An Experimental Study of Oil Transport on the Piston Third Land and the Effects of Piston and Ring Designs

Faced with increasing concern for lubricating oil consumption and engine friction, it is critical to understand the oil transport mechanisms in the power cylinder system. Lubricating oil travels through distinct regions along the piston ring pack before being consumed in the combustion chamber, with the oil distribution and dominant driving forces varying substantially for each of these regions. In this work, the focus is on the lowest region in the piston ring pack, namely the third land, which is located between the second compression ring and the oil control ring. A detailed 2D LIF (Two Dimensional Laser Induced Fluorescence) study has been performed on the oil distribution and flow patterns of the third land throughout the entire cycle of a single cylinder spark ignition engine. The impact of speed and load were experimentally observed with the LIF generated real time high-resolution images, as were changes in piston and ring design.

The results reveal the oil flow patterns and timing are consistent and predictable at each operating point. Speed and load variation alter the basic flow pattern through a corresponding change in inertia and gas dragging effect respectively, with ring design variation instigating specific and repeatable phenomenon onto the consistent oil flow pattern. As the majority of lubricating oil consumed in the engine crosses the third land at some point, an understanding of the timing and magnitude of the oil transport processes will allow means to be specifically developed to reduce the net oil flow across the third land towards the combustion chamber. This work forms a foundation for developing oil control strategies for the third land and for identifying how and when oil reaches the upper piston ring pack regions that directly contribute to oil consumption.