Parametric study on the aerodynamic performance of a ducted-fan rotor using free-form method

Abstract

In this paper, the effects of various parameters, especially three engineering parameters (twist, sweep, lean), on aerodynamic and structural performance of the fan blade were investigated. The change of blade geometry was realized by the free-form deformation (FFD) approach, which was more flexible than traditional parametric methods. A coupled iterative loop was used in a multi-objective optimization process considering two operating conditions. Not only the effect of a single parameter, but also the coupled effects of any two of them were studied. From the Design of Experiment (DoE) results, it was found that the twist and sweep have a relatively strong influence on aerodynamic performance compared with the lean. In addition, it's noteworthy that the effect of twist varied at different operating conditions. At a relatively low mass flow rate, an excessive twist caused a sudden drop in the total pressure ratio. Optimization results showed that the maximum blade stress was dominated by the twist, and a backward sweep at mid-span decreased the stress on the blade surface. The design of twist (DoT) and sweep (DoS) provided a significant improvement of total pressure ratio ranging from 5% to 15% approximately throughout the operating range. Although the peak efficiency was increased by about 1.3% for DoT, the strong tip leakage vortex caused a premature rotating instability compared with the baseline design.