Effect of leaned blades on the aerodynamic performance of contra-rotating open rotor

The contra-rotating open rotor (CROR) engine has gained attention for its outstanding fuel-saving potential. Attention needs to be paid to the propulsion efficiency of the contra-rotating open rotor, as it is the key to realizing the engine’s fuel-saving advantage. In this paper, the performance of CRORs with different lean angles is investigated by numerical simulation. Furthermore, the mechanism of the influence of leaned blades on the propulsion efficiency of the CROR is analyzed. The results show that the positive leaned blades (pressure-surface down) significantly improve the propulsion efficiency of the CROR, with a maximum improvement of 1.34%. In contrast, the negative leaned blades (suction surface down) reduce propulsion efficiency. Due to the radial equilibrium equation, the positive lean increases the radial pressure gradient. The increased gradient enhances flow on the suction surface and reduces the flow reversal region, thus improving the propulsion efficiency. At low advance ratios, the enhanced radial flow due to the leaned blades makes the optimization less effective. By comparing the inlet conditions of the front and rear rotors, it was found that the front rotor was less likely to have a flow reversal region compared to the rear rotor. If a flow reversal region occurs in the channel, it is necessary to introduce leaned blades. The most recommended lean angle is the one that makes the flow reversal region disappear exactly.