Design and Pitch Angle Optimisation of Horizontal Axis Hydrokinetic Turbine with Constant Tip Speed Ratio

Abstract In recent times, the application of small-scale horizontal axis wind turbines (SHAWTs) has drawn interest in certain areas where the energy demand is minimal. These turbines, operating mostly at low Reynolds number (Re) and low tip speed ratio (λ) applications, can be used as stand-alone systems. The present study aims at the design, development, and testing of a series of SHAWT models. On the basis of aerodynamic characteristics, four SHAWT models viz., M1, M2, M3, and M4 composed of E216, SG6043, NACA63415, and NACA0012 airfoils, respectively have been developed. Initially, the rotors are designed through blade element momentum theory (BEMT), and their power coefficient have been evaluated. Thence, the developed rotors are tested in a low-speed wind tunnel to find their rotational frequency, power and power coefficient at design and off-design conditions. From BEMT analysis, M1 shows a maximum power coefficient (Cpmax) of 0.37 at λ = 2.5. The subsequent wind tunnel tests on M1, M2, M3, and M4 at 9 m/s show the Cpmax values to be 0.34, 0.30, 0.28, and 0.156, respectively. Thus, from the experiments, the M1 rotor is found to be favourable than the other three rotors, and its Cpmax value is found to be about 92% of BEMT prediction. Further, the effect of pitch angle (θp) on Cp of the model rotors is also examined, where M1 is found to produce a satisfactory performance within ±5° from the design pitch angle (θp, design).

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Blade pitch angle and tip speed ratio control schemes for constant power generation of WECS

2016 IEEE 1st International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES) ◽

10.1109/icpeices.2016.7853498 ◽

2016 ◽

Author(s):

Deeksha Bansal ◽

Kamlesh Pandey

Keyword(s):

Power Generation ◽

Pitch Angle ◽

Speed Ratio ◽

Constant Power ◽

Tip Speed Ratio ◽

Control Schemes ◽

Blade Pitch Angle

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Numerical simulation and experimental study of blade pitch effect on Darrieus straight-bladed wind turbine with high solidity: A case study under realistic conditions

10.21203/rs.3.rs-17911/v1 ◽

2020 ◽

Author(s):

Milad Babadi Soultanzadeh ◽

Alireza Moradi

Keyword(s):

Wind Turbine ◽

Numerical Method ◽

Pitch Angle ◽

Numerical Results ◽

Power Coefficient ◽

Speed Ratio ◽

Regulation System ◽

Lower Velocity ◽

Realistic Condition ◽

Tip Speed Ratio

Abstract Numerical and experimental studies were performed to examined the influence of pitch angle on the aerodynamic performance of a small Darrieus straight blade vertical axis wind turbine with high solidity and pitch regulation system under a realistic condition. By comparing experimental and numerical results, numerical results were validated. The power coefficient was measured and calculated at different tip speed ratios and for two pitch angles 0 and 5. The results revealed that 5 degrees increase in the pitch angle led to 25% elevation in the maximum value of the power coefficient (performance coefficient). Also, the numerical results showed higher accuracy at lower tip speed ratios for both pitch angles. After numerical method validation, numerical method employed to calculate the coefficient of performance and coefficient of torque function of Azimuth position as well as the flow field in the rotor affected zone and lateral distance. According to the numerical results, vorticity generation increased by the rise in the pitch angle at a constant tip speed ratio; the maximum performance coefficient occurred at a lower tip speed ratio with elevation in the pitch angle; finally, the increment in the pitch angle led to lower velocity profile in lateral distances of the rotor.

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Wake Expansion and the Finite Blade Functions for Horizontal-Axis Wind Turbines

Energies ◽

10.3390/en14227653 ◽

2021 ◽

Vol 14 (22) ◽

pp. 7653

Author(s):

David Wood

Keyword(s):

Radial Velocity ◽

Wind Turbines ◽

Loss Factor ◽

Axial Direction ◽

Horizontal Axis ◽

Speed Ratio ◽

Tip Speed Ratio ◽

Constant Pitch ◽

Horizontal Axis Wind Turbines ◽

Blade Element

This paper considers the effect of wake expansion on the finite blade functions in blade element/momentum theory for horizontal-axis wind turbines. For any velocity component, the function is the ratio of the streamtube average to that at the blade elements. In most cases, the functions are set by the trailing vorticity only and Prandtl’s tip loss factor can be a reasonable approximation to the axial and circumferential functions at sufficiently high tip speed ratio. Nevertheless, important cases like coned or swept rotors or shrouded turbines involve more complex blade functions than provided by the tip loss factor or its recent modifications. Even in the presence of significant wake expansion, the functions derived from the exact solution for the flow due to constant pitch and radius helical vortices provide accurate estimates for the axial and circumferential blade functions. Modifying the vortex pitch in response to the expansion improves the accuracy of the latter. The modified functions are more accurate than the tip loss factor for the test cases at high tip speed ratio that are studied here. The radial velocity is important for expanding flow as it has the magnitude of the induced axial velocity near the edge of the rotor. It is shown that the resulting angle of the flow to the axial direction is small even with significant expansion, as long is the tip speed ratio is high. This means that blade element theory does not have account for the effective blade sweep due to the radial velocity. Further, the circumferential variation of the radial velocity is lower than of the other components.

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Some effects of flow expansion on the aerodynamics of horizontal-axis wind turbines

10.5194/wes-2021-52 ◽

2021 ◽

Author(s):

David Wood ◽

Eric Limacher

Keyword(s):

Axial Velocity ◽

Momentum Equation ◽

Horizontal Axis ◽

Speed Ratio ◽

Axial Component ◽

Horizontal Axis Wind Turbine ◽

Tip Vortices ◽

Tip Speed Ratio ◽

Constant Pitch ◽

Far Wake

Abstract. Upwind of an energy-extracting horizontal-axis wind turbine, the flow expands as it approaches the rotor, and the expansion continues in the vorticity-bearing wake behind the rotor. The upwind expansion has long been known to influence the axial momentum equation through the axial component of the pressure, although the extent of the influence has not been quantified. Starting with the impulse analysis of Limacher & Wood (2020), but making no further use of impulse techniques, we demonstrate that the expansion redistributes momentum from the external flow to the wake and derive its exact expression when the rotor is circumferentially uniform. This expression, which depends on the radial velocity and the axial induction factor, is added to the thrust equation containing the pressure on the back of the disk. Removing the pressure to obtain a practically useful equation shows the axial induction in the far-wake is twice the value at the rotor only at high tip speed ratio and only if the relationship between vortex pitch and axial induction in non-expanding flow carries over to the expanding case. At high tip speed ratio, we assume that the expanding wake approaches the "Joukowsky'' model of a hub vortex on the axis of rotation and tip vortices originating from each blade. The additional assumption that the helical tip vortices have constant pitch, allows a semi-analytic treatment of their effect on the rotor flow. Expansion modifies the relation between the pitch and induced axial velocity so that the far-wake area and induction are significantly less than twice the values at the rotor. There is a moderate decrease – about 6 % – in the power production and a similar size error occurs in the familiar axial momentum equation involving the axial velocity.

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Study of horizontal axis tidal turbine performance and investigation on the optimum fixed pitch angle using CFD

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-05-2019-0447 ◽

2019 ◽

Vol 30 (1) ◽

pp. 206-227 ◽

Cited By ~ 12

Author(s):

Hoseyn A. Amiri ◽

Rouzbeh Shafaghat ◽

Rezvan Alamian ◽

Seyed Mohamad Taheri ◽

Mostafa Safdari Shadloo

Keyword(s):

Pitch Angle ◽

Flow Characteristics ◽

Horizontal Axis ◽

Speed Ratio ◽

Wall Region ◽

Computational Domain ◽

Thrust Coefficient ◽

Content Type ◽

Tidal Turbine ◽

Fixed Pitch

Purpose The purpose of this paper is to design, investigate and optimize a horizontal axis tidal turbine (HATT) using computer-aided numerical simulation and computational fluid dynamics (CFD). This is the first step of research and development (R&D) for implementation in the Persian Gulf condition. To do so, suitable locations are reviewed. Then, the optimization is focused on determining the optimum fixed pitch angle (β) of a three-bladed HATT based on the widespread multiple reference frame (MRF) technique to calculate power and thrust coefficients at different operational rotating speeds. Design/methodology/approach To simplify the problem and reducing the computational costs due to cyclic symmetry only one blade, accordingly one-third of the whole computational domain is considered in the modeling. Due to flow’s nature involving rotating, separation and recirculation, a realizable κ-ε turbulence model with standard wall function is selected to capture flow characteristics influenced by the rotor and near the wall region. Simulations are conducted for two free-stream velocities, then compared with their dependencies through the dimensionless tip speed ratio (TSR) parameter. Findings The validation process of the simulations is carried out by the use of AeroDyn BEM code, which has been evaluated by comparing with two experimental data. As results, the highest coefficient of power is achieved at ß = 19.3° at TSR = 4 with the value around 0.41 and 0.816 for thrust coefficient. Furthermore, to comprehend the rotor’s performance and simulation method, flow characteristics due to the rise in angular velocity is discussed in detail. Moreover, the major phenomenon, cavitation occurrence, is also checked at the critical situation where it is found to be safe. Originality/value By comparing and evaluating the results to other HATTs, it implies that the proposed rotor of this study is feasible and proved by CFD evaluation at this step. However, the current rotor is awaiting a justification through experimental assessment.

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Development of an Analytical Unsteady Model for Wind Turbine Aerodynamic Response to Linear Pitch Changes

Journal of Solar Energy Engineering ◽

10.1115/1.4033592 ◽

2016 ◽

Vol 138 (5) ◽

Cited By ~ 1

Author(s):

Mohamed M. Hammam ◽

David H. Wood ◽

Curran Crawford

Keyword(s):

Wind Turbine ◽

Pitch Angle ◽

Turbine Rotor ◽

Speed Ratio ◽

Element Analysis ◽

Tip Speed Ratio ◽

First Order ◽

Vortex Model ◽

Constant Pitch ◽

Induced Velocity

A simple unsteady blade element analysis is used to account for the effect of the trailing wake on the induced velocity of a wind turbine rotor undergoing fast changes in pitch angle. At sufficiently high tip speed ratio, the equation describing the thrust of the element reduces to a first order, nonlinear Riccti's equation which is solved in a closed form for a ramp change in pitch followed by a constant pitch. Finite tip speed ratio results in a first order, nonlinear Abel's equation. The unsteady aerodynamic forces on the NREL VI wind turbine are analyzed at different pitch rates and tip speed ratio, and it is found that the overshoot in the forces increases as the tip speed ratio and/or the pitch angle increase. The analytical solution of the Riccati's equation and numerical solution of Abel's equation gave very similar results at high tip speed ratio but the solutions differ as the tip speed ratio reduces, partly because the Abel's equation was found to magnify the error of assuming linear lift at low tip speed ratio. The unsteady tangential induction factor is expressed in the form of first order differential equation with the time constant estimated using Jowkowsky's vortex model and it was found that it is negligible for large tip speed ratio operation.

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A case study on optimum tip speed ratio and pitch angle laws for wind turbine rotors operating in yawed conditions

Journal of Physics Conference Series ◽

10.1088/1742-6596/555/1/012022 ◽

2014 ◽

Vol 555 ◽

pp. 012022

Author(s):

A Cuerva-Tejero ◽

O Lopez-Garcia ◽

D Marangoni ◽

F González-Meruelo

Keyword(s):

Wind Turbine ◽

Pitch Angle ◽

Speed Ratio ◽

Tip Speed Ratio ◽

Turbine Rotors

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Characteristic Analysis of Three-Bladed Darrieus Wind Turbine Based on the Multiple Streamtube Model

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.651-653.663 ◽

2014 ◽

Vol 651-653 ◽

pp. 663-667 ◽

Cited By ~ 1

Author(s):

Jing Ru Chen ◽

Zhen Zhou Zhao ◽

Tao Li

Keyword(s):

Wind Turbine ◽

Pitch Angle ◽

Power Coefficient ◽

Speed Ratio ◽

Characteristic Analysis ◽

Negative Power ◽

Tip Speed Ratio ◽

Maximum Value ◽

Blade Pitch Angle ◽

Ratio Range

The paper analyzes the effect of airfoil thickness, camber and blade pitch angle on the performance of the three-bladed Darrieus wind turbines. The research results show that the increase of airfoil thickness, camber and pitch angle of blade, can improve power coefficient when the wind turbine tip speed ratio between zero and four. The increase of thickness and camber of the airfoil leads to running tip speed ratio range of wind turbine get narrowed, and reduces the power coefficient when wind turbine runs in high tip speed ratio range. When the pitch angle of blade is 1˚, power coefficient reaches the maximum value. Negative pitch angle has a bad impact on power coefficient and even creates negative power coefficients.

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Some effects of flow expansion on the aerodynamics of horizontal-axis wind turbines

Wind Energy Science ◽

10.5194/wes-6-1413-2021 ◽

2021 ◽

Vol 6 (6) ◽

pp. 1413-1425

Author(s):

David H. Wood ◽

Eric J. Limacher

Keyword(s):

Axial Velocity ◽

Momentum Equation ◽

Horizontal Axis ◽

Speed Ratio ◽

Axial Component ◽

Horizontal Axis Wind Turbine ◽

Tip Vortices ◽

Tip Speed Ratio ◽

Constant Pitch ◽

Far Wake

Abstract. The flow upwind of an energy-extracting horizontal-axis wind turbine expands as it approaches the rotor, and the expansion continues in the vorticity-bearing wake behind the rotor. The upwind expansion has long been known to influence the axial momentum equation through the axial component of the pressure, although the extent of the influence has not been quantified. Starting with the impulse analysis of Limacher and Wood (2020), but making no further use of impulse techniques, we derive its exact expression when the rotor is a circumferentially uniform disc. This expression, which depends on the radial velocity and the axial induction factor, is added to the thrust equation containing the pressure on the back of the disc. Removing the pressure to obtain a practically useful equation shows the axial induction in the far wake is twice the value at the rotor only at high tip speed ratio and only if the relationship between vortex pitch and axial induction in non-expanding flow carries over to the expanding case. At high tip speed ratio, we assume that the expanding wake approaches the Joukowsky model of a hub vortex on the axis of rotation and tip vortices originating from each blade. The additional assumption that the helical tip vortices have constant pitch allows a semi-analytic treatment of their effect on the rotor flow. Expansion modifies the relation between the pitch and induced axial velocity so that the far-wake area and induction are significantly less than twice the values at the rotor. There is a moderate decrease – about 6 % – in the power production, and a similar size error occurs in the familiar axial momentum equation involving the axial velocity.

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