Evaluation of Medium Duty DME Truck Performance -Field Test Results and PM Characteristics-

The performance of a medium duty DME truck was evaluated by field tests and engine bench tests. The DME vehicle was given a public license plate on October 2004, after which running tests were continued on public roads and a test course. The DME vehicle could run the whole distance, about 500 km, without refueling. The average diesel equivalent fuel consumption of the fully loaded DME truck was 5.75 km/l, running at 80 km/h on public highways. Remedying several malfunctions that occurred in the power-train subsystems enhanced the vehicle performance and operation. The DME vehicle accumulated 13,000 km as of August, 2006 with no observed durability trouble of the fuel injection pump. Disassembly and inspection of the fuel injectors after 7,700 km operation revealed a few differences in the nozzle tip and the needle compared to diesel fuel operation. However, the injectors were used again after cleanup. Regarding particulate matter (PM) emissions characteristics, a PM size distribution characteristic of the nuclei mode was observed with diesel fuel operation. The peak PM size increased and the distribution moved to smaller sizes with higher engine load. Nanoparticle concentration were greatly decreased with an oxidation catalyst. The peak PM size increased with EGR but there was no significant effect of the EGR ratio on PM size distributions.