An experimental study of the effect of condensing water vapour on the cold corrosion wear of marine engine cylinder liners

Abstract

This work presents an experimental study of the cold corrosion wear phenomenon that is experienced on the cylinder liners in large two-stroke marine diesel engines that burn heavy fuel oil containing sulfur. The wear is caused by condensing sulfuric acid-and water vapours (H 2 SO 4 and H 2 O, respectively) that are formed during combustion. In this work, cold corrosion is studied experimentally with a modified and motored light duty engine that operates at 98 revolutions per minute, in order to match the rotational speed of a large marine engine. The engine works as a tribotester where multiple charge gas compositions with up to 10% H 2 O and 80 ppm H 2 SO 4 (mole/mole) in dry air are fed to its cylinders to produce realistic marine engine H 2 O and H 2 SO 4 partial pressures. A lube oil blend that is composed by a conventional two-stroke marine engine cylinder lube oil and a base oil is used in the experiments. By extracting oil samples from the engine oil swamp during an experiment (that are analysed for iron and sulfur content using an energy dispersive X-ray fluorescence spectrometer) the cylinder liner wear rate and sulfuric acid condensation rate are determined for the applied charge gas composition and liner surface temperature (primarily 80 C). The method shows that the different charge gas compositions yield distinct liner wear rates and the highest wear rates are experienced at elevated H 2 O concentrations where the influence of H 2 SO 4 is comparably low.