbine further comprises a rotor and nacelle assembly (see Fig. 3), placed on top of the first portion 2 of the support member 5.
• the first and second portions 2,3 are connected together, for example by bolts.
• the tower 6 has a pipe-in-pipe connection to the foundation 4.
• the second portion 3 of the support member 5 has a lower modulus of elasticity than the first portion 3 of the support member 5, by tuning the length of the first and second portions 2,3, the natural stiffness the support member and the wind turbine combined natural frequency can be tailored to suite any needs, especially to be lower than the blade frequency of the wind turbine
• the second portion 3 of the support member 5 has a lower modulus of elasticity than the first portion 3 of the support member 5, by tuning the length of the first and second portions 2,3, the natural stiffness the support member and the wind turbine combined natural frequency can be tailored to suite any needs, especially to be lower than the blade frequency of the wind turbine
• the first portion 2 of the support member 5 is a hollow cylinder substantially made of steel
• the second portion 3 of the support member 5 is a hollow cylinder substantially formed from a glass fiber reinforced epoxy which has a considerably lower bending stiffness than steel for the same strength.
• the first and second portions 2,3 are connected together to form the support member 5.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Architecture (AREA)
• Structural Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Civil Engineering (AREA)
• Sustainable Development (AREA)
• Wood Science & Technology (AREA)
• Materials Engineering (AREA)
• Sustainable Energy (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Mining & Mineral Resources (AREA)
• Paleontology (AREA)
• Wind Motors (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=88093144

Family Applications (1)

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Family Cites Families (9)

• 2022
  • 2022-09-13 NO NO20220974A patent/NO348641B1/en unknown
• 2023
  • 2023-09-13 EP EP23772171.7A patent/EP4587701A1/de active Pending
  • 2023-09-13 WO PCT/EP2023/075204 patent/WO2024056767A1/en not_active Ceased

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