Browse Publications Technical Papers 2019-01-0305
2019-04-02

Gas Content in Lubricants of Modern Powertrain Systems – Development of a Continuous Volumetric Measurement Method 2019-01-0305

The demands on the lubrication systems of modern powertrains are constantly increasing. Besides the elementary lubrication and cooling tasks in internal combustion engines and transmissions for cylinder liner and piston, bearings, gear and chain drives or the valve train, the oil system must increasingly fulfil additional hydraulic functions. Examples are variable valve train devices or variable compression ratio systems. To reduce the mechanical losses caused by the oil pump and its drive for enhanced efficiency, variable capacity oil pumps are increasingly being introduced in latest engine designs. This additionally complicates the reliable simultaneous fulfilment of all the aforementioned tasks, as oil pressure and volumetric oil flow are to be reduced as much as possible for best mechanical efficiency. A parameter often underestimated concerning the reliable operation of lubrication systems in engines and transmissions is the gas content in the oil. Undissolved gas has a significant impact on various physical parameters of a lubricant such as viscosity and compressibility. Both are crucial especially for a reliable function of the new hydraulic systems. To address this issue, FEV has improved its static volumetric measurement apparatus for determining the gas content in an oil sample. Furthermore, a device utilizing an all new continuous volumetric measurement method has been developed. This technique enables direct, accurate and reproducible measurements of the gas content in dynamic testing scenarios. At first, the paper addresses the fundamental necessity for gas content measurements during powertrain system development. Then the advantages of volumetric measurement methods are discussed and the static and continuous approach for precise measurements of the gas content are presented.

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