RECIRCULATION ZONES DURING THE CENTRIFUGAL COMPRESSOR SURGE CYCLE: CFD SIMULATION

In this paper the flow recirculation regions during the full surge cycle were described. It is a known fact that the surge cycle consists of two periods: backflow and recovery. The aim of this paper is to add spatial dimension to this analysis. Therefore, the main target is to identify the regions of backflow and recirculation throughout the surge cycle. The full surge cycle modelled with an application of unsteady RANS methods is demonstrated - the significant push was put to realistic boundary conditions definition, narrowed to establishing pressure setting at both inlet and outlet positions located far from the impeller. The results show that all the backflow appears in the recirculation zones that grow and diminish throughout the surge cycle. The regions of inflow and backflow can concurrently exist at different stages of the surge. The analysis includes areas occupied by both structures and mass flowrates associated with them. Presented research is a part of a project aiming at design and construction of more efficient anti-surge systems. Its overall target is to eventually introduce the anti-surge systems that are made to fit the particular machine. Therefore, the understanding of local flows during and prior to surge are one of the key issues that need to be interpreted.