On the performance of a micro-scale Bach-type turbine as predicted by discrete-vortex simulations (original) (raw)
Energies
Horizontal axis turbines are commonly used for harnessing renewable hydrokinetic energy, contained in marine and river currents. In order to encourage the expansion of electricity generation using micro-hydrokinetic turbines, several design improvements are investigated. Firstly, optimization-based design of rotor blade is used to get as close as possible to the efficiency limit of 59.3% (known as Betz limit), that counts for bare turbine rotors, placed in the free flow. Additional diffuser elements are further added to examine the potential to overcome the theoretical efficiency limit by accelerating water at the axial direction. Various diffuser geometrical configurations are investigated using the computational fluid dynamics (CFD) to obtain insight into hydrodynamics of augmented micro-hydrokinetic turbines. Moreover, the turbines are compared from the energy conversion efficiency point of view. The highest maximum power coefficient increase of 81% is obtained with brimmed (flan...
Characterization of a micro-hydrokinetic turbine in close proximity to the free surface
Ocean Engineering, 2015
Predicting hydrokinetic turbine power generation is difficult due to complex geometry, highly turbulent conditions, and difficulty capturing the transient interface existing between air and water.A threedimensional finite volume solver was used to capture the effects resulting from free surface interaction with the aid of a Volume of Fluid(VOF) multiphase solver.Depths from free surface level to blade tip with corresponding Froude numbers of 0.71, 0.92, 1.04, and 1.31 were modelled specifically to capture the transition from subcritical to supercritical flow conditions.A sharp decrease in performance was observed at the critical Froude number (Fr=1.0).Results at subcritical conditions showed acceptable agreement with previously published single phase results where the turbine is assumed to be operating in aninfinite medium.At subcritical conditions, the propeller-based turbine studied was compared to numerical and experimental results obtained for a traditional marine current turbine (MCT).As the flow became critical, a 32.2% decrease in the power coefficient was predicted and significant wake-free surface interaction was observed.
The Efficiency Comparison of Hydro Turbines for Micro Power Plant from Free Vortex
Energies
In this research paper, the relationship between a crossflow turbine and propeller turbine size changes and the pond size in a free vortex power generation system was investigated. This relationship can be written in the form of a new mathematical equation using the principles of the response surface methodology (RSM) method. This study aimed to compare the efficiency of a crossflow turbine and propeller turbine to enhance a micro power plant from free vortex. The pond size in a micro power plant from free vortex was 1 m in diameter and 0.5 m in height with a 0.2 m outlet drain at the bottom. All turbines were tested at different water flowrates of 0.2, 0.3, 0.4, 0.5, and 0.6 m3/s to identify the rpm, water head, voltage, and electric current to access the waterpower, power output, and overall efficiency. At a 0.02 m3/s water flowrate, the crossflow turbine had greater overall efficiency than the propeller turbine, reaching 9.09% efficiency. From the comparison of the results of the...
Numerical analysis of a shrouded micro-hydrokinetic turbine unit
Journal of Hydraulic Research, 2015
Computational fluid dynamics simulations were conducted for two diffuser designs that were added to a pre-existing horizontal axis hydro-kinetic turbine design. The two diffuser designs investigated in the present study had the area ratio values of 1.36 and 2.01. Each design used a short axial length to satisfy system portability constraints. The turbine-diffuser systems steady-state performance characteristics were assessed numerically. A structured, hexahedral mesh was employed to discretize the equations governing the fluid motion. Turbulent flow structures were captured through the implementation of the k-ω Shear Stress Transport (SST) model. A 39.5% and 55.8% increase in output mechanical power was observed versus the un-augmented turbine performance. As the area ratio increases from 1.36 to 2.01, the total thrust experienced by the unit nearly doubles.
Numerical simulation of 3D flow past a real-life marine hydrokinetic turbine
Advances in Water Resources, 2012
We simulate three-dimensional, turbulent flow past an axial-flow marine hydrokinetic (MHK) turbine mounted on the bed of a rectangular open channel by adapting a computational framework developed for carrying out high-resolution large-eddy simulation (LES) in arbitrarily complex domains involving moving or stationary boundaries. The complex turbine geometry, including the rotor and all stationary components, is handled by employing the curvilinear immersed boundary (CURVIB) method . Velocity boundary conditions near all solid surfaces are reconstructed using a wall model based on solving the simplified boundary layer equations . To demonstrate the capabilities of the model we apply it to simulate the flow past a Gen4 axial flow MHK turbine developed by Verdant Power for the Roosevelt Island Tidal Energy (RITE) project in the East River in New York City, USA. We carry out systematic grid refinement studies, using grids with up to 185 million nodes, for only the turbine rotor placed in an infinite free stream to show that the computed torque converges to a grid insensitive value, which is in good agreement with field measurements. We also carry out LES for the complete turbine configuration, including the pylon, nacelle and rotor, mounted on the bed of a straight rectangular open channel. The computed results illustrate the complexity of the flow and show that the power output of the complete turbine is primarily dependent on the rotor geometry and tip speed ratio, and is not affected by the stationary components of the turbine and the presence of the channel bed. The complete turbine simulation also reveals that the downstream wake of the turbine consists of three main regions: (1) the outer layer with the spiral blade tip vortices rotating in the same direction as the blades; (2) the counter-rotating inner layer surrounded by the spiral tip vortices; and (3) the core layer co-rotating with respect to the tip vortices. This study is the first to report the three-dimensional wake structure of MHK turbines.
2017
This paper presents a combined experimental and Computational Fluid Dynamics (CFD) simulation of Micro wind Turbine with 2.28 meters rotor Diameter is performed using the FLUENT 16.2 WORKBENCH. A Micro Horizontal Axis Three Blade Wind Turbine was designed, developed and tested for power performance on new airfoil AFN2016 Designed. The three blades were fabricated from glass fiber with a rotor swept area of 3.14 sq.m for the 1-meter length of the blade and angle of attack experimentally determined to be 5o.The blade is designed for tip speed ratio (TSR) of 7. The power out measured for wind speed from 3.0m/s to 9.0 m/s. The comparison of the CFD and experimental results on the relationship between the power obtained and the wind speed of the wind turbine at the wind from 3-9 m/s. It can be clearly seen that the experimental data match quite well again with the numerical analysis and they both demonstrated that the power of wind turbine increasing with wind speed increases.
A Review on Micro Hydro Gravitational Vortex Power and Turbine Systems
Electrical power is essential in commercial and social investments like lighting, heating, communications, computers, industrial equipment, transport etc. Therefore hydropower energy is one of the most suitable and efficient source of renewable energy which depends on more than century of experience for this issue. The power capacity and facility are two criteria required for the classification of hydropower plant. The first one consists of five technologies: dammed reservoir, run of river, pumped storage, in stream technology and new technology gravitational vortex. The other one is classified according to power scale is Large, Small, Micro and Pico Hydropower. This paper is focusing on micro hydropower especially gravitational vortex power which increases the sustainability and health of the water as a whole. It presents an overview from both flow and power points of view by discussing the free surface vortex (FSV) and the suitable turbine systems which are used in micro hydropower
Experimental optimization of a free vortex propeller runner for micro hydro application
Experimental Thermal and Fluid Science, 2009
The turbine technology for low head application in the micro hydro range has been vastly neglected despite niche available in scattered regions of valley flows as well as in wastewater canals and other energy recovery schemes, where the available head does not exceed 2 meters. The goal of this study is to develop hydraulically optimized propeller turbines for the micro hydro range with a particular focus on ease of manufacture.
An experimental study of improvement of a micro hydro turbine performance
1999
The thesis includes a literature survey of small hydraulic turbines, incorporating a historical review. The possible role of "micro hydros" in generating power in various parts of the world, and particularly in Iran, is discussed. The theory of turbo machinery, particularly with regard to axial flow turbines, is presented next. This is followed by some details on the design of guide vanes, runner blades and draft tube of axial flow turbines, these components being usually regarded as areas which have major impact on the performance of hydraulic turbines. The next chapter gives the details of the test circuit that was constructed. This could provide water volume flow rates of up to 0.15 m3/s at heads of up 25m. The two dynamometers that were used could adsorb pores to up to 25 kw and 50 kw respectively. An existing micro-turbine, the Agnew turbine, was selected for examination and possible improvement. The first possible improvement was the introduction of guide vanes upstr...
Design and Simulation of a Micro Hydrokinetic Turbine
Conventional hydropower equipment requires a significant vertical head of water to drive turbines, which substantially reduces the number of potential installation sites for a portable, fast-deploying turbine. A potential solution to this lies in hydrokinetic turbines that rely on kinetic pressure to drive the turbine. A preliminary micro hydrokinetic turbine with a 0.5334 m diameter rotor has been designed to meet a goal of generating 500 Watts of continuous power over the widest range of operating conditions possible, while maintaining portability and fast-deploy characteristics. This paper provides insight into the computational models used to evaluate the design, such as Computational Fluid Dynamics to study performance and predict cavitation, as well as a Finite Element Analysis to check the structural integrity of the turbine in preparation for manufacturing. Results of the flow field analysis, cavitation analysis and a static structural analysis are presented.