Experimental study of cylinder oil stripping behavior at the scavenge port of a low-speed two-stroke engine

The stripping of cylinder oil at the scavenging ports of low-speed two-stroke marine engines is one of the main sources of floating oil droplets existing in cylinders. The combustion of these oil droplets is one of the major reasons of PM emissions and pre-ignition for dual-fuel engines. In order to investigate the stripping behavior, a prototype model and a test bench were set up to carry out the experiment of cylinder oil stripping behavior and single droplet deformation under different conditions. Meanwhile, a CFD model was established to analyze the actual scavenging flow field, and the verification results were obtained: in the case of excessive lubrication, a considerable amount of cylinder oil remains on the upper surface of the scavenge ports. Such cylinder oil can be blown into the cylinder when the ports are opened. Then the oil droplets floating in the cylinder or attaching to the exhaust valve form potential spontaneous combustion points, which leads to the worsening of PM emissions and the threat of pre-ignition, the most harmful abnormal combustion for Otto-cycle dual-fuel engines.