Flow characteristics analysis of an ultrathin forward-curved multi-blade centrifugal fan

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The ultrathin centrifugal fan, widely utilised in compact electronic devices such as laptops, is characterised by numerous forward-curved blades that generate high static pressure and flow rates. Despite its widespread application, the flow dynamics of ultrathin centrifugal fans remain insufficiently explored. In large-scale centrifugal turbomachinery, boundary layer thickness is typically negligible, with flow separation being the primary contributor to flow losses. However, the loss mechanisms in ultrathin centrifugal fans are not yet well understood. This study addresses these gaps by investigating entropy production associated with various flow processes, decomposing entropy generation into components related to molecular viscosity and eddy viscosity. Large Eddy Simulation (LES) is employed to analyze the turbulent characteristics of ultrathin centrifugal fans. The findings indicate that the boundary layer thickness, constituting approximately 10% of the volute height, is substantial. Viscous dissipation within the boundary layer generates 2.85 × 10 − 4 W / K of entropy, whereas flow separation contributes 1.16 × 10 − 5 W / K , underscoring the significant impact of the boundary layer on the fan's operational efficiency. To further investigate the turbulence characteristics, hot-wire anemometry measurements were conducted to obtain the turbulent energy spectrum. Moreover, the turbulence scale and pressure fluctuations derived from simulation results were analyzed in the frequency domain, revealing that low-frequency components are linked to blade surfaces, while high-frequency components are associated with the volute shell. The insights gained from this flow field analysis can inform the design of more efficient and quieter cooling fans.