Research on Emissions and Engine Lube Oil Deterioration of Diesel Engines with BioFuels (RME) 2011-01-1302

In the diesel sector the fatty acid methyl esters (FAME's) - in Europe mostly RME (rapeseed methyl ester) and in US mostly SME (soja oil methyl ester) - are used as a various share, % volume blends with the diesel fuel (B5, B7, B10, B20, Bxx). The present joint project focuses on RME being the most important representative of the biofuels of 1st generation in Europe. The influences of RME blend fuels on emissions and on lube oil deterioration are emphasized.

Emissions were investigated on a modern engine with exhaust gas aftertreatment devices like SCR and (DPF+ SCR). Beside the legally limited exhaust emission components some non-legislated like NO₂, N₂O, NH₃ and nanoparticles were measured at stationary and dynamic engine operation.

The most important findings are: - the increased percentage of RME w/o aftertreatment causes an increase of NO_x by higher engine load and reduction of CO & HC; at transient operation (ETC) these tendencies are less pronounced and only B100 shows an increase of NO_x, - with SCR alone there are no differences of NO_x and of NO_x reduction rate (KNO_X) with increasing RME portion; there is lowering of CO & HC, - with DPF+SCR KNO_X-values are slightly higher, than with SCR alone, due to the production of NO₂ in the catalytic DPF (upstream of SCR), - there is excellent count filtration efficiency of DPF, up to 99.9%; with SCR alone there is usually a small reduction of nanoparticles concentrations (in the range of 10-20%, similar like a usual oxidation catalyst).

The paper describes as well significant problems related to the influences of biofuels on engine lube oils deterioration demonstrated by monitoring the engine lube oil aging during its operation in heavy-duty (HD) and modern high speed direct injection (HSDI) light-duty (LD) engine through the bench tests.

Subject to the long run durability engine tests were both: mineral and synthetic engine lube oils with different improved additives packages and viscosity ranges and with different RME-blending ratios in fuel.

The research methodology used: standard analysis as well as in-house-developed innovative methods, extensive analysis of engine lubricants oxidation stability - thin lubricant film oxidation tests and bulk lubricant oxidation tests.

It can be stated that: - the presence of bio-components in the fuel has significant impact on multidirectional hastening of engine lube oil destruction processes, - kind of base lube oil, lube oil additives components and RME-portion, as well as engine design and its operating conditions are very essential factors influencing the engine lube oil performance, - the processes taking place in an engine lubricant, influence adversely the limited possibilities of bio-components evaporation from engine lube oil and contribute to initiation of accelerated, deeper engine lube oil oxidation and degradation.