An experimental study of squirrel cage fan rotor width on performance and velocity profiles

This article reports an experimental investigation of the effect of fan width on performance and velocity profiles of a squirrel cage fan. Optimum rotor width to diameter ratio was 0.38 for present configurations which had the highest maximum total pressure coefficient and the highest maximum axial flow rate. This also means that it handled more flow in the same occupied volume. Maximum efficiency dropped with an increase in rotor width and therefore narrower rotors have higher efficiencies for a lower total pressure coefficient. A wider rotor has a flatter performance curve, higher efficiency in the operating range and a more uniform radial velocity around the rotor. For the four rotors under study, velocity components were measured by LDA across and around the rotor. The results showed that in the narrowest fan maximum flow out of the rotor exits near the cut off. Less flow in volute reduced secondary flow losses in this fan and therefore a higher efficiency ensued.