ANALYSIS OF SLIP FACTORS IN CFD CALCULATIONS - ASSESSMENT OF LITERATURE MODELS

Several slip models like the Stodola, Pfleiderer, Wiesner as well as Qiu model are published in the literature. All of them are semi-empirical models considering the flow phenomena, which lead to outlet flow deviation. In this paper, a CFD-based DOE with 598 centrifugal compressor impellers and a large variation in compressor design parameters is calculated for assessing the literature models. In a first step, an automated simulation workflow for centrifugal compressor impellers is described in detail. Overall, seven geometrical parameters as well as the mass flow and rotational speed are analyzed. The CFD setup is validated based on the Eckardt publication with focus on the slip factor. A DOE based statistical ranking underlines that the Wiesner model suits best to the CFD data. Finally, the main influences on the compressor slip are determined in an analysis of variance. These are the specific speed, blade number, blade outlet angle as well as turning rate.