Investigation on Influences of Labyrinth Seal on Stability of High-Parameter Rotor System and Application of Axiomatic Design Method

TLDR: In this paper, the authors investigated the dynamic stability of high-parameters steam turbine under the combined action of oil-film force and labyrinth seal force and showed that the cross-stiffness of high pressure cylinder shroud seals has reached about 107N/m.

Abstract: The rotor system's dynamic stability of high-parameters steam turbine under the combined action of oil-film force and labyrinth seal force was researched.The improved two-control-volume bulk-flow model was used to compute the dynamic coefficients of multi-stage labyrinth seals,and the results show that the cross-stiffness of high pressure cylinder shroud seals has reached about 107N/m,which is equal or even higher than the six-pad tilting bearing's cross-stiffness,this indicate that seal is the dominant factor of system's dynamic stability.The rotor system was modeled by finite element method and then the rotor-bearing-seal dynamic model was built to calculate the influence of seal clearance and rotating speed on rotor system dynamic performance,the analysis results indicate that the logarithm decrement(?min) of the rotor system decreased rapidly in considering of the sealing force,but the critical speed of rotor system is influenced weakly,while,the ?min is influenced by the seal clearance regionally,proper choice of seal clearance in range of 0.5 mm to 0.8 mm which is less than the design clearance(0.8mm),can optimize the leakage and stability of the system.The concept design knowledge representation and scheme optimization for coupling design was accomplished by axiomatic design(AD)theory,which takes four schemes of seal design as the case,and this indicate that the AD method is simple and effective.