A Numerical Investigation of the Vaporization Process of Lubricating Oil Droplets under Gas Engine Conditions

The abnormal combustion resulted by the auto-ignition of lubricating oil is a great challenge to the development of Otto-cycle gas engines. In order to investigate the mechanism of lubricating oil droplet vaporization process, a crucial sub-process of auto-ignition process, a new multi-component vaporization model was constructed for high temperature and pressure, and forced gas flow conditions as encountered in practical gas engines. The vaporization model has been conducted with a multi-diffusion sub-model considering the multi-component diffusivity coefficients in the gas phase. The radiation heat flux caused by ambient gas was taken into account in high temperature conditions, and a real gas equation of state was used for high pressure conditions. A correction for mass vaporization rate was used for forced gas flow conditions. Extensive verifications have been realized, and considerable results have been achieved. Finally, the vaporization model is used to investigate the vaporization characteristics of lubricating oil droplets under various conditions. The research results show that using new lubricating oil droplets with improved chemical characteristics, or limiting the droplet physical characteristics, or controlling the ambient conditions should reduce the vaporization rate of the lubricating oil droplet in the gas engine.