Simulation of the Overall Transient Operation of Gas Turbines

Reduction of the start-up time and flexible operation require comprehensive testing and modification of a gas turbine. The cost of this testing can be significantly reduced by using reliable dynamic models to simulate critical regimes without the possibility of damage. This paper describes a dynamic model, called GTDyn, for simulation of the complete transient operation of gas turbines, from start-up to shutdown. In addition to basic transient phenomena, volume packing, and heat soakage, the effects of the tip clearance change on the performance are also included. The performance of the compressor and the turbine are described using steady-state characteristics, while component dynamics are modeled with the conversation laws in the form of ordinary differential equations. The applied component characteristics are calculated using through-flow solvers. A large number of compressor maps are implemented to include adjustments of stator blades and changes in tip clearances. The model is paired with a control system for the regulation of speed/load and turbine exit temperature. For the start-up sequence, a mode with starter assistance is implemented. The developed model was applied for simulating multiple start-ups to analyze the influence of thermal states on machine performance. The numerical results are compared with experimental data for an industrial single-shaft, air-cooled gas turbine. The comparison includes temperatures and pressures at inlet and outlet stations of each component, inlet mass flow, IGV adjustment, fuel mass flow, gas turbine speed, and power. The numerical results for starter power and compressor tip clearance are also presented.