Under the background of actively advocating the concept of the green development of China, water-lubricated bearings have been widely used in ship and marine engineering equipment industries because of their advantages, such as low cost, good heat dissipation and environmentally friendliness. However, because water has low viscosity and poor film-forming ability, water-lubricated bearings are prone to rupture of water film between friction pairs under severe working conditions, which leads to bearing wear failure. Moreover, wear failure can induce vibration and noise of water-lubricated bearings, and thus their service lives can be affected. Therefore, how to prevent water film failure is one of the key problems, in particular, when water-lubricated bearings are subjected to short-time severe working conditions.

In order to solve these problems, our research group had proposed a new idea of using a small quantity of lubricating oil as the secondary lubricating medium to temporarily inject it into the contact region when water-lubricated bearings encounter severe working conditions, so as to improve the bearing capacity of water-lubricated bearings and achieve the purpose of temporary risk aversion. In our previous work, this proposed idea had been proved to have a remarkable improvement in bearing capacity and a reduction in friction and wear of water-lubricated bearings, thereby achieving temporary risk aversion.

In the current work, emulsifying oil was selected as the secondary lubricating medium, and the MRH-3 high-speed block-on-ring test rig was used to evaluate the friction and wear performance of Thordon material under different working conditions with the lubrication of pure water and water with a small quantity of secondary lubricating oil, complemented by CFD simulations to elucidate the underlying mechanisms. Meanwhile, the difference of wear surfaces of different material test blocks was observed and analyzed by the conformal microscope. Results showed that when the oil supply quantity, oil supply rate and the applied load were kept unchanged, the friction coefficient of the Thordon material changed with different ring rotational speeds after the injection of a small quantity of emulsifying oil in the water environment. Results obtained from CFD simulations conducted over a 10-minute duration confirmed that oil film remained adhered to the ring surface to participate the lubrication even after the oil injection was ceased. Compared with the surface observation of the Thordon test blocks under different working conditions from the conformal microscope, the surface wear track width of the Thordon material gradually increased with the increase of the applied load and the ring rotational speeds. It was also found that the width of wear tracks of the Thordon material was wider than that of the NBR material under the same working conditions after the injection of the emulsifying oil. The current research work could provide the data support for the selection of materials of water-lubricated bearings.