The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Kim A. Stelson - One of the best experts on this subject based on the ideXlab platform.
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improving the reliability and energy production of large wind turbine with a digital hydrostatic drivetrain
Applied Energy, 2019Co-Authors: Feng Wang, Jincheng Chen, Bing Xu, Kim A. StelsonAbstract:Abstract Gearbox failure is one of the major factors causing the increased downtime in modern wind turbines. This increases the turbine maintenance cost and therefore the turbine cost of energy. A hydrostatic transmission not only improves the turbine reliability through its “soft” transmission, but also eliminates the use of power converter through its continuous variable transmission function. A hydrostatic wind turbine usually employs a fixed displacement pump to drive a variable displacement motor. The variable displacement motor runs at partial displacement when the wind speed is below the rated wind speed, leading to low drivetrain efficiency. Moreover, large variable displacement motors for large utility wind turbine are not commercially available. Therefore in this paper a digital hydrostatic transmission solution for large utility wind turbine has been proposed. The large variable displacement motor was replaced by combining several fixed displacement motors and a small variable displacement motor with some digital encoding scheme. Two encoding schemes have been proposed for digital hydrostatic transmission. The modeling and design of the digital hydrostatic wind turbine were presented. A hydrostatic wind turbine control based on kw2 control law has been proposed. A dynamic simulation model of the digital hydrostatic wind turbine has been developed. The proposed digital hydrostatic drive solution has been compared with a conventional hydrostatic solution in a commercial 2.5 MW wind turbine. Simulation studies verified the feasibility and the engineering practice of the proposed digital hydrostatic drive solution.
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A Novel Digitalized Hydrostatic Drive Solution for Modern Wind Turbine
ASME BATH 2017 Symposium on Fluid Power and Motion Control, 2017Co-Authors: Jincheng Chen, Feng Wang, Kim A. StelsonAbstract:Gearbox is a concern in modern wind turbines, increasing the maintenance cost and therefore the cost of energy (COE). A hydrostatic transmission (HST) improves the turbine drivetrain reliability by using slightly compressible mineral oil as the working medium rather than a rigid gearbox. An HST eliminates the power converter since it is a continuous variable transmission (CVT), making the turbine simpler and more cost effective. The turbine operates below the rated wind speed for a considerable time in a year, making the variable hydraulic motor run at partial displacement for the most common configuration of a hydrostatic wind turbine, a fixed displacement pump and a variable displacement motor. This results in low drivetrain efficiency. Moreover, large variable displacement motors for megawatt turbine are commercially unavailable. A digitalized hydrostatic drive for a modern wind turbine is proposed to improve the drivetrain efficiency at low wind speeds. The digital coding method for hydrostatic wind turbine is studied. A dynamic simulation model of the digitalized hydrostatic (dHST) wind turbine has been developed in Simulink. A widely used efficiency model for the hydrostatic pump and motors is used in the simulation to make the study practical. The proposed digitalized hydrostatic solution has been compared with a conventional hydrostatic solution. Simulation results show the benefits of digitalized hydrostatic transmission over conventional hydrostatic transmission in drivetrain efficiency, system complexity and cost.
Rafael Mañanes - One of the best experts on this subject based on the ideXlab platform.
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Some considerations about non-hydrostatic vs. hydrostatic simulation of short-period internal waves. A case study: The Strait of Gibraltar
Continental Shelf Research, 2019Co-Authors: O. Álvarez, Alfredo Izquierdo, C.j. González, Miguel Bruno, Rafael MañanesAbstract:Abstract A 3-D nonlinear, finite-difference, high-resolution, hydrodynamic model, extended with a direct implementation of the non-hydrostatic pressure, is applied to study the influence of the non-hydrostatic contribution to the generation and propagation of short-period wave fronts (less than 1 h) in the domain of the Gibraltar Strait. The generation, rupture and propagation of these waves and their free surface manifestations are shown. Calculations of the model show its ability to generate surface wave fronts. However, differences in the period and wavelength of the generated baroclinic waves are evident when hydrostatic and non-hydrostatic results are compared. In particular, the non-hydrostatic contribution tends to generate short-period waves with longer wavelengths and periods with respect to the hydrostatic values. An increase of the non-hydrostatic short-period wavelengths from the Camarinal Sill towards the Mediterranean Sea is also plausible. This increase is induced by changes in the thickness of the deeper layer that influences the disintegration of wave fronts into wave trains and the imbalance of non-hydrostatic and non-linear contributions. Sensitivity analyses show that grid resolution is a key factor due to the potential generation of spurious non-hydrostatic processes, including numerical dispersion induced by a low grid resolution. It is shown that this numerical non-hydrostatic process could generate similar results in hydrostatic and non-hydrostatic simulations when the spatial resolution is comparable to the wavelengths. Results also show the ability of the direct implementation of the non-hydrostatic model to reproduce the main features in a real case, such as the Strait of Gibraltar.
Alan Chalmers - One of the best experts on this subject based on the ideXlab platform.
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Descartes’ Engagement with Hydrostatics
Archimedes, 2017Co-Authors: Alan ChalmersAbstract:The young Descartes was involved in contributing to the sciences of his day, especially mechanics and optics and including a brief, unpublished, foray into Hydrostatics. Such involvements persisted into his maturity, but came to play a role subsidiary to Descartes’ ambitious plan to construct an outline of the ultimate, corpuscular, structure of the universe in its entirety. Descartes’ contributions to Hydrostatics need to be extracted piecemeal from his writings because he did not offer a systematic treatment. In the early, unpublished, work Descartes did respond to some of Stevin ’s results in a way that can be interpreted as having potential, but he did not pursue those early thoughts. The corpuscular system of the world outlined in Descartes’ Principles of Philosophy treated pressure in liquids and the transmission of light in analogous ways. Both were seen as resulting from the transmission of pushes from corpuscle to corpuscle. This had the result that the linear transmission of hydrostatic forces in liquids was as fundamental as the linear transmission of light. In retrospect at least it can be seen that Descartes’ Hydrostatics was ill-equipped to deal with the isotropy of hydrostatic forces that had been identified by Stevin.
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Hydrostatics and Experiment
Archimedes, 2017Co-Authors: Alan ChalmersAbstract:This chapter is concerned with capturing exactly what is involved in the idea that the progression in Hydrostatics from Stevin to Newton corresponded to the shift from the attempt to construct a science on the basis of given, unproblematic, postulates to the recognition that the adequacy of postulates needed to be discovered and justified via experiment. The importance that experiment could play in the discovery of previously unknown phenomena was clear in the context of pneumatics in the wake of Torricelli’s experiment. However, as far as Hydrostatics is concerned, the move from Stevin to Newton did not involve discovery of hydrostatic phenomena that were significantly novel. If a theory is supported by a range of evidence to the extent that it can explain it in an uncontrived way, then it can be supported by old as well as new evidence. The path from Stevin to Newton can be seen as involving steadily increasing degrees of support from a largely unchanging pool of evidence because of the extent to which that evidence could be naturally explained to an increasing degree. Other roles for experiment in seventeenth-century Hydrostatics can be clearly discerned in the work of Boyle. Those roles concern the way in which thought-directed manipulation can contribute to novel concept formation and the way in which the exposition of a theory can be facilitated by key thought experiments or archetypal experiments actually performed.
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Hydrostatics and the Scientific Revolution
Archimedes, 2017Co-Authors: Alan ChalmersAbstract:The extent to which dealings with the world as it can be observed and manipulated is dependent on the availability of concepts up to the task has not been adequately appreciated by historians of science. Detailed attention to changes that the concept of pressure underwent in the seventeenth century can serve to ameliorate that situation. The history of Hydrostatics can also usefully illustrate the way in which science emerged in the seventeenth century as autonomous from mathematics, practitioners’ knowledge and metaphysics. Hydrostatics employed mathematics but differed from mathematics insofar as its postulates were in need of empirical support. As far as practitioner’s knowledge of Hydrostatics is concerned, that did not change much during the seventeenth century. However, the level of understanding of Hydrostatics was much deepened by way of theories that could explain what was taken for granted by practitioners. Finally, knowledge of Hydrostatics was distinct from the accounts of the ultimate structure of the world favored by mechanical philosophers. It owed little to their attempts to construct such a metaphysics. From a modern point of view the technical sense of pressure can appear obvious. There is much to be learnt about science by recovering the way in which it became obvious.
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The Historical Background to Stevin’s Hydrostatics
Archimedes, 2017Co-Authors: Alan ChalmersAbstract:The starting point of my story is the account of Hydrostatics formulated by Simon Stevin in 1586. He could take for granted a distinction between liquids and solids which formed part of everyday knowledge and which was presumed in common technologies involving the management of water. Stevin could also take for granted the science of simple machines that had been developed with considerable sophistication in the sixteenth century. Stevin explicitly based his theory of Hydrostatics on Archimedes’ work on floating bodies, building on its content as well as adopting its style of reasoning. The propositions of Hydrostatics were to be derived from postulates sufficiently unproblematic to be granted at the outset.
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one hundred years of pressure Hydrostatics from stevin to newton
2017Co-Authors: Alan ChalmersAbstract:Chapter 1. The theoretical challenge posed for seventeenth century mechanics by fluids.Chapter 2. The background to Simon Stevin's Hydrostatics.Chapter 3. Moving beyond Archimedes: The Hydrostatics of Simon StevinChapter 4. Galileo, floating bodies and the balanceChapter 5. Descartes' engagement with HydrostaticsChapter 6. Pascal on the equilibrium of liquidsChapter 7. Experimenting with, and theorizing about, airChapter 8. Boyle and the concept of pressureChapter 9. Newton's Hydrostatics: Pressure in a continuum, following Boyle, rather than corpuscle pressing on corpuscle, following Descartes.Chapter 10. Reflections on the role of theory and experiment in the emergence of HydrostaticsChapter 11. Reflections on the significance of the history of Hydrostatics: What was revolutionary about the scientific revolution?
Shigeru Tabeta - One of the best experts on this subject based on the ideXlab platform.
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Unsteady Buoyant Jet Simulations Using Dynamic Connection Scheme of Hydrostatic and Non-Hydrostatic Zone
29th International Conference on Ocean Offshore and Arctic Engineering: Volume 3, 2010Co-Authors: Masanobu Hasebe, Shigeru TabetaAbstract:Most of ocean models employ hydrostatic approximation because the horizontal scale is usually much larger than the vertical scale in oceanic phenomena. In hydrostatic approximation, dynamic pressure is neglected and the momentum equation in vertical direction needs not to be solved. But for the phenomena of buoyant jet from the sea bottom such as submarine groundwater discharge, hydrothermal plume and so on, hydrodynamic pressure cannot be neglected and the momentum equation of vertical direction must to be taken into account. Non-hydrostatic analysis requires so much computation time that it is usually difficult to calculate the current field in the wide ocean area by this approach. On the other hand, analysis assuming the hydrostatic approximation needs less computational time and usually gives reasonable results for large scale ocean phenomena such as tidal current. In the present study, the authors developed a new type of ocean model for multi-scale analysis, which conducts hydrostatic analysis for phenomena in wide area and non-hydrostatic analysis for the detail flow around the buoyant jet simultaneously. The application limit of hydrostatic approximation for ocean model was investigated, and a dynamic connection method of hydrostatic zone with non-hydrostatic zone was developed. By theoretical consideration employing parameter δ and e which represent the ratio of grid size Δz to Δx and the ratio of vertical velocity to horizontal velocity, it was found that hydrostatic approximation can be applied if δe and e2 are minute. To examine the developed method, simulations for lock-exchange problem and vertical jet under oscillating current were conducted. The result by the present model was similar to that of non-hydrostatic model in the case that hydrostatic approximation was applied on the area of δe
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Dynamic Connection of Hydrostatic and Non-Hydrostatic Zone for Coastal Hydrodynamic Model
Journal of Japan Society of Civil Engineers Ser. B2 (Coastal Engineering), 2009Co-Authors: Masanobu Hasebe, Shigeru TabetaAbstract:Application limit of hydrostatic approximation for coastal hydrodynamic model was investigated, and a dynamic connection method of hydrostatic zone with non-hydrostatic zone was developed. By theoretical consideration employing parameter δ and e which represent the ratio of mesh size Δz to Δx and the ratio of vertical velocity to horizontal velocity, it was found that hydrostatic approximation can be applied if δe and e2 are minute. To examine the developed method, simulations for vertical jet under oscillating current was conducted. The result by the present model was similar to that of non-hydrostatic model in the case that hydrostatic approximation was applied on the area of δe
Feng Wang - One of the best experts on this subject based on the ideXlab platform.
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improving the reliability and energy production of large wind turbine with a digital hydrostatic drivetrain
Applied Energy, 2019Co-Authors: Feng Wang, Jincheng Chen, Bing Xu, Kim A. StelsonAbstract:Abstract Gearbox failure is one of the major factors causing the increased downtime in modern wind turbines. This increases the turbine maintenance cost and therefore the turbine cost of energy. A hydrostatic transmission not only improves the turbine reliability through its “soft” transmission, but also eliminates the use of power converter through its continuous variable transmission function. A hydrostatic wind turbine usually employs a fixed displacement pump to drive a variable displacement motor. The variable displacement motor runs at partial displacement when the wind speed is below the rated wind speed, leading to low drivetrain efficiency. Moreover, large variable displacement motors for large utility wind turbine are not commercially available. Therefore in this paper a digital hydrostatic transmission solution for large utility wind turbine has been proposed. The large variable displacement motor was replaced by combining several fixed displacement motors and a small variable displacement motor with some digital encoding scheme. Two encoding schemes have been proposed for digital hydrostatic transmission. The modeling and design of the digital hydrostatic wind turbine were presented. A hydrostatic wind turbine control based on kw2 control law has been proposed. A dynamic simulation model of the digital hydrostatic wind turbine has been developed. The proposed digital hydrostatic drive solution has been compared with a conventional hydrostatic solution in a commercial 2.5 MW wind turbine. Simulation studies verified the feasibility and the engineering practice of the proposed digital hydrostatic drive solution.
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A Novel Digitalized Hydrostatic Drive Solution for Modern Wind Turbine
ASME BATH 2017 Symposium on Fluid Power and Motion Control, 2017Co-Authors: Jincheng Chen, Feng Wang, Kim A. StelsonAbstract:Gearbox is a concern in modern wind turbines, increasing the maintenance cost and therefore the cost of energy (COE). A hydrostatic transmission (HST) improves the turbine drivetrain reliability by using slightly compressible mineral oil as the working medium rather than a rigid gearbox. An HST eliminates the power converter since it is a continuous variable transmission (CVT), making the turbine simpler and more cost effective. The turbine operates below the rated wind speed for a considerable time in a year, making the variable hydraulic motor run at partial displacement for the most common configuration of a hydrostatic wind turbine, a fixed displacement pump and a variable displacement motor. This results in low drivetrain efficiency. Moreover, large variable displacement motors for megawatt turbine are commercially unavailable. A digitalized hydrostatic drive for a modern wind turbine is proposed to improve the drivetrain efficiency at low wind speeds. The digital coding method for hydrostatic wind turbine is studied. A dynamic simulation model of the digitalized hydrostatic (dHST) wind turbine has been developed in Simulink. A widely used efficiency model for the hydrostatic pump and motors is used in the simulation to make the study practical. The proposed digitalized hydrostatic solution has been compared with a conventional hydrostatic solution. Simulation results show the benefits of digitalized hydrostatic transmission over conventional hydrostatic transmission in drivetrain efficiency, system complexity and cost.
