Fuel Rule to Spur Tweaks in Cummins’ SCR Engines

Engine manufacturer Cummins Inc. will use incremental improvements to its current selective catalytic reduction engines to meet new federal standards for limiting greenhouse gas emissions between now and 2017, a senior company engineer said.

The Columbus, Ind., manufacturer also said that onboard diagnostic sensors mandated by earlier anti-pollution regulations on nitrogen oxides and particulate matter might also be used to control carbon dioxide output, said Stephen Charlton, chief technical officer of the corporation’s engine business.

“SCR is the cornerstone of what we’re doing. We took a big step with it three years ago, but it’s not static. Think of the 2010 engines as the first generation of SCR; 2014 as the second generation; and 2017 will be the third generation,” Charlton told Transport Topics.

The Obama administration formally unveiled its two-step greenhouse gas rule on Aug. 9, calling for 20% reductions by 2017 in diesel fuel burned and greenhouse gas emitted (8-15, p. 1). The following week, executives from manufacturers Daimler Trucks North America, Navistar International Corp. and Volvo Group began discussing their plans for design and engineering changes in 2014 and 2017 (8-22, p. 5).

Although Cummins does not make trucks, it is the largest North American producer of heavy-duty diesel engines, controlling 34.1% of engine sales in the first half of this year (8-22, p. 1).

Charlton said Cummins management is so confident in meeting the first phase of the rule that the company anticipates making the technology available in January 2013, a year before it is due. As for the second phase, Charlton said research is being done now.

While truck makers may pursue aerodynamic body designs, Charlton said, Cummins will look at friction reduction, greater efficiency in combustion, air handling and waste-heat recovery. He described the engine’s variable-geometry turbocharger as being particularly important.

“The VGT is our Swiss Army knife. There are quite a number of systems it has to control very accurately,” said Charlton, adding that the component has effects on SCR, braking and exhaust gas recirculation.

Another potential for increasing energy efficiency that is not intuitively obvious is less viscous engine oil. The more viscous the lubricating oil in a bearing, the more energy it takes to turn an axle, Charlton said. Therefore, maintaining the level of metal protection, but with a less viscous oil, yields an incremental improvement in efficiency.

“We’re looking into every corner for savings,” Charlton said.

On the notion of waste heat, which has also been raised by the truck makers, Charlton said a typical heavy-duty diesel engine throws off heat at around 850 degrees Fahrenheit. Capturing it and using it could improve efficiency by 5% to 8%, he said.

The process is simply stated as capturing the heat, using it to boil water or a refrigerant and using the steam to power a turbine. The challenge is to do that efficiently within a fairly small space.

Charlton said the turbo could power an onboard electrical generator or even be used for propulsion.

“We’re talking about quite a number of kilowatts, maybe 20,000 to 40,000 kilowatts, that could go back into the crankshaft, but both options are in play,” he said.

Charlton said onboard diagnostics sensors for NOx and PM also could help monitor greenhouse gases.

“There are some synergies here, although it’s not a 100% overlap,” he said. The sensors should allow for better control of the aftertreatment process for NOx, and that also should increase overall engine efficiency, he said.

Two things that will not change greatly, Charlton said, are engine weight and the company’s James-town, N.Y., engine plant, where Cummins makes heavy-duty ISX engines.

“For 2014, there won’t be a significant change in weight from 2010. It’s too soon to tell precisely for 2017, but there could also be offsetting benefits. Right now, the best guess is that weight will be pretty close,” he said.

Charlton also said changes at Jamestown would be minimal because even the 2017 power plants would have the “same basic engine architecture. We will see incremental improvements to subsystems.”