Letteratura scientifica selezionata sul tema "Blade grid"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "Blade grid".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Articoli di riviste sul tema "Blade grid"
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.
9
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.
Tesi sul tema "Blade grid"
1
Mish, Patrick F. "Mean Loading and Turbulence Scale Effects on the Surface Pressure Fluctuations Occurring on a NACA 0015 Airfoil Immersed in Grid Generated Turbulence". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33751.
Testo completoAbstract (sommario):
Detailed surface pressure measurements have been made on a NACA 0015 immersed in two grid generated homogenous flows at Re = 1.17 x 10^6 for a = 0°, 4°, 8°, 12°, 16°, and 20°. The goal of this measurement was to reveal and highlight mean loading and turbulence scale effects on surface pressure fluctuations resulting from turbulence/airfoil interaction. Also, measurements are compared with the theory of Amiet (1976a,b). The surface pressure response shows a dependance on angle of attack, the nature of which is related to the relative chord/turbulence scale. The dependance on turbulence scale appears to be non-monotonic at low reduced frequencies, wr = Pi*f*c/U with both an increase and decrease in unsteady pressure magnitude occuring with increasing mean load. A reduced frequency overlap region exists at wr > 10 where the two different scale flows begin to produce similar effects on the surface pressure with increasing angle of attack manifesting as a rise in unsteady surface pressure magnitude. Also, the interaction of the full 3-dimensional wavenumber spectrum affects the distance over which pressure fluctuations correlate and the extent of correlation is affected by angle of attack as demonstrated in the chordwise and spanwise pressure correlation. Amietâ s theory is shown to agree favorably with measurements in the leading edge region although demonstrates insufficiencies in predicting unsteady pressure phasing.Master of Science
2
Larssen, Jon Vegard. "Large Scale Homogeneous Turbulence and Interactions with a Flat-Plate Cascade". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/26540.
Testo completoAbstract (sommario):
The turbulent flow through a marine propulsor was experimentally modeled using a large cascade configuration with six 33 cm chord flat plates spanning the entire height of the test section in the Virginia Tech Stability Wind Tunnel. Three-component hot-wire velocity measurements were obtained ahead, throughout and behind both an unstaggered and a 35º staggered cascade configuration with blade spacing and onset turbulence integral scales on the order of the chord. This provided a much needed data-set of much larger Taylor Reynolds number than previous related studies and allowed a thorough investigation of the blade-blocking effects of the cascade on the incident turbulent field.
In order to generate the large scale turbulence needed for this study, a mechanically rotating â activeâ grid design was adopted and placed in the contraction of the wind tunnel at a streamwise location sufficient to cancel out the relatively large inherent low frequency anisotropy associated with this type of grid. The resulting turbulent flow is one of the largest Reynolds number (Reλ 1000) homogeneous near-isotropic turbulent flows ever created in a wind tunnel, and provided the opportunity to investigate Reynolds number effects on turbulence parameters, especially relating to inertial range dynamics. Key findings include 1) that the extent of local isotropy is solely determined by the turbulence generator and the size of the wind-tunnel that houses it; and 2) that the turbulence generator operating conditions affect the shape of the equilibrium range at fixed Taylor Reynolds number. The latter finding suggests that grid turbulence is not necessarily self-similar at a given Reynolds number independent of how it was generated.
The experimental blade-blocking data was compared to linear cascade theory and showed good qualitative agreement, especially for wavenumbers above the region of influence of the wind tunnel and turbulence generator effects. As predicted, the turbulence is permanently modified by the presence of the cascade after which it remains invariant for a significant downstream distance outside the thin viscous regions. The obtained results support the claim that Rapid Distortion Theory (RDT) is capable of providing reasonable estimates of the flow behind the cascade even though the experimental conditions lie far outside the predicted region of validity.Ph. D.
3
Taymans, Claire. "Solving Incompressible Navier-Stokes Equations on Octree grids : towards Application to Wind Turbine Blade Modelling". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0157/document.
Testo completoAbstract (sommario):
Le sujet de la thèse est le développement d'un outil numérique qui permet de modéliser l'écoulement autour des pales d'éoliennes. Nous nous sommes intéressés à la résolution des équations de Navier-Stokes en incompressible sur des maillages de type octree où les échelles plus petites en proche parois ont été modélisées par la méthode dite des wall functions. Un procédé d'adaptation automatique du maillage (AMR) a été développé pour affiner le maillage dans les zones où la vorticité est plus importante. Le modèle de structure d'une pale d'éolienne a été également implémenté et couplé avec le modèle fluide car une application de l'outil numérique est l'étude des effets des rafales de vent sur les pales d'éolienne. Un travail expérimental a été mené sur une éolienne avec une mesure de vent en amont. Ces données permettent ainsi de calibrer et valider les modèles numériques développés dans la thèseThe subject of the thesis is the development of a numerical tool that allows to model the flow around wind blades. We are interested in the solving of incompressible Navier-Stokes equations on octree grids, where the smallest scales close to the wall have been modelled by the use of the so-called Wall Functions. An automatic Adaptive Mesh Refinement (AMR) process has been developed in order to refine the mesh in the areas where the vorticity is higher. The structural model of a real wind blade has also been implemented and coupled with the fluid model. Indeed, an application of the numerical tool is the study of the effects of wind gusts on blades. An experimental work has been conducted with an in-service wind turbine with the measurement of wind speed upstream. This data will allow to calibrate and validate the numerical models developed in the thesis
4
Linda, Jakub. "Větrné stroje pro obydlené oblasti". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417801.
Testo completoAbstract (sommario):
The submitted diploma thesis deals with wind machines in densely populated areas. The aim of the work is to design a appropriate wind machine for use on the roofs of buildings, including all the specifics that the air flow in the city may contain. At the beginning, the work focuses on the production of electricity in cities in general, which results in an ideal system of obtaining energy for households. Furthermore, the work deals with the wind in general, where all its specifics are taken over. A very important part of the work is the study of the specifics of air flow in the urban environment together with the numerical simulation of this flow, which results in certain regularities of the location of wind machines on the roofs of buildings. The work then passes to a search of used wind machines, from which the most suitable candidate for use in cities is subsequently selected. The last part of the work is the design of the machine itself for a specific location. In this chapter, the design wind speed is determined from the measured data, which is later followed by the calculation of the geometry of the blades, and finally its benefits and advantages are determined from the properties of the wind machine
5
Ратушний, Олександр Валерійович, Александр Валерьевич Ратушный e Oleksandr Valeriiovych Ratushnyi. "Повышение напорности ступени центробежного насоса путем усовершенствования лопастной решетки рабочего колеса". Thesis, Изд-во СумГУ, 2015. http://essuir.sumdu.edu.ua/handle/123456789/40844.
Testo completoAbstract (sommario):
У дисертаційній роботі подане нове розв’язання наукової задачі, що полягає
у підвищенні енергетичної ефективності ступеня відцентрового насоса. В якості
шляху розв’язання цієї задачі розглядається можливість створення ступенів із
суттєво більшим напором при тих самих геометричних розмірах, величинах
витрати і швидкості обертання. На основі огляду науково-технічної інформаціі
була обгрунтована актуальність теми дослідження, сформульовані його мета і
задачи. Розв’язання наукової задачі полягає у поєднання різних способів впливу
на геометрію лопатевої ґратки робочих коліс: використання двоярусної ґратки
нової геометрії, затиловки вихідних кромок лопаті, лопатей S-подібної форми із
підвищеним кутом виходу.
На адекватних математичних моделях отримано картини течії в робочому
колесі, які дають можливість оцінки розподілів швидкостей та тисків, а також
визначення геометричних параметрів, що найбільш суттєво впливають на його
енергетичні характеристики. Встановлено оптимальні співвідношення основних
геометричних параметрів, що дають можливість збільшити напір колеса на 15-
30% при практично тому ж рівні економічності.
Встановлено вплив окремих геометричних параметрів робочого колеса з
модернізованими лопатевими ґратки на його характеристики, що дало змогу
провести оптимізацію за різними параметрами на основі методики планування
експерименту. Визначено діапазон швидкохідностей ns = 65…95, у якому
сукупність підвищення напору і ККД оптимальні. Виявлена можливість
застосування модернізованих робочих коліс у складі ступеня без заміни
направляючого апарата.В диссертационной работе представленно новое решение научной задачи, заключающейся в повышении энергетической эффективности ступени центробежного насоса. В качестве пути решения этой задачи рассматривается возможность создания ступеней с существенно большим напором при неизменных геометрических размерах, величинах подачи и скорости вращения. На основе обзора научно-технической информации была обоснована актуальность темы исследования, сформулированные его цель и задачи. Решение научной задачи состоит в объединении различных способов влияния на геометрию лопастной решетки рабочих колес: использование двухъярусной решетки новой геометрии, затыловки выходных кромок лопастей, лопастей S- образной формы с увеличенным углом выхода. На адекватных математических моделях получена картины течения в рабочем колесе, которые дают возможность оценки распределения скоростей и давлений, а также определения геометрических параметров, которые наиболее существенно влияют на его энергетические характеристики. Установлены оптимальные соотношения основных геометрических параметров, которые дают возможность увеличить напор колеса на 15-30% при практически том же уровне экономичности. На основе идеи совместного использования способов повышения напорности рабочего колеса были предложены их две конструкции: колесо, в межлопастном канале которого установлено несколько выполненных в два раза тоньше, по сравнению с основной, коротких дополнительных лопастей длиной в 10% от неё с затыловкой выходных кромок лопастей обоих ярусов; колесо, имеющие лопасти S-образной формы с затыловкой выходных кромок и с несколькими короткими дополнительными лопастями в межлопастном канале, выполненными в два раза тоньше по сравнению с основной лопастью и длиной в 1 0% от неё, повторяющими форму основных лопастей. Установлено влияние отдельных геометрических параметров рабочего колеса с модернизованными лопастными решетками на его характеристики, которое дало возможность провести оптимизацию по разным параметрам на основе методики планирования эксперимента. Была решена компромиссная задача нахождения условного экстремума для одной поверхности отклика при ограничениях, налагаемых другой. Для этого использовался метод неопределённых множителей Лагранжа. Определен диапазон быстроходностей ns = 65…95, в котором совокупность повышения напора и ККД оптимальны. Указана возможность применения модернизованных рабочих колес в составе ступени без замены направляющего аппарата.
In the dissertation presented a new solutionof a scientific problem, consisting in increasing the energy efficiency of the centrifugal pump stage. As away of solving this problem is considered the ability of creation of steps with considerably high pressure at constant geometric dimensions, feed amount and rotational speed. Based on a review of scientific and technical information has been proving the actuality the research topics and formulated its purpose and tasks. The solution of this scientific problem, which is to increase the pressure centrifugal pump stage by combining a variety of ways to influence the geometry of the blade grid of impellers: by using the double blade grid, truncated blade shape modification, the S-shaped blades with a larger angle of outlet. At the appropriate mathematical models to get a picture of flowin the impeller, which allow assessment of distribution of velocities and pressures and determining the geometric parameters that most significantly affect its energy characteristics. The optimum ratio of the basic geometrical parameters which allow increasing the pressure ofthe impeller between 15-30 % with almost the same level of efficiency. The influence of individual geometric parameters of impeller with the modernizing blades on its characteristics, which provided an opportunity to optimize for different parameters based on the methodology of experimental design, is stablished. It determined the range of high-speed ns = 65-95, in which the totality of increasing pressure and the efficiency are optimal. Indicated the possibility of using modernized impellers composed stage without replacing the guide vanes.
6
Gecgel, Murat. "Parallel, Navier". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/12604807/index.pdf.
Testo completoAbstract (sommario):
The aim of this study is to extend a parallel Fortran90 code to compute three&ndashdimensional laminar and turbulent flowfields over rotary wing configurations. The code employs finite volume discretization and the compact, four step Runge-Kutta type time integration technique to solve unsteady, thin&ndash
layer Navier&ndash
Stokes equations. Zero&ndash
order Baldwin&ndash
Lomax turbulence model is utilized to model the turbulence for the computation of turbulent flowfields. A fine, viscous, H type structured grid is employed in the computations. To reduce the computational time and memory requirements parallel processing with distributed memory is used. The data communication among the processors is executed by using the MPI ( Message Passing Interface ) communication libraries. Laminar and turbulent solutions around a two bladed UH &ndash
1 helicopter rotor and turbulent solution around a flat plate is obtained. For the rotary wing configurations, nonlifting and lifting rotor cases are handled seperately for subsonic and transonic blade tip speeds. The results are, generally, in good agreement with the experimental data.
7
Duffy, Michael James. "Small wind turbines mounted to existing structures". Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34765.
Testo completoAbstract (sommario):
Small wind turbines, and especially urban-mounted turbines which require no dedicated pole, have garnered great public enthusiasm in recent years. This enthusiasm has fueled widespread growth among energy conservationists, and estimates predict that the power produced nationally by small wind will increase thirty-fold by 2013. Unfortunately, most of the wind resources currently available have been designed for larger, rural-mounted turbines; thus, they are not well suited for this nascent market. A consequence of this is that many potential urban small wind turbine owners over-predict their local wind resource, which is both costly and inefficient. According to a recent study published by Encraft Ltd., small wind turbines mounted to buildings far underperformed their rural pole mounted counterparts.
As a proposed solution to this problem, this project introduces the concept of a Web-based Wind Assessment System (WWAS). This system combines all the necessary resources for potential urban small wind turbine customers into a single web-based tool. The system also presents the concept of a modular wind measurement system, which couples with the WWAS to provide real-time wind data measurements. The benefits of the system include its ease of use, flexibility of installation, data accessibility from any web browser, and expert advice. The WWAS prevents potential clients from investing in a system that may not be viable for their location.
In addition, a small wind turbine is designed in this project, which has a unique modular mounting system, allowing the same baseline wind turbine to attach to various structures using interchangeable mounting hardware. This includes such accessible urban structures as street lights, building corners, flag poles, and building walls, among others.
This design also utilizes concepts that address some of the challenges associated with mounting small wind turbines to existing urban structures. These concepts include: swept tip blades and lower RPM to reduce noise; vibration suppression using rubber shims; a netted duct to protect wildlife; and a direct-drive permanent magnet generator to ensure low starting torque.
Finally, the cost of this system is calculated using off-the-shelf components, which minimize testing and certification expense. This small wind turbine system is designed to be grid-connected, has a 6 foot diameter rotor, and is rated at 1 kW. This design features a unique modular interchangeable mounting system. The cost for this complete system is estimated to be $2,050. If a users' site has an average wind speed of 14 mph (6.5 m/s), this system will generate a return on investment in 8.5 years, leaving over 10 years of profit. The profit for this system, at this sample average wind speed, yields over $4,000 during its 20-year design life, which is a two-fold return on investment.
This project has implications for various stakeholders in the small wind turbine market, including designers, engineers, manufacturers, and potential customers. Equally important is its potential role in guiding our future national--even global--energy agenda.
8
Joulain, Antoine. "Simulation aérodynamique d'extrémités de pales de rotors sustentateurs d'hélicoptère". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4768.
Testo completoAbstract (sommario):
L’aérodynamique de l’hélicoptère est fortement impactée par les tourbillons générés aux extrémités de pales. La complexité des phénomènes en jeux et l’insuffisance de données expérimentales locales font du design d’extrémité un véritable défi. Cette étude propose une nouvelle approche dédiée à l’étude des extrémités en vol stationnaire. Une méthode numérique rapide et précise est mise au point afin d’étudier une extrémité de pale en rotation comme une extrémité d’aile fixe. Chaque étape de la construction de la méthode est validée par des comparaisons détaillées avec des données expérimentales publiées. Le code CFD elsA est dans un premier temps utilisé pour mettre en place une méthode de calcul basée sur la résolution des équations Reynolds-Averaged Navier-Stokes en stationnaire. La convergence de la solution et l’indépendance au maillage et aux paramètres numériques sont étudiées en détail en deux, puis en trois dimensions. La précision importante de la solution numérique permet d’analyser finement la physique de l’enroulement tourbillonnaire en extrémité. Des géométries tronquée et arrondie sont étudiées en détail, et révèlent la présence de systèmes tourbillonnaires complexes. Puis la nouvelle méthode d’adaptation pale en rotation / aile fixe est présentée. Une méthode de calcul hybride est mise au point entre le code de mécanique du vol HOST et le code elsA. En repère fixe, l’aérodynamique globale sur la pale et locale en extrémité est calculée fidèlement pour toutes les configurations étudiées. Comparée aux méthodes d’adaptation précédemment publiées, cette nouvelle stratégie offre une amélioration considérable concernant la simulation de l’aérodynamique de paleHelicopter aerodynamics is strongly influenced by the vortices generated from the rotor-blade tips. The design of efficient tip shapes is a challenging task because of the complexity of the aerodynamic phenomena involved and the lack of local blade-tip flow measurements. This work provides a contribution to the design of helicopter tips in hover. An efficient, relatively simple and quick numerical method is set up to study rotating blade tips in fixed-wing configurations. The accuracy of the method is shown at each step of the construction by comprehensive comparisons with reliable experimental data from the literature. First, an efficient steady Reynolds-Averaged Navier-Stokes method is constructed using ONERA's elsA code. Comprehensive studies of convergence, grid dependence and sensitivity to the numerical method are performed in two and three dimensions. The very good agreement of the solution with measurements and the accuracy of the numerical method allow a physical analysis with unprecedented detail of the vortex generation and roll-up near square and rounded wing tips. The new methodology of framework adaptation is then presented. An uncoupled hybrid strategy is set up using AIRBUS HELICOPTERS' Comprehensive Analysis code HOST and the Computational Fluid Dynamics solver elsA. Global and local performance calculations are validated for all investigated test cases. Comparison with previously published adaptation methods indicates considerable improvement in the prediction of the blade aerodynamics
9
Zhou, Jian Ming. "A multi-grid method for computation of film cooling". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29414.
Testo completoAbstract (sommario):
This thesis presents a multi-grid scheme applied to the solution of transport equations in turbulent flow associated with heat transfer. The multi-grid scheme is then applied to flow which occurs in the film cooling of turbine blades. The governing equations are discretized on a staggered grid with the hybrid differencing scheme. The momentum and continuity equations are solved by a nonlinear full multi-grid scheme with the SIMPLE algorithm as a relaxation smoother. The turbulence k — Є equations and the thermal energy equation are solved on each grid without multi-grid correction.
Observation shows that the multi-grid scheme has a faster convergence rate in solving the Navier-Stokes equations and that the rate is not sensitive to the number of mesh points or the Reynolds number. A significant acceleration of convergence is also produced for the k — Є and the thermal energy equations, even though the multi-grid correction is not applied to these equations. The multi-grid method provides a stable and efficient means for local mesh refinement with only little additional computational and.memory costs.
Driven cavity flows at high Reynolds numbers are computed on a number of fine meshes for both the multi-grid scheme and the local mesh-refinement scheme. Two-dimensional film cooling flow is studied using multi-grid processing and significant improvements
in the results are obtained. The non-uniformity of the flow at the slot exit and its influence on the film cooling are investigated with the fine grid resolution. A near-wall turbulence model is used. Film cooling results are presented for slot injection with different mass flow ratios.Science, Faculty of
Mathematics, Department of
Graduate
10
Banerjee, Mili. "Subordinate Perception of Leadership Style and Power: A Cross-Cultural Investigation". University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1253769052.
Testo completoLibri sul tema "Blade grid"
1
L, Rigby D., e NASA Glenn Research Center, a cura di. A numerical analysis of heat transfer and effectiveness on film cooled turbine blade tip models. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.
Cerca il testo completo
2
L, Hoffman G., e United States. National Aeronautics and Space Administration., a cura di. IGB grid: User's manual (a turbomachinery grid generation code). [Washington, DC]: National Aeronautics and Space Administration, 1992.
Cerca il testo completo
3
Center, Langley Research, a cura di. Full-potential modeling of blade-vortex interactions. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1997.
Cerca il testo completo
4
Center, Langley Research, a cura di. Full-potential modeling of blade-vortex interactions. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1997.
Cerca il testo completo
5
C, Hall Kenneth, e United States. National Aeronautics and Space Administration., a cura di. Sensitivity analysis for aeroacoustic and aeroelastic design of turbomachinery blades: Final technical report. Durham, NC: Dept. of Mechanical Engineering and Materials Science, School of Engineering, Duke University, 1995.
Cerca il testo completo
6
N, Duque Earl P., e United States. National Aeronautics and Space Administration., a cura di. Helicopter rotor blade computation in unsteady flows using moving overset grids. Washington, DC: American Institute of Aeronautics and Astronautics, 1996.
Cerca il testo completo
7
Center, NASA Glenn Research, a cura di. Heat transfer on a film-cooled rotating blade. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.
Cerca il testo completo
8
Boyle, Robert J. Grid orthogonality effects on predicted turbine midspan heat transfer and performance. [Washington, DC]: National Aeronautics and Space Administration, 1995.
Cerca il testo completo
9
A, Garriz Javier, Samareh Jamshid A e United States. National Aeronautics and Space Administration., a cura di. The development of a tool for semi-automated generation of structured and unstructured grids about isolated rotorcraft blades. [Washington, D.C: National Aeronautics and Space Administration, 1997.
Cerca il testo completo
10
S, Clark William. Prediction of unsteady flows in turbomachinery using the linearized Euler equations on deforming grids. [Washington, DC: National Aeronautics and Space Administration, 1991.
Cerca il testo completoCapitoli di libri sul tema "Blade grid"
1
Bartosch, Leonard, Julia Baule, Felipe Castrillón e Dinah Spitzley. "Managerial Grid nach Blake und Mouton". In Ziel- und Leistungsorientierung, 11–12. Wiesbaden: Springer Fachmedien Wiesbaden, 2017. http://dx.doi.org/10.1007/978-3-658-16882-7_4.
Testo completo
2
Opiela, M., M. Meinke e W. Schröder. "Simulation of a Wake-Blade Interaction in Moving Grids". In Computational Fluid Dynamics 2000, 437–42. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-56535-9_65.
Testo completo
3
Im, Dong-Kyun, Seong-Yong Wie, Eugene Kim, Jang-Hyuk Kwon, Duck-Joo Lee, Ki-Hoon Chung e Seung-Bum Kim. "Aerodynamic Analysis of Rotor Blades using Overset Grid with Parallel Computation". In Lecture Notes in Computational Science and Engineering, 101–10. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14438-7_10.
Testo completo
4
Thakre, Utkarsh, e Asim Tewari. "Using Automated Finite Element Framework to Analyze Offshore Grid Turbine Blades Design". In Lecture Notes in Mechanical Engineering, 621–30. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0698-4_68.
Testo completo
5
Fuchs, M., H. Burchhardt, A. Losch e K. M. Stürmer. "Die Versorgung proximaler Oberarmfrakturen im hohen Lebensalter mit der „durchbohrten Winkelplatte 90 Grad“ / Stabilization of Proximal Humeral Fractures with the Cannulated Blade Plate 90° in Elderly Patients". In Deutsche Gesellschaft für Chirurgie, 360. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-56458-1_118.
Testo completo
6
Socrates, S., M. Shanmugapriya, B. Murugeshwari e S. Angalaeswari. "Efficient Design for Implantable Device Constant Current Induction Doubly Fed Generating Incorporating Grid Connectivity". In Advances in Computer and Electrical Engineering, 382–92. IGI Global, 2024. http://dx.doi.org/10.4018/979-8-3693-3735-6.ch019.
Testo completoAbstract (sommario):
This research presents an innovative approach to the efficient design of implantable devices, focusing on the development and modeling of a constant current induction doubly fed generator (DFIG) system that incorporates grid connectivity under both sub and hyper synchronization conditions. The core of this study is to establish a physical equation for a power station and a DFIG using a combination of power management and voltage estimation techniques in the context of circuit power. The induction generator (IG) blade in the system is designed to rotate synchronously with the photovoltaic (PV) system frequency. The DFIG is connected to a distribution substation, with synchronization between the active power filter and the grid depot achieved through the use of dual converters: a machine side converter (MSC) on the grid side and a grid side converter (GSC) on the power system. Within the circuits, two applications are implemented to recover the parameter spectrum, aiming to maximize the thermodynamic efficiency delivered to the DFIG rotor.
7
Brahimi, Tayeb, e Ion Paraschivoiu. "Aerodynamic Analysis and Performance Prediction of VAWT and HAWT Using CARDAAV and Qblade Computer Codes". In Entropy and Exergy in Renewable Energy [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96343.
Testo completoAbstract (sommario):
Wind energy researchers have recently invited the scientific community to tackle three significant wind energy challenges to transform wind power into one of the more substantial, low-cost energy sources. The first challenge is to understand the physics behind wind energy resources better. The second challenge is to study and investigate the aerodynamics, structural, and dynamics of large-scale wind turbine machines. The third challenge is to enhance grid integration, network stability, and optimization. This chapter book attempts to tackle the second challenge by detailing the physics and mathematical modeling of wind turbine aerodynamic loads and the performance of horizontal and vertical axis wind turbines (HAWT & VAWT). This work underlines success in the development of the aerodynamic codes CARDAAV and Qbalde, with a focus on Blade Element Method (BEM) for studying the aerodynamic of wind turbines rotor blades, calculating the induced velocity fields, the aerodynamic normal and tangential forces, and the generated power as a function of a tip speed ration including dynamic stall and atmospheric turbulence. The codes have been successfully applied in HAWT and VAWT machines, and results show good agreement compared to experimental data. The strength of the BEM modeling lies in its simplicity and ability to include secondary effects and dynamic stall phenomena and require less computer time than vortex or CFD models. More work is now needed for the simulation of wind farms, the influence of the wake, the atmospheric wind flow, the structure and dynamics of large-scale machines, and the enhancement of energy capture, control, stability, optimization, and reliability.
8
Valentine, Scott. "Understanding Wind Power Systems". In Wind Power Politics and Policy. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780199862726.003.0004.
Testo completoAbstract (sommario):
All of the above statements represent prominent objections to wind power development. For the most part, these statements are premised upon small truths that have been exaggerated by wind power opponents in order to generate public opposition. The intent of this chapter is to try and separate fact from fiction in order to give the reader a better technical understanding of the true hurdles faced by nations that embark on ambitious wind power development programs. Although a technical understanding of wind power systems is not necessary to understand the case studies presented in this book, enhanced technical understanding will help the reader better understand the possibilities and limitations of the technology. This chapter begins by describing the basic components of a wind power system before exploring how technical choices made in regard to system components and site location influence generation costs. From this technical foundation, the discussion will shift to the stochastic (fluctuating) nature of wind power and examine existing solutions for smoothing power fluctuations. This will provide the reader with a better understanding of the potential of wind power systems to replace fossil fuel electricity generation technologies. In concluding sections of this chapter, an attempt will be made to separate truth from fiction in regard to community and environmental impacts commonly attributed to wind power systems. Hopefully, by the end of this chapter, the pros and cons associated with wind power development will be better understood. There are basically two main wind turbine designs—vertical axis and horizontal axis. Vertical axis wind turbines (VAWT), which can resemble egg beaters placed on towers, are not widely used for electricity generation, so this section will focus on the main components of horizontal axis wind turbines (HAWT). The main components of a wind turbine includes the rotor blade; the nacelle (which houses the gearbox, generator, and yaw motor); the tower upon which the wind turbine is placed; the foundation which anchors the tower to the ground; the control system and transformer (usually located at the base of the tower), which transforms the collected energy into electric current that can be delivered to the electricity grid; and the electrical conduits that connect the wind turbine to the electricity grid.
9
Biborski, Mateusz, Marcin Biborski e Janusz Stępiński. "Badania nad technologią wybranych zabytków żelaznych". In Ocalone Dziedzictwo Archeologiczne, 135–44. Wydawnictwo Profil-Archeo; Muzeum im. Jacka Malczewskiego w Radomiu, 2020. http://dx.doi.org/10.33547/oda-sah.10.zn.12.
Testo completoAbstract (sommario):
The extensive programme of research on artefacts recovered from the Przeworsk culture cemetery in Żelazna Nowa, Comm. Magnuszew, included performing a series of metallographic analyses. Only three objects were subjected to the analyses due to their good preservation: two knives and a shield grip fragment. The aim was to determine the technology of manufacture of particular objects and to identify the raw materials from which they were forged. Microstructure was examined using a Leica DMLM metallurgical microscope, and the observed metal structures were photographed. In addition, metal hardness was measured using the Vickers method, with a load of 10 kG (98N). Carbon content of steel was determined based on microscopic observation. As demonstrated by the analyses, the artefacts were made from metal obtained through the bloomery process from bog iron with a significant admixture of phosphorus. The technology used for manufacture of the analysed artefacts was not particularly sophisticated. They were forged from single pieces of bloomery iron. The only exception is a knife (inv. no. CCLII/15), which was forged from two different pieces of metal welded together, namely from a piece of high phosphorus iron and a piece of soft steel. This made the knife more flexible, while rendering its blade sufficiently hard and more resistant to abrasion. One cannot rule out that the blades of both knives were originally hardened by local carburisation, in connection with later thermal processing (quenching). The results of metallographic research seem to support our assumptions. The two knives and the shield grip were manufactured in local Przeworsk culture workshops, perhaps from iron originating from the centre of metallurgy in the Mazowsze (Mazovia) region.
10
Elyaalaoui, Kamal, Moussa Labbadi, Khalid Chigane, Mohammed Ouassaid e Mohamed Cherkaoui. "Operation and Startup of Three-Phase Grid-Connected PWM Inverter for an Experimental Test Bench With DSPACE Real-Time Implementation of PQ Control". In Advances in Environmental Engineering and Green Technologies, 207–32. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-7447-8.ch008.
Testo completoAbstract (sommario):
The main objective of this chapter is the experimental validation of active and reactive power control at the connection point for a three-phase grid connected inverter. It gives an overview on the adopted vector control strategy, regulation of the angle of orientation of the blades (pitch control), synchronization grid side converter to the power network using phase closed loop (PLL). Once the experimental test bench is described, the authors devote a first part to the design of the block circuit diagram of the experimental platform and the control strategy implemented in the DSPace DS1104, and they suggest some steps to associate the inverter to the electrical network. Subsequently, they discuss the experimental results validating the proposed power control. The purpose of this experimental results is the DSPACE real-time implementation of PQ control using three-phase inverter and development of a startup algorithm of the experimental test bench.
Atti di convegni sul tema "Blade grid"
1
Min, Byung-Young, Isaac Wilbur, Sandeep Agarwal, Ramin Modarres, Jinggen Zhao, Jonathan Wong, Brian Wake e Marilyn Smith. "Toward Improved UH-60A Blade Structural Loads Correlation". In Vertical Flight Society 74th Annual Forum & Technology Display, 1–18. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12762.
Testo completoAbstract (sommario):
This study is focused on the improvement of UH-60A blade structural loads correlation with flight and wind-tunnel test data. The blade airloads prediction has been proven to be reasonably good from past studies. However, the blade structural loads, especially the edgewise bending moment, were poorly predicted, and these are the subject of the current study. Several variations of modeling effort have been examined. This includes the drive-train model, refined grid, lag-damper model variation, hub impedance with test stand, tunnel wall, and dis-similar blades. The drive-train and refined grid showed noticeable improvement in edgewise bending moment, but not enough to close the gap between measured data and prediction. A lag damper study indicated that the current nonlinear damper seems to be adequate, and variations to the lag damper had a limited impact to inboard region only. The influence of dis-similar blades provides further insight into the sensitivity of the edgewise bending moment. The largest difference was observed to be due to the presence of the fuselage-like wind tunnel mount, indicating that a rotor analysis should include the fuselage.
2
Zhu, Zheng, e QiJun Zhao. "Numerical Optimization for Rotor Blade-tip Planform with Low HSI Noise Characteristics in Forward Flight". In Vertical Flight Society 71st Annual Forum & Technology Display, 1–9. The Vertical Flight Society, 2015. http://dx.doi.org/10.4050/f-0071-2015-10070.
Testo completoAbstract (sommario):
Based on CFD/FW-H_pds methods and hybrid optimization technique, an optimization design procedure for rotor planform with low HSI noise characteristics is established. In this solver, based on the moving-embedded grid methodology, a CFD simulation method for the aerodynamic characteristics of rotor is developed by solving the compressible Reynolds-averaged Navier-Stokes (RANS) equations. Among the optimization process, the high-qualified blade grids are generated by a high-efficient parameterized method. Additionally, the high-speed impulsive (HSI) noise characteristics generated by transonic helicopter rotor are analyzed through a robust prediction method based on FW-H_pds equations (Ffowcs Williams-Hawkings equations with penetrable data surface). Aiming at the minimization of the noise level in forward flight, optimization analyses based on the rotor blade with double-swept and tapered tip have been accomplished with the aerodynamic performance as constraints. The genetic algorithm and surrogated model based on Latin Hypercube Sampling (LHS) design and Radial Basis Function (RBF) are combined as a hybrid optimization technique. Compared with rectangular blades, it shows that the noise level of rotor with optimized blade-tip shape can be decreased obviously at the present calculating condition. For the rotor with optimized blade-tip, the HSI noise level can be reduced effectively due to its weaker transonic "delocalization" phenomenon in the region of blade-tip.
3
Peng, Li, Zhao Qi-Jun e Zhu Qiu-xian. "CFD Calculations on the Unsteady Aerodynamic Force of Tilt-rotor in Conversion Mode". In Vertical Flight Society 70th Annual Forum & Technology Display, 1–12. The Vertical Flight Society, 2014. http://dx.doi.org/10.4050/f-0070-2014-9422.
Testo completoAbstract (sommario):
In order to calculate the unsteady aerodynamic force of tilt-rotor in conversion mode, VBM (Virtual Blade Model), RBM (Real Blade Model) and HBM (Hybrid Blade Model) are established respectively. A new multi-layer moving-embedded grid technique is presented to reduce the numerical dissipation of the tilt-rotor wake. In this method, grid generated abound the rotor accounts for rigid blade motions and a new searching scheme is implemented to search suitable donor elements in moving-embedded grids to translate information between the viscous flow and inviscid flow zones. In these CFD methods, a dual-time method is employed to fulfil the calculation of unsteady flowfield of tilt-rotor, and a second-order centred difference scheme by introducing artificial viscosity is used to calculate the flux. In order to improve the computing efficiency, the SMPD model parallel acceleration technology adopted, according to the characteristics of the current grid system. The lift and drag distributions of NACA0012 airfoil, the dynamic pressure distributions on a typical rotor and the sectional pressure distributions on XV-15 tilt-rotor in hovering flight are calculated respectively, and the developed VBM and RBM model are validated by comparing the calculated results with available experimental data. Then, unsteady aerodynamic force and flowfield of XV-15 tilt-rotor in different modes, such as fixed conversion mode at different tilt angles (15-deg, 30-deg, 60-deg), and full conversion cases from 0-deg to 90-deg, are numerically simulated by the VBM/RBM/HBM respectively. By analyses and comparisons on the simulated results about unsteady aerodynamic forces of tilt-rotor in different modes, some meaningful conclusions about distorted blade-tip vortex distribution and unsteady aerodynamic force variation in conversion mode are obtained, and these investigated results could provide a good foundation for tilt-rotor aircraft design in the future.
4
Xi, Chen, e Zhao Qi-jun. "Aerodynamic Performance Analysis for Iced Rotor based on New Three-Dimensional Rotor Icing Model". In Vertical Flight Society 72nd Annual Forum & Technology Display, 1–12. The Vertical Flight Society, 2016. http://dx.doi.org/10.4050/f-0072-2016-11376.
Testo completoAbstract (sommario):
A new numerical method for predicting ice accretion on helicopter rotor is established. The ice amount is calculated using a coupling method of 3-D CFD and 3-D icing model. Firstly, the orthogonal and body-fitted grids are generated around rotor blade by interpolating and folding approach of section airfoil grid. Then, the CFD simulation method for 3-D flowfield around the blade is established by solving the unsteady RANS equations with Spalart-Allmaras turbulence model. Based on the Eulerian approach, the conservation equations of mass and momentum are solved to obtain the droplet flowfield properties on the same grid used in CFD simulations, and the multistage Runge-Kutta scheme is employed in the temporal discretization. Followed that, combined with the characters of rotor blade motion, a 3-D icing model considering the influences of the centrifugal force, the movement of water film and the variation of the azimuthal angle is put forward. The comparisons between the calculated results and experimental data about the ice accretion on rotor in hover and in forward flight indicate that the present method is effective. At last, the effects of the atmospheric temperature on the icing process and the aerodynamic performance of the iced rotor are analyzed. At the warmer sub-freezing temperatures, ice is not easy to form near the blade tip, and blade sectional lift along the spanwise direction from 45% to 65%R is decreased obviously. There is a significant deterioration in the rotor required power and the lift coefficient with temperature dropping, resulting in the decrease of the Figure of Merit of rotor in hover (FM is reduced by about 7.1% at the temperature of -28°C).
5
Zagitov, R. A., A. N. Dushko e Yu N. Shmotin. "Automatic Three Dimensional Grid Generation in Turbo Machine Blade Passages". In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-27127.
Testo completoAbstract (sommario):
Generation of the grid for blade passages with packaging using universal grid generators usually takes much time. The paper is devoted to grid generation in turbo machine blade passages with packaging in automatic mode. The main requirement to the approach is to obtain the grid with minimum engineer participant. In the developed procedure engineer must specify only general input data: number of nodes, cell size near solid bodies and geometrical data. Multiblock structured grids are considered. All grid blocks have node-to-node attachment between each other; periodicity is also specified from node to node. The grid in blade passage consists of two blocks: “O” grid around blade and “H” grid in blade passage. Additional blocks are used to describe different ZR-effects such us tip clearances, leakage seals and bleed air systems. A variational method of constructing three dimensional grids composed of hexahedral cells is applied. The combination of the energy density functional and cell size functional is used. The first functional lets us control the shapes and the second functional lets us control the sizes of grid cells. Grid untangling procedure is also developed. Developed approach was tested using the blades of axial and centrifugal compressors and axial turbines. Results of grid generation are presented.
6
Groth, Pieter, Hans Mårtensson e Lars-Erik Eriksson. "Validation of a 4D Finite Volume Method for Blade Flutter". In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-429.
Testo completoAbstract (sommario):
A finite volume method for blade flutter analyses, using moving grids is presented and partly validated. The method which solves the unsteady three-dimensional Euler equations is formulated in the four-dimensional time-space domain. An algebraic grid generation technique based on transfinite interpolation is used to move and deform the grid to conform to the blade motion. Fluxes are calculated using a third-order upwind-biased scheme. For time marching both an explicit three-stage Runge-Kutta scheme and a Crank-Nicolson scheme is used. Internal and external flows are calculated using the present method. Calculated results agree well with the corresponding experiments and with results obtained using other methods.
7
Arnone, Andrea, Ennio Carnevale e Michele Marconcini. "Grid Dependency Study for the NASA Rotor 37 Compressor Blade". In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-384.
Testo completoAbstract (sommario):
The NASA Rotor 37 has been computed by several authors in the last few years with relative success. The aim of this work is to present a systematic grid dependency study in order to quantify the amount of uncertainty that comes from the grid density. The computational domain is divided onto several regions (i.e. leading edge, trailing edge, shear layer …) and for each of them, the impact of the grid density is investigated. By means of this analysis, substantial improvement has been obtained in the prediction of efficiency and exit angle. On the contrary, the improvement achieved in total pressure and total temperature ratio is less remarkable. It is believed that only after a systematic grid dependency study can the contribution of turbulence modeling, laminar-turbulent transition, and boundary conditions be analyzed with success.
8
Mondal, Pranab, e Joseph Mathew. "Large Eddy Simulation of a Compressor Stage". In ASME 2017 Gas Turbine India Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gtindia2017-4849.
Testo completoAbstract (sommario):
A methodology for large eddy simulation (LES) of a turbomachine stage is presented. Computations of mean fields (RANS) of stages may be performed separately of rotor and stator rows by providing an averaged solution as input to the down-stream row. In unsteady simulations, unsteady field information must be exchanged in both directions after every time step. Here a procedure for linear cascade simulations of a stage has been implemented in a high-resolution compressible flow solver for LES. The LES uses an explicit filtering method for sub-grid-scale modelling. Grids overlap at the interface between blade rows. Field data is transferred in both directions. Rotor velocity is added or subtracted as needed to tangential velocity component during this transfer. The relative movement of the rotor and stator grids is accounted for by suitable periodic tangential shifting of the paired grid points in the overlap for the transfer. The method has been tested against a published DNS of a statorrotor stage. The Reynolds number based on blade chord and mean axial velocity at inflow was 40000. Solution fields show the wake vortex street of the upstream blade row impinging on downstream blades and being convected through the downstream blade passage. The LES captured transition on rotor blade surface boundary layers. Blade surface pressure distributions agree closely on pressure surfaces. Separation and transition on downstream blade suction surface is delayed slightly at the present resolution, but this will improve with grid refinement, monotonically, for this LES method.
9
Petriaszwili, Georgij, Piotr Janicki e Serhii Komarov. "Investigations on book cutting by circular knife with eccentric blade movement". In 10th International Symposium on Graphic Engineering and Design. University of Novi Sad, Faculty of technical sciences, Department of graphic engineering and design,, 2020. http://dx.doi.org/10.24867/grid-2020-p24.
Testo completoAbstract (sommario):
The paper describes investigations on new method of the book cutting by using special circular knife with eccentric blade movement. Analysis of kinematic parameters of book block cutting shows, that by using eccentric circular cutting knife the cutting process may be realized in two different modes: continuous cutting – with the constant contact between cutting edge and cut material, and interrupted cutting process - with the impulse cutting knife action to treated material. The results of the conducted experimental studies confirm the kinematic analysis of the cutting process.
10
Iwase, Taku, Kazuyuki Sugimura e Ryuuichi Shimada. "Technique for Designing Forward Curved Bladed Fans Using Computational Fluid Dynamics and Numerical Optimization". In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98136.
Testo completoAbstract (sommario):
We developed a technique for designing forward curved bladed fans using computational fluid dynamics (CFD) and numerical optimization. The target is a forward curved bladed fan including an impeller with blades and a volute casing. In our research, we developed a two-step calculation method with a blade-to-blade grid model and a full grid model. Using these models individually according to purpose, we reduced the design time by one quarter. An automatic grid-generation program that was developed in-house generated the grids for the CFD calculation. The fan performance was calculated using commercial CFD software based on an incompressible Reynolds-averaged Navier-Stokes (RANS) solver. For numerical optimization, we used a simulated annealing algorithm (SA) to determine the optimized design variables. Using the developed technique, we attempted to minimize the total pressure loss of an impeller and a suction cone. We could obtain the optimized design variables: the gap between the impeller and suction cone, the inside diameter of the shroud rim cover and the number of blades. Our results demonstrated that the optimized fan design had smaller shaft power than the initial design, especially at the low flow rate. Clearly therefore, our technique is capable of designing an energy saving fan in a short time. Moreover, it was found that that the leak flow between the impeller and suction cone of the optimized fan was suppressed. The change in these design variables contributed to this suppression.