Rotor Blade Research Articles

Consideration of various configurations of SG6043-based rotor applied in small capacity horizontal axis wind turbine

The SG6043 airfoil model is well known for its high aerodynamic efficiency and it is suitable for designing small wind turbine blades. This paper determined the optimal blade configurations using only the SG6043 airfoil model with ten different lengths from 1 m to 10 m. Then, it proposed the most suitable model for a rated wind speed of 5 m/s in Vietnam. The chord and twist values of each blade’s part were optimized by using the Betz optimization method (BOM) in the Qblade open software. Several important characteristic quantities such as lift coefficient (Cl), drag coefficient (Cd), power factor (Cp) and power (P) of the different blade configurations are determined by using a combination of both XFLR5 code and Qblade software. After that, parameters related to operation such as pitch angle and rotation speed of the rotor were also investigated to find the operating conditions for the best efficiency of wind energy exploitation. The obtained results show that the Cp of the blades has a maximum value of about 0.476 and the P has a value of up to 95.319 kW in operating conditions with a wind speed range between 1 m/s and 10 m/s. In addition, the ratios of power to blade surface area (P/S) and the ratios of power to blade volume (P/V) at the wind speed of 5 m/s were also investigated. The results show that rotors with blades ranging from 3 m to 5 m will give much higher P/S and P/V values than other blade configurations under these operating conditions. This emphasizes that these blade configurations will bring more economic benefit because they will consume less material and reduce production time while still ensuring the required capacity value. Finally, the 5 m blade rotor with a capacity of 2.750 kW at a rated wind speed of 5 m/s was proposed as the rotor suitable for individual household use. This design can help millions of Vietnamese households be proactive in their power source, thereby contributing to the significant reduction of CO2 emissions from coal-fired power plants.

Improving Aeromechanical Performance of Compressor Rotor Blisk with Topology Optimization

When it comes to modern design of turbomachinery, one of the most critical objectives is to achieve higher efficiency and performance by reducing weight, fuel consumption, and noise emissions. This implies the need for reducing the mass and number of the components, by designing thinner, lighter, and more loaded blades. These choices may lead to mechanical issues caused by the fluid–structure interaction, such as flutter and forced response. Due to the periodic aerodynamic loading in rotating components, preventing or predicting resonances is essential to avoid or limit the dangerous vibration of the blades; thus, simulation methods are crucial to study such conditions during the machine design. The purpose of this paper is to assess a numerical approach based on a topology optimization method for the innovative design of a compressor rotor. A fluid-structural optimization process has been applied to a rotor blisk which belongs to a one-and-a-half-stage aeronautical compressor including static and dynamic loads coming from blade rotation and fluid flow interaction. The fluid forcing is computed by some CFD TRAF code, and it is processed via time and space discrete Fourier transform to extract the pressure fluctuation components in a cyclic-symmetry environment. Finally, a topological optimization of the disk is performed, and the encouraging results are presented and discussed. The remarkable mass reduction in the component (≈32%), the mode-shape frequency shift from a fluid forcing frequency, and an overall relevant reduction in the dynamic response around Campbell’s crossing confirm the efficacy of the presented methodology.

Scalable electromagnetic energy harvester for wind turbine rotor blade applications

Abstract One of the biggest challenges in structural health monitoring for rotor blades in wind turbines is to provide enough energy to power wireless sensor nodes. Batteries are not an adequate solution due to their limited lifetime and conventional cabling fails due to the rotation of the rotor blade. Therefore, we present an electromagnetic energy harvester that is specifically designed to be operated inside rotor blades and can generate a sufficient amount of energy. It uses the changing gravitational force vector to move a permanent magnet in a tube and converts this mechanical into electrical energy by coils arranged around the tube. Finite element methods simulations were performed to estimate the generated energy and an extensive parameter sweep of several key design parameters provided guidance for an optimized performance of a prototype. This device was characterized in the lab followed by a field test in a wind turbine where it was operated for several days and provided a continuous and rectified power of 6 mW, enough to power conventional wireless accelerometers, typically used within a predictive maintenance concept for the vibrational monitoring of rotor blades.

Design and Non-Linearity Optimization of a Vertical Brushless Electric Power Steering Angle Sensor

This paper presents the design and the non-linearity optimization of a new vertical non-contact angle sensor based on the electromagnetic induction principle. The proposed sensor consists of a stator part (with one solenoidal excitation coil and three sinusoidal receiver coils) and a rotor part (with six rectangular metal sheets). The receiver coil was designed based on the differential principle, which eliminates the effect of the excitation coil on the induced voltage of the receiver coil, and essentially decouples the excitation field from the eddy current field. Moreover, the induced voltages in the three receiver coils are three-phase sinusoidal signals with a phase difference of 10°, which are linearized by CLARK transformation. To minimize the sensor non-linearity, the Plackett–Burman technique was used, which identified the stator radius and the rotor blade thickness as the key factors affecting the sensor linearity. Then, the particle swarm algorithm with decreasing inertia weights was utilized to optimize the sensor linearity. A sensor prototype was made and tested in the laboratory, where the experimental results showed that the sensor non-linearity was only 0.648% and 0.645% in the clockwise and counterclockwise directions, respectively. Notably, the non-linearity of the sensor was less than −0.696% at different speeds.

Mach number influence on low-pressure turbine flutter

The effect of the Mach number on the vibration amplitude trends of an isolated low-pressure turbine rotor is described. The study utilizes an analytical model correlating the aerodynamic work and the dry-friction work. Aerodynamic damping has been obtained using a frequency domain linearized Navier-Stokes solver, whereas friction damping has been modeled using a heuristic micro-slip model calibrated with the experimental data. In order to validate the analytical predictions, an extensive experimental campaign was conducted. Unsteady pressure transducers flushed mounted in the outer casing, one chord downstream of the trailing edge of the rotor, were used to characterize the vibration of the rotor. The analysis reveals a significant influence of the Mach number on the work balance between aerodynamic and mechanical components. It is observed that the vibration amplitude and the flutter-induced unsteady pressure perturbations of low-pressure turbine rotor blades notably increases when the exit Mach number does.

Combination of Advanced Actuator Line/Disk Model and High-Order Unstructured Finite Volume Solver for Helicopter Rotors

In the research field of rotorcraft aerodynamics, there are two fundamental challenges: resolving the complex vortex structures in rotor wakes and representing the moving rotor blades in the ambient airflow. In this paper, we address the first challenge by utilizing a third-order unstructured finite volume solver, which exhibits lower numerical dissipation than its second-order counterpart. This allows for sufficient resolution of small vortex structures on relatively coarse meshes. With this flow solver, the second challenge is addressed by modeling each rotor as an actuator disk (i.e., the actuator disk model (ADM)) or modeling each blade as an actuator line (i.e., the actuator line model (ALM)). Both of the two models are equipped with an improved tip loss correction, which is introduced in detail in the methodology section. In the section of numerical experiments, the numerical convergence properties of the two types of solvers have been compared in the case of two-dimensional infinite wing. In addition, the relationship between the ALM and the lifting line theory is discussed in the cases of fixed-wing calculations. Another goal of these cases is to validate the tip loss correction presented. The validation of the ALM/ADM and comparisons of computational efficiency are also demonstrated in simulations involving both hover and forward flight rotors. It was found that the combination of the third-order finite volume solver and the ALM/ADM with the improved tip loss correction presents an efficient way of performing the aerodynamic analysis of rotor-induced downwash flow.

Experimental Investigation of Tip Design Effects on the Unsteady Aerodynamics and Heat Transfer of a High-Speed Turbine

Abstract While modern engine manufacturers devote significant efforts to the development of reliable and efficient machines, the introduction of novel, optimized components in the hot gas path represents a risky opportunity. Accurate experimental and numerical data are critical to assess the impact of new technologies on the harsh engine environment. The present study addresses the impact of a selection of high-performance rotor blade tips on the aerodynamic and heat flux field of a high-pressure turbine (HPT) stage. A combined numerical and experimental approach is employed to characterize the interaction of the tip leakage flow with the rotor secondary flows and the casing heat transfer mechanisms for each individual tip geometry. The turbine stage is tested at engine-scaled conditions in the rotating turbine facility of the von Karman Institute. In the present study, the turbine rotor is operated in rainbow configuration to allow the simultaneous testing of multiple blade tip geometries. Reynolds-averaged Navier–Stokes (RANS) simulations are employed to predict the aerodynamic and thermal fields of the individual profiles using test-calibrated boundary conditions. Isothermal steady computations are performed at different wall temperatures to compute the adiabatic wall temperature and the heat transfer convective coefficient. Low-order models are used to represent the over-tip thermal field and the driving heat transfer mechanisms. The time-resolved outlet flow is characterized using a vortex tracking technique and high-frequency aerodynamic measurements to identify the rotor secondary flow structures.

A Hybrid Neural Network‐Based Improved PSO Algorithm for Gas Turbine Emissions Prediction

AbstractIn gas‐fired power plants, emissions may reduce turbine blade rotation, thus decreasing power output. This study proposes a hybrid model integrating the Feed forward Neural Network (FFNN) model and Particle Swarm Optimization (PSO) algorithm to predict gas emissions from natural gas power plants. The FFNN predicts gas turbine nitrogen oxides (NOx) and carbon monoxide (CO) emissions, while the PSO optimizes FFNN weights, improving prediction accuracy. The PSO adopts a unique random number selection strategy, incorporating the K‐Nearest Neighbor (KNN) algorithm to reduce prediction errors. Neighbor Component Analysis (NCA) selects parameters most correlated with CO and NOx emissions. The hybrid model is constructed, trained, and testedusing publicly available datasets, evaluating performance with statistical metrics like Mean Square Error (MSE), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). Results show significant improvement in FFNN training with the PSO algorithm, boosting CO and NOx prediction accuracy by 99.18% and 82.11%, respectively. The model achieves the lowest MSE, MAE, and RMSE values for CO and NOx emissions. Overall, the hybrid model achieves high prediction accuracy, particularly with optimized PSO parameter selection using seed random generators.

Identification of the Aeromechanical Parameters of a Compressor Rotor from Blade Tip Timing Data

Abstract This article presents a maximum likelihood approach to identifying the mistuning, aerodynamic forcing functions, and aerodynamic influence coefficients of compressor rotor blades from noisy experimental measurements of blade deflection. The maximum likelihood estimation approach leads naturally to a nonlinear least squares optimization problem that can be solved using numerical optimization techniques such as quasi-Newton methods. An eigenmode decomposition approach is presented that permits the optimization objective function and gradient to be efficiently calculated so that the optimization is computationally feasible, even for experiments involving very large data sets. Simulation results show that the method has the potential to accurately identify the mistuning and aerodynamic nodal diameter forcing functions, but obtaining accurate results for influence coefficients may not be possible if there is significant disk flexibility. We demonstrate the method using both simulated and experimental blade vibration data from rotor 2 of the Purdue University three-stage axial compressor research facility collected using a light probe tip timing system as the rotor is slowly accelerated or decelerated through a Campbell diagram crossing.

Impact of Blade Modifications on the Performance of a Darrieus Wind Turbine

Vertical axis wind turbines (VAWTs) are gaining increasing significance in the realm of renewable energy. One notable advantage they possess is their ability to operate efficiently in diverse wind conditions, including low-speed and turbulent winds, which are often prevalent in urban areas. In this study, dimples and pitch angles into the rotor blades are used to enhance the aerodynamic performance of a straight-bladed Darrieus turbine. To simulate the turbine’s rotation under transient conditions, computational fluid dynamics calculations are conducted in a two-dimensional setting. The unsteady Navier–Stokes equations are solved, and the k-ω SST turbulence model is employed to represent turbulent flow. The results of the simulation demonstrate that the application of a circular dimple on the pressure side of the blades, positioned at 0.25 of the chord length with a diameter of 0.08 chord length, leads to a 5.18% increase in the power coefficient at λ = 2.7, in comparison to a turbine with plain airfoils. Moreover, when an airfoil with both a dimple and a + 1° pitch angle is utilized, the turbine’s performance at λ = 2.7 improved by 7.17% compared to a plain airfoil, and by 1.8% compared to a dimpled airfoil without a pitch angle. Additionally, the impact of a double dimple on both the pressure and suction sides of the airfoil on turbine performance was investigated. It was discovered that the double-dimpled airfoil exhibited lower performance in comparison to a plain airfoil. The study showed that the utilization of both dimples and pitch angles for airfoils of a Darrieus turbine blade increases the power generated by the turbine.

From Generation to Reuse: A Circular Economy Strategy Applied to Wind Turbine Production

The environmental impact of wind turbine rotor blades, both during manufacturing and at the end of their life cycle, can be significant. The aim of this study was to define and test a methodology for recycling the waste resulting from their production. Particles of waste from the mechanical machining of rotor blades, which were made up of a glass fibre/epoxy matrix mixture, were used to produce toe caps for use by the footwear industry. The addition of 1 wt.% of particles improved the mechanical properties of the epoxy matrix, with a 5.50% improvement in tension and an 8% improvement in stiffness. Characterisation of the laminates, manufactured by hand lay-up technique, revealed that in the three-point bending tests, the additive laminates showed improvements of 18.60% in tension, 7.50% in stiffness, and 10% in deformation compared to the control laminate. The compression test showed that the additive glass fibre toe cap had greater resistance to compression than the control glass fibre toe cap, with a reduction in deformation of 23.10%. The toe caps are suitable for use in protective footwear according to European standard EN ISO 20346:2022. They guaranteed protection against low-velocity impacts at an energy level of at least 100 J and against compression when tested at a compression load of at least 10 kN.

Relationship between Casing Pressure and Non-Synchronous Vibration in an Axial Compressor

The relationship between aerodynamic forcing and non-synchronous vibration (NSV) in axial compressors remains difficult to ascertain from experimental measurements. In this work, the relationship between casing pressure and blade vibration was investigated using experimental observations from a 1.5-stage axial compressor under off-design conditions. The wavenumber-dependent auto-spectral density (ASD) of casing pressure was introduced to aid in understanding the characteristics of pressure fluctuations that lead to the aeromechanical response. Specifically, the rotor blade’s natural frequencies and nodal diameters could be directly compared with the pressure spectra. This analysis indicated that the rotating disturbances coincided with the first bending (1B) and second bending (2B) vibration modes at certain frequencies and wavenumbers. The non-intrusive stress measurement system (NSMS) data showed elevated vibration amplitudes for the coincident nodal diameters. The amplitude of the wavenumber-dependent pressure spectra was projected onto the single-degree-of-freedom (SDOF) transfer function and was compared with the measured vibration amplitude. The results showed a near-linear relationship between the pressure and vibration data.

CHARACTERISING THE UNSTEADY FLOW-FIELD IN LOW-FLOW TURBINE OPERATION

Abstract Current operational considerations require steam turbines to operate in a more flexible way, with an increasing part-load operation. For low flow rates, the interaction of highly separated flow with the high rotational speed causes windage flow. This type of flow is characterized by increased temperature and highly unsteady flow, which forms vortex structures that rotate at a fraction of the rotor speed. If their magnitude is sufficiently high and the frequency is close to the blade eigenfrequency, non-synchronous vibration (NSV) is induced. In this paper, low-flow turbine operation is investigated using a three-stage turbine rig, featuring an instrumentation concept focused on capturing aerodynamic and aeroelastic phenomena. Extensive steady probe, unsteady pressure, and tip-timing measurements are utilized. It covers a wide range of operation in terms of rotational speed and mass flow rates. Low-flow regimes are detected by a reversed torque and increase in temperature. Unsteady measurements during transient operation identified large-scale vortical flow structures rotating along the circumference, so called rotating instabilities (RI). The onset, growth, and breakdown regimes of RI are characterized for different low-flow conditions. The quantitative characteristics of RI are derived by a cross-correlation of multiple unsteady sensors. The blade vibration measurements show a moderate structural response from unsteady aerodynamic excitation. Later in the study, an acoustic excitation system has been applied to trigger a locked-in NSV. From that, significant blade response has been observed, revealing a high degree of mistuning and damping of the rotor blading.

Design and manufacturing of aeroacoustic metamaterial: Textured rotor blades with enhanced acoustic and aerodynamic performance

Unmanned aerial vehicles (UAVs), commonly referred to as drones, have attracted increasing attention as urban aerial mobility platforms. A pivotal consideration in their optimization is the reduction of rotor blade noise without compromising aerodynamic performance. This study endeavors to advance the field by developing aeroacoustic metamaterials tailored specifically for rotor blades, to concurrently achieve noise reduction and thrust enhancement. To enhance these acoustic and aerodynamic performances, the surface of the rotor blade was designed to incorporate various texture patterns. These textured blades were fabricated using photopolymerization-type additive manufacturing. Experimental investigations revealed that the grid-textured blade exhibited superior efficiency in noise reduction but an inferior thrust force. Numerical simulations were conducted to investigate the effect of surface texturing on the airflow near the blade. These simulations revealed that surface texturing effectively diminished the turbulence kinetic energy in the proximity of the blade, resulting in a corresponding reduction in the noise levels. However, a patterned groove located at the leading edge induces flow separation, leading to a discernible reduction in the thrust. An adaptive texture gradation method was then employed to avoid flow separation at the leading edge, and the resulting grid-textured blade demonstrated reduced noise and augmented thrust. The simultaneous enhancement of acoustic and aerodynamic performances signifies the emergence of an aeroacoustic metamaterial, offering a promising solution to the critical challenge of noise mitigation without compromising propulsion efficiency.

Aerodynamic noise analysis of tilting rotor in edgewise flow conditions

This paper presents a comprehensive experimental analysis of the noise characteristics of an isolated tilt-rotor system under edgewise flight conditions. The investigation explores the effect of rotor tilt on noise and aerodynamics using flow velocity, thrust, and far-field noise measurements. Flow field results show that as the tilting angles vary, there is a change in speed over the rotor blade surface, which influences vortex formation and wake attributes. The far-field noise spectra revealed a significant decrease in sound pressure level with increasing tilt angle, predominantly evident in both the high-amplitude tonal peaks and the broadband signal within the low-to-mid frequency range. The directivity patterns of the overall sound pressure level also demonstrated a reduction in magnitude with the tilting of the rotor. This reduction was observed consistently across all top-plane observation points, with a monopole directivity trend. Meanwhile, in the side plane array, the decrease was primarily evident above the plane of rotation with a dipole directivity pattern. The radiation direction at which the minimum sound pressure level occurs was identified near the rotation plane, irrespective of the tilt angle. Furthermore, the time-dependent noise analyses revealed dominant and persistent signal characteristics at the blade passing frequency, whereas the mid-frequency range exhibited more intermittent behaviour, and the high-frequency range indicated transient characteristics.

Experimental and numerical investigations on non-synchronous vibration and frequency lock-in of transonic compressor rotor blades

Non-synchronous vibration (NSV) problems in axial compressors are challenging and frequently result in high vibration stress or structural failure within the frequency lock-in region. A deeper understanding of the lock-in phenomenon in NSV is necessary to improve blade reliability and safety. In this study, an experiment was conducted on a multistage transonic axial compressor to obtain frequency lock-in characteristics. The enforced motion of the flexible blade simulation method was used to study the frequency lock-in mechanism between blade vibration and tip unstable flow. The results showed that the aerodynamic frequency characteristic changed from a broadband spectrum to a distinct frequency peak as the NSV onset. The nonlinear vibration pattern could maintain the limited cycle oscillation for 26s. The vibration stress of the frequency locked-in case was approximately 19 times that of the frequency unlocked one. The pressure fluctuations generated by the large-scale radial separation vortex structures were stronger than those of the tip leakage flow, and the third-order harmonic frequency of the circumferential instability flow was close to the first-order bending model natural frequency. The periodic shedding and reattachment process of flow separation provided the initial non-synchronous aerodynamic excitation source. The frequency lock-in phenomenon occurred at a maximum vibration amplitude of 2% and 3% tip chord length. The tip unstable flow characteristics were consistent and entirely dominated by blade vibration.

AHN LifeFlight, 45 Years in the Making: Current Condition and Capabilities of Air Medical Transport.

In Pittsburgh, Pennsylvania, the skies have become a battleground against time in a world where every second counts. Since its inception in 1978, a revolution has occurred in emergency medical services, with LifeFlight Helicopters soaring to new heights in emergency treatment and transport. This article will explore the transformation of helicopter emergency medical services through the decades, where every rotor blade spins with a mission to save lives and rewrite the rules of survival. Allegheny Health Network's LifeFlight is a rotor-wing (helicopter) aeromedical transport service that provides rapid emergent transport for critically ill and injured persons. The program hub of operations is primarily in Western Pennsylvania. Since its inception in 1978, the program has grown and transformed into the sophisticated, highly technical, expanded scope of practice, critical care transport service it is today. The crews spend a significant portion of clinical care focusing on preparing the patient to survive the transport and ensure stability during transit; this phase of transport is equally crucial as the patient care during the actual flight. This article introduces the evolution and innovations that LifeFlight's medical crews and aviation practices have undergone since the program started.

LTI/LQE: A Physics-Based Approach for Online Estimation of Dynamic Loads in the Rotating Frame

Accurate and online load monitoring of vital components located in the rotor system is important for not only inferring usage and estimating fatigue in those components but also for developing load alleviation/limiting control schemes. In the literature, on-board models for online (i.e., real-time) estimation of rotor component loads using available in-flight aircraft fixed-frame measurements are developed using neural networks, a statistical-based approach, or a combination of both. These models are aircraft-specific, do not capture the higher harmonic dynamics of the rotor system vibratory loads, and their synthesis requires obtaining a lot of data. To remedy these issues, this paper introduces a purely physics-based approach to online estimation of rotor system loads. The proposed approach can be applied to any rotary-wing vehicle, does not rely on a large amount of data, and captures the higher harmonic dynamics of the rotor system vibratory loads. The developed model entitled LTI/LQE is synthesized using a linear time invariant (LTI) model of helicopter-coupled body-rotor-inflow dynamics and a linear quadratic estimator (LQE), that is designed to correct the LTI model state response using fixed system measurements. The estimation fidelity of the LTI/LQE model is evaluated in simulation using a high-fidelity nonlinear model of a generic helicopter for online prediction of rotor blade pitch link loads arising from vehicle maneuvers. Results obtained using the LTI/LQE model revealed an interesting finding. It was found that the N/rev (where N is the number of blades) fixed system load measurements have information that can be leveraged to make an inference about the N/rev dynamic loads in the rotating system.

基于ANSYS/LS-Dyna旋耕刀切土仿真分析及优化

Mini-tiller is an indispensable agricultural machinery in hilly and mountainous areas of China. Rotary blade is an important working part of mini-tiller, which directly affects the operation quality and power consumption of mini-tiller. In order to reduce the cutting resistance and power consumption of the rotary blade of mini-tiller, the cutting process of the rotary blade was analyzed by numerical simulation, and the tangential bending radius (R), bending angle (β) and edge thickness (c) of the rotary blade were selected as factors to optimize it. After comparing the cutting resistance and cutting power consumption of the rotary blade before and after optimization, the results show that the cutting force of the optimized rotary blade is smaller than that of the rotary blade before optimization. The cutting power consumption of the optimized rotary blade is 2.4% lower than that of the unoptimized rotary blade, which achieves the purpose of drag reduction and consumption reduction.

Development of an EN8 Steel Stepped Rotor by a Novel Engraving Milling Technique.

The rotor or impeller is a rotational and key part of a pump and compressor. This article presents the detailed development process of a rotor of small size constructed from an EN8 steel cylindrical blank using a novel technique based on a computer numerical control engraving milling machine (CNC-EMM) equipped with a 4 mm tungsten carbide end mill cutter. We fabricated a total of twenty-eight stepped rotors following the Box-Behnken Design (BBD) DoE technique at fourteen distinct combinations of CNC-EMM variable parameters, namely rotational speed, feed, and plunge feed. Average roughness 'Ra', an important surface quality indicator, has been considered and presented in this article, as a quality measure for the fabricated rotors. Feed and plunge feed have been identified as the most influencing variable parameters as per an analysis of variance (ANOVA) test. The lowest average roughness value obtained by this process for the rotor blade was 0.11 µm. A micrograph obtained from a field-emission scanning electron microscope (FE-SEM) showed a uniform and accurate tooth profile along with burr formation at corner edges. This study claims to establish engraving milling as a viable alternative to other manufacturing processes used for rotor blades. The findings of this study are useful to scholars, engineers, and researchers who are exploring new ways to fabricate mechanical parts and components.