Heavy-Duty-, On- und Off-Highway-Motoren 2021

The transport sector contributes significantly to global CO₂ emissions. In fact, road freight accounts for 9% of those emissions and is expected to further grow in the coming decades.

For heavy duty vehicles battery electric propulsion is seen as feasible for certain use cases, but it is considered as challenging i.e., due to size & weight of batteries as well as a lacking charging infrastructure. Other options like liquid and gaseous hydrogen as well as green methanol were recently investigated in a study done by Shell and TU Hamburg.

The paper gives a holistic overview of the production and distribution pathways, also considering constraints from the energy system perspective, requiring seasonal energy storage and molecular energy imports into Europe.

The following energy-carrier-powertrain options were investigated: battery electric, gaseous hydrogen, liquid hydrogen and green methanol. Efficiency losses along the supply chain were investigated. For all pathways also cost from the solar/wind farm to the wheel of the truck were calculated.

Currently CO₂ standards are not defined by legislation for powertrains of mobile machinery. However, CO₂ reduction is driven by political incentives, product strategies of OEMs and the economic evaluation of each application. DEUTZ AG, formerly known as non-captive manufacturer of diesel engines, is expanding its product portfolio to serve the OEM with CO₂-free powertrains needed for different applications.

In this paper DEUTZ gives an outlook on its technology strategy which comprises electric and hybrid powertrains from 48 to 400 V as well as combustion engines operated with synthetic fuels which are usable as drop-in fuels for existing diesel engines and gas engines which may be operated with regeneratively produced methane. Finally, the hydrogen engine is presented as an option for the use of green hydrogen produced by electrolysis enabled by regenerative wind or solar power.

The appropriate approach to energy options can only be understood when energy supply and its worldwide production is considered as a whole. Germany as an example was, in the past, always dependent on energy imports and it is assumed it will stay in this position in the future. Scientific analyses show that Germany will not be able to produce solar and wind power in a magnitude that will enables it to be independent from energy imports. Therefore, storage capacity for regenerative energy is needed. This can be either hydrogen or consecutive products.

In this paper, WinGD experts will elaborate how the experience and knowledge gained from the mid-size X-DF engines (such as X62DF & X72DF) were scaled up and adapted in the development of WinGD’s largest X-DF engine, namely the 12X92DF (see Fig. 1 below). In particular, it will highlight the specific challenges connected with the engine size.

It will also present how the Dual Fuel engine market has developed over time to include also the ultra large container vessel segment, creating the need for such large Dual Fuel engines as the 12X92DF.

It also gives an insight on the development of the latest generation engine control system, which took place in parallel with the engine development.

In addition, engine test results will be briefly summarized, as well as the service experience gained so far.

Gas engines are more attractive for stationary power generation than ever. MAN Energy Solutions’s proven and reliable gas engines are available with power outputs of 3 to 20.7 MW each and achieving electrical efficiencies exceeding 50%. While we are pushing ahead with the decarbonisation of our power plants, we are constantly adapting to customer needs.

European Transmission System Operators recently overcome critical grid frequency offsets. These challenges will remain, as Germany for example, will take large conventional power plants off the grid in the near future and the share of renewable but often volatile energy sources is growing steadily.

At the same time, hydrogen is becoming more and more interesting in the course of the energy transition and both European and national roadmaps are in place.

Concisely we believe fast starting Gas Engine GenSets arranged in a combined heat and power setup are a perfect choice to meet todays and future power generation needs.

Our focus in this publication is on the development of automatic Frequency Restoration Reserve (aFRR) functionalities for several German customers and fulfilling the requirements of ENTSO-E, the European Network of Transmission System Operators for Electricity, as well as EU 2017/1485 and national grid directives.

In addition, we would like to give some insights into how we customize our engines to burn natural gas/ hydrogen mixtures and thus supporting European and German initiatives on hydrogen.

The world of shipping is at a turning point. Due to the pressure of public debates, the entire industry is being called upon to become more environmentally friendly and to eventually reach climate neutrality. Shipping associations, ship-owners and large engine manufacturers have recognised this and are increasingly turning to alternative fuels. Alongside methanol, ammonia and other PtL (Power to Liquid) fuels, liquefied natural gas (LNG) offers one way of achieving these goals. Although currently still derived from fossil sources, LNG alone combines the properties of having a very well-developed land-based infrastructure, of enabling 100 % climate-neutral supply via electrolysis and hydrolysis, while offering the possibility to use any high proportion of climate-neutral synLNG as a drop-in fuel during the transformation process.

Up to now, engines in the marine sector, which are often designed according to the dual-fuel principle, have predominantly operated in fixed application areas. It is therefore possible for ships to bunker gas qualities that are as constant as possible at fixed stations and for manufacturers to optimise their engines for a certain gas quality range. This has mostly been achieved by means of specially adapted engine control unit mappings and hardware adjustments to the compression ratio. In the case of a worldwide application with frequently changing bunker locations, this approach has to accept disadvantages in efficiencies and emissions.

This paper characterises the combustion behaviour of medium-speed dual-fuel large engines on the basis of test bench measurements from a single-cylinder research engine operating using strongly fluctuating gas qualities. Engine control unit measures will be presented which enable the engine to operate in a methane number (MN) range from 105 down to 65 without hardware adjustments and without loss of performance. For this purpose, the Chair of Piston Engines and Internal Combustion Engines utilises a gas mixing unit with which the methane number (MN) and heating value (HV) can be adjusted by adding carbon dioxide and propane to the base gas. Adaptations of the pilot fuel injection strategy, especially with regard to injection pressure, quantity and timing, show great potential for reducing engine knock. The relationship between the energy release process in the cylinder and the occurrence of combustion anomalies is illustrated on the basis of combustion process and emission measurements.

This article examines selected experimental results and provides an outlook on further development steps towards an automated adaptation of the combustion process.

Two promising eFuels were investigated as 30% and 70% blend components with EN 590 diesel in injection chamber and single-cylinder engine tests: oxymethylenether (OME) and paraffinic diesel (HVO). Using a prototype injector from Woodward L’Orange GmbH that was equipped with a pressure sensing element in the control chamber we were able to gather information about fuel impacts on injector hydraulics. A high-pressure high temperature injection chamber was employed to assess the mixture formation, ignition and combustion behavior of the fuels. While the HVO-blends showed a very similar mixture and burning behavior, the OME-blends showed a significantly different flame structure with completely different soot oxidation behavior. Engine results showed high-quality drop-in behavior of HVO-blends with negligible impact on injection control and positive effects in terms of decreased ignition delay and reduced soot emission. OME-blends were significantly affecting the injection control and the needle dynamic due to their properties. OME-blends showed superior soot emission behavior at varying NO_x emissions.

With regards to reducing greenhouse gas emissions, CO₂-neutral fuels such as hydrogen, ammonia, methanol and synthetic liquified natural gas (sLNG) play a decisive role, especially for shipping and various off-road applications. In addition to the possibility of energy conversion of hydrogen into fuel cells, hydrogen combustion engines offer a number of practical advantages, such as the use of existing technology modules as the basis for robust solutions for propulsion systems at a considerable cost advantage. The present paper starts with the motivation, describing that hydrogen is part of the goals and not only a bridging fuel. In the second part, the challenges in engine operation with hydrogen on the engine design and charging are briefly described. On the third section, measurement results of test series with hydrogen combustion and H₂ natural gas mixtures on medium-speed large engines are compared and evaluated with engine results carried out with pure natural gas operation. The achieved mean indicated pressures at two different compression ratios are discussed. With lowered compression ratio, detailed results such as emissions, load increase at constant hydrogen content and hydrogen variation at constant load are described. The limits of combustion phenomena’s are described in two examples. Finally, an outlook on further development activities with regard to CO₂-neutral fuel alternatives is given.

The global target of Greenhouse gases (GHG) reduction for 2050 is one of the main focuses on selection and definition of the future power train in several business sectors.

The EU has agreed on new regulations to limit the CO₂ emissions of new heavy-duty vehicles by 15% from 2025 and by 30% (or higher) from 2030 considering 2020 as reference. Similar emissions reduction targets are expected to follow up in the off-road sector.

Hydrogen, as a combustion fuel, represents an alternative and efficient solution for decarbonization of the future power train in the Off-road sector. Combustion of hydrogen fuel can be achieved using several ways and system configurations that are mainly characterised by injection technology, air path configuration and ignition type technology.

This new solution shall be convenient to operate in harsh environments and offer a lower product cost compared to other zero emission technologies. Furthermore, the new engine architecture shall ensure easier engine integration, higher power density, better system efficiency, higher lifetime.

The port fuel injection (PFI) and direct injection (DI) are considered one of the possible strategies to assess the impact of the fuel path on the system characteristics. Additionally, the air path plays an important role in engine performance, dynamic behavior and emission compliance. Two-stage charging system and single stage with EGR are two possible air path configurations capable to ensure ultra-lean combustion which leads to low NOx emissions and higher power density at full load operating condition.

Furthermore, this technology is robust and ensures a quick time to market since the same vehicle interfaces can be used for integration of the hydrogen engine in the vehicles. Besides the advantages of this hydrogen technology, there are some challenges that this technology has to face. The main challenge is to reach an acceptable hydrogen storage volume able to guarantee the typical working time of an off-road machine. This point is not considered further here, but the authors are aware of this issue and suitable measures must be taken into account or implemented during the phase of technology integration in the machine.

The latest proposals by CLOVE (Consortium for ultra-low Vehicle Emissions) for Heavy-duty Euro VII legislation forecast significant tightening of pollutant emissions e.g. NO_x while also initiate an extension of the testing conditions leading to exceptional challenges in the powertrain development. In addition, the already phased-in regulations regarding CO₂ enforce a continuous reduction in fuel consumption. The legislative trends are similar in the US, where the already approved CARB 2027 regulation introduces a reduction in NO_x emission limits by 90%, while the GHG legislation requires reduced CO₂ emissions.

In order to fulfill the emission limits, a rapid start of NO_x conversion in the exhaust after-treatment (EAT) is inevitable. For this purpose, optimal calibration of engine-based thermal management in combination with advanced EAT layout are key technologies. Furthermore, cold start and cold ambient conditions during testing with low load profiles using as low as 0% payload may also require external heating measures of the EAT.

In this study a systematic investigation is carried out by means of model-based holistic approach targeting the definition of the EAT layout and optimal thermal management calibration for future legislations. The close-coupled dual-stage SCR with twin dosing is considered with multiple system layouts in order to minimize the fuel penalty during the heat up phases. An optimization of engine hardware concept and the engine thermal management are carried out and the potentials regarding CO₂ emissions quantified.

The investigations and the concept development consider both CARB ultra low NO_x as well as Euro VII future legislations.

YTO have developed a new family of diesel, water-cooled engines, comprising a 4.6 L 4-cylinder and a 6.9 L 6-cylinder engine. These engines, to be launched in 2023, will meet the future needs and demands for engine performance, emissions and operating costs, supporting YTO products in the off-highway machinery sectors around the globe.

The engines meet Euro Stage V and US Tier 4f emissions requirements, whilst delivering class leading performance. This paper will describe the key features of the 4-cylinder engine and the robust technology selection process. The 4-cylinder engine delivers best-in-class power and torque density (>30 kW/L and >175N m/L) for single stage, wastegate turbocharged for off-road engines. This performance is delivered with excellent fuel consumption (<196 g/kWh minimum full load BSFC).

A digital first approach has been used throughout the design and development, with simulation used to lead design selection and confirm attributes. Working closely with the supply base, cost effective technologies have been utilised throughout. As a result, a high level of maturity was reached through the virtual engine, allowing production tooling to be used for the core components of the first design prototype, and reducing the time from first prototype to Start of Production.

The commercial vehicle industry continues to move in the direction of improving brake thermal efficiency while meeting more stringent diesel engine emissions requirements. This study focused on fuel efficiency when using an exhaust burner during cold starts. Selective catalyst reduction (SCR) systems are very efficient at eliminating NOx from the exhaust once its temperature has been raised to 250 °C. The exhaust burner is used during a cold start to raise the temperature of the SCR system quickly, and then it is turned off once thermal preparation of the SCR is complete. The exhaust burner converts fuel energy to exhaust heat directly, and thus more efficiently, in comparison to engine measures such as intake/exhaust throttling or elevating the idle speed. Therefore, if engine measures are scaled back because the burner is responsible for SCR system heating, total fuel efficiency should be improved.

This hypothesis was tested at Southwest Research Institute (SwRI), making use of engine testing capabilities that allowed the results to be compared with those generated in the low-NOx technology demonstration funded by the California Air Resources Board (CARB). In addition to an exhaust burner, this testing made use of a conventional aftertreatment system (i.e. not a 2-stage SCR or “dual-dosing” system) that had been hydrothermally aged to end of useful life. FTP and WHTC cycles were run with the burner being responsible for more and more of the warm-up, allowing the tailpipe NOx vs. CO2 trade-off curve to be defined for this technology package.

Mandatory compliance with the most stringent exhaust emission limits is to be expected in the future, e.g. the new European exhaust emission limits for commercial vehicle diesel engines. The new, stringent NOx EURO VII commercial vehicle limits in particular, which are expected not before 2025, can only be achieved with very efficient heating technology for new, adapted exhaust aftertreatment systems. The highly dynamic Real Drive Emission (RDE) test cycles containing a high amount of cold starts that will be used in this context will confront the Euro VII commercial vehicle emission reduction systems with some challenges that are quite difficult to overcome. After the publication of the first promising results of component and initial engine test bench trials with the new heating measure for exhaust aftertreatment (EAT), a.k.a. the CatVap® system (see also previous publications, such as at the 15th MTZ/ATZ On-/Off- Highway Conference or MTZ 01/2021 et al.), more highly dynamic component and commercial vehicle engine test bench trials were carried out with an OEM medium duty and a heavy duty engine, each in conjunction with up-to-date combined exhaust gas aftertreatment systems of the EURO VI+ (e,f) generation, in conjunction with the newly established development consortium consisting of Fraunhofer ISE, Albonair GmbH, Vitesco Technologies Emitec GmbH and Thomas Magnete GmbH. This article shows the most relevant dynamic tests that were carried out (their basis being real world drive cycles, e.g. the special urban cycle), graphically visualized as well as in the form of corresponding test interpretations. Many of these tests were performed using dynamic test cycles, and their results are presented accordingly, including raw emission data in a percentage comparison with the effect on the tailpipe end emissions. It could be demonstrated that low NOx-levels can be achieved with a Euro VI+ EAT box and CatVap®. These tests have also shown strong fuel benefits with significantly lower NOx-emissions through CatVap® in comparison to internal heating measures. CatVap® can mitigate the trade-off between low NOx-emissions and low fuel consumption.

Currently, by far the largest share of CO₂ emissions in transport – around 80% – is caused by long-haul and heavy-duty vehicles with long range and/or high performance requirements. For these applications, the hydrogen combustion engine (H₂ engine) offers an effective addition to the fuel cell, to achieve a CO₂-free commercial vehicle sector

In order to achieve diesel-like standards of robustness and functionality, extensive investigations are carried out on a research H₂ test engine, which is installed and tested at MAHLE. In this paper, the challenges for the H₂ engine core components piston, piston rings and valve sets are presented, as well as measures to meet the high requirements illustrated.

The adaptation of the baseline diesel engine to spark-ignited H₂ combustion offers the possibility to use aluminium pistons. However, this leads to challenges regarding the piston shape, which have been matched against the background of thermomechanical stress.

The conflicting objectives between lubrication, oil consumption and blowby are one of the central challenges in the development of H₂ engines. By optimizing the power cell unit, the blowby and lubricating oil consumption can be decreased, thus reducing the crank case ventilation requirements and the preignition risk.

Valve set material solutions for applications with gaseous fuels and thus more challenging dry tribological conditions are well known. A new requirement for the material development of H₂ engines is the combination of moderate thermal load and high potential corrosion load due to the high water content in the exhaust gas.

Beside optimized diesel powertrains new powertrain options, such as hybrid electric, battery electric or fuel cell electric, will be required to comply with CO₂ regulations and to reduce the carbon footprint of the transport sector.

Each of these powertrain options has special requirements to its cooling system in terms of heat rejection, target temperatures of the components involved and required coolant properties. Therefore, the solution for each powertrain looks different and has its own challenges. This significantly impacts the cooling system layout, the size of the heat exchangers and the fan power required to get the cooling task done.

This paper will describe the cooling requirements for optimized diesel, HEV, BEV and FCV powertrains and highlight the special challenges for each of them. Dedicated cooling system layouts will be presented, and the main thermal management components discussed.

For the development of new, efficient and alternative powertrains an increasing electrification of its components is key focus. MAN Engines as part of MAN Truck & Bus SE is currently developing a marine propulsion solution with incorporated energy management system, that extends the proven diesel technology with an electric machine. Since the MAN Marine Hybrid System for marine applications provides a higher variance than conventional powertrain setups, the individual adaption for expected areas of use and load profiles plays a major role in the optimization process. Non-disruptive changes of operation modes give versatile challenges when developing and calibrating this system. Amongst others the high requirements in comfort and improved performance of the dynamic system behaviour will be described and characterized. Hereby the focus will be on operation mode transitions that could already be measured in the test bench setup. Supported by investigations on the elaborate test bench setup an evaluation of efficiency aspects gives a first impression on the economic prospects of the MAN Marine Hybrid System for the use in commercial as well as pleasure marine applications.

A concept for converting conventional diesel-powered long-haul trucks to a combined battery and hydrogen fuel cell powertrain is presented. The development of the concept is outlined whereas the focus is on the operational strategy, the thermal design, the spatial constraints, FEM strength simulations and safety aspects. Based on a costumer drive cycle the battery capacity as well as the fuel cell power output is determined with the help of a 1D-Matlab/Simulink model. Beside this the thermal system and especially the low temperature and high temperature circuit requirements are defined by system simulation. The results of these simulations were implemented in the design concept of the fuel cell heavy duty tractor (“HyBatt truck”) and are validated by the testing results of the first prototype.

Future automotive powertrains will be different. Digitalization, the limited availability of fossil fuels and especially the tightening of CO₂ legislation and other emissions are one of the key development drivers. For commercial vehicles, a CO₂ reduction of 30% by 2030 compared to 2019/2020 was defined by European legislation. A potential solution to reach these ambitious targets are fuel cell electric powertrain configurations. System efficiencies of up to 60% as well as the high gravimetric energy density of hydrogen are beneficial for long-haul applications. Furthermore, fuel cell systems can be integrated in existing electrified vehicle platforms. The availability for fuel cell system units on the market is currently limited to around 100 kW of maximum power, which is insufficient for a 40 t heavy-duty truck. Consequently, a modularization of fuel cell systems and the integration of multiple units is necessary. In this context, a model-based development approach for evaluation of system modularization concepts in terms of performance, durability, efficiency, package and costs was developed by IAV. With this proceeding, different fuel cell systems topologies for a 40 t long-haul truck are investigated.