A study of the lubricant transport across the piston rings in large two-stroke marine diesel engines is presented.
Cylinder lubrication systems for large two-stroke marine diesel engines do not support recirculation of the lubricant and it is lost after usage. The lubricant is expensive and may contain several polluting additives. Reducing the lubricant consumption is economically profitable and reduces emissions. The physical mechanisms of lubricant transport across piston rings are investigated and presented in this work.
The structure of the numerical model is described. The work covers solving Reynolds equation by the finite difference method, force equilibrium of the piston ring by considering the lubricant stiffness, transient mass conservation as well as the influence from rough surfaces in the hydrodynamic effects and asperity contact.
Theoretical investigations of the influence by piston ring curvatures for fully flooded and starved conditions as well as different lubricant profiles on the liner are conducted. Results are presented for the lubricant consumption and asperity contact friction as functions of lubricant injection positions on the liner, piston ring asymmetries and curvatures.
The knowledge gained in the mechanisms controlling the lubricant consumption can be utilized for optimizing the cylinder lubricant injection system for reduced consumption and asperity contact friction between the surfaces.
The method of laser induced fluorescence is presented and applied in a reciprocating test rig. It mimics the lubrication conditions between a piston ring and cylinder liner. Results for friction forces and minimum film thicknesses are presented.
Supervisor:
Professor Peder Klit, DTU Mechanical Engineering
Co-supervisor:
Senior Research Engineer, PhD Anders Vølund, MAN Energy Solutions, Denmark
Examiners:
Associate Professor Casper Schousboe Andreasen, DTU Mechanical Engineering
Professor Martin Priest, University of Bradford, United Kingdom
Professor Arto Lehtovaraa, Tampere University of Technology, Finland
Chairman:
Associate Professor Niels Leergaard Pedersen, DTU Mechanical Engineering