Steam-Gas Combined Units with Multiple Expansion, Re-heating Gas Section[GRUPPI COMBINATI GAS-VAPORE CON SEZIONE A GAS AD ESPANSIONE FRAZIONATA INTERRISCALDATA.]

The paper covers the study of steam-gas combined units fitted with a gas section that realizes multiple expansion with only one intermediate pressure to which re-heating is effected. The aim of the study is to point out the choice of the particular type of gas cycles considered on the overall efficiency of the unit and the ratio between the power of the gas and steam sections. The investigation methodology adopted, which keeps account of the irreversibilities of the transformations in the turbomachines by means of polytropic efficiency, assumed constant, essentially consists in evaluation the variations in the performance of the units being examined compared to those of simply combined units. The expansion ratio and the input temperature of the low-pressure turbine have been assumed as variables.