Unsteady flow modelling in turbine stage.
The paper deals with the problems of unsteady flow modelling in turbine stage. The impact of unsteadiness in the design procedure as well as in the real flow phenomena are briefly addressed. After a discussion of the physical aspects of the real flow in turbine stage which differ from the unsteady flow in a single row environment, the paper reports a survey of the actual and more recent approaches to the numerical modelling on the unsteady flow in multiple rows environment. The classical steady models, used for long time in the design procedure, are addressed and their limits are focused. The more complex procedures ranging from quasi-unsteady methods to the fully unsteady methods are reported and investigated in details. The discussion on the specific features of the different approaches is pointed to assess the accuracy, the feasibility, the robustness and the usability (i.e. the computer time and storage requirements). Sample results from the author research activity are reported and presented. Discussion of crucial and open questions to improve the prediction capability of the methods are finally reported as well as some comments on the possibility to joint classical (steady methods) and advanced approaches (fully unsteady methods) to improve the actual design procedure are addressed.
Martelli
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Energetic Department, University of Florence, Italy.