Shape optimization in the design of turbomachinery based on the three-dimensional flow analysis has been developed remarkably in recent years with the rapid enhancement of computational power. In the present study, optimal design of a centrifugal fan installed in refuse collecting system has been performed using response surface method and three-dimensional Navier-Stokes analysis to increase fan efficiency. The centrifugal fan is used to increase suction pressure for the moving of a waste through the pipe line of the system. Two design variables, which are used to define the shape of an inlet guide, are introduced to increase the efficiency of the fan. In the shape optimization using the response surface method, data points for response evaluations are selected, and linear programming method is used for an optimization on a response surface. To analyze three-dimensional flow field in the 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 centrifugal fan, the fan efficiency is successfully increased by decreasing local losses in the blade passage. The result of shape optimization shows that the efficiency of the optimized shape at the design flow condition is enhanced by 1.42% based on the reference fan. It is found that recirculation flow region of optimum one is relatively small compared to the reference one. The reduction of recirculation region can be decreased the shaft power of an impeller, thus it can be increased the efficiency of the fan.

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