Prewarming of Steam Turbine Components

   

Motivation

The growing share of renewable energies leads to increasing grid fluctuations in the electricity supply, which have to be compensated currently by conventional power plants. This is accompanied by a simultaneous decrease in the annual full load hours of the conventional power stations. Hence, new operating solutions are necessary which increase the flexibility of the existing power plants in order to meet these requirements. For the execution of the energy transition from conventional to renewable energies, the power plants have to be as flexible as possible with simultaneous minimal lifetime consumption. One possibility is the accelerated power plant start-up using hot gas for keeping the steam turbine warm during a standstill (e.g. at the weekend). Thus, after the standstill a hot start can be realized instead of a cold start, which saves time, emissions, money and lifetime.

 

Method

The aim of the project is to investigate the heat transfer and flow phenomena during pre-heating respectively warm-keeping operation of a HP or IP steam turbines with hot air. During the warming process, the steam turbine is continuously rotated using a turning motor. The objective of the investigations is the steady-state warming operation over a longer period of time, which makes it possible to start the turbine at any time very quickly. This operation is investigated using a numerical Conjugate Heat Transfer (CHT) model, from which analytical calculation methods are derived, which allow for a quick and simplified calculation of the temperature distribution in the critical components. Based on this, the efficiency of the pre-heating / warm-keeping operation can be evaluated.

 

Funding

The project is realized as part of the AG Turbo joint project "Cooreflex" and funded by the Federal Ministry for Economic Affairs and Energy (BMWi) in a period of 3.5 years.