A One-Line Correlation for Predicting Oil Vaporization from Liner for IC Engines 2018-01-0162
The increasingly stringent regulations for fuel economy and emissions require better optimization and control of oil consumption. One of the primary mechanisms of oil consumption is vaporization from the liner; we consider this as the “minimum oil consumption (MOC).” This paper presents a physical-mathematical cycle model for predicting the MOC. The numerical simulations suggest that the MOC is markedly sensitive to oil volatility, liner temperature, engine load and speed but less sensitive to oil film thickness. A one-line correlation is proposed for quick MOC estimations. It is shown to have <15% error compared to the cycle MOC computation.
In the “dry region” (between top ring and OCR at the TDC), oil is depleted due to high heat and continual exposure to the combustion chamber. MTU Friedrichshafen GmbH, who develops and produces large high-speed engines and propulsion systems, conducted experiments on an single-cylinder diesel engine, which is only used for test purposes and measured the oil content in the exhaust gas via radioactive markers. This measured oil consumption was a result of both oil transport and oil vaporization. However, the MOC prediction including the dry region without treatment to oil film thickness and properties unreasonably exceeded the measured oil consumption. Therefore, excluding the dry region is believed to be a better gauge for lower bound estimations of the MOC.