Characterization and Modeling of Rubbing Friction in a Motored Four-Cylinder Internal Combustion Engine

Abstract

<p>While many aspects of the internal combustion engine contribute to its fuel efficiency, internal friction warrants special attention due to the relatively large degree of losses it represents, as well as a nearly universal application to all engines. Internal friction is therefore an important consideration in the design of modern engines and will remain so in the conventionally powered and hybrid vehicles of the near future.</p> <p>Measurement and characterization of internal engine friction is a significant first step towards engine modeling, attempts to reduce friction, and further applications related to engine condition monitoring or control. In order to measure the friction losses internal to a Ford 2.0L 4-cylinder engine a dedicated dynamometer test stand was designed and constructed. This test stand allowed the direct measurement of the frictional losses encountered by the engine in the motored state from low to moderate speeds. This data was then used to update and fit a physical, component-based friction model to the engine. A complete engine model known as the mean value engine model (MVEM) was then augmented with the verified friction model for simulation of the running engine. Its predictions were compared to a limited amount of available fired-engine data, demonstrating a general fit which could be improved with additional data.</p> <p>The dynamometer test stand created is a viable tool for future engine friction testing, especially with partial engine disassembly or varying engine oil (operating) temperatures, or for future investigations of other rotating equipment.</p>