Assessment of a twin-entry turbine efficiency model including momentum exchange between branches

Abstract

Radial twin-entry turbines standard maps have limited data available for fitting model parameters since they usually provide information only at full and partial admission conditions. However, twin-entry turbines’ most common operation is at unequal admission conditions. A new losses-based efficiency model has been developed that takes into account the behaviour of the twin-entry turbines at unequal admission conditions considering the different losses produced in each of its parts to improve the model predictions in these conditions. The model is validated with experimental measurements of the whole range of admission conditions, and all the model parameters needed are fitted. Moreover, the model’s accuracy is compared with empirical and commercial models using a limited amount of data instead of the whole measured map, obtaining reasonable extrapolations and improving the results provided by the other models at unequal admission conditions.