点吸收式振荡浮子水动力学影响因素研究

基于势流理论建立浮体的水动力运动方程,并以该运动方程为基础对不同外形参数的浮子进行建模仿真,研究单个振荡浮子在频域下的水动力性能.主要利用水动力分析软件AQWA分析浮子底部形状、直径、吃水和重心位置变化对浮子RAO、波浪激励力、辐射阻尼系数、附加质量等水动力参数的影响,并与最近相关文献的结果进行对比.发现圆柱底浮子的性...     

梯形摆式波能转换装置水动力性能研究

基于势流理论,采用频域方法对固定梯形摆式波能转换装置的水动力性能进行研究。由于摆式波能转换装置固有周期较长,在固有周期附近辐射阻尼系数较小,故波能转换效率并不高。在线性理论下研究波能转换装置的水动力性能时通常忽略非线性阻尼的作用,当波浪周期等于装置的固有周期且负载阻尼系数等于辐射阻尼系数时可获最大的输出功率。类似于船舶横摇,对摆式波能转换装置而言有必要考虑非线性阻尼的影响,分析非线性阻尼对最佳负载阻尼系数的影响及负载阻尼系数对摇幅及波能转换效率的影响。     

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。     

双轴铰接波浪发电装置能量吸收参数优化研究

基于三维势流理论和多体动力学方法,建立双轴铰接波浪发电装置多体水动力模型。将其能量捕获系统等效成刚度-阻尼模型,对其进行不规则波浪海况下的时域数值计算。对比不同波浪入射角、刚度和阻尼取值对波浪发电装置能量吸收的影响。结果表明:在0°~90°范围内,能量吸收功率随着波浪入射角的增大而先增大后减小,当波浪以60°方向入射时,能量吸收功率接近最大;在不同海况下,存在与之对应的最优刚度及阻尼参数取值;此外,在纵摇方向和艏摇方向设置不同的阻尼系数与刚度系数,可以使能量吸收最大化。     

波浪能装置的原理与优化设计

主要研究在波浪激励的作用下,一种波浪能装置在实际工作中的运动规律。对波浪能装置,建立了基于牛顿三大定律和胡克定律的刚体运动模型,先仅考虑了在竖直方向上的一维运动微分方程,再考虑装置的平面运动。将装置的浮子和振子视为两个刚体,每个刚体的运动可以转化为平面上的平动和转动。这2个刚体的运动规律可用6个微分方程进行描述。据装置的工况,得出微分方程的初始条件,后采用4阶Runge-Kutta方法求解微分方程,得出浮子和振子的运动规律,进而推导出稳定条件下,波浪能装置的输出功率,并且给出了在一定条件下装置输出最大功率时的阻尼系数。     

直驱式波能装置振动及转换效率分析

波浪能利用装置一般是利用振动来获取波浪能量,如鸭式装置、点吸收式装置。点吸收技术是世界上目前研究得比较热门的一类波浪能利用技术,漂浮直驱式波能装置是点吸收技术的一种。文章首先通过物理过程分析,把由双圆柱浮体构成的漂浮直驱式波浪能装置当成一个双自由度振动系统,建立系统振动方程;然后,运用势流理论求解由双圆柱浮体的垂荡辐射问题和绕射问题,求解出振动分析所需要的水动力学参数。考虑波浪能装置通过粘性阻尼吸收波浪能,利用求得的水动力学参数,设定的外部阻尼和弹簧弹性系数,可求解出此情况下水面浮体和水下浮体的相对运动幅值,进而求得装置的转换效率。给定模型尺寸参数,在一些确定的外部阻尼值和弹簧弹性系数点,分别通过变化外部阻尼和弹簧弹性系数,分析装置的振动特性以及转换效率的变化,从而在不同波况下选择适合装置的外部阻尼系数和弹簧弹性系数。     

振荡水柱式波浪能供电浮标水动力学性能研究

提出一种振荡水柱式锥形中心管波浪能供电浮标。首先，介绍浮标的结构及工作原理，其次，设计3种模型方案。建立浮标在入射波下受迫运动的数学模型，进行数值模拟计算，获得浮标在设计工况下的附加质量、阻尼系数、波浪激励力、运动响应等水动力学参数。最后，通过物理模型试验，获得各设计方案在不同周期下的俘获宽度比，并与数值计算获得的俘获宽度比进行对比分析。结果显示：不同设计方案的浮标适应不同的水深条件，设计方案中模型1的俘获宽度比最大数值为47.8%。     

漂浮式波浪能直线发电原理试验研究

介绍一种漂浮式波浪能直线发电装置,按相似理论对该装置进行模型设计和水槽试验,分析不同波高、周期、负载对该类装置输出功率和转换效率的影响。试验结果表明:阻尼匹配极大地影响到模型的转换效率。考虑到机械阻尼情况下模型从波浪到电的最大转换效率为11%,在不计机械阻尼的情况下,模型从波浪到电的最大转换效率可达49%。     

底铰摆式波能装置在斜向波中的水动力性能

采用特征函数展开和二维格林函数相结合的方法求解底铰等厚度摆式波能转换装置水动力系数及斜向规则波作用下的波浪扰动力矩。二维积分方程中奇异积分项采用复变函数解析法求解,因此同时适用于有限厚度及薄壁底铰摆板的水动力计算。通过与文献及与AQWA软件水动力计算结果的比较,验证程序的正确性。类似于船舶横摇运动,在固有周期附近粘性阻尼对摆式波能转换装置的性能有很大影响。通过在运动方程中添加粘性阻尼项考虑粘性阻尼的作用,并在此基础上给出最佳负载阻尼系数的估算公式,分析波向角和波高对装置最佳转换效率的影响。     

一种漂浮铰接式波能装置的水动力学研究

主要研究包含水面浮体和水下浮体两部分的一种铰接式波能装置。由于其外形较复杂,为了计算得到波能装置的水动力学系数和波浪激励力,采用基于三维面元法的Hydrostar软件进行水动力学计算。对铰接式波能装置进行受力分析得到装置的力学方程。最后通过适当选取弹簧弹性系数和外部阻尼系数,可求得优化的水面浮体和水下浮体的相对运动幅度以及装置的俘获宽度比。     

半潜式波浪能养殖平台与系泊系统的耦合动力分析

以“澎湖号”半潜式波浪能养殖平台为研究对象,开展养殖平台及其系泊系统在浪、流联合作用下水动力性能的研究。基于三维势流理论,应用一阶泰勒展开边界元方法对其频域水动力进行计算,研究不同浪向下平台的运动响应和二阶波浪漂移力。采用间接时域分析方法和异步耦合方法实现平台和系泊系统的时域耦合动力求解,对不同浪流组合工况下平台的时域运动与锚链张力进行分析。研究表明,在南海常规海况中平台稳定性较好,立柱间水动力干扰尤为明显,顺浪时平台所受的二阶波浪漂移力最小。在与系泊系统的耦合作用下,平台的横摇与纵摇运动受入射波浪向的影响较大,入射波波高对顺浪下的平台横摇运动和横浪与斜浪下平台纵摇运动影响明显。     

Performance analysis of axisymmetric floating energy harvesters and influences of parameters and shape variation

This paper presents a novel axisymmetric floating energy harvester associated with hydraulic cylinders and gear rack mechanism to harness wave energy. The harvester collects energy in surge, heave, and pitch modes. The mathematical models for the harvester are developed to analyze the performance and the harvested power. The Pierson‐Moskowitz two‐parameter spectrum was utilized to model the incident waves. The retardation function for the radiation force and the added mass curve are fitted based on the least squares method. The irregular exciting force, the displacement, the velocity, and the power harvesting of the axisymmetric floating energy harvesters in three motion modes with irregular waves are simulated. The effects of harvester design parameters and the geometry shape variation of the submerged part on the wave‐exciting force, the displacement, the velocity, the harvested power, and the harvesting efficiency are investigated. Under the same output damping and the same parameters with the radius of 4 m, the submerged height of 4 m, the above‐water height of 2 m, and the center of mass of ?1 m, the cylinder wave‐exciting force in surge is highest among three shapes, the cone wave‐exciting force is highest among three shapes in heave and pitch modes, and the total harvested power and the efficiency of the cylinder‐shaped harvester are the highest among three different axisymmetric shapes, which are 40.521 kW and 62.96%, respectively. The harvested power and the efficiency differences between the cylinder and the cone are 1.571 kW and 2.4%, and the differences between the cylinder and the halfsphere are 8.543 kW and 13.28%. For the cylinder‐shaped harvester with the submerged height of 4 m, the above‐water height of 2 m, and the center of mass of ?1 m, when the radius increases from 3 m to 5 m, under the optimal output damping, the total harvested power and the harvesting efficiency increase by 38.811 kW and 35.83%, respectively. For the cylinder‐shaped harvester with the radius of 4 m and the above‐water height of 2 m, as the submerged part height increases from 2 to 4 m, the total harvested power and the harvesting efficiency increase by 15.776 kW and 24.51%, respectively. For the cylinder‐shaped harvester with the radius of 4 m, the submerged height of 4 m, and the above‐water height of 2 m, as the center of mass is reduced from 0 to ?1 m, the total harvested power and the harvesting efficiency rise by 15.153 kW and 23.54%, respectively.     

直管型中心管波能模型的数值计算和实验研究

中心管波浪能模型利用浮体自身振荡运动吸收波浪能,使管内水柱产生相对运动,通过外加气动阻尼转换俘获的波浪能.运用HydroStar水动力学软件计算了直管型中心管模型在不同波况下的水动力学性能,对比分析了不同外加气动阻尼对模型俘获宽度比的影响,得到了最佳气动阻尼;研究了模型在3种不同总质量下的性能,得到了最佳响应波周期与模...     

A novel control method to maximize the energy-harvesting capability of an adjustable slope angle wave energy converter

This paper introduces a novel control approach to maximizing the output energy of an adjustable slope angle wave energy converter (ASAWEC) with oil-hydraulic power take-off. Different from typical floating-buoy WECs, the ASAWEC is capable of capturing wave energy from both heave and surge modes of wave motions. For different waves, online determination of the titling angle plays a significant role in optimizing the overall efficiency of the ASAWEC. To enhance this task, the proposed method was developed based on a learning vector quantitative neural network (LVQNN) algorithm. First, the LVQNN-based supervisor controller detects wave conditions and directly produces the optimal titling angles. Second, a so-called efficiency optimization mechanism (EOM) with a secondary controller was designed to regulate automatically the ASAWEC slope angle to the desired value sent from the supervisor controller. A prototype of the ASAWEC was fabricated and a series of simulations and experiments was performed to train the supervisor controller and validate the effectiveness of the proposed control approach with regular waves. The results indicated that the system could reach the optimal angle within 2s and subsequently, the output energy could be maximized. Compared to the performance of a system with a vertically fixed slope angle, an increase of 5% in the overall efficiency was achieved. In addition, simulations of the controlled system were performed with irregular waves to confirm the applicability of the proposed approach in practice.     

Measurements of the slow drift dynamics of a model Pelamis wave energy converter

The Pelamis wave energy converter (WEC) is moored with a clump-assisted wire catenary of high compliance that, coupled with the displacement mass of Pelamis, has a resonant frequency an order of magnitude lower than the wave frequencies. The mooring is thus decoupled from first-order wave excitation, and is excited by second-order slowly varying drift forces, which are mainly due to the wave momentum transferred to the device as wave power is absorbed. The slow drift motion is damped by a combination of drag and wave-drift damping. This paper describes an experimental investigation of the slow-drift excitation and damping.     

风力机的新型变桨距自抗扰控制系统

采用高速浮点 TMS320F28335(DSP)芯片作为硬件核心控制器,运用自抗扰控制系统算法对风力机桨距角进行精确调整,实现了一种由新型软硬件相结合的风力机变桨距控制系统.结果表明:当风速高于额定风速或者瞬时输出功率大于额定功率时,通过对桨叶桨距角的精确调整,可使输出功率动态维持在额定功率附近.变桨距自抗扰控制系统算法实现简单,具有良好的动态响应特性,能有效保障风力机的安全运行.     

结合防波堤的振荡摇摆式波浪能装置试验研究

讨论一种结合防波堤的振荡摇摆式波浪能装置的结构和工作原理,并在河海大学河口航道综合试验厅进行物理模型试验。试验以重块和不锈钢板间的摩擦力作为波浪能转换装置的负载阻尼,通过测量不锈钢板两端的拉力及其位移计算波浪能转换输出功率。结果表明,当入射波的周期和浮体的固有周期接近时,浮体的运动接近共振状态,此时波浪能转换平均输出功率和转换效率最高,分别可达0.05 W和17.9%。入射波周期较大时,装置的波浪能转换输出功率较高,但此时其波浪能转换效率低于入射波周期较小时。水深对于浮体的姿态和运动特性起到关键作用,结果表明水深为60 cm时波浪能转换输出功率和转换效率最高。     

Model predictive control of sea wave energy converters – Part II: The case of an array of devices

This paper addresses model predictive control (MPC) of highly-coupled clusters of sea wave energy converters (WECs). Since each WEC is not only a wave absorber but also a wave generator, the motion of each WEC can be affected by the waves generated by its adjacent WECs when they are close to each other. A distributed MPC strategy is developed to maximize the energy output of the whole array and guarantee the safe operation of all the WECs with a reasonable computational load. The system for an array is partitioned into subsystems and each subsystem is controlled by a local MPC controller. The local MPC controllers run cooperatively by transmitting information to each other. Within one sampling period, each MPC controller performs optimizations iteratively so that a global optimization for the whole array can be approximated. The computational burden for the whole array is also distributed to the local controllers. A numerical simulation demonstrates the efficacy of the proposed control strategy. For the WECs operating under constraints explored, it is found that the optimized power output is an increasing function of degree of WEC–WEC coupling. Increases in power of up to 20% were achieved using realistic ranges of parameters with respect to the uncoupled case.     

鹰式二号波浪能装置的频域动态响应计算与负载优化设计

以鹰式二号波浪能发电装置为研究对象,基于捕获宽度达到最优为准则,通过对波浪中运动的装置建立频域运动方程,计算装置运动模态响应、获得最优负载阻尼和主要结构点受力等设计要素,并根据万山岛海域波浪条件开展能量转换系统负载设计、提供结构强度设计支持数据等。研究结果表明:在不同波况下装置获得捕获宽度对应的最优阻尼也不同;鹰式二号波浪能装置对于周期约2 s小周期波浪也具有良好的响应,捕获宽度达50%以上,在主要设计波况3~6 s最高捕获宽度达到300%,在万山岛海域波浪能试验场波况最高捕获宽度达到200%。