SAE International Numerical Simulation Study of Carbon Build-up and Oil Consumption in a Heavy Duty Diesel Engine 2012-01-1326

Nowadays, the use of numerical simulations is an important tool in order to optimize the engine and components behaviors, directly contributing to the emissions and lead-time development project reduction. With the increase of engine thermal specific loading, excessive piston carbon build-up may be an issue, eventually causing liner polishing and excessive Lube Oil Consumption (OC). During the development of a Cummins heavy duty 8.9L engine, preliminary engine test results indicated excessive OC levels, above the engine specification limits. Also, a considerable carbon build-up, mainly in the second ring groove, was observed. This paper presents the application of piston rings numerical simulation to predict the piston ring pack behavior and evaluate potential sources of OC which may explain the excessive values obtained in engine tests. After that, the effect of relevant geometric parameters in the ring dynamics stability was analyzed and a proposed Power Cylinder Unit (PCU) was recommended as a potential solution for the excessive OC. Endurance engine test was performed using the proposed PCU from the numerical simulation and the results showed a significant OC reduction. Then, a complementary study was done in order to understand the effect of the carbon build-up in the ring dynamics behavior and OC. Some possible mechanisms leading to the observed blow-by and OC spikes observed during the engine tests are discussed.