Performance of evaporative cycle gas turbines Derived from Aeroengines

The modification of the thermodynamic cycle could be an attractive opportunity for improving the performance of aeroderivative gas turbines. The simulation of a aeroderivative gas turbine modified to realize a nonintercooled regenerative water-injected (RWI) cycle is presented. The thermodynamic analysis of the RWI cycle shows that aeroderivative gas turbines with a pressure ratio from 16 to 20 can reach thermal efficiency of 45%. The design of the enhanced gas turbine is carried out under the hypotheses that the compressor is unchanged and that the stator vanes of the two-stage high-pressure turbine are partially opened to accommodate to the larger mass flow produced by water injection. The other characteristics of the turbine stator blades (internal and external area and internal coolant passages) and the rotor blades are supposed unchanged. A stage-by-stage off-design model, including blade cooling and hydrodynamics, is introduced for predicting the performance of the modified high-pressure turbine. The effects produced by modification of the cycle are then evaluated. The off-design incidence angles at the rotor inlet of both the stages appear to limit the maximum amount of the water that can be injected per air mass unit. The increase of the blade temperature instead can be compensated by decreasing the turbine inlet temperature or by refrigerating the cooling air. The mathematical model adopted for simulating the on-design and the off-design behavior of the enhanced gas turbine is described.