Effect of radial curvature on the internal flow and performance of the vaned diffuser for a compact centrifugal blower

Abstract

Compact centrifugal blowers with vaned diffusers are often used in home electric vacuum cleaners. To achieve high efficiency and low noise, it is important to improve the performance of impellers and diffusers. In this study, the authors used a large solidity diffuser whose flow duct is low in height. The authors studied the influence of internal flow on the diffuser performance by using PIV and pressure measurement and visualizing the flow field in detail. From the authors' measurement results, low velocity was observed in the middle span section and the pressure side in the middle of the overlapped region. Pressure recovery increased gradually at the downstream of the low velocity region. From the authors' simulation results, the authors found that in the low velocity area, limiting streamlines from hub and shroud sides concentrate toward the mid-span, which lead to low velocity in the middle of the overlapped region. Compared with diffusers with small radial curvatures, diffusers with large radial curvatures are more likely to suppress secondary flow generated from the hub and shroud sides of the pressure side of the overlapped regions. Also, by suppressing separation at the hub-side and suction-side surface of the overlapped region, it is possible to improve the flow stagnation at the mid-span of the overlapped region. The authors can therefore achieve high blower efficiency by gaining larger pressure recovery at the rear part of the overlapped region.