Performance Analysis in Off-design Condition of Gas Turbine Air-bottoming Combined System

Abstract

Nowadays, the gradual depletion of fossil fuels associated with constraints on emissions of greenhouse gases leads to valorize their wasted heat from power plant. One of the technologies adopted for improvement is the utilization of combined cycles. For this purpose, the steam cycle is used most frequently. These systems are highly efficient, but they are very complex and water is requested, moreover they are very heavy, so they cannot always be used. In this context, Air Bottoming Cycles (ABC) become attractive for potential use in future plants and repowering because they are light, compact and they have flexible-use and no water consumption.An application of an Air Bottoming Cycle (ABC) is composed of a gas turbine powered by natural gas, an air compressor and an air turbine coupled to the system by means of a heat exchanger, referred to as the AHX (Air Heat Exchanger).The aim of this paper is to study an Air Bottoming Cycle (ABC) that uses a medium power industrial gas turbine as topper cycle. A thermodynamic optimization is realized, determining the best pressure ratio and air mass flow rate of bottomer cycle. Then, an off-design analysis varying ambient temperature and FAR (Fuel Air Ratio) is shown, in fact, in this case, the exhaust gas conditions from topper gas turbine and inlet air of bottoming joule cycle change.