IMPACT ASSESSMENT OF MODERNIZATION OF STEAM TURBINE END SEALS ON THE RESIDUAL RESOURCE

Abstract

Modernization of sealing units with a change of design is carried out in order to improve the technical and economic parameters of steam turbines. It is known from experience of operation of the turbine equipment that, ring cracks in rotors arise in sealing areas. This is due to both seals design features and the accumulation of thermocyclic fatigue. The research is devoted to the study of resource parameters of the high-pressure rotor of the T-250/300-240 turbine equipped with seals of labyrinth, honeycomb and direct-flow type. Numerical experiments were performed on the basis of three-dimensional geometric models of interflow end seals of the high pressure rotor. The finite element method is used to discretize the computational area. The thermal state of the turbine is calculated for the starting mode from the cold state of the metal by solving the boundary value problem of thermal conductivity in a non-stationary setting. The calculation of the stress-strain state of the turbine takes into account the obtained data on temperature stresses and forces from the non-uniformity of temperature fields, as well as centrifugal forces and steam pressure. Differences in the stress-strain state of the rotor for different seal designs are established. It is indicated that after grooving of labyrinth interflow seals to the honeycomb structure, the stress level in the rotor decreased by 8 %, and when grooving to the direct-flow structure — by 21 %. The accumulated damage in the main metal of the turbine was determined using experimental curves of long-term strength of steel 25Cr1Mo1V. The calculation of resource indicators showed that in the transition from the labyrinth to the honeycomb design of the seals, the individual resource of the high-pressure rotor increases by 6.1 %, and in the transition to direct-flow — by 14.4 %. Ref. 10, Fig. 5, Tab. 1.