Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.
The working temperature of a gas turbine, necessary to
achieve high efficiency, makes cooling of the first turbine
stages unavoidable. Air and steam can be used for cooling. A
model for an air-cooled gas turbine based on the work of
Young and Wilcock [J.B. Young, R.C. Wilcock, ASME J.
Turbomachinery 124 (2002) 207–221] is implemented in
AspenTM. Simple cycle calculations with realistic parameters of
current machines are made and confirm the results of Wilcock
et al. [R.C. Wilcock, J.B. Young, J.H. Horlock, ASME J. Eng.
Gas Turb. Power 127 (2005) 109–120] that increasing the
turbine inlet temperature no longer means an increase in gas
turbine cycle efficiency. This conclusion has important
consequences for gas turbines because it breaks with the
general accepted trend of increasing the TIT. An intercooled
gas turbine cycle is intensively investigated, taking the turbine
cooling into account. Intercooling not only lowers the work of
compression, but also lowers cooling air temperatures. The
major influences of the intercooling on the gas turbine cycle are
mapped and explained. Optimum intercooling pressure for
maximum gas turbine cycle efficiency is much lower than
halfway compression. A simulation of the LMS100, the most
recent gas turbine on the market from GE Energy, is made to
verify the simulation methodology. The claimed intercooled
cycle efficiency of 46% is confirmed. Further increasing the
pressure ratio and TIT can still improve the performance of the
intercooled gas turbine cycle.
