A simple gas turbine system and co-generation power plant improvement based on endogenous and exogenous exergy destruction

Abstract

Exergy analysis provides useful information about system optimization. An exergy analysis identifies the sources of thermodynamic inefficiencies by evaluating the exergy destruction within each system component. Splitting the exergy destruction into endogenous/exogenous parts represents a new development in the exergy analysis of energy conversion systems. The present work is an attempt to investigate the combustion process in a simple gas turbine (GT) and a cogeneration power plant based on the general concept of endogenous and exogenous exergy destruction. Therefore, using a graphical approach, an advanced exergy analysis is applied to both cycles with different fuels such as natural gas (NG) and diesel. Also, dual-fueling of the combustion chamber (CC) is investigated based on the aforementioned approach in which different substitutions of NG fuel with diesel fuel are considered. It is found that in both cycles, the CC has the largest value of the endogenous exergy destruction. The exergetic efficiency of the CC is the least value of the three components of the GT system and increases by about 1.76 per cent, when NG fuel is substituted for diesel fuel. Also, for the cogeneration power plant, it can be seen that the exergetic efficiency of CC increases by about 1.87 per cent, when NG fuel is substituted for diesel fuel. As a result, the total system exergetic efficiency for simple GT and co-generation power plants increases by 1.05 per cent and 1.6 per cent, respectively. Therefore, cycles have been improved by increasing the substitution of NG fuel with diesel fuel. The results obtained here may provide some useful information on the optimal design and performance improvement of these cycles.