Design optimization of a volute casing in a centrifugal fan installed in a refuse collecting system has been studied to enhance the performance of the fan. Two design variables, which are used to define the shape of a volute casing, are introduced to increase the pressure and efficiency of the fan. The pressure and efficiency is selected as an object function for the present shape optimization. Response surface method (RSM) combined with three-dimensional Navier-Stokes solver is introduced to find optimum shape of a volute casing in a centrifugal fan. To analyze three-dimensional flow field in a centrifugal fan, general analysis code, CFX, is employed in the present work. SST turbulence model is employed to estimate the eddy viscosity. Unstructured grids are used to represent a composite grid system including blade, casing and inlet guide. Throughout the shape optimization of a volute casing, the fan efficiency is successfully increased by decreasing local losses in the blade passage and the volute casing. The result of a shape optimization shows that the efficiency and pressure of the optimized shape at the design flow condition is enhanced by 2.7% and 1.9% based on the reference fan, respectively. It is found that the casing width of the design variables is more sensitive on the object function of efficiency compared to that of the diameter of casing expansion. This means that the shape optimization using a casing width is more effective to increase fan efficiency in a centrifugal fan.
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