Natural Gas Dedicated Exhaust Gas Recirculation Engine for Improved On-Highway Efficiency

A Cummins Westport ISX12 G heavy-duty natural gas engine was modified to use dedicated exhaust gas recirculation (Dedicated EGR®), an innovative configuration where specific cylinders directly feed their exhaust to the intake of the engine. This configuration enables higher levels of EGR dilution with reduced pumping work when compared to traditional high-pressure EGR systems typically seen on heavy-duty engines. This system was used in combination with an advanced continuous discharge ignition system, a variable geometry turbocharger, and a low-squish, high compression ratio piston. The combined hardware modifications enabled a 12 percent improvement in engine fuel economy while maintaining oxides of nitrogen (NOX) emissions at levels 90 percent below the current 2010 heavy-duty NOX standard. Heavy-duty natural gas vehicles using high efficiency Dedicated EGR engines can displace diesel vehicles and help California meet its greenhouse gas emission reduction goals, while simultaneously addressing air quality improvement needs of regions such as the South Coast Air Basin.