An Experimental and Theoretical Study of the Contribution of Oil Evaporation to Oil Consumption 2002-01-2684
Engine oil consumption is an important source of hydrocarbon and particulate emissions in automotive engines. Oil evaporating from the piston-ring-liner system is believed to contribute significantly to total oil consumption, especially during severe operating conditions. This paper presents an extensive experimental and theoretical study on the contribution of oil evaporation to total oil consumption at different steady state speed and load conditions.
A sulfur tracer method was used to measure the dependence of oil consumption on coolant outlet temperature, oil volatility, and operating speed and load in a production spark ignition engine. Liquid oil distribution on the piston was studied using a one-point Laser-Induced-Fluorescence (LIF) technique. In addition, important in-cylinder variables for oil evaporation, such as liner temperature and cylinder pressure, were measured. A multi-species cylinder liner oil evaporation model was developed to interpret the oil consumption data.
A linear relation between oil consumption and coolant outlet temperature was observed during different steady state speed and load conditions. This behavior was observed for two oils with different volatility. Moreover, it was found that reducing oil volatility led to an improved oil economy, especially at high engine loads. Further analysis with the liner evaporation model suggested that oil evaporating from the liner was responsible for the dependence of oil consumption on coolant outlet temperature.