Fluid-Structure Interaction Analysis of a Centrifugal Fan

Abstract

Centrifugal fans are used within many applications where great ability to create pressure increase is of importance. Rotating machinery such as industrial fans are often expected to withstand a very large number of load cycles with little or no maintenance. Consequently, accurate estimation of the fatigue limit is of interest when designing a centrifugal fan. It is known that pressure fluctuations arise on the fan leading to time varying loads. It is proposed that these pressure fluctuations have an impact on the fatigue limit of the centrifugal fan studied in this work. This study investigates the capabilities of estimating the fatigue limit based on fluid-structure interaction with commercial software. In this study, a method of simulating fluid-structure interaction has been applied on a centrifugal fan with the commercial software platform ANSYS Workbench. The method involves simulation of the unsteady turbulent flow through the fan as well as, static and transient, structural analysis. Fluid analysis has been performed on the deformed shape on the fan caused by centrifugal force. Pressure fluctuations on the fan surface are analysed and applied to the fan in a transient structural simulation to obtain the stress variations in critical locations. A crude estimate of the fatigue limit has been done based on the obtained stress field. Blade pressure fluctuations are captured in simulations and interesting correlations between the blade surface fluctuations and the surrounding flow structures are found. Results shows a weak interaction between structural and fluid field suggesting that a one-way coupled approach is adequate when performing fluid-structure interaction simulations of the studied fan. Aerodynamic loads are found to have a negligible impact on the estimated fatigue life. The main weakness of this work is the lack of verification of the numerical simulations.