Suppression of Stall-Induced Instability and Positive Slope at Low Flow Rates of an Axial Fan With Two-Dimensional Anti-Stall Fin

Abstract

Abstract An axial fan in the general industry needs to secure stable characteristics in a wide operating range through an antistalling process, concerning its high demands, energy consumption, safety, and lifetime. As a “simple” and “original” method to control the stall of an axial fan, two-dimensional plates so-named anti-stall fin (ASF) were attached inside the casing and toward the shaft. The sensitivity analysis for design variables was conducted through the 2k full factorial design method, and the optimization was performed using the response surface method (RSM). In the case of an axial fan without the ASF, the backflow gradually increased in the spanwise direction toward the hub and the streamwise direction to the inlet passage (upstream), as the flowrate decreased, and the rotating stall was developed through the quickening-growing-setting period. However, an ASF-attached axial fan stably recovered performance degradation in the stalling flow rates and allowed to form a negative slope to 0.5Φd. This study was mainly based on numerical simulations, while the performance before/after application of the ASF was validated through experimental tests.