Abstract
Keywords: Combustion Engine, Friction, Simulation
Over the past twenty years CAE has made tremendous progress. CAE has become an integral part of the combustion engine development. The main benefits of CAE are savings on cost and timing. Through CAE costly prototypes can be avoided and the development process can be shortened. In addition CAE can in many cases answer questions which cannot be answered by tests, firstly because additional data can be extracted from CAE results which are not available from real hardware tests, secondly because CAE can separate the influence of different parameters which cannot be modified individually in a test.
While CFD and FEM as well as multi-body dynamics are well established tools in the engine development process, friction and wear calculation has been less reliable for quite some time. Consequently friction prediction is becoming more and more important because friction reduction offers an additional potential for fuel consumption reduction. At the same time reliability requirements are getting more stringent which requires more accurate models for the prediction of wear.
Friction and wear occurs at different locations in the engine. The new tool presented in this paper is targeting on the simulation of friction and wear for all line contacts and will enable the user to make upfront design decisions based on CAE. Areas of application are valve train systems, gear drives,fuel pump drives in gasoline and diesel engines [MUES03], but also similar contact cases in other industries, e.g. rail contacts.
In the following a model will be described for the Thermo Elasto Hydrodynamic Lubrication (TEHL) simulation of a cam tappet contact under mixed friction conditions. The simulation in the mixed friction regime is an important step to wear calculation. Predictions of the severity of the dry contact are possible by calculating the real contact area or the film thickness parameter. Besides, predictions of the intensity of the dry contact can be made by calculating a critical contact pressure, which is given by the contact pressure on the asperities. The simulation model is also a prerequisite for the future simulation of the run-in behaviour of components, because surface parameters can be changed easily.