COMBINED CYCLE ENGINES

A combined cycle engine (103) is formed of a gas turbine cycle coupled with a fuel expansion cycle in which fuel for the gas turbine cycle is the working fluid of the fuel expansion cycle. The fuel expansion cycle comprises, in flow series, a fuel pump (401) for pumping a cryogenic fuel for the gas turbine cycle, a first heat exchanger (403) for heating the fuel, an expander (404) to recover power by expansion of the fuel and to thereby drive a load (401), and a second heat exchanger (406) to reheat the fuel. The gas turbine cycle comprises, in flow series, a compressor (302, 304), a combustor (504) for combustion of reheated fuel delivered from the second heat exchanger (406), and a turbine (307, 308) configured to drive the compressor (302, 304). The first heat exchanger (403) and the second heat exchanger (406) are stationed downstream of the combustor (504) and are configured to transfer heat from combustion products of the gas turbine cycle to the fuel in the fuel expansion cycle.