一种多浮体铰接式波浪能装置的运动分析与俘获特性研究

基于线性势流理论，利用总模态法对多浮体铰接波浪能装置“海星号”在波浪中的运动开展水动力学系数计算；然后基于矢量力学建立多浮体刚体运动学方程，并结合几何约束条件开展动态响应计算，获得最优俘获效率和最优负载阻尼；最后比较并分析“海星”波浪能装置的多浮体俘获效率，获得“海星”多浮体做功的俘获特性。研究表明：“海星”波浪能装置的多浮体四向迎波设计可拓宽装置最优俘获频带宽度，提高装置整体俘获效率；正向迎波与背向迎波俘获波浪能方式相比，小周期情况下，正向吸波浮体俘获效率较高，随着周期增大，正向吸波浮体俘获效率开始降低，背向吸波浮体俘获效率开始增大，极大周期情况下，正向吸波浮体和背向吸波浮体俘获效率趋于一致且趋近于零。     

波能利用型圆筒透空堤水动力特性实验研究

将波能装置与防波堤等海洋结构物相结合,将有助于提升其经济性,促进其应用。以一定间距平行排布多个圆筒振荡水柱装置（OWC）形成波能利用型圆筒透空堤,并基于二维波浪水槽物理模型实验对其水动力特性展开研究,重点关注筒间距、OWC吃水、波高对于波浪防护和波能转换的影响规律。结果表明：圆筒较为紧密排布时,高效波能转换的波频范围显著拓宽;较浅OWC吃水在获得近似波浪防护效果的同时波能转换性能更佳;波浪防护效果及波能转换性能受波高影响较小。波能利用型圆筒透空堤在实际应用时,应采用较小的筒间距和OWC吃水,以同时兼顾较好的波浪防护效果和波能转换性能。     

波浪能俘获装置的设计和研究

设计一种新型密封式波浪能俘获装置,浮体随波浪进行摆动,驱动浮体内摆体旋转,将波浪能转换成机械能;通过选取4种摆体的形状进行对比,选出最佳的摆体形状,并建构摆体的数学模型;利用Matlab软件对摆体在不同波浪条件下进行数值求解,之后在水动力测试平台进行模型试验。结果表明：球体是最佳的摆体形状,其装置俘获效率较高,且结构简单、成本较低,可为下一步定量优化装置提供有效的理论依据。     

Testing and control of a power take-off system for an oscillating-water-column wave energy converter

The paper concerns the development of the PTO (power take-off) control of an OWC (oscillating-water-column) spar-buoy wave energy converter. The OWC spar-buoy is an axisymmetric device consisting of a submerged vertical tail tube open at both ends, rigidly fixed to a floater that moves essentially in heave. The oscillating motion of the internal free surface relative to the floater-tube set, produced by the incident waves, makes the air flow through a novel self-rectifying air turbine: the biradial turbine. To reduce the losses of the PTO system at partial load, an electrical generator with a rated power twice the maximum expected average power conversion of the buoy was adopted. The control of the turbine-generator set under highly energetic sea-state conditions was experimentally investigated by means of tests performed in a PTO test rig. In the reported tests, the hydrodynamics of the OWC spar-buoy and the aerodynamics of the air turbine were numerically simulated in real-time and coupled with the experimental model of the turbine/electrical generator set in a hardware-in-the-loop configuration. The experimental results allowed the dynamic behaviour of the PTO to be characterized and provided validation of the proposed control algorithms that ensure operation within safe limits.     

Performance estimation of bi-directional turbines in wave energy plants

Oscillating water column(OWC)based wave energy plants have been designed with several types of bidirec-tional turbines for converting pneumatic power to shaft power.Impulse turbines with linked guide vanes andfixed guide vanes have been tested at the Indian Wave Energy plant.This was after initial experimentation withWell's turbines.In contrast to the Well's turbine which has a linear damping characteristic,impulse turbines havenon-linear damping.This has an important effect in the overall energy conversion from wave to wire.Optimizingthe wave energy plant requires a turbine with linear damping and good efficiency over a broad range of flow co-efficient.This work describes how such a design can be made using fixed guide vane impulse turbines.The In-dian Wave Energy plant is used as a case study.     

Performance of OWC wave energy converters: influence of turbine damping and tidal variability

The performance of oscillating water column (OWC) systems depends on a number of factors in a complex manner. The objective of this work is to analyse the influence of the wave conditions, the damping caused by the turbine and the tidal level on the efficiency of the conversion from wave to pneumatic energy that occurs in the OWC chamber. To achieve this, a comprehensive experimental campaign is carried out, involving in total 387 tests of a model OWC under varying wave conditions (both with regular and irregular waves), damping coefficients and tidal levels. It is found that the damping exerted by the turbine is the factor that most affects the chamber efficiency—even more than the wave conditions. It follows that a proper selection of the turbine is crucial not only to the performance of the turbine itself but also to that of the chamber, which reflects the importance of the turbine–chamber coupling in OWC systems. The next factor in order of importance is the wave period. Finally, we find that the influence of the tidal level, which is examined in this work for the first time, is significant under certain conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

A twin unidirectional impulse turbine topology for OWC based wave energy plants

Experimental results from near shore bottom standing OWC based wave energy plants in Japan and India have now been available for about a decade. Historically the weakest link in the conversion efficiency of OWC based wave energy plants built so far has been the bidirectional turbine. This is possibly because a single turbine has been required to deliver power when the plant is exposed to random incident wave excitation varying by a factor of 10. A new topology that uses twin unidirectional turbines (which features a high efficiency spanning a broad range) is proposed. Using the Indian Wave Energy plant as a case study, it is shown that the power output from such a module considerably exceeds existing optimal configurations including those based on a fixed guide vane impulse turbine, linked guide vane impulse turbine or a Well's turbine. A wave to wire efficiency of the order of 50% over the incident range is shown to be feasible in a credible manner by showing the output at all stages of the conversion process. A frequency domain technique is used to compute the OWC efficiency and a time domain approach used for the power module with the turbine pressure being the pivotal variable.     

Oscillating-water-column wave energy converters and air turbines: A review

The ocean waves are an important renewable energy resource that, if extensively exploited, may contribute significantly to the electrical energy supply of countries with coasts facing the sea. A wide variety of technologies has been proposed, studied, and in some cases tested at full size in real ocean conditions. Oscillating-water-column (OWC) devices, of fixed structure or floating, are an important class of wave energy devices. A large part of wave energy converter prototypes deployed so far into the sea are of OWC type. In an OWC, there is a fixed or floating hollow structure, open to the sea below the water surface, that traps air above the inner free-surface. Wave action alternately compresses and decompresses the trapped air which is forced to flow through a turbine coupled to a generator. The paper presents a comprehensive review of OWC technologies and air turbines. This is followed by a survey of theoretical, numerical and experimental modelling techniques of OWC converters. Reactive phase control and phase control by latching are important issues that are addressed, together with turbine rotational speed control.     

变频声波团聚超细液滴气溶胶的实验研究

声波团聚技术是细颗粒物排放控制领域极具潜力的预处理方法.为提高团聚效率,提出了变频声波团聚的新方法.以热雾机产生的超细液滴气溶胶为研究对象,进行了定频与变频声波的团聚实验并比较两种条件下的团聚效率.此外,还实验研究了变频声波各种参数对团聚效率的影响.结果表明:在实验条件为10 W声功率、30 s团聚时间的情况下,6 k...     

规则波作用下旋转浮子式波浪能捕获装置水动力试验研究

提出一种旋转浮子式波浪能捕获装置,并进行一系列物理模型试验来研究其在规则波作用下的水动力行为特性。试验研究发现：1）浮子旋转角速度随螺距的增大而减小。2）入射波周期小于2.4 s时,平均角速度随入射波周期的增加呈增大趋势;入射波周期大于2.4 s时,随着入射波周期的增加,平均角速度增幅趋缓,个别工况呈轻微减小的趋势。3）波能捕获宽度比与入射波周期基本呈正相关关系。波能捕获宽度比随螺距的减小而增大;在螺距δ=0.02、入射波周期T=2.4s时,波能捕获宽度比达到最大。最后,利用量纲分析方法,推导旋转浮子的平均角速度方程,并利用试验数据对其进行验证。     

A twin unidirectional impulse turbine topology for OWC based wave energy plants – Experimental validation and scaling

The twin unidirectional turbine topology was recently proposed with the promise of very significant improvements in the energy capture in Oscillating Water Column (OWC) based wave energy plants. Here, we present the initial results of the experimental validation of the twin unidirectional impulse turbine topology. A scale model of the concept was built and tested using simulated bidirectional flow. The model consists of two 165 mm impulse turbines each individually coupled to 375 W grid connected induction machines. An oscillatory flow test rig was used to simulate bidirectional flow to test the model. The results of the experiments validate the concept of the twin turbine configuration. The proposed topology utilizes no moving parts and achieves more than 50% efficiency over a broad range of flow coefficients. A comparison with other competing turbines (viz, a twin Wells’ turbine, a linked guide vane impulse turbine and a fixed guide vane impulse turbine) is done, based on actual measurements in the Indian wave energy plant. The results from the experiments are scaled to evaluate the design features of a 50 GWh wave energy plant.     

Multi–chamber oscillating water column wave energy converters and air turbines: A review

The oscillating water column (OWC) is a more common type of wave energy converter (WEC) that has been the subject of the study and development for several decades. Multi–chamber oscillating water column (MC–OWC) devices or arrays have the advantage of being more efficient in energy extraction compared to a single chamber system, particularly in more chaotic sea states. A variety of single and array OWC devices have been proposed and studied on a small–scale, whereas few large–scale devices have been tested under ocean wave conditions. This paper provides a concise review of the current state of MC–OWC device development in laboratory conditions. The review highlights explicitly the main stages of MC–OWC device development for one ongoing study as an example. This review was based on the available information in the literature from 2003 to 2012, in addition, further work is presented as part of the current study at the University of Technology Sydney. This study is from 2015 to 2018. The discussion shows the challenges that a device needs to overcome to be more competitive with other WECs in the global of wave energy converter area.     

Experimental investigation and ANN modeling on improved performance of an innovative method of using heave response of a non-floating object for ocean wave energy conversion

To convert wave energy into usable forms of energy by utilizing heaving body, heaving bodies (buoys) which are buoyant in nature and float on the water surface are usually used. The wave exerts excess buoyancy force on the buoy, lifting it during the approach of wave crest while the gravity pulls it down during the wave trough. A hydraulic, direct or mechanical power takeoff is used to convert this up and down motion of the buoy to produce usable forms of energy. Though using a floating buoy for harnessing wave energy is conventional, this device faces many challenges in improving the overall conversion efficiency and survivability in extreme conditions. Up to the present, no studies have been done to harness ocean waves using a non-floating object and to find out the merits and demerits of the system. In the present paper, an innovative heaving body type of wave energy converter with a non-floating object was proposed to harness waves. It was also shown that the conversion efficiency and safety of the proposed device were significantly higher than any other device proposed with floating buoy. To demonstrate the improvements, experiments were conducted with non-floating body for different dimensions and the heave response was noted. Power generation was not considered in the experiment to observe the worst case response of the heaving body. The device was modeled in artificial neural network (ANN), the heave response for various parameters were predicted, and compared with the experimental results. It was found that the ANN model could predict the heave response with an accuracy of 99%.     

Coupled 1-D stress and thermal waves in temperature dependent nonlinear elastic and viscoelastic media*

Abstract

A general analysis is formulated for the closed loop coupled thermal and displacement viscoelastic 1-D wave problem. The proper inclusion of the highly temperature sensitive viscoelastic material properties renders the problem nonlinear, even though the displacements and material properties are considered to obey linear relations. In the present article. the previous analysis is enlarged and reformulated by (a) the inclusion of nonlinear elastic and viscoelastic constitutive relations as formulated in Hilton, (b) the addition of thermal waves to the displacement waves, and by (c) temperature dependent material density and viscoelastic moduli and compliances. The wave problem studied here is of significant importance in modeling, material characterization, determination of instantaneous moduli, nonlinear analytical solution protocols and the nonlinear interaction of temperature, material properties, and wave motions. Analytical and numerical solution protocols are presented and evaluated.     

Analysis of the SEA-OWC-Clam wave energy device – Part A: Historical development,hydrodynamic and motion response formulations & solutions

The SEA-Clam wave energy device has undergone the metamorphic changes presented in the historical development. Each variation leads to more complex hydrodynamic and motion responses. The most recent novel Oscillating Water Column (OWC) form of the device has multiple internal free surfaces, the motions of which are required to predict power take-off once a device specification with structural integrity has been identified. Motion equations for structure and the large number of degrees-of-freedom of the free surfaces modelled as massless plates are derived and presented in a very compact form. This paper also proffers two simpler models consistent with standard offshore engineering calculations. These are investigated within since structural integrity of device requires further refinement; as demonstrated in the companion paper. Quality checks of the hydrodynamic analyses are explained and applied to justify the numerical investigations undertaken. Sea spectra for the possible operational site of South Uist are used to generate motion transfer functions for associated wave frequency range. The peak pitch response of this large annular shaped structure is a main concern regarding survivability. The analyses undertaken reflect conceptual rather than detailed design status of the device.     

实海况条件下磁流体波浪发电机的优化设计

以点吸收式波浪发电装置为例,考虑浮体和阻尼板在垂荡方向上的运动响应特性及磁流体发电机的发电特性,利用遗传算法优化不同规则波况下磁流体发电机的结构参数,得到装置投放于南海某岛屿附近时不同平均有效波高下的发电效率.然后,根据该岛屿全年波况的频率分布规律,计算得到全年发电量,年发电量最大时磁流体发电机结构参数最优.与传统按主...     

Numerical simulation of a submerged cylindrical wave energy converter

In this study, a numerical model based on the complete solution of the Navier–Stokes equations is proposed to predict the behavior of the submerged circular cylinder wave energy converter (WEC) subjected to highly nonlinear incident waves. The solution is obtained using a control volume approach in conjunction with the fast-fictitious-domain-method for treating the solid objects. To validate the model, the numerical results are compared with the available analytical and experimental data in various scenarios where good agreements are observed. First, the free vibrations of a solid object in different non-dimensional damping ratios and the free decay of a heaving circular cylinder on the free surface of a still water are simulated. Next, the wave energy absorption efficiency of a circular cylinder WEC calculated from the model is compared with that of the available experiments in similar conditions. The results show that tuning the converter based on the linear theory is not satisfactory when subjected to steep incident waves while the numerical wave tank (NWT) developed in the current study can be effectively employed in order to tune the converter in such conditions. The current NWT is able to predict the wave-body interactions as long as the turbulence phenomena are not important which covers a wide range of Reynolds and Keulegan-Carpenter numbers.     

Numerical modeling of the effects of wave energy converter characteristics on nearshore wave conditions

Modeled nearshore wave propagation was investigated downstream of simulated wave energy converters (WECs) to evaluate overall near- and far-field effects of WEC arrays. Model sensitivity to WEC characteristics and WEC array deployment scenarios was evaluated using a modified version of an industry standard wave model, Simulating WAves Nearshore (SWAN), which allows the incorporation of device-specific WEC characteristics to specify obstacle transmission. The sensitivity study illustrated that WEC device type and subsequently its size directly resulted in wave height variations in the lee of the WEC array. Wave heights decreased up to 30% between modeled scenarios with and without WECs for large arrays (100 devices) of relatively sizable devices (26 m in diameter) with peak power generation near to the modeled incident wave height. Other WEC types resulted in less than 15% differences in modeled wave height with and without WECs, with lesser influence for WECs less than 10 m in diameter. Wave directions and periods were largely insensitive to changes in parameters. However, additional model parameterization and analysis are required to fully explore the model sensitivity of peak wave period and mean wave direction to the varying of the parameters.     

Effects of turbine damping on performance of an impulse turbine for wave energy conversion under different sea conditions using numerical simulation techniques

This paper presents the work carried out to predict the behavior of a 0.6 m impulse turbine with fixed guide vanes with 0.6 hub to tip (H/T) ratio under real sea conditions.This enhances the earlier work done by authors on the subject by including the effects of damping applied by the turbine. Real wave data for different wave sites were used as the input data. A typical oscillating water column (OWC) geometry has been used for this simulation. Standard numerical techniques were employed to solve the non-linear behavior of the sea waves. Considering the quasi-steady assumption, uni-directional steady flow experimental data were used to simulate the turbine characteristics under irregular unsteady flow conditions. The test rotor used for this simulation consisted of 30 blades with elliptical profile with a set of symmetric, fixed guide vanes on both up-stream and down-stream sections of the rotor, with 26 vanes each. The results show that the performance of this type of turbine depends on the level of damping applied by the turbine and the prevailing wave site conditions. The objective of this paper is to predict the effects of applied damping on the behavior of impulse turbine under irregular, unsteady conditions for wave power conversion using numerical simulation.     

基于Rife法的波浪发电RBF神经网络功率优化控制

为提高不规则海况下直驱式波浪发电系统的功率捕获能力,通过建立水动力模型及直线电机模型,分析等效模拟电路共振状态,构造最优功率捕获条件;针对波浪工作环境强噪声干扰问题,采用Rife法获取波浪主导激励分量,设置等效阻尼系数,计算q轴最优期望电流跟踪值;通过设计径向基函数（RBF）神经网络PI控制,提高等效控制电流信号的跟踪精度,改善系统动态性能。仿真结果表明,所提策略对含强噪声干扰的波浪信号主频段幅值和频率预估精度高,跟踪期望电流效果好,鲁棒性强,系统输出功率优化效果显著。