Combustion characteristics of oxymethylene dimethyl ether-diesel blends: An experimental investigation using a constant-volume combustion chamber

Abstract

The combustion characteristics of oxymethylene dimethyl ether (OMEx) and its blends with diesel have been investigated using a multi-hole injector in a constant-volume combustion chamber. The results show OMEx addition can reduce the ignition delay, especially when blends of more than 50 vol% are used, at low chamber temperature. Two individual heat-release peaks are observed for OMEx during premixed combustion at 750 K, due to a pronounced low-temperature heat-release phase. The chamber temperature of 800 K can be regarded as a transition point for the behavior of burn duration as well as maximum ROHR peak, mostly caused by combustion regime transition from premixed- to diffusion combustion. It appears that there is an approximate linear relation between maximum ROHR peak and the time at which this peak occurs with injection pressure. The ignition delay of OMEx is almost insensitive to a decrease in ambient oxygen concentration. And the premixed ROHR profile, due to its high oxygen content, is very similar and only ignition delay and burn duration increase slightly. Additionally, comparisons of natural luminosity results for OMEx and diesel indicate that OMEx produces near-zero soot values. Luminosity is expected to be caused by chemiluminescence alone, which increases with injection pressure.