Characterization of oil transport in the power cylinder of internal combustion engines during steady state and transient operation

Abstract

Engine friction, wear, and oil consumption are some of the primary interests for the automotive industry. However, there is currently a lack of understanding of the fundamentals involving oil transport inside the power cylinder. Therefore, improving one area of engine performance, such as friction, may lead to decreased performance in another area, such as oil consumption. This work seeks to address some fundamental aspects of oil transport in the power cylinder through experiments and modeling. A two-dimensional multiple-dye Laser-Induced Fluorescence (LIF) visualization system was implemented in a spark-ignition engine. Real time images of oil distribution were acquired and analyzed for a multitude of operating conditions typically encountered by passenger car engines. Based on experimental observations, major oil flow patterns in the piston ring pack during transient operation were identified and characterized. Physically based models were used to describe and understand the fundamentals of the individual oil transport process. The work shows oil may enter the top ring groove under low load (high vacuum) conditions. After enough time at low load, the oil may interfere with the gas flow into the top ring groove. Thereafter, upon a transition to a higher engine load, the top ring may radially collapse, resulting in an extremely large increase of blow-by gases. Additional work was conducted studying oil transport from the piston to the cylinder liner during steady state conditions. The results show that oil transport to the cylinder liner may be one of the main contributors to oil consumption. Also, analysis of oil transport on the piston skirt was conducted and an overview of the general transport pattern was developed.

(cont.) This work was the first comprehensive investigation of the mechanisms of oil transport in the piston ring pack of internal combustion engines during transient operation. Additionally, the understanding of oil transport to the cylinder liner during steady state operation was enhanced. This work is also the first investigation that developed a general overview of oil transport on the piston skirt. Such understanding of oil transport is a major step to controlling oil consumption during transient and steady state operation.