Emissions reductions have posed many challenges for off-highway applications, particularly as solutions are launched for Tier 4 Interim deadlines and as development continues for Tier 4 Final designs.
The off-highway market, in particular, pushes the boundaries of constraints, driving significant demands on packaging and application-specific duty cycle effects. Additionally, customer requirements have become more complex—manufacturers require high-performance systems that don’t compromise the work cycle of the equipment, can be produced affordably, and don’t require major engine modifications.
Development costs for these applications must be controlled, requiring designs that are scalable and easily transferred from one application to another.
At Tenneco, we have aftertreatment strategies in place that are leading the industry in emissions control system development. We are a full-suite provider of integrated aftertreatment solutions that effectively withstand the extremes of duty cycles with varying engine speeds and loads and a variety of ambient conditions. Our solutions also meet performance criteria and provide R&D savings for the customer.
Tenneco’s complete solutions support its customers through Tier 4 Interim and beyond. Innovative technologies such as T.R.U.E.-Clean, ELIM-NOx®, SOLID SCRTM, and HC-LNC all support emissions reductions and, at the same time, offer unique cost and performance advantages.
Off-road vehicles are typically limited from utilizing underchassis aftertreatment designs due to unique concerns with ground clearance and flammability of underbrush.
While mounting the aftertreatment above the engine is normally a good solution in such cases, this introduces additional concerns such as the high investment for hood retooling and the subsequent impairment of operator visibility.
Tenneco has had excellent success with our compact T.R.U.E.-Clean DPF system in packaging the system in the space previously used by the vehicle silencer, with applications as diverse as forklifts, skid steers, utility tractors, and wheel loaders. With zero cost for hood retooling and zero adverse impairment of operator visibility, this represents a great solution for our customers.
Notably, the acoustic signature of the vehicle is often improved with this approach, thereby delivering incremental value.
Finding the best solutions at the lowest possible cost is critical in all segments of the market, given the highly competitive environment for the engines and machines.
There are several ways to help lower cost while providing such solutions. For example, our HC-LNC technology, under joint development with GE and Umicore, eliminates the use of precious group metals such as platinum and palladium by replacing the DOC with a thermal regeneration unit and Ag (Silver)-based catalyst.
Alternatively, modifying system architectures with alternative NOx reduction technologies such as Solid-SCR further reduces complexity and cost, including the elimination of heated liquid lines and connectors, coolant valves, and heat exchangers, by avoiding the need for freeze/thaw capability for DEF (AdBlue) systems.
Operating costs include fuel and reductant consumption, as well as equipment and operator use efficiencies. Fuel penalties will continue to be reduced with technologies that reduce system backpressure and provide more efficient, active DPF regeneration, such as Tenneco’s fuel vaporizer and hydrocarbon injector.
Improved reductant injection, coupled with improved mixer designs and improved uniformity across the SCR substrate, can significantly reduce reductant consumption. Maintenance costs, such as ash cleaning or catalyst replacement, also will be refined and controlled, thus reducing financial burdens for the vehicle owner. Finally, even on off-highway applications, component mass drives costs, and this will be scrutinized and reduced.
The bane of emissions performance for off-highway applications is lack of heat. Heat is necessary in an aftertreatment system to achieve DOC activation, provide for adequate passive or active DPF regeneration, and achieve satisfactory NOx conversion efficiency with SCR.
Many duty cycles simply fail to deliver adequate heat, especially for long periods after an overnight cold soak. Alternative solutions offering improved performance are continually being developed. Cost-effective technologies such as air gap pipe, electronic throttling valves, and improved hydrocarbon injection can provide solutions if reliable DOC activation can be achieved, but thermal activation and regeneration systems are often the only answer to assure performance without compromise, under any duty cycle, climate, or altitude conditions.
“Green” vehicles will continue to influence system designs, and the demand for biofuels will grow, requiring aftertreatment manufacturers to adjust their solutions. Tenneco’s hydrocarbon injection and vaporizer system are engineered for full compatibility with all ratios of biodiesel.
Emissions reductions will continue to influence engineering teams’ decisions, as the future has the potential to bring new particle number standards and greenhouse gas controls, while also emphasizing the benefits of retrofit solutions to clean up the past.
In this era of globalization, off-highway emissions standards will continue to spread to most regions of the world, even beyond the emerging BRIC (Brazil, Russia, India, and China) economies.
But the standards must meet the needs of the market they serve.
Fuel sulfur levels and reductant infrastructure are both key concerns as developing countries implement these new regulations to ever tightening timelines. HC-LNC technology is a possible solution, with highly demonstrated sulfur-resistant, full sulphation recovery using periodic regeneration cycles and no need for a secondary reductant for NOx conversion levels up to 60%.
All of these considerations require thorough system integration.
Tenneco has adopted a strategy of providing “one-stop” shopping for our customers with mechanical aftertreatment, injection systems, thermal management devices, reductant tanks, electronic control units, software, sensors, and onboard diagnostics, all available as a single module.
Our technology roadmap prescribes the advanced engineering and development at Tenneco, as the company aligns its advanced engineering efforts with its customers’ global demands.
We view all of the challenges outlined as opportunities for our industry and, more specifically, for our company. Tenneco will continue to lead the drive to reduce vehicle emissions through its aftertreatment solutions aimed at helping manufacturers improve fuel economy, reduce CO2 emissions, enhance equipment performance, and meet requirements for Tier 4 Interim, Tier 4 Final, and beyond.
Tim Jackson, Chief Technology Officer, Tenneco, wrote this article for SAE Off-Highway Engineering.