Biofuel blend late post-injection effects on oil dilution and diesel oxidation catalyst performance

Abstract

In this article, the effects of different biofuel–diesel blends on engine oil dilution and diesel oxidation catalyst performance during late post-injections were investigated. The engine tests were made with an off-road diesel engine under low load conditions at 1200 r/min engine speed. During the experiments, oil samples were periodically taken from the engine oil and later analyzed. Emissions and temperatures before and after the diesel oxidation catalyst were also measured. The fuels studied were fossil EN590:2013 diesel fuel, 30 vol.% biodiesel (fatty acid methyl ester) and 30 vol.% hydrotreated vegetable oil, which is a paraffinic diesel fuel fulfilling the EN15940 specification. The novelty of the study is based on two parts. First, similar late post-injection tests were run with blends of both hydrotreated vegetable oil and fatty acid methyl ester, giving a rare comparison with the fuels. Second, oil dilution and the fuel exit rates during normal mode without the late post-injections were measured. The results showed the oil dilution and the diesel oxidation catalyst performance to be very similar with regular diesel and hydrotreated vegetable oil blend. With the fatty acid methyl ester blend, increased oil dilution, smaller temperature rise in the diesel oxidation catalyst and higher emissions were measured. This indicates that during diesel particulate filter regeneration by late post-injections, fatty acid methyl ester blends increase fuel consumption and require shorter oil change intervals, while hydrotreated vegetable oil blends require no parameter changes.