Blade Material Research Articles

High-speed Digital Image Correlation (DIC) for measuring deformation and vibration of fast rotating fan blades

Due to ecological requirements, the bypass-ratio of future civil turbofan engines will be increased. This leads to ultra-high bypass ratio (UHBR) engines, which bring in new challenges concerning the blade material, structural integration, and aeroelastic behaviour of the fan. The ambition of the project Composite fan Aerodynamic, Aeroelastic, and Aeroacoustic Validation Rig (CA3ViAR) is to design and test an open-test-case fan that experiences instability mechanisms, which are representative for UHBR fans of civil aircrafts. The optical measurement technique Digital Image Correlation (DIC) allows for the spatial measurement of deformations. The aim is to apply this technique to measure rotor blade deformation under loading and its vibration due to aeroelastic phenomena to get a better understanding of the structural and aeroelastic behaviour of the composite fan. However, the high rotational speeds, blade vibration frequencies, and expected amplitudes pose challenges for the measurement setup. In this work, a high-speed DIC system is prepared and tested to measure deformation and vibration of a fast rotating blade. Additionally, the requirements for the DIC setup are defined and presented. The expected blade tip speeds in the CA3ViAR project are up to 295 m/s and the blade frequencies of interest up to 650 Hz. Therefore, particular emphasis must be given to the setup in order to eliminate motion blur due to the rotation and to achieve the required frequency. This leads to a setup with synchronised high-speed cameras and a laser to measure frequency vibrations up to 1 kHz with an exposure time below 210 ns. Test measurements are conducted on a stationary beam and an axial blower with a max. blade tip speed of 50 m/s. A data analysis method is developed and described to eliminate the rigid body rotation, analyse the deformation of each blade compared to a reference condition, and analyse the spatial vibration in the frequency domain for a high number of data points per time step. The results of the structural beam are in agreement with the reference measurements and numerical simulations. By analysing the spatial vibration modes of the axial blower, the 1F-flap mode is identified at 38 Hz. In conclusion, this DIC setup shows promising results for future deformation and vibration measurements on a scaled UHBR fan.

Influence of Blade-Flow Interactions on Flow Behaviours and Blade Loading of an Automotive Mixed-Flow Turbine

Mixed-flow turbine (MFT) is one type of turbines in automotive turbocharger. Multiple studies on turbine blades and flow interactions were done in this area but mainly focusing on structural responses and none on the fluid behaviours. The objectives of this paper are to compare and analyse the influence of blade-flow interactions on flow behaviours and blade loading at four MFT turbine operating conditions under steady state flow. Flow behaviours are indicated by appearances of secondary flows and blade loading is ratio of static pressure acting on turbine rotor blades over the total isentropic pressure at volute inlet. Blade loading represents capability of turbine blades to generate torque. Three validated simulations models using commercial software were developed, a non-coupled model and coupled models which consists of one-way and two-way coupled model. Non-coupled model assumes blades are rigid bodies and for coupled models, blades are deformable and share interfaces for interactions. Results show that there are differences in flow behaviours in non-coupled and coupled models that affect blade loading. Coupled models produce torque with range 1.33% to 0.60% lower than non-coupled model at most operating conditions. At 50% turbine design speed, average efficiency differences for non-coupled and coupled models to experiment data are 1.38% and 1.28% respectively. There is no significant difference in flow behaviours in one-way and two-way coupled models due to the stiffness of material of turbine blades is high but show minor differences in blade loading and torque.

Material Selection of Face Sheet of Sandwich Plate Used in Blade of Wind Turbine Using MCDM Method

Abstract: The design and materials of wind turbine blades are crucial in terms of performance and durability. They are an essential part of the energy sector. In this article, we use the Multi-Criteria Decision Making (MCDM) method to suggest a material selection method for the face sheet for a sandwich shell/web for wind turbine blades. To determine the best material out of all the options, the MCDM method allows the evaluation of multiple criteria. The suggested method takes into account a number of things, including weight, price, mechanical qualities, and environmental impact. Aluminium, Carbon Fibre Reinforced Polymer, and Glass Fibre Reinforced Polymer were the materials assessed in this study. According to the MCDM results, CFRP is the best material for a wind turbine sandwich shell or web's face sheet when taking the chosen criteria into account. The suggested strategy offers a method for selecting materials that is systematic and all-inclusive and can be used in other fields and applications

Study on the thermal transformation of basic components of wind turbine blade

AbstractTo alleviate the environmental pollution caused by waste wind turbine blades and provide new ideas for recycling, the thermochemical characteristics of four basic components of composite materials commonly used in wind turbine blades were studied in this paper. Thermogravimetric experiments in different atmospheres and heating rates, and thermogravimetric‐infrared combined experiments were carried out. The results show that the reaction of epoxy resin and thermoplastic polyurethane was easy and deep in N2 and CO2. Except for glass fiber, the other three components showed different combustion characteristics in air. The maximum reaction rates and activation energy of resin‐based components in N2 increased with increasing heating rate. The pyrolysis products of the four basic components all contained CO2 and CO, and some aromatic substances could be generated during the thermal transformation of epoxy resin and thermoplastic polyurethane. It can be concluded that the thermal transformation properties of the basic components of the composite material of wind turbine blades can be used to treat the waste blades, making the resin as the matrix material undergo a thermal transformation reaction and recover the fiber. This is to effectively guarantee the green and sustainable development of wind power generation.

Fatigue crack initiation and growth behavior within varying notch geometries in the low‐cycle fatigue regime for FV566 turbine blade material

AbstractPlain bend bars made from FV566 martensitic stainless steel were extracted from the root of ex‐service power plant turbine blades and several industry‐relevant notch geometries were introduced. Some of the samples were shot peened. The notched bend bars were loaded plastically in the low‐cycle fatigue regime and finite element (FE) modeling carried out to investigate the effects of changing notch geometry, combined with shot peening, on fatigue behaviors such as crack initiation, short crack growth, and coalescence. Shot peening damaged the notch surface, accelerating initiation behaviors, but had a lifetime‐extending effect by retarding short crack growth in all tested notch geometries. At a total strain range higher than 1.2%, the lifetime extension benefit from shot peening was diminished due to compressive residual stress relaxation in the notch stress field. Notch geometry (and the associated varying constraint levels and stress/strain gradients) was found to have no notable difference on fatigue life when tested at identical notch‐root strain ranges.

Corrosion of Potential First Stage Blade Materials in Simulated Supercritical CO2

ABSTRACT Global power consumption is predicted to double by 2050, notably driven by the transportation and energy sectors necessitating limitations of emissions. Due to its compact turbomachinery, better thermal efficiency, and simpler layout, supercritical-CO2 cycles have received attention, with numerous variations proposed (either indirect-fired/closed cycles or direct-fired-open cycles). One technical challenge is degradation pathway quantification of turbine materials in sCO2 as selection is crucial to successfully and economically operate new plants. This requires degradation assessment in representative environments simulating the Allam cycle. Laboratory tests were conducted on a first stage turbine blade alloy, CM247, with either an environmentally resistant coating or bond coat/thermal barrier coat at one atmosphere and 800°C, with potential exposure including (O2, H2O, N2, SO2) for up to 1000 h. Weight change and metallographic measurements tracked scale development. Scanning electron microscopy/energy dispersive X-ray spectroscopy studied scales and internal precipitates. Locations of contaminant element in the CO2-rich environment were investigated.

In-situ SEM study on fatigue crack behavior of a nickel-based single crystal alloy at 950 °C and 1050 °C

As the blade material of engine, nickel-base single crystal superalloy has been subjected to complex service environment such as high temperature and alternating load for a long time. In this work, the mechanism of fatigue microcrack initiation and propagation in a nickel-based single crystal at 950 °C and 1050 °C was studied by using the in-situ scanning electron microscope high temperature fatigue test system. At 950 °C, the alloy deformation was controlled by slip and the crack shear γ/γ’ phase cracking, showing Stage I mode. At 1050 °C, the alloy crack tearing occurred at the γ phase parallel to the loading direction and γ/γ' interface perpendicular to the loading direction and presents a Stage II mode perpendicular to the loading axis, then changes into Stage I in the accelerating stage. The deformation mechanism of fatigue cracking at two temperatures was compared. Besides, the influence of the microstructure defects on the fatigue crack behavior was discussed. The results show that the propagation of the microcrack below 100 μm shows evident fluctuations, which is closely related to the microstructure and the development stage of the fatigue crack.

Wind Tunnel Tests of Surface Icing Distribution on Aluminum Alloy and Carbon Fiber-Reinforced Polymer Blades for Wind Turbines

In cold areas, wind turbines face ice risk. The ice accretion on the blade surface will reduce the output power of wind turbines. To explore the effect of blade material on icing distribution, the blades of aluminum and carbon fiber-reinforced polymer (CFRP) were made, and the icing wind tunnel tests were carried out. The icing test is conducted under three icing times (2 min, 4 min, and 6 min) and three ambient temperatures (−5 °C, −10 °C, and −15 °C). The experimental results show that the icing time and ambient temperature are key factors in icing distribution. When the icing time increases, the average thickness of ice on the blade surface increases, and the airfoil profile of the blade changes significantly. When the ambient temperature decreases, the average thickness of ice on the blade surface increases, and the ice type changes from glaze ice to rime ice. The effect of blade material on the icing distribution is significantly affected by ambient temperature.

Alternative Manufacturing Processes (AMP) for Wind Turbine Blade Material, in Isolated Regime Based on AHP

The newest cutting-edge technologies in Renewable Energy Sources (RES) projects provides economic benefits for project developers, especially when installing a wind power in isolated regime. The research was focused on finding technological alternatives, using an optimal composite material for wind blades structure. In this sense, the research team made a decision based on critical analysis of today existing technologies that can provide feasible solutions. The Analytic Hierarchy Process (AHP) method provides results for choosing alternative manufacturing processes, suitable for blades structure, in isolated regime

Aluminum Alloy Reinforced with Agro-Waste, and Eggshell as Viable Material for Wind Turbine Blade to Annex Potential Wind Energy: A Review

The most important part of the wind turbine is the blade. From existing studies, it has been concluded that most wind turbine blades have a high rate of failure during operation due to fatigue, because of a lack of proper material selection processes. Materials such as fiberglass, wood, aluminum, and steel have been used but have not been able to qualify as sustainable materials. Therefore, this study focuses on the review of existing materials employed for developing metal matrix composites as ecological materials to produce wind blades. This study discusses the application of aluminium, silicon, and magnesium metal matrix alloys and the implementation of agro-waste materials (coconut rice, coconut shell, rice husk ash, and sugar Bagasse ash) and eggshell as reinforcement particulates for metal matrix composites for developing wind blades. The study also reviews the method of production of matrix composites. From the results obtained via the review, it is clear that the application of eggshells assists as a binding element for proper mixture, and the combination of Al–Si–Mg alloy with coconut rice and shell improves the strength of the material, since wind blades need durable materials and ductility due to their aerodynamic shape to convert enough energy from the wind.

A comprehensive review on design and development analysis and blade material selection of helical Savonius rotor

The helical Savonius rotor (HSR) is used as green energy generation. The accurate design of HSR is essential before installing any wind farm in a region. It has been widely employed that positive static torque coefficients of helical Savonius rotor are higher compared to conventional semicircular rotor stated by several researchers. The reason is behind that the formation of secondary vortex of fluid. It is leading by vertical vortex flow, which passes over the curve surface and creates drag force. Still now, various design have been proposed to meet peak power output through optimum geometry parameters like blade profile design, aspect ratio and overlap ratio. The selection of blade material is also the influencing parameter to improve the starting torque of the rotor. In this regards present paper is aim to study the details experimental, numerical, and analytical review on HSR and selection of blade material with minimum production cost.

Failure study of an aircraft engine high pressure turbine (HPT) first stage blade

In jet engines, almost 50% of failures are located in the damage of turbine blades and discs. This paper presents the study to determine the root cause of the failure of a high-pressure temperature blade in a turbofan engine.Visual observation of the blades indicated that initially-one blade was fractured. Subsequently, detachment of the airfoil from this blade and its impact with the rest of the blades of the first turbine disc trigged a catastrophic damage to them and affected later stages blades. Chemical, microstructural and mechanical characterization determined that blade material corresponded to René 142 nickel superalloy.The observed fractographic characters by optical and scanning electron microscopy showed that the fracture of the first damaged blade was due to a thermo-mechanical fatigue mechanism. The fatigue phenomenon was initiated by corrosion pitting on the root surface of the mentioned blade and progressed due to the cyclic stresses and temperature gradients.

Effect of flexible machining on subsurface damage and recrystallization of single crystal superalloy

Single crystal superalloy has gradually become the primary manufacturing material of advanced aero-engine turbine blades. However, it is easy to introduce subsurface damage and recrystallization to worsen the high-temperature service performance during the precision machining process. To investigate the effect of abrasive belt grinding on the subsurface damage and recrystallization of single crystal superalloy, a flexible adaptive continuous feed analysis model was established, which was confirmed by a series of flexible and rigid scratching experiments. The experimental results showed that the plastic deformation area generated by flexible scratch was smaller, but the slip area was larger. The recrystallization depth of flexible scratch was about 35 % lower than that of rigid scratch. The effective material removal rate of the flexible scratch was larger. The flexible reciprocating scratch verified the feasibility of the adaptive continuous feed model. And the recrystallization depth of flexible reciprocating scratch was about 47 % lower than that of rigid scratch. It indicates that the flexible machining method can not only reduce the recrystallization depth but also ensure material processing efficiency. It is expected to provide a theoretical basis and technical support for the high efficiency and low-damage machining of single crystal superalloy.

Large-amplitude vibration of rotating functionally graded blades including geometrical nonlinearity and stress stiffening effects

The nonlinear frequency responses of functionally graded (ceramic/metal/ceramic) straight/curved blade-type structures are examined under rotation and thermal environment. Here, the geometrical nonlinearity is introduced using Green-Lagrange’s strain via the higher-order shear deformation theory. The constituent materials, i.e. ceramic and metal-alloy, are considered to be temperature-dependent, whereas, the overall blade material properties are evaluated using Voigt’s homogenization scheme via a modified power-law function. The equations of motion are obtained using Hamilton’s principle by including the geometrical nonlinearity and stress stiffening effects. The linear and the nonlinear frequency responses are computed through the developed nonlinear finite element method and Picard’s successive iteration scheme. An exhaustive computation is carried out to report the linear and the nonlinear vibrational behavior of the proposed composite straight/curved blade model at small-to-large amplitudes for various sets of combinations of geometric and material parameters, such as blade span, blade thickness, volume fractions, rotational speed, and temperature.

Numerical investigations of heat transfer characteristics using oblong fins and circular fins in a wedge channel

Abstract Turbine inlet air temperatures are extremely high, which can result in blade material damage. As a result, cooling the turbine blades is required, and a variety of cooling techniques have been introduced. The majority of the previous research on pin fins has focused on circular fins using a wedge duct to apply a constant temperature and uniform heat flux to the end wall and pin fin surfaces. The present study compares seven oblong pin-fins to seven circular pin fins in a wedge duct with a Reynolds number range of 10,000–50,000 and a constant heat flux (surface) of 3280 W/m2 applied to the endwall and surfaces of the oblong pin fin. The results indicate that the friction factor for oblong fins is 14% lower than for circular pin fins. The thermal performance factor is increased by 11.4%. The thermal performance factor can be improved by using oblong pin fins with higher Reynolds numbers.

Strength Analysis on Horizontal Axis Wind Turbine Propeller Blade PVC Pipe with Angled Ends

The basic problem of appropriate wind energy technology is how to design wind turbines from materials that are easily available on the market, one solution is PVC pipe as the blade material. For this reason, it is necessary to analyze the working stress that occurs in the blade construction, so that the PVC pipe propeller wind turbine is safe when applied in society. The purpose of this study was to determine the effect of wind speed and tip elbow width on working stress. The simulation test method uses SolidWorks Flow Simulation Software and then the results are exported to Static Simulation to determine the strength of the material. Simulation tests were carried out with wind loads on PVC pipe propellers with wind speeds of 5 m/s, 6 m/s, and 7 m/s and elbow tip widths of 100 mm, 110 mm, and 130 mm. The results of the maximum stress value in the wind turbine simulation test with the addition of an elbow tip were obtained at a wind speed of 7 m/s and an elbow tip width of 130 mm

Investigation of Aerodynamic Characteristics of a Two-Bladed Sailing Wind Turbine

The article examines a prototype of a wind turbine with two blades. For experimental work, a mock-up of a sailing wind turbine consisting of two blades was developed. The material of the sail blades was selected according to elasticity and lightness, cheapness, roughness of the streamlined surfaces. The study shows the aerodynamic parameters acting on the blade. The air flow velocity varied from 3 to 12 m/s. The dependence of the lifting force and the frontal barrier on the air flow velocity was obtained by turning the blades of the wind turbine so that the angle of attack was α = 00; 150; 300; 450 и 600. It is established that when the position of the blade’s changes, the lifting force and the drag force decrease. With an increase in the angle of attack α > 00 leads to a decrease in the midsection of the wind wheel with respect to the air flow. On this basis, there is a decrease in aerodynamic forces. As the speed of the air treacle increases, the speed of rotation of the wind wheel also increases. However, during the experiment it was found that the location of the blades at different angles affects the numerical value of the rotational speed. According to the conducted experiments, several values were obtained. The analysis of the obtained values is carried out. A graph is constructed based on the dependence of the wind wheel rotation frequency on the wind speed with a change in the angle of attack. A wind turbine with blades with a variable angle of attack, which, turning, gradually become more parallel to the direction of the wind. Centrifugal forces regulate the inclination of the blades, and as a result, the speed of rotation of the wind wheel, and keep the wind generator at the nominal speed of rotation.

Simulation of the Erosion-Corrosion Destruction Process of Steam Turbine Low-Pressure Cylinder Blades

This paper is devoted to the important problem of creating a method for predicting the intensity of erosion-corrosion destruction of the working blades material of low-pressure stages of powerful steam turbines, considering the complex physical processes that accompany the emergence, transformation of erosion-hazardous droplets and their interaction with elements of the flow path. The features of the construction of some existing erosion models are considered. The model that is developed at the Institute of Mechanical Engineering Problems of the National Academy of Sciences of Ukraine and based on a deterministic-statistical approach to its creation is analyzed in detail. The calculations performed during the research showed a satisfactory coincidence with the results of experimental tests by various authors, obtained on droplet impact stands, which contributed to the successful use of the model in creating a comprehensive method of predicting the wear of working blades. To do this, it was supplemented by the method of determining the parameters of the erosive environment based on the droplet movement equation, taking into account the size distribution law. Along with that, it is shown that the considered model, although it allows to carry out fairly accurate prediction of the development of erosive wear at the modern level, has difficulties in its construction due to the need to identify it from the data of full-scale experiments, the number of which is limited. It has been established that one of the important reasons for the discrepancies that arise is the failure to include of the electrophysical component of the processes occurring in a two-phase flow. In this regard, the results of comprehensive studies of steam electrization and its influence on the working processes of wet steam turbines are considered. It is shown that the change in the properties of the working medium as a functional erosive medium as a result of electrification causes a significant increase (relative to neutral wet steam) of electrochemical processes. At the same time, the kinetics of the damage accumulation to the metal surface layer changes due to the joint occurrence of several negative processes: droplet impact influence; electrochemical processes caused by mechanical and structural and chemical heterogeneity of the surface; hydrogen absorption; changes in mechanical properties under the electric field influence. It was noted that the contribution of hydrogen absorption to changes in mechanical properties is the greatest. According to a preliminary assessment, the complex negative droplet impact and electrophysical influence on the metal surface reduces the incubation period and intensifies the erosion-corrosion process by approximately 2 times

Predictive Modeling and Analysis of Material Removal Characteristics for Robotic Belt Grinding of Complex Blade

High-performance grinding has been converted from traditional manual grinding to robotic grinding over recent years. Accurate material removal is challenging for workpieces with complex profiles. Over recent years, digital processing of grinding has shown its great potential in the optimization of manufacturing processes and operational efficiency. Thus, quantification of the material removal process is an inevitable trend. This research establishes a three-dimensional model of the grinding workstation and designs the blade back arc grinding trajectory. A prediction model of the blade material removal depth (MRD) is established, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS). Experiments were carried out using the Taguchi method to investigate how certain elements might affect the outcomes. An Analysis of Variance (ANOVA) was used to study the effect of abrasive belt grinding characteristics on blade material removal. The mean absolute percent error (MAPE) of the established ANFIS model, after training and testing, was 3.976%, demonstrating superior performance to the reported findings, which range from 4.373% to 7.960%. ANFIS exhibited superior outcomes, when compared to other prediction models, such as random forest (RF), artificial neural network (ANN), and support vector regression (SVR). This work can provide some sound guidance for high-precision prediction of material removal amounts from surface grinding of steam turbine blades.

Carbon Fiber Composites for Large-Scale Wind Turbine Blades: Applicability Study and Comprehensive Evaluation in China

Wind energy is a type of clean energy that can address global energy shortages and environmental issues. Wind turbine blades are a critical component in capturing wind energy. Carbon fiber composites have been widely recognized for their excellent overall performance in large-scale wind turbine blades. However, in China, the wide application of carbon fiber composites in wind turbine blades still faces many problems and challenges. This paper examines the current state of carbon fiber composites for wind turbine blades and the geographical distribution characteristics of wind resources in China. The economic revenues from increasing the length of wind turbine blades in four typical wind farms, including offshore wind farms, are compared. Using a mathematical model, the energy efficiency of carbon fiber composites in the application of large wind turbine blades is evaluated from the aspects of cost, embedded energy, and carbon footprint. Further, the current relationship between supply and demand for the industrial structure of carbon fiber in China is revealed. The manufacturing technologies for carbon fiber composite wind turbine blades are analyzed, and corresponding countermeasures are proposed. Finally, the incentive policy for applying carbon fiber composites to wind turbine blades is explained, and the development prospects are explored. In this paper, the economics and energy efficiency of the application of carbon fiber composite materials in large wind turbine blades are analyzed and comprehensively evaluated by using mathematical models, which will provide a valuable reference for China’s wind turbine blade industry.