基于外场实验的风力机叶片三维效应研究

针对一台33 kW水平轴风电机组开展了外场实验,得到其叶片7个断面翼型的压力分布曲线;基于求解时均N-S方程对风轮进行三维数值模拟,以及将叶片各断面作为二维翼型进行数值计算,分别得到各断面翼型的压力分布曲线及升阻力系数.通过将外场实验、三维和二维数值计算所得压力分布曲线及升阻力系数进行对比分析,研究了三维效应对风力机气动性能的影响.研究表明,从叶尖到叶根各断面翼型的压差先增大后逐渐减小,叶片表面压力分布曲线比较明显地反映了从叶尖到叶根流动分离的变化;叶片表面压力分布的三维数值计算结果较二维计算结果更加接近于外场实验值;风力机叶片表面的三维流动对叶片的气动性能影响较大,在叶尖和叶根部分尤为突出.

Numerical Simulation of Wind Turbine Wake Characteristics in Uniform Inflow

Flow field around a two-bladed horizontal-axis wind turbine(HAWT)is simulated at various tip speed ratios to investigate its wake characteristics by analyzing the tip and root vortex trajectories in the nearwake,as well as the vertical profiles of the axial velocity.Results show that the pitch of the tip vortex varies inversely with the tip speed ratio.Radial expansion of the tip vortices becomes more obvious as the tip speed ratio increases.Tip vortices shed not exactly from the blade tip but from the blade span of 96.5%—99%radius of the rotor.The axial velocity profiles are transformed into V-shape from W-shape at the distance downstream of eight rotor diameters due to the momentum recovery.

Design and Experimentation of a 1 MW Horizontal Axis Wind Turbine

In this work was carried out the aerodynamics design of a 1 MW horizontal axis wind turbine by using blade element momentum theory (BEM). The generated design was scaled and built for testing purposes in the discharge of an axial flow fan of 80 cm in diameter. Strip theory was used for the aerodynamic performance evaluation. In the numerical calculations was conducted a comparative analysis of the performance curves adding increasingly correction factors to the original equation of ideal flow to reduce the error regarding real operating values got by the experimental tests. Correction factors introduced in the ideal flow equation were the tip loss factor and drag coefficient. BEM results showed good approximation using experimental data for the tip speed ratio less than design. The best approximation of the power coefficient calculation was for tip speed ratio less than 6. BEM method is a tool for practical calculation and can be used for the design and evaluation of wind turbines when the flow rate is not too turbulent and radial velocity components are negligible.

Proposal for Offshore Wind Farm with Triangle-Coupled Movable Parallelogram Buoyancy Structure for the High Seas

We are responsible for providing energy and food resources for our next generation.After more than 20 years of research,the author has confirmed that the VAWT with flip-up mechanism can maintain rotation without the brake,even in strong winds.Experiments have shown that the triangularly coupled movable parallelogram buoyancy structure makes it easy to maintain the verticality of the wind turbine tower even under large waves.Furthermore,as a result of studying the connection between the HAWT(horizontal axis wind turbine)and the movable parallelogram buoyancy structure of the triangular connection,the feasibility was confirmed.The only way for all people in the world to secure energy and food fairly is to look for the remaining areas such as the high seas.The author would like to propose the use of the high seas to combat global hunger,which is likely to be a global problem in the future.

A Novel Power Curve Prediction Method for Horizontal-Axis Wind Turbines Using Artificial Neural Networks

Accurate prediction of wind turbine power curve is essential for wind farm planning as it influences the expected power production.Existing methods require detailed wind turbine geometry for performance evaluation,which most of the time unattainable and impractical in early stage of wind farm planning.While significant amount of work has been done on fitting of wind turbine power curve using parametric and non-parametric models,little to no attention has been paid for power curve modelling that relates the wind turbine design information.This paper presents a novel method that employs artificial neural network to learn the underlying relationships between 6 turbine design parameters and its power curve.A total of 198 existing pitch-controlled and active stall-controlled horizontal-axis wind turbines have been used for model training and validation.The results showed that the method is reliable and reasonably accurate,with average R^(2)score of 0.9966.

On Optimization of Power Coefficient of HAWT

The horizontal axis wind turbine (HAWT) blades rotation in the steady wind flow is considered. We discuss the problem of determining the blade twist which could guarantee the maximum value of the power coefficient. We define the blade twist as the technological turn of sections of blade around its axis. This turn changes the effective pitch angle of turbine blade along its length. For description of aerodynamic load upon the blades we used the quasi-steady approach. Air velocities of centers of pressure of blade sections are represented when taking into account components induced by flow and vortex. We reduced the functional maximization problem to find the maximum of non-dimensional function. This function is given by Riemann integral depending on section pitch angle and tip speed ratio. We suggested the algorithm for solving the problem under consideration for a given blade shape.

Behavior of HAWT with Differential Planetary Gearbox

A dynamic model for simulating behavior of a horizontal axis wind turbine (HAWT) with differential planetary gearbox is developed. The aerodynamic load applied to the wind turbine connected with the carrier is described using the quasi-steady approach. The control torque is assumed to be applied to the external ring of the gearbox. Steady regimes of the device are analyzed, and their stability is studied. For the case of constant control torque, power costs are estimated required for preserving constant angular speed of the generator.

Effect of Boundary Layer Fence Location on HAWT Power Performance

Even though wind energy is a deep-rooted technology, but not yet mature and hence there are bounteous scopes for improvement to reduce the cost of wind energy. An experimental investigation has been carried out on 1:25 scaled S809 aerofoil blade featuring boundary layer fence at various span wise location. Quantifying electrical power obtained by rotation of wind turbine rotor coupled with dynamic testing system. A baseline model with no flow control and an upgraded model with detachable boundary layer fence have been studied in the wind tunnel. For upgraded model, fences were placed along the location of 40% to 90% of the blade span. The rotor blades are then tested dynamically in wind tunnel at open terrain condition for 7 m/s, 9 m/s and 11 m/s velocities. In order to study the effect of boundary layer fence test has been carried out in the low speed wind tunnel having test section of size 0.9 m × 1.2 m × 2 m. Scope corder DL 750 is used to measure time varying voltage and proximity sensor with its compatible display unit is used to measure the rotor RPM. The flow behaviour was found to be considerably favourable from conventional rotor blades. Installation of fence has been found promising for increased energy extraction from air column by controlling the three dimensional span wise flow. Results demonstrate the potential of the proposed model which can obtain a maximum of about 11.8% increase in the power. In addition, the significance of the location of wing fence and blade pitch angle has been analysed.

A study on performance influences of airfoil aerodynamic parameters and evaluation indicators for the roughness sensitivity on wind turbine blade

The roughness increase on horizontal axis wind turbine(HAWT) blade surface,especially on the leading edge,can lead to an aerodynamic performance degradation of blade and power output loss of HAWT,so roughness sensitivity is an important factor for the HAWT blade design.However,there is no criterion for evaluating roughness sensitivity of blade currently.In this paper,the performance influences of airfoil aerodynamic parameters were analyzed by the blade element momentum(BEM) method and 1.5 MW wind turbine blade.It showed that airfoil lift coefficient was the key parameter to the power output and axial thrust of HAWT.Moreover,the evaluation indicators of roughness sensitivity for the different spanwise airfoils of the pitch-regulated HAWT blade were proposed.Those respectively were the lift-to-drag ratio and lift coefficient without feedback system,the maximum lift-to-drag ratio and design lift coefficient with feedback system for the airfoils at outboard section of blade,and lift coefficient without feedback,maximum lift coefficient with feedback for the airfoils at other sections under the pitch-fixed and variable-speed operation.It is not necessary to consider the roughness when HWAT can be regulated to the rated power output by the pitch-regulated and invariable-speed operation.