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1
Gutiérrez, R., E. Llorente i D. Ragni. "Induced stalled flow due to roughness sensitivity for thick airfoils in modern wind turbines". Journal of Physics: Conference Series 2151, nr 1 (1.01.2022): 012001. http://dx.doi.org/10.1088/1742-6596/2151/1/012001.
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Abstract The mid-span region of wind turbine blades can be thickened to fulfil the structural requirements of the blade. Hence, thick airfoils, that were designed to operate at the root region of the blade, are moved to the mid-span region. This could not imply remarkable variations of the blade performance once its surface is smooth. However, the sensitivity of thick airfoils to roughness could cause significant aerodynamic impacts such as flow separation. This research aims to quantify the impact of the blade thickness, under smooth and rough conditions, in the annual energy production and the fatigue loads of the blade. Ten blade designs, linearly interpolated in thickness, are studied employing aero-elastic computations. The results reveal that the thickest blade increases the annual energy production by 5% with respect to the thinnest blade under rough conditions. Whereas this increase is less than 1% under smooth conditions. The loss of annual energy production varies with the blade thickness linearly for thin blades while it varies exponentially for thick blades up to 22%. Fatigue loads assessment confirmed a reduction of the damage equivalent load under smooth conditions, whereas the thickest blade increased it 28% under rough conditions.
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Lu, Lei, i Li Da Zhang. "3D Geometric Modeling of Francis Turbine Blades Based on Wooden Patterns and UG Software". Applied Mechanics and Materials 596 (lipiec 2014): 606–9. http://dx.doi.org/10.4028/www.scientific.net/amm.596.606.
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To quickly and easily get a smooth and accurate 3D model of blades, This paper was based on the two-dimensional wooden patterns of the existing francis turbine blades in "AutoCAD", by importing UG software platform, directly translating two-dimensional lines to get three-dimensional wooden patterns, without calculating the spatial coordinates of distribution points on the blade section lines, obtaining the optimized smooth pressure sides and suction sides of the blades by characteristic surface intersecting lines, after partial rounding and sewing the sheets, the process of three-dimensional modeling of blades was finally completed. This takes a solid foundation for hydraulic performance prediction and CFD numerical simulation analysis of the francis turbine. The blade modeling method described in this article has some reference value.
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Zhang, Si Qing, Guo Hua Ma, Yun Long Zhang i Dong Wang. "Hydraulic Turbine Blades Modeling Based on Two-Dimensional Wooden Patterns". Advanced Materials Research 860-863 (grudzień 2013): 1521–24. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.1521.
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There are many difficulties to design, processing and research on numerical simulation for Francis turbine because of the complexity of blade shape and the difficulty of solid modeling. Based on two-dimensional wooden patterns of Francis turbine blades, this article aims to complete blades three-dimensional modeling for Francis turbine runner with long and short blades by means of Pro-E software which has powerful 3D modeling function. After comparing three kinds of available methods to generate blade across section which provided by Pro-E, finally completed blades three-dimensional modeling by method of generating across section with point files, established a smooth and accurate three-dimensional model. The method provides an accurate physical model for the numerical simulation of the Francis turbine with long and short blades, as well as provides a feasible approach for hydro-mechanical blades modeling.
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Siddappaji, Kiran, i Mark G. Turner. "Versatile Tool for Parametric Smooth Turbomachinery Blades". Aerospace 9, nr 9 (31.08.2022): 489. http://dx.doi.org/10.3390/aerospace9090489.
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Designing blades for efficient energy transfer by turning the flow and angular momentum change is both an art and iterative multidisciplinary engineering process. A robust parametric design tool with few inputs to create 3D blades for turbomachinery and rotating or non-rotating energy converters is described in this paper. The parameters include axial–radial coordinates of the leading/trailing edges, construction lines (streamlines), metal angles, thickness-to-chord ratio, standard, and user-defined airfoil type among others. Using these, 2D airfoils are created, conformally mapped to 3D stream surfaces, stacked radially with multiple options, and they are transformed to a 3D Cartesian coordinate system. Smooth changes in blade curvature are essential to ensure a smooth pressure distribution and attached flow. B-splines are used to control meanline curvature, thickness, leading edge shape, sweep-lean, and other parameters chordwise and spanwise, making the design iteration quick and easy. C2 curve continuity is achieved through parametric segments of cubic and quartic B-splines and is better than G2. New geometries using an efficient parametric scheme and minimal CAD interaction create watertight solid bodies and optional fluid domains. Several examples of ducted axial and radial turbomachinery with special airfoil shapes or otherwise, unducted rotors including propellers and wind and hydrokinetic turbines are presented to demonstrate versatility and robustness of the tool and can be easily tied to any automation chain and optimizer.
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Thilmany, Jean. "Smooth Operator". Mechanical Engineering 124, nr 07 (1.07.2002): 46–48. http://dx.doi.org/10.1115/1.2002-jul-4.
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This article reviews finite element analysis (FEA) that helped Boeing to eliminate oiled bearings on its Chinook helicopter. The pitch-hinge assembly on the helicopter permits the blade to rotate on its longitudinal axis and to control thrust, which determines where the helicopter is going. In other words, it dictates the pitch of the rotor blades and is one of the most important hinges on the craft. About 2 years ago, Boeing sought to redesign the pitch-hinge assembly to replace the bearings with a self-lubricated hinge. FEA is the use of a complex system of points, called nodes that form a grid, or mesh, across a computer-aided design model. The mesh contains the material and structural properties that define how the part will react to certain load conditions. In essence, FEA is a numerical method used to solve a variety of engineering problems that involve stress, heat transfer, electromagnetism, and fluid flow.
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Boynton, J. L., R. Tabibzadeh i S. T. Hudson. "Investigation of Rotor Blade Roughness Effects on Turbine Performance". Journal of Turbomachinery 115, nr 3 (1.07.1993): 614–20. http://dx.doi.org/10.1115/1.2929298.
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The cold air test program was completed on the SSME (Space Shuttle Main Engine) HPFTP (High-Pressure Fuel Turbopump) turbine with production nozzle vane rings and polished coated rotor blades with a smooth surface finish of 30 μin. (0.76 μm) rms (root mean square). The smooth blades were polished by an abrasive flow machining process. The test results were compared with the air test results from production rough-coated rotor blades with a surface finish of up to 400 μin. (10.16 μm) rms. Turbine efficiency was higher for the smooth blades over the entire range tested. Efficiency increased 2.1 percentage points at the SSME 104 percent RPL (Rated Power Level) conditions. This efficiency improvement could reduce the SSME HPFTP turbine inlet temperature by 57 R (32 K), increasing turbine durability. The turbine flow parameter increased and the midspan outlet swirl angle became more axial with the smooth rotor blades.
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Chen, Jian Ping, Li Xin Huo i Hai Jun Li. "Failure Diagnosis of Large Cooling Tower Fan Based on FFT and EMD Analysis Method". Advanced Materials Research 694-697 (maj 2013): 1139–45. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.1139.
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Large cooling tower fan mainly used in petroleum, chemical, electric power industry, carries industrial water circulating cooling function and its operational status directly affects the industrial production. The blades are the important parts of the fan. The modal analysis is used to find the distribution of blade vibration frequency, and then the acquisition and analysis of vibration parameters of running large cooling tower fan blades are done using the EMD methods. Finally, compare with the modal analysis to find out safety hazards of fan blades. This method can eliminate the failures of the cooling tower fan blades, shorten the repair cycle, ensure the smooth production of the enterprise and improve economic efficiency.
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Gu, Yun Qing, Zheng Zan Shi, Jie Gang Mou, Hao Shuai Wang i Pei Jian Zhou. "Non-Smooth Surface Flow Drag Reduction Characteristics of Centrifugal Pump Impeller". International Journal of Engineering Research in Africa 24 (czerwiec 2016): 44–56. http://dx.doi.org/10.4028/www.scientific.net/jera.24.44.
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In order to improve the efficiency of centrifugal pump, based on the bionics principle, established non-smooth surfaces of various groove structure on the centrifugal pump impeller. The internal flow field of it was numerically simulated through RNG k-ε turbulence model. Research the drag reduction characteristics of non-smooth impeller in different groove shape and arrangement. The results showed that the biggest drag reduction rate of centrifugal pump with non-smooth blades is about 6.22%. The blades of non-smooth unit can effectively inhibit the near wall boundary layer flow state, reduce the shear stress on blades wall, reduce the internal fluid turbulent degree of centrifugal pump, so that the fluid flow in centrifugal pump impeller is more stable, improve the efficiency of centrifugal pump.
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Růžička, Milan, Josef Jurenka, Martin Nesládek i Ján Džugan. "Fatigue Strength Simulation and Prediction of a Turbine Blade". Key Engineering Materials 627 (wrzesień 2014): 229–32. http://dx.doi.org/10.4028/www.scientific.net/kem.627.229.
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Fatigue strength prediction methods of blades of a high pressure steam turbine are the main topic of this article. Experimental approaches, as well as use of the experimental results for the verification of the finite element method (FEM) and fatigue models, were performed on two basic levels. First, verification by the fatigue tests of smooth and notched cylindrical specimens under room and service conditions was performed. Second, verification of the real blade fatigue limit prediction was conducted. These tests were carried out using special test stand under the typical combined blades loading. Appropriate uniaxial and multiaxial fatigue criteria were applied. Achieved results were finally used in the process of the fatigue strength prediction of rotor blades.
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Li, Mo, Yuwang Yang, Li Guo, Donghui Chen, Hongliang Sun i Jin Tong. "Design and Analysis of Bionic Cutting Blades Using Finite Element Method". Applied Bionics and Biomechanics 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/471347.
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Praying mantis is one of the most efficient predators in insect world, which has a pair of powerful tools, two sharp and strong forelegs. Its femur and tibia are both armed with a double row of strong spines along their posterior edges which can firmly grasp the prey, when the femur and tibia fold on each other in capturing. These spines are so sharp that they can easily and quickly cut into the prey. The geometrical characteristic of the praying mantis’s foreleg, especially its tibia, has important reference value for the design of agricultural soil-cutting tools. Learning from the profile and arrangement of these spines, cutting blades with tooth profile were designed in this work. Two different sizes of tooth structure and arrangement were utilized in the design on the cutting edge. A conventional smooth-edge blade was used to compare with the bionic serrate-edge blades. To compare the working efficiency of conventional blade and bionic blades, 3D finite element simulation analysis and experimental measurement were operated in present work. Both the simulation and experimental results indicated that the bionic serrate-edge blades showed better performance in cutting efficiency.
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Katrenko, M., V. Borsch i O. Kulyk. "Approximation of blades of radial machines with multiparameter family of smooth surfaces". Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu, nr 6 (25.12.2022): 68–75. http://dx.doi.org/10.33271/nvngu/2022-6/068.
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Purpose. Development of a mathematical model for creating the spatial forms of blade devices of rotating radial dynamic blade machines. Methodology. An approach to the development of a mathematical model of blade profiling of radial dynamic blade machines, as parts of power plants, air-jet engines and fuel component supply systems of rocket engines, has been suggested. The approach is based on a physical model of the working body flow over helical surfaces. Findings. A system of equations for describing the blade of a radial dynamic blade machine of any purpose as a family of smooth surfaces has been obtained. A multi-parameter correction of the shape of the smooth surface of the blade, accounting for the change in geometric data, based on input and output parameters of the blade, has been developed. Based on a review of modern technology samples, possible configurations of the spatial shape of the blade of the radial and radial-axial type, geometric factors affecting the surface of the blade being created are taken into account. The possibility of obtaining a multi-level blade apparatus by changing the conditions of the geometric parameters at the entrance is shown. Originality. As part of the developed approach, in relation to the conditions for ensuring the calculated geometric parameters and the working process conditions of the blade machine, blade machines operating on compressible and non-compressible working bodies are considered. In particular, the possibility is shown of ensuring the construction of the spatial surface of the blade of the impellers of radial blade machines with a wide range of angles of the blades at the entrance and exit using smooth surfaces. Practical value. The use of a developed mathematical method allows you to perform the profile of rotating vane devices for radial vane dynamic machines of various purposes, such as centrifugal pumps and compressors, centrifugal radial turbines, as well as diagonal type vane machines. The practical significance of the obtained results is determined by the use of dynamic radial vane machines in aviation and rocket technology, aggregates of the mining industry, and technological devices of chemical industry enterprises.
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Tangler, J. L. "Influence of Pitch, Twist, and Taper on a Blade’s Performance Loss due to Roughness". Journal of Solar Energy Engineering 119, nr 3 (1.08.1997): 248–52. http://dx.doi.org/10.1115/1.2888027.
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The purpose of this study was to determine the influence of blade geometric parameters such as pitch, twist, and taper on a blade’s sensitivity to leading edge roughness. The approach began with an evaluation of available test data of performance degradation due to roughness effects for several rotors. In addition to airfoil geometry, this evaluation suggested that a rotor’s sensitivity to roughness was also influenced by the blade geometric parameters. Parametric studies were conducted using the PROP93 computer code with wind tunnel airfoil characteristics for smooth and rough surface conditions to quantify the performance loss due to roughness for tapered and twisted blades relative to a constant-chord nontwisted blade at several blade pitch angles. The results indicate that a constant-chord nontwisted blade pitched toward stall will have the greatest losses due to roughness. The use of twist, taper, and positive blade-pitch angles all help reduce the angle-of-attack distribution along the blade for a given wind speed and the associated performance degradation due to roughness.
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Samsher. "Comparison between loss coefficients of smooth, smooth-thickened, and rough-thickened axial turbine blades". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 221, nr 4 (czerwiec 2007): 575–82. http://dx.doi.org/10.1243/09576509jpe380.
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Yirijor, John, i Nana Asabere Siaw-Mensah. "Design and Optimisation of Horizontal Axis Wind Turbine Blades Using Biomimicry of Whale Tubercles". Journal of Engineering Research and Reports 25, nr 5 (5.07.2023): 100–112. http://dx.doi.org/10.9734/jerr/2023/v25i5915.
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Wind speed is the major factor in generating power in a wind turbine. However, due to the non-optimum and redundant design of wind turbine blades, not nearly enough wind is captured for utilization. In the present study, modifications were done on the leading edge of the HAWT blade using tubercles showing their effects on aerodynamic performances. From this research, the following results found concerning the performances of HAWT with leading-edge tubercles were that; blades with tubercles on the leading edge will have superior performance in the post-stall regime by 27%, tubercles with a smaller amplitude and lower wavelength will produce higher lift and lower drag in the low wind speed condition, and tubercle blade will have a stable and smooth performance in varying wind speed conditions, producing higher torque and power at low wind speed. Using a small wind turbine model, SolidWorks Motion Analysis Simulation was used for dynamic modeling to evaluate and determine the force and torque of the mechanical structure. These results were compared and examined using standard wind turbine blades which showed an improvement of 30% in efficiency.
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Cen, Hai Tang, i Jian Lan Liu. "Bionic Design Review of Wind Turbine Blades". Advanced Materials Research 512-515 (maj 2012): 599–603. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.599.
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With the power increase of the wind turbine, the scale of the blade is increasing, further improving the performance of the blade, improving the stiffness and stability of the blade, inhibiting the vibration and noise of the blade and reducing the blade weight has become an problem urgently needed to be solved with for the design of the large wind turbine blade. The unique external shape of organisms, the perfect unity of the function, structure and material, the excellent capability for adapting the environment, also provides an inexhaustible inspiration for the bionic design of wind turbine. Applying the biological non-smooth and self-cleaning effect and imitating the biological medial axis pattern structure, self-adaptive characteristics conduct the bionic design of the wind turbine blade, it can effectively realize drag-reduction and lift enhancement for the blades, noise reduction, lightweight, and can improve the self-adaptive ability, resisting wind and sand, preventing icing up. Paying attention to research on biological mechanism, perfecting the bionic design theory, implementing the multidisciplinary design optimization, strengthening the research on model, have an important significance on improving the bionic design effect for the wind turbine blade and promoting the bionic engineering application.
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Kaya, Mustafa. "A CFD Based Application of Support Vector Regression to Determine the Optimum Smooth Twist for Wind Turbine Blades". Sustainability 11, nr 16 (20.08.2019): 4502. http://dx.doi.org/10.3390/su11164502.
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Computational fluid dynamics (CFD) is a powerful tool to estimate accurately the aerodynamic loads on wind turbine blades at the expense of high requirements like the duration of computation. Such requirements grow in the case of blade shape optimization in which several analyses are needed. A fast and reliable way to mimic the CFD solutions is to use surrogate models. In this study, a machine learning technique, the support vector regression (SVR) method based on a set of CFD solutions, is used as the surrogate model. CFD solutions are calculated by solving the Reynolds-averaged Navier–Stokes equation with the k-epsilon turbulence model using a commercial solver. The support vector regression model is then trained to give a functional relationship between the spanwise twist distribution and the generated torque. The smooth twist distribution is defined using a three-node cubic spline with four parameters in total. The optimum twist is determined for two baseline blade cases: the National Renewable Energy Laboratory (NREL) Phase II and Phase VI rotor blades. In the optimization process, extremum points that give the maximum torque are easily determined since the SVR gives an analytical model. Results show that it is possible to increase the torque generated by the NREL VI blade more than 10% just by redistributing the spanwise twist without carrying out a full geometry optimization of the blade shape with many shape-defining parameters. The increase in torque for the NREL II case is much higher.
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Fancello, Matteo, Marco Morandini i Pierangelo Masarati. "Helicopter Rotor Sailing by Non-Smooth Dynamics Co-Simulation". Archive of Mechanical Engineering 61, nr 2 (15.08.2014): 253–68. http://dx.doi.org/10.2478/meceng-2014-0015.
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Abstract This paper presents the application of a co-simulation approach for the simulation of frictional contact in general-purpose multibody dynamics to a rotorcraft dynamics problem. The proposed approach is based on the co-simulation of a main problem, which is described and solved as a set of differential algebraic equations, with a subproblem that is characterized by nonsmooth dynamics events and solved using a timestepping technique. The implementation and validation of the formulation is presented. The method is applied to the analysis of the droop and anti-flap contacts of helicopter rotor blades. Simulations focusing on the problem of blade sailing are conducted to understand the behavior and assess the validity of the method. For this purpose, the results obtained using a contact model based on Hertzian reaction forces at the interface are compared with those of the proposed approach.
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Kinnas, Spyros A., HanSeong Lee i Yin L. Young. "Modeling of Unsteady Sheet Cavitation on Marine Propeller Blades". International Journal of Rotating Machinery 9, nr 4 (2003): 263–77. http://dx.doi.org/10.1155/s1023621x03000241.
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Unsteady sheet cavitation is very common on marine propulsor blades. The authors summarize a lifting-surface and a surface-panel model to solve for the unsteady cavitating flow around a propeller that is subject to nonaxisymmetric inflow. The time-dependent extent and thickness of the cavity were determined by using an iterative method. The cavity detachment was determined by applying the smooth detachment criterion in an iterative manner. A nonzeroradius developed vortex cavity model was utilized at the tip of the blade, and the trailing wake geometry was determined using a fully unsteady wake-alignment process. Comparisons of predictions by the two models and measurements from several experiments are given.
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K, RANGASAMY, MUTHAMILSELVAN M i SUDAGAR I P. "Development and performance evaluation of a manual fruit harvester". Madras Agricultural Journal 89, june (2002): 253–56. http://dx.doi.org/10.29321/maj.10.a00212.
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The conventional methods used for harvesting fruits are crude, laborious and time consuming. The fruit harvesting systems employing vibratory mechanism and mechanical harvesting prevalent in the advanced countries cannot be adopted in Indian conditions. With a view of simplifying the fruit harvesting operation, a manual fruit harvester was developed and tested. Three types of blade viz. curved blade, V-shaped blade and scissor type blade were fabricated and attached with the harvester. The field capacity and good fruit percentage by the three blades were determined for five important fruit crops. The combination of V-shaped harvester for pomegranate fruit gave maximum field capacity. The good fruit percentage was found to be more in lime. Guava was subjected to maximum damage due to its soft and smooth skin.
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Zhang, Jun-Qiu, Zhi-Wu Han, Hui-Na Cao, Wei Yin, Shi-Chao Niu i Hui-Yuan Wang. "Numerical Analysis of Erosion Caused by Biomimetic Axial Fan Blade". Advances in Materials Science and Engineering 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/254305.
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Damage caused by erosion has been reported in several industries for a wide range of situations. In the present work, a new method is presented to improve the erosion resistance of machine components by biomimetic method. A numerical investigation of solid particle erosion in the standard and biomimetic configuration blade of axial fan is presented. The analysis consists in the application of the discrete phase model, for modeling the solid particles flow, and the Eulerian conservation equations to the continuous phase. The numerical study employs computational fluid dynamics (CFD) software, based on a finite volume method. User-defined function was used to define wear equation. Gas/solid flow axial fan was simulated to calculate the erosion rate of the particles on the fan blades and comparatively analyzed the erosive wear of the smooth surface, the groove-shaped, and convex hull-shaped biomimetic surface axial flow fan blade. The results show that the groove-shaped biomimetic blade antierosion ability is better than that of the other two fan blades. Thoroughly analyze of antierosion mechanism of the biomimetic blade from many factors including the flow velocity contours and flow path lines, impact velocity, impact angle, particle trajectories, and the number of collisions.
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Morris, W. D., i S. W. Chang. "Heat transfer in a radially rotating smooth-walled tube". Aeronautical Journal 102, nr 1015 (maj 1998): 277–86. http://dx.doi.org/10.1017/s0001924000065313.
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SummaryThis paper describes a detailed experimental investigation of turbulent heat transfer in a radially rotating tube with particular reference to its application to the design of cooled turbine rotor blades. The paper focuses on the strategy adopted, the description of the apparatus used, the method of data processing and a selection of measurements which illustrate the manner by which Coriolis force and centripetal buoyancy force interactively affect the local heat transfer along the leading and trailing edges of the tube.As well as re-confirming the fact that Coriolis force and centripetal buoyancy have a significant influence on the forced convection mechanism present due to the through flow, a number of new experimentally-based observations are presented. An empirical correlation, which is physically consistent, has been developed which permits the interactive effect of Coriolis force and centripetal buoyancy on forced convection to be evaluated and quantified.The work has been motivated by the need to understand the general effect of rotation on the performance of the internal cooling airways used in gas turbine rotor blades.
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Parker, Michael, i Douglas Bohl. "Experimental Investigation of Finite Aspect Ratio Cylindrical Bodies for Accelerated Wind Applications". Fluids 5, nr 1 (17.02.2020): 25. http://dx.doi.org/10.3390/fluids5010025.
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The placement of a cylindrical body in a flow alters the velocity and pressure fields resulting in a local increase in the flow speed near the body. This interaction is of interest as wind turbine rotor blades could be placed in the area of increased wind speed to enhance energy harvesting. In this work the aerodynamic performance of two short aspect ratio (AR = 0.93) cylindrical bodies was evaluated for potential use in “accelerated wind” applications. The first cylinder was smooth with a constant diameter. The diameter of the second cylinder varied periodically along the span forming channels, or corrugations, where wind turbine blades could be placed. Experiments were performed for Reynolds numbers ranging from 1 × 105 to 9 × 105. Pressure distributions showed that the smooth cylinder had lower minimum pressure coefficients and delayed separation compared to the corrugated cylinder. Velocity profiles showed that the corrugated cylinder had lower peak speeds, a less uniform profile, and lower kinetic energy flux when compared to the smooth cylinder. It was concluded that the smooth cylinder had significantly better potential performance in accelerated wind applications than the corrugated cylinder.
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Hosseini, Seyed Farhad, i Behnam Moetakef-Imani. "Innovative approach to computer-aided design of horizontal axis wind turbine blades". Journal of Computational Design and Engineering 4, nr 2 (18.11.2016): 98–105. http://dx.doi.org/10.1016/j.jcde.2016.11.001.
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Abstract The design of horizontal axis wind turbine (HAWT) blades involves several geometric complexities. As a result, the modeling of these blades by commercial computer-aided design (CAD) software is not easily accomplished. In the present paper, the HAWT blade is divided into structural and aerodynamic surfaces with a G1 continuity imposed on their connecting region. The widely used method of skinning is employed throughout the current work for surface approximation. In addition, to ensure the compatibility of section curves, a novel approach is developed based on the redistribution of input airfoil points. In order to evaluate deviation errors, the Hausdorff metric is used. The fairness of surfaces is quantitatively assessed using the standard strain energy method. The above-mentioned algorithms are successfully integrated into a MATLAB program so as to enhance further optimization applications. The final surfaces created by the procedure developed during the present study can be exported using the IGES standard file format and directly interpreted by commercial CAD and FE software. Highlights A new skinning approach is presented based on redistribution of input data points. The developed skinning method is successfully applied to the design of horizontal axis wind turbine blades. It has been shown that the blade surface constructed using the developed method is fair and visually pleasing. Special attention has been paid to construct a smooth surface in the transition area between the root and the section with maximum chord.
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Takeishi, Kenichiro. "Evolution of Turbine Cooled Vanes and Blades Applied for Large Industrial Gas Turbines and Its Trend toward Carbon Neutrality". Energies 15, nr 23 (25.11.2022): 8935. http://dx.doi.org/10.3390/en15238935.
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Photovoltaics and wind power are expected to account for a large share of power generation in the carbon-neutral era. A gas turbine combined cycle (GTCC) with an industrial gas turbine as the main engine has the ability to rapidly start up and can follow up to load fluctuations to smooth out fluctuations in power generation from renewable energy sources. Simultaneously, the system must be more efficient than today’s state-of-the-art GTCCs because it will use either Carbon dioxide Capture and Storage (CCS) when burning natural gas or hydrogen/ammonia as fuel, which is more expensive than natural gas. This paper describes the trend of cooled turbine rotor blades used in large industrial gas turbines that are carbon neutral. First, the evolution of cooled turbine stationary vanes and rotor blades is traced. Then, the current status of heat transfer technology, blade material technology, and thermal barrier coating technology that will lead to the realization of future ultra-high-temperature industrial gas turbines is surveyed. Based on these technologies, this paper introduces turbine vane and blade cooling technologies applicable to ultra-high-temperature industrial gas turbines for GTCC in the carbon-neutral era.
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Arias-Rojas, Heriberto, Miguel A. Rodríguez-Velázquez, Ángel Cerriteño-Sánchez, Francisco J. Domínguez-Mota i Sergio R. Galván-González. "A FEM Structural Analysis of a Francis Turbine Blade Parametrized Using Piecewise Bernstein Polynomials". Computation 11, nr 7 (26.06.2023): 123. http://dx.doi.org/10.3390/computation11070123.
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Several methodologies have successfully described the runner blade shape as a set of discrete sections joining the hub and shroud, defined by 3D geometrical forms of considerable complexity. This task requires an appropriate parametric approach for its accurate reconstruction. Among them, piecewise Bernstein polynomials have been used to create parametrizations of twisted runner blades by extracting some cross-sectional hydrofoil profiles from reference CAD data to be approximated by such polynomials. Using the interpolating polynomial coefficients as parameters, more profiles are generated by Lagrangian techniques. The generated profiles are then stacked along the spanwise direction of the blade via transfinite interpolation to obtain a smooth and continuous representation of the reference blade. This versatile approach makes the description of a range of different blade shapes possible within the required accuracy and, furthermore, the design of new blade shapes. However, even though it is possible to redefine new blade shapes using the aforementioned parametrization, a remaining question is whether the parametrized blades are suitable as a replacement for the currently used ones. In order to assess the mechanical feasibility of the new shapes, several stages of analysis are required. In this paper, bearing in mind the standard hydraulic test conditions of the hydrofoil test case of the Norwegian Hydropower Center, we present a structural stress–strain analysis of the reparametrization of a Francis blade, thus showing its adequate computational performance in two model tests.
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Lastivka, Ivan. "RAISING GAS-DYNAMIC STABILITY MARGIN OF AXIAL AND CENTRIFUGAL COMPRESSOR STAGES BY MEANS OF VANED DIFFUSER BOUNDARY LAYER CONTROL / DUJŲ DINAMINIO STABILUMO RIBOS AŠINIO IR IŠCENTRINIO KOMPRESORIAUS PAKOPOSE DIDINIMAS ATLIEKANT STABILIZUOTO DIFUZORIAUS PARIBIO SLUOKSNIO KONTROLĘ". Aviation 15, nr 3 (4.10.2011): 76–81. http://dx.doi.org/10.3846/16487788.2011.624262.
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Generalised research results that consider the upgradability of axial and centrifugal gas turbine engine compressors by means of gas-dynamic boundary layer control on bladed disks are demonstrated. Active and passive methods are used. Comparative analysis of the results has been carried out. The analysis is purposed to determine the influence of the flow circulation around the aerofoils on the performance of compressor single-row bladed disks with smooth blades and rough blades and under the condition that vortex generators are installed. An increase in the efficiency of aviation gas-turbine engines and in their gas-dynamic stability margin support leads to the enhancement of the parameters and performance of compressors: increase in loading of aerodynamic bladed disks, improvement of their economical efficiency, improvement of margin of the continuous flow around the compressor grids, etc. Airflow in the compressor grid is characterised by the flow region in the flow core and also by the flow regions in the wall boundary layers on the grid blades where shock waves, vortices, air swirls, and flow separation phenomena take place. The principle objective of the work is to research the possibilities of influence on the parameters of the elements of compressors and overall performance of gas-turbine engines via the methods of active and passive flow regulation. Active flow regulation is realised either by rendering the auxiliary gas mass to the blades boundary layer, or by suction (withdrawal) of the boundary layer (its part) from the surfaces of blades. Passive flow around regulation is characterised by influence on the boundary layer by means of energy redistribution in the flow itself. Santrauka Šiuo tyrimu siekiama nustatyti sparno profilio aptekejimo įtaką vienos eiles menčių kompresoriaus su lygiomis ir šiurkščiomis mentemis darbui, esant įdiegtiems sūkurio generatoriams. Pagrindinis darbo tikslas – ištirti kompresoriaus elementų ir bendro dujų turbininių variklių darbo įtaką parametrams, taikant pasyvų ir aktyvų srauto reguliavimo metodus. Padidinus dujų turbininių variklių našumą ir jų dujų dinamikos stabilumo ribas, pagereja kompresorių darbas ir parametrai: padideja aerodinaminių diskų su mentemis apkrova, jie tampa ekonomiškai našesni, padideja nepertraukiamo srauto riba aplink kompresoriaus plokšteles.
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Denkena, Berend, Jens Köhler i Thomas Krawczyk. "Grinding of Riblet Structures on Free Formed Compressor Blades". Advanced Materials Research 907 (kwiecień 2014): 463–73. http://dx.doi.org/10.4028/www.scientific.net/amr.907.463.
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The effectiveness of gas turbines can be improved significantly by decreasing the friction losses. Compared to smooth surfaces riblet-structures have been proven to reduce skin friction in turbulent flow up to 10 %. For the technical application on compressor blades in turbo machines, micro riblet-structures with a riblet width between 20 μm and 120 μm and a depth of the half width are required. Furthermore, the application on compressor blades needs ideal riblet-geometries with an aspect ratio of 0.5, trapezoid groove geometry and a shape accuracy of the compressor blade about 10 μm. This paper presents the relevant influencing factors on the overall shape accuracy as well as the riblet geometry in five axes grinding of riblet-structures on double curved compressor blades. The results show, that the shape accuracy is affected by the CAD data and the macro-geometry of the grinding wheel. Therefore, specialized requirements on the CAD data were defined in order to increase the shape accuracy. To decrease the influence of the grinding wheel geometry on the overall shape geometry, a method adjusting the grinding wheel geometry on double curved surfaces was developed. Furthermore, the effect of the 5 axes kinematic on the aspect ratio and the profile wear was examined.
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Korakianitis, T. "Prescribed-Curvature-Distribution Airfoils for the Preliminary Geometric Design of Axial-Turbomachinery Cascades". Journal of Turbomachinery 115, nr 2 (1.04.1993): 325–33. http://dx.doi.org/10.1115/1.2929238.
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Blade surfaces with continuous curvature and continuous slope of curvature minimize the possibility of flow separation, lead to improved blade designs, and reduce the direct and inverse blade-design iterations for the selection of isolated airfoils and gas-turbine-blade cascades. A method for generating two-dimensional blade shapes is presented. The geometry near the trailing edge is specified by an analytic polynomial, the main portion of the blade surface is mapped using as input a prescribed surface-curvature distribution, and the leading edge is specified as a thickness distribution added to a construction line. This procedure is similar for the suction and pressure surfaces, and by specification it constructs continuous slope-of-curvature surfaces that result in smooth surface-Mach-number and surface-pressure distributions. The method can be used to generate subsonic or supersonic airfoils for compressors and turbines, or isolated airfoils. The resulting geometric shapes can be used as inputs to various blade-design sequences. It is shown that, with other cascade-design parameters being equal, increasing the stagger angle of turbine blades results in more front-loaded and thinner blades, and that there is an optimum stagger angle resulting in minimum wake thickness. The subsonic axial-turbine blade rows included for discussion in this paper have been designed by iterative modifications of the blade geometry to obtain a desirable velocity distribution. The blade-design method can be used to improve the aerodynamic and heat transfer performance of turbine cascades, and it can result in high-performance airfoils, even if using the direct method exclusively, in very few iterations.
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Suder, K. L., R. V. Chima, A. J. Strazisar i W. B. Roberts. "The Effect of Adding Roughness and Thickness to a Transonic Axial Compressor Rotor". Journal of Turbomachinery 117, nr 4 (1.10.1995): 491–505. http://dx.doi.org/10.1115/1.2836561.
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The performance deterioration of a high-speed axial compressor rotor due to surface roughness and airfoil thickness variations is reported. A 0.025 mm (0.001 in.) thick rough coating with a surface finish of 2.54–3.18 rms μm (100–125 rms μin.) is applied to the pressure and suction surface of the rotor blades. Coating both surfaces increases the leading edge thickness by 10 percent at the hub and 20 percent at the tip. Application of this coating results in a loss in efficiency of 6 points and a 9 percent reduction in the pressure ratio across the rotor at an operating condition near the design point. To separate the effects of thickness and roughness, a smooth coating of equal thickness is also applied to the blade. The smooth coating surface finish is 0.254–0.508 rms μm (10–20 rms μin.), compared to the bare metal blade surface finish of 0.508 rms pm (20 rms μin.). The smooth coating results in approximately half of the performance deterioration found from the rough coating. Both coatings are then applied to different portions of the blade surface to determine which portions of the airfoil are most sensitive to thickness/roughness variations. Aerodynamic performance measurements are presented for a number of coating configurations at 60, 80, and 100 percent of design speed. The results indicate that thickness/roughness over the first 2 percent of blade chord accounts for virtually all of the observed performance degradation for the smooth coating, compared to about 70 percent of the observed performance degradation for the rough coating. The performance deterioration is investigated in more detail at design speed using laser anemometer measurements as well as predictions generated by a quasi-three-dimensional Navier–Stokes flow solver, which includes a surface roughness model. Measurements and analysis are performed on the baseline blade and the full-coverage smooth and rough coatings. The results indicate that adding roughness at the blade leading edge causes a thickening of the blade boundary layers. The interaction between the rotor passage shock and the thickened suction surface boundary layer then results in an increase in blockage, which reduces the diffusion level in the rear half of the blade passage, thus reducing the aerodynamic performance of the rotor.
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Gu, Yunqing, Muhan Yan, Jiayun Yu, Ke Xia, Longbiao Ma, Jiegang Mou, Denghao Wu i Jianxing Tang. "Effect of the Bionic Circular Groove Non-Smooth Structure on the Anti-Wear Performance of the Two-Vane Pump". Lubricants 10, nr 10 (22.09.2022): 231. http://dx.doi.org/10.3390/lubricants10100231.
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The characteristics of the material transported by the two-vane pump can cause the impeller to wear out, leading to a deterioration in hydraulic efficiency. Appropriately, the research goal of this paper is to consolidate the anti-wear performance of the two-vane pump conveying a solid-liquid two-phase flow. Based on the bionic principle and the anti-wear structure of blood clams, the circular non-smooth structure adapted from blood clams is arranged in the wear-prone area. Through numerical simulation, we compare the main indexes of the pump: the head, the pressure distribution, the vortex pressures, and the average wear rate, to reveal the wear resistance mechanism of circular non-smooth structures. The results illustrate that the use of a circular non-smooth structure does not modify the external characteristics of the pump; the pressure distribution inside the impeller is similarly consistent, and the vortex pressures are all approximately the same. The average wear rate is higher when the diameter of the circular non-smooth structure is either 0.25 mm or 0.30 mm, and the simulation results are poor. At a diameter of 0.20 mm, the average wear rate of circular non-smooth blades is at its lowest point. The circular non-smooth surface structure causes impurities to be “caught” by the vortex zone and not freely struck against the wall, resulting in the particles migrating away from the blade.
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Abler, William L. "The Serrated Teeth of Tyrannosaurid Dinosaurs, and Biting Structures in Other Animals". Paleobiology 18, nr 2 (marzec 1992): 161–83. http://dx.doi.org/10.1017/s0094837300013956.
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The function of serrated teeth is analyzed by experimental comparison with the action of artificially made steel blades. Serrated blades cut compliant materials with a grip-and-rip mechanism, whereas smooth, sharp blades cut by concentrating a large downward force on a tiny area.Tyrannosaurid teeth from the Cretaceous Judith River Formation bear rows of serrations that have thick, rounded enamel caps, gripping slots between neighboring serrations, thick enamel bodies inside the teeth underneath the gripping slots, and a root beneath each serration. In contrast, the carnivorous dinosaur Troodon has teeth with exposed pointed serrations, thin enamel, and possibly serration roots.Serrations on the teeth of Troodon and the fossil shark Carcharodon, cut compliant materials in the same way as a serrated hacksaw blade. In contrast, the cutting action of tyrannosaurid teeth most closely resembles that of a dull smooth blade. The spaces between the serrations act as minute frictional vises that grip and hold meat fibers; chambers between neighboring serrations receive and retain small fragments of meat, and inevitably would have acted as havens where bacteria could be stored. These spaces may therefore have led to infections in wounds, analogous to those inflicted by the living Komodo dragon or ora. By analogy, the hunting and feeding behavior of tyrannosaurs may have resembled that of the ora.Serrations and slots are widely distributed among cutting devices in the natural world, and many of these deserve further study. For example, the carnassial teeth of mammalian carnivores cut by a combination of static force at the cutting edge, a crushing or scissoring action at the advancing junction between upper and lower teeth, and by lateral gripping and compression in a slot, like that seen on a much smaller scale in tyrannosaurid serrations. Mammalian teeth operate well only when deployed with sophisticated control over jaw movement, however, and the fine neural control necessary to operate them may have formed the basis for the later development of intelligence in mammals.Previously, being interested in mammals was largely a matter of being interested in teeth, whereas being interested in reptiles was largely a matter of being interested in everything but teeth. I suggest that the teeth of at least some reptiles are as rich in information as the teeth of any mammals.
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Takeyama, Ken, Hideyuki Yokochi, Satoru Nishio i Satoru Tsuchikawa. "Characteristics of self-excited alternate-tooth vibration of circular saw blade". BioResources 16, nr 2 (13.04.2021): 3840–50. http://dx.doi.org/10.15376/biores.16.2.3840-3850.
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In recent years, circular saw blades with thinner kerfs have been in high demand for improvement of the production yield of wood-based materials and the reduction of sawdust. In the case of ripping of solid wood, the number of teeth of a circular saw blade is normally set to 40 or 50, with a diameter of 305 mm, which allows less cutting resistance and smooth exhausting of sawdust. However, at certain rotational speeds, self-excited alternate-tooth vibration can easily occur in circular saw blades with such thin kerfs and so few teeth. Therefore, the cutting surface quality tends to be worse. In this study, the mechanism of this self-excited alternate-tooth vibration was clarified. The vibration mode and frequency were predicted by the finite element method. In addition, a circular saw blade with a body thickness 1.5 mm and 50 teeth was employed for wood-cutting experiments. The rotational speed range of the self-excited alternate-tooth vibration modes and their frequencies were investigated. When a double of the tooth passage frequency was slightly higher than the frequencies of the alternate-tooth vibration modes, an alternate-tooth vibration of the regenerative chatter type was excited, owing to the forces on the sides of the tooth.
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Yan, Pei, Yiming Rong, Xibin Wang, Junyi Zhu, Li Jiao i Zhiqiang Liang. "Effect of cutting fluid on precision machined surface integrity of heat-resistant stainless steel". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, nr 9 (24.10.2016): 1535–48. http://dx.doi.org/10.1177/0954405416673684.
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The machined surface integrity of blades is of utmost importance in the power equipment manufacturing industry. Recently, many blade accidents have been attributable to the misuse of cutting fluids that were necessary in the actual machining of difficult-to-cut materials, but the effect of the cutting fluid on surface integrity and service performance has been persistently neglected. In this article, an investigation into the effect of cutting fluids on the surface quality of a typical blade material was undertaken, combined with properties of two universal cutting fluids. Element composition, surface morphology, residual stress and hardness of the machined surfaces were investigated. The results indicated that cutting fluids could not reduce cutting forces in precision machining. There were some places where local and irregular elemental Cr loss was incurred when machined with the additive Cl, and the depth of Cr loss was 1–2 µm. The machined surface under CF-206 was smooth, and the roughness of CF-210 was the highest. The tensile residual stresses of dry cutting were the highest, whereas those of CF-210 were the lowest. Surface work hardening under cutting fluids was higher, with depths of 20–30 µm. These results are significant for the control of precision machined surfaces and subsurfaces of blades with high integrity and service performance.
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Newell, Steven Y. "Fungal biomass and productivity in standing-decaying leaves of black needlerush (Juncus roemerianus)". Marine and Freshwater Research 52, nr 2 (2001): 249. http://dx.doi.org/10.1071/mf00068.
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Ascomycetous fungal decomposers generate the major part of the microbial biomass on and in standing naturally decaying shoots for one (smooth cordgrass, Spartina alterniflora ) of the two major ramet-forming marsh plants of the south-eastern USA. Evidence from frequency of occurrence of sexual structures (ascomata) in the second major ramet-forming marsh plant (black needlerush, Juncus roemerianus ) suggests that fungi are major secondary producers in the needlerush decomposition system also. To test this, samples of needlerush blades at three stages of decay were collected seasonally for three years. Average living-fungal standing crop (as ergosterol) of needlerush blades (254 µ g g – 1 organic mass of decay system) was ~65%of a comparable average for smooth cordgrass, but fungal mass was equally active between the two species (near 30 pmol acetate incorporated into ergosterol µ g – 1 ergosterol h –1 ). Although maximum living-fungal crop for needlerush was found in winter, and in winter and spring for smooth cordgrass, in many other respects, patterns of change in needlerush fungal variables were quite different from those for smooth cordgrass. For example, living-fungal standing crop rose 1.5-fold with decay stage for needlerush, but was constant for cordgrass, perhaps because of lesser mycophagous activity and lesser competition from bacterioplankton associated with tidal flooding in the high-marsh, needlerush zones.
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A. Simpson. "On the generation of a set of accurate numerical modal functions for use in the aeroelastic analysis of flexible rotor blades". Aeronautical Journal 93, nr 926 (lipiec 1989): 207–18. http://dx.doi.org/10.1017/s000192400001705x.
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A comparison is presented of three methods for the generation of numerical, modal approximating functions for use in modal Lagrangian analysis of rotating flexible blades. The methods considered are those based on the use of uniform beam/bar eigenfunctions, smooth bending moment or torque modes, and modes generated by recourse to one stage of the Stodola method. For blades which are highly non-uniform in their specific stiffness and inertial properties, and where the objective is to use a small number of approximating functions, consistent with accurate determination of eigen-solutions in the fundamental spectrum, it is demonstrated (as is well known) that direct use of uniform system eigenfunctions is unsatisfactory. On the other hand, it is demonstrated that the use of smooth bending moment modes, even in cases where the variations in sectional inertia properties are very large, can produce excellent results. The use of ‘Stodola modes', however, is shown to offer the all-important advantage of enhanced convergence rate in all cases considered.
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Bagrintsev, V. V., N. V. Marinich i А. A. Koval. "Effect of vane hub cap on hydrodynamic, cavitation and acoustic performance of propulsion system". Transactions of the Krylov State Research Centre 3, nr 401 (5.07.2022): 47–51. http://dx.doi.org/10.24937/2542-2324-2022-3-401-47-51.
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Object and purpose of research. Effects of the vane hub cap are investigated regarding hydrodynamic, cavitation and acoustic performance of a ducted propeller as propulsion system. Materials and methods. In the work process two versions of the vane hub cap have been designed to take account of the wake field behind propeller. Experimental investigations of the propulsion system model with a smooth hub cap and designed hub cap are given. Additionally, positions of hub cap vanes with respect to propeller blades (in-between the blades or in wake of the blades) were studied. Main results. The thrust and torque coefficients as well as cavitation numbers were obtained, and the acoustic radiation was measured for the investigated propulsion system arrangements. Conclusion. Comparisons were made and conclusions drawn regarding the efficiency of vane hub cap application.
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Ghorbani, Hamid, i Farbod Khameneifar. "Airfoil profile reconstruction from unorganized noisy point cloud data". Journal of Computational Design and Engineering 8, nr 2 (28.02.2021): 740–55. http://dx.doi.org/10.1093/jcde/qwab011.
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Abstract Airfoil blades are typically inspected in sections to verify their conformance to the geometric tolerances specified on their nominal design. To maintain the accuracy of geometric error evaluation, in particular, for the position and orientation errors of the airfoil sections, sectional airfoil profiles should be reconstructed from the inspection data points. This paper presents a new method to automatically reconstruct the airfoil profile from unorganized noisy sectional data points of 3D scanned blades. A three-step airfoil profile reconstruction approach is presented. First, the algorithm thins the scattered set of sectional data points by projecting them onto the local curves fitted to them. For this purpose, a recursive weighted local least-squares scheme is proposed to fit local curves within the measurement uncertainty constraint of inspection data. Then, to order the thinned set of data points, the profile polygon is generated and imperfect nodes are modified by evaluation of the angular deviation of edges. Finally, a closed nonperiodic B-spline curve is fitted to the thinned and ordered set of data points to construct the smooth airfoil profile. A series of case studies have been carried out to demonstrate the effectiveness of the proposed airfoil profile reconstruction method. Implementation results have demonstrated that the proposed method is accurate and robust to noise. In addition to blade inspection, other applications such as repair and adaptive machining of aero-engine blades can equally benefit from the proposed method for automatic airfoil profile reconstruction.
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Abdulwahab, Zaman A., Sami I. Jafar i Sami A. Ajeel. "Effect of Laser Process on Microstructure and Fatigue Resistance of Steam Turbine Blade". IOP Conference Series: Earth and Environmental Science 961, nr 1 (1.01.2022): 012017. http://dx.doi.org/10.1088/1755-1315/961/1/012017.
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Abstract The steal turbine blades, operating in steam electricity production plants are subjected to periodic circular stresses that cause fatigue failure with the passage of time. The chemical composition so steam turbine blades show that is steel 52 it has a wide range of applications, mostly in welded construction, All kinds of welded construction, wind turbines, load-lifting equipment, platform components, cranes, bridge components, and structures. This research aims to study the microstructure of these turbine blades before and after the occurrence of fatigue, and for the purpose of improvement the fatigue resistance, the blades were treated with a laser and the amount of improvement in fatigue resistance was calculated and also the change in the microstructure after laser treatment was studied. The remelting process applied with this parameter Pulse energy = 8 joules, Pulse width = 4.5 Ms., Pulse frequency = 12 Hz, Laser Average Power = 96 W, Laser peak power = 1.78 KW. The results show, after remelting process the microstructure of the specimen is smooth and increase the cyclic of fatigue comparison with specimen without leaser remelting process. So, the fatigue resistance is increased.
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Zhang, Xue Feng, Maria Vera, Howard Hodson i Neil Harvey. "Separation and Transition Control on an Aft-Loaded Ultra-High-Lift LP Turbine Blade at Low Reynolds Numbers: Low-Speed Investigation". Journal of Turbomachinery 128, nr 3 (1.02.2005): 517–27. http://dx.doi.org/10.1115/1.2187524.
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An experimental study was conducted to improve the performance of an aft-loaded ultra-high-lift low-pressure turbine blade known as U2 at low Reynolds numbers. This was achieved by manipulation of the laminar-turbulent transition process on the suction surface. The U2 profile was designed to meet the targets of reduced cost, weight and fuel burn of aircraft engines. The studies were conducted on both low-speed and high-speed experimental facilities under the unsteady flow conditions with upstream passing wakes. The current paper presents the low-speed investigation results. On the smooth suction surface, the incoming wakes are not strong enough to suppress the separation bubble due to the strong adverse pressure gradient on the suction surface and the low wake passing frequency, which allows the separation between the wakes more time to re-establish. Therefore, the profile losses of this ultra-high-lift blade are not as low as conventional or high-lift blades at low Reynolds numbers even in unsteady flows. Two different types of passive separation control devices, i.e., surface trips and air jets, were investigated to further improve the blade performance. The measurement results show that the profile losses can be further reduced to the levels similar to those of the high-lift and conventional blades due to the aft-loaded nature of this ultra-high-lift blade. Detailed surveys of the blade surface boundary layer developments showed that the loss reduction was due to the suppression of the separation underneath the wakes, the effect of the strengthened calmed region and the smaller separation bubble between wakes.
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Veerammanavara, Raghavendra, Veerangouda M, Sushilendra, Vijayakumar Palled, Sharangouda Hiregoudar i Channabasavann A.S. "Influence of Blade Types, Cutting Velocity and Stalk Diameter of Sorghum Crop on Cutting Energy and Cutting Force". Ecology, Environment and Conservation 28 (2022): 79–85. http://dx.doi.org/10.53550/eec.2022.v28i07s.013.
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Sorghum (Sorghum bicolor L.) popularly known as “Jowar”, a cereal grain found in tropical and subtropical climate. India ranks fifth in total sorghum production with 4.7 million tonnes (USDA, 2020). Sorghum is grown in India in an area about 4.82 m ha with production of 4.78 m tonnes and productivity of 989 kg/ ha.In Karnataka, it is grown in 0.94 m ha with a production of 0.98 million tonnes and productivity of 945 kg/ha (INDIASTAT, 2020). A designed and fabricated laboratory test-rig of a pendulum impact tester was used to conduct the experiment in the Department of Farm Machinery and Power Engineering, College of Agricultural Engineering, Raichur. The experiment was conducted to determine the engineering properties of sorghum stalk. The independent variables viz., two types of blades (smooth edge and serrated blade), four levels different stalk diameters (12, 16, 20, 24 mm) and three levels of blade cutting velocity (4.40, 6.30, 7.40 m/s) were selected. Results showed that the maximum cutting energy of 35.47 J was recorded at a blade cutting velocity of 4.40 ms-1 at 24 mm stalk diameter and the least cutting energy of 5.23 J was recorded for 12 mm stalk diameter at blade cutting velocity of 7.40 m s-1 for serrated blade for smooth edge blade and the more cutting energy was recorded of 28.65 J for 24 mm stalk diameter at blade cutting velocity of 4.40 ms-1 and the least cutting energy 3.55 J were recorded for 12 m stalk diameter at 7.40 ms-1 for serrated cutting blade. The maximum cutting force of 1477.92 N was recorded at a blade cutting velocity of 4.40 ms1 at 24 mm stalk diameter. The least cutting force of 435.81 N was recorded for 12 mm stalk diameter at blade cutting velocity of 7.40 m s-1 for smooth edge blade and for serrated cutting blade, the more cutting force was recorded of 1193.75 N for 24 mm stalk diameter at blade cutting velocity of 4.40 ms-1 and the least cutting energy 295.84 N were recorded for 12 m stalk diameter at 7.40 ms-1.
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Grinchar, N. G., i A. Yu Bykov. "Influence of hydro-pneumatic accumulator on the hydraulic drive of the brush work body of light type track machines". Nauchno-tekhnicheskiy vestnik Bryanskogo gosudarstvennogo universiteta 7, nr 2 (25.06.2021): 113–19. http://dx.doi.org/10.22281/2413-9920-2021-07-02-113-119.
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The main direction of improving the repair processes of all types and the current maintenance of the track is to reduce the time and labor costs with the highest possible level of mechanization and automation of all types of track work. At the same time, a significant place is occupied by cleaning the tracks from weeds and excess ballast. The working body of the machines for performing these works is a brush picker with flexible blades, which provides cleaning of weeds and ballast below the level of the rail head. As a rule, on domestic machines, flexible blades are segments of a steel cable with a diameter of 16…21 mm. One of the main disadvantages of brush pickers with cable blades is the relatively low efficiency due to fatigue breaking of the flexible blades at the point of exit from the seal. There are also known design solutions with the use of blades made of rubber tape. The most successful is the combination of cable and belt blades on one picker. The main type of drive for such a working body should be considered a volumetric hydraulic drive, which allows you to solve the problem structurally in the simplest and most effective way. Since the picker blades interact with the object (ballast rubble) alternately ( usually there are 8-12 blades) the load on the drive is non-stationary, the pressure in the pressure line of the drive hydraulic motor changes sinusoidally, which negatively affects the reliability and durability of the drive. To smooth out pressure fluctuations, it is recommended to use a hydropneumulator.
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Lee, Kyung Jung, Il Wung Park, Ki Suk Bang, Yeong Min Kim i Young Chull Ahn. "Optimal Design of a Plenum Fan with Three-Dimensional Blades". Applied Sciences 10, nr 10 (17.05.2020): 3460. http://dx.doi.org/10.3390/app10103460.
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We successfully designed an optimized plenum fan with a three-dimensional, smooth, curved blade. The optimized model revealed that the static pressure in the channel had been increased uniformly and stably, and the flow separation at the leading edge was significantly reduced. According to simulations, the three-dimensional blade stabilized the fluid flow, and the flow friction was reduced by suppressing the flow separation as much as possible so that both the static pressure and the static efficiency were clearly improved in comparison with those of the original model. As a result, the static efficiency was improved by 6.3% compared with that of the original model.
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Ninnemann, Todd, i Wing F. Ng. "Loss Reduction Using Riblets on a Supersonic Through-Flow Fan Blade Cascade". Journal of Fluids Engineering 126, nr 4 (1.07.2004): 642–49. http://dx.doi.org/10.1115/1.1667883.
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An experimental and computational study to determine the effects of riblets on the performance of the Supersonic Throughflow Fan (STF) cascade blades was performed. The cascade was tested in the Virginia Tech intermittent wind tunnel facility, where the Mach and Reynolds (based on chord) numbers were 2.36 and 4.8×106, respectively. The riblet sheets were symmetric v-grooved type and were applied onto the blade surfaces. Three different riblet heights were tested: 0.023, 0.033, and 0.051 mm. Riblet testing was conducted at design incidence as well as at off-design conditions (incidence angles: +5, −10 deg). Loss coefficients were measured and compared with a control test case where an equivalent thickness of smooth material was applied to the blade. Results show that at the design incidence, the riblet sheet with a height of 0.033 mm provides the optimal benefit, with a reduction of 8.5% in loss coefficient compared to the control case. Smaller effects were measured at the off-design conditions. In addition to the experimental study, a numerical investigation of the riblet effect on the STF cascade was conducted at design incidence. A simple method was developed to model riblet effects due to decrease in turbulent viscous drag and the delay of turbulent transition on the blades. Conclusions from numerical study indicate the 2/3 of the total decrease in losses are the result of delaying the transition location. The final 1/3 decrease in loss coefficient comes from the decrease in turbulent viscous losses.
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Zhang, Bo, Quan Hong, Yuanyuan Dou, Honghu Ji i Rui Chen. "Experimental investigation of flow and heat transfer characteristics on matrix ribbed channel". Thermal Science 24, nr 3 Part A (2020): 1593–600. http://dx.doi.org/10.2298/tsci190702026z.
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The effect of the rib width to height ratio t/e and width to pitch ratio t/p on the local heat transfer distribution in a rectangular matrix ribbed channel with two opposite in line 45? ribs are experimentally investigated for Reynolds numbers from 54000 to 150000. The rib height to channel height ratio e/H is 0.5, t/p and t/e both varies in range of 0.3-0.5. To simulate the actually situation in turbine blades, and provide useful direct results for turbine blade designers, the parameters are same with the blade. The experiments results show that, in comparison to fully developed flow in a smooth pipe of equivalent hydraulic diameter, the Nusselt number inside the matrix-ribbed rectangular channel is increased up to 5 to 9 times higher, while total pressure drop is enlarged by up to significant magnitude. The Nusselt number ratio increases with t/p and t/e increased. Semi-empirical heat transfer is developed for designing of cooling channel.
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Boyle, R. J. "Prediction of Surface Roughness and Incidence Effects on Turbine Performance". Journal of Turbomachinery 116, nr 4 (1.10.1994): 745–51. http://dx.doi.org/10.1115/1.2929468.
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The use of a Navier–Stokes analysis to predict the change in turbine efficiency resulting from changes in blade surface roughness or incidence flow angles is discussed. The results of a midspan Navier–Stokes analysis are combined with those from a quasi-three-dimensional flow analysis code to predict turbine performance. A quasi-three-dimensional flow analysis code was used to determine turbine performance over a range of incidence flow angles. This analysis was done for a number of incidence loss models. The change in loss due to changes in incidence flow computed from the Navier–Stokes analysis is compared with the results obtained using the empirical loss models. The Navier–Stokes analysis was also used to determine the effects of surface roughness using a mixing length turbulence model, which incorporated the roughness height. The validity of the approach used was verified by comparisons with experimental data for a turbine with both smooth and rough blades tested over a wide range of blade incidence flow angles.
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Wang, Rui, Yuhao Ge i Xiangyu Guo. "Investigation on Tool Path Planning Algorithm of Propeller Blade Double-Sided Collaborative Machining". Applied Sciences 13, nr 11 (27.05.2023): 6529. http://dx.doi.org/10.3390/app13116529.
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The concomitant vibration and deformation produced by propeller blades in single-sided machining seriously affect the surface machining precision. Double-sided symmetrical machining can improve system rigidity through mutual shoring on both sides which abates the concomitant vibration and deformation. However, the actual double-sided symmetrical machining cannot be applied to blade machining due to its shape complexity. The double-sided collaborative machining method combining symmetrical machining and staggered machining is devised in this paper, and its tool path planning algorithm is investigated. Firstly, the algorithm achieves smooth fitting and correspondence of bilateral cutter position points through double-curve interpolation and position data alignment. Secondly, the blade surface is divided into four regions by two partition parameters: tip region, internal region, variable region, and edge region. Then, the conversion between symmetrical machining and staggered machining is completed through the Sigmoid deformation curve in the variable region. Finally, the feasibility and superiority of double-sided collaborative machining are verified through machining experiments.
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Ren, Luquan, Zhiwu Han, Jianjiao Li i Jin Tong. "Effects of non-smooth characteristics on bionic bulldozer blades in resistance reduction against soil". Journal of Terramechanics 39, nr 4 (październik 2002): 221–30. http://dx.doi.org/10.1016/s0022-4898(03)00012-0.
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Munaweera Thanthirige, Tenis Ranjan, Jamie Goggins, Michael Flanagan i William Finnegan. "A State-of-the-Art Review of Structural Testing of Tidal Turbine Blades". Energies 16, nr 10 (12.05.2023): 4061. http://dx.doi.org/10.3390/en16104061.
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Over the last two decades, the tidal energy industry has laid the groundwork for creating commercially viable tidal power generation projects to strengthen sustainable energy policies around the world. At the end of 2021, the cumulative installation of tidal stream technology that has been deployed in Europe reached 30.2 MW, where the majority of the installations are by small and medium-sized companies. Due to a growing demand among investors related to the global tidal energy industry, the reliability and safety of operational-stage tidal energy systems’ components are becoming increasingly important. In this context, companies, universities and research institutes are focusing on conducting large- and small-scale tests of tidal turbine elements to validate their projected design life, and major attention is being given to assessing the structural integrity of turbine blades. This review paper focuses on structural tests that have been reported for axial flow tidal turbine blades manufactured using composite materials around the world, highlighting the testing standards, equipment and instrumentation required. Overall, this review article discusses the state of the art in the structural testing of tidal turbine blades. In addition, it highlights the global concerns and research gaps to ensure the long-term sustainability of axial flow tidal turbine blades. In addition, the information contained in this article will be useful for formulating a smooth and reliable mechanism to enhance the evaluation process of the structural properties of tidal turbine blades in the future.
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Sobral, Marcos, CLÁUDIA P. CALIARI, ELIANA GRESSLER, FIORELLA F. MAZINE, MARA MAGENTA i PEDRO L. VIANA. "Seven new southeastern Brazilian species of Myrcia (Myrtaceae)". Phytotaxa 247, nr 1 (17.02.2016): 27. http://dx.doi.org/10.11646/phytotaxa.247.1.2.
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There are described, illustrated, compared with related species and commented in their conservation issues Myrcia delicata, M. exapata, M. guarujana, M. parca, M. pseudosplendens, M. ubatubana and M. venosissima. Myrcia delicata, from the states of São Paulo and Rio de Janeiro, is close to M. neocambessedeana, differing through its triflorous, slender inflorescences; Myrcia exapata, from Rio de Janeiro, is related to M. calycampa, differing through its obovate blades, longer peduncles and dichasial branches; Myrcia guarujana, from São Paulo, is related to M. colpodes, but differs in its pilose flowers and trilocular ovaries; Myrcia parca, from the state of Espírito Santo, is related to M. warmingiana, but differs in its narrower, concolorous blades, pauciflorous inflorescences and smooth ovaries; Myrcia pseudosplendens, from Minas Gerais, is close to M. splendens, but has costate fruits and exfoliating bark; Myrcia ubatubana, from São Paulo, is related to M. ferruginosa, but is kept apart through its pauciflorous inflorescences and narrower blades, and Myrcia venosissima, from Minas Gerais, resembles M. almasensis, differing through its uniflorous to triflorous inflorescences and flowers with longer calyx lobes.
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Wu, Ao, Ruijie Zhao, Fei Wang, Desheng Zhang i Xikun Wang. "Effects of Coolant and Working Temperature on the Cavitation in an Aeronautic Cooling Pump with High Rotation Speed". Machines 10, nr 10 (7.10.2022): 904. http://dx.doi.org/10.3390/machines10100904.
Pełny tekst źródłaStreszczenie:
The centrifugal pump with high rotation speed is the key component in the cooling system of an aircraft. Because of the high rotation speed, the impeller inlet is very prone to cavitation. Two impellers with different types of blades (cylindrical and splitter) are designed, and the numerical models of the pumps are built. The authenticity of the numerical models is validated with the corresponding experiments in terms of both the hydraulic and cavitation characteristics. Then, the effects of different coolants and working temperatures on the hydraulic and cavitation performances of the prototype models are studied based on the numerical simulations. The results show that the head and efficiency of the pump for conveying water are higher than those for conveying ethylene glycol (EG) aqueous solution and propylene glycol (PG) aqueous solution (EGaq and PGaq are defined to represent the EG aqueous solution and the PG aqueous solution, respectively). The hydraulic performance in the EGaq is slightly better than that in the PGaq. The cavitation performance of water is far less than that of the EGaq and PGaq under high working temperature. The volume of cavitation in EGaq is smaller than that in PGaq, and the volume of cavitation in the splitter blades is slightly smaller than that in the cylindrical blades. It is suggested that EGaq be used as the first option. The splitter blades can improve the cavitation performance somehow while the improvement by using the splitter blades is very limited at high rotation speeds, and the design of the short blades should be careful in order to obtain a smooth internal flow field.