Study the Performance of the Combined Gas Turbine-Steam Cycle for Power Generation

Abstract

In this research, a theoretical and analytical study of gas turbine-steam turbine combined cycle for power generation was carried out to improve the performance of the thermal power plant.

A thermodynamic analysis of the combined cycle through a typical pattern was done. Appropriate assumptions were made for two kinds of combined cycles, simple gas turbine-steam turbine and reheat gas turbine-steam turbine combined cycles, such that the results obtained would closely approximate actual data. Then the equations of the combined cycle calculations were derived. Four cases were studied to choose the optimum gas turbine and steam turbine conditions for the combined cycle.

The reheat gas turbine-steam turbine combined cycle is better as compared to the simple gas turbine-steam turbine combined cycle, because the output per unit mass of air flow is significantly improved by 35-41%, and the efficiency is higher by 4 % for the combined cycle utilizing the reheat gas turbine, which points to potential cost saving for such a cycle.

It was found that the optimum conditions of the gas turbine cycle in the combined cycle mode occur at the maximum net work conditions. The efficiency of the waste heat boiler for high exhaust temperature ranges (maximum ?_B= 87%) is comparable to the efficiency of the conventional boilers. The waste heat boiler has the added advantage of simplicity, therefore this type of combined cycle using waste heat boiler has great promise for power generation.

Keywords: Combined gas-steam cycle, gas turbine cycle