An experimental investigation on the active piston pin oil supply on a high-speed diesel engine under deformation influence

Abstract

Within this work an existing active lubrication system, that is, a direct feed of lubrication oil from the connecting rod big end bearing to the small end bearing, is investigated in detail on a high-speed Diesel engine by measurement and simulation. The methodology includes the insertion of three highly dynamic pressure sensors and two temperature sensors into the feed bore in the connecting rod, supplemented by a deformation measurement of the connecting rod small end and the measurement of the piston pin rotation by means of a GMR (Giant Magnetoresistance) sensor. In addition to an evaluation of the basic behavior at different speed and load points up to n = 1961 min⁻¹ and p_max = 220 bar, the sensitivity of the system on engine boundary conditions such as the gallery pressure level and the delivery volume of the piston cooling jet is analyzed. In addition, a hardware variant with a modified inlet groove geometry of the big end bearing shell is investigated. An accompanying FE (finite elements) analysis provides information on the deformation modes and the lubricant pressure distribution in the small end bearing. An accompanying 1-D flow simulation matched with measurement data enables the assessment of the oil transport behavior as well as the derivation of an optimal feed bore entry position. The measurement methodology with a GMR sensor proved to be a robust source of high quality data. The piston pin rotation showed a solely negative direction in relation to the crankshaft rotation. Key findings are the consistent pin rotation behavior corresponding to changes in the lubrication conditions, the possibility to improve lubrication supply by a modified big end inlet groove geometry and the significance of the positioning of the feed bore inlet as a high sensitivity of the transported oil mass is observed in the 1-D flow simulation.