Thermodynamic analysis and optimization of a gas turbine and cascade CO₂ combined cycle

This paper describes a novel gas turbine and cascade CO₂ combined cycle which composes of a gas turbine, a supercritical CO₂ Brayton cycle and a transcritical CO₂ cycle. To show its thermodynamic potential, a new solving procedure for performance evaluation and optimization of this combined cycle was proposed. Genetic algorithm (GA) was introduced for parameter optimization in order to get better combined cycle performance. Simulation results showed that the GT-cascade CO₂ combined cycle did have better thermodynamic performance than conventional GT-steam Rankine combined cycles. And this GT-cascade CO₂ combined cycle could have an efficiency increase of more than 17.03% from singe gas turbine cycles. Moreover, this combined configuration could be applied to gas turbines of different power levels. Through GA optimization, the thermal efficiency could achieve 52.53% for the Taurus 60 GT-cascade CO₂ combined cycle. Sensitivity simulation results indicated that the proposed cascade CO₂ cycle was favorable to counteract the influence of ambient temperature on the combined cycle performance.