Cummins Inc. said its heavy-duty diesel engines that comply with the Environmental Protection Agency’s 2010 standards will not require NOx aftertreatment, although its medium-duty engines will use selective catalytic reduction (SCR) technology.
The decision to meet 2010 standards without SCR in heavy-duty engines stands in contrast with announcements from Detroit Diesel and Volvo/Mack that their 2010 truck engine solutions will employ SCR technology in order to bring NOx levels within EPA’s mandated maximum levels. SCR introduces urea into heated exhaust, causing it to break down into ammonia. The ammonia, in turn, reacts with the NOx in a catalytic converter to produce nitrogen and water.
At a news conference in Nashville on Sunday, Sept. 23, Steve Charlton, Cummins executive director of heavy-duty engineering, announced that the company’s heavy-duty engines instead would meet EPA demands through a combination of the XPI high-pressure common rail (HPCR) fuel system, improved cooled exhaust gas recirculation, advanced electronic controls, variable geometry turbochargers and the Cummins diesel particulate filter.
Cummins also said the 2010 engines in North America will include 11.9-liter and 16-liter diesel engines to complement its 15-liter product. All will share a common architecture that includes the XPI HPCR, said Ed Pence, vice president and general manager of Cummins’ heavy-duty engine business. “This is the first time in nearly 20 years that we’ve had common architecture across our heavy-duty products,” Pence said.
The HPCR fuel system, which was designed and built by a Cummins-Scania joint venture, offers improved performance and cleaner exhaust by maintaining high injection pressures regardless of engine speed, Cummins said. The company will continue to use the Cummins Turbo Technologies-designed VG turbo. And the Cummins Particulate Filter, designed and built by Cummins Emission Solutions and introduced in 2007, will be the only aftertreatment required for the 2010 solution.
Cummins’ approach toward lowering NOx for 2010 is to continue reducing the amount of oxygen introduced into the combustion process. Reducing the airflow not only reduces NOx, but it also produces other benefits, including high power density, minimum heat rejection and optimal fuel economy, Charlton said. And with less oxygen introduced into combustion, less oxygen comes out for use in cooled EGR, further improving performance and emissions control. “It’s a virtuous circle,” Charlton said.
In the heavy-duty segment, Cummins said it chose its solution with an eye to the key drivers of uptime, operational efficiency and low cost of ownership. By using its chosen approach rather than SCR to achieve NOx reduction, Cummins lowered the complexity and eliminated the need to purchase and manage urea, the company said.
