Ring-rolling design of yaw ring for wind turbines (original) (raw)
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Ring rotational speed trend analysis by FEM approach in a Ring Rolling process
AIP Conference Proceedings, 2018
Ring Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. In this process two different deformations occur in order to reduce the width and the height of a preform hollow ring; as results a diameter expansion is obtained. In order to guarantee a uniform deformation, the preform is forced toward the Driver Roll whose aim is to transmit the rotation to the ring. The ring rotational speed selection is fundamental because the higher is the speed the higher will be the axial symmetry of the deformation process. However, it is important to underline that the rotational speed will affect not only the final ring geometry but also the loads and energy needed to produce it. Despite this importance in industrial environment, usually, a constant value for the Driver Roll angular velocity is set so to result in a decreasing trend law for the ring rotational speed. The main risk due to this approach is not fulfilling the axial symmetric constrain (due to the diameter expansion) and to generate a high localized ring section deformation. In order to improve the knowledge about this topic in the present paper three different ring rotational speed trends (constant, linearly increasing and linearly decreasing) were investigated by FEM approach. Results were compared in terms of geometrical and dimensional analysis, loads and energies required.
STRUCTURAL ANALYSIS OF SLEWING BEARINGS FOR WIND TURBINES
IAEME PUBLICATION, 2020
This study is a structural analysis of slewing bearings for wind turbines. The ball of a bearing delivers load while making contact with raceways of the inner and outer rings. To facilitate stress analysis of the slewing bearing, which has more balls than other types of bearing, the balls were converted into spring elements. Considering the shape of contact between balls and raceways, one, two, and three spring elements were introduced. Global finite element analysis of the bearing, with balls as spring elements, showed that the bearing experienced different degrees of deformation depending on the number of springs. Using the bearing deformation obtained from the global analysis, cut boundary constraint was applied for local contact analysis of balls and raceways. The contact stress between balls and raceways showed that more uniform stress could be achieved by increasing the number of springs.
Fabrication Methodology of Small Scale Horizontal Axis Wind Turbine
Due to the increasing environmental and economic cost of fossil fuels, alternative sources of energy are needed. One such source is wind energy. Much of the current wind turbine research focuses on large-scale wind turbines. An alternative approach is small-scale wind turbines designed specifically to produce power at low wind speeds. The mechanism is that the wind drives the blades, which in turn drive the compound gear train, which eventually is coupled to a generator. The DC power from the generator can either be used directly or converted to AC power and then used or stored in a battery for future use. While these results provide valuable information for the design of small-scale wind turbines, further study into the design process would result in an improved performance using CFD techniques as well as experimentation. This paper includes design and analysis of a light weight and small size turbine without compromising its performance.
Computational Investigation of a Wind Turbine Shrouded with a Circular Ring
CFD Letters
In this research work, a new design concept for shrouded turbines is introduced using a circular flange ring instead of a diffuser. The performance of a wind turbine shrouded with the conventional configuration of flanged diffusers is firstly investigated. This allows comparison to be made with the performance of the new design proposed in this project. The bare turbine used in this research work is a horizontal axis wind turbine with a diameter of 0.6 m, and the flange height is 10% of the diameter. The performance of the shrouded turbine is investigated using computational fluid dynamics; by solving the flow field using three-dimensional Reynolds Averaged Navier-Stokes for incompressible flow. Findings indicate that the performance of the turbine shrouded with the flange ring is superior to the bare turbine by 33%. It also has benefit over the conventional design as this new design concept is simpler and uses lesser material since it is not using the diffuser, which favorably in t...
Forschung im Ingenieurwesen, 2021
With the possibility to replace sliding segments on the tower without disassembling the drivetrain, the use of segmented plain bearings with conical sliding surfaces as main bearing in wind turbines has a great potential to reduce the maintenance costs and thus the levelized cost of energy (LCOE). Furthermore, the short axial design leads to lower investment costs. Since this design is totally new and no design guidelines are available so far, the objective of this paper is to investigate the influence of the geometric parameters on the hydrodynamic pressure distribution of the bearing. In this context a parameter screening is performed using a suitable test field according to Plackett and Burman in order to determine the most relevant parameters. With the help of the simulations carried out after this test field, correlations between the geometric parameters and the hydrodynamic pressure distribution are evaluated. To be able to quantitatively analyze the three-dimensional pressure...
2015
To realize large wind power plants in an economically feasible way, it is necessary to identify potential for lightweight design of the generator hollow-shafts, which are commonly produced by casting. The weight of these shafts can significantly be reduced by producing them by open-die forging, since the forming of the material leads to a higher strength, which allows to reduce the wall thickness noticeable. This paper describes the development and implementation of a forging process for hollow shafts with respect to an optimized microstructure. To numerically investigate this process, a realistic finite element simulation model was developed in a first step. The kinematic of the tools has been implemented authentically to provide a realistic material flow and process conditions. Additionally, a material model for the steel 42CrMo4 was integrated into the simulation model to predict the resulting microstructure. Using the implemented FE model, the forging process was optimized manua...
International Journal of Mechanical Sciences, 2015
This papers aims to give an answer to the problem of setup for a cylindrical ring rolling process, giving the possibility to determine stable kinematic conditions for the key variables of the process (such as mandrel feeding speed, main roll rotational speed, etc.) and also to estimate the dimension of the initial blank used to obtain the desired final ring, minimising scrap material. The setup of a manufacturing process is usually a tedious and time-consuming activity, which is largely based on the experience of the process planner. Every process presents a typical process parameters window where the set up can be arranged by the planner according to the limits due to the available machine (working volume, geometry of the tools, maximum loads, etc.) as well as to the properties of the manufactured component (material, structure, forming temperature, rheology, etc.). The general target for the planner is to produce the component, which satisfies the specifications of the designer, with the shortest time cycle and with the available machines and tools. The process planner tries to perform this commitment adopting a trial and error procedure, where he modifies the process parameters and initial blank geometry in order to find a feasible setup of the process. If this approach is directly applied in the production plant, it results to be extremely expensive, time consuming and can generate a large quantity of scrap parts. The adoption of a numerical approach based on FE simulation can be helpful because it removes the trial and error experimentation from the real production plant to its virtualization inside a CAE environment. In the case of ring rolling process the virtualization of the process is not so straightforward due to intrinsic complexity of the kinematics of the rolling mill where different tools should be moved with different laws and the plastic deformation of the ring occurs in a really 3D volume, which cannot be reduced to a simplified model as axial symmetric, plane strain or plane stress. For these reasons, the FE model is complex in terms of kinematics of the tools and discretisation of the ring volume (mesh). Moreover, this numerical problem pertains to the high not linear problems where coupled thermomechanical analysis is required. In this case, the computational effort increases considerably and results in a computational time of few days in a 4-cores computer for one simulation. Collecting rules suggested by the literature and by the practice, introducing some improvements in the model of the ring rolling process and organising them in a worksheet it is possible to provide to the process planner an analytical-numerical tool where he can check rapidly different setups of the process in terms of kinematics of the rolling mill, evolution of the ring geometry, required forces, etc. The present paper focused on the first two targets remarked just above. The choice of a constant mandrel feeding speed, as suggested in the literature, aiming to satisfy both initial and final ring dimensions, is too strict and in some practical cases cannot be accomplished. Hence, the authors suggest choosing a linear variable motion law for the feeding mandrel speed between the initial and the final condition in order to satisfy all the requirements necessary for the stability of the process. In addition to that, an analytical method is proposed in order to forecast the evolution of the kinematic key parameters during the ring rolling, including the forecast of the number of rounds necessary for the complete forming of the ring. The analytical procedure has been tested through FE simulations which have confirmed the estimations of the theoretical model, showing that the theoretical frame is suitable for the design of a rolling process for small, medium and large rings. The purpose is to give a full set of equations for setting up and controlling the ring-rolling process and to foresee the evolution of the main geometrical variables of the ring during its expansion. The Contents lists available at ScienceDirect
Cage Loads of Wind Turbine Blade Bearing
Journal of Physics: Conference Series, 2020
Slewing bearings of wind turbine blades pitch system allow the required oscillation while transferring complex dynamical loads from the rotor blades towards the hub. Most common for this application are double rowed four-point contact ball bearings consisting of two rings and two rolling element sets either equipped with a ring cage or with spacers. By equally distributing the rolling elements along the circumference, the bearing cage balances the loads along the raceways and thereby actively prevents damage mechanisms. However, cage stress analyses imply further optimization potentials leading to higher load capacities and the prediction of cage damaging mechanisms via dynamic simulations. This contribution presents a simulation procedure that calculates rolling element dynamics at the presence of a ring cage by taking the perpendicular movement of the contact ellipses due to the elastic deformations of the bearing rings into account. The procedure is carried out exemplary by the l...
DESIGN AND MATERIAL OPTIMIZATION OF WIND TURBINE BLADE
Wind is just moving air. This mass, having a certain velocity, owns kinetic energy.The energy can be converted, through a specific device, into a more useful type.Therefore, it is possible to produce electricity, moving parts with mechanical energy,pump water or provide heat for instance. Humans had the first approach with wind power thousands of years ago, propellingtheir sailboats with it. Since the 7th century AD, wind was used by windmills to pumpwater or mill grains in Persia. Wind energy has been adopted for pumping water from wells for steam trains, and itis still able to provide it for isolated houses or off-grid locations.Only at the end of 19th century the concept of modern wind turbine arises, convertingthe kinetic energy of the wind into electricity. Wind energy industry born officially in 1979, with the first serial production ofDanish turbines.