Cummins Power Generation employs multiple emissions technologies to increase performance and reliability of new EPA Tier 4 Final generator sets

Approach combines in-cylinder combustion improvements, exhaust gas recirculation (EGR) and optimized selective catalytic reduction (SCR) aftertreatment to meet EPA Tier 4 Final emissions goals without a diesel particulate filter (DPF).

MINNEAPOLIS – EPA Tier 4 Final emissions regulations go into effect in January 2014 for mobile generator sets with diesel engines rated from 174 to 751 horsepower. These engines will be required to emit no more than 0.4 grams of nitrogen oxides (NOx) and 0.02 grams of particulate matter (PM) in their exhaust, representing a 90 percent reduction in these two pollutants since Tier 3 regulations which were introduced in 2005.  Reaching these emissions goals has been a challenge for manufacturers, but Cummins Power Generation is one of the first to offer Tier 4 Final products in this power node, accomplished by optimizing a combination of emissions reduction techniques while increasing performance and reliability.

While all engine manufacturers will need to employ various forms of exhaust aftertreatment techniques, Cummins Power Generation decided early in the design phase to keep the aftertreatment technology as simple as possible.  Cummins Tier4 integrated solution meets Tier4 with an advanced engine which minimizes emissions in-cylinder and only a Selective Catalytic Reduction (SCR) and a compact Diesel Oxidation Catalyst as aftertreatment. While several manufacturers need to employ a more complex SCR and DPF package, Cummins meets Tier4 without having to use a DPF.

“The alternative to a DPF was eliminating PM formation in the engine cylinders during combustion.  By increasing fuel injection pressure, and other in-cylinder improvements, Cummins was able to significantly reduce the amount of PM produced in the first place,” said Eric Fay, technical project leader, Tier4 Final G-drive, Cummins Power Generation.  “As is characteristic of diesel engines, combustion conditions that favor a decrease in PM also favor an increase in NOx.  However, NOx is more easily controlled using a combination of cooled EGR and an SCR aftertreatment system.  Through years of experience with on-highway aftertreatment systems on its diesel engines, Cummins was well positioned to employ advanced SCR technology for power generation in order to meet EPA Tier 4 Final regulations.”

The multipronged approach Cummins Power Generation uses to meet Tier 4 Final emissions standards in its 174 to 751 horsepower diesel engines includes a variety of in-cylinder and aftertreatment techniques:

On-engine engineering changes and additions

• Fuel system – Increased pressure in the advanced high-pressure common rail fuel injection system helps reduce PM and improve fuel economy.
• Air handling –Variable geometry turbochargers provide optimal air flow at different speeds and loads for better combustion over the full range of power.
• EGR – Cooled exhaust gas recirculation is an effective way to reduce NOx in the combustion chamber without fuel efficiency penalties.
• Advanced engine controls – New electronic engine controls with faster microprocessors and more memory better manage operational parameters to control emissions over the full range of performance.  New software enhancements help manage DEF dosing in the SCR system.

Exhaust aftertreatment strategies

The Tier 4 Final aftertreatment architecture that Cummins employs in its integrated SCR system is based on three key subsystems:

• Diesel oxidation catalyst (DOC) – This system oxidizes remaining unburned hydrocarbons and carbon monoxide in the exhaust to carbon dioxide and water.
• DEF dosing system – This system meters the diesel exhaust fluid (DEF) from the DEF tank to the reactor tube in the exhaust. The consumption of DEF is approximately 4 percent that of diesel fuel. Sensors help limit DEF consumption to only the amount needed, reducing DEF costs.
• SCR – The heat of the exhaust causes the DEF to release ammonia, which neutralizes the NOx with the help of catalysts in the SCR. Sensors monitor any excess ammonia and make appropriate adjustments to DEF dosing.

The results of Cummins’ approach to meeting EPA Tier 4 Final standards are new certified engines that not only minimize emissions, but also offer better fuel efficiency with no decrease in reliability, power or performance.  The highly refined aftertreatment system is compact and configurable in a variety of ways to enhance engine packaging. Customers will benefit from the improved efficiency and low-maintenance aspects of the new Tier 4 Final engines, and the environment will benefit from reduced emissions.  Please visit the Web site: http://www.rental.tier4answers.com/

About Cummins Power Generation

Cummins Power Generation, a subsidiary of Cummins Inc. (NYSE: CMI), is a global leader dedicated to increasing the availability and reliability of electric power around the world. With more than 90 years of experience, the company’s global network of distributors in more than 190 countries delivers innovative solutions for any power need – commercial, industrial, recreational, emergency and residential.

Robert Sheldon, APR
Creative Communications Consultants, Inc.
(On behalf of Cummins Power Generation)
+1 210-828-1880
rsheldon@cccinc.com