大型混流式水轮机宽负荷运行不稳定流动特性及控制OA

To ensure the stable operation of new power systems,conventional hydroelectric units must operate under wide-load conditions to meet frequent peak-shaving demands caused by intermittent re-newable energy output.However,traditional units were not designed for wide-load operation,resulting in severe hydraulic instability problems when operating under partial load.A Francis turbine in a large power plant was taken as the research object,using the SST k-ωturbulence model to numerically si-mulate its internal flow and pressure fluctuation characteristics under wide load conditions.The results show that when the turbine is operating below 25%opening,vortices in the runner lead to flow pattern change.Flow in the draft tube inlet hits the wall surface generating vortices and recirculation,which develop into draft tube swirls.Rotor-stator interaction(RSI)and draft tube swirls excite pressure pul-sations of 0.2,5.0,15.0 and 24.0 times the rotating frequency.An entropy production-cavitation cou-pling analysis framework is established,revealing that high entropy production zones couple with low-pressure zones at the runner outlet under 100%opening at rated head to form cavitation-sensitive re-gions,and cavitation risk limits the upper bound of stable operation.Based on flow pattern analysis,pressure pulsation characteristics and cavitation risk assessment,a dynamic determination method for wide-load stable operation ranges under multiple head conditions is proposed:the recommended stable operation ranges are determined as 50%to 70%opening under rated head and 50%to 65%opening under maximum head.