The Challenge of Time-Resolved Flow Investigation of a One-Stage Centrifugal Compressor with a Non-Symmetric Volute

Abstract

A single stage industrial centrifugal compressor including vaneless diffuser and a non-symmetric volute is investigated with regard to the development of flow instabilities and rotating stall. A deeper understanding of flow phenomena that might be a precursor for stall inception would help to predict unstable operation already during the design phase of a compressor stage, as today the design is commonly supported by CFD analysis providing performance data and flow information at an early stage of the design process. Due to the complex flow path geometry of the volute a sophisticated instrumentation concept was developed allowing for unsteady pressure measurement with synchronized high-resolution flow field measurement. This paper summarizes the challenges and the steps taken during rig design in terms of integrating non-intrusive, high resolution pressure measurement sensors along with access for optical techniques such as time-resolved PIV and L2F to investigate unsteady flow phenomena and stall inception occurring at reduced speed operation. Results of performance measurements and surge testing are presented and compared to CFD simulations. Exemplary results of the extensive database obtained by optical techniques in combination with dynamic pressure measurements are provided.