Spatiotemporal Characteristics and Pressure Fluctuations of Internal Flow in a High-Speed Centrifugal Blower for Vacuum Cleaner at Low Flow-Rate Conditions

The steady and unsteady characteristics of the internal flow in a high-speed centrifugal blower are studied by computational fluid dynamics (CFD) approach at low flow rates. It is demonstrated that as the flow rate decreases, the separation of flow in the blade passage becomes serious, and separated vortexes always occur on the suction surface of the blade which gradually expand and block the passage. The stall cells move downstream and generate vortices at the exit of the passage, resulting serious loss to the performance of the blower. Q-criteria is used to analyze the flow field and explore the evolution of the vortex structure in the impeller. It is further found that strong pressure fluctuations are caused by the rotating stall in the impeller. At the stall conditions, the instability characteristics are particularly obvious. At flow rates of 0.65Qn and 0.47Qn, the pressure fluctuation in the blade passage is dominated by the blade passing frequency, while a lower frequency dominates at 0.26Qn. Moreover, the flow on the suction surface of impeller blades fluctuates substantially. The characteristics of steady flow and unsteady flow can clearly explain the internal flow of centrifugal blower for vacuum cleaners at low-flow conditions, which can be widely used in various engineering designs of vacuum cleaners.