Download or read book Design and Critical Performance Evaluation of Horizontal Axis Hydrokinetic Turbines written by Suchi Subhra Mukherji and published by . This book was released on 2010 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The current work discusses the hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkT) under different turbine geometries and flow conditions. Hydrokinetic turbines are a class of zero-head hydropower systems which utilize kinetic energy of flowing water to drive a generator. However, such turbines often suffer from low-efficiency. A detailed computational fluid dynamics study was performed using a low-order k-[omega] SST (Shear Stress Transport) turbulence model to examine the effect of each of tip-speed ratio, solidity, angle of attack and number of blades on the performance of small HAHkTs with a power capacity of 10 kW. The numerical models (both two-dimensional and three-dimensional) developed for these purposes were validated with blade element momentum theory. The two-dimensional numerical models suggest an optimum angle of attack that maximizes lift as well as lift to drag ratio thereby yielding the maximum power output. In addition, our three-dimensional model is used to estimate optimum turbine solidity and blade numbers that produces maximum power coefficient at a given tip speed ratio. Furthermore, the axial velocity deficit downstream of the turbine rotor provides quantitative details of energy loss suffered by each turbine at ambient flow conditions. The velocity distribution provides confirmation of the stall-delay phenomenon that occurs due to the rotation of the turbine. In addition, it provides further verification of optimum tip speed ratio corresponding to maximum power coefficient obtained from the solidity analysis"--Abstract, leaf iii.

Download or read book Performance Evaluation of Coaxial Horizontal Axis Hydrokinetic Turbines System written by Abdulaziz Mohammed Abutunis and published by . This book was released on 2014 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Hydrokinetic energy technologies are emerging as a viable solution for renewable power generation. Unlike conventional hydropower turbines, hydrokinetic turbines are environmentally friendly; they operate at zero-head, and do not need dams to preserve the water. Unfortunately, they have a low efficiency which makes their design a challenging task. This work was focused on the hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkTs) under different turbine arrangements and flow conditions. It was undertaken in an effort to improve the efficiency of small HAHkTs that harness a river’s kinetic energy. Four sets of experiments were performed in a water tunnel to investigate small-scale constant cross-section HAHkT models with various configurations. The first set of experiments provided insight into the operating characteristics of a 3-blade single turbine by varying its pitch angle ([theta]) , tip speed ratio (TSR), flow speed (U[sub infinity]), and applied load. A multi-turbine system of both two and three 3- blade rotors (mounted coaxially to the same shaft) was tested in the second set of experiments. The purpose was to decrease the turbine system solidity while increasing the blade number. Here, the number of and the distance between rotors as well as the rotors relative installation angle were investigated. A long duct reducer was used to shroud single turbine and multi- turbine system in the third set of experiments. The particle image velocimetry (PIV) technique was used in the final set of experiments to examine the flow patterns at different axial locations downstream from two different turbine configurations. The effect of the flow speed on the wake characteristics was also examined in this experiment"--Abstract, page iii.

Download or read book Vertical Axis Hydrokinetic Turbines Numerical and Experimental Analyses written by Mabrouk Mosbahi and published by Bentham Science Publishers. This book was released on 2021-12-14 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook is a guide to numerical and experimental processes that are used to analyze and improve the efficiency of vertical axis rotors. Chapters present information that is required to optimize the geometrical parameters of rotors or understand how to augment upstream water velocity. The authors of this volume present a numerical model to characterize the water flow around the vertical axis rotors using commercial CFD code in Ansys Fluent®. The software has been used to select adequate parameters and perform computational simulations of spiral Darrieus turbines. The contents of the volume explain the experimental procedure carried out to evaluate the performance of the spiral Darrieus turbine, how to characterize the water flow in the vicinity of the tested turbine and the method to assess the spiral angle influence on the turbine performance parameters. Results for different spiral angles (ranging from 10° to 40°) are presented. This volume is a useful handbook for engineers involved in power plant design and renewable energy sectors who are studying the computational fluid dynamics of vertical axis turbines (such as Darrieus turbines) that are used in hydropower projects. Key features: - 4 chapters that cover the numerical and experimental analysis of vertical axis rotors and hydrokinetic turbines - Simple structured layout for easy reading (methodology, models and results) - Bibliographic study to introduce the reader to the subject - A wide range of parameters included in experiments - A comprehensive appendix of tables for mechanical parameters, statistical models, rotor parameters and geometric details.

Download or read book Aerodynamics of Wind Turbines 2nd edition written by Martin O. L. Hansen and published by Routledge. This book was released on 2013-05-13 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its second edition, it has been entirely updated and substantially extended to reflect advances in technology, research into rotor aerodynamics and the structural response of the wind turbine structure. Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element Momentum method is also covered, as are eigenmodes and the dynamic behaviour of a turbine. The new material includes a description of the effects of the dynamics and how this can be modelled in an ?aeroelastic code?, which is widely used in the design and verification of modern wind turbines. Further, the description of how to calculate the vibration of the whole construction, as well as the time varying loads, has been substantially updated.

Download or read book Effect of Shroud on the Performance of Horizontal Axis Hydrokinetic Turbines written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Performance Evaluation Emulation and Control of Cross flow Hydrokinetic Turbines written by Robert J. Cavagnaro and published by . This book was released on 2016 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross-flow hydrokinetic turbines are a promising option for effectively harvesting energy from fast-flowing streams or currents. This work describes the dynamics of such turbines, analyzes techniques used to scale turbine properties for prototyping, determines and demonstrates the limits of stability for cross-flow rotors, and discusses means and objectives of turbine control. This involves a progression from the analysis of a laboratory-scale prototype turbine to the emulation of a field-scale commercial turbine under realistic control. Understanding of turbine and system component dynamics and performance is leveraged at each phase, with the ultimate goal of enhancing the efficacy of prototype testing and enabling safer, more advanced control techniques. Novel control strategies are under development to utilize low-speed operation (slower than at maximum power point) as a means of shedding power under rated conditions. However, operation in this regime may be unstable. An experiment designed to characterize the stability of a laboratory-scale cross-flow turbine operating near a critically low speed yields evidence that system stall (complete loss of ability to rotate) occurs due, in part, to interactions with turbulent decreases in flow speed. The turbine is capable of maintaining 'stable' operation at critical speed for short duration (typically less than 10 s), as described by exponential decay. The presence of accelerated 'bypass' flow around the rotor and decelerated 'induction' region directly upstream of the rotor, both predicted by linear momentum theory, are observed and quantified with particle image velocimetry (PIV) measurements conducted upstream of the turbine. Additionally, general agreement is seen between PIV inflow measurements and those obtained by an advection-corrected acoustic Doppler velocimeter (ADV) further upstream. Definitive evidence linking observable flow events to the onset of system stall is not found. However, a link between turbulent kinetic energy of the flow, the system time constant, and the turbine's dynamic response to turbulence indicates changes in the flow occurring over a horizon of several seconds create the conditions under which system stall is likely. Performance of a turbine at small (prototype) geometric scale may be prone to undesirable effects due to operation at low Reynolds number and in the presence of high channel blockage. Therefore, testing at larger scale, in open water is desirable. A cross-flow hydrokinetic turbine with a projected area (product of blade span and rotor diameter) of 0.7 m^2 is evaluated in open-water tow trials at three inflow speeds ranging from 1.0 m/s to 2.1 m/s. Measurements of the inflow velocity, the rotor mechanical power, and electrical power output of a complete power take-off (PTO) system are utilized to determine the rotor hydrodynamic efficiency (maximum of 17%) and total system efficiency (maximum of 9%). A lab-based dynamometry method yields individual component and total PTO efficiencies, shown to have high variability and strong influence on total system efficiency. The method of tow-testing is found effective, and when combined with PTO characterization, steady-state performance can be inferred solely from inflow velocity and turbine rotation rate. Dynamic efficiencies of PTO components can effect the overall efficiency of a turbine system, a result from field characterization. Thus, the ability to evaluate such components and their potential effects on turbine performance prior to field deployment is desirable. Before attempting control experiments with actual turbines, hardware-in-the-loop testing on controllable motor-generator sets or electromechanical emulation machines (EEMs) are explored to better understand power take-off response. The emulator control dynamic equations are presented, methods for scaling turbine parameters are developed and evaluated, and experimental results are presented from three EEMs programmed to emulate the same cross-flow turbine. Although hardware platforms and control implementations varied, results show that each EEM is successful in emulating the turbine model at different power levels, thus demonstrating the general feasibility of the approach. However, performance of motor control under torque command, current command, or speed command differed; torque methods required accurate characterization of the motors while speed methods utilized encoder feedback and more accurately tracked turbine dynamics. In a demonstration of an EEM for evaluating a hydrokinetic turbine implementation, a controller is used to track the maximum power-point of the turbine in response to turbulence. Utilizing realistic inflow conditions and control laws, the emulator dynamic speed response is shown to agree well at low frequencies with simulation but to deviate at high frequencies. The efficacy of an electromechanical emulator as an accurate representation of a fielded turbine is evaluated. A commercial horizontally-oriented cross-flow turbine is dynamically emulated on hardware to investigate control strategies and grid integration. A representative inflow time-series with a mean of 2 m/s is generated from high-resolution flow measurements of a riverine site and is used to drive emulation. Power output during emulation under similar input and loading conditions yields agreement with field measurements to within 3% at high power, near-optimal levels. Constant tip-speed ratio and constant speed proportional plus integral control schemes are compared to optimal nonlinear control and constant resistance regulation. All controllers yield similar results in terms of overall system efficiency. The emulated turbine is more responsive to turbulent inflow than the field turbine, as the model utilized to drive emulation does not account for a smoothing effect of turbulent fluctuations over the span of the fielded turbine's rotors. The turbine has a lower inertia than the demand of an isolated grid, indicating a secondary source of power with a similar frequency response is necessary if a single turbine cannot meet the entire demand. Major contributions of this work include exploration of the system time constant as an indicator of turbine dynamic response, evidence a turbine experiences system stall probabilistically, a reduced-complexity field performance characterization methodology, and demonstration of the effectiveness of electromechanical emulators at replicating turbine dynamics.

Download or read book Vertical Axis Hydrokinetic Turbines written by Mabrouk Mosbahi; Ahmed and published by . This book was released on 2021-12-14 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook is a guide to numerical and experimental processes that are used to analyze and improve the efficiency of vertical axis rotors. Chapters present information that is required to optimize the geometrical parameters of rotors or understand how to augment upstream water velocity. The authors of this volume present a numerical model to characterize the water flow around the vertical axis rotors using commercial CFD code in Ansys Fluent®. The software has been used to select adequate parameters and perform computational simulations of spiral Darrieus turbines. The contents of the volume explain the experimental procedure carried out to evaluate the performance of the spiral Darrieus turbine, how to characterize the water flow in the vicinity of the tested turbine and the method to assess the spiral angle influence on the turbine performance parameters. Results for different spiral angles (ranging from 10° to 40°) are presented. This volume is a useful handbook for engineers involved in power plant design and renewable energy sectors who are studying the computational fluid dynamics of vertical axis turbines (such as Darrieus turbines) that are used in hydropower projects. Key features: - 4 chapters that cover the numerical and experimental analysis of vertical axis rotors and hydrokinetic turbines - Simple structured layout for easy reading (methodology, models and results) - Bibliographic study to introduce the reader to the subject - A wide range of parameters included in experiments - A comprehensive appendix of tables for mechanical parameters, statistical models, rotor parameters and geometric details.

Download or read book Design and Experimental Investigation of a High weight flow Low pressure ratio Turbine written by Donald A. Petrash and published by . This book was released on 1959 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Analysis of an Axial Flow Horizontal Axis Marine Hydrokinetic Turbine written by Aarshana Parekh and published by . This book was released on 2019 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tidal energy extraction using marine hydrokinetic devices has become an important area of research in the renewable energy field in recent years because of the highly predictable nature of the tides. Due to its early stage of development, many studies need yet to be done before deployment of these devices at tidal sites. It is essential to have a thorough understanding of the turbine performance and wake properties before determining the array arrangement for tidal farms. In this thesis, flow behavior in the wake of a counter-rotating dual rotor horizontal axis tidal turbine is studied by numerically solving the Reynolds Averaged Navier Stokes (RANS) Equations. The rotational effects of the turbine are modeled using the sliding mesh technique. The realizable k-epsilon model is employed to solve the closure problem. The methodology is validated against experimental data measured in open channel tests conducted at the St. Anthony Falls Laboratory of the University of Minnesota, in collaboration with Sandia National Laboratory, to investigate the turbine efficiency and the physical dynamics of the wake. The transient performance of the turbine is predicted with good accuracy using the sliding mesh model, with some level of disagreement found in predicting the velocity deficit in the flow. The limitations of accurately predicting the turbulent flow properties for the turbine are addressed and the sliding mesh technique is proven to capture effectively the different coherent structures in the wake. The qualitative agreement of the method suggests that this model can be used to explore turbine design and wake characteristics over various parameters in a cost-effective manner. This method can also provide critical parameters needed for designing efficient tidal farms.

Download or read book Small Wind and Hydrokinetic Turbines written by Philip Clausen and published by IET. This book was released on 2021-11-30 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is huge potential for smaller wind turbines to provide clean energy around the world. Small wind turbines come in a variety of designs, and have similarities in principles and technology to small hydrokinetic turbines (SHKTs). SHKTs, in turn, can play an important role in hydropower. Small wind and hydrokinetic systems can even work together, for example, to power farms, communities, campuses, rural as well as remote rural areas, and island regions.

Download or read book Development of Horizontal Axis Hydrokinetic Turbine Using Experimental and Numerical Approaches written by Abdulaziz Mohammed Abutunis and published by . This book was released on 2020 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Hydrokinetic energy conversion systems (HECSs) are emerging as viable solutions for harnessing the kinetic energy in river streams and tidal currents due to their low operating head and flexible mobility. This study is focused on the experimental and numerical aspects of developing an axial HECS for applications with low head ranges and limited operational space. In Part I, blade element momentum (BEM) and neural network (NN) models were developed and coupled to overcome the BEM's inherent convergence issues which hinder the blade design process. The NNs were also used as a multivariate interpolation tool to estimate the blade hydrodynamic characteristics required by the BEM model. The BEM-NN model was able to operate without convergence problems and provide accurate results even at high tip speed ratios. In Part II, an experimental setup was developed and tested in a water tunnel. The effects of flow velocity, pitch angle, number of blades, number of rotors, and duct reducer were investigated. The performance was improved as rotors were added to the system. However, as rotors added, their contribution was less. Significant performance improvement was observed after incorporating a duct reducer. In Part III, a computational fluid dynamics (CFD) simulation was conducted to derive the optimum design criteria for the multi-turbine system. Solidity, blockage, and their interactive effects were studied. The system configuration was altered, then its performance and flow characteristics were investigated. The experimental setup was upgraded to allow for blockage correction. Particle image velocimetry was used to investigate the wake velocity profiles and validate the CFD model. The flow characteristics and their effects on the turbines performance were analyzed"--Abstract, page iv.

Download or read book Performance Analysis of a High Solidity Diffuser Shrouded Vertical Axis Hydrokinetic Turbine Using Computational Fluid Dynamics written by and published by . This book was released on 2014 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling and Simulation of Hydrokinetic Composite Turbine System written by Haifeng Li and published by . This book was released on 2014 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The utilization of kinetic energy from the river is promising as an attractive alternative to other available renewable energy resources. Hydrokinetic turbine systems are advantageous over traditional dam based hydropower systems due to "zero-head" and mobility. The objective of this study is to design and analyze hydrokinetic composite turbine system in operation. Fatigue study and structural optimization of composite turbine blades were conducted. System level performance of the composite hydrokinetic turbine was evaluated. A fully-coupled blade element momentum-finite element method algorithm has been developed to compute the stress response of the turbine blade subjected to hydrodynamic and buoyancy loadings during operation. Loadings on the blade were validated with commercial software simulation results. Reliability-based fatigue life of the designed composite blade was investigated. A particle swarm based structural optimization model was developed to optimize the weight and structural performance of laminated composite hydrokinetic turbine blades. The online iterative optimization process couples the three-dimensional comprehensive finite element model of the blade with real-time particle swarm optimization (PSO). The composite blade after optimization possesses much less weight and better load-carrying capability. Finally, the model developed has been extended to design and evaluate the performance of a three-blade horizontal axis hydrokinetic composite turbine system. Flow behavior around the blade and power/power efficiency of the system was characterized by simulation. Laboratory water tunnel testing was performed and simulation results were validated by experimental findings. The work performed provides a valuable procedure for the design and analysis of hydrokinetic composite turbine systems"--Abstract, page iv.

Download or read book Design Analysis of Performance and Aerodynamic Loading of Non Flexible Horizontal axis Wind Turbines written by Robert E. Wilson and published by . This book was released on 1978 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this report is to develop simplified methods of determining the performance and aerodynamic loading of non -flexible horizontal axis wind turbines. The first chapter is devoted to a general discussion and background of wind turbine aerodynamics. The second chapter covers horizontal axis wind turbine performance in a uniform wind. A calculation scheme is developed and examples are given. The calculation scheme and program listing are given in detail in Appendik A. The third chapter deals with the analysis and behavior of wind turbines subject to yaw, wind shear and tower shadow. The method of analysis used for yaw has been checked with NACA wind tunnel test data for yawed propellers. Calculation procedures and program listings are given in Appendices B and C.

Download or read book Optimization and Computational Fluid Dynamics written by Dominique Thévenin and published by Springer Science & Business Media. This book was released on 2008-01-08 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: The numerical optimization of practical applications has been an issue of major importance for the last 10 years. It allows us to explore reliable non-trivial configurations, differing widely from all known solutions. The purpose of this book is to introduce the state-of-the-art concerning this issue and many complementary applications are presented.

Download or read book Hydrodynamic Optimization Method and Design Code for Stall regulated Hydrokinetic Turbine Rotors written by Danny Sale and published by . This book was released on 2009 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the adaptation of a wind turbine performance code for use in the development of a general use design code and optimization method for stall-regulated horizontal-axis hydrokinetic turbine rotors. This rotor optimization code couples a modern genetic algorithm and blade-element momentum performance code in a user-friendly graphical user interface (GUI) that allows for rapid and intuitive design of optimal stall-regulated rotors. This optimization method calculates the optimal chord, twist, and hydrofoil distributions which maximize the hydrodynamic efficiency and ensure that the rotor produces an ideal power curve and avoids cavitation. Optimizing a rotor for maximum efficiency does not necessarily create a turbine with the lowest cost of energy, but maximizing the efficiency is an excellent criterion to use as a first pass in the design process. To test the capabilities of this optimization method, two conceptual rotors were designed which successfully met the design objectives.

Download or read book Analysis of Hydrokinetic Turbines in Open Channel Flows written by Arshiya Hoseyni Chime and published by . This book was released on 2013 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rivers and irrigation canals are good candidates to produce small-scale hydrokinetic power. Traditionally, gates are used to control water flow in such waterways by dissipating kinetic energy of the flow. This study investigates potential of replacing these gates with Horizontal Axis Hydrokinetic Turbines (HAHT). These machines are designed so that not only power can be extracted but also flow is going to be maintained at the required flow rate. This application increases renewable energy capacity and decreases energy dependency on foreign resources. In this study, theoretical and numerical approaches are used to model HAHT in open channel flows. Theoretical method uses one-dimensional control volume analysis to predict maximum power that an ideal rotor can extract from the flow as useful power and wake mixing at a given Froude number and blockage ratio. This method is then compared to three-dimensional Actuator Disc Model (ADM) developed in commercial Computational Fluid Dynamic (CFD) code ANSYS Fluent. This model uses a porous media to represent HAHT and Reynolds-Average Navier-Stokes (RANS) equations along with Volume of Fluid (VoF) model to solve for flow field and track the free surface. Same computation method is implemented with a more advanced model, Virtual Blade Model (VBM), which uses blade element theory to consider geometry of the blade and operating conditions such as angular velocity and pitching angle. This method is used to optimize the turbine geometry for maximum power and find operating limits to avoid cavitation. Previous literature mostly concentrates on performance of Horizontal Axis Tidal Turbines in channels where blockage ratio is low and consequently free-surface deflection is not a matter of interest. Even in cases where blockage was considered in order to validate flume experiments, velocity deficit of wake region was the main focus. However, this research attempts to fill the gap in literature for better understanding the power extraction of HAHT and subsequent head loss (flow control) in highly blocked flows using three methods mentioned above. In addition, this work attempts to use validated VBM to answer if one-dimensional theory and CFD ADM are capable of predicting power production of HAHTs in highly blocked and low head flows such as irrigation canals.