Modelling and simulation of the effect of ambient parameters on the performance of a combined cycle gas turbine power plant

Gas turbine combined cycle power plants are one of the most efficient energy conversion systems. These systems encompass: a gas turbine cycle, steam turbine cycle and heat recovery steam generator. The electrical power of a gas turbine combined cycle power plant heavily depends on ambient parameters — mainly on temperature. A variation of ambient parameters changes the compressor's working point, hence the temperature and stream of the flue gas leaving a gas turbine can be changed. In consequence, boiler efficiency, steam flow and parameters can also be changed. The article presents a numerical analysis of the influence of ambient parameters on energy operating indicators of the gas turbine, double pressure heat recovery steam generator and the steam turbine. The effect of the variation of the ambient temperature on gas turbine electrical power, flue gas stream and temperature at the outlet of turbine is modelled with the use of correction curves. A mathematical model of a heat recovery steam generator is based on mass and energy equations and additional equations which describe the heat transfer process. Unknown parameters which occur in empirical equations have been estimated on the basis of measure results. The model of the steam turbine contains a balance model and a theoretical-empirical model of the steam expansion line in the turbine. The calculation method and exemplary calculation results have been presented.