Effect of sulfur dioxide in recirculated exhaust gas on wear within diesel engines (relationship between wear and amount of SO2 absorbed by lubricating oil film)

In both spark ignition engines and diesel engines, exhaust gas recirculation (EGR) is well known as an effective technique to reduce emissions of nitrogen oxides. However, it has not yet been applied practically to heavy-duty diesel engines because the wear on piston rings and cylinder liners is increased by EGR. It is widely accepted that sulfur dioxide in burnt gas is strongly related to this wear increase. This paper proposes a numerical model to clarify the mechanism of wear which estimates the amount of sulfur dioxide absorbed by lubricating oil film. The calculated results show that the concentration of sulfur dioxide in lubricating oil film is increased with the increase in the rate of EGR and the reduction in engine speed, and is decreased with the decrease in engine load. The measured amount of wear on piston rings and cylinder liners is related to the concentration of sulfur dioxide in lubricating oil film.