Modeling of a Steam Turbine Including Partial Arc Admission for Use in a Process Simulation Software Environment

A dynamic process model of a steam turbine, including partial arc admission operation, is presented. Models were made for the first stage and last stage, with the middle stages assumed to have a constant pressure ratio and efficiency. A condenser model is also presented. The paper discusses the function and importance of the steam turbine's entrance design and the first stage. The results for steam turbines with a partial arc entrance are shown and compare well with experimental data available in the literature; in particular, the “valve loop” behavior as the steam flow rate is reduced. This is important to model correctly since it significantly influences the downstream state variables of the steam, and thus the characteristic of the entire steam turbine, e.g., state conditions at extractions, overall turbine flow, and condenser behavior. The importance of the last stage (the stage just upstream of the condenser) in determining the overall flow rate and exhaust conditions to the condenser is described and shown via results.