Design and performance optimization of a very low head turbine with high pitch angle based on two-dimensional optimization (original) (raw)
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Design and performance of very low head water turbines using a surface vorticity model algorithm
International Journal of Power Electronics and Drive Systems (IJPEDS), 2022
This study explores the numerical optimization of water turbine runner profile performance using a surface vorticity model algorithm. The turbine is designed on a laboratory scale and operates at a net head of 0.09 m, 400 rpm, and a water flow rate of 0.003 m 3 /s. The initial design of the turbine runner was optimized to minimize losses in the hydrofoil. The optimization algorithm is coded in MATLAB software to obtain the optimal stagger angle that will be used in the water turbine design. Furthermore, design validation was performed using computational fluid dynamics analysis ANSYS CFX to determine the water turbine performance. The settings used in ANSYS CFX include the reference pressure of 1 atm, turbulence model shear stress transport, and inlet boundary conditions using total pressure and static pressure outlet boundary conditions. The computational fluid dynamics analysis reveals that by optimizing the design, the efficiency of the water turbine increases by approximately 2.6%. The surface vorticity model algorithm can be applied to optimize the design of the water turbine runner.
Hydrodynamic and performance of low power turbines: conception, modelling and experimental tests
2010
The present work comprises a research about hydraulic machines with the aim of optimization and the selection of adequate turbines of low power for exploitation of an available energy still unexplored in water supply systems based on analyses of 3D hydrodynamic flows and on characteristic curves which lead to the best efficiency point. The analysis is carried out based on non-dimensional parameters (i.e., discharge, head, efficiency, runner speed and mechanical power) in order to be possible comparisons. Mathematical models based on the physical principles, associated to the development of volumetric and rotordynamic machines, are developed. New turbines are suggested, which are based on similar theory among turbo machines based on applications in hydraulic systems with guarantee discharge and available head. The hydrodynamic fluid mechanical analysis requires the use of complex advanced models (CFD) which apply the equations of Navier-Stokes by using mathematical models of conservation laws, for the study of the turbulent flow behaviour. To determine the correlation between the flow velocity and pressure fields, the k-ε model, is used in this research. Many turbines are evaluated (i.e., positive displacement (PD), pump as turbine (PAT), propeller with volute at inlet, four and five blades tubular propellers) and sensitivity analyses, to the best configurations, as well as comparisons between performance curves and experimental tests. Results are presented with the appropriate range variation for each turbine type and application.
Design Optimization of Axial Hydraulic Turbine for Very Low Head Application
Energy Procedia, 2015
Studies are conducted on axial hydraulic turbine for very low head application which operates on low speed. Design optimization is generated by optimizing the blade airfoil and blade cascade during development of the turbine blades. Blade airfoil is optimized to obtain optimum value of ratio of Lift coefficient Cl and Drag coefficient Cd, in the range of turbine operation by utilizing of XFOIL that controlled via MATLAB. These airfoils are used to develop the blade cascade. To increase the benefits of fluid flow passing through the turbine blades, the analysis and optimization of the blade cascade is conducted. Vortex panel method is used to analyze the fluid flow inside cascade to gain the maximum of the lift force, in order to optimize the potential power of the fluid that can be utilized by the turbine rotor. The cascade optimization is including arrangement of the incidence angle of the cascade to reduce cascade losses and blade loading by applying the concept of shock-free inflow. Numerical analyses are conducted to determine the performance of the designed turbine with the commercial CFD. The results of numerical simulations show that the turbine can be operated at a maximum efficiency of 91% at various ranges of flow rates.
Journal of Applied Fluid Mechanics
This research study was aimed to develop a new concept design of a very low head (VLH) turbine using advanced optimization methodologies. A potentially local site was chosen for the turbine and based on its local conditions, such as the water head level of <2 meters and the flow rate of <5 m 3 /s. The study focused on the optimization of the turbine blade and guide vane profiles, because of their major impacts on the efficiency of the VLH axial flow turbine. The fluid flow simulation was firstly conducted for the axial turbine, followed by applying the regression analysis concept to develop a turbine mathematical model where the leading-and trailing-edge angles of the guide vanes and the turbine blades were related to the efficiency, total head and flow rate. The genetic algorithms (GA) with multi-objective function was also used to locate the optimal blade angles. Thereafter, the refined design was re-simulated. Following this procedure the turbine efficiency was improved from 82.59% to 83.96% at a flow rate of 4.2 m 3 /s and total head of 2 meters.
Improved Hydrodynamic Efficiency of Kaplan Hydro Turbine through Varying Blade Number and Length
Kaplan hydro turbines are adjustable propeller blade turbines that are used in conventional hydroelectric power systems for the generation of electric power. Their mechanical efficiency based on their flexible and wide operating range of flow rates and head depends much on the runner blades and the alignments of the wicket gates. However, design modification of the geometry of the runner blade can be made for the improvement of mechanical efficiency. Computational Fluid dynamics simulation was employed to investigate the improved features of two hypothetical model turbine blades. SolidWorks® software was used for modeling the two categories of the turbine, named model A and model B Kaplan turbines. Model A has a short blade length of 130 mm twisted at an angle of 300, and its blade was varied from 2 to 6 blades. Model B has a longer blade length of 150 mm twisted at an angle of 300, and its blade was varied from 2 to 6 blades. The governing equations, which include continuity and momentum, were discretized using the Finite Volume method. The result shows that an increase in blade total surface area, as a result of an increase in blade length or blade number, increases the power output of the Kaplan hydro turbine.
Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. Therefore, a cross-flow hydraulic turbine is proposed for small hydropower in this study because the turbine has relatively simple structure and high possibility of applying to small hydropower. The purpose of this study is to investigate the effect of the turbine's structural configuration on the performance and internal flow characteristics of the cross-flow turbine model using CFD analysis. The results show that nozzle shape, runner blade angle and runner blade number are closely related to the performance and internal flow of the turbine. Moreover, air layer in the turbine runner plays very important roles of improving the turbine performance.
Optimization study on an ultra-low head bulb hydro turbine
Procceedings of the 24th ABCM International Congress of Mechanical Engineering, 2017
The increase of efficiency of a turbomachine requires a behavior analysis of the flow on its hydromechanical components, in a global way. For a proposal of modification in the profile of the components on a conceptual machine, aiming its optimization, it is necessary to survey into the reason of the possible shortcomings and, finally, to present arguments for their optimization. The use of Computational Fluid Dynamics (CFD) tools are widely used in these researches. Consolidated axial turbines, in general, presents very significant efficiencies, however, machines that operate under special conditions, such as turbines for ultra-low heads condition (0.5 meters to 5.0 meters), are still under development, opening space for research on performance improvements. This work presents an analysis based on the results obtained by computational study through CFD, in order to evaluate an ultra-low head turbine model, proposing the optimization of its performance. The analysis discussed in this paper suggested the exclusion of the original draft tube system, in order to verify the behavior of the fluid flow. This modification resulted in a slight improvement of the efficiency.
Numerical analysis and performance enhancement of a cross-flow hydro turbine
Renewable Energy, 2015
Exploitation of small hydropower sources requires the use of small turbines that combine efficiency and economy which can conveniently cater the power needs of rural and small communities. Cross-flow turbines are used widely in such micro hydropower plants due to their simple design, easier maintenance, low initial investment and modest efficiency. Also, because of their suitability under low heads, their efficient operation under a wide range of flow variations and ease of fabrication, cross-flow turbines have been extensively employed. The primary objective of this study is to numerically analyze the characteristics and the fluid flow in a cross-flow hydro turbine and to optimize its performance by geometrically modifying the several parameters. During the process, a base model was chosen, the design was modified simultaneously by varying the nozzle shape, changing the guide vane angle, varying the number of runner blades and simulations were carried out individually. Two phase (air & water at 25 C), steady state with SST turbulence model was selected in the commercial CFD code ANSYS CFX 13.0 for the numerical simulation. The design parameters included 10 m head, 0.1 m 3 /s flow rate and 642 rpm rotational speed. The results obtained showed that the best efficiency obtained from the base nozzle was 63.67% which was geometrically modified that improved the turbine performance and the efficiency reached 76.60% (increase by 12.93%). Velocity distribution, pressure contours, output torque within the flow domain were also characterized. It was observed that the re-circulating flow region was reduced and also its pattern was varied.