Geometric deformation prediction of a centrifugal impeller considering welding distortion and fluid-structure interaction

Abstract

An impeller serves in a centrifugal fan, pushes the surrounding air and in turn reacts on itself. The fluid-to-structure response and part welding distortion during the fabrication and working processes will cause the impeller to deform and reduce fan performance. This work develops a numerical simulation approach and focuses on two essential factors: welding distortion and distortion induced by fluid to structure interaction. The research target was an impeller comprising five thin-plate curved fillet joints, and its total distortion was predicted using the proposed approach. First, the structure of the impeller was modeled with solid elements, and each welded local joint's welding distortion was measured with a modified inherent strain method. A one-way fluid-structure coupling analysis carefully examined the distortion induced by Fluid-Structure Interaction (FSI) from the fluid medium and coupling surfaces. Then, an interpolation method was conducted to compute the welding and FSI distortion contours using a simple structural analysis. To determine the inherent strain in a curved and non-curved fillet joint, a detailed transient analysis by the Thermal Elastic Plastic (TEP) Finite Element Method (FEM) and their welding distortion, plastic strain distribution, and inherent deformation are discussed. The welding and flow field tests both agree with the simulation results, confirming the modified inherent strain method and relevant FSI results. Thus, the developed approach can provide a suitable reference for controlling distortion in welded fans and related fluid machinery.