Design and fluid dynamics of volutes in centrifugal compressors: A comprehensive review

The volute can presumably be considered as the most neglected aerodynamic components in the research literature of centrifugal compressors. Compared to the abundant investigations on the flow inside the impellers and diffusers, the published studies on volutes, especially in centrifugal compressors, are limited. This is while the volutes are the cause of pressure distortions which can propagate upstream and affect the performance of the impellers and restrict the stable operating range of the compressors. The current paper presents a comprehensive review on the scholars which have analyzed the design methods and aerodynamic performance of volutes. The main design methodologies for the volutes which are, the constant mean velocity, constant angular momentum and non-constant angular momentum, are reviewed. The review showed that there are only a few studies which have compared these design methodologies and they have been carried out at a limited number of operating conditions. The need for a general guideline for selecting the suitable design method at a desired operating condition is felt. The review of the numerical studies revealed that most of the investigations are performed using the steady Reynolds-Averaged-Navier-Stokes equations with one and two-equation eddy-viscosity turbulence models. Hence, investigating the unsteadiness induced by the upstream effects using simple or even more sophisticated models can provide deeper insights into the flow structure inside the volutes under various operating conditions. Furthermore, although there are some studies about the effects of the tongue geometry on the performance of the volutes, a systematic investigation in this regard can be very beneficial for the designers.