Blade Deformation Research Articles

Study on the optimal elastic modulus of flexible blades for right heart assist device supporting patients with single-ventricle physiologies.

Patients with single-ventricle physiologies continue to experience insufficient circulatory power after undergoing palliative surgeries. This paper proposed a right heart assist device equipped with flexible blades to provide circulatory assistance for these patients. The optimal elastic modulus of the flexible blades was investigated through numerical simulation. A one-way fluid-structure interaction (FSI) simulation was employed to study the deformation of flexible blades during rotation and its impact on device performance. The process began with a computational fluid dynamics (CFD) simulation to calculate the blood pressure rise and the pressure on the blades' surface. Subsequently, these pressure data were exported for finite element analysis (FEA) to compute the deformation of the blades. The fluid domain was then recreated based on the deformed blades' shape. Iterative CFD and FEA simulations were performed until both the blood pressure rise and the blades' shape stabilized. The blood pressure rise, hemolysis risk, and thrombosis risk corresponding to blades with different elastic moduli were exhaustively evaluated to determine the optimal elastic modulus. Except for the case at 8,000 rpm with a blade elastic modulus of 40 MPa, the pressure rise associated with flexible blades within the studied range (rotational speeds of 4,000 rpm and 8,000 rpm, elastic modulus between 10 MPa and 200 MPa) was lower than that of rigid blades. It was observed that the pressure rise corresponding to flexible blades increased as the elastic modulus increased. Additionally, no significant difference was found in the hemolysis risk and thrombus risk between flexible blades of various elastic moduli and rigid blades. Except for one specific case, deformation of the flexible blades within the studied range led to a decrease in the impeller's functionality. Notably, rotational speed had a more significant impact on hemolysis risk and thrombus risk compared to blade deformation. After a comprehensive analysis of blade compressibility, blood pressure rise, hemolysis risk, and thrombus risk, the optimal elastic modulus for the flexible blades was determined to be between 40 MPa and 50 MPa.

Investigation of electrolyte pressure effect on blisk blades during electrochemical machining

PurposeThe purpose of this study is analysis of deformation and vibrations of turbine blades produced by high electrolyte pressure during electrochemical machining.Design/methodology/approachAn experimental setup was designed, experiments were conducted and the obtained results were compared with the finite element results. The deformations were measured according to various flow rates of electrolyte. In finite element calculations, the pressure distribution created by the electrolyte on the blade surface was obtained in the ANSYS® (A finite element analysis software) Fluent software and transferred to the static structural where the deformation analysis was carried out. Three different parameters were examined, namely blade thickness, blade material and electrolyte pressure on blade disk caused by mass flow rate. The deformation results were compared with the gap distances between cathode and anode.FindingsLarge deformations were obtained at the free end of the blade and the most curved part of it. The appropriate pressure values for the electrolyte to be used in the production of blisk blades were proposed numerically. It has been determined that high pressure applications are not suitable for gap distance lower than 0.5 mm.Originality/valueWhen the literature is examined, it is required that the high speed flow of the electrolyte is desired in order to remove the parts that are separated from the anode from the machining area during electrochemical machining. However, the electrolyte flowing at high speeds causes high pressure in the blisk blades, excessive deformation and vibration of the machined part, and as a result, contact of the anode with the cathode. This study provides important findings for smooth electro chemical machining at high electrolyte flows.

The mechanical characteristics and cooling performance of a turbine blade with non-homogeneous lattice structure

The turbine blade is working at a high rotation speed and under constant impact from the high-temperature and high-pressure mainstream, causing deformation and a reduction in working efficiency; at the same time, the mainstream temperature at the inlet is increasing to achieve a high heat efficiency. Therefore, there is a high demand for turbine blade cooling technology. In this study, the authors proposed replacing the traditional spoiler with a non-homogeneous lattice structure in the inner cavity of the high-pressure turbine blade. The turbine blade was then simulated and experimend in real-world conditions using numerical simulation software and manufactured actual blades, and the maximum deformation of the turbine blade was measured to assess the impact of the non-homogeneous lattice structure on the blade's strength. The findings are as follows: The maximum deformation of the turbine blade optimized with a non-homogeneous lattice structure is 9.91% less than that of the traditional turbine blade with a spoiler, and its deformation-weight ratio is 11.51% less than the latter; the optimized turbine blade has a large cooling area in the concave surface of the blade, which improves the air film cooling effect, the coverage area of gas film hole outlet flow rate has increased by 12.39%. Finally, the non-homogeneous lattice structure optimizes the inner cavity structure of the turbine blade and is useful for improving the turbine blade's structural design and air film cooling performance.

Piezoresistive Sensor for Strain Measurement on Turbine Blade with Wireless Telemetry Data Acquisition

In the paper, strain-gauge sensor design and its application for wireless measurement of blade deformations and strains are presented. The strain sensor was designed using FEM (Finite Element Modeling) and uses piezoresistive strain sensitive boron doped nanocrystalline layers or insulated silicon layers (SOI). Nanocrystalline Diamond (NCD) is a very promising material for fabrication of harsh-environment devices because of its unique mechanical and electrical properties. The prospective of using diamond is not only in sensors (MEMS) but in RF and power electronic as well. Selection of method for data transfer is the key problem in rotating mechanisms. Traditional approach is using the slip ring, but it is not suitable for multisensor applications due to the requirement of one slip ring per sensing element. Telemetry can be related to transfer a data over any media, but is typically applied on wireless communications. A basic telemetry system consists of a measuring element or sensor, a device for sending the transmission, a receiver, and an output controller which records and displays data.

Mechanical response analysis of the wide-chord hollow fan blade considering the fluid–structure interaction

The aero-engine wide-chord hollow fan blade with a cavity stiffener structure can effectively reduce the weight and greatly increase the rotational speed. However, during the high-speed rotation process of the hollow fan, there is a strong coupling effect between the solid domain of the blade and the incoming air. This effect leads to a certain deformation of the rotor blade, which has a large impact on the structural strength of the blade. Aiming at the problem of the fluid–structure interaction in its operation, the finite-element method was used to simulate the two-layer structure of the TC4 titanium alloy wide-chord hollow fan blade. The centrifugal force and fluid–structure coupling effect were considered when carrying out the research on the structural mechanical characteristics of the blade. The results show that the maximum equivalent stress of the blade considering the fluid–structure coupling effect is 508 MPa at the rotational speed of 2,900 r/min, which is approximately 18% higher than the maximum stress when only the centrifugal force is considered. This phenomenon indicates that the effect of aerodynamic force on the blade stress cannot be ignored. The stress concentration area of the blade is located in the third stiffener from the leading edge and near the root of the blade, and the aerodynamic force has a more significant effect on the radial stress distribution of the blade. Further analysis of the equivalent stress distribution along the blade tip direction shows a trend of first increasing and then decreasing. The maximum equivalent stress appears at a distance of 30 mm up to the bottom of the stiffener.

Performance enhancement of Savonius wind turbine through partially deformable blades

In this study, we employ partially deformable blades to elevate the performance of Savonius wind turbines. The Bucket is constructed with rigid components equipped with a guidance system, resulting in continuous changes in its shape during turbine rotation. As the trailing edge of the advancing blade expands, it creates an active slot, effectively correcting the Bucket’s pressure distribution and enhancing the positive torque generated by the turbine. We employ a two-dimensional (2D) numerical model, implemented using the commercial software ANSYS-Fluent 23.0, with the governing motion equation executed through a user-defined function (UDF). This investigation explores the mechanism of performance enhancement by varying expansion amplitudes Our results, obtained at a Tip-speed ratio (TSR) of 1, reveal that when the amplitude of deformation exceeds one-quarter of the Bucket radius, the partially deformable blade outperforms the rigid blade, leading to a remarkable 32% improvement in the torque coefficient. These findings signify a promising path toward enhancing Savonius turbine efficiency.

Performance Evaluation of Damaged Blades Using Numerical Simulation and Machine Learning

The formulation of maintenance strategies for gas turbines requires an accurate and rapid assessment of damaged blade performance. Variety and uncertainty in the three-dimensional geometric deformation of gas turbine vanes and blades increase the difficulty of degradation analysis. In this paper, the effects on the aerodynamic performance of partial damage to turbine nozzle guide vanes are investigated experimentally and numerically. A methodology for constructing a deformation–degradation model for high-pressure gas turbine vanes/blades is proposed based on machine learning. A database consisting of 670 numerical simulation results with various deformation patterns is constructed for the vane cascade. A mapping is constructed between the matrices defining geometric deformations and the total pressure loss coefficient of the cascades based on a convolutional neural network model. The accuracy of this deformation–degradation model is verified against experimental results. We find that deformation on the suction side of the blade has the most significant influence on aerodynamic performance. The deformation–degradation model constructed for a specific cascade provides a rapid evaluation of aerodynamic performance based on rough geometrical measurements without additional experiments or numerical simulations, providing a potential tool in the precise repair of gas turbines.

Application of an Open-Source OpenFoam for Fluid-Structure Interaction Analysis of the Horizontal-Axis Wind Turbine Blade

This study investigates numerical simulation for fluid-structure interaction in wind turbine blades, emphasizing the influence of dimensionless numbers. Utilizing OpenFoam, the Navier-Stokes equation is accurately solved with the PISO algorithm, ensuring proper interface conditions. The icoFsiFoam solver is validated through dynamic testing, demonstrating its effectiveness. In contrast to the widely adopted Blade Element Momentum Theory (BEMT), our approach focuses on analyzing blade deformation and resonance phenomena, capturing intricate deformations and stress concentrations. Our investigation explores the impact of reduced velocity on blade behavior across a range of 0.105 to 0.145, while consistently maintaining crucial dimensionless numbers such as Reynolds number (Re = 10⁶), Froude number (Fr = 4.93), and Cauchy number ( Cy = 10-5). The outcomes of this study significantly contribute to the understanding of fluid-structure interaction in wind turbine blades. By examining the oscillatory behavior of the blades, we observe trends similar to those predicted by BEMT. However, our approach surpasses BEMT by providing additional insights into stress concentrations and deformation modes. This advancement enables superior performance optimization and facilitates advanced blade analysis. The implications of our research are paramount for optimizing blade design and performance under varying reduced velocities. By incorporating the findings of this study, blade designers can make well-informed decisions to enhance the efficiency and durability of wind turbine technologies. The presented methodology and results provide a comprehensive investigation into the fluid-structure interaction of wind turbine blades, highlighting the importance of dimensionless numbers and their influence on blade behavior. Overall, this study offers valuable insights for improving wind turbine design and performance.

One-way fluid structure interaction analysis of a static savonius hydrokinetic turbine under different velocity and surface roughness with different blade materials

Hydrokinetic turbines are prone to a harsh hydrodynamic environment with intricate vortical flows that elevate the probability of failure. The degradation of the blade surface caused by corrosion can impact the blade's hydrodynamic and the structural performance. This paper reports a one-way three-dimensional fluid-structure interaction simulation to analyse the performance of a static Savonius hydrokinetic turbine at varying rotor positions, with different surface roughness and water velocities, in terms of coefficients of static torque, static torque, stresses, and blade deformation. The simulations revealed that the optimum position for the highest coefficient of static torque was at 15° (Cst = 0.30) in reference to the water flow. Increasing the water velocity from 0.4 ms−1 to 0.84 ms−1 improved the turbine static torque due to an increase in the kinetic energy. However, the presence of surface roughness has deterioration effects on the static torque coefficient due to a delayed separation which causes a drag reduction. The simulation predicted no structural failure at 0.4 ms−1 and 0.84 ms−1, but varying materials exhibited varying maximum principal stress and deformation, highlighting the significance of the early development of materials selection process. The maximum von Mises stress and deformation was obtained when the turbine is resting at 45° for aluminium blade (σ = 1.05 MPa, ε = 5.6e−4 mm). The results of this study indicate suitable materials from a hydrodynamic and material perspectives for the construction of the Savonius hydrokinetic turbine, which can be implemented in the design process to potentially save cost and minimize turbine downtime.

Improved seismic risk evaluation for high‐voltage switchgear equipment: A copula‐based framework considering joint failure modes

AbstractTraditional seismic evaluations for high‐voltage switchgear equipment, the critical power facilities, consider only structural failure mode and may underestimate the actual seismic risk. By additionally introducing a probable functional failure mode caused by the excessive deformation of the switchable blade of equipment, a novel copula‐based framework is proposed to utilize limited samples to generate simulation data and evaluate the joint failure probability (JFP). The correlation index and Akaike Information Criterion are employed to optimize the Copula function. For illustration, a disconnector, representative switchgear equipment, was selected as an example and modeled with the experiment validation. Model analysis results demonstrate the Clayton type is the most competent for evaluation. Neglecting functional failure can significantly underestimate the actual failure probability at various seismic intensities, up to 50%. Furthermore, it was found that the current equipment material strength level already meets the requirements, and enhancing strength alone does not effectively improve reliability under strong earthquakes. For PGA intensities ≥0.7 g, the blade deformation capacity plays the primary reliability constraint, independent of material stress. A cost‐effective seismic design should optimize the combination of allowable material stress and blade deformation based on the JFP considering seismic intensity and targeted reliability.

Numerical investigation of the use of flexible blades for vertical axis wind turbines

This study proposes a novel vertical axis wind turbine (VAWT) design with flexible blades aiming to improve their energy extraction capability. The blade deformation is achieved using Ansys Fluent dynamic mesh and user-defined functions to control the position of the blades nodes at specific azimuthal angles. An optimization study is carried out using computational Fluid Dynamics (CFD) simulations and Design of Experiments (DOE) to get the optimal design parameters of the flexible blade at different Tip Speed Ratios (TSRs). In addition, a comparison between the DOE results of both 2D and 3D CFD simulations is achieved to assess the use of 2D simulations for optimization purposes. Also, a detailed numerical study of the aerodynamic performance of the turbine based on this new design is done to compare the rigid and flexible blade models' power coefficient and flow fields around the blades. Results of 2D and 3D CFD simulations show that the flexible blades are able to improve the power coefficient of the turbine by up to 66% and 32% respectively at low tip speed ratios diminishing gradually with increasing tip speed ratios. It is also noticeable that similar pattern in power coefficient results was obtained from the 2D and 3D simulations of both turbine models. This, in turn, demonstrates the efficacy of 2D simulations in accurately determining optimized design parameters while significantly reducing computational costs compared to 3D simulations.

Hybrid joint interface in composite fan blade subjected to bird strike loading

An aircraft engine’s fan blades are one of the most important parts of the engine. Bird strikes on fan blades have always been an issue, as bird parts can strike other parts of the engine, potentially causing more damage. It is impossible to avoid being struck by a bird entirely. However, finite element analysis can be used to optimize the design of blade so that the overall impact of a bird on a jet engine is reduced. Even though current composite blades can withstand the impact of a bird strike, some delamination failures have been observed on the blade’s trailing edge side, probably due to vibration bending modes. Instead of the single fiber composite blade that is currently in use, this research proposes using two fibers (Carbon and Glass). For this to be possible, two fiber joints must be designed properly at different locations on the blade. At crucial joint locations, the minimum inter-laminar strain level was used as the design criteria. Blade deformation is simulated using coupon and sub-element level finite element analysis (FEA) models with appropriate boundary conditions with in-built hybrid joints inside. The first stage of this project involved using the Ansys Parametric Design Language (APDL) and linear static analysis to create coupon models for combinations of joint positions. In the present work, dynamic bird strike analysis on sub-element level models was performed with various joint location combinations. The best joint configurations based on static and dynamic analysis results will be suggested for use in the composite blade to prevent delamination.

Application of overset mesh approach in the investigation of the Savonius wind turbines with rigid and deformable blades

Application of overset mesh approach in the investigation of the Savonius wind turbines with rigid and deformable blades

Development of a Procedure for Torsion Measurement Using a Fan-Shaped Distance Meter System.

Maximising the efficiency of wind turbines is crucial for sustainable development of renewable energy. In this context, monitoring and optimising rotor blade performance is becoming increasingly important, especially rotor blade deformation and torsion. We developed an approach for marker-free and contactless measurement of rotor blades during operation. Deformations of rotor blades can be recorded, with focus on torsion measurement. An innovative measuring system, named the fan-shaped distance meter system (FDMS), uses a combination of multiple laser scanners and photogrammetry. The focus of this work is to analyse the suitability of the FDMS for torsion measurement. We designed a torsion simulator to assess the achievable accuracy. Computer simulations and initial laboratory tests have demonstrated precise torsion measurements are possible using this method with an accuracy of 0.3°. Measurements can be carried out during operation of the wind turbine without the need to apply markers or sensors on rotor blades. By precisely recording the deformation and, in particular, torsion of rotor blades, targeted optimisation measures can be obtained in order to maximise performance of wind turbines. This innovative approach to measure the torsion of rotor blades in operation might offer great potential to increase the efficiency and life cycle of wind turbines.

Identification of milling information and cutter-workpiece engagement in five-axis finishing of turbine blades based on NURBS and NC codes

Five-axis milling is frequently used for machining of turbine blades. Cutting force can cause deformation and vibration of blades, which will eventually affect the milling accuracy and surface quality. Modeling of cutter-workpiece engagement (CWE) is a key process to predict cutting force, especially for complex tool geometries and workpiece surfaces. In this paper, a method to modeling ball-end cutter CWE boundaries for blades with free-form surfaces is presented. Firstly, the NURBS theory is employed to get the surfaces before and after finishing. Secondly, milling information such as coordinate systems is extracted from NC codes. Thirdly, the CWE boundaries are extracted based on the NURBS surfaces and extracted information. The proposed model is a combination of discrete and analytical method. Finally, the performance of CWE model is examined from computational accuracy and efficiency, and is verified through milling test. The proposed method provides a visualization of complex engagement between tool and blade in five-axis milling process, and can be further used in simulation of milling force, vibration and deformation.

Structural Design and Aeromechanical Analysis of Unconventional Blades for Future Mars Rotorcraft

The structural design of rotor blades with ultra-thin, unconventional airfoils is conducted in support of the NASA Rotor Optimization for the Advancement of Mars eXploration (ROAMX) project. The outer mold line was provided by NASA, and the internal structural design was developed at the University of Maryland using a CAD-based three-dimensional (3D) aeromechanical analysis. The main objectives of this paper are to document the unique aeroelastic behavior encountered due to the low Reynolds number (down to 15K) and high subsonic Mach number (up to 0.95). Four different blade designs are considered, with the pitch axis varied from quarter-chord to midchord to determine the effect of center of gravity (C. G.) offset on natural frequencies, blade deformations, root loads, and 3D stresses. Torsional stability is emphasized for each of the designs - especially important due to the low Lock number on Mars. The designs are first studied in vacuum, and significant reductions in root loads and 3D stresses are achieved by moving the pitch axis closer to midchord to reduce the C. G. offset. Next, the design with the pitch axis at 40% chord is selected for a lifting-line aeromechanical analysis. The blade control load, airloads, deformations, and 3D stresses are studied for steady hover. Dynamic control load and dynamic 3D stresses are studied for unsteady hover. Interesting elastic twist is observed due to the trapeze effect and propeller moment, in turn affecting the spanwise distribution of aerodynamic loads. The dynamic control load is found to increase significantly due to inertial coupling from the C. G. offset. The dynamic stresses also increase but still have factors of safety greater than two for both tensile and compressive stress.

Role of surface phenomena in deformation and fracture of gas turbine blades and stamping tools under intense mechanical and thermal loading

Role of surface phenomena in deformation and fracture of gas turbine blades and stamping tools under intense mechanical and thermal loading

Analysis of the blade aeroelastic effect on the floating offshore wind turbine wake in a focusing wave with a hybrid model

With the recent trend toward larger floating offshore wind turbines (FOWT), the influence of blade deformation becomes more obvious. Modelling this fully coupled fluid-structure interaction (FSI) system, especially at extreme sea level with large-scale motion of the entire system, is an essential challenge. A hybrid numerical model integrating the potential-viscous flow model (qaleFOAM), the unstable actuator line method (UALM), the Legendre spectral finite element model (BeamDyn), and the Lumped Mass Mooring Model (MoorDyn) is employed in the current research. This model is capable of effortlessly and accurately reflecting the blade aeroelastic effect on the dynamics of a FOWT system under the circumstances of a focused wave and uniform wind. The result reveals that the aeroelastic impacts have been identified to not only increase the fatigue damage on the turbine blades but also affect the wake field distribution. Based on the temporal and spatial distribution of the velocity fields, it is found that the coupled effects of the large wave elevation and the FOWT high-frequency motions will disturb the velocity in the wake region. The slight variation of the wind speed in the wake region will be exacerbated by about 0.21% to 18.6%, and it transforms the shape of the wake region when the blade aeroelastic effect participates in the coupled effect. This phenomenon may further affect the downstream FOWT system features through the upstream FOWT wake field.

A Novel Method for the Determination of Blade Vibration Stress Considering the Change in Blade Tip Timing Sensing Position

Abstract Blade tip timing (BTT) technology is concerned with the estimation of turbomachinery blade stress. The stress is determined from BTT data by relating the measured tip displacement to the stress via finite element (FE) models based on the sensing position. However, the correlation of BTT data with FE predictions involves a number of uncertainties. One of the main ones is the effective positions detected by sensors may deviate from their nominal position due to the blade deformation, which will yield deceptive calibration factors. To deal with this problem, a novel method based on the amplitude ratio and virtual displacement optimization under the distance constraints of sensors installed in different axial positions is proposed to determine the accuracy calibration factors and sensing positions. It realizes the identification of sensing positions without the information of static deformation, and overcomes the inapplicability of the corrected displacement to bending modes. Both synchronous and asynchronous vibrations of five typical vibration modes are discussed to illustrate the applicability of this method. The results show that this method has better performance than traditional method. The prediction errors of bending modes are reduced from 20 ∼ 30% to 7%, and the maximum error of other modes is reduced from 72% to 23%. In addition, sensitivity analysis is performed to investigate the influence of vibration levels and mode shape inaccuracies. Results demonstrate the great potential of this method in vibration stress determination.

Aerodynamic and structural analysis for blades of a 15MW floating offshore wind turbine

Recent years have seen an important evolution toward large-scale and increased gross capability in the design of floating wind turbines. For an up-to-date 15 MW wind turbine, the slender blades sustain undesirable risks of failure and fatigue due to the significant interaction between fluid and structure (FSI). Considering its sufficient resolution, a one-way CFD-FEA (Computational Fluid Dynamics-Finite Element Analysis) FSI model is established on a full-scale floating IEA 15 MW Reference Wind Turbine (RWT). Particular attention is focused on the effects of the wave-induced motions on the wind field, the structural response of the blades, and the power generation performance of the floating 15 MW wind turbine. It is found that the relative velocities between the blade and the wind field are evidently disturbed by the pitch and surge motions, resulting in the amplified pressure maxima and abrupt change on the leading edge. Meanwhile, the motions amplify the maximum thrust, torque, and aerodynamic power, but also introduce the minima close to zero. This would lead to significant instability in energy production and possibly a sudden halt of the wind turbine gearbox. Moreover, owing to the detailed 3D composite FEA model, the enlarged stresses and tip deformations of blades due to the platform motions are revealed with better fidelity than the beam model in previous FSI simulations.