Synergistic Structural and Sediment Optimization for Enhanced Sealing and Wear Resistance in Francis Turbine Crown Relief Chambers

To ensure stable contribution of hydropower to renewable energy, enhancing long-term operation of Francis turbines under sediment-laden conditions is important. The crown pressure relief chamber often experiences performance degradation due to seal failure. This study synergistically optimized structure and sediment control, enhancing sealing and wear resistance of the upper crown pressure relief chamber. The flow field in four different crown pressure relief chambers under 72 sediment-laden conditions is simulated. Through analysis of 288 cases, the flow characteristics and wear mechanisms of sediment-laden leakage are highlighted, showing potential for structural optimization. Results show that the increase in sediment concentration or particle size significantly intensifies wear. By optimizing the crown pressure relief chamber structure, the pressure of the main shaft seal and the labyrinth seal can be reduced, and the sediment distribution pattern improved. Adding a runner pump to the crown pressure relief chamber shifts the high sediment concentration region from the labyrinth seal to the vertical annular plate, protecting the seal. To ensure sediment capture by runner pump, allowable upper limits for sediment concentration and particle size are 7 % and 0.05 mm. This work provides engineering solutions and theoretical basis for enhancing wear resistance and seal reliability in Francis turbines.