Numerical Investigation of the Validity of Axial Blade Design

Abstract

The core of the present work is an axial blade design procedure which stands as premises for an optimization tool for axial fans. The initial design assumptions made refer to the computation of the blade angles and the determination of the blade shape. The back-bone of the present work is a design solver which computes inversely the blade shape, based on the assumption that the angle distribution between the inlet and the outlet blade angles is parabolic. The flow-optimized blade shape of an established industrial fan, used in engine-cooling applications, was derived using this design solver. Intensive numerical investigations were carried out for both the industrial and the optimized impellers, and an appropriate performance indicator had to be found. The static-to-total efficiency is an accurate performance indicator and when computing it for both impellers, it was noticed that the optimized blade impeller performs better and a 24% difference in the efficiency curves was observed. Also, by computing the total-to-total efficiency curves, the optimized blade performed better and a 13% difference between the two impellers was found.

Analytical and numerical investigation of the optimum pressure distribution along a low-pressure axial fan blade

“…The increase from γ 1 to γ 2 can be estimated by any type of variation, either linear or higher degree polynomial. According to Pascu and Epple [16], for axial fans a parabolic distribution of the blade angles is appropriate. It was shown by means of streamline analysis that this assumption, made at early design stage, was confirmed by the actual flow angles, thus achieving very good flow-blade congruency.…”

“…After processing the results of the numerical simulations and evaluating the performance of the three designs according to equation (16), the performance charts in Fig. 15 can be plotted.…”