Explosion Mechanism of Lubricating Oil Droplets in High-Temperature and High-Pressure Combustion Environments

Abstract

Lubricating oil-induced pre-ignition is a critical issue that requires attention in downsized gasoline engines and marine low-speed two-stroke natural gas engines. As a result, the ignition behavior of lubricating oil at high temperatures and pressures has been extensively studied. In some cases, when studying the ignition of oil droplets using a rapid compression machine, an explosion-like behavior of the oil droplets is observed, producing a soot cloud that can spread throughout the combustion chamber, especially when the ignition delay time of the ambient gas is short. To gain detailed insights into the mechanism of oil droplet explosion, the explosion process under initial pressures from 13 to 31 bar and temperatures from 700 to 1600 K was visualized using high-speed photography and microphotography on a rapid compression machine. The effects of temperature and shock waves were experimentally investigated, and droplet deformation after shock wave impact was calculated using a simple model. The results demonstrated that high temperature does not have a significant effect on droplet explosion under the conditions studied in this paper. The shock wave impact is the primary cause of the droplet’s explosion.