A study of the friction (piston-liner interaction) in internal combustion engines using a Floating Liner Engine

Abstract

With the increasing interest in decreasing the environmental impact from internal combustion engines as well as increasing the fuel efficiency has led to deeper investigation into the components of the engine. The mechanical friction in an engine is a major concern, any improvements or reductions in friction can have large implication on the' efficiency of the engines. This thesis focuses on the piston/ ring pack assembly and its contribution to friction. It investigates several key components and trends in friction for the piston/ ring pack assembly, specifically the trends related to the oil control ring and the liner surface. The Floating Liner Engine is used in this study to isolate results from different components. The data collected can be used for comparative analysis and to identify trends in the friction trace. The thesis starts with describing the Floating Liner Engine system at MIT in detail. Both the data collection and the hardware systems are described as well as the test capabilities of the Floating Liner Engine. The results used in the thesis have been collected using the motoring condition. The oil control ring plays a key role in controlling the supply of oil to the top two rings and hence has a higher tension that the top two rings. This leads to the oil control ring having a significant contribution to the total friction of the system. The two most prevalent oil control rings used in the industry are the twin land oil control ring (TLOCR) and the three piece oil control ring (TPOCR). The thesis investigates the effect of changing liner roughness on the friction of the TLOCR. A comparison between the TLOCR and the TPOCR is also performed using the same liner surfaces. The results from these studies show a marked difference between the friction traces from the two oil control rings.