Showing papers on "Wells turbine published in 2023"
TL;DR: In this paper , the authors applied a combination of stall fences and casing grooves for passive flow control of a Wells turbine, which increased the operating range up to 33.3% and the peak-to-average power ratio decreased by 27.7%.
Abstract: Abstract Remarkable advancement in wave energy conversion technology has taken place in recent years. Due to its simplicity, the Wells turbine has been one of the most widely used power take-off mechanisms in an oscillating water column type wave-energy conversion device. However, the turbine suffers from several challenges due to its narrow operating range, which hinders the commercial feasibility of the system. Several aerodynamic applications have successfully used passive control methods to modify the flow conditions. This work applied a combination of stall fences and casing grooves for passive flow control of a Wells turbine. The computational fluid dynamics (CFD) technique is used to analyze the modified turbine numerically. The casing groove modified the tip-leakage vortices, interacted with local vortices created by the stall fences, and helped reattach the flow at higher flow coefficients. As a result, the modified turbine increases the operating range up to 33.3%. In addition, the peak-to-average (PTA) power ratio decreased by up to 27.7%.
2 citations
TL;DR: In this article , the influence of VGs on the hydrodynamic characteristics of the turbine blades of the NACA 4418 hydrofoil has been investigated using a numerical simulation.
Abstract: Tidal turbine blades are prone to flow separation in the boundary layer under high speed or high angle of attack(AOA), which will reduce energy efficiency and even the stall damage of the blades. This paper proposes introducing the flow control theory of Vortex Generators(VGs) to tidal turbines and studying the influence of VGs on the hydrodynamic characteristics of the tidal turbine blades. Firstly, a numerical study is performed to investigate the effects of VGS on the hydrodynamic performance of the NACA 4418 hydrofoil. The impact of different parameters, such as VG arrangement, spacing, height and length, on the hydrodynamic performance of hydrofoil is studied by the CFD method. The results show that VGs can effectively suppress the flow separation and improve the maximum lift coefficient of the hydrofoil. The influence of VGs on flow separation characteristics of horizontal axis tidal turbines (HATT) is studied by the CFD method. The results show that the flow separation of turbine blades mainly occurs at the root part of the suction surface, and the flow separation region expands radially as the flow velocity increases. VGs can effectively reduce the flow separation area on the suction side of turbine blades by suppressing the flow separation effect. Compared with the turbine blades without VGs, the power coefficient of turbine blades with VGs is increased by up to 5%. The flume experiment verifies the accuracy of the simulation results.
1 citations
TL;DR: In this paper , the design and experimental testing of a high-solidity biplane Wells turbine with and without guide vanes were investigated on a unidirectional flow test rig to investigate turbine performance and flow characteristics.
1 citations
TL;DR: In this paper , a self-rectifying impulse turbine with U-shaped duct is proposed for oscillating water column wave energy conversion, which has a pair of fixed, symmetrical and radial-flow guide vane rows, and an axisymmetric, U-shape duct with increasing cross-sectional area from the rotor to the guide vanes, therefore it is expected to be relatively simple, reliable and efficient.
TL;DR: In this article , the authors used the response surface optimization library in the ANSYS software to optimize the performance of the axial turbine of a wave energy conversion turbine and found that the tip treatment strategy was utilized to improve the performance.
TL;DR: In this article , a rectangular Gurney flap (GF) at the trailing edge (TE) of a Wells turbine consisting of hybrid airfoil (NACA 0015 and NACA 0025) blades with variable chord distribution along the span was adopted to achieve increased power production by the Wells turbine.
Abstract: In the past decade, there has been renewed interest in wave energy harvesting utilizing oscillating water columns (OWC), one of the most well-studied wave energy harnessing technologies. In the OWC, pneumatic power from ocean waves is converted to mechanical energy by Wells turbines. It should be noted, however, that such turbines tend to perform poorly, have a limited operating range, and have low efficiency. In the present study, we incorporate a rectangular Gurney flap (GF) at the trailing edge (TE) of a Wells turbine consisting of hybrid airfoil (NACA 0015 and NACA 0025) blades with variable chord distribution along the span. This passive flow control mechanism was adopted to achieve increased power production by the Wells turbine. This study aimed to determine the aerodynamic performance of the variable chord turbine with GF compared to a turbine with a constant chord. By using ANSYS™ CFX, the three-dimensional, steady-state, incompressible Reynolds averaged Navier–Stokes (RANS) equations coupled with the k-ω SST turbulence model are solved. The performance was evaluated through the use of non-dimensional coefficients of torque, pressure drop, and efficiency. In addition, the numerical accuracy was achieved through a grid independence study. There was a good agreement between the computed results and the available experimental and numerical data. The GF increased the torque coefficient by 18.6% and 47.3% but with the expense of peak efficiency of 8.5% and 7.4% for the baseline and the hybrid turbine, respectively. Additionally, the hybrid turbine with GF delayed the onset of the stall by ~3° angle of attack (AOA).
TL;DR: In this article , the design of a closed cycle power takeoff (CCPTO) for a shore-based installation, with particular attention paid to the turbine, is presented, and the entire system is simulated with a reduced order model for a range of sea states to estimate the operating conditions of the turbine.
Abstract: A promising class of devices for ocean wave energy conversion is called the oscillating water column in which the wave power is transferred to an airflow that rotates a turbine. A closed cycle power takeoff (CCPTO), in which air is forced through two valves and a turbine, has two main benefits for such a system: it allows a unidirectional turbine, and it smooths the large variations in pressure due to irregular (i.e., polychromatic) seas. This paper presents the design of a CCPTO for a shore-based installation, with particular attention paid to the turbine. The entire system is simulated with a reduced order model for a range of sea states to estimate the operating conditions of the turbine. It is found that the pressure drop range is modest but strongly dependent on the tide and sea chamber geometry. The geometry of the turbine is initially developed with a 1D preliminary design of the blades and then the turbine performance is analysed and the design is refined using Reynolds Averaged Navier–Stokes simulations. The design process is conducted based on the geometry and the sea climate of a real-life wave energy installation located in Mutriku (Spain). A turbine that displays efficient performance over a wide range of sea states is obtained. The overall performance of this turbine as part of the entire CCPTO system is assessed and leads to an energy output of ∼1500 kWh for one month in sea conditions at Mutriku wave power plant in Spain. It is concluded that the CCPTO deserves further development in any fixed oscillating wave column system.
07 Apr 2023
TL;DR: In this paper , a 3D-printed contra rotary self-rectifying impulse turbine with middle vanes was generated as a demonstration model and the efficiency of the turbine was determined by the turbine's design configuration and the chamber's partially submerged water column.
Abstract: Background: The global energy demand is rising day to day. To cover the energy gap, governments around the world are pursuing a variety of strategies to meet energy demands. However, according to the long-term strategy, all nonrenewable energy plants must be replaced with renewable energy sources. Existing technologies are enhanced, and new sources are being investigated for this purpose. The ocean covers 70% of the planet so there is a huge potential to extract energy from this source. Objective: This research aims to optimize the design of an oscillating water column (OWC) wave energy converter to extract energy from ocean waves. Methods: The total efficiency of an OWC wave energy converter is determined by the turbine's design configuration and the chamber's partially submerged water column. The various designs of wave energy turbines were examined before simulating the contra rotary impulse turbine with middle vanes at specific angles. The efficiency of the turbine was determined using ANSYS FLUENT workbench simulations. Additionally, the design of an OWC was simulated to determine the optimal chamber slope. To conduct experiments, a 3D-printed contra rotary self-rectifying impulse turbine with middle vanes was generated as a demonstration model. Middle vanes used in contra-rotary turbines can assist in reducing turbulence between contra rotors. Results: The results demonstrate that the turbine with middle vanes has a higher torque coefficient Ct than the turbine without middle vanes. Similarly, the input coefficient Ca is higher for the turbine which has middle vanes. Therefore, the turbine with a middle vane shows better efficiency than the turbine without a middle vane in low flow coefficient as well as higher flow coefficient. Conclusion: The efficiency of the contra rotatory turbine is greater than the single rotatory turbine and the efficiency increases further when middle vanes are added.
01 Jan 2023
TL;DR: In this article , two dimensional CFD simulation have been carried out on Darrieus lift type turbine having NACA0017 blade profile and the performance of this airfoil is compared with the already established NACA 0015.
Abstract: The vertical axis wind turbine has many advantages as compared to horizontal axis wind turbine as they are much more convenient to use in urban areas, turbulent environment and low wind speed regions. However, its low efficiency and low self-start ability are the main concerns. For the performance enhancement of the turbine, selection of effective blade profile is an important criterion. In this paper two dimensional CFD simulation have been carried out on Darrieus lift type turbine having NACA0017 blade profile. The performance of this airfoil is compared with already established NACA0015 airfoil. The numerical results predicted that power coefficient of NACA0017 is relatively on higher side at higher TSR which also provides good structural strength due to its higher thickness. The peak value of power coefficient is found to be 0.4 and 0.38 at velocity 5m/s and 4m/s respectively.
07 Feb 2023
TL;DR: In this paper , the authors applied a combination of stall fences and casing grooves for passive flow control of a Wells turbine, which increased the operating range up to 33.3% and the peak-to-average power ratio decreased by 27.7%.
Abstract: Abstract Remarkable advancement in wave energy conversion technology has taken place in recent years. Due to its simplicity, the Wells turbine has been one of the most widely used power take-off mechanisms in an oscillating water column type wave-energy conversion device. However, the turbine suffers from several challenges due to its narrow operating range, which hinders the commercial feasibility of the system. Several aerodynamic applications have successfully used passive control methods to modify the flow conditions. This work applied a combination of stall fences and casing grooves for passive flow control of a Wells turbine. The computational fluid dynamics (CFD) technique is used to analyze the modified turbine numerically. The casing groove modified the tip-leakage vortices, interacted with local vortices created by the stall fences, and helped reattach the flow at higher flow coefficients. As a result, the modified turbine increases the operating range up to 33.3%. In addition, the peak-to-average (PTA) power ratio decreased by up to 27.7%.
TL;DR: In this paper , a 2D URANS (Unsteady Reynolds-Averaged Navier Stokes) numerical analysis is employed for an H-Darrieus VAWT.
Abstract: Vertical Axis Wind Turbines (VAWTs) have proven to be suitable for changing wind conditions, particularly in urban settings. In this paper, a 2D URANS (Unsteady Reynolds-Averaged Navier Stokes) numerical analysis is employed for an H-Darrieus VAWT. A turbulent domain is created through systemically randomising the inlet velocity to create macro-turbulence in front of the VAWT. The parameters for spatial and temporal randomisation of velocity and its effects on the turbine performance are studied for a mean free stream velocity, U∞ = 10 m/s, and a tip speed ratio (TSR) of 4.1. The mean Coefficient of power (Cp) for randomised fluctuation of 2 m/s and half-cycle randomisation update frequency is 0.411 and for uniform inlet velocity is 0.400. The Cp vs. Tip Speed ratio plot suggests that the optimal tip speed ratio for operation is around 4.1 for this particular wind turbine of diameter 1 m, chord 0.06 m, and NACA 0018 airfoils. The effect of randomisation for tip speed ratio λ = 2.5, 3.3, 4.1, and 5.3 on the performance of the turbine is studied. Turbine wake recovers at a faster rate for macro-turbulent conditions and is symmetric when compared to wake generated by uniform velocity inlet. The maximum velocity deficit for a distance behind the turbine, x/d = 8 at TSR (λ) = 4.1 is 46% for randomised inlet and 64% for uniform inlet. The effect of randomisation for λ = 2.5 to 5.3 on the performance of the turbine is analysed. A time-varying gust based on International Electrotechnical Commission (IEC) Extreme Operating Gust is used to study the effect of fluctuating wind conditions in a turbulent environment. Since real-time conditions often exceed gust factors mentioned by IEC, winds with large gust factors such as 1.50, 1.64, and 1.80 are analysed. With an increase in gust amplitude, Ugust = 6 m/s to Ugust = 12 m/s on a free stream velocity of U∞ = 10 m/s, the mean Cp decreases from 0.41 to 0.35 since the wind turbine operates under tip speed ratios outside optimal range due to large fluctuations in incoming velocity.
TL;DR: In this paper , the effect of geometric change in leading-edge radius (LER) of a vertical axis wind turbine performance has been numerically studied and the results indicated that the leading edge radius affected the near wake flow of the turbine, and the optimization of leadingedge radius parameter controlled the dynamic stall and reduces the formation of a vortex.
Abstract: Numerous studies have been conducted to investigate effect of blade geometry of vertical axis wind turbine performance. Most of the evaluations have focused on the airfoil series and airfoil geometry parameters such as thickness and camber of the airfoil. Few studies have examined the effect of other blade geometry parameters on the vertical axis wind turbine performance. In the present study, the effect of geometric change in leading-edge radius (LER) of a vertical axis wind turbine performance has been numerically studied. Hence, modified NACA 0021 airfoil profiles were created using the geometric method (CST). Then, the flow behavior around a Darrieus vertical axis wind turbine was simulated under the influence of the reduction and set-up coefficients of the leading-edge radius at a constant wind speed of 9 m/s and a tip speed ratio of 1.5 to 3.5 using the computational fluid dynamics. Additionally, the effects of the examined parameter (leading-edge radius) on fluid flow and aerodynamic performance coefficients, including the coefficients of power and torque, were investigated. The results indicated that the leading-edge radius affected the near wake flow of the turbine, and the optimization of leading-edge radius parameter controls the dynamic stall and reduces the formation of a vortex. Finally, the optimization of LER revealed that at 20% reduction in the LER the performance of the turbine at tip speed ratio of 1.5 was increased by more than 50%. This reinforces the self-starting capability of a Darrieus wind turbine.
TL;DR: In this article , the authors investigated the vortex effect on the turbine arm and proposed an advanced design to reduce its impact by using computational fluid dynamic method to analyze the vortex generated by turbine arm.
Abstract: The design of a marine current turbine generator specifically in deep water with unequal seabed which requires the designer to develop a floating platform for the turbine. It creates a massive challenge in improving the mechanical system, such as the turbine arm. In order to make the monitoring and maintenance accessible, the generator must be placed on the platform’s deck. A long shaft is required to make the connection between the generator and turbine. The problems occur due to the vibration generated by the vortex around the shaft or the turbine arm. This paper aim is to investigate the vortex effect on the turbine arm and propose an advanced design to reduce its impact. The computational fluid dynamic method is approached to analyse the vortex generated by the turbine arm. The analysis compared the conventional cylindrical and the foil-shaped turbine arm. Moreover, the investigation includes force along the X-axis and Y-axis, flow, drag, lift coefficient, also fatigue lift near the turbine arm. The numerical output illustrates that the foil shaped on the turbine arm provided limited vortex and improved the performance compared to the conventional cylindrical turbine arm.
TL;DR: In this paper , the authors proposed a built-in variable wavelength traveling wave turbine that established a traveling wave mechanism in the rectangular flow channel, which has the same function as a conventional turbine, extracting energy from incoming high-pressure gas, but operates in a completely different way from axial flow and centripetal types.
TL;DR: In this article , the authors describe the testing of a turbine model with an angled turbine blade that produces the best efficiency and rotation due to wave forces and ocean currents, and the test is carried out by varying the angle of the turbine blade tilt (45°, 60°, and 75°) each is given a variation in height and wave period but still, maintains the turbine rotor area.
Abstract: Indonesia has a long coastline that has the potential for renewable energy sources from waves to be used as an energy source for power generation. To take advantage of this potential, research has been carried out by testing the Darrieus-type vertical axis turbine model at the Indonesian Hydrodynamics Laboratory. The weakness of the wave turbine is that it cannot rotate due to the wave force due to the position of the turbine rotor which is perpendicular to the turbine axis. By changing the angle of the turbine blade in an inclined position, it is expected to produce optimal efficiency to produce rotor rotation. This paper describes the testing of a turbine model with an angled turbine blade that produces the best efficiency and rotation due to wave forces and ocean currents. The test is carried out by varying the angle of the turbine blade tilt (45°, 60°, and 75°). Each is given a variation in height and wave period but still, maintains the turbine rotor area. Furthermore, the torque, efficiency, rotation, and resulting power are measured. wave height of 0.15 meters with variations in wave periods ranging from 1.2 - 2.5 seconds. The test results show that a turbine with a rotor angle of 60° produces the best performance.
TL;DR: In this article , an experimental and numerical analysis of the Hunter turbine, a vertical axis turbine utilized for tidal energy, was conducted on the surface of the turbine blade, and the results were obtained accordingly.
Abstract: This study involves an experimental and numerical analysis of the Hunter turbine, a vertical axis turbine utilized for tidal energy. A laboratory model of the Hunter turbine, featuring an aspect ratio of 1.2, was designed and tested. Numerical equations, including the Reynolds-averaged Navier–Stokes (RANS) constant, were analyzed through computational fluid dynamics (CFD) software using the k-ω turbulence model to forecast turbine performance and other related flow specifications, such as pressure lines, stream velocity, and pressure. This simulation was conducted on the surface of the turbine blade, and the results were obtained accordingly. The experimental data were utilized to verify the numerical results, and the difference between the two was reasonably acceptable. The turbine was studied in six different flow coefficients and four different vertical positions. The results indicated that the power coefficient increased as the submerged depth from a water-free surface increased, and after a specific depth, the output power remained constant. It was also observed that the minimum depth from a water-free surface for maximum power coefficient was three times the diameter of the turbine drum (3D).
TL;DR: In this paper , a 3-part-blade VAWT with a proper helix angle was used to smoothen the output torque of the 3-PB turbine by setting a proper angle of helix while maintaining its average of torque output.
TL;DR: In this paper , the authors investigated the flow behavior near the NACA 64-618 airfoil profile of the blade tip section of a wind turbine for electric power production after a short icing event.
Abstract: The paper investigates the flow behavior near the NACA 64-618 airfoil profile of the blade tip section of a wind turbine for electric power production after a short icing event. The flow simulation considering the rotation speed of the wind turbine blade is performed to assess the effect of icing on the aerodynamic characteristics. Degradation of aerodynamic characteristics affects the electrical energy production of the wind turbine. The aerodynamic lift and drag coefficients are calculated for different angles of attack. The flow velocity fields near the airfoil are analyzed. The pressure coefficient distributions along the profile surface are obtained. The points of flow stall and changes of aerodynamic characteristics at different angles of attack are determined.
TL;DR: In this article , a laboratory OWC system is simulated numerically with deformable grids to simulate the air-water interface, and a lumped-parameter model is used to reproduce the interaction between the air flow and the Wells turbine in the OWC systems.
TL;DR: In this article , the effects of geometry and design of an oscillating water column energy converter air chamber on the airflow response were analyzed using the commercial software ANSYS, where a vent is located at the chamber's outlet rather than a turbine.
Abstract: Abstract This paper represents the effects of geometry and design of an oscillating water column energy converter air chamber on the airflow response. The primary goal of this research is to use different shapes of air chambers, such as rectangular, cylindrical, and conical
air chambers with varying cross sections, to optimize the air velocity entering the turbine, to obtain the maximum power available in a progressive wave with a constant period and wavelength. Modeling and numericalsimulation are performed by using the commercial software ANSYS. Since this
paper is concerned with the effect of air flow velocity, a vent is located at the chamber's outlet rather than a turbine. In order to obtain the exit air velocity results, the wave system air characteristics results are applied as an input air flowfor three air chamber cases. The results show
that the air velocity flow increasedsignificantly from 7.14 m/s in the rectangular air chamber to 10.4 m/s in cylindrical air chamber and reached a maximum of 14.2 m/s in the conical airchamber.
TL;DR: In this paper , a 3D-printed monoplane Wells turbine has been tested at the open wind tunnel of the Polytechnic University of Bari, Italy, and it has been found that this unsteady behavior is due neither to the mass flow rate crossing the turbine nor to stagnation pressure drop, but only to the detachment of vortices generated from the leading edge and travelling along the suction side of the blade.
TL;DR: In this paper , the authors used dynamic fluid computational simulations in three-dimensional form with steady state conditions, discretization using second-order, with convergent conditions when it reached 10-6.
Abstract: This study simulated the characteristics of the fluid flow that passes through the Darrieus turbine before installation and testing were carried out. The purpose of knowing the flow characteristics can determine the profile and position of the maximum speed so that the design and placement of the turbine can be improved. The research method was carried out using dynamic fluid computational simulations in three-dimensional form with steady state conditions, discretization using second-order, with convergent conditions when it reached 10-6. The simulation results show that the position of the flow above the turbine had the lowest value because the fluid flowed relatively without disturbance which caused the velocity to had a value almost the same as the incoming fluid velocity. The fluid velocity increased when it was in line 2 and line 3 or across the turbine. This was due to the turbulence generated by the rotation of the turbine. While the speed on line 4 or below the turbine had a lower value than line 2 and line 3. This was due to the position below the turbine so that the turbine rotation did not have an impact on speed. At the four line positions the velocity increased at Y=0.7 m or when the fluid hits the turbine. This increase in fluid velocity was expected to turn the turbine. The results also included the flow distribution in the form of a streamline in several positions where the flow that was in contact with the channel wall had a low velocity value due to friction with the wall.
TL;DR: In this article , the characteristic of a combined three-blade vane type and three-bladed Darrieus turbine was computed by utilizing CFD software with k-ω turbulence model and commercial accessible solid work 2016.
Abstract: The field of renewable energy utilized is expanding. For this reason, many researchers in this field have centered on investigating the utilization of sustainable energy and diminishing the utilization of fossil fuels. The VAWTs is one of the sorts of wind turbines that are right now broadly utilized. Utilizing the Darrieus wind turbine, its beginning torque value is little due to the little projected area in contact with the wind stream. To extend this beginning torque, the vane-type blade with a vertical axis of revolution has been installed, which contains movable vans and installed with a three straight- bladed Darrieus airfoil (NACA0012) on the same turning shaft. In this paper, the characteristic of a combined three–blade vane type and three-bladed Darrieus turbine was talked about computationally by utilizing CFD (Fluent) software’ with k-ω turbulence model and commercial accessible solid work 2016. Through present study, the results gotten demonstrate that the beginning torque of the combined wind turbine increases when the blades with even movable vans are installed with the straight -bladed Darrieus wind turbine. Expanding the starting torque of the combined turbine because the wind stream is freely passed without any resistance through the movable vanes that are completely open on the inverse side of the wind direction, leads to an increment within the output power of the turbine compared to the comes about confirmed within the published sources of the vertical axis wind turbine, which has different shapes.