Comparison of Pile-Soil-Structure Interaction Modeling Techniques for A 10-MW Large-Scale Monopile Wind Turbine Model Under Wind and Wave Conditions

Considering the large diameter effect of piles,the influence of different pile-soil analysis methods on the design of monopile foundations for offshore wind turbines has become an urgent problem to be solved.Three different pile-soil models were used to study a large 10 MW monopile wind turbine.By modeling the three models in the SACS software,this paper analyzed the motion response of the overall structure under the conditions of wind and waves.According to the given working conditions,this paper concludes that under the condition of independent wind,the average value of the tower top x-displacement of the rigid connection method is the smalle st,and the standard deviation is the smallest under the condition of independent wave.The results obtained by the p-y curve method are the most conservative.

Towing characteristics of large-scale composite bucket foundation for offshore wind turbines

In order to study the towing dynamic properties of the large-scale composite bucket foundation the hydrodynamic software MOSES is used to simulate the dynamic motion of the foundation towed to the construction site.The MOSES model with the prototype size is established as the water draft of 5 and 6 m under the environmental conditions on site.The related factors such as towing force displacement towing accelerations in six degrees of freedom of the bucket foundation and air pressures inside the bucket are analyzed in detail.In addition the towing point and wave conditions are set as the critical factors to simulate the limit conditions of the stable dynamic characteristics.The results show that the large-scale composite bucket foundation with reasonable subdivisions inside the bucket has the satisfying floating stability.During the towing process the air pressures inside the bucket obviously change little and it is found that the towing point at the waterline is the most optimal choice.The characteristics of the foundation with the self-floating towing technique are competitive for saving lots of cost with few of the expensive types of equipment required during the towing transportation.

Videometric research on deformation measurement of large-scale wind turbine blades

Utilization of wind energy is a promising way to generate power,and wind turbine blades play a key role in collecting the wind energy effectively.This paper attempts to measure the deformation parameter of wind turbine blades in mechanics experiments using a videometric method. In view that the blades experience small buckling deformation and large integral deformation simultaneously, we proposed a parallel network measurement(PNM) method including the key techniques such as camera network construction,camera calibration,distortion correction,the semi-automatic high-precision extraction of targets,coordinate systems unification,and bundle adjustment,etc. The relatively convenient construction method of the measuring system can provide an abundant measuring content,a wide measuring range and post processing.The experimental results show that the accuracy of the integral deformation measurement is higher than 0.5 mm and that of the buckling deformation measurement higher than 0.1mm.

Numerical Simulation of Pressure Fluctuations in a Large Francis Turbine Runner

The pressure fluctuation caused by unsteady flow in runner is one of the main reasons of vibration for a large Francis hydraulic turbine. It directly affects the steady operation of the hydraulic turbine unit. The existing research of the pressure fluctuation in hydraulic turbine mainly focuses on the unsteady flow in draft tube. Accurate distribution of pressure fluctuations inside a runner is not very clear. In this paper, the numerical method for predicting the pressure fluctuations in runner is investigated and the numerical simulation is performed for a large Francis hydraulic turbine. It is proved that the combination of shear-stress transport（SST） k-o） turbulence model and pressure-implicit with splitting of operators（PISO） algorithm could give more reliable prediction of pressure fluctuations in runner. The frequencies of pressure fluctuations in runner are affected by the flow in guide vane and the flow in draft tube The first dominant frequency is significantly determined by the flow in draft tube, especially at part load condition. This frequency is approximately equal to one-third of the runner rotating frequency. The evident second dominant frequency is exactly equal to the guide vane passing frequency. The peak-to-peak amplitudes of pressure fluctuations in runner at small guide vane open angle are larger than that at large open angle at the same operating head. The amplitudes at points on blade pressure surface are generally greater than that on suction surface. The research results could be used to direct the hydraulic design and operation stability improvement of a large Francis hydraulic turbine.

Numerical simulation of cavitation turbulence in Francis turbine runner with splitter blades

Cavitation will reduce the turbine performance and even damage the turbine components.To verify the effects of splitter blades on improving the cavitation performance,the cavitation flow inside a Francis turbine runner with splitter blades was numerically simulated by using the Singhal cavitation model and the standard k-ε turbulence model.The distributions of static pressure and gas volume fractions on the surface of the runner blades were predicated under different conditions,and the cavitation in the flow field of the runner was analyzed.The results show that the static pressure and gas volume fractions are more uniformly distributed on the short blades than those on the long blades in Francis turbines with splitter blades,and there is almost no cavitation on the short blades;their distributions are more uniform under small flow conditions than those under large flow conditions;and large gas volume fractions are concentrated at the outlet tip near the band on the suction side of the long blade.The installation of splitter blades can improve the cavitation performance of conventional Francis turbines.

Optimization of Blade Geometry of Savonius Hydrokinetic Turbine Based onGenetic Algorithm

Savonius hydrokinetic turbine is a kind of turbine set which is suitable for low-velocity conditions.Unlike conventional turbines,Savonius turbines employ S-shaped blades and have simple internal structures.Therefore,there is a large space for optimizing the blade geometry.In this study,computational fluid dynamics(CFD)numerical simulation and genetic algorithm(GA)were used for the optimal design.The optimization strategies and methods were determined by comparing the results calculated by CFD with the experimental results.The weighted objective function was constructed with the maximum power coefficient Cp and the high-power coefficient range R under multiple working conditions.GA helps to find the optimal individual of the objective function.Compared the optimal scheme with the initial scheme,the overlap ratioβincreased from 0.2 to 0.202,and the clearance ratioεincreased from 0 to 0.179,the blade circumferential angleγincreased from 0°to 27°,the blade shape extended more towards the spindle.The overall power of Savonius turbines was maintained at a high level over 22%,R also increased from 0.73 to 1.02.In comparison with the initial scheme,the energy loss of the optimal scheme at high blade tip speed is greatly reduced,and this reduction is closely related to the optimization of blade geometry.As R becomes larger,Savonius turbines can adapt to the overall working conditions and meet the needs of its work in low flow rate conditions.The results of this paper can be used as a reference for the hydrodynamic optimization of Savonius turbine runners.

New Bulb Turbine with Counter-rotating Tandem-runner

With the increasing demand for the clean sustainable power, the turbine design urgently turns to increase the capability significantly toward higher head for generating larger power. Currently, there are many studies in the field of the bulb turbine with single-stage runner, though reports about counter-rotating tandem-runner are rare. However, the further high-head application with the single-stage runner is very difficult to achieve due to the limit of the specific speed. In this paper, a new bulb turbine with the tandem-runner is designed in order to substantially increase the applicable limit toward higher head with larger power. A half of the net head is absorbed by the frontal runner which can generate output power, while the remaining half is absorbed by the rear runner. To generate the Euler energy required for the rear runner, the frontal runner has the counter-rotation against the rear runner so that the counter-rotating tandem-runner can meet the purpose of double head and power under the same size as the conventional bulb turbine. Supply and demand of Euler energy between the two runners are thoroughly optimized through the detailed flow analysis, in order to secure the stable operation. As a result, the interference of Euler energies between the outflow from the frontal runner and the inflow to the rear runner is confirmed to be very small on the counter-rotating interface between the two runners. The prediction method of on-cam performance between the two adjustable runners is also developed numerically, which provides optimal flow between the two runners. This research provides a theoretical basis for the optimal design and operation of the counter-rotating tandem-runner bulb turbines.

Giant Hydraulic Turbine Runner under construction

Four giant hydraulic turbines of Yantan Hydropower Sta-tion located on the Hongshui River,Guangxi Provinceare now under construction by the Harbin Electric Machinery Works(HEMW)of China Harbin Power-Plant Equipment Corporation(GROUP).The turbine will become the largest in dimension forFrancis type turbine ever made in China.The external diameter ofthe runner is 8.6 m,which is supposed to be ranked No.3 among thelargest runners of this category in the world.Each turbine is

Dynamic Simulation on Collision Between Ship and Offshore Wind Turbine

By using ABAQUS/Explicit, the dynamic process of an offshore wind turbine(OWT) stricken by a ship of 5000DWT in the front direction is simulated. The OWT is located on a large-scale prestressing bucket foundation constructed by an integrated installation technique. According to the simulation results, under the ship collision, a certain range of plastic zone appears within a local area of arc transition structure of the bucket foundation, and the concrete plastic zone is seriously damaged. As the stress level of OWT tower is relatively low, the OWT tower is less affected. A great inertial force is generated at the top of the OWT tower as the mass of nacelle and blades is up to 400 t. The displacement of the tower is in the opposite direction of the ship collision at the end of 1 s under the action of inertial force. There is only a minor damage in the ship bow. Most of the kinetic energy is transformed into the plastic dissipation and absorbed by the arc transition structure of bucket foundation.

Experimental study of rotating wind turbine breakdown characteristics in large scale air gaps

When a wind turbine is struck by lightning,its blades are usually rotating.The effect of blade rotation on a turbine＇s ability to trigger a lightning strike is unclear.Therefore,an arching electrode was used in a wind turbine lightning discharge test to investigate the difference in lightning triggering ability when blades are rotating and stationary.A negative polarity switching waveform of 250/2500 μs was applied to the arching electrode and the up-and-down method was used to calculate the 50%discharge voltage.Lightning discharge tests of a 1：30 scale wind turbine model with 2,4,and 6 m air gaps were performed and the discharge process was observed.The experimental results demonstrated that when a 2 m air gap was used,the breakdown voltage increased as the blade speed was increased,but when the gap length was 4 m or longer,the trend was reversed and the breakdown voltage decreased.The analysis revealed that the rotation of the blades changes the charge distribution in the blade-tip region,promotes upward leader development on the blade tip,and decreases the breakdown voltage.Thus,the blade rotation of a wind turbine increases its ability to trigger lightning strikes.

Improving the Energy Performance of a High-Pressure Hydraulic Turbine by Researching the Flow in the Flow Part

In this study, the goal is to increase the efficiency of a high-pressure hydraulic turbine. The goal is achieved by numerical flow simulation using CFX-TASCflow. This approach reduces costs and time compared to the experimental approach and allows for improving the turbine productivity and its design. The analysis of energy losses in the flow part of the turbine Fr500, as well as the analysis of the influence of the opening of the guide vanes on changes in energy losses. The results showed that the greatest losses occur in the guide vane 3.02% based on the two-dimensional model and 2.5% based on the 3D model, which significantly affects the efficiency. The analysis was carried out using programs for calculating fluid flow in two-dimensional and three-dimensional formulations. With the help of the study, the main energy problem is solved—increasing efficiency.

基于MRD优化布置的水轮发电机组碰摩系统振动抑制

针对水轮发电机组转子-转轮系统碰摩故障问题,采用磁流变液阻尼器(magneto-rheological damper,MRD)对轴系振动进行抑制,旨在探究MRD对机组轴系振动的影响规律及其对系统碰摩故障的抑制效果。首先,将机组轴向位置函数引入MRD非线性动力学模型,推导了碰摩故障下含轴向分布参数的MRD-转子-转轮系统动力学方程。其次,基于数值模拟方法,以机组转速为控制参数对比分析了是否考虑MRD的转子-转轮系统非线性动力学行为。最后,研究了不同MRD轴向布置参数对碰摩转子-转轮系统动力学行为的影响。研究结果表明:MRD的加入对转子、转轮非稳态运动具有良好约束作用,能够显著减小转子、转轮振动幅值,有效避免了机组轴系碰摩故障的发生;当阻尼器位置参数s_(1)、s_(2)分别取0.25与0.95时,MRD对系统的减振效果最佳。通过在机组轴系合理布置MRD,可有效改善系统振动情况,从而为水轮发电机组振动控制提供有益指导。

1000 MW水轮机转轮径向安装偏差对流动特征的影响

本文以百万千瓦混流机组为研究对象,使用ANSYS软件进行三维全流道稳态数值分析。探究在额定工况下,当转轮出现Y轴负方向0.1 mm、0.3 mm、0.5 mm、1.5 mm、2.5 mm的径向安装偏差时,间隙分布不均匀对于百万千瓦大型水轮机组内部流动特征的影响。研究发现,在一定偏差数值内,随着间隙的减小,该区域压力逐渐上升,但超过该数值以后,流体无法流入则变为了低压区。另外,上冠腔和下环腔均出现了相同数量的旋涡演变周期,但旋涡的发生位置不同,上冠腔旋涡较剧烈,且数量与叶片数呈非整数倍关系。最后阐明了下环腔内壁面受到的旋涡流动冲击程度要大于上冠腔内壁面。因此,本研究可以应用于其他大中型混流式水轮机的设计与安装,对于提高水轮机运行质量、降低运行成本和提高水电站效益具有重要意义。

喷针开度对冲击式水轮机转轮水力性能影响研究

冲击式水轮机是一种适用于中高水头段水力资源开发的流体机械,在我国西南地区高水头水力资源的开发中有着广阔的应用前景。本文以西藏紫霞水电站冲击式水轮机模型机转轮为研究对象,在5个不同的喷针开度下分别进行了转轮内部三维非定常多相流动数值模拟,分析了喷针开度对转轮水力性能与内部流动特性的的影响。预测结果显示转轮水力效率随开度上升而先上升后下降,在设计开度下水力效率最优。在0.75~1.60倍设计流量区间中,转轮水力效率的变化幅度小于1%。根据3个典型开度下转轮水斗内部非定常流动过程的对比分析,发现大开度工况时,水斗缺口处会发生水膜流的漏流现象,喷针开度越大时的泄漏量也越大,从水斗缺口处的漏流现象是其水力损失加剧的主要流动原因。研究为紫霞水电站230 MW大型冲击式水轮转轮水斗的水力优化设计提供了重要参考。

抽水蓄能机组水轮机工况启动过程转轮动应力特性

本文以某原型水泵水轮机组为研究对象,研究了水轮机工况启动过程中外特性的动态变化曲线,重点分析水泵水轮机转轮内流场和动应力特性。研究结果表明,在水轮机工况启动过程中,转轮扭矩呈先上升后下降的趋势,在转速达到额定值时,扭矩接近于0;流量受到导叶开度的影响非常明显,处于先上升后下降趋势;水头在430~480m左右波动。随着转速的增加,转轮流固耦合面上的整体压力值显著增加。高压区起始集中在转轮进水边的压力面一侧,随着时间的推移,高压区域逐渐扩大并移动到进水边的吸力面一侧。转轮进水边与下环交接处的应力呈现先下降后上升的趋势,应力均值下降的同时,峰峰值也有所下降,应力值一直处于较低的水平。转轮进水边与上冠交接处的应力呈现上升趋势,并与转轮转速的变化趋势一致。本文对于深入理解水泵水轮机组启动过程复杂条件下的内部流动和转轮动应力特性具有重要参考价值。

超大容量水斗式水轮机水力特性数值模拟分析

为满足超高水头、超大容量水电站建设需求,提出了一种额定水头1000 m,单机容量接近800 MW的三转轮立轴串联水斗式水轮机方案。阐明了这种通过增多转轮来增大容量的设计理念和结构组成,给出了方案的理论设计参数,并应用CFD模拟预测了其水力特性、分析和优化转轮及转轮室流态。研究表明:三转轮水斗式水轮机的额定工况效率可达87%,工作特性曲线变化平稳。转轮室溅水干扰是影响效率的主要因素。通过优化各层转轮相对位置和喷嘴方位,可一定程度提高效率,减小力矩振荡,保证出力稳定。此初步尝试证明了概念的可行性,也发现溅水优化的重要性,能为后续优化研究提供参考。

大型混流式水轮机转轮应力研究综述

混流式水轮机转轮的裂纹问题,降低了转轮的使用寿命,给机组运行带来了安全隐患,也是制约大型机组宽域运行的主要因素之一。混流式水轮机在低负荷工况的水力稳定性,决定了其运行的安全稳定范围。而叶片裂纹的产生及发展,与叶片在不同工况下的应力特性密切相关。本文总结了混流式水轮机裂纹出现的不同原因,分析了裂纹处理及预防的不同案例,详细对比了三种转轮应力研究方法的不同,最终对大型混流式水轮机转轮应力的研究前景做了总结和展望。

不同水头下抽水蓄能电站标准化设想与分析

为满足抽水蓄能大规模快速发展的要求,解决抽水蓄能设备供应不足等系列问题,分析了我国抽水蓄能设备标准化的难点,从我国抽水蓄能电站运行设备的参数统计规律分析出发,提出了常规叶片与长短叶片相结合的方式,实现抽水蓄能水泵水轮机转轮尺寸标准化的构想。根据水力学基本公式,论述了不同水头下抽水蓄能电站水泵水轮机转速、转轮直径标准化的机理,分析了水泵水轮机转轮标准化的优缺点。在此基础上,提出了抽水蓄能电站机电设备、厂房等的标准化整体架构。研究结果对我国抽水蓄能的标准化工作具有重要意义。

基于Moldflow优化的计算机CPU涡轮风扇模具设计

结合CPU涡轮风扇的注射成型要求,采用CAE辅助分析优化得到了塑件的成型方案为1模1腔、正面中心轴顶端进浇模腔布局,单点热嘴环形热浇口浇注。利用分层抽芯的方法将单个涡轮叶槽的脱模采用上、中、下3层滑块的顺序实施抽芯的方法进行侧抽芯脱模,从而得到整个涡轮风扇叶槽的所需脱模机构为27个滑块机构,分别为上层9个上滑块机构、中层9个中滑块机构、下层9个下滑块机构。根据滑块机构的抽芯驱动需要,将模具的整体结构采用一种假三板模结构,分3次开模,第一次开模用作下层9个滑块机构的侧抽芯驱动;第二次开模用作上层9个滑块机构的侧抽芯驱动;第三次开模用作塑件的完全脱模,第三次开模打开后,随着中层9个油缸驱动9个中滑块侧抽芯动作的完成,塑件自动脱落而实现完全脱模。结合涡轮风扇叶槽难以脱模的实践难题,设计了3层滑块机构按序抽芯,根据模具开模提供的驱动进行设计,有效地解决了涡轮风扇塑件的成型难题,机构动作可靠,生产效率较高。

基于空化烈度的水轮机转轮叶片空化诊断研究

水电机组运行过程中出现的空化会侵蚀过流部件,加剧振动,降低机组效率并影响机组的稳定性,因此对机组空化进行诊断对安全稳定运行十分重要。空化辐射能量信号是宽频带信号,但常规方法仅监测某一特征频率或频带,难以实现空化准确监测,为此提出基于空化烈度开展水轮机转轮叶片空化监测。首先从监测原理出发,对比分析空化对频域能量分布特性的影响,提出采用空化烈度表征空化强弱的程度;然后基于空化机理和水轮机试验数据,提出判定空化发生与否的数学模型;最后开展水轮机空化台架试验,验证所提监测指标的有效性。结果表明:空化会导致高频带成分占比增加,基于高低频能量面积比构造的空化烈度指标能够有效判别出空化的发生及强弱,台架试验判定准确率达100%。研究结果可为水下机构空化等故障的检测提供理论依据。