Design of a Three-dimensional Blade of Low Solidity Circular Cascade Diffuser by Multi-Point Optimization

Abstract

Three dimensional blade of a low solidity circular cascade diffuser in a centrifugal blower is successfully designed by means of multi-point optimization technique. The optimization is aiming at improving the static pressure coefficient at design point and at small flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a clear definition of secondary flow which expressed by positive radial velocity at hub side is taken into consideration in constraints. The number of design parameters for three dimensional blade reaches to ten in this study, such as a radial gap, a radial chord length and mean camber angle distribution of the LSD blade with five control points, control point between hub and shroud with two design of freedom. Optimization results show a clear pareto front and selected optimum design shows good improvement of diffuser pressure rise at small flow rate conditions. It is found that three dimensional blade has advantage for stabilize the secondary flow effect with improving pressure recovery in the low solidity circular cascade diffuser.