This paper attempts to solve the turbine failures reported by a hydropower station, namely, the violent vibration in the runner region under a special working condition and the blade cracking on the outlet edge near the lower ring. For this purpose, the entire flow channel of the turbine was simulated by computational fluid dynamics (CFD) on ANSYS, and the runner strength and mode of shaft assembly system (SAS) were computed by the liquid-solid coupling algorithm. The calculation results show that severe low (negative) pressure appeared on the outlet edge near the lower ring, excess stress was observed in that area, and the resonance occurred as the fifth and sixth order natural frequencies of the SAS were the same with the rotation frequencies of the blade. On this basis, the original blade was modified repeatedly. Through the modification, the flow field distribution in the runner region and the blade strength were both greatly improved, and the SAS natural frequencies were kept away from the various external excitation frequencies, laying a solid basis for the safe and stable operation of the turbine.
As high-end equipment requires a higher and higher sealing effect, sealing forms such as packing seals expose problems such as considerable wear and high heat generated by friction. Based on the theoretical analysis of the instability at the liquid-liquid interface and the pressure resistance of the seal structure, considering the rotating speed of the rotating shaft, this paper reconstructs the formula for calculating the pressure resistance value of the seal structure. On this basis, a magnetic fluid seal structure is designed for a large horizontal shaft diameter in liquid. Based on the magnetic field analysis software Maxwell, the magnetic field of the magnetic fluid seal is analyzed, and the mapping relationship between the different tooth widths of the pole teeth, the size of the permanent magnet, and the difference in the magnetic induction intensity of the seal gap is obtained. Built in the ring seal test system, the pressure test of the horizontal large shaft diameter seal structure under different rotating speeds was carried out to verify the effectiveness of the seal structure. The results have specific theoretical research significance and engineering application value for designing and applying magnetic fluid seal structures.
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