CFD Simulation of Connecting Rod Bearing Lubrication

Modern engines are designed to operate at highly rated engine speed and load, which brings up challenges to the lubrication design of main and connecting rod bearings. Damages could occur on rod bearings due to high-speed relative sliding motion. Expensive cross drillings are often seen in today's engineering practice to ensure adequate lubrication in rod bearings. The objective of this study is to establish a methodology for predicting lubrication flows in rod bearings and use it to guide the engineering design.

The high-speed nature of the crankshaft makes it difficult to acquire experimental data during its normal operation for better understanding the flow inside rod bearings and oil circuits. In the present study, the commercial CFD code, FLUENT, has been used to evaluate the flow characteristics within the rod bearings and oil passages connecting main bearing to rod bearing. In order to ensure a continuous oil supply to the rod bearing, the three-dimensional, transient flow in a single rotating reference frame with multiple rotation centers has been solved for rotating speeds ranging from 550rpm to 5200rpm and oil temperature from 50°C to 120°C. The minimum pressure in the feed oil transfer passage to the connecting rod bearing is determined in terms of cavitation. The phenomenon of oil being sucked back into the rod bearings through end gaps due to low local pressure previously observed by Suzuki Shigeo et al. [1] has also been confirmed.