Having trouble trying to meet EPA emissions standards? Southwest Research Institute of San Antonio, as part of the U.S. Department of Energy’s Next Generation Natural Gas Vehicle Program, has developed a new low-emissions, heavy-duty natural-gas engine that more than meets stringent EPA emissions standards. The next-generation engine (Circle 927) emits greatly reduced levels of oxides of nitrogen (NOx) and particulate matter (PM), allowing production of heavy-duty trucks that restrict the release of pollutants into the atmosphere.
Natural gas engines operate on a gaseous fuel and are typically spark ignited, which emits lower PM. However, the engines are normally adjusted to run with a lean air-fuel ratio, which prevents using a simple catalytic after-treatment device to reduce NOx emissions. Other changes to the engine included adding a cooled exhaust gas recirculation (EGR) system modifying an engine controller with algorithms to control the EGR-improved engine efficiency, lowered temperatures, reduced engine-out NOx emissions and decreased tendency to knock.