Development of a Direct-Injected Natural Gas Engine System for Heavy-Duty Vehicles: Final Report, Phase 1

The transportation sector accounts for approximately 65% of U.S. petroleum consumption. Consumption for light-duty vehicles has stabilized in the last 10-15 years; however, consumption in the heavy-duty sector has continued to increase. For various reasons, the United States must reduce its dependence on petroleum. One significant way is to substitute 'alternative fuels' (natural gas, propane,alcohols, and others) in place of petroleum fuels in heavy-duty applications. Most alternative fuels have the additional benefit of reduced exhaust emissions relative to petroleum fuels, thus providing a cleaner environment. The best long-term technology for heavy-duty alternative fuel engines is the 4-stroke cycle, direct injected (DI) engine using a single fuel. This DI, single fuel approachmaximizes the substitution of alternative fuel for diesel and retains the thermal efficiency and power density of the diesel engine. This report summarizes the results of the first year (Phase 1) of this contract. Phase 1 focused on developing a 4-stroke cycle, DI single fuel, alternative fuel technology that will duplicate or exceed diesel power density and thermal efficiency, while havingexhaust emissions equal to or less than the diesel. Although the work is currently on a 3500 Series DING engine, the work is viewed as 'basic technology' development that can be applied to any engine. Phase 1 concentrated on DING engine component durability, exhaust emissions, and fuel handling system durability. Task 1 focused on identifying primary areas (e.g., ignition assist and gas injectorsystems) for future durability testing. In Task 2, eight mode-cycle-averaged NOx emissions were reduced from 11.8 gm/hp-hr ('baseline' conditions) to 2.5 gm/hp-hr (modified conditions) on a 3501 DING engine. In Task 3, a state-of-the-art fuel handling system was identified