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Blade element rotor theory
\"Blade Element Rotor Theory presents an extension of the blade element rotor theory to describe the dynamic properties of helicopter rotors. It focuses on the more precise mathematical determination of the forces and moments by which a rotor affects its rotorcraft at specified flight conditions and control positions. The book is intended for graduate students and researchers studying rotor dynamics and helicopter flight dynamics. Analyzing the impact of non-uniform blade parameters, the book covers blade twisting, non-rectangular planform shape of a blade, and inhomogeneous airfoil along a blade\"-- Provided by publisher.
Book
Advances in Wind Turbine Blade Design and Materials
Wind energy is gaining critical ground in the area of renewable energy, with wind energy being predicted to provide up to 8% of the worlds consumption of electricity by 2021. This book reviews the design and functionality of wind turbine rotor blades as well as the requirements and challenges for composite materials used in both current and future designs of wind turbine blades. Part one outlines the challenges and developments in wind turbine blade design, including aerodynamic and aeroelastic design features, fatigue loads on wind turbine blades, and characteristics of wind turbine blade airfoils. Part two discusses the fatigue behavior of composite wind turbine blades, including the micromechanical modelling and fatigue life prediction of wind turbine blade composite materials, and the effects of resin and reinforcement variations on the fatigue resistance of wind turbine blades. The final part of the book describes advances in wind turbine blade materials, development and testing, including biobased composites, surface protection and coatings, structural performance testing and the design, manufacture and testing of small wind turbine blades This book offers a comprehensive review of the recent advances and challenges encountered in wind turbine blade materials and design, and will provide an invaluable reference for researchers and innovators in the field of wind energy production, including materials scientists and engineers, wind turbine blade manufacturers and maintenance technicians, scientists, researchers and academics.
eBook
Solid Particle Erosion Behaviour and Protective Coatings for Gas Turbine Compressor Blades—A Review
Gas turbines (GTEs) are often utilised in harsh environments where the GT components, including compressor vanes and rotor blades, are subject to erosion damage by sand and dust particles. For instance, in a desert environment, the rate of damage made by solid particles erosion (SPE) becomes severe, and therefore results in degradation to the GTE parts, lowering the cycle efficiency, reducing the device lifetime, and increasing the overall cost of the operation. As such, understanding the erosion mechanism caused by solid particles and the effects associated with it is crucial for selecting the appropriate countermeasures and maintaining the system performance. This review paper provides a survey of the available studies on SPE effects on GTEs and surface protective coatings. Firstly, the ductile and brittle SPE mechanism is presented, as well as the ductile-brittle transition region. Then, an in-depth focus on the parameters associated with the SPE, such as particles properties and impingement conditions, is introduced. Furthermore, the existing theoretical models are shown and discussed. Afterwards, erosion resistant coating materials for surface protection and their selection criteria are covered in the review. Finally, the gap in knowledge and future research direction in the field of SPE on GTEs are provided.
Journal Article
Steady Flow Over a Finite Patch of Submerged Flexible Vegetation
An immersed boundary‐finite element with soft‐body dynamics has been implemented to study steady flow over a finite patch of submerged flexible aquatic vegetation. The flow structure interaction model can resolve the flow interactions with flexible vegetation, and hence the reconfiguration of vegetation blades to ambient flow. Flow dynamics strongly depend on two dimensionless parameters, namely vegetation density and Cauchy number (defined as the ratio of the fluid drag force to the elastic force). Five different flow patterns have been identified based on vegetation density and Cauchy number, including the limited reach, swaying, “monami” A, “monami” B with slow moving interfacial wave, and prone. The “monami” B pattern occurred at high vegetation density and is different from “monami” A, in which the passage of Kelvin‐Helmholtz billows strongly affects the vegetation interface. With soft‐body dynamics, blade‐to‐blade interactions can also be resolved. At high vegetation density, the hydrodynamic interactions play an important role in blade‐to‐blade interactions, where adjacent vegetation blades interact via the interstitial fluid pressure. At low vegetation density, direct contacts among vegetation blades play important roles in preventing unphysical penetration of vegetation blades. Key Points A flow‐structure interaction model has been developed with direct blade‐to‐blade interactions The hydrodynamic interactions among vegetation blades play an important role Five distinct flow regimes have been identified based on Cauchy number and vegetation density
Journal Article
Model updating of wind turbine blade cross sections with invertible neural networks
Fabricated wind turbine blades have unavoidable deviations from their designs due to imperfections in the manufacturing processes. Model updating is a common approach to enhance model predictions and therefore improve the numerical blade design accuracy compared to the built blade. An updated model can provide a basis for a digital twin of the rotor blade including the manufacturing deviations. Classical optimization algorithms, most often combined with reduced order or surrogate models, represent the state of the art in structural model updating. However, these deterministic methods suffer from high computational costs and a missing probabilistic evaluation. This feasibility study approaches the model updating task by inverting the model through the application of invertible neural networks, which allow for inferring a posterior distribution of the input parameters from given output parameters, without costly optimization or sampling algorithms. In our use case, rotor blade cross sections are updated to match given cross‐sectional parameters. To this end, a sensitivity analysis of the input (material properties or layup locations) and output parameters (such as stiffness and mass matrix entries) first selects relevant features in advance to then set up and train the invertible neural network. The trained network predicts with outstanding accuracy most of the selected cross‐sectional input parameters for different radial positions; that is, the posterior distribution of these parameters shows a narrow width. At the same time, it identifies some parameters that are hard to recover accurately or contain intrinsic ambiguities. Hence, we demonstrate that invertible neural networks are highly capable for structural model updating.
Journal Article
Research on the influence of the combination of hole shape and Hole compound angle on the temperature field of the actual turbine rotor blade
Using conjugate heat transfer methods, the effects of the combination of hole shapes and hole compound angles on the temperature field of actual turbine blades were studied. Four-hole shapes and three-hole compound angles were set on the GE-E3 1st turbine blades. The results show that changes in compound angles have different effects on blade temperature in different hole shapes, exhibiting distinct characteristics. For the cylinder hole configuration, regardless of whether it is the suction surface or the pressure surface, the compound angle of -45° case has the lowest regional average temperature, with a maximum decrease of 18.7 K. In the console hole configuration, the selection of the hole compound angle needs to consider the mainstream velocity components. This is mainly because in the console hole configuration, the coolant velocity is faster, and when the coolant’s spanwise velocity component is aligned with the mainstream, it reduces the lift of the cooling air. For fan-shaped hole configuration, the case with a compound angle of -45° demonstrates the strongest ability to reduce wall temperature on both the suction surface and pressure surface, with a maximum reduction of 52 K. This is primarily because, in the -45° compound angle case, the coolant not only flows out along the hole but also a small portion flows out from the upper part of the hole, resulting in a larger overall coverage area. For the 7-7-7 shaped hole configuration, the overall trend is similar to that of the fan-shaped hole, especially on the pressure surface, where the -45° compound angle case also shows the strongest ability to reduce wall temperature, achieving a reduction of 44.7 K.
Journal Article
Research on high-cycle vibration fatigue performance test technology of turbine rotor blades
Objective: To investigate the vibration fatigue failure of aero-engine turbine blades under the second-order natural frequency (torsional mode), this study conducts vibration characteristic analysis and research on test methods for the second-order mode. Methods: The blade resonance frequency was identified via a frequency sweep test. Based on the finite element method (FEM), a blade model was established for modal analysis to obtain multi-order modal frequencies and vibration modes, which were verified against test results to determine the blade’s second-order natural frequency. The influence of clamping preload on blade frequency was determined through a torsional gradient test. The installation position of the laser displacement sensor was optimized according to the vibration displacement direction of the target mode. Vibration stress calibration was achieved using synchronous test technology for blade dynamic stress and blade tip vibration displacement. Results: The first two natural frequencies of the blade measured by the frequency sweep test were in good agreement with the FEM simulation results. The simulation further provided the first six modal frequencies and modes. A linear relationship was found between the blade’s vibration stress (σ) and its natural frequency (f) and amplitude (a). Conclusion: The theoretical and measured vibration characteristics of the blade are consistent, and the relationship between the stress under the blade’s second-order natural frequency (torsional mode) and the blade’s natural frequency and amplitude was obtained. This finding confirms the effectiveness of the proposed test method, which can provide fatigue data support for turbine blades.
Journal Article
Investigation on the aerodynamic properties of LM62 blade using blade element momentum theory by DNV/Risø and GH Bladed
The 5.0 MW permanent magnet direct-drive wind turbine generator, with a rated rotational speed of 11.64 rpm, features three (3) LM 62 blades. The turbine blades are suitable for an IEC Class II wind turbine generator. The rotor radius measures 63.7 m with a distance of 1.7 m from the hub centre to the rotor shaft Jlange. An aerodynamic analysis of the LM 62 blade was performed to examine the power output and power coefJicient at wind speeds ranging from 3.0 m/s to 25.0 m/s using the Blade Element Momentum Theory suggested by DNV/Risø and derived from GH Bladed. The blade includes Jive airfoils with a design tip speed ratio of 8.65. Axial and tangential induction factors, lift and drag coefJicients, aerodynamic forces, and torque proJiles as normalized rotor blade length functions were calculated and compared with two BEM models. Discrepancies in the induction factors appear in the inboard section of the blade. The results show that the two BEM models are nearly identical when the upstream wind speed exceeds 11.18 m/s. A Student’s t-test compared the power curves predicted by both BEM models with those from the GH Bladed software. The GH Bladed BEM model had a correlation coefJicient of 0.998 and a t-value of 1.4139, which is below the critical t-value when compared to the GH Bladed software output. This indicates that the power curves are statistically similar with over 95% conJidence. The sound power level of the LM62 blade was found to be 103 dB at rated wind speed.
Journal Article
Vibration-Based Fatigue Analysis of Octet-Truss Lattice Infill Blades for Utilization in Turbine Rotors
Vibration fatigue characteristics are critical for rotating machinery components such as turbine rotor blades. Lattice structures are gaining popularity in engineering applications due to their unique ability to reduce weight and improve the mechanical properties. This study is an experimental investigation of octet-truss lattice structure utilization in turbine rotor blades for weight reduction and to improve vibration fatigue characteristics. One completely solid and three lattice infilled blades with variable strut thickness were manufactured via additive manufacturing. Both free and forced experimental vibration analyses were performed on the blades to investigate their modal and vibration fatigue characteristics. The blades were subjected to random vibration using a vibration shaker. The response was measured using a triaxial accelerometer in terms of vibration acceleration time histories in the X, Y, and Z directions. Results indicate a weight reduction of up to 24.91% and enhancement in the first natural frequency of up to 5.29% were achieved using lattice infilled blades. The fatigue life of the blades was investigated using three frequency domain approaches, namely, Lalanne, Dirlik and narrow band. The fatigue life results indicate that the 0.25 mm lattice blade exhibits the highest fatigue life, while the solid blade exhibits the lowest fatigue life of all four blades. The fatigue life of the 0.25 mm lattice blade was 1822-, 1802-, and 1819- fold higher compared to that of the solid blade, using the Lalanne, Dirlik, and narrow-band approaches, respectively. These results can serve as the first step towards the utilization of lattice structures in turbine blades, with thermal analysis as the next step. Therefore, apart from being light weight, the octet-truss lattice infilled blades exhibited superior vibration fatigue characteristics to vibration loads, thereby making them a potential replacement for solid blades in turbine rotors.
Journal Article