Abstract
Two kinds of unstable flows, high/low-speed modes, were observed in a flow system including a mixed-flow vaneless diffuser, and the causes of the unstable flows were experimentally and theoretically researched. The cause of low-speed mode is the mixed-flow vaneless diffuser and the high-speed mode is believed to arise from instability in the inlet pipe system. The effects of physical components of the system were recognized in the measurement of the unstable flow. In the present study, the effects of an inlet pipe, outside diameter of the diffuser and cone angle of the diffuser are examined experimentally. A predicting equation of a rotational speed of cells for low-speed mode is proposed from estimation of measured values, and it is confirmed that the equation is applicable over the wide geometric range of the mixed-flow vaneless diffuser.
