Impact of increased injector nozzle hole diameters on engine performance,exhaust particle distribution and methane and formaldehyde emissions during dimethyl ether operation

Abstract

E-Fuels can play a significant role in decarbonizing the transport sector. Among the potential E-fuels, dimethyl ether is a promising candidate for the combustion in compression ignition engines. Together with methanol, it can be produced from synthesis gas in a combined single-step process. However, due to the low volumetric heating value of dimethyl ether, the fuel injection system has to be modified to realize higher fuel flow rates. In this study, two injectors with increased nozzle hole diameters have been investigated, and their impact on engine performance, particle number distribution and formaldehyde as well as methane emissions was assessed. It was found that with dimethyl ether as fuel, the indicated efficiency at high load could be increased by over 1% compared to operation with conventional diesel fuel. The main reason for this is lower wall heat loss. Furthermore, almost no particle emission was found during dimethyl ether operation with the smaller nozzle. With the larger nozzle hole diameter, increased particle concentrations were measured at high loads. But these were still much lower compared to the corresponding diesel fuel combustion. Regarding formaldehyde and methane, higher emissions were found for the dimethyl ether combustion compared to diesel fuel combustion. It is assumed that this is due to the increased formaldehyde and methane production of dimethyl ether during high temperature pyrolysis and oxidation. The increased hydrocarbon emissions could have been caused by fuel dripping from the nozzle after the end of the injection event.