Development and validation of a model for transient lubricant transport following start-up in a spray lubricated, motored marine diesel engine simulator

Abstract

This paper presents a model of the development of lubricating film thickness and film extent in a cross-head engine operated from start-up under motoring, along with experimental validation using an engine simulator. Theoretical predictions and experimental measurements of oil film thickness, and axial and radial ring gap filling under lubricant transport are presented with crank angle resolution on an instantaneous basis over several engine strokes following start-up. The experimental equipment and simulation model permit delivery of lubricant in a range of quantities (0.01 ml and 0.04 ml per injector are discussed here), delivery interval, supply distribution the timing of injection during the cycle can also be varied although they remained constant (injecting once per cycle at bottom dead-centre) for the work presented here. The novel, multi-stroke theoretical model simulates this process.
On system start-up, it was found that axial distribution of the lubricant under Couette flow occurred more quickly than circumferential distribution under Poiseuille flow. It was also shown that lubricant distribution occurs in a number of distinct steps which the authors have linked to physical stages of the filling process. The aim of the study was to gain a quantitative understanding of the lubricant distribution mechanism, with the long-term aim of supporting steps to minimise the lubricant delivery rates for large, two-stroke marine engines, and thus reduce operating costs and engine emissions due to the combustion of lubricating oil.