Effect Of Pitch Angle Research Articles

A numerical investigation of a new horizontal wind turbine performance for rural use

In this paper, a new configuration of a horizontal axis wind turbine with three blades for domestic electricity production on farms was numerically simulated. Three configurations were tested numerically: a standard single-blade wind turbine (STWT), a single wind turbine (SWT), and a tandem three-blade wind turbine (TWT) for rural use. For the tandem wind turbine, the effects of pitch angle and the distance between the blades were also investigated. The Gambit and Fluent 19.2 codes were, respectively, used to generate different meshes and determine various parameters. The resolution of the averaged Navier–Stokes equations (RANS) using a finite volume method was conducted. The k–[Formula: see text] realizable two-equation model was chosen for turbulence calculation. The obtained results showed that the maximum power coefficient (Cp) was 0.444 for one of the tandem configurations (TWT), compared to the conventional blade (STWT). The maximum Cp obtained in this study is slightly greater than the experimental results found in the literature. It has also been observed that the flow on these new turbines exhibits a complex phenomenon on both surfaces.

Experimental Study on the Pitot Tube Pitch Angle Effect on the Measurement of Velocity

Experimental Study on the Pitot Tube Pitch Angle Effect on the Measurement of Velocity

A probabilistic fatigue life assessment method for wind turbine blade based on Bayesian GPR with the effects of pitch angle

AbstractThe fatigue behavior of large wind turbine blades is complex and stochastic due to their complex structure and operating environment. This paper focuses on developing a probabilistic fatigue life assessment method for wind turbine blades considering the uncertainties from wind velocity, material mechanical properties, pitch angle, and layer thickness. To improve the efficiency of stochastic fatigue behavior analysis of wind turbine blade, unidirectional fluid‐structure coupling (UFSC) and bidirectional fluid‐structure coupling (BFSC) analysis are employed to analyze the stochastic response. Then, Gaussian process regression (GPR) and Bayesian updating are combined to establish the stochastic fatigue behavior prediction model for wind turbine blade. On this basis, a modified S‐N curve formulation is proposed, and the fatigue life of wind turbine blade is analyzed by the modified S‐N curve and compared with the three‐parameter Weibull model. The results indicate that the proposed method for fatigue life assessment has better accuracy. The proposed probabilistic fatigue life assessment method with high accuracy and high efficiency, which is beneficial for the fatigue reliability design of wind turbine blades.

Study on the Pitch Angle Effect on the Power Coefficient and Blade Fatigue Load of a Vertical Axis Wind Turbine

For vertical axis wind turbines (VAWTs), the increase of the incoming wind speed higher than the rated value will make the tip speed ratio (TSR) lower and lower, resulting in the blade fatigue load becoming more and more severe and the power coefficient weakening gradually. This paper explores whether varying the pitch with the TSR decrease is necessary for improving the power coefficient and reducing the fatigue load. Specifically, the pitch angle effect on the power coefficient and fatigue load of a VAWT at different TSRs was studied by the computational fluid dynamics method. The results show that the optimal pitch angle in terms of the power coefficient varies with the TSR, which means that varying the pitch with the TSR decrease can improve the power coefficient. Meanwhile, the principle to guide the pitch variation is to avoid flow separation in the downwind zone and minimize the angles of attack (AoAs) in the upwind zone. At the lowest TSR of 1.7 in the present work, varying the pitch from the optimal one in terms of the power coefficient reduced the blade normal force amplitude significantly, which is mainly attributed to avoiding the vortex–blade encounter and minimizing the AoAs in the downwind zone. The vortex–blade encounter at the lowest TSR is an important phenomenon related to the variation of the blade torque and blade normal force and will weaken and disappear with the pitch angle increase.

Effects of pitch angle on a near free surface underwater vehicle

Simulations of an underwater vehicle were conducted to investigate the effects of steady pitch angle, Froude number, and submergence depth. A shallow submerged (D* = 1.1) to a deeply submerged (D* = 6.6) SUBOFF was investigated over a range of steady pitch angles and Froude numbers. Results show that proximity to the free surface causes increased resistance, heave and pitch moment and that free surface effects diminish rapidly with increased submergence depth. Even though D* = 3.3 is typically quoted as being the deeply submerged threshold, free surface effects can still be observed especially at large pitch angles. At pitch angle, asymmetry can be seen between the pressure distribution of the upper and lower surfaces of the SUBOFF, with a phase shift of the hydrodynamic forces and moments. At smaller pitch angles, the changes in hydrodynamic forces and moments stay relatively linear at an offset from zero degrees. At larger pitch angles, the hydrodynamic forces and moments become non-linear due to crossflow separation and air entrainment over the bow/stern. Additionally, the potential of the stern planes to cope with free surface effects were investigated, showing the safety threshold with respect to Froude number, submergence depth, and hull pitch angle.

An experimental study to investigate the effect of pitch angle and wave characteristics on the performance of a horizontal axis tidal turbine

This study investigates the performance characteristics of a scaled-down three-bladed tidal turbine in a towing tank. The effects of pitch angle, electrical load, wave characteristics, and current velocity on turbine performance are examined. The experimental model, a 1:6 scale horizontal-axis tidal turbine with a rotor diameter of 1.15 m, is tested in the Strait of Khoran in Iran, selected based on tidal potential evaluation. After calibration and uncertainty analysis, experimental tests are conducted using the Taguchi method to optimize parameters and explore turbine performance in different conditions: current-only and wave-current interactions. Results demonstrate the direct relationship between power, momentum, thrust, rotor speed, and current velocity. Notably, power and momentum coefficients exhibit nonlinear (polynomial) variations at different tip speed ratios (TSRs). The presence of waves consistently enhances turbine performance compared to the no-wave mode, albeit with a lesser impact than other variable parameters. A pitch angle of 18.77° in the presence of waves yields a significant increase of up to 31.1% in power coefficient and up to 23.6% in momentum coefficient, compared to the no-wave mode. The optimal blade angle generally falls within the range of 30–35 mm, with 35 mm (18.77°) and 30 mm (22.72°) as the respective optimum pitch angles for wave-current interaction and the no-wave state. Optimal electrical load is achieved by setting Rheostat equal to 20 Ω, resulting in a remarkable 11% to 40% increase in system efficiency. In the upstream flow, the maximum power and momentum coefficients are observed as 0.219 and 0.033, respectively, at a TSR of 6.62 in the presence of waves with a dimensionless wave number of 3.43. Similarly, in the no-wave mode, the optimal power and momentum coefficients are obtained as 0.205 and 0.0286, respectively, at a TSR of 7.18. These findings highlight the significance of waves with a dimensionless wave number of 3.43.

Optimization of the Energy Capture Performance of the Lift-Drag Hybrid Vertical-Axis Wind Turbine Based on the Taguchi Experimental Method and CFD Simulation

In order to improve the energy capture performance of vertical axis lift wind turbines in a low wind speed environment, the drag wind turbine is employed to couple with the design of existing vertical axis lift wind turbines. In contrast to the existing literature, in this work, a computational model is proposed that can simulate the interaction between the turbine and the fluid. The effects of pitch angle (β), installation angle (θ), overlap ratio (ε) and diameter ratio (DL) on the energy capture performance of hybrid vertical axis wind turbines are systematically analyzed based on Taguchi and CFD methods. The results show that under the optimized parameter combination, the peak energy capture coefficient of the lift-drag hybrid wind turbine can be increased to 0.2328, compared with 0.0309 and 0.0287 of the pure lift and drag turbine, respectively. In addition, the result of the prototype test show that the optimized hybrid wind turbine not only has a better-starting performance but also has 2.0 times the output power of that of the lift wind turbine.

Thermal buckling behavior of Bouligand inspired laminated composite plates

Natural Bouligand structure is a special class of hierarchical architectures, which have proven to be effective in enhancing its mechanical properties. In this work, we demonstrate that the thermal buckling capacity of Carbon Fibre Reinforced Plastics can also be improved by mimicking bio-inspired Bouligand architectures. A finite element approach using commercial software ABAQUS is developed to predict the critical buckling temperature of the Bouligand inspired laminated plates under thermal loading. Numerical predictions show a good agreement with analytical results obtained from the literature. The effectiveness of Bouligand-type composite laminates in enhancing thermal buckling behavior is first confirmed by comparing with unidirectional, cross-ply and quasi-isotropic laminates. We then present the effects of pitch angle and ply thickness on the thermal buckling temperature of bio-inspired Bouligand-type laminates. Finally, we conclude that the improved mechanical and thermal properties can be simultaneously achieved by the Bouligand structure of laminates as the pitch angle is increased. The present study highlights the high thermal buckling behavior of biomimetic Bouligand structure, offering a possibility in developing biomimetic composites with good trade-off between mechanical properties and thermal performance.

The aerodynamic effects of blade pitch angle on small horizontal axis wind turbines

PurposeThe purpose of this paper is to thoroughly investigate the aerodynamic effects of blade pitch angle on small scaled horizontal axis wind turbines (HAWTs) using computational fluid dynamics (CFD) method to find out the sophisticated effects on the flow phenomena and power performance.Design/methodology/approachA small HAWT is used as a reference to validate the model and examine the aerodynamic effects. The blade pitch angle was varied between +2 and −6 degrees, angles which are critical for the reference wind turbine in terms of performance, and the CFD simulations were performed at different tip speed ratio values, λ = 2, 3, 4, 5, 6, 7, 9 and 10.5 to cover the effects in various conditions. Results are examined in two different aspects, namely, general performance and the flow physics.FindingsThe power performance varies significantly according to the tip speed ratio; the power coefficient increases up to a certain pitch angle at the design tip speed ratio (λ = 6); however, between λ = 2 and 4, the more the blade is pitched downwards, the larger is the power coefficient, the smaller is the thrust coefficient. Similarly, for tip speed ratios higher than λ = 8, the positive effect of the low pitch angles on the power coefficient at λ = 6 reverses. The flow separation location moves close to the leading edge at low tip speed ratios when the blade is pitched upwards and the also tip vortices become more intense. In conclusion, the pitch control can significantly contribute to the performance of small HAWTs depending on different conditions.Originality/valueIn the literature, only very little attention has been paid to the aerodynamic effects of pitch angle on HAWTs, and no such study is available about the effects on small HAWTs. The change of blade pitch angle was maintained at only one degree each time to capture even the smallest aerodynamic effects, and the results are presented in terms of the power performance and flow physics.

Investigation of pitch angles on the aerodynamics of twin-VAWT under staggered arrangement

The potential applications of twin vertical axis wind turbines (VAWTs) in oceanic wind energy harvesting have drawn increasing attention. Previous researches have focused on the influence of relative location, rotational direction, tip speed ratio, etc. on the power output of this system. However, limited studies have been done to uncover the effect of pitch angles on their aerodynamic performance, especially under staggered arrangements where the blade-vortex interaction remarkably occurs. In the current study, the methods of computational fluid dynamics are used to simulate the changes of power coefficients of the twin staggered H-rotors with their pitch angles. With a relative distance of 1.6 times diameter and a relative angle of 30 °, the rotors are operated at the optimal tip speed ratio in a co-rotating direction. Totally 49 cases are conducted to investigate the pitch angle range from −6° to 0° in both rotors. It is found that the changes in pitch angle of the target rotor will affect the performance of itself and the other rotor with fixed pitch angle. Within the specified pitch range, due to the influence of the other rotor, the largest difference in power performance reaches 4.79% for the upstream rotor, and 7.04% for the downstream one. In addition, the aerodynamic mechanism is comprehensively analysed through the comparisons among velocity, vorticity and pressure fields. The findings of the current study is helpful to provide suggestions for the design of twin-VAWT system.

3D concrete printing of bioinspired Bouligand structure: A study on impact resistance

For extrusion-based 3D concrete printing, research work on mechanical properties mainly focuses on static behaviour, whereas dynamic performance has been rarely reported. Meanwhile, biomimicry is getting increasing interests in the field of 3D concrete printing, due to its advantage of improving structural properties and optimising material usage by learning from nature. Inspired by the Bouligand structure in the dactyl club of mantis shrimp, this study explored the impact resistance of 3D-printed concrete specimens with and without steel fibres under drop weight impact tests. Four different printing patterns were designed, including the pitch angle of 0˚, 15˚, 30˚ and 45˚. For fibre-reinforced specimens, those with helicoidal patterns performed better than the one with unidirectional pattern (i.e. 0˚) in terms of impact duration, peak impact force and energy absorption. For specimens without fibres, the effect of pitch angle on the impact resistance was insignificant. The influence of pitch angle on impact resistance was more profound when specimens were incorporated with steel fibres during the printing process. Micro-CT images showed the size and geometry of internal pores were influenced by the printing pattern, thus affecting the mechanical response. Meanwhile, fibre-reinforced specimens presented complex cracking mechanisms with mixed modes, including crack deflection, twisting, branching, bridging and micro-cracks. Analysis on fibre orientation revealed the fibre alignment in the direction of the toolpath, leading to effective crack-bridge actions by steel fibres as the crack propagated during the impact process.

Aerodynamic Design and Wind Tunnel Tests of Small-scale Horizontal-axis Wind Turbines for Low Tip Speed Ratio Applications

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).

Analysis of The Effect of Pitch Angle on Propeller Modification by Considering Wake Distribution on Propeller Performance

The propeller is an important component of the ship’s propulsion system, and its design related to the safety and ship’s cost. The propeller is operated in an uneven flow field behind the ship so it has an important influence on the cavity, vibration and hydrodynamic performance. Therefore, optimization calculations are needed to get most economical in addition to meeting the provisions of the Energy Efficiency Design Index. Optimization software through polynomial regression values can be used for selecting propeller. However, when the propeller is installed on the hull, the Velocity Advance (Va) on the propeller will change from the distribution at the time of the open water test because of the shape of the hull. This reduces the performance of propeller. So it is necessary to calculate the engine propeller hull matching to get a match on each propulsion component. Blade element theory concept can be used in designing the propeller for the engine hull matching, with the hypothesis that if the pitch angle is greater than Va, cavitation will occur. This condition is not allowed and if the pitch angle is too small for Va, the thrust cannot be maximized against flow, then it must adjust to the Velocity Advance (Va) distribution on the ship’s hull, because increasing the thrust value will also increasing propeller’s relative rotative efficiency (ηR) and open water efficiency (ηO) and hull efficiency (ηH). This situation makes a proportional increase in the value of the propulsive coefficient. The simulations are carried out on the size of the model with a dual domain (single-hull) by turning the propeller while the ship is stationary and seeing the convergent speed generated by the ship. The simulation data that will be taken are propeller thrust and torque because these values are considered sufficient to compare the simulation results. It’s getting the thrust foil value that making model S_T, S_eta and S_KomL S_T model is done by looking at the highest thrust, S_eta model with highest efficiency method and on S_KomL with highest thrust and efficiency by looking at the streamlined model, the thrust and efficiency values are equal to or higher of the MP687. It is showed that open water efficiency value in the two modified models has decreased, namely S_T model of 0.341, S_KomL of 0.345 and S_eta of 0.301 with original MP687 model of 0.371. While the hull efficiency of S_T model has decreased to 1,449 and S_KomL model increased by 1,591 and S_eta model increased by 3.8 but in MP687 model was 1,526, and the relative rotate efficiency of S_T model increased to 1,096, S_KomL model also increased by 1,099 and also S_eta model of 1.08 which originally on the MP687 1,055 model. This will result in the Propulsive Coefficient (PC) value in S_T model of 0.543 with decreasing, S_KomL 0.604 and S_eta 1.25 with an increase from the original MP687 0.597

Effect of Pitch Angle on the Winding Capacity of Nb3Sn Rutherford Cable

Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford cable can be used in the next generation of superconducting magnets above 10 T which cannot be reached with NbTi strands. Rutherford cable is a multi-strand twisted cable with a two-layer structure and rectangle or trapezoidal cross section. Strands are fully transposed with respect to magnetic field. The pitch angle is important for Rutherford cable, which affects the AC loss and bending ability of the cable. Usually different magnets adopt different pitch angles according to the requirement. The winding capacity of the cable is one of a key point. To evaluate the influence of the pitch angle on the cable winding capacity and establish a reference for a new cable design, finite element method based on ABAQUS has been conducted to simulate the cable winding process.

Numerical analysis of the pitch angle effect on the performance improvement and flow characteristics of the 3-PB Darrieus vertical axis wind turbine

Present work aims to enhance the aerodynamic performance of the three-part-blade (3-PB) Vertical Axis Wind Turbine (VAWT) by setting a pitch angle using the solution of Reynolds averaged Navier-Stokes (RANS) equations in two and three dimensions. The 3-PB turbine with zero pitch angle is taken as the reference for comparison at wind speed of 7 m/s and tip speed ratios (TSRs) from 0.44 to 1.77. Having analyzed five pitch angles using 2D simulation, the best pitch angle of -2° is selected for 3D simulations. Flow characteristics and output torque of both 3-PB turbines with 0 and -2° pitch angles are scrutinized in 3D simulation. The blade with -2° pitch angle in the upwind area significantly contributes to the output torque, resulting in performance improvement for most TSRs. The modified turbine demonstrates the most improvement in average of total torque coefficient at TSR = 0.89, by 13.65%, while the maximum reduction in deviation of total torque coefficient from its average is 16.92% at TSR = 1.33. Based on the results, a delay of about 2° in azimuth angle has happened in dynamic stall phenomenon in the 3-PB turbine with -2° pitch angle. More details about flow structure are given in the paper.

Effect of pitch angle in the performance of wind turbine using numerical techniques

The study of performance on the Darrieus turbine is an emerging topic using many techniques to make it improve the performance up to the industrial standard. The angle of air received at the leading edge of the aerodynamic wind blade influencing the performance of the turbine. Every instant of the angle of air varying each blade due to the rotating motion of the turbine. The objective of this paper is to determine the optimum pitch angle using the Computational Fluid Dynamics simulation technique in Ansys 18.1, where the sliding mesh technique is used. The geometry of the blade is taken from the previous literature which is used to verify the results. The various pitch angles are chosen from -6° to +6°. The coefficient of the moment is calculated using K-epsilon SST 2 equation model. The graph is plotted between TSR and the coefficient of performance of various pitch angle for optimization purpose.

Effect of pitch angle on power and hydrodynamics of a vertical axis turbine

The use of vertical-axis turbines in marine-current applications for electric energy generation is still in early developments, and one of the key factors for assessing the applicability of such technology is the power coefficient. To contribute towards the highly competitive market of renewable energy conversions, the turbine system requires good outcomes in terms of energy yield. In this scenario, one of the main challenges regarding the design process to improve the blade performance is to find the best trade-off between the maximization of the power output and the minimization of the structural loadings.In the current work, the influence of blade pitch angles on the hydrodynamics of a vertical-axis five-blade water turbine has been studied. The pitch angles from −5° to +5° were investigated using Computational Fluid Dynamics (CFD). The simulations were validated against experimental data for the power coefficient collected in a river. Overall, a good agreement was found in terms of computed power between simulations and experiments for a wide range of tip speed ratios. The CFD model was proven to be suitable for exploratory analyses and an optimized design was found, providing a 2.3% higher power coefficient by adopting a pitch angle of +2° compared to the zero-referenced pitch angle. Besides validating with the experiment, the CFD simulations were compared with the results of a vortex model. The effect of different pitch angles on the performance prediction and on the blade and turbine loadings was also discussed. It is becoming vital to develop an understanding of the complex interaction of vertical-axis turbines, especially in tidal-current areas where there is a lack of detailed experimental data.

Diagonal inflow effect on the wake characteristics of a horizontal axis wind turbine with Gaussian model and field measurements

This paper investigates the diagonal inflow effect on the wake characteristics of a HAWT (Horizontal Axis Wind Turbine) in a wind farm. In this study, a HAWT with the generator capacity of 30 kW and the rotor diameter of 10.0 m is used. Firstly, the effect of pitch angle on the power and thrust performances of wind turbine are investigated through field experiment. On this basis, the wake characteristics of the HAWT are examined with different wind directions and pitch angles. The velocity field is measured by the ultrasonic anemometers, the three-cup type anemometer and the wind vane. Finally, the annual power generation of the downstream wind turbine is predicted by different Gaussian models. As a result, the maximum power coefficients Cp are 0.31, 0.33 and 0.27, corresponding to the tip speed ratios λ = 7.5, 7.4 and 6.8 and the pitch angles β = 0°, 2° and 4°, respectively. The standard deviations of wind direction are divided into four regions between σθ = 5° and 20°. The maximum deficit values of the wake velocity decreases from 0.27 to 0.16, and the full wake widths at half maximum Dr increases from 1.35 to 1.71 with σθ increasing from 5°∼9°–14°∼20°. The amount of annual energy production predicted by the wind tunnel experiment model is about 51 % of the field experiment model. This study provides a better understanding of the wake characteristics and a guiding significance for the layout optimization of wind farms.

Numerical simulation and experimental study of blade pitch effect on Darrieus straight-bladed wind turbine with high solidity

Increasing the solidity in vertical axis wind turbines (VAWT) leads to the decreased coefficient of performance (COP) despite the improved start-up performance. To overcome this problem, the pitch regulation system is proposed in this paper for increasing the solidity. In most of the previous investigations, the effect of pitch angle was tested on low-solidity VAWT at uniform flow conditions and low turbulence intensity in wind tunnel test sections, which are different from the real conditions. In this investigation, the influence of pitch angle on the aerodynamic performance of a small Darrieus-type straight-bladed high-solidity VAWT equipped with a pitch regulation system is investigated numerically and experimentally under realistic condition. The proposed numerical procedure is validated through experimental test results. The COP is measured and calculated at different tip speed ratios and two pitch angles of 0 and 5°. The results reveal 25% enhancement in maximum COP with the increase of pitch angle up to 5°. Moreover, according to the numerical results, higher accuracy can be obtained at lower tip speed ratios for both pitch angles. Then, the numerical method is employed to calculate the power (performance) and torque coefficients as a function of Azimuth position as well as the flow field in rotor affected zone and lateral distance. It is found that increasing the pitch angle at a constant tip speed ratio is followed by accelerated vorticity generation, occurrence of maximum COP at lower tip speed ratio and smoother velocity profile in lateral distances of the rotor.

Effects of Pitch Angle on the Correction Factors for the Stress Intensity Factors of Semielliptic Surface Cracks in Helical Compression Springs

Effects of Pitch Angle on the Correction Factors for the Stress Intensity Factors of Semielliptic Surface Cracks in Helical Compression Springs