THERMODYNAMIC, THERMAL AND STRUCTURE EVALUATION OF AN IMPROVED HEAT-UP PROCEDURE FOR A LARGE POWER STEAM TURBINE

An improved start-up procedure for a large power turbine is scrutinized with the help of CFD (Computational Fluid Dynamics) and CSM (Computational Structure Mechanics) analyses. The surface heat flux and fluid/solid temperatures are first evaluated in the course of preheating the casing/intercasing space for this turbine, then further thermal and mechanical integrity calculations are made so as to validate the preheating procedure. The calculations include the geometry of the turbine outer casing, inner casing, stator blade carriers, rotor and other elements of the turbine heat-up system. The calculations are made for given parameters of the steam supplied to turbine inlet/exit pipes and given heat-and-flow balance at crucial turbine flow sections. This is a novel method of determination of surface heat fluxes at the walls of the turbine chambers from conjugate heat transfer calculations using a CFD code. Until now the surface heat flux in turbine chambers was usually calculated from empirical equations. The authors believe that the new methodology can be advantageous in the near future since using CFD it is possible to compute various geometries, not only those for which empirical correlations can be found.