Design of a high-pressure fuel system for use with Dimethyl Ether

The paper documents the modeling and experimental work on a Common Rail fuel injection system for Dimethyl Ether, a potential Diesel substitute with a low Carbon Intensity signature. The DME fuel system is deployed on a light duty 2.2L compression ignition engine. The paper describes the injector optimization to shift to higher flows to account for the lower heating value and density of the DME when compared to Diesel. The type of the injection system used for the DME application is an advanced rendering of the Common Rail noted for a one-piece piston-needle injector construction, a solenoid driven spill valve featuring a pressure balanced poppet, and, a high-pressure fuel pump capable to effectively pressurize DME. The impact of these design features is a fast acting open and close injection event, reduced leakage, and, a low cavitation design. Design parameters studied include fill and spill orifices, needle lift, bias spring, and injector hole size. The model provides good correlation of the instantaneous rates of injection with experiments across a wide range of pressure and injection timings. Performance milestones include, foremost, a match of the DME injection duration to the Diesel counterpart for same fuel energy injected into the cylinder. Retaining near same duration contributes to keeping a very high engine cycle efficiency. The design provides reduced hydraulic delays of 50%. Tests demonstrate sustained operation at pressures of 1000 bar, with capability to reach 1500bar. Durability tests show no cavitation-deterioration over a 200 hr test cycle by means of spray imaging and hardware inspection.