Operation of a gas turbine air bottoming cycle at part load

The purpose of this study is to analyze the performance characteristics of a gas turbine air bottoming cycle operating under part-load conditions. In terms of energy efficiency, the most effective option for each installation is to operate under a nominal load. However, different applications have different needs. Marine gas turbines, for instance, should feature a high value of efficiency across a wide range of load. There are numerous other examples of installations which most of the time operate at generating power levels significantly lower than maximum capacity. This paper presents a two-shaft gas turbine air bottoming cycle. The gas turbine is coupled to the air part by means of an air heat exchanger. This configuration allows the gas turbine to operate at a nominal load while the cycle power output is regulated by the air turbine partial load. However, due to the fact that the air turbine to gas turbine mechanical power output ratio is about 0.17...0.20, it is necessary to consider a variant where the gas turbine also operates under a partial load. Selected results are summarized and compared with those obtained for a standalone gas turbine unit.