An experimental investigation to control the stall of a centrifugal compression system

Experiments to investigate the feasibility of controlling (i.e., delaying) stall in the radial diffuser of a low-speed centrifugal blower were carried out. The mass flow rate of air through the blower was reduced gradually until stall inception was accomplished. The static and dynamic pressures in the diffuser were measured along a radial or circumferential path using static and dynamic pressure transducers. The technique to control the stall was very simple, and involved decreasing the flow area at the diffuser exit with the use of throttle rings attached to either the diffuser shroud or the diffuser hub. Simultaneous attachments of the throttle rings to both the diffuser shroud and the hub walls were also made. The diffuser exit blockage ratio varied between 0% and 75%. The results showed that the self-excited flow instability (stall) in the diffuser was delayed to a lower flow coefficient, whereby the critical mass flow rate could be reduced to 60% of its value without blockage. The experimental data also confirmed that throttle rings could be an effective method for controlling stall in vaneless radial diffusers. © 2007 CASI.