EFFECTS OF BLADE SOLIDITY AND ASPECT RATIO ON A 0.5 HUB-TO-TIP RATIO TUBE-AXIAL FAN

Solidity and aspect ratio are the two geometrical parameters bridging the fan preliminary sizing with the blade aerodynamic design. In a previous work, the topic has been investigated by experimental testing of 16 propeller fans with 0.2 hub-to-tip ratio, all designed for approximately 0.075 flow rate coefficient and 0.008 pressure coefficient. As a further research step, this paper investigates the influence of solidity and aspect ratio on the global aerodynamic performance of 0.5 hub-to-tip ratio tube-axial fan rotors. Aim of the work is twofold: first, to extend the aerodynamic performance data set of comparable axial-flow industrial fans characterised by different blade solidity and aspect ratio; second to investigate by experiments the role of the hub-to-tip ratio on the effects of the two design parameters. To this end, 18 additional fans with 0.5 hub-to-tip ratio were designed and tested according to ISO-5801, and the collected data were compared to those already available from the 16 fans with 0.2 hub-tip ratio. The results confirm that the aerodynamic performance at best efficiency operation is primarily set by the hub-to-tip ratio. Solidity plays a role comparable to the hub-to-tip ratio only within the minimum-to-low solidity range, whereas the aspect ratio contributes to the fan efficiency – in high hub-to-tip ratio designs only – and to the best efficiency flow rate coefficient – in low hub-to-tip ratio designs only.