Incorporation of forward blade sweep in preliminary controlled vortex design of axial flow rotors

A new controlled vortex design (CVD) method has been presented herein, incorporating forward blade sweep (FSW) in the preliminary design phase of axial flow rotors. Supplementing the traditional quasi-two-dimensional (Q2D) technique applied to CVD rotors of notable radial flow, the new method enables a more accurate consideration and control of blade aerodynamics along the three-dimensional suction side flow paths, where the majority of loss is generated away from the endwalls. For this purpose, the new method unifies Q2D and quasi-three-dimensional (Q3D) blade design approaches for CVD rotors. The incorporated Q2D and Q3D approaches can rely on traditional cascade correlations. The Q3D approach is to be aided by computational fluid dynamics. In contrast to the view dominating in literature that sweep is prescribed arbitrarily in preliminary design, the new method serves with the FSW angle distribution as design output. This means that the favourable blade stacking geometry is a result of the proposed preliminary design process. A design case study has been presented for demonstrating the consistency and advantages of the proposed method. At the design flow rate, fair agreement was found between the simulated and modelled three-dimensional flow features for the FSW rotor. Furthermore, moderation of total pressure loss was observed on the suction side away from the endwalls, leading to efficiency gain.