Impact of gas turbine frame size on efficiency of gas turbine power plants

A computational study to assess the effect of gas turbine (GT) frame size on efficiency of gas turbine power plant configurations is presented in this paper. The work includes the effect of relative humidity (RH), ambient inlet air temperature and frame size on gas turbine plant configurations with and without fogger unit. Investigation also covers economic analysis. 20 MW_e GE 5271RA, 40 MW_e GE-6561B and 70 MW_e GE-6101FA frames are selected for the present study. GT PRO software has been used for carrying out the analysis including; net plant output and net efficiency, break even electricity price (BEEP) and break even fuel LHV price (BEFP), etc. The relative humidity and temperature have been varied from 30 to 45% and from 80 to 100° F, respectively. Fuels considered in the study are natural gas, diesel and crude oil. Results show that variation of humidity does not affect the gas turbine performance appreciably for all GT frame size regardless of type of fuel. For a decrease of inlet air temperature by 10 °F, net plant output and efficiency have been found to increase by 4 and 1.7%, 4.2 and 1.3%, 4.7 and 1.8%, respectively for 20 MW,40MW and 70MW for crude oil and for GT only situation. However, for GT with Fogger scenario, for a decrease of inlet air temperature by 10 °F, net plant output and efficiency have been found to further increase by 3.1 and 1.3%, 3 and 0.9%, 3.2 and 1.1%, respectively for 20 MW,40MW and 70MW. For situations with and without fogger for crude oil, BEFP have been found to vary from 1.3968 to 1.3916, 2.13 to 2.0948, 2.387 to 2.4642 USD/MMBTU respectively for 20 MW, 40MW and 70MW and BEEP have been found to vary from 0.03142 to 0.0313, 0.02488 to 0.02504, 0.0229 to 0.0233 USD/kWh respectively for 20 MW, 40MW and 70MW.