Wells Turbines With 3-Dimensional Blades: The Performance Under Unsteady Flow Conditions

2015 ◽  
Author(s):  
Manabu Takao ◽  
Katsuya Takasaki ◽  
Tomohiro Tsunematsu ◽  
Miah Md. Ashraful Alam ◽  
Toshiaki Setoguchi
Keyword(s):  
Unsteady Flow ◽  
Flow Separation ◽  
Blade Profile ◽  
Wave Energy Conversion ◽  
Flow Conditions ◽  
Suction Surface ◽  
Wells Turbine ◽  
3 Dimensional ◽  
Profile Changes ◽  
The Mean

The effect of the 3-dimentional (3D) blade on the turbine characteristics of Wells turbines for wave energy conversion has been investigated numerically by a quasi-steady analysis under unsteady flow conditions in this study in order to improve the peak mean efficiency characteristics. The aim of use of the 3D blade is to prevent flow separation on the suction surface near the tip. The chord length is constant in the radius and the blade profile changes gradually from the mean radius to the tip. The proposed blade profiles in the study are NACA0015 from the hub to mean radius and NACA0025 at the tip. The performance of the Wells turbine with 3D blades has been compared with those of the original Wells turbine, i.e., the turbine with 2-dimentional blades. As a result, it was concluded that although the peak mean efficiency of a Wells turbine can be improved by the use of the proposed 3D blade, its blade does not overcome the stall characteristic.

scholarly journals Effect of Blade Profile on the Performance of Wells Turbine under Unidirectional Sinusoidal and Real Sea Flow Conditions

2007 ◽  
Vol 2007 ◽  
pp. 1-9 ◽  
Author(s):  
A. Thakker ◽  
R. Abdulhadi
Keyword(s):  
Unsteady Flow ◽  
Numerical Results ◽  
Blade Profile ◽  
Flow Conditions ◽  
Wells Turbine ◽  
Hysteretic Characteristics ◽  
The One ◽  
Good Agreement

This paper presents the effect of blade profile and rotor solidity on the performance of Wells turbine operating under unidirectional unsteady flow conditions. In the study, four kinds of blade profile were selected, that is, NACA0020, NACA0015, CA9, and HSIM 15-262123-1576. The experiments have been carried out for two solidities,σ= 0.48 andσ= 0.64, under sinusoidal and irregular unsteady flow conditions based on Irish waves (site2). As a result, it was found that the preferable rotor geometry is the one with blade profile of CA9 with solidityσ= 0.64. In addition, the effect of blade profile and rotor solidity on hysteretic characteristics of the turbine has been clarified experimentally and it was found to be in good agreement qualitatively when compared to numerical results (Setoguchi et al. (2003)).

The Estimation of Discharge in an Experimental Open Channel

2014 ◽  
Vol 905 ◽  
pp. 369-373
Author(s):  
Choo Tai Ho ◽  
Yoon Hyeon Cheol ◽  
Yun Gwan Seon ◽  
Noh Hyun Suk ◽  
Bae Chang Yeon
Keyword(s):  
Unsteady Flow ◽  
River Discharge ◽  
Open Channel ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Velocity Equation ◽  
The Mean ◽  
Loop Form

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

Wells Turbine With Variable Blade Profile for Wave Energy Conversion

2018 ◽  
Author(s):  
Celia Miguel González ◽  
Ginés Rodríguez Fuertes ◽  
Manuel García Díaz ◽  
Bruno Pereiras García ◽  
Francisco Castro ◽  
...  
Keyword(s):  
Rotation Speed ◽  
Incidence Angle ◽  
Main Flow ◽  
Performance Curve ◽  
Oscillating Water Column ◽  
Blade Profile ◽  
Wave Energy Conversion ◽  
Wells Turbine ◽  
Sharp Drop ◽  
Ansys Fluent

It is well known among the researchers involved in the field of turbines for Oscillating Water Column systems (OWC) that the main problem for Wells turbines is the stall, which appears when the main flow incidence angle exceeds certain value and leads to a sharp drop in the efficiency. It also causes problems during the starting, driving the turbine to not reach the designing rotation speed. Delaying the stall apparition is the key to improve the performance of the Wells turbine. is necessary to delay the flow separation at the trailing edge because it is the reason which leads to the sharp efficiency drop at the stall point. One of the solutions proposed by researchers in this field is using a variable blade profile instead of the traditional ones, built using constant chord and profile from hub to tip. This work tries to dig deeper in this line by analysing a blade with variable chord and shape among the blade span. The work has been developed numerically by using commercial software ANSYS FLUENT®. A CFD code was created in order to obtain the performance curve of the turbine proposed to be compared with those assumed as reference, which were taken from the bibliography and also used to validate the numerical model. The results have shown that an improvement has been achieved. It confirms that using a variable blade profile is a suitable solution to delay the stall apparition.

CFD Analysis of Stall in a Wells Turbine

2018 ◽  
Author(s):  
Kellis Kincaid ◽  
David W. MacPhee
Keyword(s):  
Source Code ◽  
Turbulence Models ◽  
Ocean Waves ◽  
Cfd Analysis ◽  
Oscillating Water Column ◽  
Blade Profile ◽  
Flow Conditions ◽  
Wells Turbine ◽  
Sst Model ◽  
Blade Shape

The Wells turbine is a self-rectifying device that employs a symmetrical blade profile, and is often used in conjunction with an oscillating water column to extract energy from ocean waves. The effects of solidity, angle of attack, blade shape and many other parameters have been widely studied both numerically and experimentally. To date, several 3-D numerical simulations have been performed using commercial software, mostly with steady flow conditions and employing various two-equation turbulence models. In this paper, the open source code Open-FOAM is used to numerically study the performance characteristics of a Wells turbine using a two-equation turbulence model, namely the Menter SST model, in conjunction with a transient fluid solver.

Mechanism of Hysteretic Characteristics of Wells Turbine for Wave Power Conversion

2003 ◽  
Vol 125 (2) ◽  
pp. 302-307 ◽  
Author(s):  
Y. Kinoue ◽  
T. Setoguchi ◽  
T. H. Kim ◽  
K. Kaneko ◽  
M. Inoue
Keyword(s):  
Flow Separation ◽  
Power Conversion ◽  
Hysteretic Behavior ◽  
Dynamic Stall ◽  
Wave Power ◽  
Suction Surface ◽  
Wells Turbine ◽  
Flow Process ◽  
Wave Power Conversion ◽  
Hysteretic Characteristics

A Wells turbine for wave power conversion has hysteretic characteristics in a reciprocating flow. The counterclockwise hysteretic loop of the Wells turbine is opposite to the clockwise one of the well-known dynamic stall of an airfoil. In this paper, the mechanism of the hysteretic behavior was elucidated by an unsteady three-dimensional Navier-Stokes numerical simulation. It was found that the hysteretic behavior was associated with a streamwise vortical flow appearing near the blade suction surface. In the accelerating process of axial flow velocity, the vortex is intensified to enlarge the flow separation area on the blade suction surface. In the decelerating flow process, the flow separation area is reduced because of the weakened vortex. Therefore, the aerodynamic performance in the accelerating flow process is lower than in the decelerating flow process, unlike the dynamic stall. Based on the vortex theorem, the mechanism to vary the intensity of the vortex can be explained by the trailing vortices associated with the change in the blade circulation.

Numerical Study on End-Wall Flow in Highly Loaded Supercritical Compressor Cascades

2009 ◽  
Author(s):  
Bin Jiang ◽  
Songtao Wang ◽  
Guotai Feng ◽  
Zhongqi Wang
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Numerical Study ◽  
Thickness Distribution ◽  
Flow Conditions ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Flow Phenomena ◽  
Wall Flow ◽  
End Wall

This paper presents a numerical study on three-dimensional flow phenomena near the endwall of a linear high-turning compressor cascade at supercritical flow conditions. The compressor cascade with 60° camber angle was designed at a higher supercritical speed (M1>0.9) by optimum method based on the baseline which aimed at improving the flow near the stator hub of small transonic fans. The camber line and thickness distribution curves of the baseline are formed by quadratic polynomials and double cubic curves respectively. The stack line and the thickness distribution near the end-wall were chosen as optimization variables to approach the objective function of total pressure loss coefficient, since they are the two main geometry parameters which can influence end-wall flow obviously. The analysis in current paper focuses on comparing the flow phenomena near the end-wall of baseline cascade with that of optimized one. Numerical simulation results are presented to show the loss reduction from the baseline to the optimized cascade near end-wall. The boundary-layer development on the suction surface, flow separation structure, shockwave and local supersonic area on the suction surface near the end-wall are analyzed in detail. The optimized cascade has a stronger shockwave near the leading edge. It was found that the radial flow of the boundary-layer caused by the optimization of stack line is the key factor influencing the aerodynamics loss near the end-wall at supercritical condition which also plays an important part in second-flow and flow separation in the corner. An understanding of the low-loss pattern of the end-wall flow and the flow filed structure for high-turning compressor at higher supercritical flow conditions then is summarized at the end of this paper.

Measurements Concerning the Influence of Surface Roughness and Profile Changes on the Performance of Gas Turbines

1972 ◽  
Vol 94 (3) ◽  
pp. 207-213 ◽  
Author(s):  
K. Bammert ◽  
H. Sandstede
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Gas Turbines ◽  
Performance Characteristics ◽  
Blade Profile ◽  
Efficiency Change ◽  
Flow Conditions ◽  
Air Turbine ◽  
Profile Changes

During operation the blading of turbines undergoes certain changes. Corrosion, erosion, and contamination cause deterioration of the surface quality and blade profile changes. As a result, the performance characteristics of the turbine, especially the efficiency, change during operation. Through measurements on a four-stage air turbine with artificially roughened blade surfaces and thinned and thickened profiles which simulate the effects of corrosion and pollution respectively, it has been possible to ascertain the influence of these profile changes on the flow conditions in the turbine. This paper shows the measuring results which are representative of the effects of surface roughness and profile changes.

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