Fewer emissions and lower consumption

Although combustion engines, particularly diesel engines, are widely regarded as being on the brink of extinction in public debate, they are far from finished in the off-highway sector. Here, they represent high availability, reliability and low operating costs with proven longevity under even the harshest of conditions. Besides industry-specific factors, it is particularly efficiency and the legal requirements for reducing pollutants that are the technological driving forces. The progress achieved in engine development to optimise mobile working machines in terms of fuel consumption and emissions will be one of the central themes at SYSTEMS & COMPONENTS, which will be taking place for the fifth time in parallel with Agritechnica in Hanover.

Fewer emissions at high output

Virtually all suppliers of classic combustion engines will be present on site with an extensive array of solutions to enable OEM customers to comply with the stringent exhaust emissions regulations according to European Off-Highway Stage V and US Off-Highway Tier 4 final. Many of these new developments are consistently pursuing the principle of downsizing: matured components for fuel injection (common rail system), engine and air management as well as exhaust gas aftertreatment slot together with low displacements to form fuel-saving powerhouses.

The suppliers are paying great attention to the modularity of their engine systems. Variably positionable individual components enable them to implement different installation variants and system integration in line with requirements. The versions differ, for example, due to fan attachments and belt drives, cylinder head covers and oil pans made of plastic and aluminium up to and including turbochargers with wastegate or charge pressure control with variable turbine geometry. Contrary to their diesel counterparts, natural gas variants are equipped with cooled exhaust gas recirculation. In order to comply with emission regulations, the engines are fitted with an exhaust gas aftertreatment system consisting of a diesel particulate filter (DPF), selective catalytic reduction (SCR) and diesel oxidation catalytic converter (DOC).

With biomethane for climate-neutral mobility

However, the different requirements made on mobile machinery such as dumper trucks, mobile excavators, tractors or combine harvesters also mean that there is no generally valid engine solution. In this context, openness to technology will be one of the most important keywords at SYSTEMS & COMPONENTS when assessing the portfolio of engines. Besides diesel engines, a range of other concepts such as parallel hybrid, range extender, plug-in hybrid and fully electric systems will therefore also be presented at the B2B platform in Hanover. Additional focus in Hanover will be placed on alternative fuels, which are intended to smooth the way to climate-neutral mobility. Amongst others, natural gas engines designed specifically for off-road applications in agricultural and construction machines will also be on show. Under real operating conditions, these output around ten percent less carbon dioxide than diesel engines.

In this process, the use of biomethane is increasingly shifting into focus in agriculture, as demonstrated by the New Holland T6 Methane Power – the world's first series production tractor that is powered by 100% methane. In its interior, a six-cylinder engine from FPT Industrial with a displacement of 6.7 litres combusts natural gas in compressed (CNG), liquefied (LNG) or renewable form (biomethane) and complies with the EU Stage V emissions standard thanks to the use of a three-way catalytic converter. The first units of this tractor are scheduled for delivery over the next few months of 2021, while an impressive number of pre-orders are also due to be produced and delivered this year. In the future, refuelling will therefore be possible at the farm's own biogas plant, provided that a corresponding gas conditioner is available. If the plant additionally ferments liquid or solid manure, the CO₂ balance is actually negative.

Synthetic fuels as a new option

Synthetic fuels offer a potential solution in the zero-carbon scenario that has been relatively overlooked thus far. They can be produced using regenerative electricity. The main advantage of these power-to-liquid-based e-fuels is their high energy density, particularly when compared to battery systems. The background to this is that, while small commercial vehicles in agricultural use offer the prospect of full electrification, this is barely achievable for heavy-duty mobile working machines. Partial electrification of the drive train with simultaneous use of smaller engines that are powered using synthetic fuels is one possible option for enabling relevant CO₂ reductions here. One example of this is regeneratively produced methanol, which could be used as a drop-in fuel in the off-highway sector. The challenge posed by e-fuels is that they require regenerative electricity for CO₂-neutral electrolysis and that this is not available in sufficient quantities at present. This important aspect on the road to a climate-neutral future will be discussed by engineers and experts in the 'Future Lounge' expert forums at SYSTEMS & COMPONENTS.

For a long time, hydrogen has played a subordinate role in the development of CO₂-neutral drive concepts in the off-highway sector. The complex conversion of other forms of energy to hydrogen appeared to be anything but the ideal solution to achieving the goal. However, since the European Union launched the 'European Clean Hydrogen Alliance' (ECH2A) in July 2020, industry focus is shifting increasingly to this topic. And not without good reason, because regeneratively produced hydrogen is not only suitable as a fuel for fuel cells – it can also be used directly in combustion engines and gas turbines. Since hydrogen is a fuel that contains no carbon, only minimal quantities of emission components from combusted lubricating oil are incurred. Thanks to its low exhaust gas temperatures, nitrogen oxide outputs are already below the limit values even without exhaust gas aftertreatment. Efficient, lean operation additionally results in a consumption advantage in comparison with conventional combustion engines.

Hydrogen engines are picking up pace

So what form does the ideal hydrogen drive train for an excavator take? SYSTEMS & COMPONENTS aims to answer this question with the engine and turbo engine adaptations necessary to achieve this. Engine manufacturer Deutz has already presented such a prototype as an alternative to fuel cell technology: the TCG 7.8 H2. The hydrogen variant of the six-cylinder in-line engine for agricultural machinery can also be used in various hybrid configurations in combination with electric drives. The recipe for success for CO₂-free combustion engines consists of efficient injection, lean combustion, exhaust gas recirculation, turbocharging and a special hydrogen catalytic converter. A project being undertaken at the Institut für Kolbenmaschinen (Institute for Piston Engines) at the Karlsruhe Institute of Technology (KIT) is also exemplary in this context. It is investigating the potential of future combustion methods using the example of heavy-duty commercial vehicles. To do this, the hydrogen is first injected into the engine's intake manifold and then, after converting the engine, directly into the cylinder. This enables Institute Director Prof. Thomas Koch and his team of scientists to analyse the influence of mixture formation on combustion. The aim is to establish the future technology road maps for commercial vehicle drives on this basis and to determine the technical challenges involved in implementing hydrogen engines.

The engine mix of the future

The performance of modern off-highway vehicles is based on the reliable and precise operation of their engines. The diesel engine will remain the engine of choice in the technology mix for the foreseeable future, but it now has competition. Whether gas, hybrid or electric, as regards the guiding SYSTEMS & COMPONENTS theme of 'Green Efficiency – inspired by solutions', the solutions on show in Hanover will help to unite market requirements and emissions regulations.