Analyse der Kolbengruppenreibung und -schmierung von Ottomotoren – Die Bedeutung des Ölabstreifrings

The optimization of the internal combustion engine will continue to play a key role in achieving the climate protection targets defined in Paris. Increasing efficiency has top priority both for small engines in hybrid drives and for large engines in commercial vehicles and construction machinery. Measures to reduce mechanical losses are typically evaluated with dragged friction measurements on the full engine (strip-down analysis). The results show that up to 50% of the total friction losses occur in the piston/cylinder liner tribological system. To analyze the piston assembly friction, a crank angle-based friction force measurement on the single-cylinder engine is used, from which the friction mean effective pressure can be derived as a measure of efficiency. The so-called floating liner engine is first used to assess the friction potential of tangential force reduction of the oil control ring. Since there is always a trade-off between friction and oil consumption, the effect of the reduced tangential force on the oil distribution within the piston assembly is also analyzed. For this purpose, a transparent engine was developed at the institute, which enables the visualization of the lubricating oil flow as well as an evaluation of the oil layer thickness. This combined approach enables a reduction of CO₂ emissions with low oil consumption at the same time. The latter is becoming increasingly important with the future use of synthetically produced fuels (eFuels). Since the combustion of these types of fuel is almost free of particles, the oil entering the combustion chamber remains the only source of particle emissions.