Experimental Investigation of the Unsteady, Three-dimensional Fluid Cavitation in Lubricant Flow

• Applicant: Professor Dr.-Ing. Peter Reinke
• Subject Area: Fluid Mechanics ; Hydraulic and Turbo Engines and Piston Engines
• Term: from 2021 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462581008

Hydrodynamic journal bearings are compact and guarantee a nearly wear-resistant operation. These features make these bearings the first choice for many applications. However, under particular operational conditions cavitation can cause bearing failures. It is already known that a high eccentricity combined with a fast thickness change rate of the lubricating film characterize the sections of the load cycle that are prone to cavitation.The applicant has developed an approach, which combines eccentricity and film thickness change velocity into one factor. This factor describes the risk of cavitation and provides a similarity law which enables the transfer of real bearing data into a model experiment. Numerous papers deal with crankshaft drive related bearing failures caused by cavitation. Out of the full range of possible applications where cavitation problems are found this application focusses on diesel powered internal combustion engines. Diesel engines are reliable and efficient which makes them a key technology that bridges the time until alternatively powered engines which solve the CO2-challenge become fully available. To maximize the scope of diesel applications exhaust gas treatment and dual fuel operation become mandatory. In the case of dual fuel operation it is necessary to maximize the efficiency by pushing the load towards the knock limit due to a lower heating value of gaseous fuels compared to diesel. However, the operation closer to the knocking limit will increase the stress on all engine components which in case of the bearing can result in a higher risk of cavitation. It is the goal of this application to verify the applicant’s approach predicting the cavitation risk and to reach a better understanding of the mechanisms which drive suction cavitation inside the lubricating film of journal bearings by carrying out specific experiments. This research project will include measurement campaigns at a model bearing experiment utilizing a specifically designed cavitating fluid which yield data necessary for the validation of the numerical results that are computed by means of an unsteady, three-dimensional and 2-phase code.It is the goal of this application to investigate the dynamics of bubble formation in relation of the unsteady variation of the film thickness and to identify areas with a high erosion potential.It is the goal of this application to validate a numerical model with the experimental data produced by this project yielding a tool that can be applied to simulate the lubricant flow in journal bearings under unsteady operating conditions.It is the goal of this application to provide the means in form of a model experiment that offers the possibility of an application on other forms of cavitation, which are typical for hydrodynamic journal bearings.

• DFG Programme: Research Grants