Title: On the question of material selection and design options analysis for a centrifugal fan impellers

Abstract

The comparative stress analysis of various design options of the radial blower impellers used in conveyor dryer for fine-grained raw materials is presented. Several popular materials that can be used for the impeller manufacturing are considered. Finite Element Method (FEM) has been used to evaluate the stresses and strains of impeller within the operational speed range and to select the appropriate material. An advantage of using steel with higher impact toughness for the manufacturing of the fan impeller has been shown. Such materials allow to have greater resistance to shock loads during abrupt starts or stops, hitting foreign objects, etc. Analysis shows advantages of impeller design with central disk. The maximum operational rotation speed for this design is 1135 min-1 according to the yield strength with 15% safety factor, while for basic design without central disk is 1225 min-1. The maximum stress for this impeller design is slightly higher among competitors in blades slot for central disk fitting, but the overall stresses are greatly decreased, especially in contact edges with hub and shroud (by 22-38%) and blades bending deformation is reduced by 51%. It is shown that the most effective material option from the considered ones for impeller manufacturing is Hardox 450 steel. Aluminium alloy 6061-T6 demonstrates worse results. Using this alloy is limited in practice, because it made it impossible to operate in high temperature conditions. However, the advantage of using aluminium alloy is the possibility of significant lightening of the impeller while maintaining high strength parameters. The worst strength performance has impeller made from ASTM A36 steel. In design practice it is worth mentioning that Hardox steels have many competitors on the global market. These competitors have almost the same quality indicators and the choice of material is significantly dependent of its availability and price in specific region. Finally the rational choice depends on operating conditions and required fan performance. The performed research helps better understanding possible week points in different impeller design options and cause of potential failures of the centrifugal fans as well; hence, to improve reliability of such equipment engaged in various industrial plants.