共查询到19条相似文献,搜索用时 156 毫秒
1.
2.
《可再生能源》2016,(11)
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。 相似文献
3.
4.
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。 相似文献
5.
6.
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。 相似文献
7.
8.
9.
《可再生能源》2017,(4)
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。 相似文献
10.
11.
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. 相似文献
12.
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。 相似文献
13.
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。 相似文献
14.
Hayati Olgun 《国际能源研究杂志》2000,24(11):953-964
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. 相似文献
15.
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Hp=0.0543的转轮泵作为最佳改进方案。 相似文献
16.
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。 相似文献
17.
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。 相似文献
18.
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. 相似文献