Optimized Design of Bio-Inspired Wind Turbine Blades

To enhance the aerodynamic performance of wind turbine blades,this study proposes the adoption of a bionic airfoil inspired by the aerodynamic shape of an eagle.Based on the blade element theory,a non-uniform extraction method of blade elements is employed for the optimization design of the considered wind turbine blades.Moreover,Computational Fluid Dynamics(CFD)is used to determine the aerodynamic performances of the eagle airfoil and a NACA2412 airfoil,thereby demonstrating the superior aerodynamic performance of the former.Finally,a mathematical model for optimizing the design of wind turbine blades is introduced and a comparative analysis is conducted with respect to the aerodynamic performances of blades designed using a uniform extraction approach.It is found that the blades designed using non-uniform extraction exhibit better aerodynamic performance.

Research on the Icing Diagnosis ofWind Turbine Blades Based on FS–XGBoost–EWMA

In winter,wind turbines are susceptible to blade icing,which results in a series of energy losses and safe operation problems.Therefore,blade icing detection has become a top priority.Conventional methods primarily rely on sensor monitoring,which is expensive and has limited applications.Data-driven blade icing detection methods have become feasible with the development of artificial intelligence.However,the data-driven method is plagued by limited training samples and icing samples;therefore,this paper proposes an icing warning strategy based on the combination of feature selection(FS),eXtreme Gradient Boosting(XGBoost)algorithm,and exponentially weighted moving average(EWMA)analysis.In the training phase,FS is performed using correlation analysis to eliminate redundant features,and the XGBoost algorithm is applied to learn the hidden effective information in supervisory control and data acquisition analysis(SCADA)data to build a normal behavior model.In the online monitoring phase,an EWMA analysis is introduced to monitor the abnormal changes in features.A blade icing warning is issued when themonitored features continuously exceed the control limit,and the ambient temperature is below 0℃.This study uses data fromthree icing-affected wind turbines and one normally operating wind turbine for validation.The experimental results reveal that the strategy can promptly predict the icing trend among wind turbines and stably monitor the normally operating wind turbines.

Nonlinear Flap-Wise Vibration Characteristics ofWind Turbine Blades Based onMulti-Scale AnalysisMethod

This work presents a novel approach to achieve nonlinear vibration response based on the Hamilton principle.We chose the 5-MW reference wind turbine which was established by the National Renewable Energy Laboratory(NREL),to research the effects of the nonlinear flap-wise vibration characteristics.The turbine wheel is simplified by treating the blade of a wind turbine as an Euler-Bernoulli beam,and the nonlinear flap-wise vibration characteristics of the wind turbine blades are discussed based on the simplification first.Then,the blade’s large-deflection flap-wise vibration governing equation is established by considering the nonlinear term involving the centrifugal force.Lastly,it is truncated by the Galerkin method and analyzed semi-analytically using the multi-scale analysis method,and numerical simulations are carried out to compare the simulation results of finite elements with the numerical simulation results using Campbell diagram analysis of blade vibration.The results indicated that the rotational speed of the impeller has a significant impact on blade vibration.When the wheel speed of 12.1 rpm and excitation amplitude of 1.23 the maximum displacement amplitude of the blade has increased from 0.72 to 3.16.From the amplitude-frequency curve,it can be seen that the multi-peak characteristic of blade amplitude frequency is under centrifugal nonlinearity.Closed phase trajectories in blade nonlinear vibration,exhibiting periodic motion characteristics,are found through phase diagrams and Poincare section diagrams.

Research on Fatigue Damage Behavior of Main Beam Sub-Structure of Composite Wind Turbine Blade

Given the difficulty in accurately evaluating the fatigue performance of large composite wind turbine blades(referred to as blades),this paper takes the main beam structure of the blade with a rectangular cross-sectionas the simulation object and establishes a composite laminate rectangular beam structure that simultaneouslyincludes the flange,web,and adhesive layer,referred to as the blade main beam sub-structure specimen,throughthe definition of blade sub-structures.This paper examines the progressive damage evolution law of the compositelaminate rectangular beam utilizing an improved 3D Hashin failure criterion,cohesive zone model,B-K failurecriterion,and computer simulation technology.Under static loading,the layup angle of the anti-shear web hasa close relationship with the static load-carrying capacity of the composite laminate rectangular beam;under fatigueloading,the fatigue damage will first occur in the lower flange adhesive area of the whole composite laminaterectangular beam and ultimately result in the fracture failure of the entire structure.These results provide a theoreticalreference and foundation for evaluating and predicting the fatigue performance of the blade main beamstructure and even the full-size blade.

Flashover Probability of Wind Turbine Blade and Impact of Strong Electromagnetic Pulse from Lightning Strikes on Wind Turbine Safety

This paper systematically studies the flashover probability of wind turbine blade lightning arrester and the impact of strong electromagnetic pulses on the local and surrounding wind turbines during lightning strikes.The research results indicate that the flashover probability of direct lightning strikes by the wind turbine blade lightning arrester is almost negligible,and the strong electromagnetic pulse of wind turbine blade during lightning strikes has a serious impact on the electronic equipment of the machine,while the impact on the surrounding wind turbine is relatively small.At the same time,the calculation formula for the reflection of lightning current on the carbon brush between the wind turbine hub and the engine compartment during the flashing of the wind turbine blades is provided,and the calculation method for calculating the spatial gradient distribution of electromagnetic field intensity using Biot-Savart Law theorem is applied.The limitations of using wind turbine blades for lightning protection are pointed out,and a technical route for achieving wind turbine lightning safety is proposed,which can be used as a reference for wind turbine lightning protection technicians.

Wind Turbine Noise Reduction through Blade Retrofitting

This paper outlines a plan for the effective reduction of the audible sound level produced by aerodynamic noise from the power-generating turbine blades. The contribution of aerodynamic noise can be divided into two categories: inflow turbulence and airfoil self-noise. The base model and retrofit blade designs were modeled in SolidWorks. Subsequently, noise prediction simulations were conducted and compared to the base blade model to determine which modification provided the greatest benefit using SolidWorks Flow Simulation. The result of this project is a series of blade retrofit recommendations that produce a more acoustically efficient design and reduce noise complaints while enabling turbines to be placed in locations that require quieter operations.

Thermal Analysis of Turbine Blades with Thermal Barrier Coatings Using Virtual Wall Thickness Method

Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results show that the virtualwall thickness method can improve themesh quality by 20%,reduce the number ofmeshes by 76.7%and save the calculation time by 35.5%,compared with the traditional real wall thickness method.The average calculation error of the two methods is between 0.21%and 0.93%.Furthermore,the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition.The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant.The thermal insulation effect of TBCs is the worst near the air film hole,and the best at the blade leading edge.According to the calculated temperature field of the substrate-coating system,the highest thermal insulation temperature of the TC layer is 172.01 K,and the thermal insulation proportions of TC,TGO and BC are 93.55%,1.54%and 4.91%,respectively.

Stiffness Degradation Modeling for Composite Wind Turbine Blades Based on Full-Scale Fatigue Testing

In order to provide more insights into the damage propagation composite wind turbine blades(blade)under cyclic fatigue loading,a stiffness degradation model for blade is proposed based on the full-scale fatigue testing of a blade.A novel non-linear fatigue damage accumulation model is proposed using the damage assessment theories of composite laminates for the first time.Then,a stiffness degradation model is established based on the correlation of fatigue damage and residual stiffness of the composite laminates.Finally,a stiffness degradation model for the blade is presented based on the full-scale fatigue testing.The scientific rationale of the proposed stiffness model of blade is verified by using full-scale fatigue test data of blade with a total length of 52.5 m.The results indicate that the proposed stiffness degradation model of the blade agrees well with the fatigue testing results of this blade.This work provides a basis for evaluating the fatigue damage and lifetime of blade under cyclic fatigue loading.

Damage Identification of Wind Turbine Blades–A Brief Review

The increasing size of these blades of wind turbines emphasizes the need for reliable monitoring and maintenance.This brief review explores the detection and analysis of damage in wind turbine blades.The study highlights various techniques,including acoustic emission analysis,strain signal monitoring,and vibration analysis,as effective approaches for damage detection.Vibration analysis,in particular,shows promise for fault identification by analyzing changes in dynamic characteristics.Damage indices based on modal properties,such as natural frequencies,mode shapes,and curvature,are discussed.

Determination of wax pattern die profile for investment casting of turbine blades

In order to conform to dimensional tolerances, an efficient numerical method, displacement iterative compensation method, based on finite element methodology （FEM） was presented for the wax pattern die profile design of turbine blades. Casting shrinkages at different positions of the blade which was considered nonlinear thermo-mechanical casting deformations were calculated. Based on the displacement iterative compensation method proposed, the optimized wax pattern die profile can be established. For a A356 alloy blade, substantial reduction in dimensional and shape tolerances was achieved with the developed die shape optimization system. Numerical simulation result obtained by the proposed method shows a good agreement with the result measured experimentally. After four times iterations, compared with the CAD model of turbine blade, the total form error decreases to 0.001 978 mm from the orevious 0.515 815 mm.

Influence of Surface Ice Roughness on the Aerodynamic Performance of Wind Turbines

The focus of this research was on the equivalent particle roughness height correction required to account for the presence of ice when determining the performances of wind turbines.In particular,two icing processes(frost ice and clear ice)were examined by combining the FENSAP-ICE and FLUENT analysis tools.The ice type on the blade surfaces was predicted by using a multi-time step method.Accordingly,the influence of variations in icing shape and ice surface roughness on the aerodynamic performance of blades during frost ice formation or clear ice formation was investigated.The results indicate that differences in blade surface roughness and heat flux lead to disparities in both ice formation rate and shape between frost ice and clear ice.Clear ice has a greater impact on aerodynamics compared to frost ice,while frost ice is significantly influenced by the roughness of its icy surface.

Optimization of a Pipeline-Type Savonius Hydraulic Turbine

This study focuses on a DN50 pipeline-type Savonius hydraulic turbine.The torque variation of the turbine in a rotation cycle is analyzed theoretically in the framework of the plane potential flow theory.Related numerical simulations show that the change in turbine torque is consistent with the theoretical analysis,with the main power zone and the secondary power zone exhibiting a positive torque.In contrast,the primary resistance zone and the secondary resistance zone are characterized by a negative torque.Analytical relationships between the turbine’s internal flow angleθ,the deflector’s inclination angleα0,and the coverage angleαof the power zone are introduced,and a method for calculating the optimal number of blades is proposed to maximize the power zone.Results are presented about performance tests conducted on five groups of hydraulic turbines with the blade number ranging from 3 to 7.Such results indicate that both the turbine’s recovery power and efficiency attain the highest values when the blade number is 4,which is in agreement with the number of blades calculated by the proposed method.Additionally,the study examines the effects of the flow rate on turbine parameters and the projected energy generation and cost savings for a specific pipeline configuration.

Analysis of the Influence of the Blade Deformation on Wind Turbine Output Power in the Framework of a Bidirectional Fluid-Structure Interaction Model

The blades of large-scale wind turbines can obviously deform during operation,and such a deformation can affect the wind turbine’s output power to a certain extent.In order to shed some light on this phenomenon,for which limited information is available in the literature,a bidirectional fluid-structure interaction(FSI)numerical model is employed in this work.In particular,a 5 MW large-scale wind turbine designed by the National Renewable Energy Laboratory(NREL)of the United States is considered as a testbed.The research results show that blades’deformation can increase the wind turbine’s output power by 135 kW at rated working conditions.Compared with the outcomes of the simulations conducted using the model with no blade deformation,the results obtained with the FSI model are closer to the experimental data.It is concluded that the bidirectional FSI model can replicate the working conditions of wind turbines with great fidelity,thereby providing an effective method for wind turbine design and optimization.

Simulation of Offshore Wind Turbine Blade Docking Based on the Stewart Platform

The windy environment is the main cause affecting the efficiency of offshore wind turbine installation.In order to improve the stability and efficiency of single-blade installation of offshore wind turbines under high wind speed conditions,the Stewart platform is used as an auxiliary tool to help dock the wind turbine blade in this paper.In order to verify the effectiveness of the Stewart platform for blade docking,a blade docking simulation system consisting of the Stewart platform,wind turbine blade,and wind load calculation module was built based on Simulink/SimscapeMultibody.At the same time,the PID algorithm is used to control the Stewart platform so that the blade can effectively track the desired trajectory during the docking process to ensure the successful docking of the blade.Through the simulation of the docking process for blades with a length of 61.5 meters,this paper successfully demonstrates a docking system that might facilitate future docking processes.It also shows that the Stewart platform can effectively reduce the vibration and the movement range of the blade root and improve the stability and efficiency of blade docking.

Research on the Follow-Up Control Strategy of Biaxial Fatigue Test of Wind Turbine Blade Based on Electromagnetic Excitation

Aiming at the drift problem that the tracking control of the actual load relative to the target load during the electromagnetic excitation biaxial fatigue test of wind turbine blades is easy to drift,a biaxial fatigue testingmachine for electromagnetic excitation is designed,and the following strategy of the actual load and the target load is studied.A Fast Transversal Recursive Least Squares algorithm based on fuzzy logic(Fuzzy FTRLS)is proposed to develop a fatigue loading following dynamic strategy,which adjusts the forgetting factor in the algorithmthrough fuzzy logic to overcome the contradiction between convergence accuracy and convergence speed and solve the phenomenon of amplitude overshoot and phase lag of the actual load relative to the target load.Combined with the previous research results,a simulation model was constructed to verify the strategy’s effectiveness.Field tests were carried out to verify its follow-up effect.The results showthat the tracking error of flapwise and edgewise direction iswithin 4%,which has better robustness and dynamic and static performance than the traditional Recursive Least Squares(RLS)algorithm.

Convergence Analysis of the Numerical Solution for Cathode Design of Aero-engine Blades in Electrochemical Machining

As a main difficult problem encountered in electrochemical machining （ECM）, the cathode design is tackled, at present, with various numerical analysis methods such as finite difference, finite element and boundary element methods. Among them, the finite element method presents more flexibility to deal with the irregularly shaped workpieces. However, it is very difficult to ensure the convergence of finite element numerical approach. This paper proposes an accurate model and a finite element numerical approach of cathode design based on the potential distribution in inter-electrode gap. In order to ensure the convergence of finite element numerical approach and increase the accuracy in cathode design, the cathode shape should be iterated to eliminate the design errors in computational process. Several experiments are conducted to verify the machining accuracy of the designed cathode. The experimental results have proven perfect convergence and good computing accuracy of the proposed finite element numerical approach by the high surface quality and dimensional accuracy of the machined blades.

Videometric research on deformation measurement of large-scale wind turbine blades

Utilization of wind energy is a promising way to generate power,and wind turbine blades play a key role in collecting the wind energy effectively.This paper attempts to measure the deformation parameter of wind turbine blades in mechanics experiments using a videometric method. In view that the blades experience small buckling deformation and large integral deformation simultaneously, we proposed a parallel network measurement(PNM) method including the key techniques such as camera network construction,camera calibration,distortion correction,the semi-automatic high-precision extraction of targets,coordinate systems unification,and bundle adjustment,etc. The relatively convenient construction method of the measuring system can provide an abundant measuring content,a wide measuring range and post processing.The experimental results show that the accuracy of the integral deformation measurement is higher than 0.5 mm and that of the buckling deformation measurement higher than 0.1mm.

Hashin Failure Theory Based Damage Assessment Methodology of Composite Tidal Turbine Blades and Implications for the Blade Design

A damage assessment methodology based on the Hashin failure theory for glass fiber reinforced polymer(GFRP)composite blade is proposed. The typical failure mechanisms including the fiber tension/compression and matrix tension/compression are considered to describe the damage behaviors. To give the flapwise and edgewise loading along the blade span, the Blade Element Momentum Theory(BEMT) is adopted. In conjunction with the hydrodynamic analysis, the structural analysis of the composite blade is cooperatively performed with the Hashin damage model. The damage characteristics of the composite blade, under normal and extreme operational conditions,are comparatively analyzed. Numerical results demonstrate that the matrix tension damage is the most significant failure mode which occurs in the mid-span of the blade. The blade internal configurations including the box-beam, Ibeam, left-C beam and right-C beam are compared and analyzed. The GFRP and carbon fiber reinforced polymer(CFRP) are considered and combined. Numerical results show that the I-beam is the best structural type. The structural performance of composite tidal turbine blades could be improved by combining the GFRP and CFRP structure considering the damage and cost-effectiveness synthetically.

Numerical simulation of cavitation turbulence in Francis turbine runner with splitter blades

Cavitation will reduce the turbine performance and even damage the turbine components.To verify the effects of splitter blades on improving the cavitation performance,the cavitation flow inside a Francis turbine runner with splitter blades was numerically simulated by using the Singhal cavitation model and the standard k-ε turbulence model.The distributions of static pressure and gas volume fractions on the surface of the runner blades were predicated under different conditions,and the cavitation in the flow field of the runner was analyzed.The results show that the static pressure and gas volume fractions are more uniformly distributed on the short blades than those on the long blades in Francis turbines with splitter blades,and there is almost no cavitation on the short blades;their distributions are more uniform under small flow conditions than those under large flow conditions;and large gas volume fractions are concentrated at the outlet tip near the band on the suction side of the long blade.The installation of splitter blades can improve the cavitation performance of conventional Francis turbines.

Geometric analysis of investment casting turbine blades based on digital measurement data

A turbine blade is one of the key components of the aero-engine. Its geometric shape should be inspected carefully in the production stage to ensure that it meets the tolerance specification. In the present paper, an approach for investment turbine blade geometric shape analysis based on multi-source digital measurement is presented. Its key technologies, such as measurement data collection, blade model reliable alignment, geometric shape deviation fast calculation and visualization, were investigated. Actual measurement data from a structure light measurement device and a Coordinate Measuring Machine(CMM) for turbine blades were used to validate the presented method. The experimental results show that the proposed method is accurate, quick and effective to implement.