Influence of the rotor blade aspect ratio on the performance of an axial fan

Abstract

An axial fan with four different number of blades for the rotor is investigated. In this contribution varying the blade aspect ratio means the number of blades is changed while every other dimensionless design parameters and the design point are kept constant. By varying the blade aspect ratio, the length of the blades alters and as a result the Reynolds number which is related to the chord length of each blade is changed as well. The considered Reynolds numbers are lying between 2.38 × 105 and 7.13 × 105. For the stator the blade aspect ratio as well as the spacing ratio are the same during the investigation.For comparison and validation both numerical and experimental investigations are performed. For the numerical investigations, due to the low Reynolds numbers the k-ω-SST transition model with the intermittency function is applied. Transient simulations are carried out. The experimental investigations are performed a pipe test bench. The results are compared in terms of performance differences for part load, overload and design conditions. The flow structure in the rotor passages is visualized and compared using the numerical results to show the influence of the blade aspect ratio on the performance.