Simulation of twin land oil control ring in heavy duty diesel engines

Abstract: With today’s striving towards reduction of fuel consumption it is moreimportant than ever to understand how different components in theinternal combustion engine function. There is a need for tools that canbe used to investigate and predict the result of specific design changesmade on the components. In this work, the mechanics and the tribologyof the power cylinder unit and more specifically the operation of thetwin land oil control ring (TLOCR) is investigated. In heavy duty dieselengines (HDDE), TLOCR are typically used. The TLOCR plays a veryimportant role in the engine since it is supposed to distribute the correctamount of oil on the liner to lubricate the other rings. It is importantthat the TLOCR does not leave too much oil on the liner for the twotop rings since it could lead too high oil consumption. In a HDDE thepiston assembly is the largest contributor to frictional losses where thepiston ring pack accounts for the major part of this. The oil control ringhas the largest contribution to frictional losses in the piston ring packtherefore making it very interesting to study from a fuel consumptionperspective. The objective of this thesis is to develop a simulation toolthat can be used to quantify design changes to the TLOCR. Such as thedimensions of the ring itself but also ring tension, running land profileand out of roundness of the cylinder liner.The model developed in this work accounts for the tribological interfaceof the TLOCR against the cylinder liner and piston ring groove aswell as the elastic deformation of the ring and the ring dynamics withinthe piston ring groove. The actual ring cross section is modelled in orderto account for the full three dimensional elastic deformation of the ring.By solving all of these problems as a coupled system it is believed thatthe entire operation of the oil control ring could be understood in a betterway than earlier and open up new optimisation possibilities for theTLOCR. The full ring is modelled in order to account for out of roundcylinder liners. Since the cylinder liner in an engine will always havesome deviation from perfectly round this is important. The model cantherefore be used to investigate the effect on oil distribution by reducedring tension which will affect the frictional losses of the system.

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