Thermal and Structural-Mechanical Modeling and Optimization of a Transiently Operated Steam Turbine Using the FE Method

Due to the growing share of renewable energy sources, there is increasing volatility in the energy fed into the grid. To cover the load when renewable energy is unavailable, steam turbines in conventional power plants must be operated more flexible and in line with the demand. The increased number of start-up processes after longer standstills results in high lifetime consumption of steam turbine. This mode of operation increases the utilization on components, which results in a reduction in service life. The Hot Standby process has already been proven itself as a method of Siemens Energy Flex-Power Services for making steam turbine operating processes more flexible. Through targeted heat transfer to the steam turbine components using a trace heating system, a cold start can be avoided, and the operational flexibility of the turbine can be increased. Heat transfer occurs predominantly via thermal radiation, which is particularly difficult to simulate compared to other heat transfer mechanisms. To simplify heat radiation exchange and still achieve realistic results, various methods and parameter settings are applied. In this paper the heat transfer via thermal radiation and its influence on heating up of structural turbine components is investigated. At the beginning, different benchmark parameter settings and the associated result variations are presented. These findings are then implemented in the modeling of the SST-3000 turbo set of Siemens Energy and the results of the simulation are discussed. The simulation results are used to determine temperature gradients that are used to design hot standby features used for flexible power plant operations.