The vaneless diffuser is an important part of the centrifugal compressor.It is important to study the characteristics of the flow field in the vaneless diffuser for improving the performance of the diffuser and understanding the occurrence of the stall.The purpose of this study is using the steady state viscosity calculation method to explore the evolution of the vaneless diffuser internal flow field under different flow rates

using the Workbench15.0 software to model the centrifugal compressor and implement numerical simulation and the centrifugal impeller and vaneless diffuser are analyzed.The results show that

the vaneless diffuser backflow zone occurs at the diffuser hub side

with the decrease of the flow coefficient

the backflow region appears in the diffuser shroud side

when the flow coefficient of further reduces

the backflow zone appears in the diffuser wall on both sides.The vaneless diffuser does not immediately enter the stall state when the backflow zone appears.When the backflow zone expands to the diffuser outlet

the diffuser enters into rotating stall state.The unsteady flow in the diffuser can be represented by the static pressure in the diffuser

and the static pressure rise coefficient will decrease when the rotating stall occurs in the vaneless diffuser.