Quantifying wave and yaw effects on a scale tidal stream turbine
Quantifying wave and yaw effects on a scale tidal stream turbine
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DOI：
10.1016/j.renene.2013.09.030
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发表时间：
2014-03
期刊：
影响因子：
8.7
通讯作者：
P. W. Galloway;L. Myers;A. Bahaj
中科院分区：
文献类型：
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作者：
P. W. Galloway;L. Myers;A. Bahaj
潮汐水轮机(TST)在波浪和转子与来流侧偏(偏航)引起的动态流场中的行为目前尚不清楚。对涡轮机施加的动态载荷可以驱动功率捕获和支持子系统的结构设计、装置尺寸及其与水面和海床的接近程度。此外，在许多潮汐能场所遇到的强双向流动可能会导致设备忽略偏航驱动；接受与转子不对中相关的额外动态负载，并减少发电量，以换取设备资本成本的降低。因此，有必要量化潜在的非定常转子载荷，以使TST装置设计适应流入条件，并避免不可接受的维护操作增加，或者更严重的是，遭受突然的结构故障。本文介绍的实验是在一个大型拖曳水池设施中使用1：20比例的三叶水平轴TST进行的。该涡轮具有测量转子推力和扭矩的能力，同时一个叶片被测量以获取叶片根部应变、方位位置和转速，所有这些都是在高频下进行的。最大面外弯矩是面内弯矩的9.5倍。在无旋翼、尺度波高为2米、固有波周期为12.8秒的涡轮试验台上，观测到的最大载荷范围为中值面外弯矩的175%和中值面内弯矩的100%。该模型考虑了一种新的动态入流修正，其结果与实测载荷非常吻合。重力分量对实验面内叶片弯矩有重要影响，也包含在边界元模型中。与波浪载荷(在实验范围内)相比，在正偏航角下单个叶片上的稳定载荷可以忽略不计，但对涡轮转子整体而言却变得很重要，从而减少了功率捕获和转子推力。当波浪存在时，应忽略边界元模型中的定常偏航效应(使用常用的倾斜轴向入流修正)，否则将导致载荷预测不佳，反映在1P(每转一次)阶段的载荷幅值增加。
The behaviour of Tidal Stream Turbines (TST) in the dynamic flow field caused by waves and rotor misalignment to the incoming flow (yaw) is currently unclear. The dynamic loading applied to the turbine could drive the structural design of the power capture and support subsystems, device size and its proximity to the water surface and sea bed. In addition, the strongly bi-directional nature of the flow encountered at many tidal energy sites may lead to devices omitting yaw drives; accepting the additional dynamic loading associated with rotor misalignment and reduced power production in return for a reduction in device capital cost. Therefore it is imperative to quantify potential unsteady rotor loads so that the TST device design accommodates the inflow conditions and avoids an unacceptable increase in maintenance action or, more seriously, suffers sudden structural failure.The experiments presented in this paper were conducted using a 1:20th scale 3-bladed horizontal axis TST at a large towing tank facility. The turbine had the capability to measure rotor thrust and torque whilst one blade was instrumented to acquire blade root strain, azimuthal position and rotational speed all at high frequency. The maximum out-of-plane bending moment was found to be as much as 9.5 times the in-plane bending moment. A maximum loading range of 175% of the median out-of-plane bending moment and 100% of the median in-plane bending moment was observed for a turbine test case with zero rotor yaw, scaled wave height of 2 m and intrinsic wave period of 12.8 s.A new tidal turbine-specific Blade-Element Momentum (BEM) numerical model has been developed to account for wave motion and yawed flow effects. This model includes a new dynamic inflow correction which is shown to be in close agreement with the measured experimental loads. The gravitational component was significant to the experimental in-plane blade bending moment and was also included in the BEM model. Steady loading on an individual blade at positive yaw angles was found to be negligible in comparison to wave loading (for the range of experiments conducted), but becomes important for the turbine rotor as a whole, reducing power capture and rotor thrust. The inclusion of steady yaw effects (using the often-applied skewed axial inflow correction) in a BEM model should be neglected when waves are present or will result in poor load prediction reflected by increased loading amplitude in the 1P (once per revolution) phase.