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1
Balalaiev, Anton, Kateryna Balalaieva, Maryna Pikul e Grygoriy Golembiyevskyy. "Власні частоти коливань композитної решітчастої дворядної лопатки вентилятора ТРДД". Aerospace Technic and Technology, n. 4 (29 agosto 2024): 49–57. http://dx.doi.org/10.32620/aktt.2024.4.06.
Testo completoAbstract (sommario):
The subject of this study is the natural oscillations of a grid tandem fan blade of a turbofan engine. The object of this study was a tandem grid fan blade. The purpose of this work was to assess the influence of the material on the natural frequencies of the oscillations of a grid tandem fan blade of a turbofan engine. The following tasks were set and solved in the work: conducting a modal analysis of the natural oscillations of a grid tandem fan blade made of a composite material and titanium alloy; construction of a Campbell diagram for a grid tandem fan blade made of a composite material and titanium alloy. The study of the natural oscillations of a fan blade was carried out using a numerical experiment. The natural frequency was obtained for the first ten harmonics. Results: Blades made of Ti-6Al-4V titanium alloy and Epoxy Carbon Woven (395 GPa) Prepreg composite material were studied. Studies have shown that the material selection affects the frequency and mode of the oscillations. For both investigated variants of the grid tandem blades, harmonics exist at which intersections between the first and second blades. The composite grid tandem fan blade has fewer harmonics with the phenomenon of crossing the first and second blade. Campbell diagrams were constructed for the grid tandem fan blades. A grid tandem blade made of a composite material has two, and from a titanium alloy, four resonant frequencies in the range of rotor operating speeds from 2000 rpm. up to 3500 rpm. The weight of the studied composite blade was approximately 5 kg, while the blade made of titanium alloy weighed 15 kg. These studies have shown that a composite grid tandem blade has better characteristics, but the design of such a fan blade row requires improvement. The scientific novelty and practical significance of the conducted research lies in the fact that new data were obtained on the natural oscillations of the grid tandem fan blades of a turbofan engine made of a composite material and a titanium alloy. The obtained data will help to create promising gas turbine engines with improved characteristics.
2
Bohn, D. E., e N. Moritz. "Algebraic method for efficient adaption of structured grids to fluctuating geometries". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 219, n. 4 (1 giugno 2005): 303–14. http://dx.doi.org/10.1243/095765005x7619.
Testo completoAbstract (sommario):
An efficient method for adaption of a structured grid to fluctuating turbine blade geometry is presented based on an algebraic algorithm. The objective of the application of this method is to analyse the aerodynamic, thermal and rotational load of rotating and cooled blades with a conjugate approach. The grid adaption method is validated with two test cases by using a simple deformation model considering the blade as a torsion spring. This model ensures a strong coupling between aerodynamic load and deformation of the blades. Thus, the stability of the numerical code can be analysed. The calculations show that convergence for the blade deformation is reached very soon. Even for great blade deformation the algebraic grid adaption method generates no negative cell volumes although this cannot be guaranteed by an algebraic algorithm.
3
Procházka, Pavel, Václav Uruba, Luděk Pešek e VÍtězslav Bula. "On the effect of moving blade grid on the flow field characteristics". EPJ Web of Conferences 180 (2018): 02086. http://dx.doi.org/10.1051/epjconf/201818002086.
Testo completoAbstract (sommario):
The motivation of this paper is the continual development of the blades for the last stage of the steam turbine. The biggest problem is the slenderness of such blades and the extreme sensitivity to aeroelastic vibrations (flutter) caused by the instabilities present in the flow. This experimental research is dealing with the aeroelastic binding of the moving blades located in the blade grid with the flow field and vice versa. A parallelogram is used to ensure one order of freedom of the blade. The grid has five blades in total, three of them are driven by force control using three shakers. The deviation as well as force response is measured by strain gauges and dynamometers. The flow field statistical as well as dynamical characteristics are measured by optical method Particle Image Velocimetry. The grid is connected to the blow-down wind tunnel with velocity range up to 40 m/s. The aeroelastic binding is investigated in dependency on used actuation frequency and maximal amplitude (the intensity of force actuation) and on different Reynolds numbers. The flow field and the wake behind each individual blade are studied and the maximal interaction is examined for individual inter-blade phase angle of the grid.
4
Tuncer, I. H., S. Weber e W. Sanz. "Investigation of Periodic Boundary Conditions in Multipassage Cascade Flows Using Overset Grids". Journal of Turbomachinery 121, n. 2 (1 aprile 1999): 341–47. http://dx.doi.org/10.1115/1.2841320.
Testo completoAbstract (sommario):
A Navier–Stokes solution method with overset grids is applied to unsteady multipassage cascade flows, and the unsteady blade loadings are compared against the single-passage solutions with the direct store interblade boundary condition. In the overset grid solutions, the multipassage domain is discretized with O-type grids around each blade and a rectangular background grid. Blade grids are allowed to move in time relative to the background grid, as prescribed by the oscillatory plunging motion. The overset grid method uses a simple, robust numerical algorithm to localize moving intergrid boundary points and to interpolate solution variables across grids. Computational results are presented for two and four-passage, subsonic and transonic flows through a turbine and a compressor cascade. The overset grid solutions over the multipassage periodic domains agree well with the single-passage solutions and the experimental data. It is concluded that the time linearization error introduced by the direct store approach is negligible in the range of flow conditions studied.
5
Zadeh, Saman Naghib, Matin Komeili e Marius Paraschivoiu. "MESH CONVERGENCE STUDY FOR 2-D STRAIGHT-BLADE VERTICAL AXIS WIND TURBINE SIMULATIONS AND ESTIMATION FOR 3-D SIMULATIONS". Transactions of the Canadian Society for Mechanical Engineering 38, n. 4 (dicembre 2014): 487–504. http://dx.doi.org/10.1139/tcsme-2014-0032.
Testo completoAbstract (sommario):
Mesh resolution requirements are investigated for 2-D and 3-D simulations of the complex flow around a straight-blade vertical axis wind turbine (VAWT). The resulting flow, which may include large separation flows over the blades, dynamic stall, and wake-blade interaction, is simulated by an Unsteady Reynolds-Averaged Navier–Stokes analysis, based on the Spalart-Allmaras (S–A) turbulence model. A grid resolution study is conducted on 2-D grids to examine the convergence of the CFD model. Hence, an averaged-grid residual of y+ > 30 is employed, along with a wall treatment, to capture the near-wall region’s flow structures. Furthermore a 3-D simulation on a coarse grid of the VAWT model is performed in order to explore the influence of the 3-D effects on the aerodynamic performance of the turbine. Finally, based on the 2-D grid convergence study and the 3-D results, the required computational time and mesh to simulate 3-D VAWT accurately is proposed.
6
Marin, Ambroise, Emmanuel Denimal, Stéphane Guyot, Ludovic Journaux e Paul Molin. "A Robust Generic Method for Grid Detection in White Light Microscopy Malassez Blade Images in the Context of Cell Counting". Microscopy and Microanalysis 21, n. 1 (16 dicembre 2014): 239–48. http://dx.doi.org/10.1017/s1431927614013671.
Testo completoAbstract (sommario):
AbstractIn biology, cell counting is a primary measurement and it is usually performed manually using hemocytometers such as Malassez blades. This work is tedious and can be automated using image processing. An algorithm based on Fourier transform filtering and the Hough transform was developed for Malassez blade grid extraction. This facilitates cell segmentation and counting within the grid. For the present work, a set of 137 images with high variability was processed. Grids were accurately detected in 98% of these images.
7
Abdullah, Bestoon, Vadim Varsegov e Adolf Limansky. "CENTRIFUGAL COMPRESSOR HEAD CHARACTERISTIC OF A MICRO TURBOJET ENGINE BASED ON NUMERICAL SIMULATION". Perm National Research Polytechnic University Aerospace Engineering Bulletin, n. 62 (2020): 5–11. http://dx.doi.org/10.15593/2224-9982/2020.62.01.
Testo completoAbstract (sommario):
Shown the possibility of using the standard ANSYS CFX hydrodynamic software package for calculating the gasdynamic characteristics of the centrifugal compressor impeller of micro turbojet engines with different options for profiling blades which based on physical and numerical modeling. Presented a methodology for designing the impeller of a centrifugal compressor based on solving the inverse problem of gas dynamics. As a result of a numerical study, the head coefficient of various forms of the impeller was obtained and presented the dependences of the head coefficient and efficiency on the blade back sweep angle 2 β . b The article discusses the effect of the blade back sweep angle 2 β b on the compressor efficiency and the head characteristic for three different values of the blade back sweep angle 2 β b for example, the impeller with the back sweep angle 2 β b and with the radial blades 2 β 90 b and with blades bent forward 2 β b The centrifugal compressor was designed using Vista CCD programs in one-dimensional computing and Fluid flow CFX in three-dimensional computing. For blade profiling, the BladeGend program was used with different profiling options in order to improve compressor efficiency. The computational grid and the construction of a structured hexahedral mesh for the impeller was carried out in Ansys Turbogrid and the SST model of turbulence was selected in the calculation, which, with sufficient grinding of the mesh at the walls, adequately simulates separated flows at the channel walls, as well as the flow in the flow core. When constructing a grid along the walls between the channel blades, the parameter y + was controlled, which should not exceed 2. It is permissible to use a coarser grid in the flow core compared to the grid near the walls. The design grid of the impeller consists of 350000 elements.
8
Vershkov, V. A., B. S. Kritsky e R. M. Mirgazov. "FEATURES OF MODELING THE FLOW AROUND THE HELICOPTER MAIN ROTOR TAKING INTO ACCOUNT ARBITRARY BLADES MOTION". Civil Aviation High TECHNOLOGIES 22, n. 3 (29 giugno 2019): 25–34. http://dx.doi.org/10.26467/2079-0619-2019-22-3-25-34.
Testo completoAbstract (sommario):
The article considers the problem of the flow around the helicopter main rotor taking into account blades flapping in the plane of rotation and in the plane of thrust as well as the elastic blades deformation. The rotor rotation is modeled by the method of converting Navier-Stokes equations from a fixed coordinate system associated with the incoming flow into a rotating system associated with the rotor hub. For axial flow problems, this makes it possible to formulate the problem as stationary at a constant rotational speed of rotor. For a mode of skewed flow around the rotor in the terms of incident flow in this system it is necessary to solve the non-stationary problem. To solve the problem, the method of deformable grids is used, in which the equations are copied taking into account the grid nodes motion determined in accordance with the spatial blades motion, and SST turbulence model is used for closure. The results of the test calculations of the main rotor aerodynamic characteristics with and without blade flapping are presented in this paper. The coefficients of the main rotor thrust cT and the blades hinge moments mh are compared. The calculations were carried out in the CFD software ANSYS CFX (TsAGI License No. 501024). The flow around a four-bladed main rotor of a radius of 2.5 meters is modeled in the regime of skewed flow. The speed of the incoming flow came to 85 m/s under normal atmospheric conditions. The rotor was at an angle of attack of −10˚. To calculate the rotor motion without taking into account the flapping movements, we used the nonstationary system of Navier-Stokes equations with the closure with SST turbulence model. The calculation was being carried out until the change in the maximum value of the rotor thrust during one revolution became less than 1%. For modeling flapping blade movements, the control laws and equations describing the angle of blade flapping as a function from its azimuth angle obtained from the experiment were used. The procedure for reconstructing the grid according to a given law was conducted using standard grid deformation methods presented in the ANSYS CFX software. When solving the nonstationary Navier-Stokes equations, a dual time step was used. The obtained results show that accounting of the effect of flapping movements and cyclic control of the blades has an impact on the character of changing the main rotor thrust coefficient during one revolution and significantly changes the shape of the graph of the hinge moment coefficient of each blade.
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Bahaghighat, Mahdi, e Seyed Motamedi. "Vision inspection and monitoring of wind turbine farms in emerging smart grids". Facta universitatis - series: Electronics and Energetics 31, n. 2 (2018): 287–301. http://dx.doi.org/10.2298/fuee1802287b.
Testo completoAbstract (sommario):
Todays, Smart Grids as the goal of next generation power grid system span wide and new aspects of power generation from distributed and bulk power generators to the end-user utilities. There are many advantages to develop these complex and multilayer system of systems such as increasing agility, reliability, efficiency, privacy, security for both Energy and ICT sections in smart grid architecture. In emerging smart grids, the communication infrastructures play main role in grid development and as a result multimedia applications are more practical for the future power systems. In this work, we introduce our method for monitoring and inspection of Wind Turbine (WT) farms in smart grids. In our proposed system, a thermal vision camera is embedded on a wireless sensor node for each WT to capture appropriate images and send video streams to the coordinator. It gets video frames to perform machine Vision Inspection (VI) and monitoring purposes. In our constructed model, turbine blade velocity estimation is targeted by detecting two important landmarks in the image that are named hub and blade. By tracking the blade in the consecutive frames and based on proposed scoring function, we can estimate the velocity of the turbine blade. Obtained results clearly indicate that accurate hub and blade positions extraction lead to error free estimation of turbine blade velocity.
10
Li, Xue Feng, Xiu Quan Huang e Chao Liu. "Numerical Simulation Method for Fluid-Structure Interaction in Compressor Blades". Applied Mechanics and Materials 488-489 (gennaio 2014): 914–17. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.914.
Testo completoAbstract (sommario):
A simulation method for fluid-structure interaction (FSI) in compressor blades was discussed to predict the aeroelastic stability of blades. Using the MFX, which is a Multi-Field Solver in ANSYS, the total force of computational fluid dynamics (CFD) have been interpolated to computational structural dynamics (CSD) grids, and then the vibration displacements of CSD nodes have been interpolated to CFD grids at the blade surface. In CFD analysis, the grid coordinates of the moveable region have been updated by multi-layer moving grid technique, and the finite volume method has been applied to calculate the Reynolds-averaged Navier-Stokes (RANS) equations closed by k-E turbulent model. For NASA Rotor 67, detect the displacement response of compressor blades at the design speed , and the aeroelastic stability of blades has been analyzed preliminarily. The study shows that the FSI procedure is feasible to predict the aeroelastic stability of compressor blades.
11
Xue, Dang Qin, De Yong Lv, Jia Xi Zhang e Shu Lin Hou. "The Optimization on Grid Division Methods of Blade Pump Blades Based on CFD". Applied Mechanics and Materials 635-637 (settembre 2014): 35–39. http://dx.doi.org/10.4028/www.scientific.net/amm.635-637.35.
Testo completoAbstract (sommario):
Grid division is the geometric expression forms and vectors of CFD numerical simulation engineering problems. The quality of the grid has an important impact on the CFD accuracy and computational efficiency about CFD. In this paper, it compares the structured and non-structured grid process summary base on blade pump. During a large number of mechanical fluid grid division and performance calculations, and combining with the theoretical guidance based on rotating machinery fluid Dynamics calculations, it summarizes some experience and practice on blades grid division optimization.
12
Vershkov, V. A. "ALGORITHM OF MESH DEFORMATION FOR ACCOUNTING CYCLIC BLADE CONTROL AND BLADES FLAPPING IN THE PROBLEM OF HELICOPTER MAIN ROTOR MODELING". Civil Aviation High TECHNOLOGIES 22, n. 2 (24 aprile 2019): 62–74. http://dx.doi.org/10.26467/2079-0619-2019-22-2-62-74.
Testo completoAbstract (sommario):
This paper presents the developed algorithm for numerical grid deformation for solving the problems of modeling the flow around the helicopter main rotor in the horizontal flight mode with allowance for flapping movements and cyclic changes in the angle of the blade installation. In general, this algorithm can be applied to simulate the aerodynamics of solid bodies deviating from its initial position at angles up to 90 degrees in the vertical and horizontal planes relative to the origin point, and also performing a rotational motion at an angle up to 90 degrees around the axis through the center of coordinates and the body mass center. The first part provides a brief overview of the existing methods of the computational grid deformation for solving various problems of numerical simulation. These include methods for rebuilding the grid, moving grids and "Chimera" grids. The second part describes the algorithms for allocating of grid deformation and for finding the final coordinate of the computational grid nodes in the presence of a predetermined blade control law. The equations of the deformation zones shape in numerical grid are given. The influence of variables on zones sizes is shown. The third part presents the results of methodological calculations confirming the performance and limitations when choosing mesh deformation zones. The influence of the size and shape of the deformation zones of the numerical grid on the quality of the mesh elements is also shown. This work is methodical in nature and is a preliminary stage in the numerical modeling of the flow around the helicopter main rotor taking into account the automatic main rotor balancing and blades flapping.
13
Yang, Wei Min, Wen Juan Bai, Min Min Du e Ti Kun Shan. "The Meshing of the Fan Blade of Scenery Tower Power Generation Device". Key Engineering Materials 561 (luglio 2013): 688–91. http://dx.doi.org/10.4028/www.scientific.net/kem.561.688.
Testo completoAbstract (sommario):
Usually wind turbine blade number is less, and blade is longer,and which speed is commonly 10-30 r/min,while the miniaturization of scenery tower power generation device of fan blade is not. The device adopts eight blades according to the similarity theory between the wind machine and the steam turbine. By changing its speed can still achieve the transfer of energy and then generate electricity,although blade is short, and the wind area is reduced.In the study of the blade,high quality grid is the key.This paper discusses the fan blade meshing used ICEM CFD in the rotation of the basin.
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Popova, Diana, Denis Popov e Nikita Samoylenko. "INVESTIGATION OF THE GRID MODEL AND TURBULENCE MODEL PARAMETERS INFLUENCE ON QUALITY OF TURBINE ROTOR BLADE TIP CLEARANCE AREA AERODYNAMIC PROCESSES MODELING". Perm National Research Polytechnic University Aerospace Engineering Bulletin, n. 66 (2021): 67–78. http://dx.doi.org/10.15593/2224-9982/2021.66.07.
Testo completoAbstract (sommario):
Aerodynamic processes mathematical modeling is carried out using numerical methods. Now the level of development of software numerical methods of three-dimensional gas-dynamic modeling of processes in turbomachinery makes it possible to determine with high accuracy the main characteristics of units at the design stage. It significantly reduces the time and cost of production. This article proposes a methodology for installation and improving the mathematical and grid model of HPT rotor blade to improve the quality of three-dimensional modeling. Aerodynamic processes mathematical modeling in aircraft turbojet engine blade rows is carried out using numerical methods. Grid model settings and turbulence model significantly affect the results qualitative characteristics and the calculations duration. This article proposes a methodology for grid model constructing based on local intense vortex formation and flow mixing places thickening. The influence of the grid and turbulence models parameters are estimated on the kinetic energy losses amount and secondary flows structure. The design model includes the building geometric model, preparation of the grid model and description of the turbulence model. Influence of grid and BSL and SST turbulence models on results of turbine blade aerodynamic calculation is considered in this article. Basic recommendations for the construction of mathematical and grid models in the ANSYS for uncooled rotor blades have been developed.
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., Sutrisno, Setyawan Bekti Wibowo e Sigit Iswahyudi. "Numerical Research on the Vortex Center on the Forward-Swept 3-D Wind Turbine Blades at Low Rotational Speed". Modern Applied Science 12, n. 12 (16 novembre 2018): 80. http://dx.doi.org/10.5539/mas.v12n12p80.
Testo completoAbstract (sommario):
This paper studies the CFD simulation of forward three-dimensional (3-D) horizontal axis wind turbine (HAWT) blades. Using logarithmic grid and Q-criterion to learn the vortex dynamics around the blades at low rotational speed. The computational fluid dynamics (CFD) simulation uses Q-criterion to probe vortices and logarithmic grid to emphasize the micro-gridding effect of the turbulent boundary layer. The visualization & measurement of the simulation results give the coefficient of pressure (Cp). For forward 3-D wind turbine blade, at low rotational speed, the strongly accelerated laminar region surrounds the lower blade, and the decelerated tip blade region coalesce each other give rise to a reverse limiting streamline, eroding the laminar region further until a little is left on the tip of the blade. The "reverse limiting streamline" grows inward radially, the area is narrowing closing to the leading edge of the blade tip. The second side of the rolled-up vortex appears the velocity ratio (Uc/Ulocal) of the second vortices are higher than the main vortex cores. For radius R=1.547 m, U=12 m/s, at 210 RPM, CL and CD values reach a maximum with fully laminar tip conditions. While at 120 RPM, the CL and CD values reach a minimum in the absence of laminar tips. The results show the detailed vortex dynamic pattern surround the blades, give more understanding to design laminar 3-D blade toward a noiseless wind turbine system.
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SHEVKUN, NIKOLAY A. "Heat recovery plant: ways to improve energy efficiency". Agricultural Engineering, n. 6 (2023): 4–9. http://dx.doi.org/10.26897/2687-1149-2023-6-4-9.
Testo completoAbstract (sommario):
One of the ways to reduce the cost of heating production facilities in animal husbandry is the use of regenerative heat recovery plants. However, the existing designs of heat exchangers have a number of design flaws affecting their functionality, in particular, the uneven distribution of the air flow over the surface of a heat exchanger. This, in turn, does not provide for a more complete utilization of exhaust air heat. Using the example of a recuperative heat recovery unit UT‑3000, the authors consider the possibility of retrofitting it with an aerodynamic grid to evenly distribute the exhaust air flow over the heat exchanger surface and reduce energy costs for its operation. To do this, they analyzed the applicability of the aerodynamic grid. The size of a blade chord was taken into account as an optimisation parameter. The pressure losses calculated on the “fan - pallet - heat exchanger” section showed that the use of an aerodynamic grid with a “normal” number of blades would create a minimum airflow pressure loss of 0.73 Pa minimum airflow pressure loss of 0.73 Pa, which is 58% less than in the version without an aerodynamic grid. Further experimental study of the uniform airflow distribution over the heat exchanger surface aimed at improving the energy efficiency of the heat recovery unit requires a new design of a heat exchanger with an aerodynamic grid, taking into account the recommended range of “normal” number of blades from 16 to 21, the blade circumference arc of 95° and the blade pitch angle ranging between 68 and 82°.
17
Roy, Lalit, Kellis Kincaid, Roohany Mahmud e David W. MacPhee. "Double-Multiple Streamtube Analysis of a Flexible Vertical Axis Wind Turbine". Fluids 6, n. 3 (13 marzo 2021): 118. http://dx.doi.org/10.3390/fluids6030118.
Testo completoAbstract (sommario):
Vertical-axis wind turbines (VAWTs) have drawn increased attention for off-grid and off-shore power generation due to inherent advantages over the more popular horizontal-axis wind turbines (HAWTs). Among these advantages are generator locale, omni-directionality and simplistic design. However, one major disadvantage is lower efficiency, which can be alleviated through blade pitching. Since each blade must transit both up- and down-stream each revolution, VAWT blade pitching techniques are not yet commonplace due to increased complexity and cost. Utilizing passively-morphing flexible blades can offer similar results as active pitching, requiring no sensors or actuators, and has shown promise in increasing VAWT performance in select cases. In this study, wind tunnel tests have been conducted with flexible and rigid-bladed NACA 0012 airfoils, in order to provide necessary input data for a Double-Multiple Stream-Tube (DMST) model. The results from this study indicate that a passively-morphing VAWT can achieve a maximum power coefficient (Cp) far exceeding that for a rigid-bladed VAWT CP (18.9% vs. 10%) with reduced normal force fluctuations as much as 6.9%. Operational range of tip-speed ratio also is observed to increase by a maximum of 40.3%.
18
Sun, Da-Gang, Jin-Jun Guo, Yong Song, Bi-juan Yan, Zhan-Long Li e Hong-Ning Zhang. "Flutter stability analysis of a perforated damping blade for large wind turbines". Journal of Sandwich Structures & Materials 21, n. 3 (28 aprile 2017): 973–89. http://dx.doi.org/10.1177/1099636217705290.
Testo completoAbstract (sommario):
The flutter stability of wind turbine blades is one of the important contents in the research of wind turbines. The bending stiffness of blades has decreased with the development of large-sized wind turbines. To achieve damping flutter-suppressing on the long spanwise blades, perforated damping blade was proposed under the consideration of the structural damping factor and the structural stiffness in this paper. Through the study of the unit cell, the deformation model was established and the structural loss factor of the perforated damping blade was derived. The undamped blade and the perforated damping blade, combined with the relevant parameters of a 1500 kW wind turbine blade, were established to simulate the flutter-suppressing abilities and the structural stability. The dynamic response analysis was accomplished with the large deformation theory, and the MPC algorithm was used to realize grid mobile and data delivery, according to the Newmark time integration method. The comparison results show that the perforated damping blade has both a higher structural damping factor and a better structural stiffness.
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Reese, Hauke, Chisachi Kato e Thomas H. Carolus. "Large Eddy Simulation of Acoustical Sources in a Low Pressure Axial-Flow Fan Encountering Highly Turbulent Inflow". Journal of Fluids Engineering 129, n. 3 (5 ottobre 2006): 263–72. http://dx.doi.org/10.1115/1.2427077.
Testo completoAbstract (sommario):
A large eddy simulation (LES) was applied to predict the unsteady flow in a low-speed axial-flow fan assembly subjected to a highly “turbulent” inflow that is generated by a turbulence grid placed upstream of the impeller. The dynamic Smagorinsky model (DSM) was used as the subgrid scale (SGS) model. A streamwise-upwind finite element method (FEM) with second-order accuracy in both time and space was applied as the discretization method together with a multi-frame of reference dynamic overset grid in order to take into account the effects of the blade-wake interactions. Based on a simple algebraic acoustical model for axial flow fans, the radiated sound power was also predicted by using the computed fluctuations in the blade force. The predicted turbulence intensity and its length scale downstream of the turbulence grid quantitatively agree with the experimental data measured by a hot-wire anemometry. The response of the blade to the inflow turbulence is also well predicted by the present LES in terms of the surface pressure fluctuations near the leading edge of the blade and the resulting sound power level. However, as soon as the effects of the turbulent boundary layer on the blades become important, the prediction tends to become inaccurate.
20
Chen, S. H., A. H. Eastland e E. D. Jackson. "Unsteady Aerodynamic Analysis of Subsonic Oscillating Cascade". Journal of Turbomachinery 116, n. 3 (1 luglio 1994): 501–12. http://dx.doi.org/10.1115/1.2929439.
Testo completoAbstract (sommario):
This paper describes the development of the source-doublet-based potential paneling method for oscillating cascade unsteady aerodynamic load predictions. By using the integral influence coefficient method and by using the interblade phase angles, the unsteady loads on an oscillating cascade can be accurately predicted at a minimum cost. As the grids are placed only on the blade surfaces, the blades are allowed to vibrate without grid deformation problems. Four notable subsonic oscillating cascade test cases that cover most important parameters, e.g., blade geometry, interblade phase angle, flow coefficient, flow speed, frequency, etc., are studied in this paper. The agreement between the present solutions and other numerical/experimental results demonstrates the robustness of the present model. Applicability of the method for realistic compressible flow cascades is also discussed.
21
Abras, Jennifer N., C. Eric Lynch e Marilyn J. Smith. "Computational Fluid Dynamics–Computational Structural Dynamics Rotor Coupling Using an Unstructured Reynolds-Averaged Navier–Stokes Methodology". Journal of the American Helicopter Society 57, n. 1 (1 gennaio 2012): 1–14. http://dx.doi.org/10.4050/jahs.57.012001.
Testo completoAbstract (sommario):
The focus of this paper is to discuss the unique challenges introduced through the use of unstructured grids in rotorcraft computational fluid dynamics (CFD)–computational structural dynamics (CSD) coupling. The use of unstructured grid methodology in CFD has been expanding because of the advantages in grid generation and modeling of complex configurations. However, the resulting amorphous distribution of the grid points on the rotor blade surface provides no information with regard to the orientation of the blade, in direct contrast to structured grid methodology that can take advantage of the ordered mapping of points to identify the orientation as well as simplifying airloads integration. A methodology has been developed and is described here, which now permits unstructured methods to be utilized for elastic rotary-wing simulations. This methodology is evaluated through comparison of the UH60A rotor with available flight test data for forward flight.
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Zhong, B., e N. Qin. "Non-inertial multiblock Navier-Stokes calculation for hovering rotor flowfields using relative velocity approach". Aeronautical Journal 105, n. 1049 (luglio 2001): 379–89. http://dx.doi.org/10.1017/s000192400001229x.
Testo completoAbstract (sommario):
AbstractA three dimensional Navier-Stokes solver is presented for calculating the hovering rotor flowfield using Osher's approximate Riemann solver. The Navier-Stokes equations are recast in the attached blade relative system using relative flow velocities as variables. Multiblock techniques are used to obtain a structured grid around the blade. A modified MUSCL scheme is proposed to alleviate the inaccuracy in the discretisation of the relative variable formulation. The calculations are performed for a two-bladed model rotor on C-H, O-O and C-H cylindrical grid topologies respectively. Computational solutions show reasonably good agreement with the experimental data for different lifting cases. The difficulty and suitability of different grid topologies for capturing the tip vortex is illustrated. The differences between Euler and Navier-Stokes solutions and between wake modelling and wake capturing approaches are also revealed. The results indicate that the relative velocity approach can give reasonable results for hovering rotor flowfields if due care is taken in minimising possible numerical errors.
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BALIKOĞLU, Fatih, Tayfur Kerem Demircioğlu e Ali IŞIKTAŞ. "Mechanical Properties Of Sandwich Composites Used For Aerofoil Shell Structures Of Wind Turbine Blade". ICONTECH INTERNATIONAL JOURNAL 5, n. 1 (28 marzo 2021): 26–37. http://dx.doi.org/10.46291/icontechvol5iss1pp26-37.
Testo completoAbstract (sommario):
The grid-scored foams contribute significantly to the overall mechanical properties of the sandwich structures, such as aerofoil shell structure of wind turbine blades which are subjected to different loads under operating conditions. The goal of the present paper is to examine the four-point bending, flatwise and edgewise compression and in-plane shear behaviour of sandwich panels composed of composite face sheets of E-glass/ bisphenol-A epoxy resin and plain and grid-scored PVC foams. The four-point bending failure load of the grid-scored foamed sandwich beams increased by 28.1% compared to the plain foamed ones. The flatwise compression strength of samples with grid-scored foam increased by 546% compared to plain foamed samples. The resin grids contributed to an increase in the flat-wise compression stress inducing the core crushing. Under the edgewise compression load, using the grid-scored foam increased the maximum load values by only about 2.9% relative to the plain foam. The reason for this small difference can be addressed as the facings are more effective in carrying the edgewise loadings. With the use of the grid-scored foam, an increase of 38.2% was obtained in-plane shear strength compared to plain foamed sandwich beams. The resin grids improved bonding between the facings and PVC foam.
24
Zhou, Weidong, Zhimei Zhao, T. S. Lee e S. H. Winoto. "Investigation of Flow Through Centrifugal Pump Impellers Using Computational Fluid Dynamics". International Journal of Rotating Machinery 9, n. 1 (2003): 49–61. http://dx.doi.org/10.1155/s1023621x0300006x.
Testo completoAbstract (sommario):
With the aid of computational fluid dynamics, the complex internal flows in water pump impellers can be well predicted, thus facilitating the design of pumps. This article describes the three-dimensional simulation of internal flow in three different types of centrifugal pumps (one pump has four straight blades and the other two have six twisted blades). A commercial three-dimensional Navier-Stokes code called CFX, with a standardk–εtwo-equation turbulence model was used to simulate the problem under examination. In the calculation, the finite-volume method and an unstructured grid system were used for the solution procedure of the discretized governing equations for this problem.Comparison of computational results for various types of pumps showed good agreement for the twisted-blade pumps. However, for the straight-blade pump, the computational results were somewhat different from widely published experimental results. It was found that the predicted results relating to twisted-blade pumps were better than those relating to the straight-blade pump, which suggests that the efficiency of a twisted-blade pump will be greater than that of a straight-blade pump. The calculation also predicts reasonable results in both the flow pattern and the pressure distribution.
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Basson, A., e B. Lakshminarayana. "Numerical Simulation of Tip Clearance Effects in Turbomachinery". Journal of Turbomachinery 117, n. 3 (1 luglio 1995): 348–59. http://dx.doi.org/10.1115/1.2835668.
Testo completoAbstract (sommario):
The numerical formulation developed here includes an efficient grid generation scheme, particularly suited to computational grids for the analysis of turbulent turbo-machinery flows and tip clearance flows, and a semi-implicit, pressure-based computational fluid dynamics scheme that directly includes artificial dissipation, and is applicable to both viscous and inviscid flows. The value of this artificial dissipation is optimized to achieve accuracy and convergency in the solution. The numerical model is used to investigate the structure of tip clearance flows in a turbine nozzle. The structure of leakage flow is captured accurately, including blade-to-blade variation of all three velocity components, pitch and yaw angles, losses and blade static pressures in the tip clearance region. The simulation also includes evaluation of such quantities as leakage mass flow, vortex strength, losses, dominant leakage flow regions, and the spanwise extent affected by the leakage flow. It is demonstrated, through optimization of grid size and artificial dissipation, that the tip clearance flow field can be captured accurately.
26
Alhrshy, L., e C. Jauch. "A Resource-Efficient Design for a Flexible Hydraulic-Pneumatic Flywheel in Wind Turbine Blades". Journal of Physics: Conference Series 2265, n. 3 (1 maggio 2022): 032018. http://dx.doi.org/10.1088/1742-6596/2265/3/032018.
Testo completoAbstract (sommario):
Abstract The utilization of renewable energy resources significantly increases in order to reduce the impact of climate change. Wind turbines are one of the most important renewable energy sources and have an important role to play in power generation. They do, however, have to serve the increasingly variable demands of the grid. Some of these demands cannot be satisfied with the standard control mechanisms of state-of-the-art wind turbines. A hydraulic-pneumatic flywheel in a wind turbine rotor is one mechanism which, in addition to its various grid services, can also reduce the mechanical loads on the structure of a wind turbine. However, the installation of such a flywheel into rotor blades increases the weight of the blades. This paper focusses on the development of a design method for reducing the additional mass of the flywheel. This method incorporates the piston accumulators of the flywheel in the blade support structure, which allows for the replacement of parts of the blade spar caps with composite material from the piston accumulators. This enables the flywheel to be installed into the rotor blades without making the wind turbine significantly heavier.
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Jamaluddin, Nur Syafiqah, Alper Celik, Kabilan Baskaran, Djamel Rezgui e Mahdi Azarpeyvand. "Experimental Analysis of Rotor Blade Noise in Edgewise Turbulence". Aerospace 10, n. 6 (25 maggio 2023): 502. http://dx.doi.org/10.3390/aerospace10060502.
Testo completoAbstract (sommario):
This paper presents an experimental investigation into the effects of turbulence ingestion on the aerodynamic noise characteristics of rotor blades in edgewise flight. A small-scaled, two-bladed rotor was used in the study. The test utilised two turbulence-generating grids, to generate turbulence inflows with different characteristics, and to compare them to the baseline configuration of the laminar inflow. The experiments were set at forwarding edgewise flight configuration, with freestream inflow velocity ranging from 10 m/s to 22 m/s. Simultaneous measurements of far-field acoustic pressure and load were conducted, along with a separate flow measurement using particle image velocimetry. The acoustic spectra demonstrated a larger contribution to the tonal noise radiation at blade passing frequency, and to the broadband noise radiation at the mid-frequency domain, due to turbulence ingestion. However, the broadband responses in the high-frequency domain were comparable between the tested laminar and turbulence inflow cases, with similar broadband humps featuring in the acoustic spectra. The directivity patterns of the overall sound pressure level showed that the noise radiation was lowest near the plane of rotation, and highest downstream. Turbulence ingestion effects could also be seen in the elevated noise levels throughout the observation positions for the grid inflow cases, particularly at larger advance ratios.
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Clarke, Ryan W., Erik G. Rognerud, Allen Puente-Urbina, David Barnes, Paul Murdy, Michael L. McGraw, Jimmy M. Newkirk et al. "Manufacture and testing of biomass-derivable thermosets for wind blade recycling". Science 385, n. 6711 (23 agosto 2024): 854–60. http://dx.doi.org/10.1126/science.adp5395.
Testo completoAbstract (sommario):
Wind energy is helping to decarbonize the electrical grid, but wind blades are not recyclable, and current end-of-life management strategies are not sustainable. To address the material recyclability challenges in sustainable energy infrastructure, we introduce scalable biomass-derivable polyester covalent adaptable networks and corresponding fiber-reinforced composites for recyclable wind blade fabrication. Through experimental and computational studies, including vacuum-assisted resin-transfer molding of a 9-meter wind blade prototype, we demonstrate drop-in technological readiness of this material with existing manufacture techniques, superior properties relative to incumbent materials, and practical end-of-life chemical recyclability. Most notable is the counterintuitive creep suppression, outperforming industry state-of-the-art thermosets despite the dynamic cross-link topology. Overall, this report details the many facets of wind blade manufacture, encompassing chemistry, engineering, safety, mechanical analyses, weathering, and chemical recyclability, enabling a realistic path toward biomass-derivable, recyclable wind blades.
29
Xu, Lianchen, Xiaohui Jin, Zhen Li, Wanquan Deng, Demin Liu e Xiaobing Liu. "Particle Image Velocimetry Test for the Inter-Blade Vortex in a Francis Turbine". Processes 9, n. 11 (4 novembre 2021): 1968. http://dx.doi.org/10.3390/pr9111968.
Testo completoAbstract (sommario):
Hydropower units are usually operated in non-design conditions because of power grid requirements. In a partial-load condition, an inter-blade vortex phenomenon occurs between the runner blades of a Francis turbine, causing pressure pulsation and unit vibration, which hinder the safe and stable operation of power stations. However, the mechanism through which the inter-blade vortex generation occurs is not entirely clear. In this study, a specific model of the Francis turbine was used to investigate and visually observe the generation of the blade vortex in Francis turbines in both the initial inter-blade and vortex development zones. Particle image velocimetry was used for this purpose. In addition, we determined the variation law of the inter-blade vortex in the Francis turbine. We found that the size and strength of the inter-blade vortex depend on the unit speed of the turbine. The higher the unit speed is, the stronger the inter-blade vortex becomes. We concluded that the inter-blade vortex of such turbines originates from the pressure surface or secondary flow and stall of the blade at the inlet side of the runner at high unit speeds, and also from the backflow zone of the suction surface of the blade at low unit speeds.
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Zheng, M., L. Zhang, H. P. Teng, J. Hu e M. L. Hu. "Power efficiency of multi-blade drag typed VAWT by CFD simulation". International Review of Applied Sciences and Engineering 9, n. 1 (giugno 2018): 25–29. http://dx.doi.org/10.1556/1848.2018.9.1.4.
Testo completoAbstract (sommario):
In the present paper, CFD simulation is used to perform the numerical calculation of behaviours of multi-blade drag typed VAWT. The sliding grid technology, FLUENT software and PISO algorithm are involved. By taking wind power efficiency Cp as the goal function, the optimal situations of multi-blade drag typed VAWT with 4 and 6 blades are conducted by CFD simulation. In this investigation, the variable parameters include the rotation rate of wind-mill ω, the blade installation angle θ and the blade width d. The results show that: the optimal working conditions for the 4-blade wind mill at the inlet wind speed 8 m/s are ω = 18 r/ min, θ = 28°, and d = 0.83 m, which induces an optimal wind power efficiency rate Cp = 27.127%; the optimal working conditions for the 6-blade wind mill at the inlet wind speed 8 m/s are ω = 18 r/min, θ = 27°, and d = 0.67 m, which leads to an optimal wind power efficiency rate Cp = 30.404%.
31
Zhang, L., e J. C. Han. "Combined Effect of Free-Stream Turbulence and Unsteady Wake on Heat Transfer Coefficients From a Gas Turbine Blade". Journal of Heat Transfer 117, n. 2 (1 maggio 1995): 296–302. http://dx.doi.org/10.1115/1.2822520.
Testo completoAbstract (sommario):
The combined effect of free-stream turbulence and unsteady wakes on turbine blade surface heat transfer was studied. The experiments used a five-blade linear cascade in a low-speed wind tunnel facility. A turbulence grid and spoked-wheel type wake generator produced the free-stream turbulence and unsteady wakes. The mainstream Reynolds numbers based on the cascade inlet mean velocity and blade chord length were 100,000, 200,000, and 300,000. Results show that the blade time-averaged heat transfer coefficient depends on the mean turbulence intensity, regardless of whether this mean turbulence intensity is from unsteady wake only, turbulence grid only, or a wake and grid combination. The higher mean turbulence promotes earlier boundary layer transition and causes much higher heat transfer coefficients on the suction surface. It also significantly enhances the heat transfer coefficients on the pressure surface. The unsteady wake greatly affects blade heat transfer for low oncoming free-stream turbulence; however, the wake effect diminishes for high oncoming turbulence. The free-stream turbulence also strongly affects blade heat transfer for a low wake passing frequency, but the oncoming turbulence effect diminishes for a high unsteady wake condition.
32
Allen, C. B. "CHIMERA volume grid generation within the EROS code". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 214, n. 3 (1 marzo 2000): 125–41. http://dx.doi.org/10.1243/0954410001531962.
Testo completoAbstract (sommario):
The EROS (European ROtorcraft Software) project was a three-year, European Commission funded, collaborative project between research institutes, universities and industry, with the goal of producing a practical computational fluid dynamic (CFD)-based design tool for rotor blade design. The overlapping mesh, or CHIMERA, approach was adopted for structured grid generation within the project. The specifics of volume grid generation in GEROS, the EROS grid generator, are presented here. The capabilities and effectiveness of GEROS are demonstrated, and sample grids are shown for fixed-wing hovering rotor and forward-flight rotor cases.
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Arnone, A., e R. C. Swanson. "A Navier–Stokes Solver for Turbomachinery Applications". Journal of Turbomachinery 115, n. 2 (1 aprile 1993): 305–13. http://dx.doi.org/10.1115/1.2929236.
Testo completoAbstract (sommario):
A computer code for solving the Reynolds-averaged full Navier–Stokes equations has been developed and applied using H- and C-type grids. The Baldwin–Lomax eddy-viscosity model is used for turbulence closure. The integration in time is based on an explicit four-stage Runge–Kutta scheme. Local time stepping, variable coefficient implicit residual smoothing, and a full multigrid method have been implemented to accelerate steady-state calculations. A grid independence analysis is presented for a transonic rotor blade. Comparisons with experimental data show that the code is an accurate viscous solver and can give very good blade-to-blade predictions for engineering applications.
34
Li, Zheng, Wenda Zhang, Hao Dong e Yongsheng Tian. "Performance Analysis and Structure Optimization of a Nautilus Isometric Spiral Wind Turbine". Energies 13, n. 1 (25 dicembre 2019): 120. http://dx.doi.org/10.3390/en13010120.
Testo completoAbstract (sommario):
Background: This paper proposes a Nautilus isometric spiral vertical axis wind turbine, which is a new structure, and its aerodynamic performance and power generation performance need to be analyzed. Methods: A 3D model of the wind turbine was built and its aerodynamic performance was analyzed. Then the wind turbine power generation and grid-connected simulation platform was built by MATLAB/SIMULINK, and its power generation performance and subsequent grid connection were studied. Results: The basic parameters of the wind turbine were obtained. In order to improve efficiency, parameters such as pressure, torque, wind energy utilization rate and relative velocity of wind turbines with different blade numbers and different sizes were compared. In addition, by building a simulation platform for the power generation control system, the power generation characteristics and grid connection characteristic curves of the generator were obtained. Conclusions: When the number of blades is three and the ratio between the ellipse major axis and minor axis of the blade inlet is 0.76, the best efficiency of the wind turbine can be obtained. Application of the power generation control system used in this paper can achieve grid-connected operation of this wind turbine. It also confirmed that the Nautilus isometric spiral wind turbine has good performance and is worthy of in-depth research.
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Demeulenaere, A., O. Léonard e R. Van den Braembussche. "A two-dimensional Navier—Stokes inverse solver for compressor and turbine blade design". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 211, n. 4 (1 giugno 1997): 299–307. http://dx.doi.org/10.1243/0957650971537204.
Testo completoAbstract (sommario):
A two-dimensional viscous inverse method for the design of compressor and turbine blades is presented. It iteratively modifies an initial geometry until a prescribed pressure distribution is reached on the blade surface. The method solves the time-dependent Navier—Stokes equations in a numerical domain of which some boundaries (the blade walls) move during the transient part of the computation. The geometry modification algorithm is based on the transpiration principle: a normal velocity distribution is computed from the difference between the actual and prescribed pressure distributions, and is used to modify the blade shape. A time iteration is then performed on this new blade shape, taking into account the grid movement during the time stepping. A two-dimensional upwind finite-volume Navier—Stokes solver has been developed. The multiblock strategy allows for a selective concentration of the discretization points in the zones of higher gradients. Applications to turbine and compressor blade design illustrate the accuracy of the flow computation, the capabilities and efficiency of the inverse method.
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Kulkarni, Siddharth Suhas, Craig Chapman, Hanifa Shah e David John Edwards. "A computational design method for bio-mimicked horizontal axis tidal turbines". International Journal of Building Pathology and Adaptation 36, n. 2 (14 maggio 2018): 188–209. http://dx.doi.org/10.1108/ijbpa-06-2017-0029.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is to conduct a comparative analysis between a straight blade (SB) and a curved caudal-fin tidal turbine blade (CB) and to examine the aspects relating to geometry, turbulence modelling, non-dimensional forces lift and power coefficients. Design/methodology/approach The comparison utilises results obtained from a default horizontal axis tidal turbine with turbine models available from the literature. A computational design method was then developed and implemented for “horizontal axis tidal turbine blade”. Computational fluid dynamics (CFD) results for the blade design are presented in terms of lift coefficient distribution at mid-height blades, power coefficients and blade surface pressure distributions. Moving the CB back towards the SB ensures that the total blade height stays constant for all geometries. A 3D mesh independency study of a “straight blade horizontal axis tidal turbine blade” modelled using CFD was carried out. The grid convergence study was produced by employing two turbulence models, the standard k-ε model and shear stress transport (SST) in ANSYS CFX. Three parameters were investigated: mesh resolution, turbulence model, and power coefficient in the initial CFD, analysis. Findings It was found that the mesh resolution and the turbulence model affect the power coefficient results. The power coefficients obtained from the standard k-ε model are 15 to 20 per cent lower than the accuracy of the SST model. Further analysis was performed on both the designed blades using ANSYS CFX and SST turbulence model. The variation in pressure distributions yields to the varying lift coefficient distribution across blade spans. The lift coefficient reached its peak between 0.75 and 0.8 of the blade span where the total lift accelerates with increasing pressure before drastically dropping down at 0.9 onwards due to the escalating rotational velocity of the blades. Originality/value The work presents a computational design methodological approach that is entirely original. While this numerical method has proven to be accurate and robust for many traditional tidal turbines, it has now been verified further for CB tidal turbines.
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Shahsavari, A., e M. Nili-Ahmadabadi. "Investigation of an innovative non-free vortex aerodynamic procedure to design a single-stage transonic compressor". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, n. 11 (8 giugno 2017): 2132–43. http://dx.doi.org/10.1177/0954410017710272.
Testo completoAbstract (sommario):
This paper presents an innovative design method for a transonic compressor based on the radial equilibrium theory by means of increasing blade loading. Firstly, the rotor blade of a transonic compressor is redesigned based on the constant spanwise de-Haller number and diffusion. The design method leads to an unconventional increased axial velocity distribution in tip section, which originates from non-uniform enthalpy distribution assumption. A code is applied to extract the compressor meridional plane and blade-to-blade geometry containing rotor and stator in order to design the blade three-dimensional view. A structured grid is generated for the numerical domain of fluid. Finer grids are used for the regions near walls to capture the boundary layer effects and behavior. Reynolds-averaged Navier–Stokes equations are solved by finite volume method for rotating zones (rotor) and stationary zones (stator). The experimental data, available for the performance map of NASA Rotor67, is used to validate the results of the current simulations. Then, the capability of the design method is validated by computational fluid dynamics that is capable of predicting the performance map. The numerical results of the new geometry by representing 11% improvement in efficiency and 19% in total pressure ratio verify the new method advantages. The computational fluid dynamics results also show that the newly designed rotor blades due to a higher velocity in the tip section have a special capacity to increase the loading without any separation. The mass flow reduction is observed in the new geometry, which could be easily improved by changing stagger angle.
38
Sun, Yan, Guohua Xu e Yongjie Shi. "Numerical Investigation of an Unsteady Blade Surface Blowing Method to Reduce Rotor Blade-Vortex Interaction Noise". International Journal of Aerospace Engineering 2022 (27 agosto 2022): 1–19. http://dx.doi.org/10.1155/2022/9647206.
Testo completoAbstract (sommario):
This paper presents a numerical investigation of unsteady surface blowing using periodic variations of jet velocity with azimuthal angle to reduce helicopter rotor blade-vortex interaction (BVI) noise. The unsteady blowing is modeled as the mass flow outlet boundary condition of time-varying jet velocity on the blade surface grid using computational fluid dynamics. The same high-resolution overset grid system and flow/noise solver are used to perform a detailed flow field simulation and noise prediction for the nonblowing baseline case and the steady/unsteady blowing cases under the rotor BVI condition, and a grid convergence study for the steady and unsteady blowing cases is carried out. The BVI noise reduction and rotor thrust coefficient results of the unsteady blowing method and the previously published steady blowing with constant jet velocity are then compared. The noise reduction level of unsteady blowing is approximately equivalent to that of steady blowing (noise reduction is more than 3 dB). However, the loss in rotor thrust coefficient caused by unsteady blowing (3.3%) is only half of that by steady blowing (6.3%); the air mass cost by unsteady blowing is only 63.7% of that by steady blowing per rotation revolution. The results show that unsteady blowing can effectively reduce BVI noise with lower cost and less thrust loss.
39
Henderson, Alan D., Gregory J. Walker e Jeremy D. Hughes. "The Influence of Turbulence on Wake Dispersion and Blade Row Interaction in an Axial Compressor". Journal of Turbomachinery 128, n. 1 (1 febbraio 2005): 150–57. http://dx.doi.org/10.1115/1.2098809.
Testo completoAbstract (sommario):
The influence of free-stream turbulence on wake dispersion and boundary layer transition processes has been studied in a 1.5-stage axial compressor. An inlet grid was used to produce turbulence characteristics typical of an embedded stage in a multistage machine. The grid turbulence strongly enhanced the dispersion of inlet guide vane (IGV) wakes. This modified the interaction of IGV and rotor wakes, leading to a significant decrease in periodic unsteadiness experienced by the downstream stator. These observations have important implications for the prediction of clocking effects in multistage machines. Boundary layer transition characteristics on the outlet stator were studied with a surface hot-film array. Observations with grid turbulence were compared with those for the natural low turbulence inflow to the machine. The transition behavior under low turbulence inflow conditions with the stator blade element immersed in the dispersed IGV wakes closely resembled the behavior with elevated grid turbulence. It is concluded that with appropriate alignment, the blade element behavior in a 1.5-stage axial machine can reliably indicate the blade element behavior of an embedded row in a multistage machine.
40
Cong, Cong. "Decentralized control of vibrations in wind turbines using multiple active tuned mass dampers with stroke constraint". Advances in Mechanical Engineering 10, n. 12 (dicembre 2018): 168781401881675. http://dx.doi.org/10.1177/1687814018816756.
Testo completoAbstract (sommario):
This article is devoted to the study of the vibration control for blades and tower in a wind turbine. Based on the Euler–Lagrangian method, a multi-body dynamic model including three blades with distributed parameter, tower, and their coupling is obtained. Multi active tuned mass dampers have been utilizing as damping devices. Therefore, the dynamics of the tuned mass dampers are also considered in modeling. The influence of extreme wind, and grid dynamics on the vibration of the blade was analyzed. Moreover, the nonlinearity induced by space constraints, which impact on vibration control, is introduced. For active control, the constrained decentralized control strategy is designed via linear matrix inequality which tuned mass dampers stroke constraints are modeled as hard constraints. A doubly fed induction generator connected to an infinite bus including the detailed electrical and structural model was performed on MATLAB/Simulink. Simulation results show that the control strategy can effectively reduce the vibration of the blade while the damper stroke satisfies the working space permitted by the blade. Investigations demonstrate promising results for decentralized constrained control in simultaneous control blade vibrations and tower vibrations. Each actuator is driven separately from the output of the corresponding sensor so that only local feedback control is achieved; this improves the system reliability.
41
Hall, K. C., e C. B. Lorence. "Calculation of Three-Dimensional Unsteady Flows in Turbomachinery Using the Linearized Harmonic Euler Equations". Journal of Turbomachinery 115, n. 4 (1 ottobre 1993): 800–809. http://dx.doi.org/10.1115/1.2929318.
Testo completoAbstract (sommario):
An efficient three-dimensional Euler analysis of unsteady flows in turbomachinery is presented. The unsteady flow is modeled as the sum of a steady or mean flow field plus a harmonically varying small perturbation flow. The linearized Euler equations, which describe the small perturbation unsteady flow, are found to be linear, variable coefficient differential equations whose coefficients depend on the mean flow. A pseudo-time time-marching finite-volume Lax-Wendroff scheme is used to discretize and solve the linearized equations for the unknown perturbation flow quantities. Local time stepping and multiple-grid acceleration techniques are used to speed convergence. For unsteady flow problems involving blade motion, a harmonically deforming computational grid, which conforms to the motion of the vibrating blades, is used to eliminate large error-producing extrapolation terms that would otherwise appear in the airfoil surface boundary conditions and in the evaluation of the unsteady surface pressure. Results are presented for both linear and annular cascade geometries, and for the latter, both rotating and nonrotating blade rows.
42
Yershov, Serhii V., e Viktor A. Yakovlev. "The Influence of Mesh Resolution on 3D RANS Flow Simulations in Turbomachinery Flow Parts". Journal of Mechanical Engineering 24, n. 1 (30 marzo 2021): 13–27. http://dx.doi.org/10.15407/pmach2021.01.013.
Testo completoAbstract (sommario):
The question of the difference mesh refinement degree influence on the results of calculation of the three-dimensional viscous gas flows in the flow parts of turbomachines using the RANS flow models and second order numerical methods is considered. Calculations of flows for a number of turbine and compressor grids on successively refining grids have been performed. We used H-type grids with approximate orthogonalization of cells in the boundary layer. The calculations were carried out using a CFD solver F with the use of an implicit ENO scheme of the second order, a local time step, and a simplified multigrid algorithm. When calculating the flow on fine grids, the following were used: convergence acceleration tools implemented in the solver; truncation of the computational domain with subsequent distribution of the results based on the symmetry property; the computational domain splitting into parts and computations parallelizing. Comparison of the obtained results is carried out, both in terms of qualitative resolution of the complex structure of three-dimensional flows, and in terms of quantitative assessment of losses. Grid convergence was estimated in two ways. In the first, the characteristic two-dimensional distributions of parameters obtained on different grids were visually compared. The purpose of such comparisons was to evaluate the sufficient degree of solution of both the general structure of the flow in grids and its features, namely, shock waves, contact discontinuities, separation zones, wakes, etc. The second estimation method is based on the grid convergence index (GCI). The GCI calculated from the three-dimensional density field was considered in this paper. It is concluded that for scientific research requiring high accuracy of calculations and detailing of the structure of a three-dimensional flow, very fine difference meshes with the number of cells from 106 to 108 in one blade-to-blade channel are needed, while for engineering calculations, under certain conditions, it is sufficient to use meshes with the number of cells less than 1 million in one blade-to-blade channel.
43
Xiao, Zhongyun, Bin Mou, Xiong Jiang e Wei Han. "Computational Aeroelastic method for rotor based on MBDYN". International Journal of Modern Physics B 34, n. 14n16 (1 giugno 2020): 2040077. http://dx.doi.org/10.1142/s0217979220400779.
Testo completoAbstract (sommario):
A framework of numerical formulations for the aeroelastic analysis of helicopter rotor is presented in this paper. The blade structural dynamics are modeled by an open source multibody dynamic software MBDYN, which solves finite element equation of elastic bodies in general motions. Then the structural deformation is transformed to blade surface grid by radial base function (RBF) interpolation, and volume grids are regenerated by RBF and TFI methods. Lastly, the fluid governing equations are solved. By integrating the above methods, S76 hovering rotors are simulated and compared to the test data. Results show that elastic torsion decreases local angle of attack. For status at [Formula: see text] and [Formula: see text], the shock and shock-induced separation are reduced on the outboard blade, which has remarkable effects on the prediction of rotor hovering performance.
44
Ekkad, S. V., A. B. Mehendale, J. C. Han e C. P. Lee. "Combined Effect of Grid Turbulence and Unsteady Wake on Film Effectiveness and Heat Transfer Coefficient of a Gas Turbine Blade With Air and CO2 Film Injection". Journal of Turbomachinery 119, n. 3 (1 luglio 1997): 594–600. http://dx.doi.org/10.1115/1.2841163.
Testo completoAbstract (sommario):
Experiments were performed to study the combined effect of grid turbulence and unsteady wake on film effectiveness and heat transfer coefficient of a turbine blade model. Tests were done on a five-blade linear cascade at the chord Reynolds number of 3.0 × 105 at cascade inlet. Several combinations of turbulence grids, their locations, and unsteady wake strengths were used to generate various upstream turbulence conditions. The test blade had three rows of film holes in the leading edge region and two rows each on the pressure and suction surfaces. Air and CO2 were used as injectants. Results show that Nusselt numbers for a blade with film injection are much higher than that without film holes. An increase in mainstream turbulence level causes an increase in Nusselt numbers and a decrease in film effectiveness over most of the blade surface, for both density injectants, and at all blowing ratios. A free-stream turbulence superimposed on an unsteady wake significantly affects Nusselt numbers and film effectiveness compared with only an unsteady wake condition.
45
Asim, Muhammad, Shoaib Muhammad, Muhammad Amjad, Muhammad Abdullah, M. A. Mujtaba, M. A. Kalam, Mohamed Mousa e Manzoore Elahi M. Soudagar. "Design and Parametric Optimization of the High-Speed Pico Waterwheel for Rural Electrification of Pakistan". Sustainability 14, n. 11 (6 giugno 2022): 6930. http://dx.doi.org/10.3390/su14116930.
Testo completoAbstract (sommario):
This research study presents an approach for analysis of pico hydro waterwheels by both experimental and numerical methods. The purpose of this research is to harness the energy efficiently from flowing water of irrigation channels and other shallow water sources in rural areas because the electrification of rural areas through connection to grid electricity is very costly. The novelty of this research work lies in testing of the waterwheel as a high-speed device, which is not usually explored. The review of existing literature reveals that pico waterwheels have been extensively studied but without changing the blade profile immersed in the water stream ot the inclination angle of the water stream. In this study, a pico scale waterwheel was tested with three different types of blade profiles, namely a C-shape blade, V-shape blade and straight blade, through computational fluid dynamics (CFD) simulations for different tip speed ratios (TSR), varying the immersed depth of the blade in the stream and changing the angle of the water conduit while keeping the number of blades and the diameter of the wheel constant. The numerical and experimental results were validated for the C-shape blade profile. A substantial improvement in performance is observed with a C-shape blade profile at a TSR of 0.88. The results show that by varying the angle of the water conduit, the maximum performance is achieved at inclination φ = 45°, with an overall improvement of 4.87% in the efficiency.
46
Verma, Shalini, Akshoy Ranjan Paul, Anuj Jain e Firoz Alam. "Numerical investigation of stall characteristics for winglet blade of a horizontal axis wind turbine". E3S Web of Conferences 321 (2021): 03004. http://dx.doi.org/10.1051/e3sconf/202132103004.
Testo completoAbstract (sommario):
Wind energy is one of the renewable energy resources which is clean and sustainable energy and the wind turbine is used for harnessing energy from the wind. The blades are the key components of a wind turbine to convert wind energy into rotational energy. Recently, wingtip devices are used in the blades of horizontal axis wind turbine (HAWT), which decreases the vortex and drag, while increases the lift and thereby improve the performance of the turbine. In the present study, a winglet is used at the tip of an NREL phase VI wind turbine blade. Solidworks, Pointwise, and Ansys-Fluent are used for geometric modeling, computational grid generation, and CFD simulation, respectively. The computational result obtained using SST k-ω turbulence modeling is well validated with the experimental data of NREL at 5 and 7 m/s of wind speeds. Numerical investigation of stall characteristics is carried out for wingleted blade at higher turbulence intensity (21% and 25%) and angle of attack (00 to 300 at 50 intervals) at 7 m/s wind speed. The result found that wingletd blade delay stall to 150 for both the cases of turbulence intensity. Increasing the turbulence intensity increases the lift coefficient at stall angle but drag coefficient also increases and thus a lower aerodynamic performance (CL/CD ratio = 13) is obtained. Wingleted blade improves the performance as the intensity of vortices is smaller compared to baseline blade
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Jauch, Clemens. "Grid Services and Stress Reduction with a Flywheel in the Rotor of a Wind Turbine". Energies 14, n. 9 (29 aprile 2021): 2556. http://dx.doi.org/10.3390/en14092556.
Testo completoAbstract (sommario):
Wind power penetration increases in most grids and the sizes of wind turbines increase. This leads to increasingly tough requirements, which are imposed on wind turbines, both from the grid as well as from economics. Some of these partially contradictory requirements can only be satisfied with additional control mechanisms in the wind turbines. In this paper, such a mechanism, i.e., a hydraulic–pneumatic flywheel system in the rotor of a wind turbine, is discussed. This flywheel system supports a wind turbine in providing grid services such as steadying the power infeed, fast frequency response, continuous inertia provision, power system stabilization, and low voltage ride-through. In addition, it can help mitigate the stress on the mechanical structure of a wind turbine, which results from varying operating points, imbalances in the rotor, gravitation that acts on the blades, in-plane vibrations, and emergency braking. The study presented in this paper is based on simulations of a publicly available reference wind turbine. Both the rotor blade design as well as the design of the flywheel system are as previously published. It is discussed how the aforementioned grid services and the stress reduction mechanisms can be combined. Finally, it is concluded that such a flywheel system broadens the range of control mechanisms of a wind turbine substantially, which is beneficial for the grid as well as for the wind turbine itself.
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Vahdati, M., e M. Imregun. "A Non-Linear Aeroelasticity Analysis of a Fan Blade Using Unstructured Dynamic Meshes". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 210, n. 6 (novembre 1996): 549–64. http://dx.doi.org/10.1243/pime_proc_1996_210_230_02.
Testo completoAbstract (sommario):
The main objective of this paper is to present a methodology for the three-dimensional aeroelasticity analysis of turbomachinery blades using an unstructured compressible Navier-Stokes solver for the fluid and a modal model for the structure. The basic fluid solver is constructed in the form of a central difference scheme with explicitly added artificial dissipation which is based upon the fourth- and second-order differences of the solution. The temporal discretization uses an implicit time integration scheme based on a Jacobi relaxation procedure. The structural modes of vibration are determined via a finite element model and the mode shapes are interpolated on to the fluid mesh in a manner that is consistent with general unstructured tetrahedral grids. A spring analogy algorithm that can move the mesh according to the instantaneous shape of a deforming blade has been developed for the accurate tracking of the solid boundaries without creating excessive grid distortions. The performance of the resulting system was examined by considering the aeroelastic behaviour of NASA Rotor 67 fan blade and predictions were compared to experimental results wherever possible. Using a three-dimensional cyclic symmetry model, the tip leading edge time histories were predicted under peak-efficiency and near-stall conditions, and the corresponding aeroelastic natural frequencies and aerodynamic damping values were determined. The blade was found to be stable in all cases considered.
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Madsen, Helge Aagaard, Torben Juul Larsen, Georg Raimund Pirrung, Ang Li e Frederik Zahle. "Implementation of the blade element momentum model on a polar grid and its aeroelastic load impact". Wind Energy Science 5, n. 1 (2 gennaio 2020): 1–27. http://dx.doi.org/10.5194/wes-5-1-2020.
Testo completoAbstract (sommario):
Abstract. We show that the upscaling of wind turbines from rotor diameters of 15–20 m to presently large rotors of 150–200 m has changed the requirements for the aerodynamic blade element momentum (BEM) models in the aeroelastic codes. This is because the typical scales in the inflow turbulence are now comparable with the rotor diameter of the large turbines. Therefore, the spectrum of the incoming turbulence relative to the rotating blade has increased energy content on 1P, 2P, …, nP, and the annular mean induction approach in a classical BEM implementation might no longer be a good approximation for large rotors. We present a complete BEM implementation on a polar grid that models the induction response to the considerable 1P, 2P, …, nP inflow variations, including models for yawed inflow, dynamic inflow and radial induction. At each time step, in an aeroelastic simulation, the induction derived from a local BEM approach is updated at all the stationary grid points covering the swept area so the model can be characterized as an engineering actuator disk (AD) solution. The induction at each grid point varies slowly in time due to the dynamic inflow filter but the rotating blade now samples the induction field; as a result, the induction seen from the blade is highly unsteady and has a spectrum with distinct 1P, 2P, …, nP peaks. The load impact mechanism from this unsteady induction is analyzed and it is found that the load impact strongly depends on the turbine design and operating conditions. For operation at low to medium thrust coefficients (conventional turbines at above rated wind speed or low induction turbines in the whole operating range), it is found that the grid BEM gives typically 8 %–10 % lower 1 Hz blade root flapwise fatigue loads than the classical annular mean BEM approach. At high thrust coefficients that can occur at low wind speeds, the grid BEM can give slightly increased fatigue loads. In the paper, the implementation of the grid-based BEM is described in detail, and finally several validation cases are presented. Comparisons with blade loads from full rotor CFD, wind tunnel experiments and a field experiment show that the model can predict the aerodynamic forces in half-wake, yawed flow, dynamic inflow and turbulent inflow conditions.
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Cinnella, P., P. De Palma, G. Pascazio e M. Napolitano. "A Numerical Method for Turbomachinery Aeroelasticity". Journal of Turbomachinery 126, n. 2 (1 aprile 2004): 310–16. http://dx.doi.org/10.1115/1.1738122.
Testo completoAbstract (sommario):
This work provides an accurate and efficient numerical method for turbomachinery flutter. The unsteady Euler or Reynolds-averaged Navier-Stokes equations are solved in integral form, the blade passages being discretised using a background fixed C-grid and a body-fitted C-grid moving with the blade. In the overlapping region data are exchanged between the two grids at every time step, using bilinear interpolation. The method employs Roe’s second-order-accurate flux difference splitting scheme for the inviscid fluxes, a standard second-order discretisation of the viscous terms, and a three-level backward difference formula for the time derivatives. The dual-time-stepping technique is used to evaluate the nonlinear residual at each time step. The state-of-the-art second-order accuracy of unsteady transonic flow solvers is thus carried over to flutter computations. The code is proven to be accurate and efficient by computing the 4th Aeroelastic Standard Configuration, namely, the subsonic flow through a turbine cascade with flutter instability in the first bending mode, where viscous effect are found practically negligible. Then, for the very severe 11th Aeroelastic Standard Configuration, namely, transonic flow through a turbine cascade at off-design conditions, benchmark solutions are provided for various values of the inter-blade phase angle.