Asymmetric flow in vaneless diffusers of centrifugal blowers.

An analytical method is proposed to evaluate the flow behaviour which is not symmetric between the walls. The analysis consists of two parts; one is for the entry zone where the main flow with velocity gradient exists between the wall boundary layers, and the other for the downstream zone where the boundary layers fill up the passage. In both cases momentum integral equations are used together with some special relations for the main flow or for the maximum velocity. The analysis was applied to the experiments in the literature as well as the authors' experiments and good agreement is observed not only for the pressure distribution but also for the velocity distribution. At a small flow rate, it is observed that a reverse flow occurs alternately on the diffuser walls and farther downstream a reverse flow disappears from both walls. Such unusual flow behaviour is predicted also by the theory. (A)