Modeling combined cycle performance at full and part loads

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.

A block of 460 MW (two gas turbines and one steam turbine) combined cycle power plant has been modeled and simulated. The model equations have been solved by the constructed MATLAB computer program. The model accounts for the actual operating parameters within the block components; compressor, combustion chamber, gas turbine, HRSG and steam turbine. The developed program is utilized to investigate the effect of load, and heat losses in the combustion chamber on the block performance. To validate the present model, the gas turbine performances at different loads are calculated. The results of the present model are compared with the corresponding ones given by the block’s manufacturer. The comparison has shown that the deviations are in the range of 3-5%. Exergy analysis is performed based on the first and second laws of thermodynamics. Its results have shown that the maximum exergy destruction is found to be in the combustion chamber at full and part loads. The effects of the percentage of heat losses within the combustion chamber on the fuel consumption, gas turbine cycle efficiency and turbine work net are investigated. The fuel mass flow rate and work net of the gas turbine increase as the heat losses increase while the thermal efficiency decreases.