104 research outputs found

    CFD Modelling and Simulation of Water Turbines

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    The design and development of water turbines requires accurate methods for performance prediction. Numerical methods and modelling are becoming increasingly important tools to achieve better designs and more efficient turbines, reducing the time required in physical model testing. This book is focused on applying numerical simulations and models for water turbines to predict tool their performance. In this Special Issue, the different contributions of this book are classified into three state-of-the-art Topics: discussing the modelling of pump-turbines, the simulation of horizontal and vertical axis turbines for hydrokinetic applications and the modelling of hydropower plants. All the contributions to this book demonstrate the importance of the modelling and simulation of water turbines for hydropower energy. This new generation of models and simulations will play a major role in the global energy transition and energy crisis, and, of course, in the mitigation of climate change

    An investigation of sqrt 2 conjecture inspired drag induced vertical axis wind turbine blade

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    Governments and research agencies are providing support and resources to facilitate the growth of renewable energy sector (RES). Today wind turbines (WT) are the prominent form of renewable energy for direct energy harvesting. It is found that traditional Savonius wind turbine (SWT) requires design modification or integration supportive design feature in order to improve the drag attributes and power output performance. Generally conventional WTs are design to operate at high wind speed ranging from 10-15 m/s. This constrains the WT to harvest adequate power at low wind speed condition. Research shows that, design configuration adjustment and optimization has improved the efficiency in Cp. Hence, in this study drag driven WT configuration namely SWT is adapted for the construction of proposed design. The research process flow is segregated into four phases specifying the strategies utilized to carry out the investigation namely bio-hybridization, experimental fluid dynamics, computational fluid dynamics and optimization. The selected bio-elements are reconfigured and altered to fit the design problem and criteria of WT. Since the study involves analyzing and recognizing complex morphologies of bio-elements, computational based framework is utilized for the geometry extraction process namely OpenCV. The proposed drag induced wind turbine (DIWT) is a result of hybridization of two bio-elements namely nautilus spiral configured shell and barnacle marine organism. The aim of primary stage of the design process is to construct the mainframe of the WT blade shape which is extracted from a non-aerodynamic element which is Nautilus shell. The initial design is modelled with barnacles and blade morphology inspired by mathematical conjecture but without endplates. The proposed conjecture and ratio provide an alternative approach in calculating the parametric values of a geometry with regards to √2. It appears that irrational number √2 is fundamental in the creation of circle and spiral. In addition, multiple combinations of blade curvatures is also possible to be constructed with the newly found conjecture, ratio and method. Meanwhile, relative to experimental fluid dynamics procedure the rotational properties of the rotor is investigated using a digital torquemeter coordinated by Arduino. The credibility of the fabricated torquemeter is investigated by comparing the generated moment magnitude with computational numerical model which is executed in CFD. The percentage of error between computational and instrumentational torque is 15.6 %. As for CFD framework for this research, the initially proposed design is comprehensively investigated based on computational numerical model analysis conducted in Ansys CFX. Preliminary investigation indicated that the performance of the initial design is affected by the absence of endplate. The barnacle geometry and its configuration introduce early turbulence and consequently reduces the pressure drag. The reconfiguration of the design is based on the proposed optimization process. The basis of the optimization technique is the Gf which governs the drag attributes of a body relative to flow. If the researcher would like to further investigate reconfigure the existing morphology, it is required to determine the body geometric factor in order to preliminary determine the drag condition. Since Gf 1 (positive volume) minimizes the drag attributes if the orientation of the body is perpendicular the flow. It is found that the implementation of the barnacle geometry aligned perpendicular to flow effectively reduces the pressure attributes. Hence, the technique inspired for the removal of the barnacle geometry. It is found that the blockage corrected peak Cp value of the reconfigured turbine is 0.201 which is 15.4 % of deviation from the uncorrected CFD result. Hence the new corrected data of Cp is utilized to compare with available literature to measure the performance of the proposed design. It can be concluded that the optimized design improved the quality of Cp by 19.2 % in comparison to conventional SWT at λ = 0.67. Meanwhile the author also presented a novel design with shaft and adjoin blade. It is found that the optimized design outperformed both the models by 15.51 % and 6.34 % respectively. Hence, it is evident that blade morphology modification via the proposed conjecture with the presence of endplate improves the performance of the rotor in terms of rotational characteristics and power output

    Analysing the performance of the Archimedes screw turbine within tidal range technologies

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    The UK has an enormous potential for tidal range energy. With the threat of global warming and the decline of the North Sea oil industry, national energy focus is shifting towards this form of renewable energy. Following in the footsteps of the first tidal barrage scheme in La Rance, the 320MW Swansea bay lagoon scheme has recently been given governmental approval (BBC News, 2015). Like existing projects, this lagoon will use the bulb turbine, which has been the standard device for tidal range projects for the last 50 years. One of the reasons these have continued to be chosen is because they are a proven technology, however, since the first project in the 1960’s, turbine technologies have evolved and altered in a plethora of new designs. The aim of this research is to investigate and evaluate these new designs numerically using a marking criteria to determine their suitability. Out of the designs examined the Archimedes Screw proved the most promising for further research, due to the reduced cost, simplistic design and environmentally friendly nature. Through the use of computational fluid dynamics (CFD), a variety of screw turbine designs were evaluated, each investigating a different geometric parameter, which affects the overall performance of the device. The trends found due to altering these values proved that the design of a screw turbine and a screw pump are fundamentally different. The designs, which both increased the volume of flow in each screw bucket and decreased the surface area of the turbine in contact with the flow proved the best. This device in tidal lagoons offers; superior pumping ability; longer operational per tide cycle and can perform well in water with a high silt content (which is expected in tidal lagoons). However, it is necessary to perform further research and model testing to fully analyse the power potential of a full sized device

    Design Optimization of a Portable, Turbine

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    Marine and hydrokinetic (MHK) technology is a growing field that encompasses many different types of turbomachinery that operate on the kinetic energy of water. Micro hydrokinetics are a subset of MHK technology comprised of units designed to produce less than 100 kW of power. A propeller-type hydrokinetic turbine is investigated as a solution for a portable micro-hydrokinetic turbine with the needs of the United States Marine Corps in mind, as well as future commercial applications. This dissertation investigates using a response surface optimization methodology to create optimal turbine blade designs under many operating conditions.The field of hydrokinetics is introduced. The finite volume method is used to solve the Reynolds-Averaged Navier-Stokes equations with the k ω Shear Stress Transport model, for different propeller-type hydrokinetic turbines. The adaptive response surface optimization methodology is introduced as related to hydrokinetic turbines, and is benchmarked with complex algebraic functions.The optimization method is further studied to characterize the size of the experimental design on its ability to find optimum conditions. It was found that a large deviation between experimental design points was preferential. Different propeller hydrokinetic turbines were designed and compared with other forms of turbomachinery. It was found that the rapid simulations usually under predict performance compare to the refined simulations, and for some other designs it drastically over predicted performance. The optimization method was used to optimize a modular pump-turbine, verifying that the optimization work for other hydro turbine designs

    Design of a novel hydrokinetic turbine for ocean current power generation.

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    M. Sc. University of KwaZulu-Natal, Durban 2014.In a world with a growing need for energy, but also a growing need to decrease dependence on fossil fuel energy production, new methods of energy generation are required. The energy which exists in flowing rivers, ocean currents and various other artificial water channels is considered a viable option for a source of renewable power. Water energy harnessing systems are referred to as Hydrokinetic conversion systems. These types of systems are still in the infant stages of development as the main focus of renewable energy in recent years has been solar and wind energy harvesting. Research into ocean currents focusing on the Agulhas Current was conducted to be used as a basis for a Subsea Hydrokinetic system to be implemented off the coast of South Africa. The results obtained from Eskom’s Acoustic Doppler Current Profiler (ADCP) readings depict that the Agulhas current is a more than adequate source of renewable energy. The readings indicate that the Agulhas current varies from 0.3 m/s to 1.2 m/s throughout the year. A proposed Vertical-Axis Hydrokinetic turbine was designed to harness power from the Agulhas current. The design focuses on the selection of blade profile to exploit the lift force which is a result of the interaction with the flow medium. The blade’s helical structure is based on the relationship with the initial attack angle of the blade at a 0° azimuthal position based on the mathematical formulae derived by Gorlov. The study compares a toe-out angle which is not modelled by Gorlov. It was assumed that the turbine’s efficiency would be increased as long as the toe-out angle is within a specified range. Analytical and Computational Fluid Dynamic (CFD) simulations have been conducted on the designed hydrokinetic turbine. The analytical simulations implement double multiple stream tube models which have been used for predecessors of the vertical axis helical turbine. The analytical model was performed in QBlade which is software that implements the double multiple streamtube theory. The CFD model was conducted within Star CCM+TM which included complex vortex interaction and interference with the turbine. Results obtained from the analytical model show that the turbine with a toe-out blade pitch had a slightly lower performance coefficient than the turbine with no blade pitch within the range of 1° to 2°. The results from the CFD simulations and the analytical modelling were in good agreement. The results obtained for the performance of the turbine for toe-out blade pitch from the analytical and CFD modelling were 50% and 52%, respectively. The results are in line with that of simulations and testing of similar type turbines conducted by previous researchers. Comparisons from the effect of toe-out angle on the turbine’s performance proved that the turbine does not experience an increase in efficiency; however, the torque fluctuations decreased for increasing blade pitch. The toe out angle reduced the amount of torque fluctuations on the turbine rotor which provides fewer fluctuations to the coupled generator

    Power generation from tidal currents. Application to Ria de Vigo

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