Modelling the power production of single and multiple extraction steam turbines

A thermodynamic model for the prediction of the operating performance of back pressure steam turbines with single and multiple extractions is presented. The approach takes the advantage of previous models reported in the literature and incorporates some improvements that allow for the prediction of the shaft work under changes in the operating conditions such as steam flow rate and pressure of each of the extractions. Simulation under changed operating conditions is conducted through the use of expressions that correlate the temperature and enthalpy of the steam as a function of the extraction pressure. The model incorporates the calculation of the isentropic efficiencies of each stage. The validity of the model is demonstrated by comparing the results with those of commercial turbines reported in the open literature.