Surge margin optimization of centrifugal compressors using a new objective function based on local flow parameters

Authors

Johannes Ratz - TU Darmstadt, Institute of Gas Turbines and Aerospace Propulsion
Sebastian Leichtfuß - TU Darmstadt, Institute of Gas Turbines and Aerospace Propulsion
Maximilian Beck - TU Darmstadt, Institute of Gas Turbines and Aerospace Propulsion
H. P. Schiffer - TU Darmstadt, Institute of Gas Turbines and Aerospace Propulsion
Friedrich Fröhlig - MTU Friedrichshafen GmbH

Abstract

Nowadays, 3D-CFD design optimization of centrifugal compressors in terms of surge margin is one major unresolved issue. On that account, this paper introduces a new kind of objective function. The objective function is based on local flow parameters present at the design point of the centrifugal compressor. A centrifugal compressor with vaned diffuser is considered to demonstrate the performance of this approach. By means of a variation of the beta angle distribution of impeller and diffuser blade, 73 design variations are generated and several local flow parameters are evaluated.  Finally, the most promising flow parameter is transferred into an objective function and an optimization is carried out. It is shown that the new approach delivers similar results as a comparable optimization with a classic objective function using two operating points for surge margin estimation, but with less computational effort since no second operating point near surge needs to be considered.