scholarly journals Quasi-Steady Analytical Model Benchmark of an Impulse Turbine for Wave Energy Extraction

2008 ◽  
Vol 2008 ◽  
pp. 1-12 ◽  
Author(s):  
A. Thakker ◽  
J. Jarvis ◽  
A. Sahed
Keyword(s):  
Wave Energy ◽  
Axial Flow ◽  
Flow Coefficient ◽  
Energy Extraction ◽  
Impulse Turbine ◽  
Guide Vanes ◽  
Aerodynamic Loss ◽  
Turbine Efficiency ◽  
Model Benchmark ◽  
Turbine Design

This work presents a mean line analysis for the prediction of the performance and aerodynamic loss of axial flow impulse turbine wave energy extraction, which can be easily incorporated into the turbine design program. The model is based on the momentum principle and the well-known Euler turbine equation. Predictions of torque, pressure drop, and turbine efficiency showed favorable agreement with experimental results. The variation of the flow incidence and exit angles with the flow coefficient has been reported for the first time in the field of wave energy extraction. Furthermore, an optimum range of upstream guide vanes setting up angle was determined, which optimized the impulse turbine performance prediction under movable guide vanes working condition.

Influence of the Guide Vanes Solidity on the Performance of a Radial Impulse Turbine With Pitch-Controlled Guide Vanes

2011 ◽  
Author(s):  
Bruno Pereiras ◽  
Manabu Takao ◽  
Fernando Garcia ◽  
Francisco Castro
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Essential Role ◽  
Experimental Tests ◽  
Energy Extraction ◽  
Ocean Energy ◽  
Impulse Turbine ◽  
Guide Vanes ◽  
Turbine Efficiency ◽  
Turbine Design

One of the most developed technologies in ocean energy is the OWC concept. In this kind of device there is a turbine which plays an essential role, it is one of the factors which determine the efficiency of the system because of its own efficiency and its coupling with the chamber. One of the main characteristics in a turbine for OWC purposes, especially impulse turbines, is to use Guide vanes to optimize the energy extraction. However, they also are the largest source of losses. Improving the Guide vanes performance could reduce the pressure drop and, thus, the efficiency increases and the damping becomes smaller. In this paper the solidity of the guide vanes is analyzed to determine the optimum one. The study has been conducted on a radial impulse turbine with pitch-controlled guide vanes to minimize the incidence losses and, therefore, analyze the effect of the solidity. Experimental tests were carried out to validate a numerical model created in FLUENT®. The numerical model has been used to analyze the same turbine design but with different solidities of the guide vanes. The results have been conclusive: there is an optimal solidity for the guide vanes, which maximize the turbine efficiency by means of improving the guide vanes performance. Moreover, it has been seen that the optimum solidity is different for the inner and outer guide vanes.

scholarly journals 3-D CFD analysis on effect of hub-to-tip ratio on performance of impulse turbine for wave energy conversion

2007 ◽  
Vol 11 (4) ◽  
pp. 157-170 ◽  
Author(s):  
Ajit Thakker ◽  
Mohammed Elhemry
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Energy Conversion ◽  
Wave Energy ◽  
Flow Coefficient ◽  
Dynamics Analysis ◽  
Wave Energy Conversion ◽  
Impulse Turbine ◽  
Guide Vanes ◽  
Computational Fluid Dynamics Analysis

This paper deals with the computational fluid dynamics analysis on effect of hub-to-tip ratio on performance of 0.6 m impulse turbine for wave energy conversion. Experiments have been conducted on the 0.6 m impulse turbine with 0.6 hub-to-tip ratio to validate the present computational fluid dynamics method and to analyze the aerodynamics in rotor and guide vanes, which demonstrates the necessity to improve the blade and guide vanes shape. Computational fluid dynamics analysis has been made on impulse turbine with different hub-to-tip ratio for various flow coefficients. The present computational fluid dynamics model can predict the experimental values with reasonable degree of accuracy. It also showed that the downstream guide vanes make considerable total pressure drop thus reducing the performance of the turbine. The computational fluid dynamics results showed that at the designed flow coefficient of 1.0 the turbine with 0.5 hub-to-tip ratio has better performance compared to 0.55 and 0.6 hub-to-tip ratio turbine.

scholarly journals Comparison of Some Analytical and Experimental Correlations of Axial-Flow Turbine Efficiency

1967 ◽  
Author(s):  
Charles A. Amann ◽  
David C. Sheridan
Keyword(s):  
Axial Flow ◽  
Flow Coefficient ◽  
Preliminary Design ◽  
Relative Temperature ◽  
Turbine Efficiency ◽  
Factors Influencing ◽  
Design Charts ◽  
Two Factors ◽  
Turbine Design ◽  
Selection Of

The first phase of the axial-flow turbine design problem involves selection of a velocity diagram. This choice exerts an important influence on turbine efficiency. Design charts relating turbine efficiency to the velocity diagram, through a work coefficient and a flow coefficient, are therefore useful in preliminary design. In this study such design charts are constructed using two established analytical methods. The results are compared with a published correlation based on experimental data. Simple constructional methods are indicated whereby these charts can be used to obtain preliminary estimates of rotor blade stress and relative temperature, two factors influencing blade life.

Unsteady Flow Analysis of the Vertical Axis Cross-Flow Wind Turbine

2006 ◽  
Author(s):  
E. Ejiri ◽  
S. Yabe ◽  
S. Hase ◽  
M. Ogiwara
Keyword(s):  
Wind Turbine ◽  
Flow Analysis ◽  
Cross Flow ◽  
Vertical Axis ◽  
Guide Vanes ◽  
Turbine Efficiency ◽  
Turbine Runner ◽  
Entire Flow ◽  
Improved Design ◽  
Turbine Design

Flow through the vertical axis cross-flow wind turbine was analyzed using computational fluid dynamics (CFD) to clarify current aerodynamic issues and to propose an improved design configuration for achieving better performance. The computed torque coefficients and power coefficients of a reference cross-flow wind turbine runner were compared with the experimental results. Flow around each blade of the turbine runner was then investigated based on the computed flow results. As a countermeasure to the issues found, a new wind turbine design was devised which has two guide vanes point-symmetrically arranged outside the turbine runner. It was experimentally shown that this improved design with the guide vanes increased turbine efficiency. However, performance predictions by CFD lack sufficient accuracy in the case of the turbine runner with the guide vanes, where complexity and unsteadiness prevail over the entire flow fields.

Impulse turbine with 3D guide vanes for wave energy conversion

2006 ◽  
Vol 15 (1) ◽  
pp. 27-30 ◽  
Author(s):  
Manabu Takao ◽  
Toshiaki Setoguchi ◽  
Kenji Kaneko ◽  
Shuichi Nagata
Keyword(s):  
Energy Conversion ◽  
Wave Energy ◽  
Wave Energy Conversion ◽  
Impulse Turbine ◽  
Guide Vanes

Hydraulic turbine efficiency

2001 ◽  
Vol 28 (2) ◽  
pp. 238-253 ◽  
Author(s):  
J L Gordon
Keyword(s):  
Root Mean Square ◽  
Axial Flow ◽  
Hydraulic Turbine ◽  
Relative Increase ◽  
Energy Output ◽  
Mean Square ◽  
Peak Efficiency ◽  
Impulse Turbine ◽  
Turbine Efficiency ◽  
Hydraulic Turbines

A set of empirical equations has been developed which defines the peak efficiency and shape of the efficiency curve for hydraulic turbines as a function of the commissioning date for the unit, rated head, rated flow, runner speed, and runner throat or impulse turbine jet diameter. The equations are based on an analysis of peak efficiency data from 56 Francis, 33 axial-flow, and eight impulse runners dating from 1908 to the present, with runner diameters ranging from just under 0.6 m to almost 9.5 m. The metric specific speeds (nq) ranged from 5.3 to 294. The root mean square error of the calculated peak efficiency for Francis and axial-flow runners was found to be 0.65%. The shape of the efficiency curves was derived from eight Francis, five Kaplan, three propeller, and four impulse turbines. Charts showing the relationship between calculated and actual efficiency curves for these 20 runners are provided. A good match between calculated and measured or guaranteed efficiency was obtained. The equations were also used to determine the relative increase in peak efficiency for new reaction runners installed in existing casings at 22 powerplants, with a root mean square accuracy of 1.0%. The equations can be used to (i) develop efficiency curves for new and old runners; (ii) compare the energy output of alternative types of turbines, where this choice is available; and (iii) calculate the approximate incremental energy benefit from installing a new runner in an existing reaction turbine casing, or onto the shaft of an impulse unit.Key words: hydraulic turbines, turbine renovation, turbine efficiency.

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