轴流式潮流能发电装置导流罩水动力特性研究

以提高潮流能水轮机工作效率为目的,采用数值模拟和实验研究相结合的方法,通过改变影响导流罩水动力特性的几个关键参数,对4种不同母线线型的导流罩进行数值模拟,并初步分析开口张角对圆型导流罩水动力学性能的影响。研究结果表明:导流罩对于提高水轮机水动力学性可发挥重要作用,基于Fluent的数值模拟结果与实验值吻合较好,为轴流式潮流能发电装置导流罩的设计提供可行的方法和依据。     

导流涵道对垂直轴水轮机性能影响的研究

垂直轴水轮机作为重要的潮流能捕获装置,相比于水平轴水轮机,它具有结构简单、适应任意水流等优点,但获能效率较低。为了增大垂直轴水轮机的获能效率,文章提出了一种导流涵道装置。采用CFD方法研究了其增速性能,并探究了水轮机在导流涵道下的输出扭矩特性,最后讨论了水轮机与导流涵道之间的间距对获能效率和转矩的影响。研究表明:导流涵道在一定程度上增大了来流的速度,涵道中心处速度可增大至原来的2倍。在导流涵道作用下,水轮机转矩脉动系数减小了0.474。水轮机与导流涵道的间距对效率与转矩产生了显著的影响,当间距为0.175倍水轮机直径时,其能源利用率达到最大,同时转矩系数在0.1倍直径时降至最小。     

新型潮流能发电装置的水动力学特性模拟

为深入分析水平轴潮流能发电装置的水动力性能,文章建立了叶轮和导流罩模型,使用计算流体力学理论（CFD）和流体仿真软件FLUENT对水轮机叶轮与导流罩周围的流场分布进行模拟分析,并对3种叶片数和6种导流罩张角下的水轮机进行数值模拟,模拟结果表明：当叶片数为4,导流罩张角为25°时,水轮机输出功率与获能效率均达到了较为理想的效果。研究结果可为今后新型水平轴潮流能发电装置的结构设计与优化提供参考和依据。     

涡流发生器对潮流能水轮机叶片流动分离特性影响研究

当来流速度过大或在大攻角来流工况下,潮流能水轮机叶片边界层会发生流动分离,导致获能效率降低,甚至会使叶片发生失速破坏。针对上述问题,该文将涡流发生器（VGs）理论与水轮机叶片设计相结合,开展VGs对潮流能水轮机叶片流动分离现象的抑制机理研究。以NACA63418翼型设计的潮流能水轮机叶片为研究对象,分别建立带和不带VGs的叶片三维模型,应用CFD方法研究VGs对潮流能水轮机叶片的流动分离特性影响。结果表明：水轮机叶片流动分离主要发生在吸力侧表面叶根部分,随着流速的增大会沿叶根向叶尖径向扩展;VGs能有效减小水轮机叶片吸力侧表面分离区域,抑制流动分离现象发生;在该研究中,安装VGs后水轮机叶片整体获能性能提升明显,获能系数增加0.5%~5.0%,且能增加潮流能水轮机运行稳定性。     

柔性叶片水轮机力学性能测算方法研究

针对一种新型潮流能发电获能装置--柔性叶片水轮机,采用风浪流水槽模型试验和Fluent数值模拟两种方法测算水力学性能参数,分析了两者测算结果的差异,并通过数值模拟法测算了柔性叶片水轮机力学特性,方法简便,对柔性叶片水轮机的开发利用具有指导意义.     

实海况下流速梯度对潮流能水轮机水动力性能影响的数值研究

针对实海况条件下来流梯度,基于现场实测的流速和水深数据,对实尺度水平轴潮流能水轮机的水动力学性能进行仿真,对比水轮机在流速梯度影响下获能和轴向力变化规律。结果表明,真实潮流场中流速梯度不仅对水轮机的获能和轴向力产生影响,还会造成流场的布放水深对水轮机实际获能产生影响。同时,流速梯度造成水轮机运行时所受载荷发生动态变化,使得叶片处于不同位置时轴向力和转矩呈现周期性波动,影响叶片的获能和动力稳定性,引起振动和寿命疲劳等问题。     

水平轴潮流水轮机转轮尾流特性数值分析

针对潮流水轮机转轮尾流对机组之间水力性能的干扰问题,利用CFD分析软件Fluent对单个水平轴潮流水轮机转轮模型和10倍转轮直径间距下的两台机组模型在额定流速条件下进行三维流场的数值模拟。结果表明,在水轮机转轮旋转平面内不同半径位置处的尾流流速恢复情况明显不同,离旋转轴线越远,尾流流速恢复越快,其流速亏损也越少;当水轮机组之间串列布置,且来流方向与旋转平面垂直情况下,下游机组运行受上游机组转轮的尾流影响较大,应尽量避免该布置方式。     

单桩结构的潮流能水轮机尾流流场分析

为降低潮流能水轮机尾流效应对机组间距的影响,合理布置水轮机位置,通过数值模拟和水槽实验的方法对具有单桩支撑结构的潮流能水轮机尾流流场进行研究,在此基础上分析具有单桩支撑结构和不同安装高程对潮流能水轮机尾流流场的影响。结果显示:数值模拟与水槽试验总体上数值模拟与实验结果的趋势具有一致性;单桩结构对纵向近尾流场造成影响,会产生一个谷值突变;安装高程越高则导致沿转轮中心直线处的流速恢复越快。     

叶片材料及根部结构对潮流能水轮机性能的影响

转轮叶片材料及根部结构对潮流能水轮机水力性能和结构性能有较大影响。文章基于CFD方法对转轮直径为2 m,3种叶片根部方案的潮流能水轮机在不同来流速度工况下的水力性能进行了稳态数值模拟,计算结果表明,当来流速度为4 m/s,采用根部方案2时,机组达到最高效率73.39%。在此基础上,利用单向流固耦合的方法计算分析了该根部方案下采用4种不同材料转轮叶片的结构性能,分析结果表明,叶片采用结构钢、碳纤维HexMC和碳纤维RTP-1389时,最大应力均为130 MPa,未超过许可应力强度,结构钢最大总形变为6.55 mm,玻璃纤维最大总形变为104.72 mm。     

旋向对竖轴潮流能水轮机阵列特性的影响分析

应用竖轴水轮机阵列水动力性能预报程序研究潮流能水轮机阵列水动力干扰现象。分析单体的相对旋转方向对其自身水动力响应以及对阵列整体获能效率的影响方式、影响程度和影响规律。研究表明:反向旋转水轮机组整体获能效率明显比同向旋转对应值高,水轮机间距越小,反向旋转的优势越明显。和同向旋转相比,反向旋转转子力矩系数均值大,对应的峰值高。较之于同向旋转情况,反向旋转情况下水轮机叶片合力均值略大。     

Influence of air supply on the performance and internal flow characteristics of a cross flow turbine

This study attempts to improve the efficiency of a given type of cross flow turbine by supplying air from air suction holes. A newly developed air supply method is adopted. CFD analysis of the cross flow turbine is carried out to investigate the performance and internal flow characteristics of the turbine in detail. The air layer prevents shock loss between water flow and axis and suppresses recirculation flow in the runner passage. Hence, it is necessary to measure the amount of air layer in the runner passage and examine its effect on the performance of the cross flow turbine. The result shows that the turbine efficiency has improved more as the newly developed air supply method is applied effectively.     

水泵水轮机转轮加装短叶片前后的流动特性对比

为对比高水头水泵水轮机的转轮加装短叶片前后的能量特性及流动特性,基于SST湍流模型,选取4个具有代表性的水泵及水轮机工况,对有/无短叶片的水泵水轮机进行全流道三维定常计算。数值模拟结果表明,以水泵运行时加装短叶片可抑制脱流与漩涡等二次流现象,降低单个叶片承受的水力载荷,提高转轮进出口、导叶区及蜗壳静压,使泵获得更高的扬程。水轮机运行时添加短叶片可减小转轮出口环量,改善在尾水管内形成的复杂漩涡流,提高其水力效率。相同边界条件下,长短叶片转轮改善了转轮区的流动条件,从而提升了机组的能量特性及水力稳定性。     

多工况下高水头水泵水轮机压力脉动特性分析

为研究多工况下高水头水泵水轮机内部的压力脉动特性,以某抽水蓄能电站水泵水轮机模型为例,采用SST湍流模型对非设计工况点下的水泵水轮机进行三维全流道非定常数值模拟,同时监测了固定导叶与活动导叶间、无叶区及尾水管处的压力脉动。结果表明,对于固定导叶与活动导叶之间的区域,水轮机工况下的压力脉动主频为叶片通过频率,而水泵工况下的最高扬程和最低扬程工况的主频分别为转频和叶片数通过的频率;对于无叶区,由于受到强烈的动静干涉效应,水轮机、水泵工况下的主频均为转轮叶片数通过频率,且脉动幅值较大;对于尾水管区域,直锥段处的频率分布规律与流量有关,水轮机小流量工况下,尾水管内主要为0.3倍转频的低频压力脉动,而水轮机大流量工况下,脉动频率主要以2.6倍转频为主。     

Effect of interior guide tubes in cross‐flow turbine runner on turbine performance

The cross‐flow turbine has attracted much attention as a source of hydropower generation for small and micro‐systems, especially for low head establishments. Such turbines have a distinct advantage of lower initial and operating costs over other small scale turbines, but their efficiency is lower than others. Efficiency predictions of these turbines are generally based on the assumption that the entire flow crosses from the first stage to the second stage of the turbine runner. In this study, interior guide tubes were designed and used inside the runner of a cross‐flow turbine to collect and guide the crossing flow towards the second stage of the runner. The interior guide tubes were designed on the basis of observed flow patterns inside the runner. Experimentally, three different types of tubes were tested. The laboratory tests were conducted to calculate the turbine efficiency with different gate openings of nozzle and different positions of interior guide tubes. Results of this work with and without interior tubes have been presented in this paper. When the experiments were done with and without interior guide tubes, it has been found that turbine efficiency with the interior guide tube decreased about 5 per cent. Copyright © 2000 John Wiley & Sons, Ltd.     

基于CFD混流式水轮机上冠转轮泵结构优化研究

为研究中高水头混流式水轮机上冠转轮泵工作特性及优化可行性,以红山嘴一级电站3号水轮机为例,建立现转轮泵及11种结构优化模型,利用CFD商业软件,基于SST湍流模型对不同结构转轮泵在9种流量工况下展开数值模拟。将上冠流道泄漏水流动特性、主轴密封真空度及转轮泵效率作为研究指标,结果表明：上冠流道泄漏水流动特性依赖于转轮泵的结构类型;减小转轮泵“泵盖高度比”或斜置动泵叶对提高主轴密封真空度均有显著效果(最佳结构可提高66.9%),同时须兼顾其工作效率;额定工况下,转轮泵工作效率较低,建议转轮上冠开设合适的泄水孔补给流量提高其效率;该电站可将泵叶斜置45°、泵盖高度比H_p=0.0543的转轮泵作为最佳改进方案。     

基于正反装叶片的垂直轴潮流水轮机水动力性能分析

为了解不对称翼型叶片的正反安装对垂直轴潮流水轮机水动力性能的影响,运用CFD软件技术,建立了不对称叶片正反安装的潮流水轮机模型,分析了不对称叶片在正反两种安装方式下,叶片压力面和吸力面压力系数随叶片相位角不同而发生的变化,同时利用效率公式计算得到了效率。结果表明,叶片的正反安装对水轮机的水动力性能影响较大,当叶片正装即不对称翼型叶片凸向朝外时,垂直轴潮流水轮机效率优于叶片反装时,叶片在相位角为0°~120°区间转动时,转轮扭矩先增大后减小,在60°、180°、300°时得到最大扭矩。     

颗粒对混流式水轮机内流场及外特性的影响

为了研究颗粒对混流式水轮机内部流场和外特性的影响,采用单相和固液两相流模型对某电站的高水头混流式水轮机进行全流道非定常数值模拟,分析水轮机运行在典型工况(小流量工况、额定工况、大流量工况)时的外特性和压力脉动特性。结果表明:颗粒的存在会不同程度降低水轮机效率,平均降低1%左右。在监测点P_1(转轮与活动导叶的交界面)处,颗粒的存在不同程度增加了此处的压力脉动,小流量工况下增加幅度最大;监测点P_5(尾水管)处,小流量工况下颗粒的存在增加了此处的低频压力脉动,大流量下颗粒的存在略微削弱了此处的压力脉动幅值。     

Transient numerical analysis of rotor–stator interaction in a Francis turbine

Pressure fluctuation due to rotor–stator interaction and occurrence of vortex rope in draft tube at partial load operation are obvious phenomena in Francis type reaction hydro turbines. These hydrodynamic effects are important issues and should be addressed during the design of hydraulic machines. A 3-dimensional transient state turbulent flow simulation in the entire flow passage of a 70 kW-Francis turbine having specific speed of 203.1 is conducted to investigate the rotor–stator interaction by adopting kω based SST turbulence model. The commercial 3D Navier–Stokes CFD solver Ansys-CFX is utilized to study the flow through this vertical shaft Francis turbine in its stationary and transient passages, at 100% optimum load and 72% of part load. The investigated turbine consists of a spiral casing with 16 guide vanes, 8 stay vanes, a runner with 13 blades and a draft tube. With a time step of 2° of a rotational period of the runner for 10 full rotations, the time dependent pressure and torque variations are monitored at the selected locations during the unsteady state calculation. A periodical behavior is observed for the pressure distribution in guide vanes, runner blades and torque in the runner blades. The pressure distribution curve in runner blades reveals the two dominating frequencies – the lower peaks due to runner speed and the upper peaks corresponding to the number of guide vanes interacting with the flow. The flow acceleration toward inside of the runner is depicted by the expanding wakes behind the stay vanes. Vortex rope is observed in draft tube, downstream the runner, at part-load operation.     

Study on an Undershot Cross-Flow Water Turbine

This study aims to develop a water turbine suitable for ultra-low heads in open channels, with the end goal being the effective utilization of unutilized hydroelectric energy in agricultural water channels. We performed tests by applying a cross-flow runner to an open channel as an undershot water turbine while attempting to simplify the structure and eliminate the casing. We experimentally investigated the flow fields and performance of water tur- bines in states where the flow rate was constant for the undershot cross-flow water turbine mentioned above. In addition, we compared existing undershot water turbines with our undershot cross-flow water turbine after at- taching a bottom plate to the runner. From the results, we were able to clarify the following. Although the effec- tive head for cross-flow runners with no bottom plate was lower than those found in existing runners equipped with a bottom plate, the power output is greater in the high rotational speed range because of the high turbine ef- ficiency. Also, the runner with no bottom plate differed from rtmners that had a bottom plate in that no water was being wound up by the blades or retained between the blades, and the former received twice the flow due to the flow-through effect. As a result, the turbine efficiency was greater for runners with no bottom plate in the full ro- tational speed range compared with that found in runners that had a bottom plate.