CN106021827A - Topological design method for inner structure of wind turbine blade in consideration of aerodynamic load - Google Patents

Abstract

The invention discloses a topological design method for an inner structure of a wind turbine blade in consideration of aerodynamic load. The method comprises the following steps: establishing a blade finite element solid model by utilizing APDL language according to the geometric dimension of the blade; dividing a complex blade into a plurality of geometric topological areas and then performing hexahedral meshing on each of the geometric topological areas, thereby realizing overall hexahedral meshing for the blade; calculating the aerodynamic pressure distribution of the blade by combining RFOIL software and momentum blade element theory and then giving the typical blade wing panel aerodynamic loading distribution condition; performing optimum design on the blade topological structure in consideration of aerodynamic load through the pressure distribution data, thereby acquiring the stress transferring paths of different parts of the blade; performing topological structure optimization on the blade according to the stress transferring paths, thereby designing the light blade meeting the mechanical property. According to the invention, the wind turbine blade structure with light weight, high structural force-transferring efficiency and strength meeting requirements can be designed.

Description

A kind of pneumatic equipment blades internal structure topology design method considering aerodynamic loading

Technical field

The invention belongs to wind turbine blade structure design field, be specifically related to a kind of pneumatic equipment blades internal junction considering aerodynamic loading Structure topology design method.

Background technology

Along with wind energy conversion system power is increasing, the size of its blade is more and more longer, and the construct validity how improving blade seems Particularly important.A kind of effective method is how to reduce the quality of blade on the premise of ensureing blade construction intensity.

As a example by using certain novel 2MW pneumatic equipment blades as Topology Structure Design object.This blade aerodynamic profile is by CQU-A aerofoil profile Series, its blade chord length, torsional angle and maximum relative thickness change as shown in Figure 1 to Figure 3 along span of foil direction.Based on three-dimensional Blade complex-curved integrated presentation formula, is coupled to aerofoil profile in this integrated presentation formula, programs and be translated into space three-dimensional number Strong point, uses APDL language establishment macro document to form data delivery mechanism with this data point, thus it is limited to set up blade parameterization Unit's physical model, as shown in Figure 4.

Mesh quality is required the highest, especially for pneumatic equipment blades complexity aerodynamic configuration curved surface by topological optimization, it is desirable to have effect, Accurate unit catches topological structure.Therefore, network topology technology is always the technology difficulty of wind turbine blade structure topological optimization One of topic.Due to blade from blade root to blade tip thickness change span greatly, blade profile air foil shape is complicated, conventional blade grid Dividing is all that free tetrahedral grid divides, and its shortcoming is that topologies degree of accuracy is difficult to ensure that, and amount of calculation is relatively big, needs Waste more calculates resource.Trace it to its cause and the most do not introduce blade profile topological net technology, it is achieved blade interior entity Hexahedral mesh Topology partition.

Summary of the invention

In order to solve above-mentioned technical problem, the technical solution used in the present invention is:

A kind of pneumatic equipment blades internal structure topology design method considering aerodynamic loading, it is characterised in that comprise the following steps:

Step one, according to blade geometry size, utilize APDL speech to set up blade solid finite element model；

Step 2, complicated blade is divided into multiple geometry topology area, then each geometry topology area is carried out hexahedron Stress and strain model, thus realize hexahedro stress and strain model overall to blade；

Step 3, carry out aerodynamic loading analysis for one of them geometry topology area, based on blade momentum theory, in conjunction with RFOIL Computed in software aerodynamic data out, tries to achieve the pressure distribution number of this geometry topology area blade wing panel under accidental conditions According to；

Step 4, accounted for by the pressure distribution data of blade surface aerodynamic loading blade topological structure optimization design, Stress pipeline to blade different parts；

Step 5, by the stress pipeline of blade different parts, blade interior structure is carried out initial optimization, thus design Meet the lighting blade of mechanical property.

Preferably, in described step 4 topological structure optimization design process, the contoured surface of blade uses shell unit, is not involved in Topology optimization design, to ensure smooth surface；Described blade interior entity uses solid45 unit, and dividing total unit number is 10-40 Ten thousand.

Preferably, to using isotropic material to be analyzed during material behavior demand analysis in described step 4, beneficially blade Topological structure initial designs, anisotropic material has directive significance equally simultaneously.

Preferably, during aerodynamic loading is analyzed, choose blade profile and research and analyse to 25%-80% position along exhibition, side Just topological structure is seen clearly.

The medicine have the advantages that

Blade topology design belongs to a kind of conceptual design method, and it provides theoretical foundation for blade dimensions optimization design.By this The conception of species designs, and can be designed that the novel wind motor that light weight, structure power transmission efficiency are high, intensity meets the superior functions such as requirement Blade construction.

Accompanying drawing explanation

Fig. 1 is blade chord length scattergram；

Fig. 2 twist angle of blade scattergram；

Fig. 3 is vane thickness scattergram；

Fig. 4 is pneumatic equipment blades geometry threedimensional model；

Fig. 5 is blade profile topologies；

Fig. 6 wing panel hexahedron topological structure；

Fig. 7 is exhibition blade profile pressure distribution when the r/R=0.25 of position

Fig. 8 is blade profile pressure distribution schematic diagram；

Fig. 9 is blade wing panel pressure distribution

Figure 10 is integral blade topological optimization result；

Figure 11 is cross section topological optimization result at span of foil about 25%；

Figure 12 is cross section topological optimization result at span of foil about 80%.

Detailed description of the invention

Below in conjunction with the accompanying drawings the present invention is illustrated.

The present invention proposes a kind of blade profile topologies, opens up as it is shown in figure 5, complicated blade profile is divided into six geometry Flutterring region, each topology area all can realize hexahedral mesh and divide, and final whole blade entity can realize hexahedral mesh and divide. Choosing blade wing panel, as shown in Figure 6, as seen from the figure, this hexahedral element can be preferable for its hexahedral mesh FEM (finite element) model Seizure topological structure, its aerodynamic configuration surface is also more smooth compared with tetrahedron element simultaneously, beneficially aerodynamic force load.

The present embodiment chooses certain novel 2MW pneumatic equipment blades as Topology Structure Design object.Complex-curved based on three dimendional blade Integrated presentation formula, utilizes MATLAB and APDL language to program and carries out data delivery mechanism, establish parametrization blade 3D solid finite element model；For blade profile complicated shape, it is proposed that a kind of new geometry topological structure, this technology energy Enough realize the full hexahedral element of blade entity；Consider that aerodynamic loading acts on blade aerodynamic contoured surface, (minimum with minimum weight Volume) it is that object function sets up blade topological optimization FEM (finite element) model, and give topological optimization result.

(1) aerodynamic loading and boundary condition

Pneumatic equipment blades is simultaneously by the load effects of being intercoupled such as aerodynamic force, gravity and inertia force, conventional blade construction topology Design generally aerodynamic loading is converted into concentrated bending moment and moment of torsion loads, and it is special to have ignored real spoon of blade pressure distribution Property.Therefore, this research considers blade surface pressure distribution, and pneumatic equipment blades carries out topological structure initial optimization design.In conjunction with RFOIL computed in software aerodynamic data out and blade momentum theory, can try to achieve each aerofoil section under accidental conditions Pressure distribution data.Act on the Pneumatic pressure on blade to try to achieve according to formula (1):

$p=\frac{1}{2}{\mathrm{\ρv}}_{rel}{C}_p+p_{\mathrm{\∞}}---\left(1\right)$

Wherein ρ is that atmospheric density takes 1.205kg/m³；C_pFor pressure coefficient, it is known that the angle of attack can use RFOIL computed in software to ask Go out；p_∞For standard atmospheric pressure, v_relFor acting on the relative velocity on blade, speed relatively can be tried to achieve based on blade momentum theory Degree, such as formula (2):

$v_{rel}=\sqrt{v_x^2+v_y^2}=\sqrt{{(1-a)}^2{v}_0^2+{(1+b)}^2{\left(\mathrm{\ω}r\right)}^2}---\left(2\right)$

V in formula₀Wind speed；

ω wind wheel angular velocity of rotation (rad/s)；

R foline is opened up to position along blade；

The axial inducible factor of a, b and circumference inducible factor；

v_x、v_yFlow the wind speed velocity component in x, y direction.

And axially inducible factor a and circumference inducible factor b is represented by

$a=\frac{2+Y_1-\sqrt{4Y_1(1-F)+Y_1^2}}{2(1+{\mathrm{FY}}_1)}---\left(3\right)$

$b=\frac{1}{(1-aF)Y_2/(1-a)-1}---\left(4\right)$

Y in formula₁=4Fsin²φ/(σC_nF₁)；

Y₂=4Fsin φ cos φ/(σ C_tF₁)；

$F=\frac{2}{\mathrm{\π}}{\cos }^{-1}\[\exp (-\frac{B(R-r)}{2r\sin \mathrm{\φ}})\];$

$\mathrm{\φ}=\arctan \frac{(1-a)v_0}{(1+b)\mathrm{\ω}r};$

C_n=C_lcosφ+C_dsinφ；

C_t=C_lsinφ-C_dcosφ；

$F_1=\frac{2}{\mathrm{\π}}{\cos }^{-1}\[\exp (-g\frac{B(R-r)}{2r\sin \mathrm{\φ}})\];$

σ=Bc/ (2 π r), B are the number of blade, and c is that foline opens up the chord length to r position along blade；

G=exp [-0.125 (B λ-21)]+0.1；

λ=wR/v₀；R is wind wheel blade length；

Program continuous iterative a and b, substitutes into formula (2) and can obtain the relative velocity of each blade profile, further according to formula (1) pressure distribution on each foline can be calculated.In order to simplify aerodynamics evaluation, herein whole blade is divided into 24 and cuts Face wing panel, applies different two-dimensional gas dynamic loadings to each blade wing panel.The pressure distribution of each blade wing panel is with higher order polynomial The form of matching is applied in FEM (finite element) model.Fig. 7 is that the matching pressure distribution opened up at 25% away from blade is distributed with discrete pressure Comparison diagram (wind speed 12.5m/s, rated speed is 20r/min).As seen from the figure, use order polynomial fits, except pressure Outside the power distribution bigger position of Curvature varying (about 0.5 times of chordwise location), can represent that the discrete pressure of blade profile section surface divides exactly Layout.Program and realize whole blade aerodynamic power LOAD FOR and matching, and be loaded in FEM (finite element) model, Fig. 8 and Fig. 9 For respective vanes wing panel FEM (finite element) model aerodynamic load load condition, the direction of arrow represents wing panel Impact direction, arrow length table Show blade wing panel pressure distribution size.

Owing to blade its root that is in operation is fixed on wheel hub, therefore root of blade BORDER PROCESSING is fixed constraint.Additionally, leaf Sheet smooth surface is the guarantee that aeroperformance is good, in process of topology optimization, it is ensured that its curved surface is complete and smooth.Therefore, Aerodynamic configuration surface uses shell unit, is not involved in topology optimization design (non-topology design region).And blade interior entity is adopted Use solid45 unit, for topology design region.The final total unit number divided is about 200,000.Material behavior uses accurate respectively to same Property material, its Young's modulus is 44GPa, modulus of shearing 17.3GPa, and Poisson's ratio is 0.27.Although pneumatic equipment blades material is special Sex expression is anisotropy (blade is fabricated by by composite), and anisotropic material cannot be used to carry out mould for solid element Intend, but for blade topological structure initial designs, use isotropic structure unit to have directive significance equally.

(2) topological optimization and interpretation of result

The purpose of topological optimization is the density of material distribution of reasonable in design section and optimal stress bang path.Herein Material interpolation model based on SIMP, is converted into continuous optimization problems by Discretization, and Optimality Criteria uses MMA algorithm, Under aerodynamic loading effect, it is deformed into constraints with stress and blade tip, with lightweight (minimum volume) as object function, builds Vertical three-dimensional blade forms topological optimization mathematical model:

Object function: f (x)=min (V)

Constraints: σ_m≤175MPa

δ_tip≤6m

Wherein σ_mFor von Mises stress, δ_tipDeform for waving the blade tip of flap-wise.

Owing to using hexahedron topological net technology, calculating resource and time are saved to a certain extent.Computer uses internal memory 8Gb, i5 dual core processor (2 × 3.30Hz), restrains through 48 hours iteration 20 steps.Its topological optimization result such as Figure 10 institute Show: blade girder extends near blade tip from blade root along spanwise direction, and girder is concentrated in front of the blade along the tangential position of blade profile At edge and maximum gauge.This is concentrated mainly near blade inlet edge and aerodynamic center (such as figure mainly due to aerodynamic force suffered by blade Shown in 8), and aerodynamic center position is close with maximum gauge position, about near 0.25 times of chord length, topological optimization will be towards more preferably Mode of transfer force remove unnecessary material, retain blade girder structure.

In order to see topological structure details clearly, take blade profile respectively and carry out studying (such as Figure 11 to about 25% and 80% position along exhibition Shown in 10).As seen from the figure: girder is wider than at lee face (suction surface) at the width of windward side (pressure face), with Girder to extend to blade tip, blade girder substantially covers whole windward side, and web structure occurs；It addition, whole blade is at the wing Reinforcement material structure is occurred in that at type trailing edge.Compare traditional blades internal structure, on this new blade topological structure difference is Lower aerofoil girder position shows as occurring in that at asymmetry and blade trailing edge reinforcement material structure.Main reason is that traditional leaf Chip architecture designs, and the aerodynamic force suffered by blade is converted into blade profile moment of flexure and moment of torsion, and is simplified by complex leaf aerodynamic configuration Design for simply supported beam processes.And this research considers aerodynamic loading distribution, the physical essence of vane stress more can be reflected.

Claims (4)

1. the pneumatic equipment blades internal structure topology design method considering aerodynamic loading, it is characterised in that comprise the following steps:

Step one, according to blade geometry size, utilize APDL speech to set up blade solid finite element model；

Step 2, complicated blade is divided into multiple geometry topology area, then each geometry topology area is carried out hexahedral mesh division, thus realizes hexahedro stress and strain model overall to blade；

Step 3, carry out aerodynamic loading analysis for one of them geometry topology area, based on blade momentum theory, in conjunction with RFOIL computed in software aerodynamic data out, try to achieve the pressure distribution data of this geometry topology area blade wing panel under accidental conditions；

Step 4, accounted for by the pressure distribution data of blade surface aerodynamic loading blade topological structure optimization design, obtain the stress pipeline of blade different parts；

Step 5, by the stress pipeline of blade different parts blade interior structure carried out initial optimization, thus design the lighting blade meeting mechanical property.

A kind of pneumatic equipment blades internal structure topology design method considering aerodynamic loading the most as claimed in claim 1, it is characterized in that: in described step 4 topological structure optimization design process, the contoured surface of blade uses shell unit, is not involved in topology optimization design, to ensure smooth surface；Described blade interior entity uses solid45 unit, and dividing total unit number is 10-40 ten thousand.

A kind of pneumatic equipment blades internal structure topology design method considering aerodynamic loading the most as claimed in claim 1, it is characterised in that: to using isotropic material to be analyzed during material behavior demand analysis in described step 4.

A kind of pneumatic equipment blades internal structure topology design method considering aerodynamic loading the most as claimed in claim 1, it is characterised in that: during aerodynamic loading is analyzed, choose blade profile and research and analyse to 25%-80% position along exhibition.