Numerical simulation of the unsteady stator-rotor interaction in a low-speed axial fan including experimental validation

Purpose - The purpose of this paper is to focus on the analysis of the dynamic and periodic interaction between both fixed and rotating blade rows in a single-stage turbomachine. Design/methodology/approach - A numerical three-dimensional (3D) simulation of the complete stage is carried out, using a commercial code, FLUENT, that resolves the 3D, unsteady turbulent flow inside the passages of a low-speed axial flow fan. For the closure of turbulence, both Reynolds-averaged Navier-Stokes modeling and large eddy simulation (LES) techniques are used and compared. LES schemes are shown to be more accurate due to their good description of the largest eddy structures of the flow, but require careful near-wall treatment. Findings - The main goal is placed on the characterization of the unsteady flow structures involved in an axial flow blower of high reaction degree, relating them to working point variations and axial gap modifications. Research limitations/implications - Complementarily, an experimental facility was developed to obtain a physical description of the flow inside the machine. Both static and dynamic measurements were used in order to describe the interaction phenomena. A five-hole probe was employed for the static characterization, and hot wire anemometry techniques were used for the instantaneous response of the interaction. Originality/value - The paper describes development of a methodology to understand the flow mechanisms related to the blade-passing frequency in a single rotor-stator interaction.