Investigation of Dimethyl Ether Injection Characteristics in High-Pressure Direct Injection Systems

The majority of transportation systems continue to rely on internal combustion engines powered by fossil fuels. Heavy-duty applications, in particular, depend on diesel engines due to their high brake efficiency, power density, and robustness. Despite significant advancements in diesel engine technology that have reduced emissions and improved efficiency, complex and costly after-treatment systems remain necessary to meet the stringent emission regulations. Dimethyl ether (DME), which can be produced from various renewable feedstocks and possesses high chemical reactivity, is a promising alternative for heavy-duty applications, particularly in compression ignition direct injection engines. Its high reactivity, volatility, and oxygenated composition offer significant potential to address emission challenges while reducing reliance on after-treatment systems. However, DME’s lower energy density requires adjustments in injection parameters (such as injection pressure and duration) or modifications to the injector geometry to match the energy levels of diesel fuels. Although previous studies have explored adjustments like increasing injection pressure and duration to compensate for DME’s lower energy density, the impact of nozzle diameter on the rate of injection profile and spray morphology remains unclear. This study investigates the injection characteristics of DME in a high-pressure direct injection system. The rate of injection profile is measured using a custom-designed long tube platform based on the Bosch principle. The results from the long tube platform show strong consistency with those obtained from a commercial injection test bench, albeit a slight reduction in the rising slope during the injector opening phase is observed with the Bosch method. Additionally, the rate of injection profiles for two different nozzle diameters are measured to assess the impact of nozzle size on the rate of injection profiles. The effects of increased nozzle diameter on spray morphology are also analyzed using high-speed photography.