This study focuses on the shaft power at the neutral angle of a controllable pitch propeller to analyze the change in the required power due to propeller fouling. It is named and defined as a power for keeping propeller’s rotation (RP) because a propeller does not generate the net thrust to push the hull but dissipates the power to keep its constant speed. Statistical analysis was conducted using a decade of the observed data from a research vessel. This study assumed that the change in RP can be considered as an indicator showing the state of propeller fouling. In addition, the state of fouling on the hull can be estimated indirectly based on RP because the data correlated the shaft power under several operating conditions with RP on the same voyage. The fouling state was classified into three conditions based on RP. The comparison of shaft power at the same ship speed between the clean condition and the serious fouled condition showed that the shaft power was increased by 35% on average due to fouling. When the ship navigates under 10 knots, propeller fouling has a larger impact on the increase in shaft power than hull fouling.

本研究重点关注可调螺距螺旋桨中性角处的轴功率，以分析螺旋桨污垢导致所需功率的变化。它被命名和定义为保持螺旋桨旋转的功率（RP），因为螺旋桨不产生推动船体的净推力，而是消耗功率以保持其恒定速度。使用研究船十年来的观测数据进行统计分析。本研究假设RP的变化可以被视为显示螺旋桨污垢状态的指标。此外，可以根据RP间接估计船体的污垢状态，因为该数据将多个操作条件下的轴功率与同一航次的RP相关联。根据RP将结垢状态分为三种情况。相同航速下清洁工况与严重污损工况的轴功率对比表明，污损导致轴功率平均增加35%。当船舶航行速度低于10节时，螺旋桨污垢对轴功率增加的影响比船体污垢更大。