Study on Flow Conditions in a Centrifugal Blower Casing. 1st Report, Pressure Distribution and Recovery Factor in a Casing.

Abstract

Flow in a blower casing which has no diffuser part and large tongue clearance was studied, The region where pressure rise occurs and the rate of rise were examined by static pressure measurement. Pressure rise occurred not only in the scroll part, but also in the section between scroll and exit duct. In the latter case, sudden change of pressure was observed within a short distance. Pressure recovery factor Cp on the branching streamline of flow from scroll to exit duct was calculated. Cp=0.83 at the maximum-pressure point and 0.77 at the design point were obtained. It was found that this section between scroll and exit duct acted as a high-performance diffuser. The rate of pressure recovery on the branching streamline was evaluated. At the design point, it was about 40 percent in the scroll part. The remaining 60 percent was recovered in the section between scroll and exit duct.