Exergy based Performance Analysis of a Gas Turbine at Part Load Conditions

A gas turbine can run at off-design due to change of ambient conditions or load demand. This needs to study how part load affect the gas turbine performance. The gas turbine considered for this study consists of variable stator vanes (VSVs). The VSVs are re-staggered for load greater than 50% so that it would increase exhaust gas temperature. For load less than 50% the VSVs are fully opened. The merit of the gas turbine system should be determined using exergy analyses because energy analyses tend to overestimate performance. Therefore, exergy model of each gas turbine component is formulated. A 4.2 MW gas turbine is analyzed for a wide range of part load condition. It is found that, at full load, the exergy destruction in the combustor is 48.9% and the loss with the exhaust gas is 35.8%. The reminder is being destroyed in the turbine and compressor are 10.8 and 4.3%, respectively. For comparison purpose both the first and second law efficiencies of each component are represented together. This analysis would help to identify the equipment where the potential for performance improvement is high, and trends which may aid in the design of future plants.