Design and modelling of circular volutes for centrifugal compressors

The current paper investigates the application of 1D performance models for external circular volutes. The aim is to substitute the volute in computationally expensive CFD calculations with lower order models during intermediate design iterations. The CFD predicted volute performance, available to the authors from designs of various stages including both vaned and vaneless diffusers, have been used as benchmarks. The conventional low order models have been examined and, where appropriate, further developments have been made. The final set of the models proposed in the paper are applicable to stages with both vanes and vaneless diffusers. This chapter discusses the application of 1D performance models for external circular volutes. The aim is to substitute the volute in computationally expensive CFD calculations with lower order models during intermediate design iterations. The flow at the discharge of centrifugal compressor stages is typically collected by a volute or scroll, consisting of a spiral duct with increasing flow area around the circumference, followed by a diffusing cone downstream of the throat. The volute cross-sections are often 'one-sided' and can be external or overhung, depending on the available radial space. The volute geometry consists of a spiral duct with increasing flow area around the circumference, followed by a diffuser cone downstream of the throat. The design flow angle can be linked to the required volute throat area at the selected design point by considering the conservation of mass and angular momentum from volute inlet to its throat.