In this paper we present an irreversible model of the Joule-Brayton cycle.
As is well known, the gas-turbines follow approximately this thermal cycle.
Our model reproduces several characteristics of a real gas-turbine such as
convex curves of power versus pressure ratio and efficiency versus pressur
e ratio. Typical loop-shaped curves of power versus efficiency for real hea
t engines are also recovered. Our model is based in a lumped friction-like
term and in a parameter arising from the Clausius inequality. We also sugge
st a procedure for improving the power and the efficiency of the cycle.