Blade Model Research Articles

Dynamic instability and internal resonance of rotating pretwisted composite airfoil blades

A rotating pretwisted airfoil blade model reinforced with graphene platelets combined with first-order shear deformation theory is developed to study dynamic instability and internal resonance of the rotating blade, which subjected to the transverse load and in-plane load. Based on the mode shapes derived by using Rayleigh-Ritz method, Lagrange's formulation is taken into account to acquire nonlinear ordinary differential equations. The critical buckling loads and instability regions are obtained and then compared with the opening results. Then, the method of multiple scales is taken into account to solve the modulation equations of the rotating airfoil blade in the presence of 1:2 internal resonance. The detailed discussions related to frequency-response and force-response curves under different parameters are carried out.

Experimental and numerical full-field displacement and strain characterization of wind turbine blade using a 3D Scanning Laser Doppler Vibrometer

Full-field dynamic measurement is desirable and useful for many purposes including model validation, or experimental characterization of test articles for which a finite element model is not available. Surface full-field strain measurement and test-model correlation have been performed on a small-size isotropic structure with a non-contacting 3D Scanning Laser Doppler Vibrometer (SLDV), which has an advantage over strain gauge tests with measurements at only a few discrete points. However, the application on large-size anisotropic structures has not been explored. This is the first work using the 3D SLDV for measuring the full-field displacement and strain Operational Deflection Shapes (ODSs) of a large composite structure, a 4.2-meter wind turbine blade. The displacement and strain measurement results are also correlated to the corresponding predictions of the blade composite finite element model in both a visual and quantified manner. The correlation is demonstrated for both low-frequency fundamental modes, but also for complex, highly-coupled high-frequency modes, which is challenging for other optical methods. Correlation results show a high degree of agreement between measured and numerically predicted displacements and strains, demonstrating the validity of the 3D SLDV measurement and the developed finite element model of the composite blade. The strain shapes are also compared with the displacement shapes and the blade structural configuration to reveal the effect of the blade structure on the strain distribution. The full-field displacement and strain identified and the proposed measurement and correlation technique would benefit wind turbine blade designers by providing new experimental tools to evaluate blade structural performance and reliability and provides a useful reference for blade structural designers.

Prediction on aeroengine blade foreign object damage validated by air gun tests

Aeroengine in service was prone to ingest foreign objects, leading to foreign object damage (FOD) and failure accidents of the blades. In this paper, laboratory FOD tests were firstly conducted on TC4 and AM355 steel simulated airfoil specimens impacted by 3 mm diameter projectile at a speed of 350 m/s, and numerically reproduced using Johnson-Cook (J-C) model with failure criterion. A penetrating-type notch (P-notch) with severe material loss was observed, and a good agreement between experiments and finite element (FE) predictions could be found for both notch morphology and size. The influence of impact velocity on FOD and the FOD-induced residual stress were investigated by the proposed FE model. High tensile stress was observed along the notch edge, while the bottom of notch was mainly dominated by compressive stress. Finally, a FE model of aeroengine blade considering the initial centrifugal force was developed, and the influences of FOD to compressor blade on its modal properties were discussed. Compared to the normal blade, the damage induced a deviation in frequency within 1 %.

Multiple limit cycle amplitudes in high-fidelity predictions of standstill wind turbine blade vibrations

Abstract. In this study, vortex-induced vibrations (VIVs) on the IEA 10 MW blade are investigated using two methodologies in order to assess strengths and weaknesses of the two simulation types. Both fully coupled fluid–structure interaction (FSI) simulations and computational fluid dynamics (CFD) with forced motion of the blade are used and compared. It is found that for the studied cases with high inclination angles, the forced-motion simulations succeed in capturing the power injection by the aerodynamics, despite the motion being simplified. From the fully coupled simulations, a dependency on initial conditions of the vibrations was found, showing that cases which are stable if unperturbed might go into large VIVs if provoked initially by, for instance, inflow turbulence or turbine operations. Depending on the initial vibration amplitudes, multiple limit cycle levels can be triggered, for the same flow case, due to the non-linearity of the aerodynamics. By fitting a simple damping model for the specific blade and mode shape from FSI simulations, it is also demonstrated that the equilibrium limit cycle amplitudes between power injection and dissipation can be estimated using forced-motion simulations, even for the multiple stable vibration cases, with good agreement with fully coupled simulations. Finally, a time series generation from forced-motion simulations and the simple damping model is presented, concluding that CFD amplitude sweeps can estimate not only the final limit cycle oscillation amplitude, but also the vibration build-up time series.

REKONSTRUKSI SUDU PRIMARY AIR FAN PLTU MENGGUNAKAN STANDAR NACA

This PA Fan is one of the vital components in the generating system that functions to drain air and carry fuel (coal) from the pulverizer to the boiler burner. The research has a focus on designing methods to reconstruct the blades in order to increase independence to maintain the reliability of turbo engine equipment. Damage to axial turbo engine equipment generally occurs as a defect in the blades. The method of self-constructing blades needs to be carried out to increase the speed of the repair process. The limitation in this study is that the blade airfoil profile is adjusted to the standards of the National Advisory Committee for Aeronautics (NACA). The benefit of the PA Fan blade reconstruction process is to find the technology of the PA Fan blade product and the basic concepts of the product design process as desired by the initial maker (design intent). The research methods used include: Measurement and geometric modeling of the PA Fan blade using the Mitutoyo Cyrsta-Apex S9106 Coordinate Measuring Machine which is connected to a non-contact laser scanner Mitutoyo Surface Measure 606 to obtain a collection of many coordinates of the measurement results (point clouds), then process point clouds processing to obtain a 3D model of the measurement results, after that identify the airfoil with the NACA standard, and the final stage is to process machine drawings of complete components with geometry specifications.

Stability analysis of periodic solutions computed for blade-tip/casing contact problems

This article focuses on the stability assessment of mechanical systems featuring a nonlinear interface on which are applied unilateral contact constraints. The regularized-Lanczos harmonic balance method is used to compute periodic solutions for each system. For each considered mechanical system, the implementation of distinct stability assessment numerical algorithms (including the Newmark 2 n -pass method and Hill’s method using eigenvalue sorting) relying on Floquet theory allows for an in-depth investigation of their convergence and accuracy. From a single-degree of freedom impactor impacting a fixed obstacle to the industrial finite element model of a transonic compressor blade impacting a deformed casing, the gradually increasing complexity of the considered mechanical systems provides new insight on which stability assessment numerical algorithm may be the best suited when dealing with contact nonlinearities. From a numerical standpoint, attention is paid to specific developments that were identified as key for enhancing the numerical efficiency of the stability assessment process including the iterative solver, the computation of analytical derivatives, the scaling of the problem and the use of fast Fourier transforms. Particular attention is also paid to the influence of the Lanczos filtering procedure and its implications in terms of stability assessment. While it is found that both the Newmark 2 n -pass method and Hill’s method with eigenvalue sorting can be successfully applied on large industrial systems featuring a nonlinear interface, the faster convergence of Hill’s method is underlined and suggests it may be a better option for an accurate and efficient stability assessment on which Lanczos filtering has a negligible influence. • Local stability analysis of periodic solutions computed using a Harmonic Balance Method. (HBM) based numerical strategy for contact problems of increasing severity. • Analytical expression of blade-tip/casing contact forces related Jacobian matrices. • Numerical considerations for efficient HBM computations and in-depth comparison of time and frequency domain-based stability assessment algorithms. • Detailed application on both academical impactors and an industrial blade: NASA rotor 37. • Influence of Lanczos filtering over stability assessment.

DESIGN AND ANALYSIS OF COMPOSITE PROPELLER BLADE FOR AIRCRAFT

The work in this paper primarily focuses on the modelling and analysis of a plane's propeller blade for strength. The geometry of a propeller blade is a sophisticated 3D model. CATIA V5 R20 is utilised to generate the blade model, which necessitates the usage of high-end modelling CAD software. This document provides a brief overview of Fiber Reinforced Plastic materials as well as the benefits of employing composite propellers over traditional metallic propeller blades. The purpose of this research is to use finite element analysis to analyse the metal and composite strength of the propeller blade. We conducted static and modal analysis for isotropic materials using ANSYS software, as well as linear layer analysis for orthotropic materials. FEA methods were used to investigate two distinct types of propellers, namely aluminium, E-glass, and carbon fibre.

Developing an Extended Virtual Blade Model for Efficient Numerical Modeling of Wind and Tidal Farms

Harnessing renewable and clean energy resources from winds and tides are promising technologies to alter the high level of consumption of traditional energy resources because of their great global potential. In this regard, developing farms with multiple energy converters is of great interest due to the skyrocketing demand for sustainable energy resources. However, the numerical simulation of these farms during the planning phase might pose challenges, the most significant of which is the computational cost. One of the most well-known approaches to resolve this concern is to use the virtual blade model (VBM). VBM is the implementation of the blade element model (BEM). This was done by coupling the blade element momentum theory equations to simulate rotor operation with the Reynolds averaged Navier–Stokes (RANS) equation to simulate rotor wake and the turbulent flow field around it. The exclusion of the actual geometry of blades enables a lower computational cost. Additionally, due to simplifications in the meshing procedure, VBM is easier to set up than the models that consider the actual geometry of blades. One of the main unaddressed limitations of the VBM code is the constraint of modeling up to 10 renewable energy converters within one computational domain. This paper provides a detailed and well-documented general methodology to develop a virtual blade model for the simulation of 10-plus converters within one computational domain to remove the limitation of this widely used and robust code. The extended code is validated for both the single- and multi-converter scenarios. It is strongly believed that the technical contribution of this paper, combined with the current advancement of available computational resources and hardware, can open the gates to simulate farms with any desired number of wind or tidal energy converters, and, accordingly, secure the sustainability and feasibility of clean energies.

A novel damage identification method for flue gas turbine blades based on tip timing

Tip timing signal analysis has been applied to the online condition monitoring of high-speed blades. However, traditional tip timing analysis methods are not suitable for low-speed flue gas turbines. Therefore, this paper proposes a novel blade tip timing signal analysis method based on an investigation of the dynamic response characteristics of low-speed blades. First, the finite element modal theory is introduced to analyze the characteristics of blade damage. Second, an equivalent cantilever beam analysis model of flue gas turbine blades is established under complex environment and working conditions. In order to monitor the variation of local stiffness, a damage identification method based on the variation of the free end deflection of the equivalent cantilever beam is proposed. Finally, a rotating blade tip timing monitoring testing rig is established to verify the feasibility of the proposed method. The results show that the cracks originating at about 80% of the blade height have the greatest influence on blade stiffness, followed by blade root. The calculated blade damage parameters are 4.8464 mm and 3.7588 mm, and the crack influencing factors are 4.7476 and 3.6822, respectively, indicating that the change trend is consistent with the blade damage rules.

Aerodynamic design considerations for supercritical CO[formula omitted] centrifugal compressor with real-gas effects

The optimal supercritical carbon dioxide (SCO2) Brayton cycle requires the SCO2 compressor to operate near the critical point, where strong real-gas effects make the aerodynamic design much more challenging. Conventional semi-empirical aerodynamic design guidelines developed for air compressors are no longer applicable because CO2 flows undergo significant changes in thermophysical properties when inlet conditions of the SCO2 compressor change, when different design parameters are chosen, and when the phase change occurs. This paper proposed a set of new design guidelines for SCO2 compressors from zero-dimensional (0D), one-dimensional (1D), and three-dimensional (3D) perspectives. At 0D level, the concept of similitude is introduced to derive new performance correlations independent of inlet conditions. At 1D level, the coupling effect of thermophysical properties and design parameters is considered and new guidelines for preliminary design are proposed. At 3D level, detailed blade modeling procedures are discussed in order to improve compressor performance and suppress phase changes. All these design considerations are validated by redesigning and comparing several well-designed SCO2 compressors from open literature. The results show that for the compressor operating near the pseudo-critical line, an efficiency increment of about 0.7% can be obtained by adopting the proposed design considerations, while phase change can also be well suppressed at the same time.

Study on the repair parameters for trailing‐edge bonding failure of wind turbine blade in service

AbstractA numerical analysis method of trailing edge deboning is proposed in this paper. Using this method, multiple repair parameters can be quantified by analyzing aerodynamic responses and structural characteristics of the trailing edge. This method can be applied to three types of trailing edge, including blunt trailing edge, transitional trailing edge, and pointed trailing edge. In this study, the repair parameters are divided into two types, including the internal parameters that can affect the bonding strength and the external parameters that can affect the stiffness and aerodynamic shape. The main research steps are as follows: First, a repair structure shell‐body model was developed. Second, static tensile tests were carried out using 49 specimens, covering two lap joint types and seven bonding thicknesses. Finally, nine different repaired trailing edge models were developed using Ansys/Fluent for each two two‐dimensional airfoil. A 30–40 m section of a 71 m blade was used to develop a three‐dimensional (3D) rotating model with the repaired trailing edge. The simulation results show that the two internal parameters, overlap length and the slope of adhesive joints, are the key to improving the bonding performance of the pointed trailing edge. In addition, the bonding thickness range of 1–10 mm is proved by the experiment results and numerical analysis to be sufficient for good bonding performance. Besides this, the influence of the repair height on the aerodynamic pressure distribution and lift coefficient is much greater than the repair width, and the torque and power of the repaired 3D blade model are 1.91% higher than that of the original blade. This should further help provide an effective theoretical basis for determining the repair plan for a wind turbine blade.

Performance Analysis of PLA Material Based Micro-Turbines for Low Wind Speed Applications.

Various studies have been conducted in recent years to find solutions to the issues in wind energy conversion systems. A 100W horizontal axis micro wind turbine is built for low wind speed applications in this work. The Blade Element Momentum theory approach was used to design the 100W micro wind turbine blade. The wind turbine blade 3D model was created using the CREO CAD 3.0 software. Based on the aerodynamic studies, the airfoil S9000 is chosen among others for generating high power at low wind speed. The density, Young’s modulus, and the Poisson ratio of the proposed wind turbine blade model with acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) materials were compared. ABS and PLA materials were investigated using a 0.33 mm layer of infill ranging from 10% to 100%. PLA and ABS output values were compared in terms of deformation, equivalent stress, and equivalent strain. PLA materials, on the other hand, have less deformation and greater structural properties than ABS materials. The wind blade structural analysis was performed in ANSYS 15 software, and the details of experimental and simulated results are presented in this paper.

Construction of damage-free digital twin of damaged aero-engine blades for repair volume generation in remanufacturing

Accurate repair volume generation from 3D scan data of damaged aero-engine blades is of great importance in additive or hybrid remanufacturing for restoring the blades to a like-new condition. In addition to material-missing damages, the blade's surface also deforms due to working in harsh environments, which makes it deviate from the nominal design geometry. Therefore, the Boolean operation between the nominal CAD model and the scanned point cloud of the damaged blade does not yield an accurate repair volume. This paper presents a new methodology to construct an accurate damage-free digital twin model of the defective blades that contains the deformations of the blade's undamaged regions. The Boolean difference between the scan data of the damaged blade and its damage-free digital twin yields the repair volume with a smooth geometric transition at the interface of the repair patch and unrepaired regions. At first, the data points of damaged regions of the blade surface are detected and eliminated from the scan through a region growing segmentation. Then, a CAD-to-scan non-rigid registration algorithm deforms the nominal CAD model of the blade to best match it to the scanned point cloud in the undamaged regions. The non-rigid registration algorithm iteratively minimizes the distance between two datasets under the local rigidity constraint to avoid shrinkage and expansion of the deformed CAD model. A constrained point-to-surface weighted correspondence search method is proposed to reduce the influence of noise and unreliable correspondences on the non-rigid registration. The results of numerical and experimental case studies have demonstrated that the proposed method is accurate and robust to noise, and it can be effectively applied to construct a damage-free digital twin model for repair volume generation.

The Optimal Blading Design and CFD Analysis of Axial Flow Fan

This study proposes a method to optimize the blade angle and chord length distributions of axial flow fan rotor blade, and applied it to the design of the actual industrial axial flow fan. The present design model of the axial flow fan rotor blade is to construct and stack the section profiles using single circular arc and airfoil thickness distribution with the camber and stagger angles as design variables along the blade span height from hub to tip, and the chord length distribution is designed in a parabolic fashion from hub to tip. The performance and efficiency of the fan rotor blades are predicted by applying a through-flow analysis method to the 3D fan blade geometry obtained from the design variables of the camber angle, stagger angle, and chord length of the blade sections. These fan design and through-flow analysis methods are used as the simulation engine for optimization problem. Through applying the optimization algorithm, an optimal axial flow fan rotor is obtained with maximum efficiency and computational fluid dynamics analysis is performed to verify the result of the present optimal design. From the computational fluid dynamics calculation results, it can be seen that the present optimal design model has an efficiency improvement of about 2% compared to the initial design, and maintains relatively high efficiency even under partial load conditions.

DETERMINATION OF THE FEATURES OF THE SHAPE AND VIBRATION FREQUENCY OF TURBINE BLADES ON DIGITAL MODELS

A digital solid model of a turbine blade with a mounting shelf has been developed in SolidWorks. The description of complex surfaces is made using spline functions. The method of computer simulation using SolidWorks Simulation was used to study the distribution of natural oscillations of the blade depending on the method of its fixing during machining. The spectra of natural oscillations of the blade in the sound range have been obtained and analyzed. The form of natural vibrations of complex surfaces is also analyzed. For the correct choice of processing parameters during machining, it is necessary to take into account both the conditions for fixing the part in the fixture and the natural frequency of the part. It is noted that an equally important parameter is the form of oscillations of a thin surface at the studied frequencies. It is noted that in the future it is possible to solve these problems through computer simulation.

Optimal Rotary Wind Turbine Blade Modeling with Bond Graph Approach for Specific Local Sites

The wind turbine blade is an important component for harnessing wind energy. It plays a vital role in wind turbine operation. In this work, a study was conducted to investigate the dynamic behavior of an optimal rotary wind turbine blade with a bond graph approach simulated with MATLAB/Simulink. The model is considered as a twisted Rayleigh beam which is made of several sections of the type SG6043 airfoil. This type of airfoil is suitable for low wind conditions, and each section is subjected to aerodynamic loads that are computed using the blade element momentum theory. The bond graph model was developed based on the law of conservation of mass and energy in the systems, and then the model was converted to the MATLAB/Simulink toolbox; results were validated with SG6043 airfoil data and real wind data collected from selected specific sites of Abomsa, Metehara, and Ziway areas in Ethiopia.

An examination of hub wind turbine utilizing fluid-structure interaction strategy

A compromise approach between aerodynamic performance and structural robustness is presented. The modeling of horizontal axis wind turbine blade GE1.5-XLE is studied regarding the applicability of three different solution methods computational fluid dynamics (CFD), one – way (unidirectional), and two – way (bidirectional) coupling fluid – structure interaction (FSI) at a shedding frequency of the vortex far from the natural frequency. The predicted results showed significant differences between the unidirectional coupling solution and experimental data. While, the bidirectional coupling method proposed accurate FSI and gave results closer to the experimental measurements than unidirectional simulation results. The bidirectional coupled approach appears to be more stable and accurate, where a large number of time steps should be used for uncoupled method to achieve the same level of precision. For the present case involving large blade strain, the difference between the prediction of rigid blade solution using CFD and FSI model increases considerably. However, it is concluded that for large blade strains, the FSI model is closer shown to be more adequate for accurate representation of the turbine performance. Moreover, when optimization is a key aspect, bidirectional simulations should be performed regardless of the higher computational cost.

CFD Modeling of Wind Turbine Blades with Eroded Leading Edge

The present work compares 2D and 3D CFD modeling of wind turbine blades to define reduced-order models of eroded leading edge arrangements. In particular, following an extensive validation campaign of the adopted numerical models, an initially qualitative comparison is carried out on the 2D and 3D flow fields by looking at turbulent kinetic energy color maps. Promising similarities push the analysis to consequent quantitative comparisons. Thus, the differences and shared points between pressure, friction coefficients, and polar diagrams of the 3D blade and the simplified eroded 2D setup are highlighted. The analysis revealed that the inviscid characteristics of the system (i.e., pressure field and lift coefficients) are precisely described by the reduced-order 2D setup. On the other hand, discrepancies in the wall friction and the drag coefficients are systematically observed with the 2D model consistently underestimating the drag contribution by around 17% and triggering flow separation over different streamwise locations. Nevertheless, the proposed 2D model is very accurate in dealing with the more significant aerodynamics performance of the blade and 30 times faster than the 3D assessment in providing the same information. Therefore the proposed 2D CFD setup is of fundamental importance for use in a digital twin of any physical wind turbine with the aim of carefully and accurately planning maintenance, also accounting for leading edge erosion.

Effects of centrifugal stiffening and spin softening on nonlinear modal characteristics of cyclic blades with impact–friction coupling

This paper aims to interpret the coupling modal properties of cyclic blades under impact–friction interactions and their evolution mechanism versus operating points. Therefore, a coupling analytical model of cyclic blades is developed based on a Lagrange method and the assumed mode method (AMM), after considering centrifugal stiffening, spin softening, stagger angle, and twist angle. Then a mixed modal analysis method (MMAM) for this analytical model is extended by combining the extended periodic motion concept (EPMC) with AMM. Wherein a classic alternating frequency/time method (AFT) and the continuation method are employed to overcome the numerical divergence problem. Then damped nonlinear normal modes (dNNMs), including eigenfrequencies, modal damping ratios, and mode shapes, of the coupling system with shroud joints are finally computed and discussed under different excitation levels and contact conditions through a modal synthesis algorithm. After that, the influence laws of centrifugal stiffening and spin softening on the dNNMs are explored to reveal its evolution mechanism versus operation speeds. Finally, the Campbell diagrams of dNNMs are successfully obtained to discuss the effects of the impact–friction coupling on critical speeds (CSs) of the shrouded blades system.

Nonharmonic Control of the Blade-Vortex Interaction Noise of Electrically Controlled Rotor

Electrically controlled rotor, also known as swashplateless rotor, represents an active rotor system that, due to the use of a trailing edge flap system instead of a swashplate, not only enables primary control but also conveniently reduces the blade-vortex interaction (BVI) noise of the rotors through active control. The effect of nonharmonic inputs on the control of the BVI noise of electrically controlled rotors based on their unique trailing edge flap systems has been investigated in this paper. To this end, an analytical model for the vortex interaction-induced load and noise of electrically controlled rotor is first established based on the viscous vortex particle method, the Weissinger-L blade model, and the Ffowcs Williams-Hawkings (FW-H) equation. On this basis, a simulation study of flap nonharmonic control for BVI noise reduction in electrically controlled rotors is carried out. According to the mechanism of the BVI in electrically controlled rotors, the second quadrant flap nonharmonic control is used to reduce the advancing side BVI noise, and the effects of different control waveforms and amplitudes on the peak value and directivity of the BVI noise of the sample electrically controlled rotors are analyzed to reveal the noise reduction mechanism of flap nonharmonic control. Subsequently, the effect of the third quadrant flap nonharmonic control on BVI noise on the retreating side of the sample electrically controlled rotors is investigated. The results show that flap nonharmonic control has little effect on miss distance and that it controls BVI noise mainly by reducing the wake vortex strength on the advancing and retreating sides, which may lead to an increase in rotor noise in other regions; the noise reduction effect of flap nonharmonic control for different blade preindex angles indicates that suitable preindex angles coupled with flap nonharmonic control help optimally reduce noise.