Academic literature on the topic 'Helical rotor'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Helical rotor.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Helical rotor"
1
Chen, Guang Zhong, Bing Zhang, Yue Yang, Jin Han, and Lin Jun Tong. "3D Visualization Automatic Modeling of Helical Rotors." Applied Mechanics and Materials 321-324 (June 2013): 1721–24. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.1721.
Full textAbstract:
Structure of Helical rotor is complicated.3D visualization automatic modeling of Helical Rotors with CAD could make the design of product more efficient. Scheme of 3D visualization automatic modeling of Helical Rotors is described in detail and Generation Principle of end surface curve of rotor and Scanning helix is analyzed deeply in the paper. With the further development of SolidWorks by Visual C#, 3D Visualization Automatic Modeling of Helical Rotors is accomplished .
2
Stošić, N. "On gearing of helical screw compressor rotors." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 212, no. 7 (1998): 587–94. http://dx.doi.org/10.1243/0954406981521556.
Full textAbstract:
Twin-screw compressor rotors are effectively helical gears. When these are formed from a hobbing cutter, the hobbing tool and the rotor together constitute a pair of crossed helical gears. In the present paper, the envelope gearing method is used to derive a meshing condition for crossed helical gears which is then used to create the profile of a hobbing tool. A reverse transformation enables the rotor profile thereby manufactured to be calculated. Simplification of the main gearing condition leads to the meshing expression for helical gears which may be used for the design of screw compressor rotors.
3
Chen, Feng, Liang Yao Gu, Yue Yang, and Chun Yang Jia. "Design and Realization of Helical Rotor NC Automatic Programming System." Advanced Materials Research 605-607 (December 2012): 1469–73. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.1469.
Full textAbstract:
Helical rotor is a core component of helical-lobe compressor. Analysis was made on the geometrical properties of tooth curves. Using standard spherical milling cutter on 4-axis NC machine, normal migration method was used to rotor surface processing. Based on the generation characteristics of helical rotor surface, object-oriented design method is used to achieve automatic programming system of helical rotor. The calculation of helical rotor end face profile lines and cutter location point are realized, and over cutting analysis is carried out to generate high efficient numerical control processing program.
4
Gupta, Rajat, Bachu Deb, and R. D. Misra. "Performance Analysis of a Helical Savonius Rotor with Shaft at 45° Twist Angle Using CFD." Mechanical Engineering Research 3, no. 1 (2013): 118. http://dx.doi.org/10.5539/mer.v3n1p118.
Full textAbstract:
Helical Savonius rotor is considered to be superior to conventional Savonius rotor in terms of higher power coefficient (Cp) and better starting characteristic. However studies related to helical Savonius rotors is few. In view of this, in this paper, the performance of a helical Savonius rotor with shaft at 45° bucket twist angle for one complete cycle of rotation was analyzed using Computational Fluid Dynamics. A two-bucket helical Savonius rotor with shaft was designed using GAMBIT, having a height of 60 cm and diameter of 17 cm with 45° bucket twist angle. A three dimensional Computational Fluid Dynamics analysis using Fluent package was done to predict the performance of the rotor. Standard k-? turbulence model with second order upwind discretization scheme and standard wall condition was used. Grid independence test was also conducted to have the best meshing accuracy. Power coefficients (Cp) of the rotor at different tip speed ratios were evaluated for rotor angle variation from 0° to 180°. Cp at each rotor angle increased with increase of tip speed ratio up to an optimum tip speed ratio, but then decreased even if tip speed ratio was further increased. Moreover, the effect of rotor angle on Cp in a complete cycle of rotation was analyzed. Cp was found to be positive at all rotor angles, and higher values of Cp were obtained at rotor angles namely 45°, 90°, 225° and 270°, which would contribute maximum power production by the rotor. In addition to these, flow physics of the rotor was studied using tangential velocity plots w.r.t. rotor angle and path lines across the rotor. It was found that at 45°, 90° and 135° rotor angles, maximum concentration of the path lines near the tip of the blades in the upstream and downstream side of the rotor had occurred, which would be responsible for generation of maximum power coefficient in its clockwise rotation.
5
Popa, Camelia, Virgil Gabriel Teodor, Nicuşor Baroiu, and Nicolae Oancea. "Side Mill Tool Profiling for Generation of Helical Surfaces Determined by Reverse Engineering." Applied Mechanics and Materials 657 (October 2014): 28–32. http://dx.doi.org/10.4028/www.scientific.net/amm.657.28.
Full textAbstract:
The compressor rotors usually are helical surfaces with constant pitch and are composed crossing profiles. Frequently, for repair operations occurs the reconstruction necessity for one or both of the worms, drive and driven, from the helical compressors gear. The helical composed surface of rotor flank is generated usually with side mill. The knowledge of worm shape can not be made from geometrical conditions. In these conditions it is necessary to determine the flank form by actual measuring the crossing profiles of these parts. So, the theoretical helical surface of the worm is being substituted by an assembly of helical lines which together with crossing profiles forms points cloud resulted from measuring leads to a polyhedral expression of the flank rotor. Numerically, this surface type is expressed by a coordinate array which shows its discrete image. The profiling of cutting tool bounded by a revolution surface reciprocally enveloping with the substitutive surface of the helical one represents a special problem. In this paper is proposed an algorithm for polyhedral expression of the helical surface previously determined by reverse engineering methods and an algorithm for the determination of the specific enveloping condition at contact with a discrete surface.It is presented an example for a compressor rotor measured on a 3D measuring machine, the algorithm for the transformation of the gathered points cloud in a surface with polyhedral expression. Given these conditions there were determined the enveloping condition and the axial section of the side mill.
6
Stefan, Vasilica, Ladislau David, Radu Ciuperca, Ana Zaica, Ancuta Nedelcu, and Albert Suvac. "Experimental testing of a helical rotor for compost distribution." E3S Web of Conferences 180 (2020): 03027. http://dx.doi.org/10.1051/e3sconf/202018003027.
Full textAbstract:
It is well known that a manure spreader must be able to apply manure consistently, effectively and uniformly over the time. An overapplying doze will cause serios environmental problems (pollution) and a sub-applying doze will not contribute to plants growth and the applying of the fertilizer will be a loss. Corroborate with others problems such as maintaining a constant tractor speed, a constant rotational speed of the rotor, a constant and continuous flow of the material make the manure spreading machines an important subject for study and continuously improving . The propose of this study is to test a vertical helicoidal rotor for manure spreading in order to improve the machine distribution uniformity. The relation between the rotor position and rotation sense is a definitory issue for the machine performance. In order to achieve a high distribution uniformity a single helical rotor is tested and a series of possible situations of placing four rotors on the machine are analyzed. The optimal solution is given by two indicators: uniformity of spreading and distribution width. The test were made with an helical rotor having the following characteristics: high=1,1 m, maximum diameter of helical spiral=0.345 m, minimum diameter of the helical spiral= 0.114m, helical pitch=0.3m, inclination angle = 15°. After analyzing four possible situations it is observe that the combination of the maximum uniformity with minimum distribution with is the optimal solution. Experimental were carried out with compost and can be repeatable with others type of solid organic fertilizers, but a new calibration should be done. It is desirable that a trapezoidal, oval or triangle pattern with uniform sloping sides to be achieved. Because most of the spreaders actually produce an oval or triangle distribution pattern it is necessary subsequent passes that increase the time for fertilization operation.
7
Adams, G. P., and W. Soedel. "Computation of Compression Loads in Twin Screw Compressors." Journal of Mechanical Design 117, no. 4 (1995): 512–19. http://dx.doi.org/10.1115/1.2826712.
Full textAbstract:
The compression mechanism in a twin screw compressor consists of two helical rotors. In this work, a method is presented for computing the forces and moments induced on each rotor due to gas compression. These are defined as the compression loads. The helical rotor surfaces are defined by the end profiles, wrap angle and rotor length. The 3D surface of each rotor is mapped to 2D integration regions. These regions correspond to the surfaces associated with individual compression chambers. The compression loads are computed by integrating the chamber pressure over the rotor surfaces. The integrals are evaluated at incremental values of the rotor angular position. The method is presented and implemented for a specific compressor configuration. The compression loads are resolved to forces at the bearing locations. These bearing forces are presented for operating pressures which represent an under-pressure condition. A frequency analysis demonstrates the rich frequency content of the bearing forces due to the sharpness of the compression loads as a function of the rotor angular position. In addition, it is demonstrated that the moment load about the axis of rotation induced on the female is approximately 12 percent of that induced on the male. Therefore, the female rotor motion approaches that of an idler gear.
8
Ilie, K., and A. Subic. "Parametric modelling of helical rotors for efficient design of twin-screw superchargers." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, no. 2 (2007): 267–72. http://dx.doi.org/10.1243/0954406jmes421ft.
Full textAbstract:
The parametric three-dimensional geometric model of twin-screw supercharger rotors of any aspect ratio was developed. For model validation through visualization, computer-aided design (CAD) rotor models with scalable data were generated in commercial CAD software and calibrated experimentally by laser Doppler velocimetry (LDV) tests. Calibrated rotor profile data can be transferred into CAD-CFD interface for flow simulation for performance optimization.
9
Chen, Ying-Chung, Tsung-Hsien Yang, and Siu-Tong Choi. "Dynamic analysis of a double-helical geared rotor system with oil-film bearing." Aircraft Engineering and Aerospace Technology 92, no. 4 (2020): 653–62. http://dx.doi.org/10.1108/aeat-05-2019-0094.
Full textAbstract:
Purpose This paper aims to study a dynamic analysis of a double-helical geared rotor system with oil-film bearing. Design/methodology/approach A finite element model of a double-helical geared rotor system with oil-film bearing is developed, in which a rigid mass is used to represent the gear and the Timoshenko beam finite element represents the shaft; the equations of motion are obtained by applying Lagrange’s equation. Natural frequencies, Campbell diagram, lateral responses, axial responses, bearing stiffness coefficients, bearing damping coefficients and bearing force are investigated. Findings Natural frequencies and Campbell diagram of a double-helical geared rotor system with oil-film bearing are investigated. An increased helical angle enhanced the axial response of the system and reduced its lateral response. The distance between the node and bearing affected the lateral response magnitude on the node. The farther away the gear pair was from the central part of the shaft, the higher the system’s resonance frequency became. The different gear pair position has a significant influence on the bearing stiffness coefficient and bearing force, but it just has a little effect on the bearing damping coefficient. Practical implications The model of a double-helical geared rotor system with oil-film bearing is established in this paper. The dynamic characteristics of a double-helical geared rotor system with oil-film bearing are investigated. The numerical results of this study can be used as a reference for subsequent personnel research. Originality/value Although the dynamics characteristics of geared rotor bearing system have been reported in some literature, the dynamic analysis of a double-helical geared rotor-bearing system is still rarely investigated. This paper showed some novel results that lateral and axial response results are obtained by the different helical angle and different gear positions. In the future, it makes valuable contributions for further development of dynamic analysis of a double-helical geared rotor-bearing system.
10
Chen, Guang Zhong, Bing Zhang, Yue Yang, Jin Han, and Lin Jun Tong. "Optimization of Helical Rotors in 3D Modeling Design and Processing." Applied Mechanics and Materials 321-324 (June 2013): 1775–78. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.1775.
Full textAbstract:
3D modeling process and shaped conductor of head face of helical rotor is described, and the constructing method of critical curves of head face is explained in detail. The processing principle of helical rotor is discoursed in paper and the four-axis tool path of the helical rotor based on ball cutter is deduced in UG environment. The Dynamic Process Simulation of tool path is finished, which Verify the feasibility of tool paths
Dissertations / Theses on the topic "Helical rotor"
1
Achilli, Isabella. "Study of a conventional Savonius rotor and optimization of a helical prototype." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15339/.
Full textAbstract:
The aim of this Master Thesis is to study numerically the aerodynamic performance of two small examples of horizontal axis domestic wind turbines: a conventional Savonius rotor, designed and built by a group of students of the Polytech of Tours (France), and its optimization, a helical Savonius rotor. In the first research project, the exploration is conducted even experimentally, testing the turbine in a wind tunnel present in the Polytech.
The numerical investigation is carried out by the use of a software based on Computational Fluid Dynamics named Star CCM+, which helps studying the main fluid dynamics aspects as flow velocity, pressure and coefficients of performance.
The second project consists in a helical Savonius rotor: according to the literature, the helical shape, comparing with the conventional Savonius rotor, usually shows better performances. After the 3D design on Catia, the turbine was printed using the 3D printer, on a reduced scale. CFD simulations allow to study the fluid dynamic features.
Afterwards, thanks to a comparison between the two Savonius models, the performance enhancement of the new one is shown, together with a practical understanding gained of the parameters influencing aerodynamics the most.
By means of the simulations, the helical rotor presents a power coefficient of 10%, which is better than the one of the conventional rotor, found at 7% for the same Tip Speed Ratio. Consequently, even the power produced by the new turbine, resulted to be better than the conventional windmill.
2
You, Cheng Xiang. "A theoretical study of rotor forces and torques in helical twin screw compressors." Thesis, University of Strathclyde, 1994. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21251.
Full textAbstract:
Helical twin screw compressors are being increasingly used in the oil and gas process industry and for refrigeration and air conditioning duties. This machine is capable of high reliability. To achieve it both thermodynamic efficiency and rotor forces must be taken into consideration at the design stage. In this study, a computer program for analysing the forces in a twin screw compressor has been developed. It takes into account all significant factors and includes a rotor profile generation program and a geometrical characteristics calculation program. The programs developed have been integrated with an existing performance simulation program and used to investigate several design aspects of a refrigeration twin screw compressor and an unusual refrigeration system design. A comprehensive examination of lobe tip designs suggests that lobe tip design parameters must be optimised if minimum power consumption is to be achieved and the use of a sealing strip gives an advantage. A para meter study for optimum rotor geometrical parameter combinations has shown that the 4+5 and 5+6 combinations have in general high efficiencies, but less rigidity, while the 5+7 and 4+6 combinations give the opposite results. The highest wrap angle and length/diameter ratio do not always lead to the highest compressor performance. A comprehensive examination of the influence of the slide valve on compressor performance and bearing forces has been conducted. Procedures for determining the optimum slide stop and volume ratios are presented. The detrimental effect of the non-return valve in a refrigeration system driven by a twin screw compressor has been examined. A non-reversing clutch fitted to the prime mover is an alternative, but must be designed according to the shut down torque which is higher than the normal running torque. This is demonstrated. An analytical model for axial-torsional coupled vibration in an Oil-injected twin screw compressor has been created. A frequency analysis of all the excitations has been conducted by using an FFT technique. It is found that the fundamental harmonic dominates the gas torque, while the first two harmonics dominate the axial forces.
3
Bolnot, Hadrien. "Instabilités des tourbillons hélicoïdaux : application au sillage des rotors." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4825/document.
Full textAbstract:
Ce travail de thèse porte sur les propriétés de stabilité des tourbillons hélicoïdaux, structures que l'on retrouve notamment dans le sillage des rotors d'hélicoptères et d'éoliennes.Dans une première partie, le développement spatio-temporel de l'instabilité d'appariement est caractérisé à l'aide d'un code numérique pseudo-spectral pour une allée infinie d'anneaux tourbillonnaires. On montre que ce modèle axisymétrique d'écoulement est en effet une bonne approximation du système hélicoïdal dans la limite des grands rayons et petits pas d’hélice. Dans ces conditions, et en utilisant un adimensionnement judicieux, on obtient également que le résultat théorique pour le taux de croissance spatio-temporel obtenu pour une double allée de tourbillons ponctuels s’avère être une bonne prédiction pour le cas hélicoïdal.Dans une seconde partie, on décrit comment un ou plusieurs tourbillons hélicoïdaux ont pu être générés de façon très peu perturbée à l’aide de modèles réduits de rotors dans le canal hydrodynamique du laboratoire. Grâce à l’introduction de perturbations d’amplitudes et de fréquences soigneusement contrôlées, le taux de croissance de l’instabilité d’appariement a pu être mesuré et comparé aux résultats théoriques. L’évolution non linéaire de ces perturbations ainsi que d’autres modes instables, à plus petites longueurs d’onde, ont également pu être observés expérimentalement pour la première fois.Enfin, ces résultats ont été appliqués au cas des rotors d’hélicoptères pour la prédiction du régime de Vortex Ring State (VRS) et à la transition vers la turbulence du sillage des éoliennes<br>This thesis is devoted to the stability properties of helical vortices, which are of interest for applications such as helicopter and wind turbine wakes.In a first part, the spatio-temporal development of the pairing instability is characterised for an infinite array of vortex rings, using a pseudo-spectral numerical code. We show that this axisymmetric flow model is indeed a good approximation of the helical system in the limit of large helix radius and small pitch. Under these assumptions, and by using appropriate dimensionless variables, we also show that the theoretical result concerning the spatio-temporal growth rate for a double row of point vortices represents a good prediction for the helical case.In a second part, we describe how one or several helical vortices were generated in a carefully controlled way using small-scale rotor models in the water channel of the laboratory. Introducing perturbations with well-defined amplitudes and frequencies, the growth rate of the pairing instability could be measured experimentally and compared to theoretical predictions. The non-linear evolution of these perturbations, as well as other unstable modes of smaller wavelengths, were also observed experimentally for the first time.Finally, these results were applied to helicopter wakes for the prediction of the Vortex Ring State (VRS) regime and to the transition to turbulence in wind turbine wakes
4
Oliveira, Cássia Pederiva de. "Análise do desempenho de uma turbina savonius helicoidal com torção de 180º empregando simulação numérica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/108528.
Full textAbstract:
Este trabalho apresenta a simulação numérica do escoamento turbulento em torno de uma turbina eólica de eixo vertical de pequeno porte, Savonius tipo helicoidal com torção de 180° nas pás. Com o intuito de avaliar a metodologia computacional empregada os resultados numéricos obtidos são comparados com os resultados experimental e numérico contidos no estado da arte. Também, compara-se o coeficiente de toque da turbina Savonius helicoidal com a turbina Savonius convencional. As simulações numéricas são baseadas no Método de Volumes Finitos, e para tal emprega-se o programa Fluent /Ansys versão 13.0 que resolve as equações da continuidade e as equações de Navier-Stokes com médias de Reynolds, juntamente com o modelo de turbulência . As simulações são desenvolvidas empregando diferentes malhas computacionais em estudos transientes, tridimensionais, com a turbina estacionária. A avaliação da qualidade da malha é realizada através do método de Índice de Convergência de Malha (GCI) o qual analisa o quão longe os resultados estão da solução assintótica para a malha utilizada. Após a análise da qualidade de malha, realizam-se simulações com a turbina em rotação as quais fazem uso da malha contendo uma região móvel possibilitando a imposição de uma velocidade angular ao rotor. O coeficiente de torque é obtido nas simulações e a partir dele calcula-se o coeficiente de potência. Além da análise do desempenho do rotor realiza-se uma análise qualitativa das características do escoamento sobre a turbina. A turbina Savonius helicoidal apresenta um valor de coeficiente de potência de 0,175 para a razão de velocidade de ponta de 0,58 considerando correção do efeito de bloqueio. Os resultados obtidos apresentam boa concordância com os resultados publicados por outros autores.<br>This dissertation presents the numerical simulation of the turbulent flow around of a small sized vertical axis wind turbine, consisting in a helical Savonius type with a 180° degree of blade twist. In order to evaluate the used methodology the obtained results are compared with the state of the art numerical and experimental data. It will be also presented the comparison between the torque coefficient of the conventional Savonius turbine and the helical Savonius turbine. The numerical simulations are based on the Finite Volume Method (FVM), using the commercial code Fluent/ANSYS version 13.0, which solves the continuity and Navier-Stokes through the Reynolds time-averaged methodology, including the turbulence model. The simulations are developed using different computational meshes for transient and three-dimensional studies with the stationary turbine. The evaluating the quality of the mesh is performed by of Grid Convergence Index (GCI) method which analyzes how far the results are the asymptotic solution to the mesh used. After the evaluation of the mesh quality, it was simulated a case considering the rotor motion using the moving mesh configuration, allowing the imposition of an angular velocity to the turbine. In the post-processing stage, it is possible to obtain the torque coefficient on the rotor shaft, allowing the calculation of the power coefficient for the turbine. In addition to the performance analysis, it is also made a qualitative analysis of the flow characteristics over the turbine rotor and in both cases presenting a good correspondence with the results in the literature. The helical Savonius turbine presents a value of power coefficient of 0.175 to a tip speed ratio of 0.58 whereas blocking effect correction.
5
Ali, Mohamed. "Caractérisation et instabilités des tourbillons hélicoïdaux dans les sillages des rotors." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4708/document.
Full textAbstract:
Les tourbillons hélicoïdaux générés derrière les rotors sont étudiés. Pour les générer, une méthode basée sur le couplage entre la technique de la ligne active et un solveur des équations de Navier-Stokes (ENS), incompressibles et tridimensionnelles, a été développée. Elle consiste à modéliser la pâle par son équivalent de forces volumiques. Les équations, écrites en coordonnées cylindriques, sont résolues par un schéma de différences finies, écrit en parallèle. La méthode est d'ordre deux en temps et en espace. Le solveur des ENS a été validé par la reproduction des taux de croissance d'un écoulement de jet, instable, trouvés par la théorie d'instabilité linéaire. La comparaison avec des données expérimentales a montré que la méthode prédit bien l'aérodynamique de la pâle. Ensuite, le tourbillon de bout de pâle a été, en particulier, caractérisé. La vorticité et la vitesse azimutale ont été trouvées auto-similaire et la taille du coeur suit asymptotiquement la loi de diffusion linéaire 2D. Un modèle simple du coeur du tourbillon a été proposé. La présence d'une vitesse axiale dans le coeur du tourbillon a été montrée et a été caractérisée en fonction du rapport de vitesse au bout de la pâle. Finalement, une étude de stabilité du tourbillon a été faite en utilisant une vitesse angulaire variable pour perturber l'écoulement. Les taux de croissances des modes les plus instables sont en bon accord avec celui de l'instabilité d'appariement 2D des tourbillons. Trois types de modes ont été identifiés en fonction de la fréquence des perturbations et ont été trouvés similaires aux modes décrits par la théorie et aussi trouvés, précédemment, par l'expérience<br>This present work is aimed to study helical vortices encountered in the wakes of rotating elements. For this, the generation of a helical wake of a one-bladed-rotor in a laminar velocity field, is simulated by the actuator line method. This method is a coupling of a Navier-Stokes (NS) solver with the Actuator Line Method where the blade is replaced by the body forces. This method has been implemented in a finite difference code, that we have written in parallel to solve the 3D incompressible NS equations written in cylindrical coordinates. The order of accuracy of the method is two both in time and space. The NS solver was validated comparing growth rates of an unstable jet, found numerically, and those of linear instability theory. A good agreement was found. A good agreement was also found comparing numerical results to analytical formulations and experimental data. It was shown that the method predicts well the blade aerodynamics . Then, the helical tip vortex is characterized for different Reynolds numbers and Tip Speed Ratios. The vorticity and the azimuthal velocity were found self-similar and the vortex core follows asymptotically the linear 2D diffusion law. A simple model for the helical vortex core was proposed. The presence of an axial velocity inside the vortex core was highlighted. Then, a stability study of the helical tip vortex was done using an angular velocity dependent on time to perturb the flow. The largest growth rates were found in good agreement with those of the (2D) pairing instability. Three types of modes were identified based on the perturbation frequency. The results are similar to those found in previous analytical and experimental works
6
Selçuk, Savas Can. "Numerical study of helical vortices and their instabilities." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066138/document.
Full textAbstract:
Le travail présenté dans ce mémoire est une contribution à l'étude numérique des systèmes tourbillonnaires hélicoïdaux qui sont émis dans le sillage des rotors (éoliennes, hélicoptères,...) et de leurs instabilités. Ici, ces écoulements sont localement modélisés par un ensemble de tourbillons à symétrie hélicoïdale. À l'aide d'un code de simulation numérique directe dédié, des solutions de base quasi-stationnaires sont obtenues pour différents systèmes tourbillonnaires. Une caractérisation précise et détaillée de ces solutions est ensuite effectuée : vitesse de rotation, taille et ellipticité du cœur, structure des champs de vitesse et de vorticité... À l'aide d'un algorithme d'Arnoldi couplé à une version linéarisée du code, on détermine les modes dominants d'instabilité ayant la même symétrie que l'écoulement de base, en fonction des paramètres du système: nombre de vortex, pas hélicoïdal, taille de cœur, nombre de Reynolds et présence d'un vortex de moyeu. En dessous d'un certain pas hélicoïdal critique, l'instabilité est dominée par un mode de déplacement global analogue au mode d’appariement d'une allé infinie de points vortex ou d'anneaux tourbillonnaires. En régime non linéaire, ce mode est à l'origine d'une dynamique complexe du système: dépassements, saute-mouton et fusion. On utilise un autre code linéarisé pour déterminer les modes instables qui brisent la symétrie hélicoïdale de l'état de base, caractérisés par une longueur suivant l'axe. À faible nombre d'onde, ces modes induisent localement des rapprochements entre portions de spires voisines. À grand nombre d'onde, on observe un autre type de mode qui déforme les cœurs tourbillonnaires via l'instabilité elliptique<br>The work presented in this manuscript is a contribution to the numerical study of helical vortex systems and their instabilities, as encountered in the near wake of rotors (wind turbines, helicopters,~...). In this work, such flows are locally modelled within the framework of helical symmetry. Using a dedicated DNS code, helical quasi-stationary basic state solutions are obtained for several configurations, and accurate tools for their characterisation are developed: angular velocity, core size and ellipticity, structure of the velocity and vorticity fields... An Arnoldi algorithm is then coupled to a linearised version of the code. The dominant instability modes with the same symmetry as the base flow are extracted as a function of the system parameters: number of vortices, helical pitch, core size, Reynolds number, presence of a central hub vortex. Under a critical helical pitch, the instability is dominated by a global displacement mode analogous to the pairing mode of an infinite array of point vortices or vortex rings. In the nonlinear regime, this mode gives rise to complex dynamics: overtaking events, leapfrogging and merging. Another linearised code is then used to extract modes characterised by a wavelength along the helix, which break the helical symmetry of the base flow. At low wavenumbers, these modes induce local displacements of the vortices and bring together portions of neighbouring coils. At large wavenumbers, another type of mode is found, which deforms the vortex cores through the elliptical instability mechanism
7
BAMDAD-SOOFI, JAHANSHAH. "Performances mecaniques du rotor d'une eolienne darrieus et application a "aeolia 3" en fonctionnement." Paris, ENSAM, 1986. http://www.theses.fr/1986ENAM0006.
Full textAbstract:
Etude des contraintes et des deformees du rotor pour toute situation de fonctionnement optimal, suivant trois etapes de recherche: 1. Analyse de fabrication des pales d'aeolia 3 (forme troposkienne de construction, parametres geometriques, contraintes normales dues au procede de cintrage). 2. Analyse du comportement statique du rotor. 3. Analyse du comportement dynamique des pales en fonctionnement (y compris l'arret) avec determination des modes propres du rotor et des deformees modales. Deux methodes de calcul, toutes deux matricielles, ont ete etudiees selon les besoins en rapidite du calcul et de sa mise au point et selon les besoins de precision des resultats
8
Miazaki, Marcio. "Controle de vibrações em rotores flexíveis utilizando molas helicoidais de liga com memória de forma." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/152328.
Full textAbstract:
Submitted by Marcio Miazaki null (mmiazaki@gmail.com) on 2017-12-12T15:38:22Z
No. of bitstreams: 1
Dissertacao.pdf: 2498214 bytes, checksum: bbe1b8f57d985978dca7748b50feb796 (MD5)<br>Submitted by Marcio Miazaki null (mmiazaki@gmail.com) on 2017-12-14T11:25:02Z
No. of bitstreams: 1
Dissertacao.pdf: 2498214 bytes, checksum: bbe1b8f57d985978dca7748b50feb796 (MD5)<br>Submitted by Marcio Miazaki null (mmiazaki@gmail.com) on 2017-12-14T13:50:31Z
No. of bitstreams: 1
Dissertacao.pdf: 2498214 bytes, checksum: bbe1b8f57d985978dca7748b50feb796 (MD5)<br>Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2017-12-18T10:25:06Z (GMT) No. of bitstreams: 1
miazaki_m_me_ilha.pdf: 2498214 bytes, checksum: bbe1b8f57d985978dca7748b50feb796 (MD5)<br>Made available in DSpace on 2017-12-18T10:25:06Z (GMT). No. of bitstreams: 1
miazaki_m_me_ilha.pdf: 2498214 bytes, checksum: bbe1b8f57d985978dca7748b50feb796 (MD5)
Previous issue date: 2017-11-30<br>Este trabalho apresenta uma proposta de utilização de molas helicoidais de liga com memória de forma presentes em rotores flexíveis para a atenuação dos deslocamentos laterais decorrentes de forças de perturbação, notadamente das forças de desbalanceamento. Num primeiro momento, o trabalho apresenta os principais modelos constitutivos de ligas com memória de forma (LMF), onde o princípio de funcionamento deste tipo de material é demonstrado por meio de simulações numéricas, e os resultados obtidos são confrontados com dados disponíveis na literatura. Discute-se também a questão da utilização de um modelo mais simplificado para representar o comportamento da liga para diferentes carregamentos termomecânicos. Dois modelos termomecânicos são confrontados numericamente visando representar adequadamente o comportamento termomecânico da LMF durante as transformações de fase. O trabalho evolui para a construção do modelo matemático via elementos finitos de rotores flexíveis contendo molas helicoidais de LMF e por fim apresenta um conjunto de simulações numéricas para comprovar a eficiência e a potencialidade do procedimento teórico formulado. O trabalho termina comentando as potencialidades da proposta apresentada, discutindo as facilidades e dificuldades encontradas na sua implementação e apontando para o desenvolvimento de futuros estudos.<br>This work proposes shape memory alloy helical springs present in flexible rotors for the attenuation of lateral displacements mainly caused by unbalance forces. This work presents some constitutive models of shape memory alloys (SMA). The principle of operation of this type of material is demonstrated by numerical simulations and the results obtained are compared with data available in the literature. The present work investigates the use of a simplified model to represent the behavior of the SMA for different thermomechanical loads. Two thermomechanical models are numerically confronted in order to represent properly the thermomechanical behavior of the SMA during the phase transformations. Based on the finite element model of flexible rotors containing helical springs of SMA, the efficiency and the potentiality of the theoretical procedure are shown through numerical simulations. This work is concluded presenting the potentialities of the design methodology proposed and future developments to be implemented.
9
Lemouchi, Cyprien. "Moteurs Moléculaires Cristallins Photo-pilotés." Phd thesis, Université d'Angers, 2010. http://tel.archives-ouvertes.fr/tel-00801226.
Full textAbstract:
L'engouement aujourd'hui pour la manipulation des propriétés électriques des supraconducteurs moléculaires dans le domaine des matériaux, nous a conduit à installer des gyroscopes au sein du cristal, pour que la propriété dynamique puisse moduler l'environnement électrostatique pouvant déboucher vers un nouvel ordre de charge et des structures ferroélectriques. Une machine moléculaire qui possède un rotor, un axe de rotation et des stators tel que le 1,4-diéthynylbicyclo[2,2,2]octane, a été choisie pour sa particularité à interagir avec la lumière, que l'on organise au sein du solide, sous forme de monocristaux appelés moteurs cristallins. La RMN CP/MAS sur poudre cristalline et monocristal a permis de caractériser le mouvement du rotor. Le développement d'une approche cristalline ajouté à la fonctionnalisation des rotors ont permis leur auto-assemblage et leur installation dans des architectures ouvertes organisées autour de cation métalliques (MOF,PCP,), ce qui a permis l'élaboration de matériaux multifonctionnels, dotés de la fonction dynamique, aux propriétés de conductivité ou de transition spin (SCO-MOF). Finalement, l'étude de systèmes cristallins dynamiques de basse dimentionnalité en optique non linéaire a permis de mettre en évidence le phénomène de photo-pilotage des gyroscopes par la lumière au sein du solide. le développement de systèmes plus élaborés permettra de mieux comprendre ce phénomène afin de l'utiliser dans des applications industrielles.
10
Chieh-WeiYang and 楊介偉. "Dynamic Analysis of a Helical Geared Rotor-Bearing System." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/91774903102380853258.
Full textBooks on the topic "Helical rotor"
1
Childs, Dara W. SSME seal test program: Test results for smooth, hole-pattern, and helically grooved stators : interim progress report. Texas A&M, Turbomachinery Laboratories, Mechanical Engineering Dept., 1987.
Find full textBook chapters on the topic "Helical rotor"
1
Amiri, Ebrahim, and Ernest Mendrel. "Induction Motors with Rotor Helical Motion." In Induction Motors - Modelling and Control. InTech, 2012. http://dx.doi.org/10.5772/48056.
Full text
2
Holmes, C. S. "Developments in the productive grinding of screw rotors and other helical parts in response to user feedback." In 7th International Conference on Compressors and their Systems 2011. Elsevier, 2011. http://dx.doi.org/10.1533/9780857095350.7.337.
Full textConference papers on the topic "Helical rotor"
1
Simmons, Larry D. "Simulation Model for Helical Rotor Expanders." In ASME 1991 International Computers in Engineering Conference and Exposition. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/cie1991-0082.
Full textAbstract:
Abstract The objective of this project was to develop a computer model for the helical rotor expander which can be used to determine performance potential and to facilitate optimization of expander design. Testing has shown that this energy conversion device has substantial potential advantages over conventional turbines in very high temperature cycles and for two-phase flow. However, the tests have been limited to particular non-optimized designs, and a model is badly needed to assess viable design improvements and their effects on performance. A computer model was developed to simulate the geometric and thermal/fluid characteristics of the expander to give power output, mass flow rate, and efficiency versus rotational speed for any chosen design configuration. The model has been tested against experimental data from expanders running on nitrogen gas and two-phase steam with good agreement. It is now ready and available for use in developing and evaluating designs for new applications of the helical rotor expander.
2
Fang, Zhi, Zhigang Li, Jun Li, and Zhenping Feng. "Numerical Investigation on the Static and Rotordynamic Characteristics for Two Types of Novel Mixed Helical Groove Seals." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-16303.
Full textAbstract:
Abstract Non-contracting annular seals, such as helical groove seals, are widely used between the impeller stages in the liquid turbomachinery to reduce the fluid leakage and stabilize the rotor-bearing system. However, previous literature has expounded that the helical groove seals possess the poor sealing property at low rotational speed condition and face the rotor instability problem inducing by negative stiffness and damping, which is undesirable for liquid turbomachinery. In this paper, to obtain the high sealing performance and the reliable rotordynamic capability for full operational conditions of the machine, two novel mixed helical groove seals, which possess a hole-pattern/pocket-damper stator matching with a helically-grooved rotor, were designed and assessed for a multiple-stage high-pressure centrifugal liquid pump. In order to assess the static and rotordynamic characteristics of these two types of mixed helical groove seals, a three-dimensional (3D) steady CFD-based method with the multiple reference frame theory was used to predict the seal leakage and drag power loss. Moreover, a proposed 3D transient CFD-based perturbation method, based on the multi-frequency one-dimensional stator whirling model, the multiple reference frame theory and a mesh deformation technique, was utilized for the predictions of seal rotordynamic characteristics. The accuracy of the numerical methods was demonstrated based on the experiment data of leakage and rotordynamic forces coefficients of published helical groove seals and hole-pattern seal. The leakage and rotordynamic forces coefficients of these two mixed helical groove seals were presented at five rotational speeds (0.5 krpm, 2.0 krpm, 4.0 krpm, 6.0 krpm, 8.0 kpm) with large pressure drop of 25MPa, and compared with three types of conventional helical groove seal (helical grooves on rotor, stator or both), and two types of damper seals (hole-pattern seal, pocket damper seal with smooth rotor). Numerical results show that the mixed groove seals possess generally better sealing capacity than the conventional helical groove seals, especially at low rotational speed conditions. The circumferentially-isolated cavities (hole or pocket) on the stator enhance the “pumping effect” of the helical grooves for mixed helical groove seals, what is more, the helical grooves also strengthen the dissipation of kinetic energy in the isolated cavities, thus the mixed helical groove seal offers less leakage. Although the mixed helical groove seals possess a slightly larger drag power loss, it is acceptable in consideration of reduced leakage for the high-power turbomachinery. The present novel mixed helical groove seals have pronounced stability advantages over the conventional helical groove seal, due to the obvious large positive stiffness and increased damping. The mixed helical groove seal with the hole-pattern stator and the helically-grooved rotor (HPS/GR) possesses the lowest leakage and the largest effective damping, especially for the high rotational speeds. From the viewpoint of sealing capacity and rotor stability, the novel mixed groove seals are better seal concepts for liquid turbomachinery.
3
M.A., Kamoji, Kedare S.B., and S. V. Prabhu. "Wind Tunnel Tests on a Single Stage Helical Savonius Rotor." In 5th International Energy Conversion Engineering Conference and Exhibit (IECEC). American Institute of Aeronautics and Astronautics, 2007. http://dx.doi.org/10.2514/6.2007-4710.
Full text
4
Liangyao, Gu, Chen Feng, Yang Yue, and Jia Chunyang. "Design and Realization of helical rotor NC automatic programming system." In 2012 2nd International Conference on Applied Robotics for the Power Industry (CARPI 2012). IEEE, 2012. http://dx.doi.org/10.1109/carpi.2012.6356471.
Full text
5
Zhao, Zhenzhou, Yuan Zheng, Xiaoyun Xu, Wenming Liu, and Daqing Zhou. "Optimum Design Configuration of Helical Savonius Rotor via Numerical Study." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78430.
Full textAbstract:
A helical Savonius rotor with two blades and 180 degree helical angle is researched to optimize the rotor power coefficient CP via numerical study from different parameters like overlap ratio, diameter of endplates, and number of inner plates within buckets and aspects ratio. The results from the study show that the rotor gets better performances when overlap ratio equals to 0.19, or the diameter of end plates is around 10% more than that of the rotor rotation, or the number of inner plates is 6, or aspects ratio is 6.0. The maximum power coefficient CPmax of rotor reaches 0.21 when overlap ratio equals to 0.19, and the diameter of end plates is around 10% more than that of the rotor rotation, and the number of inner plates is 6, and aspects ratio is 6.0. The numerical study results coincide well with experimental results, that means the model results is credible.
6
Schröder, Dominic, Thomas Leweke, Ralf Hörnschemeyer, and Eike Stumpf. "Experiments on helical vortex pairs in the wake of a rotor." In AIAA Scitech 2021 Forum. American Institute of Aeronautics and Astronautics, 2021. http://dx.doi.org/10.2514/6.2021-1088.
Full text
7
Zullah, Mohammed Asid, Deepak Prasad, Young-Do Choi, et al. "Study on the performance of helical savonius rotor for wave energy conversion." In THE 10TH ASIAN INTERNATIONAL CONFERENCE ON FLUID MACHINERY. AIP, 2010. http://dx.doi.org/10.1063/1.3464913.
Full text
8
Dobzhanskyi, Oleksandr. "PM BLDC Actuator with Helical Motion of the Rotor For Industrial Applications." In 2019 IEEE Texas Power and Energy conference (TPEC). IEEE, 2019. http://dx.doi.org/10.1109/tpec.2019.8662162.
Full text
9
Watson, Cori, and Houston G. Wood. "Optimizing a Helical Groove Seal With Grooves on Both the Rotor and Stator Surfaces." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64687.
Full textAbstract:
Helical groove seals are non-contacting annular seals commonly used in pumps within the impeller stages to sustain a pressure differential for a given leakage. Helical groove seals have continuously cut grooves, like the threads of a screw, on the surface of the rotor, the surface of the stator, or both. The two main components of the flow within helical groove seals are axial flow and groove flow. The axial flow serves to reduce the leakage by dissipating kinetic energy as the fluid expands in the grooves and then is forced to contract within the jet stream region. The groove flow serves to reduce the leakage by acting as screw pump. The fluid within the grooves is displaced towards the high pressure region as it spins with the rotor. Previous work has shown that seals with grooves on both the surface of the rotor and the surface of the stator can sustain higher pressure differentials for a given leakage than seals with grooves on only one surface. The goal of this study is to optimize the leakage performance of a double surface helical groove seal for a given set of operating conditions. To accomplish this goal, simulations are run in ANSYS CFX. A sufficient mesh with appropriate boundary layers is determined from the mesh independence study. The turbulence model is k-ε turbulence for water at 25°C. This is the first paper to present numerical results for the performance of helical groove seals with grooves on both the rotor and the stator. The design parameters used in the optimization are inner (rotor) groove size, inner helix angle, outer (stator) groove size, and outer helix angle. A Kennard-Stone algorithm, which optimally spaces the simulations within the design space, is used to select the designs to be simulated. A multifactor quadratic regression is derived. Backward regression is used to reduce the performance function to only statistically significant terms. Finally, the optimal seal design is derived from the performance function and is simulated to demonstrate the predictive power of the performance function. Interaction terms for the rotor and stator design parameters will be used to explore the mechanism whereby helical groove seals with grooves on both the rotor and the stator surfaces are able to have lower leakage than helical groove seals with grooves on just one surface. The end result of this study is a seal design which minimizes leakage and therefore improve machine efficiency.
10
Paudel, Wisher, Cori Watson, and Houston G. Wood. "The Impact of Adding a Labyrinth Surface to an Optimal Helical Seal Design." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87089.
Full textAbstract:
Non-contacting annular seals are used in rotating machinery to reduce the flow of working fluid across a pressure differential. Helical and labyrinth grooved seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump and at the balance drum. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves on either or both the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy, but have the added mechanism of functioning as a pump to push the fluid back towards the high-pressure region. Previous work has shown that mixed helical-labyrinth seals with labyrinth grooves on stator and helical grooves on rotor or labyrinth grooves on rotor and helical grooves on stator have an approximately 45% lower leakage than an optimized helical groove seal with grooves just on the stator in a high pressure application. The primary objective of this study is to determine whether the same performance gains can also be achieved in a low pressure application. Simulations were run in ANSYS CFX for seal designs with a helical stator and labyrinth rotor. Several labyrinth design parameters including the number of grooves and the groove width and depth are varied while the helical variables such as the groove width and depth as well as helix angle are kept constant. The data obtained are analyzed using backward regression methods and various response plots to determine the relationship between the design parameters and mass flow and power loss. The optimized helical design was simulated and the axial pressure profiles of the designs were compared to analyze the mechanism of the mixed helical-labyrinth seal. Then, the same labyrinth seal designs were simulated for a labyrinth rotor and a smooth stator to determine whether the optimal number of grooves, groove width and groove depth change due to the helical stator. The findings of this study show the effectiveness of mixed helical labyrinth grooved seals for both low and high pressure cases, and thus their efficiency and reliability for numerous industrial applications.