Experimental and Mechanistic Study on Current Carrying Friction of Sliding Ring Slide in Shaft-Type Oil Distributor under Different Oil Environments

The issue of current-carrying friction wear in the sliding ring slider of a controllable pitch propeller (CPP) oil distributor under shaft current conditions was addressed through the development of a specialized wear test device. Comparative tests were carried out with and without the application of electrical current in order to assess lubrication performance in bio-oil, mineral oil, and gear oil. Under conditions of low electrical current, the device exhibited significant signs of current-induced friction wear, in addition to substantial oil oxidation and the accumulation of deposits within the bio-oil. Conversely, the level of wear experienced was minimal in both mineral oil and gear oil conditions. These results imply that CPP systems utilising bio-oil encounter a considerable risk of wear under current-carrying circumstances. Quantitative analysis revealed that the wear depth of the friction pair in bio-oil under energized conditions reached 0.02 mm, accompanied by the formation of a phase-transformed layer up to 11.2 μm thick, which was approximately twice that observed in mineral or gear oils. Metallographic evidence confirmed severe arc erosion as the dominant wear mechanism, which was significantly exacerbated by the inferior oxidation stability and higher electrical conductivity of the bio-oil. In engineering practice, the utilisation of alternative lubricants is to be given precedence, and the shaft-type oil distributor is to be electrically insulated.