Investigation of the Possibilities to Improve Hydrodynamic Performances of Micro-Hydrokinetic Turbines (original) (raw)
Related papers
Many modifications have been made on conventional hydrokinetic turbines rotor blades to improve the performances. The rotor blade modification in this research paper is a blade combination where the circle-shaped conventional model is combined with the one of a concave elliptical model. Two different blade geometries have been analyzed using a detailed computational Fluid Dynamics approach. The blade design will affect the simplicity of construction and cost of manufacture of turbine rotors. The aim is to analyze the influence of the blade combination towards the performance of hydrokinetic turbine for installation at a selected site. The research includes experimental method using open-type water tunnel of rotor's prototype with 2 different blade models of similar dimensions. The experiment shows, there are influences of the modification of the rotor blade to the performances of the turbine. The optimized blade design improves the performances of the Tip Speed Ratio (TSR) by 78 % while the Coefficient of thrust (CT) is improved by 58.3% at peak co-efficient of performance value of 0.47 for both the blade designs.
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.
Design of a hydrokinetic turbine
WIT Transactions on Ecology and the Environment, 2015
Hydrokinetic turbine power production depends on the interaction between the rotor and water. Therefore, an optimum geometry of the rotor must be designed and constructed to capture the maximum water energy and convert it into a usable energy. The steps involved in the design and numerical simulation of a small horizontal axis hydrokinetic turbine rotor are presented based on the same incompressible flow techniques used for designing wind turbines. Three blades of a 1 Hp (746 W) prototype hydrokinetic turbine were designed for a water velocity of 1.5 m/s with a tip speed ratio of 6.325, an angle of attack of 5 • and 0 • as the pitch angle; in order to obtain the maximum power coefficient of the turbine. This coefficient was 0.4382, near the Betz limit. S822 airfoil was used to generate the coordinates of the blade. CFD simulation was carried out using Ansys CFX to estimate the performance of the blade design. Furthermore, FEM was successfully used for stress calculations on turbine blades under the influence of centrifugal and hydrodynamic loading. The designed hydrokinetic turbine can be used for pico hydro generation in rural communities non-connected to electricity services through the national interconnected electric system, due to its simple structure, and low cost of initial investment. Additionally, it can be locally manufactured, the environmental impact is negligible, since large dams are not involved, and the schemes can be managed and maintained by the consumer.
Numerical characterization of a preliminary portable micro-hydrokinetic turbine rotor design
Renewable Energy
Portable micro-hydrokinetic turbines are designed and characterized using computational fluid dynamics (CFD) simulations. The two equation k–ω shear-stress transport (SST) turbulence model is employed to predict quasi steady flow structures for a wide range of tip-speed ratios. Seven input design parameters selected a priori are used to create preliminary turbine rotor designs by using a hydraulic design methodology. Various blade designs are characterized and compared in terms of torque and thrust over a range of operating conditions. Performance characteristics of two, three, and four blade designs are shown to be similar. The results indicate that a maximum power coefficient of 0.43 with a 73.7% efficiency relative to Betz limit is achieved. The portable hydrokinetic turbines, designed and characterized here, do not require large civil structures, making this technology an attractive alternative to conventional hydropower.
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.
Performance of a hydrokinetic turbine using a theoretical approach
Energy Reports, 2020
Regarding the interest in renewable energies, several sources of energy production have been studied and still under improvement. In this work, we are interested in harnessing marine energy currents exploiting the hydrokinetic turbines. The purpose of this study is to provide a comprehensive assessment of the hydrodynamic loads of a 3-blade horizontal-axis marine turbine using a rotor model adapted to the Moroccan potential. For that, the Blade Element Momentum (BEM) is used to calculate the hydrodynamic loads, to estimate the energetic performance, and to determine the blade optimal parameters for a turbine. In additions, the resulting equations are solved in order to obtain the hydrodynamic loads. For validation, a comparison of pressure coefficients along the chord length was made with the results of the Blade software. The Computations were accomplished for a specific NACA profile. c
Diffuser Optimization for a Micro-Hydrokinetic Turbine
Small, hydrokinetic systems generating between 0.5 and 10 kW of power are potentially capable of portable power generation. A propeller turbine 18 inches in diameter is paired with a flanged diffuser and numerically simulated as a potential portable hydrokinetic system. The diffuser augmented hydrokinetic turbine (DAHkT) is investigated with a response surface optimization method, where geometric parameters of the system are systematically varied to determine their effects on the system power generation and thrust. The simulations are determined using a central composite design of experiments to minimize the number of simulations required to fit a second order regression to the results. Potential optimum designs are determined from the regression model, further verified with simulations, and characterized for their entire operating range.
Transient analysis of micro-hydrokinetic turbines for river applications
Ocean Engineering, 2017
Transient simulations are conducted to characterize a single turbine and multiple turbines in an inline and a staggered array using k-ω shear-stress transport (SST) turbulence model. Performance characteristics predicted by transient analysis at various operating conditions were compared to those predicted by steady-state analysis. Transient results indicated that a power coefficient of 0.43 would be generated at the best efficiency point which corresponds to 1.4% deviations between transient and steady-state solutions for a single unit. Flow separation is observed at the tip speed ratio lower than that at the design point. The relative power of the upstream turbine is obtained to be nearly unity in both inline and staggered arrays. The relative power of the downstream turbine in the staggered array is not influenced by the presence of the upstream turbine and it is the same as that of the upstream turbine. On the other hand, the relative power of the downstream turbine in an inline array is reduced to 0.18 at a downstream separation of 6D t. The massive drop in the power generation by the downstream turbine resulted from the presence of strong wake flow induced by the upstream turbine.
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.
Experimental study of a small-scale axial hydrokinetic turbine with adjustable blade pitch
A small-scale axial hydrokinetic turbine (HKT) with a runner having 3 blades with adjustable pitch and a diameter of 0.2 m was designed and tested to evaluate the optimum relationship between its power coefficient and its blade tip speed ratio (TSR). The design was carried out for a water velocity of 0.8 m/s and was based on the Blade Element Momentum Theory. The turbine was built by 3D printing and tested in a free surface water channel for water velocities between 0.8 and 1.1 m/s at three different blade pitch angles. The speed and torque at the turbine shaft were measured. The results of the experimental tests are encouraging and in good agreement with the literature and show that for harvesting hydrokinetic energy for power generation, fast HKTs with 3 thinner blades are more suitable than slower designs with wider blades, as the former allow a reduction in the size and cost of the electrical generator.