摘要
为了研究空化流动下灯泡贯流式水轮机中叶顶间隙数值变化对其压力脉动特性的敏感性,揭示不同叶顶间隙值对灯泡贯流式水轮机非定常流动特性的影响.以某电站原型机为研究对象进行全流道数值计算和模型试验研究,用4种间隙δ变化方案对压力脉动特性进行比较.分析了叶顶间隙处的流场结构,并对数值计算结果和模型实验结果进行了对比.结果表明:文中所使用的方法可以基本反映出水轮机内部的流动情况;当空化系数开始降低时,水轮机的效率发生变化,水力性能降低,达到临界空化系数时,效率下降明显;受到空化加剧的影响,叶片背面处监测点的压力脉动幅值增加,靠近轮缘处幅值大于叶片中部和轮毂处,当局部压力降到空化压力以下时波动不再剧烈,"削波"现象产生;随着叶顶间隙值的增加,转轮间隙处空化程度加剧,空化形态由间隙空化演变为翼型空化,并出现泄漏涡空化;叶片反面轮缘处压力脉动主频与叶片转频相差不大,较大的叶顶间隙值可以有效降低轮缘处高频压力脉动,然而泄漏流动加剧会导致空化更为严重.因此,选取的叶顶间隙数值对于灯泡贯流式水轮机在稳定运行和降低振动噪声方面具有重要的意义.
In order to study the characteristics of the pmssure fluctuation of bulb tubular turbine effected by tip clearance under the cavitation flow and to reveal the various tip clearance of bulb tubular turbine influence on the unsteady flow, numerical calculation and model test wsearch prototype on whole flow passage are used to compare with pressure fluctuation characteristics on the four clearance schemes on the basis of the SST k-to turbulence model and moving mesh. Then the tip clearance of the flow field structre is analyzed and the numerical results and model experimental results which confirmed the method can basically reflect the internal flow of the turbine are compared. The results show that with the reduction of the cavitation coefficient, the energy of the water turbine characteristics change, and hydraulic performnce degraded too. And the an＇ival of the critical cavitation coefficient leads to effi- ciency to drop significantly; affected by the occunrence of cavitation intensification, pressre fluctuation amplitude is inreased in the suction side, and the nearby flange of the amplitude is greater than that in the middle part of the blade and hub. When the partial pressure drops below the saturation pressure, fluctuation is no longer violent, with the phenomenon called ＂clipping＂ appearing. With the tip clearance value and cavitation occurrences aggravating in the gap, cavitation shape evolves from a gap cavitation to an airfoil one, and then leakage vortex cavitation emerges. The rotating frequency dominates the pressure fluctuation of the nearby flange on the suction side of the blade, a larger tip clearance can reduce high frequency pressure fluctuation at the flange, leakage flow will lead to more sevms cavitation. Therfore, selecting the appropriate value gap is greatly significant to the bulb turbine in stable operation, lower vibration and noise.
作者
张毅鹏
刘梅清
吴远为
林鹏
ZHANG Yipeng;LIU Meiqing;WU Yuanwei;LIN Peng(School of Power Mechanical Engineering,Wuhan University,Wuhan 430072,Hubei,China;Hubei Key Laboratory-of Accoutrement Technique in Fluid Machinery and Power Engineering,Wuhan University,Wuhan 430072,Hubei,China)
出处
《华南理工大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2018年第4期58-66,共9页
Journal of South China University of Technology(Natural Science Edition)
基金
国家自然科学基金资助项目(51409197)
湖北省水利重点科研项目(HBSLKY201701)~~
