The majority of transportation systems have continued to be powered by the internal combustion engine and fossil fuels. Heavy-duty applications especially are reliant on diesel engines for their high brake efficiency, power density, and robustness. Although engineering developments have advanced engines towards significantly fewer emissions and higher efficiency, the use of fossil-derived diesel as fuel sets a fundamental threshold in the achievable total net carbon reduction. Dimethyl ether can be produced from various renewable feedstocks and has a high chemical reactivity making it suitable for heavy-duty applications, namely compression ignition direct injection engines. Literature shows the successful use of DME fuels in diesel engines without significant hardware modifications. The lower energy density of DME calls for adjustments in injection parameters (such as injection pressure and duration) or modifications to the injector geometry to align with the energy levels found in diesel fuels. However, detailed direct comparisons between diesel and DME fuel injection characteristics over a wide testing range is lacking.
This study investigates the injection characteristics of DME and diesel fuels in a common rail fuel injection system using the Bosch tube method. It is demonstrated that this method can be effectively applied to measure DME fuel injection characteristics, albeit with some limitations in predicting injector closing delay. The research emphasizes the presence of hydraulic delay, resulting in a ratio of actual to commanded injection duration for DME between 1.5 to 2 under the testing conditions. The study finds that mass-based injection quantities for diesel and DME fuels are quite similar at matching conditions, although the lower heating value of DME results in lower energy-based injection quantities and thus fuel injection scheduling need to be adapted to compensate that. Furthermore, the paper offers valuable insights and suggestions for those considering the modification of diesel-operated engines into DME-operated engines.