Research On Hydrodynamic Optimization Of Thrust-ring Pump For Hydro-generator Units

Thrust-ring-pump is a kind of extreme-low specific speed centrifugal pump with special structure integrated into hydro-generator units.The oil circulatory and cooling system with thrust-ring-pump has a lot of advantages in maintenance and compactness in structure,and it has widely been used in large and medium-sized hydro-generator units.As so far,the study for thrust-ring-pump is not perfect at home and abroad.For example,the mirror plate hole type is sole,and they are arranged at radial and backward direction in actual engineering.The hydrodynamic performance of oil bath is often ignored in actual engineering.The matching relationship between the flow passage and oil bath is considered inadequate.On another hand,the head and flow rates vary with the operation condition of hydro-generator unit and the oil circulatory and cooling system.As so far,the empirical method for thrust-ring-pump is not conducive to improve the reliability of the lubricating oil system and ensure the system run efficiently.According to the above problems,and combining with the development of the thrust-ring-pump for one large hydro-generator units.The performance prediction method was used to optimize the performance of thrust-ring-pump.The specific research contents and conclusions are as follows.1)Numerical simulation for oil circulatory and cooling system.Numerical simulation was conducted to lubricating oil system for one large hydroelectric units,and the method was verified feasible with the model test.The calculation result of lubricating oil system provides hydrodynamic performance parameters for the preliminary design of thrust-ring-pump,and the preliminary design of thrust-ring-pump is finished.The research shows that numerical simulation for lubricating oil system can supply accurate design parameters for thrust-ring-pump.2)The research object is the mirror-plate-pump.The hydrodynamic performance prediction method for thrust-ring-pump is based on multi-condition numerical simulation,and the method has been proved to be feasible by the model test.3)The optimization design for the impeller of thrust-ring-pump.The impeller is formed by punching hole in mirror plate.On the basis of the original mirror plate hole type,another five kinds of mirror plate hole type(inclined hole,folded hole,round hole)were designed.They match with the same oil bath.Numerical simulation was conducted for different combination models with positive inversion.The result shows that when the generator rotates at the single-direction,and the mirror plate holes match with the spiral oil bath,reducing outlet angle of the mirror plate hole is helpful to reducing the energy loss in the oil bath.The inlet angle of mirror plate hole has great influence on the performance of mirror-plate-pump,so the inlet angle should be chosen according to the actual situation.The mirror-plate-pump with inclined hole is the best choice for the generator rotating at the single-direction,while themirror-plate-pump with folded hole(two outlet)is the best choice for the generator rotating at the double-direction.4)The optimization design for oil bath.Based on CFD,the relationship between the hydraulic performance of thrust-ring-pump and the section shape and outlet area of oil bath is discussed.The result shows that the cross-sectional shape of oil bath has only tiny impact on the performance of mirror-plate-pump,and manufacturing process is just need to be considered for the design of oil bath.On the other hand,the outlet area of oil bath designed by existing method is too large,so if the structure allows,the total area of oil bath should be reduce properly to improve the mirror efficiency of the pump.The above research results can provide theoretical support for improving the performance of mirror-plate-pump and the security,stability,reliability of lubricating oil system and improve the design theory and method of this special centrifugal pump.