Analysis of Optimization of Lean and Sweep Influence on Highly Loaded Transonic Tandem Rotor

To study the effects of the optimization of 3D sweep and lean on the performance of tandem rotor, an automatic optimization system of 3D sweep and lean of tandem rotor was developed based on Kriging model and NURBS method. The optimization system is validated by optimizing a highly loaded transonic tandem rotor. The effects of sweep optimization, lean optimization and composite optimization of lean and sweep on the performance of the tandem rotor were respectively discussed. The results show that the optimization of 3D sweep and lean can improve the performance of tandem rotor. Compared with original tandem rotor, at design condition, the efficiency of forward sweep rotor, positive lean rotor and the composite of lean and sweep rotor were improved by 1%, 1.03% and 1.47%, respectively. The stability margin of positive lean rotor was raised by 23%, while the stability margin of forward sweep rotor and the composite of lean and sweep rotor had a little decrement. Besides, forward sweep blade can improve the aerodynamic performance of the tip and the middle section of highly loaded transonic tandem rotor, but deteriorate the aerodynamic performance of the hub. Positive lean blade can enhance the aerodynamic performance of most span of tandem rotor. The reason for sweep and lean optimization enhancing the efficiency of tandem rotor is that sweep and lean optimization reduces the shock Mach number of rotor passage normal shock, but does not change the position of normal shock.