AERODYNAMIC PROFILES FOR APPLICATIONS IN HORIZONTAL AXIS HYDROKINETIC TURBINES (original) (raw)
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Engineering Journal, 2018
Three twisted blades of a 1 kW prototype hydrokinetic turbine were designed based on the Blade Element Momentum (BEM) theory with a tip speed ratio of 6.25; a water velocity of 1.5 m/s; an angle of attack and pitch angle of 5 and 0 • , respectively; a power coefficient of 0.4382 and a drive train efficiency of 70%. S822 hydrofoil was used to generate the coordinates of the blade cross-section. Experimental investigations and Computational Fluid Dynamics (CFD) simulations were carried out to estimate the performance of the blade design and know the effect of the section pitch angle on the performance of a horizontal-axis hydrokinetic turbine. The obtained results showed that the increase in the section pitch angle enhanced the performance up to a certain value. Further increase in the section pitch angle resulted in a low performance and a reduction of the rotation velocity, which in turn requires a high gearing ratio of the transmission system.
Performance Analysis of Hydrokinetic Turbine Blade Sections
2015
Hydrokinetic turbines are recently developed renewable energy harnessing devices which convert the kinetic energy of rivers, tidal currents and waves into electricity. The blade sections (hydrofoil) of in-stream hydrokinetic energy converters are very important which have a great impact on the turbine performance. Various studies have been conducted on horizontal axis wind turbine blade sections. However the hydrokinetic turbine blade profiles are poorly investigated. The aim of this study is to apply a numerical performance analysis on pre-developed blade sections to be used hydrokinetic turbines. The lift, drag and pressure coefficients of various NACA, NREL and RISØ hydrofoils were studied. The most suitable blade sections were pointed out considering high lift/drag ratio and low cavitation criteria.
Background:The study of the optimization of horizontal axis hydrokinetic turbineperformances using computational fluid dynamics (CFD), creates awareness on the recent development in renewable energy industries and enhanced the output power of the Hydrokinetic power plant. In this work. the effect of TSR and chord length was investigated using CFD approach and. the results shows that power coefficient (C p) depends on TSR and slightly affected by chord length. Materials and Method:A three dimensional CFD analysis performed using ANSYS CFX 15.0 and SolidWorks as Preprocessor to draw the rotor, boundary conditions were created using the pre-processing tool solid-works, Hydrofoil SG-6043 was chosen for the simulation and mesh was created using structured quadrilateral cells around the hydrofoils. The computational domain was assumed to be sufficiently large compared to the chord length to enable larger area of flow visualization around the hydrofoil. A finer mesh was applied on the vicinity of the hydrofoil to obtain better flow characteristics and flow orientation very near to surface. Quadrilateral elements were used to mesh the entire geometry to ensure uniform aspect ratios of cells across the domain. Results: As the rotational speed increases from root to tip of a blade, the flow angle decreases andas solidity increase from 0.084 to 0.127 there was a corresponding increase of C p from 0.112 to 0.284 implying strong influence of solidity on horizontal axis hydrokinetic turbine performances. From analysis the results of the optimization performed shows that a C p value of 0.45 achievable for a variable chord rotor of 1.0m at appropriate combination of turbine parameters. Conclusion: Hydrodynamic analysis and optimization shows that the performance of hydrokinetic turbine can be maximized by choosing the right combination of design variables. Secondly, the three-dimensional results for optimum design suggested a strong dependence of maximum C P on TSR when different turbine geometries are being considered. It was also observed that, Increase in turbine solidity results in increased C P under the entire operating range of TSR studied with maximum C P observed in lower TSR
Journal of Renewable and Sustainable Energy, 2011
The hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkTs) under different turbine geometries and flow conditions is discussed. Hydrokinetic turbines are a class of zero-head hydropower systems which utilize kinetic energy of flowing water to drive a generator. However, such turbines very often suffer from low-efficiency which is primarily due to its operation in a low tip-speed ratio (4) regime. This makes the design of a HAHkT a challenging task. A detailed computational fluid dynamics study was performed using the k-x shear stress transport turbulence model to examine the effect of various parameters like tip-speed ratio, solidity, angle of attack, and number of blades on the performance HAHkTs having power capacities of $12 kW. For this purpose, a three-dimensional numerical model was developed and validated with experimental data. The numerical studies estimate optimum turbine solidity and blade numbers that produce maximum power coefficient at a given tip speed ratio. Simulations were also performed to observe the axial velocity ratios at the turbine rotor downstream for different tip speed ratios which provide quantitative details of energy loss suffered by each turbine at an ambient flow condition. The velocity distribution provides confirmation of the stall-delay phenomenon due to the effect of rotation of the turbine and a further verification of optimum tip speed ratio corresponding to maximum power coefficient obtained from the solidity analysis. V
Development of horizontal axis hydrokinetic turbine using experimental and numerical approaches
2020
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.
Environmental Progress & Sustainable Energy, 2016
The main objective of this paper is to achieve a very high lift rotor to take the maximum advantage of the kinetic energy of a slow velocity water flow, which belongs to a lowland river type. Low speed flux and lack of depth are the main obstacles in hydrokinetic operation. The use of a high lift aerodynamic profile and the gain of the rotor number of blades serve to accomplish the task. This work presents the fluid dynamic design for an axial hydrokinetic turbine rotor, studied in a three-dimensional (3-D) numerical simulation by means of Computational Fluid Dynamics (CFD). The use of CFD techniques avoids some physical model assays. For the hydrokinetic turbine rotor design, first a one-dimensional (1-D) theoretical design was carried out, starting with the selection of a suitable airfoil profile to create the hydrofoil blade. Then, the 3-D rotor geometry was defined and studied 2 carefully by means of CFD, in order to check its hydrodynamic behaviour, i.e., lift and drag, streamline velocities and pressure fields. The CFD results were obtained using an open CFD code (Kratos). Novelty: Despite hydrokinetic energy conversion is not a new technic; the application in a free water stream is becoming popular in the present. Most of the advances in this field involves oceanographic tides, relegating river flow usage to a very few studies. A very small part of these ambit concerns about a riverbed location of the hydrokinetic turbine, working in axial flow mode. Classical 3 bladed rotors in a drag operation enclose the advances in the field. This work aims to present the feasibility study of an 8 bladed hydrokinetic turbine rotor, improved by a high lift hydrodynamic profile.
Numerical analysis on the use of multi-element blades in a horizontal-axis hydrokinetic turbine
Journal of Mechanical Engineering and Sciences, 2020
The blades of a hydrokinetic turbine have a great impact on its performance due to they are the elements responsible for capturing the kinetic energy from water and transform it into rotational mechanical energy. In this work, numerical analyses on the performance of a multi-element blade section were developed. The lift and drag coefficients (CL and CD, respectively) of the hydrofoils with traditional and multi-element configurations were studied. For this purpose, 2D numerical analyses were conducted by using JavaFoil code. S805, S822, Eppler 420, Eppler 421, Eppler 422, Eppler 423, Eppler 857, Wortmann FX 74-CL5-140, Wortmann FX 74-CL5-140 MOD, Douglas/Liebeck LA203A, Selig S1210, Selig S1223 and UI-1720 profiles were tested. The results indicated that the Eppler 420 multi-element hydrofoil provided high efficiency to the turbine. This was attributed to its higher relationship between the maximum CL and CD (CLmax /CD), which was equal to 47.77, compared to that of the Selig S1223...
CFD Simulation of a Horizontal Axis Hydrokinetic Turbine
Renewable Energy and Power Quality Journal
This study presents three-dimensional full transient numerical simulations of a horizontal axis hydrokinetic turbine, HAHT with particular emphasis on the analysis of its hydrodynamic characteristics. Hydrokinetic turbine performance is studied using a time-accurate Reynolds-averaged Navier-Stokes (RANS) commercial solver. A physical transient rotorstator model with a sliding mesh technique is used to capture changes in flow field at a particular time step. A shear stress transport (SST) turbulence model has been employed to model the turbulent features of the flow. The studied rotor has three blades, based on NACA4412 airfoil. Two operation conditions have been considered: shaft parallel to the incoming flow (SP configuration) and shaft inclined an angle around 30 o regarding the main stream (SI configuration). As a result, the decrement of the hydrodynamic performance of the turbine with the inclined axis is quantitatively evaluated regarding that of the parallel axis. Moreover, a preliminary study of the vorticity dynamics in the wake of the inclined rotor is performed
A methodology for the transient behavior of horizontal axis hydrokinetic turbines
Energy Conversion and Management, 2014
In recent years, increasing attention is being given to the study of hydrokinetic turbines for power generation due to the use of clean energy by using renewable sources. This paper aims to present a general methodology for the efficient design of horizontal axis hydrokinetic turbines with variable rotation. The approach uses the Blade Element Method (BEM) for determining the power coefficient of the turbine. The modeling of the hydrokinetic rotor is coupled with the model of the drive line of the system, including the multiplier and the electric generator. Therefore, the modeling of the whole system comprises the hydrodynamic information of the rotor and the characteristics of the inertia of whole system, frictional losses and electromagnetic torque of the generator. The results of numerical simulation are obtained for the rotational speed of the rotor as well as the results of the torque, mechanical and electrical power. Dr. Ingram is a expert in Turbomachinery with a published book (Basic Concepts in Turbomachinery) and has developed a well-recognized code for wind turbine design and analysis using the Blade Element Momentum Theory, that is the base for the submitted paper.
Computational Fluid Dynamic Simulation of Vertical Axis Hydrokinetic Turbines
Computational Fluid Dynamics Simulations [Working Title]
Hydrokinetic turbines are one of the technological alternatives to generate and supply electricity for rural communities isolated from the national electrical grid with almost zero emission. These technologies may appear suitable to convert kinetic energy of canal, river, tidal, or ocean water currents into electricity. Nevertheless, they are in an early stage of development; therefore, studying the hydrokinetic system is an active topic of academic research. In order to improve their efficiencies and understand their performance, several works focusing on both experimental and numerical studies have been reported. For the particular case of flow behavior simulation of hydrokinetic turbines with complex geometries, the use of computational fluids dynamics (CFD) nowadays is still suffering from a high computational cost and time; thus, in the first instance, the analysis of the problem is required for defining the computational domain, the mesh characteristics, and the model of turbulence to be used. In this chapter, CFD analysis of a H-Darrieus vertical axis hydrokinetic turbines is carried out for a rated power output of 0.5 kW at a designed water speed of 1.5 m=s, a tip speed ratio of 1.75, a chord length of 0.33 m, a swept area of 0.636 m 2 , 3 blades, and NACA 0025 hydrofoil profile.