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At present, the process of designing a GTE involves a large amount of computational modeling. With the help of computational modeling, it is possible to predict a behavior of an engine part during engine operations before conducting experimental studies. For example, the numerical dynamic behavior analysis of compressor blades and prediction of dynamic stress levels during fluctuations in free modes are urgent problems. A high level of dynamic stress in the compressor blades in resonant modes can break a blade and stop an engine. In this paper, we propose a simple vibration stress estimation method for the compressor blades based on the calculation of natural frequencies and vibration forms. The method is based on a comparative analysis and scaling of stresses by the value of the total potential or kinetic energy. This estimation method is valid for local changes in the blade geometry, which do not lead to changes in the natural frequencies and vibration forms of the blades, assuming that the geometry change does not change the level of the aerodynamic excitation of the blade or its damping. At the stage of development or revision of the blade, a large number of variants of the blade geometry needs to be analyzed in order to reduce dynamic stresses. The proposed vibration stress estimation method has shown its high efficiency in developing and refining the geometry of the compressor blade. The vibration stress estimation method was tested using the rotor blade of a high-pressure compressor. As a result of the experimental study of the rotor blade, a high level of vibration stresses exceeding the permissible level was found for natural frequencies and vibration forms. To reduce the vibration stresses, measures were proposed to modify the geometry of the blade. For the modified blade geometry, the vibration stress estimation was performed with a prediction of the vibration stress values based on the manifested vibration forms. In order to verify the estimated vibration stress change, an experimental study of the modified blade was conducted. The vibration stress estimation method for the compressor blades was successfully verified.

The blades of a hydrokinetic turbine have a great impact on its performance due to they are the elements responsible for capturing the kinetic energy from water and transform it into rotational mechanical energy. In this work, numerical analyses on the performance of a multi-element blade section were developed. The lift and drag coefficients (CL and CD, respectively) of the hydrofoils with traditional and multi-element configurations were studied. For this purpose, 2D numerical analyses were conducted by using JavaFoil code. S805, S822, Eppler 420, Eppler 421, Eppler 422, Eppler 423, Eppler 857, Wortmann FX 74-CL5-140, Wortmann FX 74-CL5-140 MOD, Douglas/Liebeck LA203A, Selig S1210, Selig S1223 and UI-1720 profiles were tested. The results indicated that the Eppler 420 multi-element hydrofoil provided high efficiency to the turbine. This was attributed to its higher relationship between the maximum CL and CD (CLmax /CD), which was equal to 47.77, compared to that of the Selig S1223 profile (39.59) and other hydrofoils studied. Therefore, the final optimized blade section selected was an Eppler 420 multi-element hydrofoil with a flap chord length of 70% of that of the main profile. The hydrodynamic and structural designs of the optimized blade section were validated with detailed 3D numerical models, through ANSYs Fluent software. The fluid and structural domains were connected using one-way coupling. The influence of the blade geometry and the operational parameters on the stresses supported by the blades were found by analyzing the fluid-structure interaction. From the numerical analyses conducted, it was observed that the blades did not exhibit structural fails. In this regard, the multi-element hydrofoil might be used for the design of a horizontal-axis hydrokinetic turbine with a high efficiency.

Utilization of hydro-power as a renewable energy source is now of prime importance in the world. Hydropower energy is available in abundance as a renewable source. For run-of river, low head reaction type Kaplan turbines mostly used. In this paper, a parametric study has been conducted on a complex geometry of Kaplan blade through static and dynamic computational analysis by varying the blade profile at different angles in the CAD model. Blade geometry surface and design were developed in Creo using the coordinate point system on the blade. Further blade profiles were analyzed to check and compare the output results. Results show that by changing the blade profile geometry, CAD models can be improved using the computational techniques. Consequences obtained were validated with the experimental/operational data and then four different blade profiles were developed. Research consequences showed improvement in the power output of the turbine.

El estudio realizado corresponde al tipo de investigación tecnológica, ya que mediante la aplicación de las metodologías de diseño mecánico, se buscó mejorar el rendimiento de una trituradora de botellas tipo PET; el nivel de investigación es experimental, debido a que considerando el tipo de geometría de la cuchilla de corte, se buscó determinar aquel que proporciona mayor rendimiento de trituración. El objetivo de esta investigación fue diseñar un prototipo de trituradora cuya geometría de cuchilla de corte permita mejorar el rendimiento de trituración de botellas tipo PET. Considerando la metodología de diseño VDI 2221, se elaboró la lista de exigencias para el diseño de un prototipo de una máquina trituradora de plásticos PET y la matriz morfológica correspondiente y se obtuvo resultados cualitativos que indican que el rendimiento de trituración está en función de la geometría de la cuchilla de corte de la trituradora de botellas tipo PET. Así mismo, se utilizó el cálculo de diseño mecánico para seleccionar los componentes del prototipo de trituradora, el resultado cuantitativo de este estudio realizado requirió de las mediciones de rendimiento de trituración según el tipo de geometría las cuchillas de corte, luego mediante el análisis de la varianza (ANOVA) de un factor, se determinó que para un nivel de confianza del 95 % el tipo de geometría C (cuchilla con 3 uñas) proporciona mayor rendimiento de trituración con un valor promedio de 21.72 kg/h.

Shrouding of HAWT in a flanged diffuser is among techniques of wind power augmentation especially in urban areas. In this paper, a small scale of Flanged Diffuser Augmented Wind Turbine (FDAWT) was presented with flanges angle (?f) of 0°. The rotor fit for FDAWT was designed based on a modified blade element momentum theory, which adopts on developing the preliminary rotor blade geometry in terms of pitch angle. The modification of the blade pitch angle was based on the maximum wind speeds in the empty flanged diffuser at rotor position along the blade sections. The models of rotor and diffuser were fabricated and experimented in the wind tunnel. The experimental tests were conducted to calculate the power at a different wind velocity ranged 5 - 9 m/s. The performance tests were in terms of power coefficient, CP and torque coefficient, CQ as a function of the tip speed ratio as well as maximum power as a function of the wind velocity. The results show the rate of increase in the maximum power producing for the FDAWT with the modified rotor up to 291% more than what it is for the preliminary bare HAWT, while this increase was only 257% for FDAWT with the preliminary rotor.

In this research work, the investigation and optimization of small horizontal axis wind turbine blade at low wind speed is pursued. In this paper, an optimized design method based on BEM Theory is explained blade radius of 0.2 m rotors investigated with and without winglet blade geometry of 10 Low Reynolds number airfoils. An Xfoil and CFD software were used to devise a novel airfoil (MAF) suitable for use at low Reynolds number. A Matlab program was developed to use BEM theory and optimize blade geometry. The experimental blades were developed using the 3D printing additive manufacturing technique. The airfoils E210, NACA2412, S1223, SG6043, E216, NACA4415, SD7080, SD7033, S1210 and MAF were tested at the wind speed of 2-6 m/s. The airfoils and optimum blade geometry were investigated with the aid of the Xfoil software at Reynolds number of 100,000. The initial investigation range included tip speed ratios from 3 to 10, solidity from 0.0431 – 0.1181, and angle of attacks from 2o to 20o. Later on these parameters were varied in MATLAB and Xfoil software for optimization and investigation of the power coefficient, lift coefficient, drag coefficient and lift to drag ratio. The cut-in wind speed of the rotors was 2 m/s with the winglet-equipped blades and without winglets. It was found that the E210, SG6043, E216 NACA4415 and MAF airfoil displayed better performance than the NACA 2412, S1223, SD7080, S1210 & SD7003 for the geometry optimized for the operating conditions and manufacturing method described.

In this study, small horizontal-axis wind turbine blades operating at low wind speeds were optimized. An optimized blade design method based on blade element momentum (BEM) theory was used. The rotor radius of 0.2 m, 0.4 m and 0.6 m and blade geometry with single (W1 & W2) and multistage rotor (W3) was examined. MATLAB and XFoil programs were used to implement to BEM theory and devise a six novel airfoil (NAF-Series) suitable for application of small horizontal axis wind turbines at low Reynolds number. The experimental blades were developed using the 3D printing additive manufacturing technique. The new airfoils such as NAF3929, NAF4420, NAF4423, NAF4923, NAF4924, and NAF5024 were investigated using XFoil software at Reynolds numbers of 100,000. The investigation range included tip speed ratios from 3 to 10 and angle of attacks from 2° to 20°. These parameters were varied in MATLAB and XFoil software for optimization and investigation of the power coefficient, lift coefficient, drag coefficient and lift-to-drag ratio. The cut-in wind velocity of the single and multistage rotors was approximately 2.5 & 3 m/s respectively. The optimized tip speed ratio, axial displacement and angle of attack were 5.5, 0.08m & 6° respectively. The proposed NAF-Series airfoil blades exhibited higher aerodynamic performances and maximum output power than those with the base SG6043 and NACA4415 airfoil at low Reynolds number.

One of the crucial issues affecting the structural safety of propeller vehicles is the propeller tonal excitation and related vibrations. Propeller rotation during flight generates vibrating sources depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust, and blade geometry. Generally, the higher energy levels generated are confined to 1st blade passing frequency (BPF) and its harmonics, while additional broadband components, mainly linked with the blade shape, the developed engine power, and the turbulent boundary layer (TBL), also contribute to the excitation levels. The vibrations problem takes on particular relevance in the case of composite structures. The laminates in fact could exert damping levels generally lower than metallic structures, where the greater amount of bolted joints allow for dissipating more vibration energy. The prediction and reduction of aircraft vibration levels are therefore significant considerations for conventional propeller aircrafts now entering the commercial market as well as for models currently being developed. In the Clean Sky 2 framework, the present study focuses on a practical case inherent to the AIRBUS-Racer program aiming to design and develop a multi-tasking fast rotorcraft. This paper defines a finite elements (FE)-based procedure for the characterization of the vibration levels of a main landing gear (MLG) composite door with respect to the expected operating tonal loads. A parametric assessment was carried out to evaluate the principal modal parameters (transfer functions and respective resonance frequencies, mode shapes, and damping coefficients) of the landing gear-door assembly in order to achieve reduced vibration levels. Based on the FE analysis results, the influence of the extra-damping, location, and number of ballast elements, the boundary conditions were investigated with respect to failure scenarios of the kinematic line opening the study towards aeroelastic evaluations. Further experimental ground test results serve as a validation database for the prediction numerical methods representative of the composite door dynamic response.

Low cutting forces can significantly reduce damage risk on sensitive tissues adjacent to the bone. Applying an ultrasound tool in bone cutting is an interest among surgeons due to its better control in an incision, low cutting force, and reduced postoperative complications. In this study, by applying a full factorial design of experiments, the effects of changes in cutting tool geometry, ultrasonic power, bone-cutting direction, and tool speed on the cutting forces of cortical bone are assessed simultaneously. The analyses of variance and regression are run on experimental data, and the influence of each factor and interactions of the elements on the cutting forces are discussed. The adjusted coefficient of determination (R2adj.) of the statistical models is 91.49% and 91.15% in the main cutting force and cutting resistant force, respectively. Both the blade geometry and ultrasonic power, together with their interactions, are the most influential factors in cutting forces with 82.2% and 86.6% contribution therein, respectively. Creating teeth in the cutting edge improves the cutting process and reduces the cutting force by about 40%. The ultrasonic-powered toothed edge blade with a 1 mm pitch, low vertical velocity, and high longitudinal speed is recommended for high efficiency and low cutting force.

Sensitivity of the shape of a turbine blade shapes on its performance is more compared to the compressor blade shape. Thus, a lot of research is concentrated on design of turbine blades and wide range of methods were suggested for the same. A blade with acceptable performance should have minimum of first order continuity along the blade curve. Discontinuity on the blade geometry leads to higher pressure gradient and affects the performance drastically. Hence, in this paper a turbine blade is generated, by using Bezier control points, to obtain a smooth blade curve. The blade is divided into leading section, main section and trailing section. The middle section of the blade is formed by cubic Bezier splines ensuring the first and second order continuity on the blade geometry. New blade geometries are formed by shifting the positions of the Bezier control points. The blade geometry formed from this newly shifted Bezier control points is subjected to the same boundary conditions as the baseline profile and the pressure distribution is analysed.The different blades generated are analysed in ANSYS FLUENT 17.2. The computational domain is a two dimensional turbine cascade, consisting of a turbine blade enclosed by periodic boundaries to mimic realistic conditions. A second order upwind strategy is used for inviscid flow analysis.

The self-excitation of last stage of slender blades leading to high vibration amplitudes is a problem encountered in the exploitation of LP steam turbines. This has been resolved by changing the geometry of alternate blades (mistuning). This paper studies the free and forced blade vibrations of various thus mistuned steam turbine systems. Two methods of mistuning are applied: either by changing the blade geometry or by changing the Young’s Modulus. In the LP steam turbine last stage, the nodal diameters of blades are destroyed by even the slightest changes to natural blade frequencies and only individual blades vibrate. Blade feathering does make nodal diameters appear, but only in every second blade. The blade geometry mistuning gives more reliable results. A comparison of the geometrical and material mistuning reveals completely different results. In the case of long blades, geometrical mistuning is recommended. The maximal blade stress location changes, depending on the form of mistuning.

Titanium hollow blades are characterized with lightweight and high structural strength, which are widely used in advanced aircraft engines nowadays. Superplastic forming/diffusion bonding (SPF/DB) combined with numerical control (NC) milling is a major solution for manufacturing titanium hollow blades. Due to the shape deviation caused by multiple heat and pressure cycles in the SPF/DB process, it is hard to manufacture the leading and tailing edges by the milling process. This paper presents a new adaptive machining approach using free-form deformation to solve this problem. The actual SPF/DB shape of a hollow blade was firstly inspected by an on-machine measurement method. The measured point data were matched to the nominal SPF/DB shape with an improved ICP algorithm afterwards, by which the point-pairs between the measurement points and their corresponding points on the nominal SPF/DB shape were established, and the maximum modification amount of the final nominal shape was constrained. Based on the displacements between the point-pairs, an accurate FFD volume was iteratively calculated. By embedding the final nominal shape in the deformation space, a new final shape of the hollow blade was built. Finally, a series of measurement and machining tests was performed, the results of which validated the feasibility of the proposed adaptive machining approach.

In the present study, the implementation of multi-blade profiles in a Savonius rotor was evaluated in order to increase the pressure in the blade’s intrados and, thus, decrease motion resistance. The geometric proportions of the secondary element were determined, which maximized the rotor’s performance. For this, the response surface methodology was used through a full factorial experimental design and a face-centered central composite design, consisting of three factors, each with three levels. The response variable that was sought to be maximized was the power coefficient (CP), which was obtained through the numerical simulation of the geometric configurations resulting from the different treatments. All geometries were studied under the same parameters and computational fluid dynamics models through the ANSYS Fluent software. The results obtained through both experimental designs showed a difference of only 1.06% in the performance estimates using the regression model and 3.41% when simulating the optimal proportions geometries. The optimized geometry was characterized by a CP of 0.2948, which constitutes an increase of 10.8% in its performance compared to the profile without secondary elements and of 51.2% compared to the conventional semicircular profile. The numerical results were contrasted with experimental data obtained using a wind tunnel, revealing a good degree of fit.

Tip loss corrections are an important factor in Blade Element Momentum (BEM) theory when determining optimum blade design for maximum power production. This paper presents the optimal tip design using the new tip loss correction. A semi-analytical solution was proposed to find the optimum rotor considering Shen’s new tip loss model. The optimal blade geometry is obtained for which the maximum power coefficient is calculated at different design tip speed and glide ratio. Our simulation is conducted for S809 rotor wind turbine blade type, produced by National Renewable Energy Laboratory (NREL).

Purpose Remanufacturing of worn blades with various defects normally requires processes such as scanning, regenerating a geometrical reference model, additive manufacturing (AM) through laser cladding, adaptive machining and polishing and quality inspection. Unlike the manufacturing process of a new part, the most difficult problem for remanufacturing such a complex surface part is that the reference model adaptive to the worn part is no longer available or useful. The worn parts may suffer from geometrical deformation, distortion and other defects because of the effects of harsh operating conditions, thereby making their original computer aided design (CAD) models inadequate for the repair process. This paper aims to regenerate the geometric models for the worn parts, which is a key issue for implementing AM to build up the parts and adaptive machining to reform the parts. Unlike straight blades with similar cross sections, the tip geometry of the worn tip of a twist blade needs to be regenerated by a different method. Design/methodology/approach This paper proposes a surface extension algorithm for the reconstruction of a twist blade tip through the extremum parameterization of a B-spline basis function. Based on the cross sections of the scanned worn blade model, the given control points and knot vectors are firstly reconstructed into a B-spline curve D. After the extremum of each control point is calculated by extremum parameterization of a B-spline basis function, the unknown control points are calculated by substituting the extremum into the curve D. Once all control points are determined, the B-spline surface of the worn blade tip can be regenerated. Finally, the extension algorithm is implemented and validated with several examples. Findings The proposed algorithm was implemented and verified through the exampled blades. Through the extension algorithm, the tip geometry of the worn tip of a twist blade can be regenerated. This method solved a key problem for the repair of a twist blade tip. It provides an appropriate reference model for repairing worn blade tips through AM to build up the blade tip and adaptive machining/polishing processes to reform the blade geometry. Research limitations/implications The extension errors for different repair models are compared and analyzed. The authors found that there are several factors affecting the accuracy of the regenerated model. When the cross-section interval and the extension length are set properly, the restoration accuracy for the blade tip can be improved, which is acceptable for the repairing. Practical implications The lack of a reference geometric model for worn blades is a significant problem when implementing blade repair through AM and adaptive machining processes. Because the geometric reference model is unavailable for the repair process, reconstruction of the geometry of a worn blade tip is the first crucial step. The authors proposed a surface extension algorithm for the reconstruction of a twist blade tip. Through the implementation of the proposed algorithm, the blade tip model can be regenerated. Social implications Remanufacturing of worn blades with various defects is highly demeaned for the aerospace enterprises considering sustainable development. Unlike straight blades, repair of twist blades encountered a very difficult problem because the geometric reference model is unavailable for the repair processes. This paper proposed a different method to generate the reference model for the repair of a twist blade tip. With this model, repair of twist blades can be implemented through AM to build up the blade tip and adaptive machining to subtract the extra material. Originality/value The authors proposed a surface extension algorithm to reconstruct the geometric model for repair of twist blades.

In this study, analytical calculation and numerical simulations were performed to design a Francis turbine runner blade. Single blade was designed by using Bovet approach. Blade geometry was created by using Ansys Bladegen V16.1. Grid model has been generated by using Ansys Meshing, with using fine mesh quality, tetrahedron type mesh. k-epsilon turbulence model have been selected for steady state analysis. Pressure distributions are obtained on meridional plane and also on suction and pressure sides of the blade. The results of the numerical analysis showed that, Bovet design approach is able to calculate a runner that has an efficiency of 1% different with respect to committed efficiency. At the inlet of the suction side, the negative pressure is observed, that can cause cavitation and oscillation. (C) 2017 The Authors. Published by Elsevier Ltd.

The longitudinal vibration characteristics of the rim driven thruster (RDT) induced by the ingested turbulence are numerically studied and compared with that of the traditional shaft driven propeller (SDP). The pressure spectrum acted on the blade surface is first computed using the correlation method based on strip theory and the statistical characteristics of isotropic turbulence. Appling the computed pressure spectrum as excitation, the random vibration response of the whole immersed thruster is obtained using the mode superposition method. The differences between the vibration responses, especially the longitudinal unsteady thrust transmission characteristics, of the two kinds of propulsors that have the same blade geometry are discussed. Computational results show that though RDT has lower hydrodynamic damping in the lower order bending modes, its resonant amplification on the unsteady thrust is still lower that of SDP for the lower modal force induced by the poor coincidence between the modal shape and space distribution of excitation. A potential merit of traditional SDP is that it has better attenuation effect on the unsteady thrust in the frequency band between the first and second bending modes of the propeller blade.

This paper presents a procedure for static stress analysis of a given shredder blade with three cutting edges used for cutting Polyethylene Terephthalate (PET) waste plastics. SolidWorks was used for generating the blade geometry and shape. This procedure gives detailed steps for calculating the distributed applied cutting forces at the edge of the blade. The blade material is selected to be low carbon steel with known physical and mechanical properties. Finite Element Analysis with ANSYS is then implemented for calculating the induced stresses and strains throughout the blade structure. 3D modeling of the blade was imported to the ANSYS Finite element –type “SOLID 185” was implemented for the present stress analysis. Meshing of the 3D model has been implemented with smart mesh density (level 3) It was found from attained results that the maximum stress resulting from the applied cutting forces is well below the allowable stress of the blade material.

This paper presents a sensitivity analysis on a numerical tidal stream turbine model where a multitude of input parameters’ effect on the load output were determined. The statistical procedure used, known as the Morris method, provided insight into the interactions between the parameters as well as showing their comparative influence on the turbine loading. The investigation covered parameters from the operational, geometric design and inflow variable domains where the rotor radius, current shear, blade root pitch, surface velocity and wave height were identified as most influential. The blade pitch was regarded as a surprisingly prominent influence on the loads. The turbine’s operating depth and the blade geometry were also found to be of limited influence in the ranges investigated. In terms of load transmission into the internal components of a turbine’s drive train, the rotor out-of-plane bending moment, or eccentric bending moment, was found to be a considerable contribution to the off-axis loads on the shaft. Therefore, special attention was paid to the input parameters’ relationship to the eccentric load component by performing a detailed study on the load variations caused by the identified primary input parameters. It is concluded that performing a sensitivity analysis on a tidal stream turbine in a specific operating climate can yield insight to the expected load range and that the eccentric loading transmitted to the shaft is significant for most input cases.

Numerical heat-transfer and turbulent flow model for an industrial high-pressure gas quenching vacuum furnace was established to simulate the heating, holding and gas fan quenching of a low rhenium-bearing Ni-based single crystal turbine blade. The mesh of simplified furnace model was built using finite volume method and the boundary conditions were set up according to the practical process. Simulation results show that the turbine blade geometry and the mutual shielding among blades have significant influence on the uniformity of the temperature distribution. The temperature distribution at sharp corner, thin wall and corner part is higher than that at thick wall part of blade during heating, and the isotherms show a toroidal line to the center of thick wall. The temperature of sheltered units is lower than that of the remaining part of blade. When there is no shelteration among multiple blades, the temperature distribution for all blades is almost identical. The fluid velocity field, temperature field and cooling curves of the single and multiple turbine blades during gas fan quenching were also simulated. Modeling results indicate that the loading tray, free outlet and the location of turbine blades have important influences on the flow field. The high-speed gas flows out from the nozzle is divided by loading tray, and the free outlet enhanced the two vortex flow at the end of the furnace door. The closer the blade is to the exhaust outlet and the nozzle, the greater the flow velocity is and the more adequate the flow is. The blade geometry has an effect on the cooling for single blade and multiple blades during gas fan quenching, and the effects in double layers differs from that in single layer. For single blade, the cooing rate at thin-walled part is lower than that at thick-walled part, the cooling rate at sharp corner is greater than that at tenon and blade platform, and the temperature at regions close to the internal position is decreased more slowly than that close to the surface. For multiple blades in single layer, the temperature at sharp corner or thin wall in the blade that close to the nozzles is much lower, and the temperature distribution of blades is almost parallel. The cooling rate inside the air current channel is lower than that of at the position near blade platform and tenon, and the effect of blade location to the nozzles on the temperature field inside the blade is lower than that on the blade surface. For multiple blades in double layers, the flow velocity is low, and the flow is not uniform for blades in the second-layer due to the shielding of blades in the first-layer. the cooling rate of blades in the second-layer is lower than that in the first-layer. The cooling rate of blade close to the nozzles in the first-layer is the higher than that of blade away from the nozzles in the second-layer, and the temperature distribution on blades in the same layer is almost parallel. The cooling rate in thin wall position of blade away from the nozzles is larger than that in tenon of the blade closer to the nozzles in the same layer. The cooling rate for blades in the second- layer is much lower both in thin wall and tenon for blades away from the nozzles.

This paper presents statistical data about lightning damage on wind turbine blades reported at different wind farms in the U.S. The analysis is based on 304 cases of damage due to direct lightning attachment on the blade surface. This study includes a large variety of blades with different lengths, laminate structure, and lightning protection systems. The statistics consist of the distribution of lightning damage along the blade and classify the damage by severity. In addition, the frequency of lightning damage to more than one blade of a wind turbine after a thunderstorm is assessed. The results of the analysis show that the majority of lightning damage is concentrated at the tip of the blade. Furthermore, all of the blades involved in the study show great similarity in the distribution of damage along the blade and the characteristics of the damages, even concerning the significant differences in the blades' geometry and materials.

A drill bit with polycrystalline diamond (PDC) inserts lost one of its three blades when operating in an oil well, leading to a costly failure. Operating conditions and associated stresses were analyzed, bit core material in the failure and adjacent areas was analyzed and tested, and fracture surfaces identified. Base material is a Ni-Cu-Mn matrix with tungsten carbide precipitates. Fracture surfaces showed cleavage planes and loss of particles, indicating a brittle fracture. Microstructures and hardness were similar in all analyzed regions, and according to specifications. The symmetry and characteristics of the fracture surfaces allow defining that the loads that caused the failure were not applied during the drilling operation. The blade broke apart due to a downward force applied at its base. Finite elements numerical modeling allowed pinpointing a specific moment in the pulling operation, in which a 28 ton overpull force was recorded, as the immediate operational event that caused the failure. Operating procedures that reduce the likelihood and amplitude of impact loads, are difficult to implement; more promising is the alternative for a redesign of the drill bit. Commercial designs focus mostly on the efficiency of the cutting cycle; blade geometry can be also optimized to take into account the pull out conditions. The most efficient redesign for this specific drill bit model relies in a re-machining of the blade base, so that a large overpull load would crack a small sector, on which a PDC insert is located. In this gecko-tail type solution, only one insert would be lost, preserving the integrity of the rest of the drill-bit. Subsequent repair would involve standard thermal spray base metal techniques, including reconstitution and brazing of a new insert. Fil: Cirimello, Pablo Gabriel. YPF - Tecnología; Argentina Fil: Otegui, Luis Jose. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. YPF - Tecnología; Argentina Fil: Sanchez Martinez, Julio. Invap S. E.; Argentina Fil: Carfi, Guillermo Rodolfo. YPF - Tecnología; Argentina

In order to evaluate and improve the efficiency of the process of grinding, various investigations are conducted, based on the relevant research methodology. One of them is the method in which the crushed sample is subjected to single stroke loads. On this basis, the influence of the geometric features of the chipper system and the dynamic process on the efficiency of the grinding is determined. Charpy hammers instrument were used to perform these modifications so that the momentary force of the resistance could be recorded with varying sample alignment, blade geometry changes and others. In addition, it was proposed to use a super fast camera (up to 1200 fps) to record the deformation of the sample and its destruction, in order to interpretation the burdens there. Under such idealized conditions, a range of variables has been identified that significantly affect the reduction of energy demand during grinding.

This paper presents results of crack growth analysis of an aero-engine compressor blade subjected to resonant vibration. In the work an original hybrid method were used for crack dynamic estimation. Proposed procedure connects three methods: analytical, numerical and experimental fatigue analysis of the blade tested in high cycle fatigue conditions. During investigations only first mode of transverse vibration was considered. In first step of analysis the stress intensity factor for the simplified model of blade with half-elliptical crack was calculated using Raju–Newman method. Crack dimensions and crack location were determined on the base of experimental investigations. The bending stress used in Raju–Newman solution was computed for the real blade geometry using the finite element method. Stress intensity factor values were next used as an input data into Paris–Erdogan equation. As a result proposed hybrid analysis, the plot of crack length in function of number of load cycles for the compressor blade vibrating at constant amplitude was determined. Obtained results of simulation were finally compared with the results of the experimental crack growth analysis performed for the first stage compressor blade of helicopter turbo-engine.

A small wind turbine blade was designed and optimized in this research paper. The blade plays an important role, because it is the most important part of the energy absorption system. Consequently, the blade has to be designed carefully to enable to absorb energy with its greatest efficiency. The main objective of this paper is to optimized blade number and selection of tip speed ratio corresponding to the solidity. The power performance of small horizontal axis wind turbines was simulated in detail using blade element momentum methods (BEM). In this paper for wind blade design various factors such as tip loss, hub loss, drag coefficient, and wake were considered. The design process includes the selection of the wind turbine type and the determination of the blade airfoil, twist angle distribution along the radius, and chord length distribution along the radius. A parametric study that will determine if the optimized values of blade twist angle and chord length create the most efficient blade geometry. The 3-bladed, 5-bladed and 7-bladed rotor achieved maximum values of Cp 0.46, 0.5 and 0.48 at the tip speed ratio 7, 5 and 4 respectively. It was observed that using BEM theory, maximum Cp varied with strongly solidity and weakly with the blade number. The studies showed that the power coefficient increases upto blade number B = 5, while the blade number if increased above 5 then the power coefficient decreases at operating pitch angle equal to 3°. Highest Cp would have solidity between 4% to 6% for number of blade 3 and design point tip speed ratio of about "7". Highest Cp would have solidity ranging from 5% to 10% for number of blade 5 and 7 and design point tip speed ratio of about 5 and 4 respectively.

This paper reports the development of a new propeller design and analysis tool. JBLADE uses an improved version of blade element momentum that embeds a new model for the three-dimensional flow equilibrium. In addition, a new method for the prediction of the airfoil drag coefficient at a 90 deg angle of attack for a better poststall modeling is also presented. The software is developed as an open-source tool for the simulation of propellers and has the capability to estimate the performance of a given propeller geometry in design and offdesign operating conditions. The software allows the introduction of the blade geometry as an arbitrary number of sections. To validate the code, the propellers from NACA Technical Report 530 by Gray (“Wind-Tunnel Tests of Two Hamilton Standard Propellers Embodying Clark Y and NACA 16-Series Blade Sections,” 1941) and NACA Technical Report 594 by Theodorsen et al. (“Characteristics of Six Propellers Including the High-Speed Range,” 1937) were simulated and the results were ...

A failure of a first stage compressor blade of a Gas Turbine Generator in a Gas Treatment plant caused severe mechanical damage to the compressor section and power supply troubles. In this paper, the blade failure is investigated by mechanical, metallography and chemical analysis. A finite element analysis is performed on the blade geometry to identify the stress concentration areas and the stress/strain values. The investigation outcomes provided the most probable cause of the premature blade failure and the recommendations to mitigate such incidents.

Strip-tillage research in developing countries usually relies on commonly used rotary blades designed for conventional full disturbance soil tillage. With the aim of optimising the blade geometry and operational settings, this study investigated the effect of three blade geometries (conventional, half-width and straight) at four rotary speeds (125, 250,375, and 500 rpm) on torque, power and energy characteristics. A single row rotary tiller was fitted with the blades set at a cutting width of 50 mm and depth of 50 mm and tested in a soil bin (sandy loam soil). Analyses of high speed video images and corresponding blade motion revealed that the peak torque occurred at a higher blade penetration depth as the speed increased indicating transformation of the peak torque requirement from due to initial soil failure at a low speed to final soil cutting and throwing at a high speed. The straight blade design required the least torque, average power, peak power, specific energy and effective specific energy at 375e500 rpm which targeted for a small bite length for a fine soil tilth. The straight blade saved 20e25% power when compared with the conventional and half-width blades at 500 rpm. Although, the average power, peak power and specific energy requirements increased with the rotary speed for all the blades with a steep rise over 375 rpm, the effective specific energy requirement remained almost unchanged for the straight blade indicating its high effectiveness for strip-tillage operations. Refereed/Peer-reviewed

In September 2015, the DLR completed the first wind tunnel test of its patented Multiple Swashplate System in the DNW's Large Low-Speed Facility in the Netherlands. During these tests, the potential of this new active rotor control system to effectively reduce noise, vibration, and power consumption using several individual blade control strategies, including 2/rev inputs, was successfully demonstrated on two different model rotors without using actuators in the rotating frame. For a Mach-scaled Bo105 model, rotor power reductions of up to 4% in level flight and reductions of the weighted 4/rev vibratory hub loads of up to 77% in a descent flight condition were measured, and BVI noise levels were reduced by up to 4.5 dB by the application of 3/rev higher harmonic control, confirming findings from the HART II test. For the second model rotor using a contemporary blade geometry, the maximum reductions were measured at 3%, 52%, and 3.9 dB for power, vibration, and BVI noise, respectively.

The impact of boundary layer suction on the aerodynamic performance of bowed compressor cascades is discussed in this paper. Preliminary studies are conducted in the context of a highly loaded compressor cascade with peak diffusion factor of 0.60 and camber angle of 60 degrees. Comparison between numerical simulation results and experiment data shows that blade bowing may well help to modify the radial migration of flow features and prevent the blade suction surface boundary layer from separating. It is noteworthy that there exists an optimum blade bowing design with different operating conditions to increase the incidence range and reduce the loss over the incidence range. With the introduction of the boundary layer suction, the blade design becomes more complicated. This paper, therefore, conducts a thorough numerical study on design parameters including bowed blade geometry, aspirated flow fraction, and aspiration slot location based on mechanical simplicity and fabrication constraints. For a better understanding of the flow physics, the aspiration slot and plenum are included as part of the computational domain. The aspirated fluid passes into the plenum and is removed through both the hub and the shroud of the blade. From there it can be dumped overboard or carried to another point in the engine to be used as cooling air. Without considering the stagnation pressure loss of the aspirated flow, the blade lose can be sustainably decreased with the growing aspirated flow fractions from 0.5% to 2.5% of the inlet mass flow. However, when the aspirated flow’s effect on stagnation pressure loss is properly quantified, the blade’s loss decreasing trend will be relatively stable or even reversed with the aspirated flow fraction increasing. The calculations show that the application of aspiration on the flow path needs to be investigated and combined with blade bowing to partly counter the negative impacts with the application of aspiration. The application of blade bowing on aspirated blade makes it possible to achieve the same loss reduction by using lower amounts of aspirated flow. In other words, the increase in spanwise pressure gradient near the endwalls can be further utilized to reduce the effects of secondary flow by bowed blade with the same aspirated flow fraction. Aspiration should not be isolated from blade bowing, the optimum blade bowing angle is different on the basis of different aspirated flow fraction and aspiration slot location. The aspiration slot location is determined by the flow phenomena such as the three-dimensional separation in the cascade corner. In consideration of the stagnation pressure loss from the aspirated flow, aspiration inside of the three-dimensional separation region has a beneficial impact on the blade loss. Conversely, it will quickly lose its effectiveness, or even lead to slight deterioration of the aerodynamic performance if aspiration location is in the midspan, outside the three-dimensional separation region.

Designing blade geometry as a multidisciplinary optimization presents important challenges due to the increment in the number of design variables and computational cost of calculating the constraints and objective function. Blades have an important impact on loads because they capture the kinetic energy in wind and transfer it to the rest of the wind turbine components. Thus, consideration of the fatigue response is necessary in the optimization problem. However, the calculation of the damage equivalent loads (DELs) implies time-consuming simulations that restrict the number of design variables due to the increment of the search space. This article proposes a frequency domain method to estimate the fatigue response, which produces an advantage in terms of computational cost. The method is based on wind turbine model linearization by means of an aero-elastic code and the subsequent calculation of a frequency response function (FRF), which serves to estimate the response of the wind turbine. The Dirlik method is then applied to infer the damage equivalent loads. This process, which is useful for variables that have a stochastic nature, provides rapid approximate prediction of the fatigue response. An alternative estimation is proposed for loads subjected to an important periodic component. The results show that the method is useful in the initial stages of design.

This paper presents the development of a portable vane rheometer to estimate concrete plastic viscosity and yield stress. The apparatus can be used not only in laboratory but also on construction site. In this study, new blade geometry was proposed to minimize the effect of segregation of concrete during testing, and also to expand the wide range of concrete work­ability with a slump of approximately from 7 cm to fluid concrete, and concrete with high plastic viscosity such as concrete with mineral additions. The used blade (U shaped and reversed) allows reducing the vibration of the apparatus, and ob­taining more stable measurements. The obtained results permit validating the rheometer test procedure and confirmed that the results are reliable, with a low coefficient of variation of 9% for repetitive test and of 5.8% for reproductive tests. First published online:23 Jun 2016

This paper presents an integrated methodology for the analysis of operationally-used turbine blades, incorporating aerodynamic and multiple structural simulations. In jet engines, blade rubbing and erosion lead to deviations of the blade geometry. The presented functional simulations are conducted in order to predict the influence of wear on the performance of turbine blades based on these geometric variations. A numerical simulation of the investigated turbine blades using CFD show the change of aerodynamic performance and the flow field due to wear. Additionally, the deviations of the blade geometry lead to a different pressure and temperature distribution on the blade surface, which is used as input for the structural simulations. The change in geometry, surface pressure and temperature lead to a change in vibration behavior of the blade. Particularly the eigenfrequencies and excitation are affected. This is incorporated into the analysis by performing a structural vibration simulation of a complete bladed disk, using component mode synthesis and wave base substructuring. The mistuning effects are analyzed statistically using the Monte Carlo method. The change in vibration amplitudes influences crack opening and closing for a single blade under thermo-mechanical load. These processes, including thermal expansion, are investigated using the extended finite element method. Two real turbine blades are used to compare the characteristics of a new and a used blade.

One of the challenging aspects of radial turbine design and manufacturing is vibration and stability. Rotordynamic analysis was performed on a rotor-bearing system of a 1 kWe radial inflow turbine. The objective of rotordynamic analysis is to determine suitable system configuration for stable operation in the design process. The rotor and blade design were previously developed using ANSYS Structural module which provides the mass and inertia of the complex blade geometry for the rotordynamic analysis. A simulation model with concentrated mass and inertia was built for the rotating structure using ANSYS Parametric Design Language (APDL). Modal and mass unbalance response analyses were carried out with six cases having different shaft diameters and bearing arrangements. The best case was chosen for further parametric study of the effects of shaft length, blade residual unbalance, and bearing stiffness on the blade displacement amplitude. Blade clearance was then set to determine acceptable shaft length, bearing arrangement, blade unbalance quality, and bearing stiffness.

This study looks at the design of a 100 kW blade geometry for a horizontal marine current turbine using the Blade Element Momentum Theory (BEMT) and by using (CFD), the power output, performance and characteristics of the the fluid flow over the blade is estimated. Three basic airfoils; FFA-W3-301, DU-93-W210 and NACA-63418, are used along the blade span and The distribution of the chord length and twist angles along the blade are obtained from the hydrodynamic optimization procedure. The power coefficient curve shows maximum peak at the rated tip speed ratio of 5.17, and the maximum power reaches about 101.82 kW at the power coefficient of 0.495.

For a centrifugal fan impeller the blade shape can be defined using two parameters: the blade angle and the blade width. There are different design methods depending on the assumption made on both the blade width and the blade angle. In this paper four design methods are presented: constant blade width and variable blade angle; hyperbolic blade width and variable blade angle; hyperbolic blade width and constant blade angle; linear blade width and variable blade angle. The sequential algorithm for solving the characteristic system of equations, which defines the blade geometry, is implemented in a MATLAB script file, for which principal code lines are explained. In the solving process of the characteristic system of equations for all four design methods considered, different relationships for relative velocity are obtained. The comparative graphical analysis of impeller blades obtained by all of the four design methods, as well as the blade geometry parameters is presented.

The study concentrates on the shape design and numerical analysis of a 1 MW horizontal axis tidal current turbine (HATCT), which can be applied near the southwest regions of Korea. On the basis of actual tidal current conditions of south-western region of Korea, configuration design of 1 MW class turbine rotor blade is carried out by blade element momentum theory (BEMT). The hydrodynamic performance including the lift and drag forces, is conducted with the variation of the angle of attack using an open source code of X-Foil. The optimized blade geometry is used for Computational Fluid Dynamics (CFD) analysis with hexahedral numerical grids. This study focuses on developing a new hydrofoil and designing a blade with relatively shorter chord length in contrast to a typical TCT blade. Therefore, after a thorough study of two common hydrofoils, (S814 and DU-91-W2-250, which show good performance for rough conditions), a new hydrofoil, MNU26, is developed. The new hydrofoil has a 26% thickness that can be applied throughout the blade length, giving good structural strength. Power coefficient, pressure and velocity distributions are investigated according to Tip Speed Ratio by CFD analysis. As cavitation analysis is also an important part of the study, it is investigated for all the three hydrofoils. Due to the shorter chord length of the new turbine blade in contrast to a typical TCT blade design, a Fluid Structure Interaction (FSI) analysis is also done. Concrete conclusions have been made after comparing the three hydrofoils, considering their performance, efficiency, occurrence of cavitation and structural feasibility.

The application of laser cladding technology is becoming widely extended in the industrial environment due to its advantages of high added value and direct manufacturing or repair of complex parts. These complex parts require 5-axis laser cladding deposition processes whose programming demands optimized and continuous tool paths. The present work develops a programming methodology for a homogeneous material deposition of a continuous 5-axis laser cladding process applied to rapid manufacturing of blisk blades. Initially, the blisk blade geometry is defined and the process requirements are studied considering key factors such as the best parameters, nozzle trajectories, and feed values. Therefore, the proposed algorithm solution for feed variation control is applied to the process obtaining a more homogeneous structure. Finally, a blisk case study is developed according to the proposed solutions.

Improvements in the aerodynamic design will lead to more efficiency of wind turbines and higher power production. In the present study, a 3D parametric gas turbine blade geometry building code, 3DBGB, has been modified in order to include wind turbine design capabilities. This approach enables greater flexibility of the design along with the ability to design more complex geometries with relative ease. The NREL NASA Phase VI wind turbine was considered as a test case for validation and as a baseline by which modified designs could be compared. The design parameters were translated into 3DBGB input to create a 3D model of the wind turbine which can also be imported into any CAD program. Design modifications included replacing the airfoil section and modifying the thickness to chord ratio as a function of span. These models were imported into a high-fidelity CFD package, Fine/TURBO by NUMECA. Fine/TURBO is a specialized CFD platform for turbo-machinery analysis. A code-geomturbo was used to convert the 3D model of the wind turbine into the native format used to define geometries in the Fine/TURBO meshing tool, AutoGrid. The CFD results were post processed using a 3D force analysis code. The radial force variations were found to play a measurable role in the performance of wind turbine blades. The radial component of the blade surface area as it varies in span is the dominant contributor of the radial forces. Through the radial momentum equation, this radial force variation is responsible for creating the streamline curvature that leads to the expansion of the streamtube (slipstream) that is responsible for slowing the wind velocity ahead of the wind turbine leading edge, which is quantified as the axial induction factor. These same radial forces also play a role in changing the slipstream for propellers. Through the design modifications, simulated with CFD and post-processed appropriately, this connection with the radial component of area to the radial forces to the axial induction factor, and finally the wind turbine power is demonstrated. The results from the CFD analysis and 3D force analysis are presented. For the case presented, the power increases by 5.6% due to changes in airfoil thickness only.

To acquire the digital model of axial compressors on the actual projects, a Reverse Engineering procedure of the blade which has high accuracy and efficiency based on Parametric Modeling was developed. To meet the requirements of geometric characteristics and aerodynamic optimization design and accuracy of overall blade, a method of blade-measuring path planning based on curves of cross sections and blade body surfaces was presented. For solving the problems of difficulty in the definition and fitting in primary parametric surfaces and connections between them, a parametric surface definition method of typical axial compressors blade based on blade geometry was presented and the connections were fit with a process of primary parametric surface boundary-splicing surface generation. Finally, an example of Reverse Engineering for blades of axial flow compressors based on parameterization was given.

The high-skewed and/or composite propellers of current interests to reduce the ship vibration and to increase the acoustic performance are likely to be exposed to the unexpected structural problems. One typical example is that the added mass effect on the propellers working in the non-uniform wake field reduces the natural frequency of the propeller leading to the resonance with the low-frequency excitation of the external forces. To avoid this resonance problem during the design stage, the technique of fluid-structure interaction has been developed, but the higher-order effect of the blade geometry deformation is not yet considered in evaluating the added mass effects. In this paper the fluid boundary-value problem is formulated by the potential-based panel method in the inviscid fluid region with the velocity inflow due to the body deformation, and the structural response of the solid body under the hydrodynamic loading is solved by applying the finite element method which implements the 20-node iso-parametric element model. The fluid-structure problem is solved iteratively. A basic fluid-sturcture interaction study is performed with the simple rectangular plates of thin thickness with various planform submerged in the water of infinite extent. The computations show good correlation with the experimental results of Linholm, et al. (1965).

It has been shown in several cases that casing treatments can improve the surge margin of a compressor. The question that is often left unanswered when designing and optimizing a casing treatment for a given compressor stage is whether the casing treatment can still improve the performance and surge margin when used on an aerodynamically improved rotor. The current work includes the influence of the rotor geometry and casing geometry in the analysis. Several optimizations with equal objectives, to improve surge margin and efficiency, were performed. First the different components were optimized separately. The possible impact of optimizing the rotor, the casing geometry and the casing treatment on surge margin and efficiency are compared in terms of global performance and aerodynamic effects. It is then analyzed how combinations of optimized geometries perform. Of particular interest is how the circumferential grooves perform when used in combination with the optimized blade geometry. The optimizations were performed using state of the art CFD and optimization procedures. Constraints on boundary conditions, mass flow rates and stresses were applied in order not to change the behavior of the compressor at design point significantly or to deteriorate the structural mechanics.

In this work, the design and the analysis of the performance of an improved tip loaded propeller geometry are proposed. Based on the experimental data and on the numerical results collected at SISTEMAR and at the University of Genoa in the case of Contracted and Tip Loaded (CLT) propellers, a new tip loaded propeller geometry is devised in order to mitigate some of the downsides of the CLT geometries increasingly adopted to improve full-scale propeller efficiency. The modified tip loaded propeller, i.e. a mix between a tip rake and a Contracted and Tip Loaded propeller, is designed via an optimization strategy using a Boundary Elements Method (BEM), a custom parametric description of the unconventional blade geometry and an optimization algorithm (of genetic type) within the modeFRONTIER environment. The reliability of the design process and of the improvements achievable with the modified tip loaded propeller are extensively verified with dedicated RANSE calculations. At first, the accuracy of the BEM, adopted for the design by optimization, is verified in terms of predicted propeller performance in order to assess its applicability for the analysis of modified tip geometries and check its confidence with respect to the allowable modifications of the blade shape. As a second step, viscous calculations are adopted to confirm the improvements of the newly designed geometries, in terms of both cavitation and predicted velocity field downstream the propeller, as a result of a better adaptation of the end plate geometry to the incoming flow. Finally, a set of unsteady calculations, by using the unsteady BEM, is carried out to verify the amplitude of the induced pressure pulses and, by comparing these numerical results with the available measurements and calculations in the case of a reference CLT propeller, to confirm the effectiveness of the modified propeller tip shape.

Tidal turbine rotor blade fractures and failures have resulted in substantial damage and hence cost of repair and recovery. The present work presents a rotor blade design and optimization method to address the blade structural strength design problem. The generic procedure is applicable to both turbine rotors and propellers. The optimization method seeks an optimum blade thickness distribution across the span with a prescribed constant safety factor for all the blade sections. This optimization procedure serves two purposes: while maintaining the required structural strength and integrity for an ultimate inflow speed, it aims to reduce the material to a minimum and to maintain power generation efficiency or improve the hydrodynamic efficiency. The value of the chosen minimum safety factor depends on the actual working conditions of the turbine in which the sectional peak loading and frequency are used: the harsher the environment, the larger the required safety factor. An engineering software tool with both hydrodynamic and structural capabilities was required to predict the instantaneous loading acting on all the blade sections, as well as the strength of a local blade section with a given blade geometry and chosen material. A time-domain, 3D unsteady panel method was then implemented based on a marine propeller software tool and used to perform the optimization. A 3-blade 20-m tidal turbine that was prototyped in parallel with the current work for the Bay of Fundy was used as an example for optimization. The optimum thickness distribution for a required safety factor at the ultimate possible inflow speed resulted in 37.6% saving in blade material. The blade thickness and distribution as a function of a maximum inflow speed of 6 m/s is also presented. The blade material used in the example was taken as nickel–aluminium–bronze (NAB) but the procedure was developed to be applicable to propeller or turbine blades of basically any material.

The boring of valve seats of internal combustion engines is done approximately 25 million times per year in Brazil. Excessive vibrations during this operation are common and can adversely affect dimensional and geometrical tolerances of the valve seats. The sealing of the combustion chamber is prejudiced, resulting in loss of power and higher emission of pollutant gases, harming the environment. The raw material of the valve seats is sintered steel of 370–410 HB hardness and is machined with expensive polycrystalline cubic boron nitride blades. In order to avoid the generation of excessive vibration or chatter during machining, operators reduce cutting speed and feed rate, which consequently causes reduction of productivity. In this context, investigation of the process was performed with the objective of minimizing the vibrations during the valve seat boring through changes in the tool holder design and in geometry of the cutting blades. The proposed modifications resulted in a remarkable reduction in magnitude of the resultant cutting force, vibrations, and roundness deviations of the valve seat. Hence, the sealing between the valve and the seat was improved and the emission of gases from the motor could be reduced, with gains in efficiency. The results also showed that the cutting blade edge must have a 60-μm honing, and the best cutting parameters are in the range: cutting speed 80–100 m/min and feed rate 0.04–0.08 mm/rev/tooth.

Advanced composite structures are becoming increasingly popular because of their high specific strength and stiffness, as well as ability to provide improved performance through passive morphing via intrinsic bend–twist deformation coupling. Self-adaptive composite structures tend to be more susceptible to geometric, material, and loading uncertainties because of their complex configuration, manufacturing process, and dependence on fluid–structure interaction (FSI) response. The objective of this work is to quantify the effects of material, geometric, and loading uncertainties on the response of self-adaptive composite propellers and overall system reliability. A fully-coupled, 3-D boundary element method–finite element method is used to compute the dynamic FSI response. Variability in propeller performance is estimated by considering variations in operating conditions, as well as blade geometry and stiffness. Modeling uncertainties are considered by employing various mechanistic-based failure initiation models. Random variations in material strengths are implemented and an estimate of the structural reliability is determined. The results indicate that adaptive composite structures that depend on FSI are more sensitive to natural, random variations than equivalent rigid, isotropic structures. Therefore, it is necessary to quantify the effects of material, geometric, and loading uncertainties on the responses, safe operating envelopes, and reliability of self-adaptive composite structures.

This paper evaluates the effect of two experimental parameters, namely microvise blade geometry and blade separation, on the scatter in measured interfacial strength in microbond experiments, with the help of two-dimensional (2D) and three-dimensional (3D) finite element models. The 3D model better captures the ‘exact’ loading nature of the problem as compared to the 2D model but it is computationally intensive. Stress distributions obtained by finite element analysis are compared with those from the shear-lag model often used to analyze microbond experiments. This comparison determines the effectiveness of using shear-lag analysis in microbond experiments and for explaining the reasons for commonly observed data scatter.

SUMMARY Prebending of wind turbine blades constitutes a viable engineering solution to the problem of tower clearance, that is, ensuring that during wind turbine operation there is sufficient distance between the rotor blades and the tower to avoid collision. The prebent shape of the blade must be such that when the turbine rotor is subjected to wind and inertial loads, the blades are straightened into their design configuration. In this paper, we propose a method for accurate prediction of the prebent shape of wind turbine blades. The method relies on a stand-alone aerodynamics simulation that provides the wind loads on a rigidly spinning rotor, followed by a series of structural mechanics simulations to determine the stress-free prebent shape of the blade. This procedure involves only one-way coupling between the fluid and structural mechanics, which avoids the challenges of solving the coupled fluid–structure interaction problem. The proposed methodology, which has no limitations on the blade geometry and structural modeling, is successfully applied to prebending of a 63-m offshore wind turbine blade. Copyright © 2011 John Wiley & Sons, Ltd.

This contribution deals with the design of cross flow water turbines. The mechanical stress sustained by the blades depends on the basic geometrical specifications of the cross flow water turbine, its rotational speed, the exact geometry of the blades and the velocity of the upstream water current. During the operation, the blades are submitted to severe cyclic loadings generated by pressure field's variation as function of angular position. This paper proposes a simplified design methodology for structural analysis of cross flow water turbine blades, with quite low computational time. A new trapezoidal-bladed turbine obtained from this method promises to be more efficient than the classical designs. Its most distinctive characteristic is a variable profiled cross-section area, which should significantly reduce the intensity of cyclic loadings in the material and improve the turbine's durability. The advantages of this new geometry will be compared with three other geometries based on NACA0018 hydrofoil.