Numerical study of surge predecessors in centrifugal blower — inlet recirculation

Paper presents the numerical investigation of inlet recirculation in a centrifugal blower. This phenomenon is known as a local flow instability that is not too harmful in centrifugal compressors compared to centrifugal pumps. However recent findings have shown that it can be regarded as a surge predecessor, and hence very significant for compressors. Therefore there is strong need to understand its physics. One of ways to understand it to apply computational fluid dynamic (CFD) simulations. Therefore in this study the transient numerical simulations were conducted and results were related to the experimental data presented in other papers. Simulation confirmed that the inlet recirculation structure can be resolved by means of CFD and the results are in agreement with some available models. Inlet recirculation structure built up gradually along the circumference increasing the power loss. Obtained structure also explained pressure variations observed in experiments. This has shown that CFD can bring significant improvement in existing antisurge systems and recirculation bleeds that extend the machine operating range