Aerodynamic analysis of the fan-diffuser in the automotive wind tunnel

In this paper, v2f turbulence model is used to study the effects of diffuser angles under seven types of incoming flow conditions, including both uniform and non-uniform incoming flow conditions. A certain optimal diffuser angle leading to minimal total pressure loss coefficient can always be found under each condition due to the interaction between wall friction loss and flow separation loss. Compared with uniform incoming flow condition, when non-uniformity of incoming flow is less than 40.0%, the optimal diffuser angle only have a small increment within 1.5°, but the total pressure loss is 2.5 times higher at lest. The circumferential non-uniformity of the incoming flow axial velocity affects the aerodynamics performance of fan-diffuser most and the total pressure loss coefficient is even one order of magnitude greater when the non-uniformity is 36.5%.