Effects of the addition of oxygenated fuels as additives on combustion characteristics and particle number and size distribution emissions of a TDI diesel engine

• When the proportion of oxygen in the additive mixture increases, decreases the emission of total number of particles.
• A tendency to increase the SFC with the increase in proportion of additive is not observed.
• In comparison with CD, only DGM10 and DGM15 blends produced an increase in the brake thermal efficiency.
• This particle emission is particularly low in the case of the ETBE15 blend.

The aim of the study is to evaluate the influence of the use of oxygenates as additives to diesel fuel on the combustion process, the specific fuel consumption, effective efficiency and emissions, especially particle emissions in the range 5.6–560 nm in size distribution and number of a diesel engine. The oxygenate compounds used were EtilTerbutilEter (ETBE) and Diglyme which were added to Commercial Diesel (7% FAME). Engine bench tests were performed with 7 additive/CD blends in different proportions, 5%, 10% and 15% of oxygenated additive added to the base Commercial Diesel fuel. The tests were performed on a 2.0 TDI diesel engine VW Euro 4, in 9 stationary operating conditions (1500, 2250 and 3000 min−1 to 15%, 30%, 45% load). Experimental results show that the mixing ratio additive/diesel is the parameter that has the greatest influence on the particle emission. NOx emission compared to CD increases or remains constant depending on the amount of additive in the mixture, engine speed and load condition. Furthermore, there is a dramatic decrease in the total particle concentration with the addition of oxygenated additives, especially when the ratio reaches 15%. The geometric mean diameter (GMD) of the particles of the blends, presents consistent trends with load and speed variation. Blends with 15% additive at all engine operating conditions are maintained in smaller sizes than the CD. The GMD does not show a clear dependence on the type of additive used, however the proportion of additive has significant influence on GMD. A higher proportion of additive, lower GMD.