Flow in a dirty air fan with a semi-open centrifugal impeller and a squirrel volute

Abstract

The flow driving performance data of a dirty air fan with a semi-open centrifugal impeller and a squirrel volute, designed for household vacuum cleaners, are experimentally obtained with the industry standard tests. The fluid flows in the fan at various conditions are numerically simulated. The agreements between the numerical data and the experimental results are reasonably good. The model-simulated flow structures show that air flow passes over the blade between the impeller blade channels. A high-velocity spot is formed at the top of each blade. The leakage flow, from the fluid-collecting squirrel back to the blade channels, represents a waste of the fluid dynamic energy and the pressure potential energy. However, such leakage flow presses the inlet air to the bottom disc of the impeller and helps in preventing the solid objects from getting to the blade top. Flow energy analysis shows that the main energy loss is in the semi-open impeller. The leakage flow and the disagreements between the flow direction and the blade angles at the leading and the trailing tips are the main causes of the low energy efficiency of the fan.