Structural design of spars for 100-m biplane wind turbine blades

Large wind turbine blades are being developed at lengths of 75–100 m, in order to improve energy capture and reduce the cost of wind energy. Bending loads in the inboard region of the blade make large blade development challenging. The “biplane blade” design was proposed to use a biplane inboard region to improve the design of the inboard region and improve overall performance of large blades. This paper focuses on the design of the internal “biplane spar” structure for 100-m biplane blades. Several spars were designed to approximate the Sandia SNL100-00 blade (“monoplane spar”) and the biplane blade (“biplane spar”). Analytical and computational models are developed to analyze these spars. The analytical model used the method of minimum total potential energy; the computational model used beam finite elements with cross-sectional analysis. Simple load cases were applied to each spar and their deflections, bending moments, axial forces, and stresses were compared. Similar performance trends are identified with both the analytical and computational models. An approximate buckling analysis shows that compressive loads in the inboard biplane region do not exceed buckling loads. A parametric analysis shows biplane spar configurations have 25–35% smaller tip deflections and 75% smaller maximum root bending moments than monoplane spars of the same length and mass per unit span. Root bending moments in the biplane spar are largely relieved by axial forces in the biplane region, which are not significant in the monoplane spar. The benefits for the inboard region could lead to weight reductions in wind turbine blades. Innovations that create lighter blades can make large blades a reality, suggesting that the biplane blade may be an attractive design for large (100-m) blades.     

螺旋侧板厚度对浮式风力机Spar平台涡激载荷的影响

Spar平台因其特殊的深吃水立柱式结构,在来流影响下极易发生涡激运动。为探究不同厚度螺旋侧板对浮式风力机Spar平台涡激载荷的影响,基于CFD方法,针对不同厚度螺旋侧板,对平台进行了数值模拟并详细分析平台的升阻力系数、压力场及涡量场等流场参数。结果表明:螺旋侧板可有效抑制涡激载荷,且随厚度增加,升力系数幅值先增加后减小,阻力系数逐步减小;在研究范围内,螺旋侧板厚度为0.10 D时,升力系数幅值最小,阻力系数与原型平台在同一范围内,对涡激载荷的抑制效果最好。     

考虑阻尼比的Spar式浮式风力机基础结构涡激运动特性研究

利用数值模拟方法对不同阻尼比条件下Spar式浮式风力机基础结构进行涡激运动特性的研究。从涡激运动响应幅值、频率比、位移、升力及拖曳力等方面研究Spar式浮式风力基础结构涡激运动的关键特性。研究表明:涡激运动上端分支对应的频率比为f_y/f_n≈1,且该分支出现最大幅值。随着阻尼比的增大,上端分支约化速度范围有减小趋势。低阻尼比下,力与位移的曲线出现"拍"现象;下端分支对应的频率比f_y/f_n均大于1,不随阻尼的改变而发生变化。上端分支与下端分支间,存在一过渡区域,该区域对应的斯托哈尔数St≈0.17,不随阻尼比的改变而改变。     

Spar平台的发展趋势及其关键技术

深海油气资源的大量开发加速了对适应深水环境的平台结构物的需求。Spar平台是一种用于深海环油气开采、生产、处理加工和储存的海洋结构物。本文介绍Spar平台的发展趋势及其关键技术的研究,包括平台动力响应、系泊系统、疲劳分析、耦合分析以及垂荡板和侧板的设计研究。     

Spar平台垂荡板设计中的关键问题

Spar平台是一种适宜于深海石油的开采、生产、处理加工和储存的平台结构形式。垂荡板是影响Truss Spar和Cell Spar垂荡性能的关键构件。垂荡板的性能及设计已是国际Spar工程和研究的热点之一。介绍了影响Spar平台垂荡板性能的主要因素,以及典型的垂荡板结构和主要载荷。     

垂荡板对传统Spar平台水动力特性的影响

为研究垂荡板对传统Spar平台水动力特性的影响,以Umaine-Hywind Spar平台为模型,利用有限元软件对垂荡板在Spar平台不同位置处的频域和时域特性进行分析,并在最佳位置处对比分析了不同透空率的垂荡板对Spar平台影响。结果表明:在相同的海况条件下,垂荡板在Spar平台下部安放有利于其工作,使其获得的响应更小,而在下部安放的垂荡板中,透空率为5%的垂荡板性能优于透空率为0的垂荡板。综合几个算例可以得出:垂荡板可以改变并优化Spar平台,然而这需要考虑影响垂荡板的因素(透空率,板间距、数目等),并非垂荡板就一定会降低Spar平台的垂荡响应。     

Spar平台垂荡阻尼板水动力研究综述

介绍了国内外在理论和试验两方面对垂荡板水动力性能的研究现状。研究表明,Spar平台的垂荡阻尼板通过增大平台的垂向阻尼和附加质量,能减小平台垂荡运动的剧烈程度。与其他增加阻尼的方法相比,垂荡板具有经济实用的特点,在海洋工程界受到越来越多的重视。     

Experimental study of the functionality of a semisubmersible wind turbine combined with flap-type Wave Energy Converters

In the present paper the functionality of the Semisubmersible wind energy and Flap-type wave energy Converter (SFC) is examined experimentally. In order to study the functionality of the SFC, the focus is on operational environmental conditions. SFC is a combined concept that utilizes offshore wind energy and ocean wave energy for power production. Details are presented as far as the physical modelling of the wind turbine with the use of a redesigned small-scale rotor and of the Power Take-Off mechanism of the Wave Energy Converters (WECs) with the use of a configuration that is based on a mechanical rotary damper. Tests with quasi-static excitation, motion decay, regular and irregular waves without and with wind that is uniform are conducted on an 1:50 scale physical model. The experimental data are compared with numerical predictions obtained by a fully coupled numerical model using Simo/Riflex tool. A good agreement is observed between experimental and numerical predictions. The combined operation of WECs doesn't affect the tension of mooring lines nor the acceleration of nacelle and the bending moment in tower's base. The produced power of the WECs of the SFC and consequently the functionality of the SFC is estimated.     

Structural integrity of a direct-drive generator for a floating wind turbine

In this work, the suitability of a direct-drive radial flux permanent magnet generator is examined as a probable drive-train candidate for a stepped-spar floating wind turbine system that supports a 2 MW downwind turbine. The suitability of the generator is assessed based on the structural integrity of its design (i.e., the stability of the air-gap between the rotor and stator) in response to the nacelle motions and its possible design implications on the overall system. Air gap deflections due to structural deflection and bearing tolerances were examined independently. The nacelle motions are obtained from experimental and numerical investigations on a 1:100 scale model. ANSYS suite is used to estimate the structural deformations of the generator and the changes in the air-gap distribution. Also, a simplified analytical model is used to compute the resulting changes in flux density and force distribution along the rotor periphery. The analytical model is also validated by 2D magneto-static simulations by utilising Finite Element Methods Magnetics software (FEMM).Preliminary results suggest that, if the nacelle accelerations are limited to 0.3 times the acceleration due to gravity (g) and the motion response cycles are below the fatigue limit, the air-gap stability of the generator is more sensitive to magnetic forces. Contributions to air-gap eccentricity from shaft displacements can be limited if the bearing supports can be designed for high stiffness. This also confirmed the adequacy of the platform design. The results also emphasise the need for air-gap management when designing direct-drive generators for floating wind turbines. Two methods are investigated as potential solutions to limit the maximum air-gap deflection to 10% level. The method of increasing structural stiffness led to a structurally unfavourable design that could potentially affect the stability and resonance properties of the system. The method of increasing the design air-gap led to a structurally more favourable design, although this meant an increase in magnetic material and hence the costs. Thus, implementing direct-drive radial flux permanent magnet generators for floating wind turbines is challenged by the difficulty in achieving optimal weight and costs at acceptable performance without compromising the air-gap tolerances. There is a need for an amendment to design standards to recognise the design challenges of Floating wind turbines.     

参一强激励作用下的Spar平台非线性纵摇运动响应分析

考虑垂荡运动和波浪激励力矩的双重影响,建立Spar平台参一强联合激励下的纵摇运动方程。应用摄动法求得当垂荡频率与纵摇固有频率比接近2:1时纵摇方程的一阶近似解,并分析了方程零解与定常周期解的运动稳定性。以一座试验Spar平台为例,计算了该平台在长周期涌浪下纵摇运动的时域响应。