Three-body Abrasive Wear Surface Characterization of Military Diesel Engine Piston Rings and Cylinder Bores

Two 50-hr engine dynamometer tests were conducted on 12-cylinder diesel military engines with differing piston ring sets. Engine A exhibited more than double the oil consumption over engine B. An investigation was conducted to explain why the oil consumption differed by employing several posttest analytical techniques including cylinder bore geometry measurements, surface metrology, wear characterization, and chemical analysis on the piston rings and cylinder wall coatings. The 3D colormaps of cylinder bore deformation showed uneven volumetric deformation through the piston stroke instead of 2D plane deformation. It was found that the primary reason of high oil consumption was direct loss of sealing between the piston, piston ring and cylinder bore due to predominately abrasive wear, three-body abrasive wear and bore polishing. Furthermore, the compromised sealing of the combustion chamber led to blow-by. Carbon deposits, corrosive byproducts, surface abrasives, loss of desired surface finish, and insufficient lubrication contributed to severe wear on the running face of the compression rings and cylinder wall near top dead center. The piston rings of Engine B appeared to reduce oil consumption by having a superior barrel contour of the running face as well as being softer by roughly 30%. It was also noted that the cylinder walls were not plateau honed for either engine.