Future engine emissions reduction strategies

  • 05-May-2017 09:14 EDT
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Joel Johnson is Global Vice President, Mobile Machinery at Freudenberg-NOK Sealing Technologies.

Demands on off-highway vehicles and trucks today are exceedingly complex. Equipment must be more environmentally friendly, work in a more aggressive environment, run longer hours and rely upon the latest material and product technology to meet market demands for peak performance. To satisfy future global emissions-reduction demands, a wider application of existing technologies and the development of innovative yet cost-effective technologies is required. As a leading manufacturer of seals, accumulators and high-performance materials, Freudenberg Sealing Technologies is dedicated to addressing the existing and future system requirements of customers throughout the world.

Discussions regarding regulations often center around measuring emissions but, in general, improving efficiency is a direct input to improving emissions. Actions such as downsizing, direct injection, exhaust gas recirculation, friction reduction and selective catalytic reduction all affect engine efficiency and thus emissions.

Systems optimization

Advanced sealing solutions play a critical role in systems optimization and extending the overall life of the machine. For example, seals are responsible for nearly one-quarter of all lost mechanical energy in today’s automatic transmissions, so transmission manufacturers are keen to lower system friction to minimize this loss. New seal designs and materials available today can help lower system weight, reduce friction and lower fuel consumption.

In engines, we are challenged to support lightweight designs, accommodate extended temperature ranges and address challenges posed by advanced fuels, lubricants and aggressive media. Freudenberg works in close cooperation with customers to develop solutions that resolve these challenges, while also optimizing the efficiency and emissions performance of various powertrain systems. The company has developed seals that withstand more than 18,000 hours of hard operation with plans to double this.

In developing optimal sealing systems, it is essential to identify application conditions. In some cases, our customers have extreme requirements, perhaps relating to contaminant exclusion or temperature specifications. Seals are part of a tribological system and can’t function properly when all performance parameters are not carefully analyzed. In many cases, multiple sealing solutions can be considered, but the optimal solution becomes evident only through extensive analysis of factors like speed, temperature, application, media, pressure and size (S.T.A.M.P.S.)

Our company’s efforts have coalesced in the development of its Low Emission Sealing Solutions (LESS) portfolio of products. LESS components have been engineered and field-tested to address S.T.A.M.P.S. parameters that influence energy consumption, efficiency and emission challenges in mobile machinery and trucks. These products incorporate: valve stem modifications for diesel engines that facilitate oil metering and blow-by control; next generation crankshaft sealing technology that reduce friction up to 90%; material and process technologies that improve transmission efficiency through seals that use oil flow and oil pressure to minimize power loss; improved gaskets that accommodate the increased tolerance range of plastic covers; gaskets compatible with exhaust gas and urea additives; and AdBlue-resistant materials for high temperatures.

Electrification and other global trends

In addition to powertrain system optimization, other global trends also are driving future engine emission strategies. For the most part, all new equipment in Europe and in the United States conforms to Stage IV emission standards. A pressing question is where and to what degree will other regions follow suit? In China, for example, where air pollution is a major issue, we will likely see emission standards that converge with Stage IV limits. But what about in other markets like India and Iran? Global manufacturers must be able to incorporate new technologies that help meet stricter limits, while balancing a “total cost of ownership” approach that extends the life of existing equipment.

There’s also a trend toward electrification, but it varies by market. In material handling equipment, electrification certainly lends itself to industrial trucks. They are often operated in enclosed spaces and need additional weight so they don’t tip over. The battery supplies the counter weight and some customers are working to replace the battery with a fuel-cell assembly to eliminate the recharging station. This is the ultimate in emissions reduction. The view of the situation is different for each market though. Agricultural machines are often operated over long periods at a constant speed, far from any infrastructure. In this application, an efficient diesel engine is generally seen as the best choice because it can provide more of a 24/7 type performance only stopping for refueling.

For smaller construction machines used in an urban environment, a diesel-electric hybrid powertrain definitely makes sense. The diesel engine would run solely as a generator at a constant rotational speed, which reduces the noise level considerably, but the work is initiated via an electrical system. In some applications, such as a classic excavator, substitution of the hydraulic system with an electrical system is not practical, so hydraulic assist storage systems may make more sense. In these cases, the pressure generated by the hydraulic system is stored in an accumulator rather than being released back into the oil reservoir. This energy is then used to initiate the next machine movement rather than starting from scratch. If the phases with lower loads use the energy stored in the accumulator, the overall energy balance is improved.

During the past 10 years, the efficiency of engine and transmission sealing packages has been improved by nearly 50%. By applying and refining technologies available today, an absolute improvement of efficiency of the same magnitude can be achieved. By optimizing current designs with existing technology, customers are able to cost-effectively move the needle in emissions reduction.

Joel Johnson, Global Vice President, Mobile Machinery at Freudenberg-NOK Sealing Technologies, wrote this article for Truck & Off-Highway Engineering as part of our annual Executive Viewpoints series.

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