Cummins takes QSK to Tier 4 Final

The engine will use integrated SCR aftertreatment, replacing the muffler with drop-in simplicity.

Cummins' high horsepower SCR system
Cummins' high horsepower SCR system
Cumminslo 10108212

Cummins Inc. announces that the QSK high-horsepower engine range will move forward to meet EPA Tier 4 Final off-highway 2015 emissions with a combination of clean in- cylinder combustion and a new Selective Catalytic Reduction (SCR) clean exhaust system.

For most applications, the Tier 4 Final QSK engine and integrated SCR aftertreatment offer the installation simplicity of a drop-in replacement for the current QSK engine and exhaust muffler, with a similar size and equivalent noise reduction. While achieving very low emissions levels, Cummins Tier 4 Final technology also reduces the overall cost of operation, with QSK fuel efficiency improved by 5% to 10%, depending on the equipment duty cycle.

The new SCR clean exhaust system will be utilized on the next generation of 19-liter to 60-liter QSK engines across a broad 800 hp to 3,000 hp (597-2,237 kW) power range. The Tier 4 Final engines retain the exceptional power output and in-service dependability of the current QSK engines, proven in the most demanding high-horsepower applications. The SCR clean exhaust system will be scaled-up for QSK engines above 3,000 hp, including the new larger-displacement engine platform, with details due to be released in September.

Cummins Tier 4 Final technology brings common emissions architecture to a diverse range of high-horsepower applications, including mining, locomotives, marine vessels, oil and gas equipment, power generation, large cranes and other industrial equipment.

"Our next-generation QSK engines, integrated with the new SCR clean exhaust system, represent a game-changing technology that leaps ahead to achieve Tier 4 Final with the benefit of installation simplicity and improved fuel efficiency," says Mark Levett, Cummins Vice-President and General Manager - High-Horsepower Business.

"No other engine company has the depth of experience with SCR technology as Cummins, dating back to 2006 in Europe and now with almost 100,000 EPA 2010 on-highway engines operating with SCR in North America. Our ability to leverage this preceding SCR experience and optimize for high-horsepower applications with the new SCR clean exhaust system enables Cummins to deliver the right emissions solution for Tier 4 Final," Levett said.

"Our SCR technology has demonstrated outstanding durability in-service, equal to that of the engine platform. Using SCR aftertreatment for high-horsepower applications means we are able to avoid any major change to the engine platform and retain the dependability and power performance of our current QSK engines - and this continuity is of key importance to our customers.

"I am certain that these considerable advantages will continue Cummins clean-power leadership in the North American high-horsepower markets," adds Levett.

The Tier 4 Final clean technology builds on the proven success of the current QSK engine range. Cummins is the clean-power leader, with more Tier 2-compliant high-horsepower engines in-service than any other engine manufacturer.

Cummins SCR clean exhaust system reduces oxides of nitrogen (NOx) emissions to 3.5 g/kW-hr for Tier 4 Final off-highway, representing a more than 40 percent reduction compared with the Tier 2 level.

By focusing NOx reduction within the exhaust rather than during in-cylinder combustion, Cummins avoids the need to make any major change to the external engine platform. Using SCR also leaves a much higher performance threshold in-cylinder in order to focus on Particulate Matter (PM) reduction and improve fuel-efficiency.

PM emissions are reduced by 80 percent to meet the 0.04 g/kW-hr level for Tier 4 Final. This is achieved by a clean-combustion formula utilizing higher-pressure fuel injection and enhancements to the power cylinder design. This inherent capability to achieve higher fuel injection pressure is a key feature carried forward from the fuel system on today's QSK engines. Highly efficient PM reduction in-cylinder eliminates the need for either a diesel oxidation catalyst or diesel particulate filter aftertreatment in the exhaust stream.

Higher Fuel Efficiency
The fuel savings achieved by Cummins Tier 4 Final QSK engines more than offsets the cost of Diesel Exhaust Fluid (DEF) dosing required for the functioning of the SCR clean exhaust system. Depending on duty cycle and application, Cummins clean combustion for Tier 4 Final enables fuel-efficiency to be improved by 5% to 10% compared with Tier 2 engines, with DEF consumption to fuel held as low as 2% to 3%.

For many applications, this results in a major reduction in overall operating costs, taking into account the cost of both diesel fuel and DEF. With the cost of bulk DEF lower than that of diesel fuel and anticipated to fall further as the off-highway market supply expands over the next few years, this brings an added cost advantage to using SCR aftertreatment.

Low DEF consumption is achieved by a series of advanced sensors monitoring the operation of the Cummins SCR clean exhaust system to match DEF dosing levels to engine load and duty cycle. Lower dosing also means that the on-board DEF tank is easily sized to meet fuel tank capacity, or can be increased in size for extended refilling intervals to match specific equipment operation.

SCR Clean Exhaust System
The new SCR clean exhaust system is a highly robust, fully integrated aftertreatment package specifically developed by Cummins Emission Solutions for high-horsepower applications. The SCR aftertreatment operates as a fully passive, flow-through system and is capable of high NOx conversion with low backpressure, enabling enhanced fuel economy.

Cummins SCR clean exhaust system utilizes an innovative DEF decomposition process to significantly reduce space claim and benefit overall equipment integration while ensuring that low NOx emissions levels are achieved. The SCR system also features an integral DEF dosing injector with a high-efficiency spray pattern.

SCR logic control is driven by the QSK electronic engine management system, upgraded with extra processing power for Tier 4 Final so that the engine and SCR aftertreatment operate as a single, integrated system.

The SCR modular configuration is scalable for the complete QSK engine line-up to ease integration and assembly by the equipment manufacturer. For applications below 1500 hp (1119 kW), an SCR single-catalyst system is used in varying lengths sized to engine output. An SCR twin-catalyst system is used for applications above 1500 hp, with each catalyst aligned with a cylinder bank and matched to engine power output. For most applications, the SCR system replaces the current muffler within an equivalent size envelope and provides similar sound suppression.

DEF is a product certified by the American Petroleum Institute (API), consisting of an aqueous solution of 32.5% high-purity urea and 67.5% deionized water, and requires no special handling. Today, Cummins Filtration supplies Air Shield(TM) DEF to the Cummins distribution network to support on-highway truck operators using EPA 2010-compliant engines.

Cummins and other DEF suppliers will have a nationwide service readily available for off-highway equipment users when required for the Tier 4 Final introduction. A wide range of DEF packaging size options are available, extending up to 330-gallon reusable totes and bulk delivery. Cummins can help equipment operators calculate DEF usage and plan the most cost-effective choice in order to lower cost of operation.

Robust System Architecture
Cummins design starting point for Tier 4 Final has been to meet very low emissions standards with the most robust and reliable system architecture, capable of performing in the toughest high horsepower applications. Jim Trueblood, Vice-President - Cummins High-Horsepower Engineering, explains how this has been achieved:

"No equipment works harder or under more severe conditions than large mining excavators and frac rigs used in oil and gas applications. As Cummins powers by far the highest number of these extreme-duty machines, we used their duty cycles as our Tier 4 Final baseline for durability and in-service dependability.

"As a result, our combination of QSK engine and SCR clean exhaust system is capable of working at the highest engine loads of over 80 percent for exceptionally high hours. As most high-horsepower applications operate well below these severe-duty cycles, this means that our Tier 4 Final base engine design is inherently stronger than any other.

"Our customers can be confident that they will realize the same dependability with our Tier 4 Final architecture as they have experienced with Cummins high-horsepower engines over many years, regularly achieving over 95% uptime," adds Trueblood.

The SCR clean exhaust system offers durability equivalent to that of the QSK engine, with a very robust catalyst and strengthened packaging intended for the harshest off-highway equipment operating conditions. The system features enhanced protection against vibration and shock loadings.

Before taking an SCR aftertreatment path, Cummins evaluated alternative Tier 4 Final technologies such as Exhaust Gas Recirculation (EGR) and Variable Valve Actuation. However, both of those approaches were considered less effective for large high-horsepower platforms, as they require major re-engineering of the base engine, generate additional heat rejection for the equipment cooling system to manage, and compromise serviceability. Cummins SCR aftertreatment offers a simpler and, therefore, more robust solution to achieve NOx emissions reduction.

As a further advantage for operators, there are no additional service requirements for the QSK Tier 4 Final engine compared with the Tier 2 engine. With only minimal external changes to the engine, this means that ease of serviceability remains the same.

Cummins SCR Experience
Cummins has a unique advantage in that all the key enabling Tier 4 Final technologies are designed, manufactured and integrated as a single system by Cummins.

The SCR clean exhaust system integrated with the Tier 4 Final QSK engines is designed and manufactured by Cummins Emission Solutions, one of the world's largest suppliers of exhaust aftertreatment, with 350,000 SCR systems produced.

Cummins experience with SCR technology is unrivalled in the industry, dating back to 2006 with Euro 4 on-highway emissions. In North America, nearly 100,000 EPA 2010 on-highway engines with SCR are in-service, meeting emissions levels more stringent than those of Tier 4 Final. Commencing in 2014, SCR technology will also be utilized for Cummins off-highway engines from 75 hp to 751 hp (56-560 kW).

This in-house capability is unique in the industry and ensures the highest level of system integration between engine and aftertreatment.

"We have been able to develop an innovative SCR packaging configuration with modular flexibility to replace the exhaust muffler within virtually the same space envelope - a first in the aftertreatment industry for high-horsepower applications," says Julie Furber, General Manager - Off-Highway Business Cummins Emission Solutions.

The first Cummins Tier 4 Final QSK engines with the integrated SCR clean exhaust will begin production in 2014, ahead of the Jan. 1, 2015, emissions effective date for engines above 751 hp (560 kW). With the emissions technology performance now validated, the Cummins Tier 4 Final program will now focus on machine integration and field test optimization, working closely with equipment manufacturers.

Concurrent with the Tier 4 Final production, Cummins will maintain full production of all current QSK and K Series high-horsepower engines for worldwide applications requiring less stringent emissions levels.