NUMERICAL PREDICTION OF CENTRIFUGAL COMPRESSOR STABILITY LIMIT

The compressor operating range is a crucial performance parameter for the design and development of such a gas turbine component. During the design phase it is of utmost importance to be able to predict or estimate the limit mass flow rate, for a given speed line, that will form the surge line and that will influence the overall operating range and matching capabilities of the compressor CFD simulations are routinely used for the compressor analysis and strongly embedded into the design process. Nevertheless, the ability of a CFD model to accurately predict the surge limit without the need of a massively expensive full 3D unsteady simulation of the centrifugal compressor stage is still an open issue. Moreover in a design process it is very cumbersome to require series of computationally intensive simulations for a 3D geometry that is still under development. In the present work, the use of a CFD approach for the numerical prediction of the stability limit of centrifugal compressors is presented. The proposed approach is applied to different centrifugal stages with vaned dffusers and the obtained surge lines are compared to available experimental datasets. An in-depth analysis of the compressor stage stability limits due to its dfferent components is presented and the use of fully 3D unsteady simulations for the complete stage are discussed to give an additional insight into the phenomenon.