Optimization of inlet air cooling systems for steam injected gas turbines

Abstract

The cooling of the inlet air in gas turbines is a practice used to improve power performances. In the past, the authors suggested extending this practice to STIG turbines, using some of the heat generated in the back boiler to supply the absorption systems. Positive results have prompted further developments. For the purpose of verifying the positive effects of compression air cooling in STIG turbines, a calculation model has been developed and studied specifically for gas turbines and STIG turbines. The model has been applied to the Allison 501 KH turbine. In addition to focusing on the two traditional techniques used to cool the air of the compression system through an absorption unit and an intercooling unit, the present work emphasizes the advantages of using an ejection cooling system. The availability of exhaust heat from the STIG turbines prompted the idea of cooling through a double ejection system. Water cannot be used as a primary refrigerant in compression cooling systems because of the very low pressures that have to be reached, whereas the ejection system used for steam compression allows for the use of water. Moreover, the ejection system is relatively easy to design and construct. The use of this cooling system, enables good results to be obtained in terms of the ejection system's coefficient of performance and consequently of the STIG turbine's performance.