EFFECT OF SOLIDITY AND ASPECT RATIO ON THE AERODYNAMIC PERFORMANCE OF AXIAL-FLOW FANS WITH 0.2 HUB-TO-TIP RATIO

Aspect ratio and solidity play complementary roles in the aerodynamic design of axial fan rotor blades. Few studies have experimented the effect of the aspect ratio of rotor blades on the performance of low-speed axial fans or on its interaction with blade solidity in terms of fan aerodynamic performance. This study examined the selection of the solidity and blade aspect ratio in the preliminary design of low-pressure industrial fans with minimized hub-to-tip ratios. The aim of this study was to make available to the fan community experimental data that allow determination of the optimal aspect ratio as a function of the blade solidity. Various aspects of the performance of 16 prototypes of a 315-mm-diameter propeller fan were compared. The industrial fan prototypes all had a hub-to-tip ratio of 0.2 and were derived from four baseline designs conceived to ideally achieve the same best efficiency operation with different values of the aspect ratio. In addition, the prototypes' assemblies were conceived to allow operation with different blade counts, i.e., with different rotor solidities at a fixed blade aspect ratio. The aerodynamic performance of the fans, measured in accordance with the ISO-5801 standard, was evaluated to assess the sensitivity and trends of the fan pressure and efficiency with respect to the blade aspect ratio and solidity. The measured effects of the aspect ratio and solidity are discussed on the basis of data available in the literature. The results of the experimental analysis were used to formulate general guidelines for the preliminary design of propeller fans with minimized hub-to-tip ratios.