| This paper focused on finding the factors which causing and influencing the bulb tubular hydroelectric Generating Units' vibration,so one hydropower was selected as an object of stability study.The possible reasons that may cause the vibration of turbine was analyzed and these unstable factors were researched by the model test,the real machine test and the numerical analysis.In the pressure fluctuation model test,+ X and-X were two measuring points that were located in the place which is about 0.4 times runner diameter from draft tube inlet section in horizontal position.The operating conditions were chosen as the coordination points whose blade openings were 24.9o,33.7o and heads were 3.1m,6.8m,7.68 m,8.34 m and 10 m respectively.The model tests obtained the pressure fluctuation performance curves in +X and–X measuring points.The results show that double-amplitude maximum is less than the design requirement value 7%.The main hydroelectric vibration is the high frequency pressure fluctuation.In the real machine test,the vibration was supervised and analyzed according to three aspects of the hydraulic factors,mechanical factors and electrical factors.(1)the draft tube pressure fluctuation of different blade opening on the 8m head;(2)the shafting vibration and swing;(3)the spindle bending;(4)the spindle turning;(5)the spindle attitude;(6)the guide bearing clearance;(7)the unit mass unbalanced;(8)the magnetic pull unbalanced;(9)the unit electrical parameters(10)the generator air gap;(11)the rotor out-of-roundness;(12)the rotor pole elongation influencing factors;(13)the rotor elasticity and flexibility.The results indicate that the rotor-stator interaction between the runner and stationary components is the main reason which causing the draft tube pressure fluctuation.There are low frequency vibration which is caused by hydraulic factors and high frequency vibration which is caused by stator base vibration at the bulb body +Y.The first frequency is 4X low frequency vibration which is caused by the water pressure fluctuation in the runner chamber.The slot jet impingement is the main reason which caused the penetrative cracks.The unbalanced magnetic pull was one of the factors which causing the units' vibration.The rotor pole elongation is mainly caused by magnetic pull.In the CFD numerical analysis,the operating head was 8m.The calculation included two parts: steady and unsteady.The CFD numerical analysis results indicate that the rotor-stator interaction between the runner and non-rotatable parts is the main factor which caused hydroelectric generating units' vibration.It was diagnosed that blades make negative contribution to shaft power and occur flow separation zones.It was diagnosed that all kinds of vortexes which caused the flow field unstable factors.The vortexes includes guide vane import vortex,guide vane tip vortex,guide vane wake vortex,blade inlet and outlet vortex,blade tip vortex,blade wake vortex,draft tube karman vortex streets and Secondary return of draft tube.Finally,three research methods were contrasted and analysed about the pressure fluctuation test.It is determined that the design requirements are complied with about the units' pressure fluctuation double-amplitude maximum.In some operating conditions,the main reason that cause the model water pressure pulsation is rotor-stator interaction which is caused by the superposition of the guide vane,the blade and the unit rotating.The main reason that causing the real machine water pressure pulsation is rotor-stator interaction which is caused by runner rotating.The pressure fluctuation model test's results can not fully explain the real real machine test's characteristics,but it still has the reference values.The pressure fluctuation CFD test can replace the real machine test in the field of spectrum analysis,but it's double maximum amplitude does not match with the model and real machine test's results in this paper.Validation requires further works to be done. |
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