A novel internal combustion steam turbine cycle suitable for an underwater power plant and a peak-cut electric power plant is proposed on various power levels. The feature of the cycle is the combustion of a stoichiometric hydrogen-oxygen mixture in the working fluid (water/steam), which allows higher initial steam temperature than that of the conventional steam turbine cycle. The combustion product which works in the turbine is extracted from the cycle in the liquid phase. This cycle has higher thermal efficiency than that in the case of external combustion. Thermodynamic performances of simple, regenerative and reheat-regenerative steam turbine cycle are compared. Effects of initial steam pressure, initial steam temperature, hydrogen excess ratio and power level on the thermal efficiency are discussed. The thermal efficiency of a 100MW reheat-regenerative cycle is 52 % on the basis of lower heating value.
