Improving the power unit operation flexibility by the turbine start-up optimization

Abstract

This paper is focused on the optimization of turbine start-up. Thermal and strength analyses are conducted for the HP part rotor using the FEM for boundary conditions varying in time and space. The optimization is carried out using the RSM-GA approach. A sensitivity analysis is also performed for the steam parameters in individual stages of the start-up process. The testing results indicate that maximum stress values in the start-up initial stage are considerably affected not only by the steam-metal temperature difference but also by the temperature distribution in the element. Even if classed within the same category, start-ups differ substantially in the duration of downtimes and, consequently, in the level and distribution of initial temperature. It is therefore recommended that the start-up analysis should be preceded by a simulation of the cooling process. The optimization resulted in new start-up curves that make it possible to run the entire start-up process in less than half of the previous. Two stress maxima are observed during the start-up procedure. If the steam initial temperature is appropriately selected to the temperature of the rotor, the start-up duration is most affected by the rate at which the process is run in the final stage.