水力发电学报2025，Vol.44Issue(10)：121-132,12.DOI:10.11660/slfdxb.20251011
混流式水轮机尾水管特殊压力脉动试验及分析
Experimental tests and analysis on special pressure pulsations in draft tube of Francis turbine
摘要
Abstract
Spiral vortex ropes in the draft tube under certain partial load conditions could be frequently observed in the model tests of Francis turbines.In addition to typical vortex rope rotation frequencies fv,pressure signals recorded at the draft tube wall monitor points often exhibit the rotational frequency fn and its higher-order harmonics(1～5)fn as distinct spectral components.Under certain operating conditions,these special frequency components show significant amplitudes,yet their underlying generation mechanisms remain controversial.This study examines the internal flow characteristics of a Francis turbine operating under typical vortex rope conditions.By combining the data from high-speed imaging with pressure fluctuation measurements,this study presents a systematic analysis on the effects of unit discharge,unit speed,and cavitation number on the vortex rope structure and pressure pulsation characteristics,focusing on analyzing the possible sources of the harmonics(1～5)fn.The results indicate that unit discharge significantly influences the amplitude of the vortex rope rotation at fv when the spiral vortex rope is visible,pressure pulsation amplitudes at fv increase substantially.In contrast,weaker effects of cavitation number and unit speed are cast on the amplitude at fv.Additionally,under certain specific conditions,a slender and stable cavitating spiral vortex rope forms in the draft tube,where the amplitude at fn sharply increases.This phenomenon is believed to be closely related to hydraulic system resonance triggered by this cavitating rope.The special harmonics at(1～5)fn are likely attributed to the elliptical cross-section of the vortex rope and its self-rotation,which is characterized by frequencies close to(1～5)fn.关键词
混流式水轮机/压力脉动试验/空化/涡带频率/转频Key words
Francis turbine/pressure pulsation test/cavitation/vortex frequency/rotational frequency分类
建筑与水利引用本文复制引用
周凌九,庞嘉扬,程宦,康文喆,陈泓宇,王正伟..混流式水轮机尾水管特殊压力脉动试验及分析[J].水力发电学报,2025,44(10):121-132,12.基金项目
国家自然科学基金面上项目(52479091) （52479091）
