Increasing the Life of Marine Turbines by Design and Innovation

由于近海海洋环境中的高密度水和高度不稳定，潮汐涡轮机上的非稳定负荷比风力涡轮机上的大得多。此外，通常用于支撑船用涡轮机的焊接软钢结构在盐水中的疲劳寿命较低。这可能导致寿命为30个月或更短，而不是设计要求的30年。此外，疲劳寿命限制了潮汐涡轮机可以部署的地点的数量，从而限制了英国实际的总体潮汐资源。该项目旨在开发创新技术，以减少由流动不稳定引起的非定常载荷，从而将船用涡轮机的寿命提高一个数量级。第一种是使用创新的液压传动系统，由英国开发，以减少由较长的非稳定“阵风”所产生的非稳定载荷，这些阵风的大小大于机器直径。液压传动系统可以使涡轮机的速度对“阵风”做出快速反应，确保机器上的负载保持不变。第二项创新技术旨在减少由小于机器直径的短时非定常“阵风”产生的非定常载荷。这项技术类似于飞机上使用的技术，即当机翼受到一股空气“阵风”袭击时，阻止飞机升力的突然变化。这项技术利用机翼上的“扰流板”、“流体喷射”或“襟翼”，在“阵风”掠过时自动保持叶片升力恒定。这项技术将应用于潮汐涡轮叶片，以减少由于短尺度非定常“阵风”造成的非定常载荷。一旦开发出来，这第二项技术也可以用来替代变桨距机构，以避免超过峰值负荷。项目方法将是使用喷气发动机行业开发的实验测试和计算模型，以了解海洋环境的不稳定如何导致涡轮负荷不稳定。描述涡轮机对非恒定流响应的简化模型将在一些英国潮汐涡轮机公司的潮汐涡轮机设计规范中实施。这将提高英国潮汐涡轮机行业预测水流不稳定影响的能力。实验和计算将用于开发用于阵风负荷控制的新的自动扰流板和襟翼控制系统。该控制系统与创新的液压传动系统模型将在潮汐涡轮机设计规范中实施。这将使非定常减载系统的成功被模拟。目前公布的海洋湍流测量在空间和时间分辨率上都是有限的。对这项研究来说，获得改进的测量结果是很重要的。项目成员将与该项目中的潮汐涡轮机公司合作，并与SuperGen合作伙伴合作，以提高可用测量的分辨率。开发了一种使用传统声学多普勒设备的新方法，如有必要，将在该项目中使用该方法以实现更高的测量分辨率。最后，非定常减载系统和液压传动系统将被纳入潮汐涡轮机的比例模型中，并将在水槽中进行测试。试验将在海洋环境特有的水流不稳定条件下进行。这些测试将决定该项目能否成功地实现非稳态减载。减载系统成功应用于全尺寸潮汐涡轮机将在延长维护期和延长使用寿命方面带来好处。此外，随着涡轮机对其环境运行条件的敏感性降低，更多的潮汐发电站将成为可行的发电地点，从而增加英国的潮汐资源。

Unsteady loads on tidal turbines are much larger than in wind turbines because of the high density of water and the high levels of unsteadiness in offshore marine environments. In addition the welded mild steel structures normally used to support marine turbines have a low fatigue life in salt water. This can lead to life of 30 months or less instead of the design requirement of 30 years. In addition fatigue life limits the number of locations where tidal turbine can be deployed, limiting the overall practical UK tidal resource. This project aims to develop innovative technologies which will reduce the unsteady loads which result from flow unsteadiness and thus increase the longevity of a marine turbine by an order of magnitude.Two technologies will be developed. The first uses innovative hydraulic drive trains, developed in the UK, to reduce the unsteady loads created by large length unsteady 'gusts', those larger in size than the machine diameter. The hydraulic drive train allows the speed of the turbine to respond quickly to the 'gust' ensuring that the load on the machine remains constant. The second innovative technology is designed to reduce the unsteady loads created by short length unsteady 'gusts', those smaller than the machine diameter. The technology is similar to that used in aircraft to stop sudden changes in aircraft lift as the wing is hit by an air 'gust'. The technology uses 'spoilers', 'fluid ejection' or 'flaps' on the wing to automatically hold the blade lift constant as the 'gust' moves over it. This technology will be employed on tidal turbine blades to reduce unsteady loading due to short length scale unsteady 'gusts'. Once developed this second technology could also be used as an alternative to variable pitch mechanisms to avoid peak loads being exceeded.The project approach will be to use experimental testing and computational modelling developed in the jet engine industry to understand how the unsteadiness in marine environment resulted in unsteady turbine loading. A simplified model describing the turbine response to unsteady flow will then be implemented in the tidal turbine design code of a number of UK tidal turbine companies. This will improve the UK tidal turbine industries capability to predict the effect of flow unsteadiness.Experiments and computation will be used to develop the new automated 'spoiler' and 'flap' control system for gust loading control. This control system in conjunction with a model for the innovative hydraulic drive train will be implemented in the tidal turbine design codes. This will allow the success of the unsteady load reduction systems to be modelled.Current published measurements of sea turbulence are limited in both their spatial and temporal resolution. It is important to this study that improved measurements are obtained. The project members will work in collaboration with the tidal turbines companies partnered in this project, and with the Supergen partners, to improve the resolution of the available measurements. A new method of using conventional acoustic doppler equipment has been developed and if necessary this will be used in the project to achieve improved measurement resolution.Finally the unsteady load reduction systems and the hydraulic drive train will be incorporated into a scale model of the tidal turbine and this will be tested in a water flume. The tests will be undertaken with flow unsteadiness characteristic of the marine environment. These tests will determine the project's success in achieving an unsteady load reduction.Successful application of the load reduction systems to full scale tidal turbines will provide benefits in terms of extended maintenance periods and increased service life. Furthermore as turbines become less sensitive to their environmental operating conditions a larger number of tidal sites will become available as viable for producing power thereby increasing the UK tidal resource.