Flow Field Of Turbine Research Articles

Wind loads and load-effects of large scale wind turbine tower with different halt positions of blade

In order to investigate the influence of different blade positions on aerodynamic load and wind loads and load-effects of large scale wind turbine tower under the halt state, we take a certain 3 MW large scale horizontal axis three-blade wind turbine as the example for analysis. First of all, numerical simulation was conducted for wind turbine flow field and aerodynamic characteristics under different halt states (8 calculating conditions in total) based on LES (large eddy simulation) method. The influence of different halt states on the average and fluctuating wind pressure coefficients of turbine tower surface, total lift force and resistance coefficient, circular flow and wake flow characteristics was compared and analysed. Then on this basis, the time-domain analysis of wind loads and load-effects was performed for the wind turbine tower structure under different halt states by making use of the finite element method. The main conclusions of this paper are as follows: The halt positions of wind blade could have a big impact on tower circular flow and aerodynamic distribution, in which Condition 5 is the most unfavourable while Condition 1 is the most beneficial condition. The wind loads and load-effects of disturbed region of tower is obviously affected by different halt positions of wind blades, especially the large fluctuating displacement mean square deviation at both windward and leeward sides, among which the maximum response occurs in <TEX>$350^{\circ}$</TEX> to the tower top under Condition 8; the maximum bending moment of tower bottom occurs in <TEX>$330^{\circ}$</TEX> under Condition 2. The extreme displacement of blade top all exceeds 2.5 m under Condition 5, and the maximum value of windward displacement response for the tip of Blade 3 under Condition 8 could reach 3.35 m. All these results indicate that the influence of halt positions of different blades should be taken into consideration carefully when making wind-resistance design for large scale wind turbine tower.

Aerodynamic optimization of shrouded wind turbines

An axisymmetric Reynolds averaged Navier–Stokes solver is used along with an actuator disk model for the analysis of shrouded wind turbine flowfields. Following this, an efficient blade design technique that maximizes sectional power production is developed. These two techniques are incorporated into an optimization framework that seeks to design the geometry of the shroud and rotor to extract maximum power under thrust constraints. The optimal solution is also evaluated using a full three-dimensional Reynolds averaged Navier–Stokes solver, suggesting the viability of the design. The predicted optimal designs yield power augmentations well in excess of the Betz limit, even if the normalization of the power coefficient is performed with respect to the maximum shroud area. Copyright © 2016 John Wiley & Sons, Ltd.

Numerical simulation of the near-wake flow field of a horizontal-axis wind turbine (HAWT) model

Using different tip speed ratios, the near-wake velocity field of a horizontal-axis wind turbine (HAWT) model was simulated. The distributions of the near-wake velocity behind the HAWT rotor are obtained. Furthermore, the development of the wake is shown. The resulting data can be used to identify and better understand the physical attributes of the complex flow field, as well as to aid in the accurate prediction of the HAWT’s performance. Calculations indicate that the axial flow downstream of the near-wake region displays obvious three-dimensional properties. The axial component of air flow velocity is larger than the tangential and radial velocity components. For wind turbines of varying heights, the velocity profiles for each component are similar in the near-wake region. Velocity loss exists downstream of the wind turbine’s near-wake region, decreasing with an increase in axial position downstream of the turbine. The rate of decrease in center velocity is largest at the near-wake region from the trailing edge of the blade to the position of twice the chord length downstream of the turbine. At the position of four times the chord length downstream, the lowest velocity is restored to over 70 % of the free incoming flow velocity.

CFD based synergistic analysis of wind turbines for roof mounted integration

The increasing global demand for energy and environmental concerns have provoked a shift from exhaustible, fossil fuel based energy to renewable energy sources. It is clear that wind energy will play an important role in satisfying our current and future energy demands. In this paper, a horizontal configuration of a Savonius wind turbine is proposed to be mounted on the upstream edge of a building, in such a way that its low performance is improved by taking advantage of the flow acceleration generated by the edge of the building. The importance of integrated simulations which include both the building and the turbine is shown and it is also demonstrated that the individual calculations of the flow around the building and the turbine individually cannot be superposed. Following the validation of our methodology with experimental data, we calculate the performance of the Savonius wind turbines placed in the vicinity of the edge of the building top. The position, blade number, and circumferential length are then investigated when the turbine is mounted on a building. The objective is to better understand wind turbine behavior for low speed urban environments. The flow fields of conventional Savonius and cup type turbines are solved using Computational Fluid Dynamics (CFD) in 3D domains. The optimal configuration shows an improvement in the power coefficient from 0.043 to 0.24, representing an improvement of 450%. The improvement also demonstrates that although cup type blades show very poor performance in free stream flow, they perform well in the right environment.

Adaptability of turbulence models to predict the performance and blade surface pressure prediction of a Francis turbine

Purpose – The purpose of this paper is to analyze the ability of turbulence models to model the flow field in the runner of a Francis turbine. Although the complex flow in the turbine can be simulated by CFD models, the prediction accuracy still needs to be improved. The choice of the turbulence model is one key tool that affects the prediction accuracy of numerical simulations. Design/methodology/approach – This study used the SST k-w and RNG k-e turbulence models, which can both accurately predict complex flow fields in numerical simulations, to simulate the flow in the entire flow passage of a Francis turbine with the results compared against experimental data for the performance and blade pressure distribution in the turbine to evaluate the applicability of the turbulence models. Findings – The results show that the SST k-w turbulence model more accurately predicts the turbine performance than the RNG turbulence model. However, the blade surface pressures predicted by the SST k-w turbulence model were basically identical to those predicted by the RNG k-e turbulence model, with both accurately predicting the experimental data. Research limitations/implications – Due to the lack of space, the method used to measure the blade surface pressure distributions is not introduced in this paper. Practical implications – Turbine performance and flow field pressure in the runner, which are the basis of turbine preliminary performance judgment and optimization through CFD, can be used to judge the rationality of the turbine runner design. The paper provides an evidence for the turbulence selection in numerical simulation to predict turbine performance and flow field pressure in the runner and improves the CFD prediction accuracy. Originality/value – This paper fulfils a test of the flow field pressure in the runner, which provide an evidence for judge the adaptability of turbulence model on the flow field in runner. And this paper also provides important evaluations of two turbulence models for modeling the flow field pressure distribution in the runner of a Francis turbine to improve the accuracy of CFD models for predicting turbine performance.

Experimental and Numerical Investigation of the Flow in a Low-Pressure Industrial Steam Turbine With Part-Span Connectors

An experimental and numerical study on the flow in a three-stage low-pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide range and even in blade resonance condition. However, additional losses are generated which affect the performance of the turbine. In order to capture the impact of PSCs on the flow field, extensive measurements with pneumatic multihole probes in an industrial steam turbine test rig have been carried out. State-of-the-art three-dimensional computational fluid dynamics (CFD) applying a nonequilibrium steam (NES) model is used to examine the aerothermodynamic effects of PSCs on the wet steam flow. The vortex system in coupled LP steam turbine rotor blading is discussed in this paper. In order to validate the CFD model, a detailed comparison between measurement data and steady-state CFD results is performed for several operating conditions. The investigation shows that the applied one-passage CFD model is able to capture the three-dimensional flow field in LP steam turbine blading with PSC and the total pressure reduction due to the PSC with a generally good agreement to measured values and is therefore sufficient for engineering practice.

ポンプ水車内部流れ場のPIV計測とCFD

ポンプ水車内部流れ場のPIV計測とCFD

Investigations on the Aerodynamic Characteristics and Blade Excitations of the Radial Turbine with Pulsating Inlet Flow

AbstractThe aerodynamic performance, detailed unsteady flow and time-based excitations acting on blade surfaces of a radial flow turbine have been investigated with pulsation flow condition. The results show that the turbine instantaneous performance under pulsation flow condition deviates from the quasi-steady value significantly and forms obvious hysteretic loops around the quasi-steady conditions. The detailed analysis of unsteady flow shows that the characteristic of pulsation flow field in radial turbine is highly influenced by the pulsation inlet condition. The blade torque, power and loading fluctuate with the inlet pulsation wave in a pulse period. For the blade excitations, the maximum and the minimum blade excitations conform to the wave crest and wave trough of the inlet pulsation, respectively, in time-based scale. And toward blade chord direction, the maximum loading distributes along the blade leading edge until 20% chord position and decreases from the leading to trailing edge.

A Simulation Study of Flow and Pressure Distribution Patterns in a Two Stage Three Bucket Savonius Vertical Axis Wind Turbine

Performance of Savonius vertical axis wind turbine can be increased by incorporating end plates, deflector plates, curtains, shielding, guide vanes etc in their designs. However, multi-staging of conventional VAWT rotors could be a viable proposition in terms of improvement of power output. Numerical analysis involving three bucket Savonius turbines are not available in the open domain. The objective of the present numerical investigation is to study the flow and pressure distribution patterns in the two-stage three bucket Savonius vertical axis wind turbine. The performance of SVAWT is based on the maximum difference in pressure between the upstream and downstream of the turbine. Velocity vector plots shows the energy transfer occurring from the fluid to the blade within the flow field in the upstream and downstream of the turbine. The trail of the wake left behind the SVAWT was observed in the downstream of the turbine. It is observed that eddies in large scale are present around the turbine flow field.

HYDRODYNAMIC CALCULATION OF ROTATING WEIS-FOGH-TYPE WATER TURBINE WITH THE ADVANCED VORTEX METHOD

In this study, a rotating-type water turbine model applying the principle of the Weis-Fogh mechanism is proposed, and its hydrodynamic characteristics calculated by an advanced vortex method. The unsteady flow and pressure fields around the wing for two revolutions were calculated by changing the uniform flow and maximum opening angle of the wing. The maximum efficiency for one wing of the water turbine was 45.3% at the maximum opening angle of the wing 36° and velocity ratio 2.0. The flow field of the water turbine is very complex because the wing rotates and moves unsteadily in the channel. However, using the advanced vortex method, accurate calculations were possible.

Design and numerical simulation on coupled flow field of radial turbine with air-inlet volute

As one of the core components of turbocharger or micro-turbine, radial turbine has the features of small size and high rotation speed. In order to explore the design method and flow mechanism of the turbine with a volute, a centimeter-scale radial turbine with a vaneless air-inlet volute was designed and simulated numerically to investigate the characteristics of the coupled flow field. The results show that the wheel efficiency of single passage computation without the volute is 80.1%. After accounting for the factors of the loss caused by the volute and the interaction between each passage, the performance is more accurate according to the whole flow passage computation with the volute. High load region gathers at the mid-span and the efficiency declines to 76.6%. The performance of the volute whose structure angle of the trapezoid section is equal to 70 degree is better. Unlike uniform inlet condition in single passage, more appropriate inlet flow for the impeller is provided by the rectification effect of the volute in full passage calculation. Flow parameters are distributed more evenly along the blade span and are generally consistent between each passage at the outlet of the turbine.

Numerical simulation of circumferentially averaged flow in a turbine

The paper refers about the development of a fast computational code, which should be able to provide an approximate information about the three-dimensional flow field in a multistage turbine. The code is based upon the solution of circumferentially averaged Euler equations coupled with the thermodynamic, geometry and loss prediction models. The computational domain is the meridional cut of a turbine. The Euler equations are solved by a finite volume solver with the AUSM type flux. Initial tests showed, that developed solver is able to predict well radial distributions of flow parameters upstream and downstream considered blade cascades at a fraction of CPU time compared to fully three-dimensional simulations.

Unsteady Flow Numerical Simulation of Vertical Axis Wind Turbine

This paper sets up model of the flow field for vertical axis wind turbine based on airfoil DU93-W–210. FLUENT is used to solve the two dimensional unsteady incompressible N-S equations with RNG κ-ɛ turbulence model. COUPLE algorithm and sliding mesh is used to simulate the 2-D unsteady flow field of the wind turbine. The rotor power coefficient of wind energy and the variation of the wind turbine's total torque are analyzed under the variation of varied blade installation angle and chord length. As the result shows, the power coefficient of wind energy at the best installation angle is increased by 2%, and the power coefficient of wind energy in the best solidity is increased by 15%.

Analysis and Evaluation of Wind Turbine Flow Field and Noise Simulation Based on CFD Software

CFD is the abbreviation of the computational fluid dynamics, which is widely used in engineering fluid simulation. Based on two-dimensional N-S equation and k-e turbulence model, this paper uses FLUENT software, finite volume method and SIMPLEC algorithm to do numerical simulation and analysis on flow field in centrifugal fan. In order to improve the efficiency and accuracy of calculation, this paper uses AutoCAD to establish the two-dimensional model of fan, and uses the structured triangular mesh to divide grid. Encrypting the blade can improve the precision and also save the computer memory. Through the calculation we get the internal flow field velocity and pressure distribution in the wind turbine, and get the power level cloud of internal noise in fan. It provides the technical reference for the optimization design of wind turbine.

Comparison of BEM-CFD and full rotor geometry simulations for the performance and flow field of a marine current turbine

Recent studies have coupled blade element momentum (BEM) theory with the Reynolds Averaged Navier–Stokes equations in computational fluid dynamics (CFD) software, as the BEM-CFD method to analyse the flows in marine current turbines is with much less computational resources. The accuracy of the BEM-CFD calculation was evaluated by analysing the performance and flow field characteristics of an isolated horizontal axis marine current turbine with comparisons to a full rotor geometry simulation and experimental data. The comparisons show that the full rotor geometry simulation gives good predictions near the optimal conditions (TSR = 5–7), but is less accurate for off-design conditions. The BEM-CFD results, which are based on two-dimensional hydrofoil theory, are evaluated using the experimental and numerical lift and drag coefficients. It shows that the two-dimensional lift and drag coefficients had significant effects on the BEM-CFD predictions. Overall, the BEM-CFD based on the numerical hydrofoil data can accurately predict the thrust, but generally overestimates the power. The influence of the lift and drag terms on the BEM-CFD predictions suggest that more reasonable 2D predictions for hydrofoils and the 3D effects should be considered to improve the BEM-CFD accuracy. BEM-CFD can reasonably reflect the circumferential averaged velocity characteristics near the rotor for the optimal condition (TSR = 6) and gets symmetrical features in the wake, but it cannot predict the detailed flow features caused by the finite number of blades due to the limitations of the BEM-CFD method.

Study on the Flow Field of an Undershot Cross-Flow Water Turbine

The purpose of this investigation is to research and develop a new type water turbine, which is appropriate for low-head open channel, in order to effectively utilize the unexploited hydropower energy of small river or agricultural waterway. The application of placing cross-flow runner into open channel as an undershot water turbine has been under consideration. As a result, a significant simplification was realized by removing the casings. However, flow field in the undershot cross-flow water turbine are complex movements with free surface. This means that the water depth around the runner changes with the variation in the rotation speed, and the flow field itself is complex and changing with time. Thus it is necessary to make clear the flow field around the water turbine with free surface, in order to improve the performance of this type turbine. In this research, the performance of the developed water turbine was determined and the flow field was visualized using particle image velocimetry (PIV) technique. The experimental results show that, the water depth between the outer and inner circumferences of the runner decreases as the rotation speed increases. In addition, the fixed-point velocities with different angles at the inlet and outlet regions of the first and second stages were extracted.

Numerical Simulation and Experimental Research of Blade Erosion in Particulate Gas Turbine

Euler-Lagrange method is adopted to simulate 3-D viscous turbulent flow field of a one-stage gas turbine. Gas-solid two-way coupling is realized to analyze the trajectories and slip of 1000 beam particles, with diameter 5~50μm, then calculate the mass erosion rate based on the impact velocity and attack angles. Simulation exhibits: erosion wear is mainly caused by impact of larger particles (&gt;10μm), erosion areas are mainly concentrated on the roots of pressure surface entrance of static blade and on the rear pressure surface of rotor blade. Comparing experiments are conducted between the substrate of X20Cr13 and the specimen with steel-bead injection. Experiment indicates: the attack angle corresponding to the maximal mass loss for substrate is about 40°, while the steal-bead injection is about 50°. Within the scope of the attack angle 20°~80°, the mass loss of the reinforced specimen is obviously less than that of the substrate, and under other angles of attack, the two kinds of material’s erosion tolerance are close to each other.

GPU Based Fast Free-Wake Calculations For Multiple Horizontal Axis Wind Turbine Rotors

Unsteady free-wake solutions of wind turbine flow fields involve computationally intensive interaction calculations, which generally limit the total amount of simulation time or the number of turbines that can be simulated by the method. This problem, however, can be addressed easily using high-level of parallelization. Especially when exploited with a GPU, a Graphics Processing Unit, this property can provide a significant computational speed-up, rendering the most intensive engineering problems realizable in hours of computation time. This paper presents the results of the simulation of the flow field for the NREL Phase VI turbine using a GPU-based in-house free-wake panel method code. Computational parallelism involved in the free-wake methodology is exploited using a GPU, allowing thousands of similar operations to be performed simultaneously. The results are compared to experimental data as well as to those obtained by running a corresponding CPU-based code. Results show that the GPU based code is capable of producing wake and load predictions similar to the CPU- based code and in a substantially reduced amount of time. This capability could allow free- wake based analysis to be used in the possible design and optimization studies of wind farms as well as prediction of multiple turbine flow fields and the investigation of the effects of using different vortex core models, core expansion and stretching models on the turbine rotor interaction problems in multiple turbine wake flow fields.

Numerical Simulation of the Aerodynamic Performance of a H-Type Wind Turbine during Self-Starting

The aerodynamic performance and the bypass flow field of a vertical axis wind turbine under self-starting are investigated using CFD simulations in this paper. The influence of pitch angle variations on the performance of the wind turbine during self-starting is presented. A two-dimensional model of the wind turbine with three blades is employed. A commercial software FlowVision is employed in this paper, which uses dynamic Cartesian grid. The SST turbulence model is used for turbulence modeling, which assumes the flow full turbulent. Based on the comparison between the computed time-dependent variations of the rotation speed with the experimental data, the time-dependent variations of the torque are presented. The characteristics of self-starting of the wind turbine are analyzed with the pitch angle of 0o、-2oand 2o. The influence of pitch angle variations on two-dimensional unsteady viscous flow field through velocity contours is discussed in detail.

Hierarchical Methodology for the Numerical Simulation of the Flow Field around and in the Wake of Horizontal Axis Wind Turbines: Rotating Reference Frame, Blade Element Method and Actuator Disk Model

A hierarchy of computational methods for Horizontal Axis Wind Turbine (HAWT) flow field is proposed, focusing on rotor models for Reynolds-Averaged Navier-Stokes simulations. Three models are systematically compared to determine their adequacy to capture performance and wake dynamics, and the trade-offs between accuracy and computational cost. The Rotating Reference Frame model is prescribed for detailed flow field studies, specifically at the root and blade tip. The Blade Element Model does not reproduce the near wake region but successfully predicts the velocity deficit in the axisymmetric far wake, and the power and torque coefficients. The Actuator Disk Model underestimates the velocity deficit in the far wake, but can be corrected to perform simulations of large wind farms. This methodology is applied to a canonical rotor and compared against experimental data. These models span three orders of magnitude in computational time and cost for the study of HAWT aerodynamic performance and wake interaction.