| Hydraulic turbine is the core equipment of hydropower station, its advantage and disadvantage performance has great influence to whole unit equipment. Efficiency,cavitation and stability are three important indexes of hydraulic turbine performance. Efficiency relates to utilization degree of hydropower; Cavitation relates to service lifetime of hydraulic turbine; Stability relates to safety of unit equipment normal operation. Hydraulic stability is the main factor of unit operation stability.CFD numerical simulation technology which is developed in recent years can make further research of hydraulic turbine internal flow detail structure and energy loss mechanism, fully understand internal complex flow field structure, explore actual law of water flow, and reveal the internal causes of hydraulic turbine hydraulic stability.The main function of hydraulic turbine diversion components is by least hydraulic losses to drive water flow to guide mechanism as uniformly and axial symmetry, also to make water flow had certain velocity circulation. For semi-spiral case hydraulic turbine, due to its spiral case wrap angle is small, the water flow uniformity and axial symmetry is difficult to obtain guarantee, thus may lead to make hydraulic turbine runner had force imbalance in every direction, induce unit equipment vibration, effect unit equipment operation safety and stability, meanwhile decrease hydraulic turbine work efficiency.This paper by using Fluent numerical simulation technology software had 3-D numerical simulation and analysis of semi-spiral case hydraulic turbine diversion components internal flow. Through hydraulic turbine diversion components had structure optimization, to improve uniformly and symmetry of the water flow entering runner, thus improved hydraulic turbine runner force imbalance, reached the objective for improving hydraulic turbine comprehensive performance, guaranteeing unit equipment operation safety and stability.
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