WO2021259432A1 - Procédé de conception de composants structuraux de turbine éolienne coulés par modélisation virtuelle et son procédé de fabrication - Google Patents

Procédé de conception de composants structuraux de turbine éolienne coulés par modélisation virtuelle et son procédé de fabrication Download PDF

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Publication number
WO2021259432A1
WO2021259432A1 PCT/DK2021/050189 DK2021050189W WO2021259432A1 WO 2021259432 A1 WO2021259432 A1 WO 2021259432A1 DK 2021050189 W DK2021050189 W DK 2021050189W WO 2021259432 A1 WO2021259432 A1 WO 2021259432A1
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WIPO (PCT)
Prior art keywords
casted
virtual
wind turbine
turbine component
data
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PCT/DK2021/050189
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English (en)
Inventor
Peter Jonatan Bernhardt JENSEN
David ÖSTERBERG
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Vestas Wind Systems A/S
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Publication of WO2021259432A1 publication Critical patent/WO2021259432A1/fr

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • 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
    • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
    • 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
    • F05B2260/84—Modelling or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/06—Wind turbines or wind farms
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/08—Fluids
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This invention relates generally to wind turbines, and more particularly to an improved method of designing and manufacturing casted wind turbine structural components, such as the main bearing housing, based on iterative computer simulation models for strength and stress distributions.
  • Wind turbine generators are used to produce electrical energy using a renewable resource and without combusting a fossil fuel.
  • a wind turbine generator converts kinetic energy from the wind into electrical energy, and includes a tower, a nacelle mounted atop the tower, a rotor hub rotatably supported by the nacelle, and a plurality of rotor blades attached to the hub.
  • the hub is coupled to a generator housed inside the nacelle by a drive train that includes a rotor shaft coupled to the rotor and extending into the nacelle, a main bearing housing for rotatably supporting the main rotor shaft, and a gear box for stepping up the rotational speed of the input shaft to the generator. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator.
  • wind power has become a more attractive alternative energy source and the number of wind turbines, wind farms, etc. has significantly increased, both on land and off-shore. Additionally, the size of wind turbines has also significantly increased, with modern wind turbine blades extending between 50 to 80 meters in length, and the length of wind turbine blades is expected to further increase in the future. Due to their large and ever-increasing size, the force and moment loads on the wind turbine are tremendous, and wind turbine components must be designed to withstand the expected loads during operation of the wind turbine. To this end, certain wind turbine components are configured as large casted structures designed to withstand the high loads experienced during wind turbine operation.
  • the main bearing housing which rotatably supports the main rotor shaft in the nacelle, is typically a large, heavy casted structural component of the wind turbine.
  • the manufacture of large casted wind turbine components is not an exact process and heavily relies on casting experts and suppliers with significant know-how and experience in making casted structures. This results in a trial-and-error approach for arriving at a casting process that results in an acceptable casted component.
  • the casting process will need to account for strength requirements and porosity levels in various regions of the casted structure in order to meet the design specifications.
  • current processes divide a casted component into quality zones (e.g., Classl , 2, 3, and 4) with different levels of specification criteria.
  • a maximum amount of casting defects is typically guaranteed by the supplier. Consequently, a maximum design strength may be designated by the manufacturer within each zone (e.g., with class 1 having the highest design strength). If the casting process results in a casted component that fails to meet the design specifications, then the casting process is modified, under the guidance of the casting experts, and repeated until a casted component resulting from the process can meet the design specifications. Because current processes produce an actual casted component for final or near final iterations of the design process, such an approach is costly and time consuming.
  • the quality zone approach outlined above is a relatively low-resolution strength distribution of the casted structure that treats strength from a more global or regional perspective instead of from a more high-resolution local perspective.
  • Such a low-resolution strength distribution limits a manufacturer's ability to optimize a particular design based on its expected stress distribution (as a result of expected operating loads). Consequently, many casted structures have designs that are overconstrained, which in turn may result in very heavy and costly wind turbine components.
  • the method may further include modifying, by the computer, at least one of the first data or the second data; and repeating the casting simulation step, stress simulation step, comparing step, and modifying step until the virtual casted wind turbine component meets the first pre-determined acceptance threshold.
  • receiving the first data further includes receiving data corresponding to at least one of a three-dimensional model of the casted wind turbine component and one or more materials of the casted wind turbine component.
  • the second data may include specific information regarding the casting process for forming the casted wind turbine component.
  • the first data may include a CAD file used to develop the design of the casted wind turbine component.
  • the second data may be a standard casting process or be a proposed casting process, such as by a casting expert, based on the design.
  • the casting simulation step further includes providing casting simulation software to the computer; executing, by the computer, the casting simulation software based on the first and second data; and determining the representative fatigue strength distribution for the virtual casted wind turbine component based on one or more outputs of the casting simulation software.
  • the determining the representative fatigue strength distribution further includes determining a theoretical fatigue strength distribution for the virtual casted wind turbine component from a first output of the casting simulation software. For example, determining the theoretical fatigue strength distribution may further include using an empirically determined curve for the material of the casted wind turbine component.
  • the step of determining the representative fatigue strength distribution may further include determining an adjusted fatigue strength distribution by reducing the theoretical fatigue strength distribution to account for defects in the virtual casted wind turbine component.
  • determining an adjusted fatigue strength distribution may further include defining a strength reduction factor corresponding to the effect of one or more defects on the fatigue strength of the virtual casted wind turbine component.
  • the strength reduction factor may be based at least on a second output of the casting simulation software, wherein in one embodiment the second output includes a porosity distribution for the virtual casted wind turbine component.
  • the strength reduction factor may be empirically related to the porosity distribution of the virtual casted wind turbine component.
  • the step of determining an adjusted fatigue strength distribution may further include defining a scaling factor.
  • the stress simulation step further includes providing stress simulation software to the computer; executing, by the computer, the stress simulation software based on the first data and one or more load conditions imposed on the virtual casted wind turbine component; and determining the representative stress distribution for the virtual casted wind turbine component based on one or more outputs of the stress simulation software.
  • the method further includes providing a plurality of load conditions to apply to the virtual casted wind turbine component in the stress simulation software; executing, by the computer, the stress simulation software for each of the plurality of load conditions imposed on the virtual casted wind turbine component; and determining the representative stress distribution for the virtual casted wind turbine component based on a combination of stress distributions resulting from each of the plurality of load conditions. For example, an averaging technique of a worst-case approach may be used to determine the representative stress distribution.
  • the plurality of load conditions may include theoretical load conditions, empirical load conditions, or a combination of theoretical and empirical load conditions.
  • the comparing step further includes defining, by the computer, a criticality index distribution based on a ratio of the representative stress to the representative strength at corresponding locations (e.g., nodes) of the virtual casted wind turbine component.
  • the first pre-determined acceptance threshold may be defined as the criticality index being less than 1.0 at each corresponding location of the virtual casted wind turbine component.
  • the modifying step further includes performing, by the computer, a mitigation step to affect the local fatigue strength in regions where the criticality index distribution failed to meet the first pre-determined acceptance threshold.
  • the mitigation step may include modifying the first data to correspond to a variance (e.g., a decrease or increase) in material thickness in regions of the virtual casted wind turbine component where the criticality index distribution failed to meet the first pre-determined acceptance threshold.
  • the mitigation step may include modifying the first and/or second data to correspond to a different casting material of the virtual casted wind turbine component.
  • the mitigation step may include modifying the second data to affect the cooling rate in regions of the virtual casted wind turbine component where the criticality index distribution failed to meet the first predetermined acceptance threshold.
  • the mitigation step may include modifying the first and/or second data to affect the porosity in regions of the virtual casted wind turbine component where the criticality index distribution failed to meet the first pre-determined acceptance threshold.
  • the method may further include estimating, by the computer, a cost for the performance of the mitigation step. In this way, the impact of a mitigation step on cost may be determined and considered in selecting a possible mitigation step.
  • a method of manufacturing a casted wind turbine component includes designing the casted wind turbine component through virtual modelling as described above, and then casting the wind turbine component based on the first and second data resulting from the virtual design process.
  • a casted wind turbine component may be manufactured according to that described above.
  • the casted wind turbine component may include a main bearing housing, for example.
  • a wind turbine may include a casted wind turbine component made in accordance with the manufacturing method described above.
  • Fig. 1 is a perspective view of a wind turbine in which embodiments of the invention may be used;
  • Fig. 3 is a flowchart illustrating a computer-based design process in accordance with an embodiment of the invention
  • Fig. 4 is a flowchart illustrating a strength simulation in accordance with an embodiment of the invention.
  • Fig. 5 is a schematic illustration of an empirical relation between the feeder modulus and the theoretical fatigue strength used to determine theoretical fatigue strength in a casted wind turbine component in accordance with an embodiment of the invention
  • Fig. 6 is a schematic illustration of an exemplary strength reduction factor as a result of porosity in a casted wind turbine component in accordance with an embodiment of the invention
  • Fig. 7 is a flowchart illustrating a stress simulation in accordance with an embodiment of the invention.
  • Fig. 8 is a diagrammatic illustration of a computer that may be used to implement one or more of the processes shown in Figs. 3-7. Detailed Description
  • a wind turbine 10 includes a tower 12, a nacelle 14 disposed at the apex of the tower 12, and a rotor 16 operatively coupled to a generator 18 via a gearbox 20 housed inside the nacelle 14.
  • the nacelle 14 may house various components needed to convert wind energy into electrical energy and to operate and optimize the performance of the wind turbine 10.
  • the tower 12 supports the load presented by the nacelle 14, rotor 16, and other wind turbine components housed inside the nacelle 14 and operates to elevate the nacelle 14 and rotor 16 to a height above ground level or sea level, as may be the case, at which air currents having lower turbulence and higher velocity are typically found.
  • the rotor 16 may include a central hub 22 and a plurality of blades 24 attached to the central hub 22 at locations distributed about the circumference of the central hub 22.
  • the rotor 16 includes three blades 24, however the number may vary.
  • the blades 24, which project radially outward from the central hub 22, are configured to interact with passing air currents to produce rotational forces that cause the central hub 22 to spin about its longitudinal axis.
  • the design, construction, and operation of the blades 24 are familiar to a person having ordinary skill in the art of wind turbine design and may include additional functional aspects to optimize performance.
  • pitch angle control of the blades 24 may be implemented by a pitch control mechanism (not shown) responsive to wind velocity to optimize power production in low wind conditions, and to feather the blades if wind velocity exceeds design limitations.
  • the rotor 16 may be coupled to the gearbox 20 directly or, as shown, indirectly via a main shaft 26 extending between the hub 22 and the gearbox 20.
  • the main shaft rotates with the rotor 16 and is supported within the nacelle 14 by a main bearing housing 28 which supports the weight of the rotor 16 and transfers the loads on the rotor 16 to the tower 12.
  • the gearbox 20 transfers the rotation of the rotor 16 through a coupling to the generator 18. Wind exceeding a minimum level may activate the rotor 16, causing the rotor 16 to rotate in a direction substantially perpendicular to the wind and ultimately applying torque to the input shaft of the generator 18.
  • the electrical power produced by the generator 18 may be supplied to a power grid (not shown) or an energy storage system (not shown) for later release to the grid as understood by a person having ordinary skill in the art. In this way, the kinetic energy of the wind may be harnessed by the wind turbine 10 for power generation.
  • the main bearing housing 28 must be designed with exceptionally high strength to withstand the loads imposed on the main bearing housing 28 during operation of the wind turbine 10.
  • the main bearing housing 28 is typically a casted structural component formed from, for example, an iron alloy, such as ductile iron.
  • the main bearing housing 28 may be formed from spheroidal graphite iron such as GJS-500-18, GJS-500-14, GJS-600-10, other suitable iron- based alloys, or other materials.
  • aspects of the present invention are directed to a method of designing a casted wind turbine component, such as the main bearing housing 28, in a manner that overcomes many of the drawbacks in the manufacturing of casted components, as described above.
  • the method is based on virtual modelling of the wind turbine component and includes an iterative design process based primarily on a comparative analysis of two computer-based simulations. If required, modifications to the virtual casted component or the virtual casting process may be made based on those virtual simulations. Once the virtual design process is complete, the casted wind turbine component may be manufactured based on the outcome of the virtual design process.
  • Fig. 3 is a schematic illustration of the general virtual design process 30 according to an exemplary embodiment of the present invention.
  • a virtual representation of the initial design for the casted component 28 (referred to as the virtual casted component 28') and a virtual representation of the initial casting process (referred to as the virtual casting process) may be proposed or received in block 32.
  • the initial design may represent the designers first attempt at the physical attributes of the casted component 28, including its overall geometry (e.g., size and shape), as well as the material makeup of the casting.
  • the initial casting process may be a standard casting process, or one proposed by a casting expert based on the initial design.
  • a computer-based casting simulation may be performed at block 34. The purpose of the casting simulation is to determine a representative fatigue strength distribution in the virtual casted component 28' based on the virtual casting process.
  • a computer-based stress simulation may be performed on the virtual casted component 28'.
  • the purpose of the stress simulation is to determine a representative stress distribution in the virtual casted component 28' based on one or more load conditions imposed on the virtual casted component 28'.
  • the distribution maps may be compared to each other to obtain some measure of how the representative strength matches up to the representative stress in the virtual casted component 28'. This is illustrated in block 38.
  • the virtual design process 30 may compare the representative strength and stress distributions at corresponding locations to determine whether the results meet a pre-determined acceptance threshold or criteria.
  • the comparison and pre-determined acceptance threshold may be configured to identify those areas or regions of the virtual casted component 28' that may be under designed (e.g., the stress values are greater than the strength values), and therefore subject to mitigation steps.
  • the process may also be configured to identify those areas or regions of the virtual casted component 28' that are over designed (e.g., have strength values much greater than the stress values). These regions may also be subject to mitigation steps.
  • the pre-determined acceptance threshold is not met for the initial design, then the design of the virtual casted component 28' or the virtual casting process may be modified to specifically address the areas of concern, as illustrated in block 42. For example, the structural or material make-up of the virtual casted component 28' may be modified to address the deficiency (i.e., change in geometry or material).
  • aspects of the virtual casting process may be modified in order to increase the strength in the areas of concern.
  • the casting simulation step 34, stress simulation step 36, comparing step 38, and possibly the modifying step 42 of the design process 30 may be repeated for the updated design. This is illustrated by line 44 in Fig. 3. Indeed, this feedback loop of the virtual design process 30 may be repeated multiple times, e.g., based on manual modifications or automated modifications to the design, until an updated design for the virtual casted component 28' satisfies the pre-determined acceptance threshold, indicating acceptability in the overall design and casting process based on virtual modelling.
  • actual manufacturing of the casted component 28 may proceed based on the virtual design and virtual casting process.
  • the method may further include traditional testing of the actual casted component 28 resulting from block 46 as further verification of the design and manufacturing process.
  • the virtual design process 30 described above has many advantages. For example, the method is not based on the trial-and-error approach of conventional casting processes that rely on the skill and experience of casting experts for producing high- quality casted components. Instead, the design process 30 is based on computer- based simulations that model representative strength-stress characteristics of the virtual casted component 28' before the component is actually manufactured. This approach avoids the cost and time of conventional trial and error casting processes. In this regard, the virtual design process 30 outlined above may be implemented at relatively low cost, especially as compared to current processes, and on a time scale that is significantly reduced compared to current casting methodologies.
  • designs of casted components may be optimized for weight. For example, material may be removed from areas which are over designed and added to areas that require strength to match the expected stresses. In this way, material is used in an efficient manner and the overall weight of the casted component may be reduced.
  • designs for casted components may be optimized for cost. For example, by using material efficiently, costs may be reduced.
  • the virtual design process 30 may be used to determine whether the casting process for a selected design of a casted component 28 is relatively high-cost or low-cost. Moreover, designs for casted components may be optimized for time. Thus, the design process 30 provides designers with many more tools for developing a casted component 28 that meets structural and manufacturability criteria.
  • the virtual design process 30 for the casted component 28 calls for a casting simulation in block 34.
  • a casting simulation 52 in accordance with an exemplary embodiment of the invention is illustrated in Fig. 4.
  • a three-dimensional (3-D) representation of the casted component 28 may be generated from an initial (or updated) design of the casted component 28.
  • the design of the casted component 28 may be provided in CAD software, such as AutoCAD, Solidworks, Creo, or other commercially available 3-D CAD software packages on a computer system.
  • the CAD software may then generate an export file storing data on the geometry of the casted component 28.
  • That data constitutes a virtual representation of the casted component 28 and essentially defines the virtual casted component 28'. It should be understood that the above is merely exemplary and the virtual representation of the casted component 28 may be generated and stored in a different manner and remain within the scope of the present invention.
  • the data from the CAD software may be imported into casting simulation software on the computer system so that the geometry/material of the virtual casted component 28' is known and the casting simulation software may operate based on that known geometry.
  • the CAD software may form part of the casting simulation software such that the importing step may be omitted.
  • data on the casting process may also be imported into the casting simulation software.
  • the casting process may be separately inputted into the casting simulation software.
  • that data constitutes a virtual representation of the casting process for casted component 28 and essentially defines the virtual casting process.
  • the ultimate purpose of the casting simulation software is to determine a representative strength distribution in the virtual casted component 28' based upon aspects of the virtual casting process.
  • Casting simulation software packages are generally known in the art and include without limitation ProCAST, QuikCAST, Flow-3D cast, AutoCAST, Altair Inspire Cast, NovaFlow&Solid, and other software packages.
  • Altair Inspire Cast may be used to simulate the casting process of the casted component 28.
  • the casting software may require certain other input parameters into the software, such as material properties, thermal boundary conditions at the surfaces of the virtual casted component, initial temperature of melt, pouring time, design of casting system (e.g., pouring basin, mould, runners, gates, feeders, chillers, and other possible information.
  • the casting simulation software may be executed in block 58 to model the thermal response of the virtual casted material.
  • the casting simulation software will typically generate a 3-D mesh of the geometry as provided by the imported data file and determine the temperature distribution throughout the virtual casted component 28' as the casting cools under the thermal boundary conditions.
  • the thermal response is relevant because the local fatigue strength of a virtual casted component 28' is highly dependent on the local cooling time of the virtual casted component 28'.
  • the cooling time may vary by several orders of magnitude between different regions of the virtual casted component 28'.
  • the output of the casting simulation software includes two distributions of interest to the present invention.
  • the first output of the casting simulation software includes a feeder modulus distribution (referred to herein as feedmod distribution) of the virtual casted component 28' and the second output of the casting simulation software includes a porosity distribution of the virtual casted component 28'.
  • feedmod distribution a feeder modulus distribution
  • porosity distribution a porosity distribution of the virtual casted component 28'.
  • a fatigue strength may be defined on any point on the S-N curve by selecting an appropriate number of cycles (e.g., five million cycles) suitable for a given component and application.
  • the S-N curve may be approximated by the following power law equation: where s is the stress level (provided on the y-axis of the S-N curve), m is the slope of the curve on the logarithmic scale, A is the intercept of the curve on the logarithmic scale, and N is the number of cycles (provided on the x-axis of the S-N curve).
  • N the number of cycles (provided on the x-axis of the S-N curve).
  • a correlation between the fatigue strength and feedmod result from the casting simulations there is a correlation between the fatigue strength and feedmod result from the casting simulations, and that correlation may be empirically determined.
  • a number of test samples of the casted material e.g., about twenty or so samples
  • the test samples are then modelled in the casting software to determine a feedmod FM value for each test sample.
  • the test samples are produced such that the feedmod FM differs for each of the test samples (i.e., to provide a range of feedmod values).
  • the actual test samples are then subjected to fatigue testing to determine their corresponding S-N curves and their particular m and A values.
  • Feedmod FM is closely related to cooling time, which is in turn closely related to the microstructure of the material.
  • m and A values from the S-N curves of the test samples are a function of feedmod FM.
  • the parameters a, b, c and d in equations (2) and (3) may be determined from the data that comes from analysing the test samples.
  • the coefficient a may be between about 10 to about 15 and the exponent b may be between about 0.3 to about 0.4 for iron-based castings.
  • the coefficient c may be between about 30 to about 50 and the exponent d may be between about 0.3 to about 0.4 for iron-based castings.
  • the theoretical fatigue strength DS distribution of the virtual casted component 28' may be determined based on the feedmod FM distribution from the casting simulation software using equation (1) above.
  • Fig. 5 illustrates an exemplary empirically determined curve for ductile iron where the theoretical fatigue strength DS is provided on the y-axis and the feedmod FM is provided on the x-axis.
  • some defects may form in the material of the casting that reduces the fatigue strength.
  • These defects represent initiation sites at which cracks form and propagate during operation of the wind turbine 10, and which ultimately leads to failure of casted component.
  • one such defect includes small voids formed within the material during the casting process due to volumetric contraction during solidification and cooling.
  • the porosity P of the material is a measure of that void formation and effectively weakens the casting in areas where the porosity value is high. Accordingly, to obtain a more accurate representation of the fatigue strength of the virtual casted component 28', defects resulting from the virtual casting process may be accounted for in the strength distribution profile of the virtual casted component 28'.
  • an adjusted fatigue strength DS adj distribution may be determined that accounts for possible defects in the virtual casted component 28'.
  • the porosity P distribution from the casting simulation software may be used to adjust the theoretical fatigue strength DS of the virtual casted component 28'.
  • a strength reduction factor C may be defined that accounts for the reduction in fatigue strength resulting from various defects in the virtual casted component 28'.
  • the strength reduction factor C may be in the range of [0, 1], wherein the smaller the value of the strength reduction factor C, the greater impact the defect has on the fatigue strength of the virtual casted component 28'.
  • the strength reduction factor C may account for multiple defects in the virtual casted component 28'.
  • the strength reduction factor C may be a product of reduction factors resulting from various defects, i.e.,
  • C U Ci, (4)
  • the strength reduction factor due to porosity C por may be empirically based.
  • Fig. 6 illustrates one exemplary approach for specifying the strength reduction factor C as a function of porosity P of the virtual casted component 28' (where P is specified in percentage).
  • the relationship may be provided by two linear equations that change at a critical value in porosity (e.g., 20%).
  • the relationship illustrated in Fig. 6 may be provided by the following equations:
  • the adjusted fatigue strength DS adj distribution for the virtual casted component 28' may be determined.
  • the adjusted fatigue strength DS adj distribution may be determined by:
  • DS adj C - DS, (7) again where DS is determined based on equations (1)-(3) above.
  • further scaling or safety factors may be used to determine an adjusted fatigue strength DS adj distribution.
  • the adjusted fatigue strength DS adj distribution may be determined by:
  • f s is a scaling or safety factor.
  • regulatory, industry, or customer guidelines may require a scaling factor for modelling based on theoretical fatigue strength DS.
  • the scaling factor f s may be in the range of [0, 1], wherein the smaller the value of the scaling factor, the greater the safety zone from the theoretical limits of the design.
  • the safety factor f s may be the ratio of a guideline fatigue strength to the theoretical fatigue strength or the adjusted fatigue strength provided by equation (7) for the material being casted.
  • a scaling factor f s of about 0.65 may be used to determine the adjusted fatigue strength.
  • Other values may also be possible.
  • the culmination of the casting simulation 52, as illustrated in Fig. 4 is a modified fatigue strength DS adj distribution of the virtual casted component 28' that accounts for certain defects from the virtual casting process, thereby representing a more realistic predictive model for the casted component 28, and any regulatory/industry/customer requirements imposed on the design of the casted component 28.
  • the virtual design process 30 for a casted component 28 also calls for a stress simulation in block 36.
  • An exemplary stress simulation 68 is illustrated in Fig. 7.
  • data on the design of the casted component 28 may be imported into the stress simulation software on the computer system.
  • the data for the virtual casted component 28' may be that provided by the CAD software or the casting simulation software, as discussed above. More particularly, for example, the export data from the CAD software may be imported into the stress simulation software on the computer system so that the virtual casted component 28' is known and the stress simulation software may operate based on that known geometry.
  • the ultimate purpose of the stress simulation software is to determine a representative stress distribution in the virtual casted component 28' based on certain imposed load conditions.
  • Stress simulation software packages are generally known in the art and include without limitation Ansys, Autodesk, Dassault Systemes Solidworks, Altair HyperMesh, PTC Creo, and other software packages.
  • Altair HyperMesh may be used to simulate the stresses on the virtual casted component 28' under an imposed load condition.
  • a load condition may be selected and imposed on the virtual casted component 28' in the stress simulation software.
  • the software may be executed in block 74 to determine the stress response of the virtual casted component 28' due to its design and the selected load condition.
  • the stress distribution of the virtual casted component 28' from the selected load condition may be stored in the computer system.
  • a stress distribution may be determined for a plurality of different load conditions imposed on the virtual casted component 28' in the stress simulation software. More particularly, the stress simulation 68 may repeat the selecting step 72, executing step 74 and storing step 76 for a plurality of different load conditions. This is demonstrated in Fig. 5 by line 78.
  • the plurality of load conditions may be maintained as a stored library on the computer system or as part of the stress simulation software for access by the software during the stress simulation 68 of the virtual casted component 28'.
  • the library may be made up of theoretical load conditions, empirically based load conditions, or a combination thereof.
  • the purpose of the library is to virtually subject the virtual casted component 28' to loads in the stress simulation software that the component 28 may actually experience during its operational lifetime in the wind turbine 10.
  • many wind turbine manufacturers monitor forces on various components of the wind turbine 10.
  • various sensors e.g., accelerometers, etc.
  • This data may be used to define one or more empirically based load conditions.
  • force data on a wind turbine component 28 may be collected over a certain period of time (e.g., day/weeks/months).
  • that data may then be analysed to determine an average load condition or a worst-case load condition, for example.
  • the data may be analysed to determine a standard low-wind load condition, medium-wind load condition, and a high-wind load condition.
  • wind data from a planned wind turbine installation site may be analysed to determine average and/or worst-case load conditions.
  • any regulations or guidelines require testing with certain load conditions, such regulator load conditions may form part of the library.
  • the one or more load conditions maintained in the library for applying to the virtual casted component 28' in the stress simulation software may be defined in a wide variety of ways including various theoretical, empirical, and statistic methodologies. Accordingly, aspects of the invention should not be limited to the particular type of load condition applied to the virtual casted component 28' or the particular manner in which the load condition was determined.
  • the stress simulation 68 may include defining a cumulative stress distribution in the virtual casted component 28' based on the one or more stress distributions s ⁇ stored in the computer system.
  • the cumulative stress distribution a cum may be a single stress distribution map of the virtual casted component 28' that is representative of the plurality of stored stress distributions a t .
  • a wide variety of statistical analyses may be applied to define the representative cumulative stress distribution a cum .
  • an averaging process may be applied to define the cumulative stress distribution a cum of the casted component 28.
  • the maximum value at each node point of the virtual casted component 28' across the plurality of stress distributions may define the cumulative stress distribution a cum .
  • This embodiment may, for example, define a worst-case cumulative distribution based upon the plurality of load conditions applied in the design process.
  • the comparing block 38 may be based on the adjusted strength distribution DS adj as provided by the casting simulation 52 illustrated in Fig. 4 and the cumulative stress distribution a cum as provided by the stress simulation 68 illustrated in Fig. 5.
  • the comparing block 38 may include defining a criticality index Cl as the ratio of the representative stress at a location of the casted component 28 to the representative strength at that location (i.e., at corresponding locations):
  • equation (9) does not include a safety factor because, for example, the safety and scaling factors were already accounted for in the casting simulation 52 for determining the adjusted fatigue strength DS adj . Nevertheless, in another embodiment a further safety factor may be applied to the calculation for the criticality index Cl. In any event, the application of equation (9) results in a criticality index Cl distribution for the casted component 28.
  • the pre-determined acceptance threshold identified in block 40 of the design process 30 in Fig. 3 may be applied to the criticality index Cl distribution.
  • the pre-determined acceptance threshold may be:
  • the adjusted fatigue strength DS adj of the casted component 28 at a location (e.g., defined at the nodes of the mesh of the 3-D model) must be greater than the cumulative stress a cum at that location. If the design of the virtual casted component 28' meets the acceptance threshold, then no mitigation efforts are required in the design of the virtual casted component 28' or the virtual casting process at that location. On the other hand, if the design of the virtual casted component 28' fails to meet the acceptance threshold, then mitigation efforts must be implemented in the design of the virtual casted component 28' or virtual casting process at that location.
  • the application of the pre-determined acceptance threshold to the criticality index distribution may be configured to immediately (e.g., visually) identify those areas of the virtual casted component 28' where mitigation efforts may be required. While equation (10) exemplifies one way to define the predetermined acceptance criteria, aspects of the invention are not so limited. In this regard, it should be understood that other pre-determined acceptance thresholds may be used in the virtual design process 30.
  • the pre-determined acceptance threshold provided by equation (10) is a uniform or constant value across all of the nodes of the mesh of the 3-D model, aspects of the invention are not so limited.
  • the criticality index Cl distribution may be provided by a non-uniform pre-determined acceptance threshold.
  • certain parts of the virtual casted component 28' may have a pre-determined acceptance threshold of one value and other parts of the virtual casted component 28' may have a pre-determined acceptance threshold of another value.
  • the pre-determined acceptance threshold is preferably less than one. However, in some areas of the casted component 28, some yielding of the material (e.g., less than about 2%) may be permitted in an acceptable design. Alternatively, certain regions of the casted component 28 may have low criticality to the overall function and safety of the wind turbine. Thus, in an alternative embodiment, the pre-determined acceptance threshold may also be greater than one for select areas of the virtual casted component 28'.
  • mitigation steps may be taken to address the deficiency.
  • these mitigation steps may take several forms.
  • the virtual casting process may be modified in order to increase the fatigue strength of the virtual casted component 28' in the particular areas of concern, as identified by the criticality index distribution.
  • the fatigue strength of the virtual casted component 28' may be heavily dependent on the cooling time of the (virtual) casted material.
  • the cooling time of the casted material in the particular areas of concern can be altered (e.g., decreased), then then fatigue strength of the casted material in that area may be likewise altered (e.g., increased).
  • the virtual casting process may be altered to include one or more chillers configured to create a local cooling effect, and thereby impact cooling time in a manner that increases the local fatigue strength. Such a modification is accounted for by the thermal boundary conditions in the virtual casting process, for example.
  • the fatigue strength of the virtual casted component 28' may be dependent upon the local porosity of the virtual casted component 28'.
  • the porosity of the casted material in the particular area of concern can be altered (e.g., decreased), then the fatigue strength of the casted material in that area may be likewise altered (e.g., increased).
  • the virtual casting process may be altered to include one or more feeders configured to fill any voids created by material shrinkage during virtual curing, and thereby reduce porosity so as to increase the local fatigue strength. It should be realized that the above approach seeks to impact the design by modifying the virtual casting process in a way that increases local fatigue strength values in the areas of concern identified by the criticality index distribution. Various means for affecting local fatigue strength values resulting from the virtual casting process should not be limited to those identified above. There may indeed be other avenues for increasing local fatigue strength values through modification of the virtual casting process that remain within the scope of the present invention.
  • the geometry of the virtual casted component 28' may be altered to address the areas of concern in the design.
  • the local thickness of the casted material may be varied in the areas of concern to thereby increase the local fatigue strength values of the material in those areas.
  • the local thickness of the casted material may be increased to increase the local strength.
  • the local thickness of the casted material may be decreased to decrease the effects of porosity (which are greater for thicker casted bodies).
  • the material aspects of the virtual casted component 28' may be altered to address the areas of concern in the design.
  • another material may be selected for the virtual casted component 28'.
  • aspects of the present invention are not limited to modifying the geometry of the virtual casted component 28' only in the areas which do not satisfy the pre-determined acceptance threshold. More particularly, the criticality index distribution will not only identify those regions of the virtual casted component 28' that are under designed (i.e., do not meet the acceptance threshold), but will also identify those regions of the virtual casted component 28' that are over designed. Over designed regions of the virtual casted component 28' are regions where the local strengths are much greater than the local stresses.
  • another acceptance threshold may be defined that identifies regions of the virtual casted component 28' that may be altered to reduce the local fatigue strength in order to save weight and cost.
  • the design may be modified to reduce the fatigue strength in those regions. For example, material thicknesses may be reduced in those areas and/or the geometry of the virtual casted component 28' in those areas may be modified.
  • This process may result in a design of the virtual casted component 28' that is smaller and uses less material but yet satisfies the structural requirements of the component 28 in the wind turbine 10.
  • the mitigation steps discussed above may be analysed from a cost perspective to determine whether taking a certain mitigation step is reasonable from a financial perspective.
  • a cost of the one or more chillers and their operation may be associated with that mitigation step.
  • a cost of one or more feeders in the casting can be associated with a mitigation step calling for such feeders.
  • material costs associated with the addition or removal of material in the virtual casted component 28' may also be accounted for.
  • the computer system or software may include a library of typical costs associated with certain actions in the mitigation process. In this way, a cost of a mitigation step may be estimated to determine whether the modification proposed by the mitigation step makes financial sense.
  • the processor 86 may include one or more devices selected from microprocessors, micro-controllers, digital signal processors, microcomputers, central processing units, field programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, or any other devices that manipulate signals (analog or digital) based on operational instructions that are stored in memory 88.
  • Memory 88 may include a single memory device or a plurality of memory devices including, but not limited to, read-only memory (ROM), random access memory (RAM), volatile memory, non-volatile memory, static random access memory (SRAM), dynamic random access memory (DRAM), flash memory, cache memory, or data storage devices such as a hard drive, optical drive, tape drive, volatile or nonvolatile solid state device, or any other device capable of storing data.
  • ROM read-only memory
  • RAM random access memory
  • volatile memory volatile memory
  • non-volatile memory volatile memory
  • SRAM static random access memory
  • DRAM dynamic random access memory
  • flash memory cache memory
  • data storage devices such as a hard drive, optical drive, tape drive, volatile or nonvolatile solid state device, or any other device capable of storing data.
  • the processor 86 may operate under the control of an operating system 98 that resides in memory 88.
  • the operating system 98 may manage computer resources so that computer program code embodied as one or more computer software applications, such as an application 100 residing in memory 88, may have instructions executed by the processor 86.
  • the processor 86 may execute the application 100 directly, in which case the operating system 98 may be omitted.
  • One or more data structures 102 may also reside in memory 88, and may be used by the processor 86, operating system 98, or application 100 to store or manipulate data.
  • the I/O interface 90 may provide a machine interface that operatively couples the processor 86 to other devices and systems, such as the external resource 94 or the network 96.
  • the application 100 may thereby work cooperatively with the external resource 94 or network 96 by communicating via the I/O interface 90 to provide the various features, functions, applications, processes, or modules comprising embodiments of the invention.
  • the application 100 may also have program code that is executed by one or more external resources 94, or otherwise rely on functions or signals provided by other system or network components external to the computer 84.
  • embodiments of the invention may include applications that are located externally to the computer 84, distributed among multiple computers or other external resources 94, or provided by computing resources (hardware and software) that are provided as a service over the network 96, such as a cloud computing service.
  • the HMI 92 may be operatively coupled to the processor 86 of computer 84 to allow a user to interact directly with the computer 84.
  • the HMI 92 may include video or alphanumeric displays, a touch screen, a speaker, and any other suitable audio and visual indicators capable of providing data to the user.
  • the HMI 92 may also include input devices and controls such as an alphanumeric keyboard, a pointing device, keypads, pushbuttons, control knobs, microphones, etc., capable of accepting commands or input from the user and transmitting the entered input to the processor 96.
  • a database 104 may reside in memory 88, and may be used to collect and organize data used by the various systems and modules described herein.
  • the database 104 may include data and supporting data structures that store and organize the data.
  • the database 104 may be arranged with any database organization or structure including, but not limited to, a relational database, a hierarchical database, a network database, or combinations thereof.
  • a database management system in the form of a computer software application executing as instructions on the processor 88 may be used to access the information or data stored in records of the database 104 in response to a query, which may be dynamically determined and executed by the operating system 98, other applications 100, or one or more modules.
  • routines executed to implement the embodiments of the invention may be referred to herein as “computer program code,” or simply “program code.”
  • Program code typically comprises computer-readable instructions that are resident at various times in various memory and storage devices in a computer and that, when read and executed by one or more processors in a computer, cause that computer to perform the operations necessary to execute operations or elements embodying the various aspects of the embodiments of the invention.
  • Computer-readable program instructions for carrying out operations of the embodiments of the invention may be, for example, assembly language, source code, or object code written in any combination of one or more programming languages.
  • the program code embodied in any of the applications/modules described herein is capable of being individually or collectively distributed as a computer program product in a variety of different forms.
  • the program code may be distributed using a computer-readable storage medium having computer-readable program instructions thereon for causing a processor to carry out aspects of the embodiments of the invention.
  • a computer-readable storage medium should not be construed as transitory signals per se (e.g., radio waves or other propagating electromagnetic waves, electromagnetic waves propagating through a transmission media such as a waveguide, or electrical signals transmitted through a wire).
  • Computer-readable program instructions may be downloaded to a computer, another type of programmable data processing apparatus, or another device from a computer-readable storage medium or to an external computer or external storage device via a network.

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Abstract

Un procédé de conception d'un composant de turbine éolienne coulé (28) consiste à recevoir, au niveau d'un ordinateur, des premières données définissant une conception virtuelle du composant coulé et des secondes données définissant un processus de coulée virtuel ; à effectuer, par l'ordinateur, une simulation de coulée sur la base des premières données et des secondes données pour déterminer une distribution de résistance à la fatigue représentative du composant coulé virtuel ; à effectuer, par l'ordinateur, une simulation de contrainte sur la base des premières données pour déterminer une distribution de contrainte représentative du composant coulé virtuel ; et à comparer, par l'ordinateur, les distributions de résistance et de contrainte représentatives pour déterminer si le composant coulé virtuel respecte un seuil d'acceptation. Si le composant coulé ne parvient pas à satisfaire le seuil d'acceptation, le procédé consiste à modifier, par l'ordinateur, au moins l'une des premières données ou des secondes données ; et à répéter la simulation de coulée, la simulation de contrainte, à comparer et à modifier des étapes jusqu'à ce que le composant coulé virtuel respecte le seuil d'acceptation. La divulgation concerne également un procédé de fabrication du composant coulé (28) sur la base du processus de conception.
PCT/DK2021/050189 2020-06-26 2021-06-14 Procédé de conception de composants structuraux de turbine éolienne coulés par modélisation virtuelle et son procédé de fabrication WO2021259432A1 (fr)

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