Dimethyl ether (DME) is an alternative fuel that, blended with propane, could be
an excellent alternative for exploring the use of fuels from renewable sources.
DME–propane blends are feasible for their comparable physicochemical properties;
these fuels may be pressured as liquids using moderate pressure at ambient
temperature. Adding a proportion of DME with a low octane number to a less
reactive fuel like propane can improve the combustion process. However, the
increased reactivity of the mixture induced by the DME could lead to the early
appearance of knocking, and this tendency may even be pronounced in boosted SI
engines. Hence, this study experimentally analyzes the effect of E10 gasoline
(baseline) and DME–propane blends, with varying proportions of DME in propane
ranging from 0% to 30% by weight, in increments of 5% on knocking tendency,
combustion characteristics, gaseous emissions, and particle number
concentration, under different intake pressure conditions (0.8, 0.9, 1.0, and
1.1 bar) in an SI engine. The results show that as the proportion of DME in the
propane blend rises, the knocking tendency becomes more pronounced. That
behavior intensifies with increasing intake pressure, but with 20% DME in the
propane blend, reaching the maximum brake torque (MBT) without knocking in the
four boosted conditions is feasible. The presence of knock limited the advance
of combustion phasing and decreased the gross indicated thermal efficiency
(ITEg) with E10 gasoline and 25% and 30% DME in propane blends under 1.0 and 1.1
bar boosted conditions. In these knock-limited circumstances, the NOx emissions
decreased due to the retarded phasing, and THC and PN emissions increased due to
the lower combustion stability, considerably raising the concentration of
accumulation mode particles in the particle size distribution (PSD) compared to
the other fuel blends tested.
