This article also appears in
Subscribe now »

Bernd Krüper (left), head of the Construction & Agriculture business, and Frank Dräse, program manager for EU Stage V at MTU. (Images by Robert Hack, MTU)

Greener, meaner, leaner drive systems for off-highway

Expected to come into force in 2019 for mobile machinery and equipment in Europe, the future European Union Stage V off-highway emissions standard harbors new challenges for the entire industry. The new regulations stipulate a further reduction in nitrogen oxide and particulate emissions throughout the entire operating range. For the first time, there is also a maximum permissible limit for particulate, making the exhaust aftertreatment system more complex.

Particularly in the case of construction vehicles and machinery, where only limited installation space is available, the system's flexibility and compactness play a decisive role. Leading engine manufacturers such as MTU Friedrichshafen have already presented their drive system solutions to meet the future EU Stage V emissions directive. Bernd Krüper, head of the Construction & Agriculture business, and Frank Dräse, program manager for EU Stage V at MTU, talk about the world’s strictest emissions directive and the solutions being developed by MTU for the power range from 100 to 480 kW (134 to 643 hp).

How is MTU preparing for the future EU Stage V emissions standard?

Krüper: Complying with the new emissions directive requires more than just expertise in engines. Our ambition is to optimize the entire powertrain and exhaust treatment system and supply our customers with a system tailored to their requirements. The product shall at the same time reduce the installation and adaptation work for our OEM clients, that is equipment manufacturers, reliably meet the emission legislation requirements and efficiently deliver the best possible performance in the field. Together with our partners we are currently further developing our proven Series 1000 to 1500 engines for EU Stage V, which will simplify integration of the future engine systems for our existing clients.

What is the biggest technological challenge for MTU in that process?

Dräse: The biggest difference between the present EU Stage IV emissions legislation and the impending Stage V is the fact that in future not only the mass of the soot particulates emitted by the engine is limited but also the number of particles. Limiting the number of particles is only possible by means of sealed particle filters. Therefore, to comply with Stage V we have to fit a diesel particulate filter, or DPF for short, to our Series 1000 to 1500 engines for the first time. With the help of sophisticated technology, we have so far been able to meet the requirements by means of internal engine refinements and an SCR (selective catalytic reduction) system. But despite the addition of a DPF, we are aiming to produce a solution that requires approximately the same space as the one for EU Stage IV/EPA Tier 4 final. For the Series 1100, 1300 and 1500 we will offer a 1-box solution with integrated exhaust treatment system. It consists of a diesel oxidation catalytic converter, DPF and an SCR system. For the Series 1000, as well as the 1-box solution there will most probably be a 2-box solution for even greater flexibility in terms of installation.

Motorists have been familiar with DPFs on their cars for some years now. What is special about the DPFs for MTU’s engines?

Krüper: It is true that DPFs have been in use for some years, including on cars and commercial vehicles. That means that we benefit in terms of our development work and the end product from basic designs that have been tried and tested thousands of times over, and we also build on the extensive experience of our development partner Daimler and its suppliers. That has a positive effect in terms not only of the advanced and sophisticated technology but also of the attractive volume-production prices for our customers. That said, as our engines are used in tough and extremely varied off-highway conditions, they are sometimes subjected to different stresses and required to meet quite different load profiles. In terms of harmonizing the overall engine system and adapting the regeneration strategies, that means a lot of work for us, which is a challenge we welcome with the comprehensive expertise at MTU and Daimler.

Regeneration strategies—what does that mean in practice?

Dräse: Every DPF functions like a sieve that traps the unburned carbon soot particles. If that filter were to become clogged with soot, the exhaust backpressure would rise considerably. The result would be higher consumption and loss of engine power. Therefore, the trapped particles in the filter have to be burned off at regular intervals. That process, which takes place at a high temperature, is called regeneration. For us, the challenge is integrating that process in the duty profile of off-highway engines. We are already pursuing some promising ideas for that.

Krüper: Agricultural and construction machines are often used differently from commercial vehicles. Lorries travel long distances at a relatively constant load, such as on motorways at a relatively even speed, so that regeneration is not usually a problem. Our exhaust treatment system has to function equally well in such diverse applications as mobile cranes and forage harvesters with entirely different load profiles. In such applications, high-load phases—such as when lifting loads or when harvesting—alternate frequently and rapidly, and often unpredictably, with idling phases. That requires an intelligent system that regenerates at the right moment and does so successfully. Because of the high temperatures produced during regeneration, it must not be allowed to happen on a field, for instance. To adapt the systems to all relevant applications and scenarios, we are conducting one of the most complex field trial programs in the history of MTU.

What do those trials actually consist of?

Dräse: We will have well over 200 engines in use with OEM clients right from the development phase. Those engines are provided with measurement and testing systems and serve as trial units both for MTU and the OEM clients. The knowledge gained will help us get all engine variants ready for the market before Stage V comes into force. That is important for some of our clients because they will produce and sell large numbers of their vehicles early on.

What will change for OEM clients? Will they have to develop new vehicle designs?

Krüper: For the OEM clients a lot will stay the same. The dimensions of our engines will remain the same. The interfaces will largely be unchanged as well as far as electronics, cooling systems and PTOs, etc. are concerned. In that regard, the amount of work required will be quite small for the OEMs. One thing that will have to be tackled is the installation of the integrated exhaust treatment system—its size will increase slightly due to the DPF. We will be offering extensive advice and support to OEMs in that process.

And how will end users benefit from the future products?

Krüper: End users will benefit from a number of advantages offered by the advanced engines. The engines will produce more torque but at the same time use less fuel. In addition, our drive systems will give vehicle users the certainty that their machines are highly reliable and environmentally safe in use as they will meet the emission standards then applicable. Albeit the environmental credentials do come at a price for the end user. The addition of the DPF means more complexity on the part of the drive system. But it goes without saying that users can rely on support from MTU service with the necessary maintenance.

This interview by Rolf Behrens with Bernd Krüper, head of the Construction & Agriculture business, and Frank Dräse, program manager for EU Stage V at MTU, was supplied to Off-Highway Engineering as part of the annual Executive Viewpoints series appearing in the June 2016 issue.

Continue reading »