Gas Bubble Development in Connecting Rod Lubrication Systems Caused by Oil Aeration

To further reduce the fuel consumption of internal combustion engines, also the friction losses must be minimized. This requires a borderline dimensioning of hydrodynamic cranktrain bearings. In order to realize this without the risk of failures, detailed modeling of the hydrodynamic effects in the bearings is becoming increasingly important. In that regard, several very advanced and powerful simulation methods already exist, such as mass conservative thermal elasto-hydrodynamic (TEHD) bearing simulations based on the 2-dimensional Reynolds equation or even full 3-dimensional flow models based on the Navier-Stokes equations. However, these simulation approaches usually consider the main and connecting rod bearing individually. This means that these approaches assume that each bearing has its own ideal oil supply source. Since many publications have already shown that the oil supply cannot be regarded as idealistic, this paper focusses on the supply conditions of a connecting rod bearing. Thereto, a novel simulation approach is presented, which is based on a transient 3D-CFD multiphase flow simulation including the ability of gas dissolution and diffusive mass transfer. The model determines the transient pressure behavior and the gas bubble development in the oil supply system of a connecting rod bearing. It allows to visualize the flow behavior and the existence of gas bubbles in order to get a detailed impression of the physical occurrences. The results of this publication can serve as an important basis for the definition of more detailed boundary conditions for hydrodynamic bearing simulations.