Effects of piston design and lubricant selection on reciprocating engine friction

The interaction between the piston and the liner in a reciprocating engine is of much interest because it affects reliability, noise, and efficiency. This study evaluated various changes to the piston skirt with the specific goal of minimizing friction. An analytical model of the piston, previously developed at MIT, was used to perform parametric studies of various designs in order to predict the effect of each on engine efficiency. The model incorporated hydrodynamic, boundary, and mixed lubrication modes, and it allowed for either fully-flooded or partially-flooded skirts. It also considered the effects of skirt deformation in response to applied loads. A dominant factor influencing net friction between the skirt and liner was the distribution between hydrodynamic lubrication (support by the oil film) and boundary lubrication (direct metal-to-metal contact). Design changes that shifted support from the high-friction boundary lubrication regime toward the hydrodynamic regime generally reduced net friction. For example, the model predicted that if a piston is originally supported largely by boundary contact, increasing the viscosity of the oil can reduce friction by enabling the oil film to sustain a greater load. If, however, the load is already supported primarily hydrodynamically, decreasing the viscosity reduces hydrodynamic drag and may reduce net friction.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Moughon, Luke (Luke Frank)

Advisor dc:contributor.advisor

• Victor W. Wong.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/36247

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/36247