Numerical simulation of the multiphase flow phenomena in the crankcase of an internal combustion engine

Abstract

The flow processes in the crankcase of an internal combustion engine are essential for many sub areas of a combustion engine. Piston cooling, oil transport through the main and conrod bearings or the tribology of the piston assembly are some of them and take place in the crankcase. The oil supply of the liner plays an important role for the friction losses of an engine. Additionally oil aerosols are emerging in the crankcase. The sizes of the droplets are crucial for the oil separator dimensioning. Due to blow-by a part of the crankcase gas flows back to the intake manifold (via the oil separator) and the containing oil in the flow is responsible for additional emissions of the engine. This study introduces a simulation method for the calculation of the multiphase flow phenomena in the crankcase of a four-cylinder diesel engine. All relevant effects have been identified and modeled numerically. The detailed geometry of the crankcase volume and all moving parts of the piston assembly have been considered in the model. To calculate the multiphase flow in the crankcase a discrete particle method has been chosen, where the gas flow is described continuously and the oil flow is modeled with the discrete droplet method. With this method the oil flow and the interaction with the gas flow can be calculated. The computational fluid dynamics results enable new insights into the crankcase flow of an internal combustion engine and therefore statements about the oil distribution in the crankcase can be made. That leads to further knowledge of the transport processes in the crankcase.