Orthogonal optimization design of a Sirocco fan and numerical analysis on the internal flow characteristics

The forward-curved multi-blade centrifugal fan, also termed as Sirocco fan, is characterized by its complex characteristics of internal flow within the impeller and volute. Currently most of the fans are designed with modifications or optimizations for certain geometric parameters which could not ensure the well compatibility of flow in the impeller and volute, thus it is difficult to improve the aerodynamic performances of the fans. In this paper, we performed a multi-parameter design of a Sirocco fan with optimizations on the geometric parameters of the impeller and volute. The geometric parameters of the volute were designed based on analysis of the internal flow patterns, and the influence from the impeller is also considered. Optimization on the geometric parameters was carried out using the steepest descent method to improve the static pressure rise and efficiency under the designed flow rate by taking into account the relevance of flow in the impeller and volute. The effect of the parametric optimization is evaluated and analyzed by large-eddy simulation (LES). It was found that the static pressure rise and efficiency of the optimized model increase by 1.8% and 5.0% compared with the baseline model, respectively. The static pressure rise fluctuates in a regularly periodic manner. The optimized model reduces the area of low-pressure recirculating flow at the center of the fan and the separated flow on the suction surface of the blades. The near-wall flow on the volute surface is more stable, and the pressure fluctuation around the volute tongue is reduced. The outflow of the volute exhibits better uniformity than the baseline model.