Photo Credit: VKA


MTZ Project Reports: Oil entry via piston top land

Investigations of the oil balance at the piston are important for optimizing future engine concepts with regard to combustion processes and emissions. As part of the FVV project Fuel in Oil II (1225), the Institute for Combustion Engines (VKA) at RWTH Aachen University developed and used a measurement method for detailed investigations of the lubricating film thicknesses on the piston top land. At the same time, the Institute for Analytical Measurement Technology Hamburg e. V. (IAM-Hamburg) developed an exhaust gas analysis method to investigate the oil emission mechanisms.

Downsizing concepts with gasoline direct injection require new standards in combustion process development [1]. In earlier research work, it was possible to prove clear interrelationships to the entry of lubricating oil into the combustion chamber both for pre-ignitions [2] and particle emissions [3].Representing the system cylinder–piston–piston ring, to which the highest contribution to the oil input can be attributed [4], the research project focused on the mechanism of throw-off of oil droplets from the piston top land as a result of inertial forces. One objective was to carry out measurement-based investigations on the oil balance at the piston top land as a source of a possible oil entry and numerical investigations on the oil entry behavior based on this. In addition, measurement-based analyses of aerosol and oil emissions were used to reach conclusions about the fundamental mechanisms involved.

The newly developed measurement methodology based on an interferometric layer thickness measurement method can be used for crank angle-resolved quantification of the oil accumulation at the piston top land and description of the oil film dynamics due to piston acceleration. Multiphase simulations initialized with these measurement results to investigate the oil transport phenomena at the top land illustrate the mechanism for throw-off of oil droplets from the piston as a result of inertial forces. Simultaneous measurements of oil and aerosol particle emissions show a strong correlation.


[1] Willand, J;. et al.: Limits on downsizing in spark ignition engines due to pre-ignition. In: MTZworldwide 5/2009, pp. 56-61
[2] Dahnz, C.; Han, K.-M.; Magar, M.: Vorentflammung bei Ottomotoren: Untersuchung des Auftretens und der Ursache von Selbstzündungen vor Zündungseinleitung bei aufgeladenen Motoren mit hohem Verdichtungsverhältnis. Final report FVV-Project No. 931, 2010
[3] Dageförde, H.: Partikel bei Otto-DI: Untersuchung von Maßnahmen zur Reduktion der Partikel-Anzahlemissionen bei Otto-DI-Motoren. Final report FVV-Project No. 1046, 2013
[4] Völtz, M.: Einfluß des Motorenöls auf den Ölverbrauch: quellen und Mecha-nismen des Ölverbrauchs im Motor. In: Krafthand 12/1997, n. p.

Project profile

The FVV in the MTZ and ATZ magazine

Results from Industrial Collective Research are accessible to all interested parties and thus final reports of FVV research projects will be presented to the public at our conferences in spring and autumn. In order to further promote the transfer of knowledge and the expansion of the prime movers innovation network, we publish articles on individual projects with particularly interesting new insights in the world's leading specialist magazines for the engine and vehicle industries. MTZ / ATZ and FVV have been working together successfully in this field for many years.


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