Low-Solidity Tandem-Cascade Diffusers for Wide-Flow-Range Centrifugal Blowers

The pressure recovery of a low-solidity circular cascade diffuser of a centrifugal blower was predicted by a simple method combining a theory of circular cascade diffusers and that of vaneless diffusers and it was compared with a series of experiments. Furthermore the stall limit of the diffuser was studied. In order to improve the performance further, a series of tandem-cascade diffusers were tested. In these diffusers, the front row of the cascade was designed for a small flow rate while the rear row of the cascade was designed for a large flow rate so that the tandem cascade would accomplish good pressure recovery in a wide range of flow rate. Experimental results showed that the operating range was as wide as that of a vaneless diffuser and the pressure recovery was excellent at a small flow rate while it was somewhat better than that in a vaneless diffuser at a large flow rate.