In the previous papers1)3) the authors presented experimental and theoretical data on propeller open characteristics, propulsive performance characteristics, cavitation characteristics, propeller-induced fluctuating pressures and blade stresses of MAU type Conventional Propeller (CP) (MPNO. 80-3), conventional 90° Highly Skewed Propeller (HSP) (MPNO. 80-4) and theoretically designed 72° HSP (MPNO. 80-5).
Presented paper studies flows on HSP blade at ahead and astern conditions and crash astern performance of the ship equipped with HSP.
First, flow visualization tests which examined flows on the blades of CP, 90° HSP and 72° HSP were carried out using depth tuft method and oil film method in order to check up the applicability of propeller theory for estimating performance characteristics of HSP and the difference between flows on the blades of CP and HSP.
Second, crash astern performance simulation for a prototype container ship (SR 183) equipped with CP or 72° HSP was carried out using theoretical method in order to compare crash, astern performance of the ship with CP and that of the ship with HSP.
From results of the study, the following conclusions were obtained;
(1) Near propeller design point, propeller theory is applicable for performance analysis of HSP.
(2) At ahead-reverse condition, propeller theory is not applicable for performance analysis of HSP. At astern-reverse condition, performance analysis of HSP by propeller theory can not be carried out when skew angle and propeller load are excessively large.
(3) Near propeller design point, flow on HSP blade is similar to that on CP blade.
(4) At astern-reverse condition flow on HSP blade is different from that on CP blade. Boundary layer flow on CP face is almost full of turbulent flow. But when skew angle and propeller load are excessively large, the wide range near blade root comes to dead flow zone.
(5) Crash astern performance of the ship with HSP is inferior to that of the ship with CP, though it falls less than backward thrust.
(6) The best way to raise crash astern performance of the ship with HSP is to increase the number of reverse revolution within the allowable range on blade stress.
