Energy saving performance analysis of contra-rotating azimuth propulsor. Part 2: Optimal matching investigation in model scale

Abstract

The propulsive efficiency maximization of contra-rotating azimuth propulsor (CRAP) at model scale is investigated through searching the optimal matching rotational speeds of the forward propeller (FP) and rear propeller (RP) of CRAP based on the potential-based panel method. The hydrodynamic performance of CRAP with changing rotational speeds (FP and RP may have different rotational speeds) are calculated. When the inflow velocity is certain, the cubic spline interpolation method is used to get the equal thrust points at which CRAP has the same thrust with the corresponding conventional propeller (CP). Then, the delivered powers at these equal thrust points are further obtained through cubic spline interpolation method. The rotational speeds of FP and RP at the equal thrust point corresponding to the minimal delivered power are the optimal matching rotational speeds of CRAP. The optimal matching calculations are carried out at different inflow velocities. The results of the optimal matching investigation show that CRAP has the lowest delivered powers when FP and RP have the optimal matching rotational speeds and that the energy saving level decreases with the increase of inflow velocity. The optimal matching rotational speed ratio decreases with the increase of inflow velocity. In general, the delivered powers of CRAP having optimal matching rotational speeds at different inflow velocities are obviously smaller than those of CP.