Heavy-Duty-, On- und Off-Highway-Motoren 2019

The manufactures of internal combustion engines face currently a lot of challenges. Among these are the required drastic emission reductions of carbon dioxide (CO₂) as well as harmful substances the most prominent. As a consequence of these harsh market conditions solutions that could cope with this framework are urgently needed. In this context the state of the art of synthetic fuels as an essential part of the energy system is discussed and how they could offer solutions.

In addition to the technology developments at Fraunhofer ISE providing innovative solutions in clean mobility such as the CatVap® technology and more efficient synthesis pathways to oxymethylene dimethyl ether (OME) the energy system analysis is one important research topic. One goal of these energy systems simulations is to find the cost optimized pathway of the transformation process. The simulation results are used as a basis for investigations to optimize national / regional energy systems with consideration of all energy carriers and consumption sectors taken into account the CO₂ reduction goals. The results clearly show that hydrogen will play a significant role and water electrolysis will be the key technology in order to reduce the transformation costs, to stabilize the grid and to connect the renewable energy power sector with the other sectors (transport, industry, buildings) for defossilization. This green hydrogen can be further converted together with CO₂ via Power to X (PtX) concepts into synthetic fuels such as methanol, dimethyl ether (DME) and OME offering both CO₂ reductions and reduction of pollutants. PtX will be installed globally in those regions of the world with favourable site conditions for renewable energies (PV, wind). As a consequence this will result in the establishment of a global trading system for renewable energy.

With the Stage V Emission regulation of the European Union (EU) a new limit for the particulate emission including particulate number is introduced for diesel engines from 19 to 56 kW. Thereby new control strategies regarding particulates are required in this engine category. This article describes the DEUTZ engine platform concept for the engine category from 19 to 56 kW with a diesel particulate filter (DPF) as a standard technology to fulfill the EU Stage V emission regulation.

The technical requirements of engines for non-road mobile machinery are described as well as the derived hardware concept of the engine family including the exhaust aftertreatment system. The introduction of a new ECU platform is used by DEUTZ for a new software concept with an airpath model based on a combination of physical engine models and data based numerical models to ensure the best performance and robustness under all ambient conditions. Furthermore, DEUTZ developed a new engine emission model including a DoE tool to reduce the calibration effort and improve the DPF model quality at the same time. The article also gives an insight on development methodology with an outlook on the virtual calibration using the DEUTZ offline simulation tool “xQtec”.

In 2019, MAN launched a newly developed engine with a displacement of 9 liters. In addition to traditional applications for trucks and coaches, the industrial version has been presented at the same time. For its first application in the off-highway segment, the engine is used in agricultural tractors, where SCR-only combustion and exhaust gas aftertreatment have been completely revised and adapted. The low-speed concept and excellent engine dynamics were of particular importance.

A large number of field cycles were analyzed during testing and the test program was adapted to the tough conditions in the tractor.

Moreover, this report presents activities and results for recording the tractor’s Real Driving Emission in a wide range of applications.

Today’s challenge is to almost comply with the emission limits 100% in Real Drive Emission (RDE) behavior, especially in the cold season, the so-called “cold city rides”, which are characterized by the fact that during the stop and go rides in the city at no time a sufficient temperature for an efficient exhaust aftertreatment is reached. The future Euro6+ or certainly the expected new Euro7 limit values will therefore only be achieved with suitable effective thermal heating, heat retention as well as regeneration measures for the exhaust aftertreatment (EAT) system.

CatVap® is an easily scalable system for both diesel and gasoline engines that provides highly efficient thermal energy, simply from fuel (diesel, gasoline, synthetic fuels), coupled into the exhaust system and thus provides the thermal energy required for exhaust gas conversion. It is fast, highly dynamically controllable, can be used as a catalytic burner for rapid heating during a cold start of the engine system. Furthermore, CatVap® can then be used as a light-off accelerator (by fuel tailoring to synthesis gas (syngas) and shorter alkenes) for the Diesel Oxidation Catalyst (DOC) and the Selective Catalytic Reduction (SCR) catalyst. CatVap can also be used for the diesel particulate filter, for its effective active regeneration or temperature control for continuous regeneration.

The CatVap system is an important key enabler for near zero-emission internal combustion (IC) engines that can be demonstrated in the near future.

Lean burn methane fueled combustion engines give low tailpipe CO₂ emissions compared to diesel and stoichiometric natural gas applications. Optimised engine efficiency by operating lean combined with a low carbon containing fuel lead to the lowest possible tailpipe CO₂ for a non-hybridized system. However, due to the lean combustion mode, both NO_x and CH₄ become a challenge for exhaust emissions control. Traditionally, urea based SCR is used to control NO_x and a highly loaded precious metal based methane oxidation catalyst (MOC) is used to attempt to achieve low tailpipe CH₄ emissions. Therefore, due to the number of catalyst and the associated control requirements, the cost of the combined aftertreatment solution becomes a significant proportion of the total engine cost. In addition to the high cost of the methane control catalyst, the MOC only becomes highly efficiency in the region of 500°C, which for lean operating engines is rarely reached under normal engine operation.

Due to the high temperature stability of methane, a novel approach has been taken to develop a catalyst system which is able to oxidise methane at low temperatures, via the use of alternative oxidising agents. Dioxygen (O₂) is relatively stable, whereas ozone (O₃) is highly reactive and is a significantly stronger oxidising agent compared to O₂. Synthetic gas reactor experiments were performed using O₃ as the oxidising agent and methane as the hydrocarbon feed. A current production iron based SCR catalyst was used and was found to oxidise methane at 220°C with an efficiency of >60%. Experiments are continuing with a multi staged fixed bed reactor with the aim of demonstrating >95% conversion, leading to the potential to eliminate the expensive PGM based MOC. These results will be presented at the conference. There is a cost associated with the on-board O₃ generator and the associated power consumption needs to be included in the engine efficiency. However, the solution is anticipated to deliver a significant GHG (CO₂ + CH₄ equivalent) reduction compared with diesel and stoichiometric NG solutions but at an aftertreatment cost that is lower than diesel and equivalent to stoichiometric NG. This paper will discuss the novel approach to emissions control utilising an alternative oxidising agent for low temperature and low cost emissions control, including the advantages and disadvantages of the system for different applications.

Selective catalytic reduction (SCR) is an established technology for treatment of exhaust gases from combustion engines. However, a major drawback of typically used monolithic catalytic converters is their susceptibility regarding high particle loads. Clogging is a critical issue limiting space efficient design and operation time, particularly under high-dust operation from HFO fired large bore Diesel engines. In order to evaluate the clogging risk of exhaust gas treatment systems (EGTS) during the design process, a novel simulation approach for deposit formation has been developed and is presented in this paper. An Eulerian-Lagrangian treatment has been utilised for simulation of the particle-laden exhaust gas flow, where drag, gravitation, buoyancy, turbulent dispersion, Saffman’s lift force as well as Brownian motion are considered as governing particle transport mechanisms. For the modelling of the gas flow (CFD), the monolithic catalyst is represented by a porous media formulation. The grid used for the CFD is extended by a collision subgrid providing more detailed geometry data for particle-wall contact consideration. The sticking probability of an impacting particle is calculated based on an elastic-adhesive contact approach. The simulation procedure has been developed using ANSYS Fluent. The underlying subgrid as wells as the particle-wall contact model have been implemented to the flow solver via multiple User-Defined Functions (UDF). The model development has been accompanied by extensive experimental investigations on a test rig with a 4-stroke single cylinder research engine of type 1VDS18/15-CR. The simulation procedure achieved good agreement with respect to experimental data of particle capture efficiency as well as reduction of open frontal area (OFA).

The recently achieved agreement within the European Union introduces very challenging limits for CO₂ emissions for heavy duty vehicles. Until 2025 a reduction of 15% in average and by 2030 of 30% has to be achieved. To ensure a low-CO₂ and low-emission, up to locally emission-free, mobility, the drive concepts of the future will necessarily increase the variety with the introduction of electric drives and fuel cells but also keeping a good share of internal combustion engines (ICE) being powered by Diesel or even Hydrogen.

In addition to particle emissions from the aftertreatment box, a further known source is crankcase ventilation. Using a modern separation system, the particle mass limit is adhered to, thus enabling open crankcase ventilation into the atmosphere in heavy duty combustion engines. Since closed crankcase ventilation influences the powertrain negatively due to compressor coking, contamination and high ash emission, the open crankcase configuration is very common. The Euro VI legislation introduced a total particle number limit. This brought the focus onto smaller particles stemming from the separation system, in addition to the bigger particles that are of concern when meeting the particle mass limit.

Efforts to reduce the engine particle raw emissions prior to the separation system have been successful, as has the improvement of the separation system itself.

This paper focuses on the drivetrain as the suspected main origin of micron and submicron oil aerosol particles. A single cylinder engine with real-time piston temperature measurement equipment enables further insights into parameters for particle formation on the one hand, and the analysis of different countermeasures on the other.

This article points out the engine oil temperature, the engine load and the piston oil nozzle flow rate as main formation parameters.

Additionally, the connection between specific oil aerosol diameter modes to the combustion process and the piston surface temperatures is shown.

Drivetrain tribology and heat management are highlighted as major countermeasure categories, and several ideas for reducing emissions are discussed.

Finally, the influence on emission reduction of a piston filled with a heat transfer medium is demonstrated.

In this article, a procedure for the application of virtual sensors for load-related sizing and lifetime prognosis of components of large diesel engines is presented. Due to high costs for testing to assure the lifetime of a large diesel engine, the knowledge about the load is of utmost importance. The approach consists of several steps beginning with the identification of the relevant loads on specific components and ends with either a prognosis of the remaining useful life (RUL) or the use of load spectrums for the development. Virtual sensors are models that use given input variables to estimate an undetected output variable of the system. Thus the load of the system during the installation is determined. The load-time signal can be used for both a stress appropriate design as well as a prediction of the remaining useful life. The necessary steps for deriving requirements for the development process as well as the lifetime prognosis are described.

Solenoid coil injectors are widely spread in the agricultural and heavy-duty vehicle sector. These types are installed due to their higher development status, longer service life and robustness. Nevertheless, injector problems are one of the more frequent causes of malfunctions and failures in diesel combustion engines. Due to ever smaller diameters and more precise coordination of the individual components, injector deposits can have a major influence on the function of injectors. Deposits change the injected fuel mass, the emissions and the reliability of the engine. Reliability is the by far the most important customer requirement of commercial machinery. Especially internal deposits can lead to a complete failure of the engine. For example, the injector can stick in closed or even in open position and may cause engine damage. This paper presents a method for detecting internal and external deposits in the injector. The basis for the detection method is a high sampling rate of the rail pressure sensor.

The results allow a qualitative statement about the injector condition. Internal and external deposits can be distinguished. If the deposits are too big, a service recommendation for injector replacement is issued.

Upcoming IMO emission regulation like the reduction of the fuel sulfur content in year 2020 and more stringent NO_x emission limits force engine manufactures and ship owners to rethink the configuration of fuel and exhaust aftertreatment for their application. It is likely that global shipping will use a variety of different fuels it the near future from distillates to heavy fuel oil in combination with SO_x scrubbers.

The Recuperated Split Cycle Engine (RSCE) is a new type of in-ternal combustion engine (ICE) with potential for clean, sustainable heavy duty, longhaul and distributed generation applications. The RSCE separates cold (induction, compression) and hot (combustion, expansion) parts of the cycle, and recovers waste exhaust heat between them via a recuperator. The engine has been developed to Proof of Concept stage using a mix of hardware testing and simulation; and has shown exceptional results for both air quality emissions and thermal efficiency. A single-cylinder engine has demonstrated controllable cool combustion, with NOx emissions that can be after-treated to SULEV or below, and potential for “near zero”. This engine also validated a simulation model of a multi-cylinder prototype, demonstrating Brake Thermal Efficiencies of between 50% and 60% depending on the level of technology applied. These credentials place it on a par with “zero emissions” propulsion. A life-cycle analysis is presented for the concept in the mid-term, highlighting its advantage against alternatives with high embedded energy. The concept is compatible with either Diesel or Natural Gas and their sustainable replacements, and potentially with future fuels such as sustainably sourced Hydrogen or Ammonia; further thinking is described on how such fuels may be supplied to the heavy duty sector in the longer term. Because the engine and fuel both have “backward compatibility” with existing products, the transition to sustainable power is far easier than with zero-emission alternatives, delivering substantial GHG mitigation in the 2030 timeframe while providing a long-term solution beyond that.

In February 2019, the European Parliament, Commission, and Council agreed on final CO₂ emission targets for heavy-duty trucks. The fleet average CO₂ emission reduction targets for new trucks have been set at 15% by 2025, and at 30% by 2030, relative to the 2019 emission levels. To achieve these ambitious targets, every aspect of engine technology has to be optimized.

Modern hybrid propulsion systems find their ways into more and more applications. This is also valid for marine and rail applications which hugely can profit from this innovative technology. A rigorously optimized system integration combining the well proven diesel engine with highly innovative electrical components and modules leads to significant reduction of fuel consumption, CO₂ and noise emission and increase of comfort. Therefore, environment and customers profit equally from this solution. Critical to success is the system view rather than the component view. The individual components and modules need to be integrated in a way that all interactions are considered and controlled for optimal performance. Smart control algorithms and systems finally make the performance benefits happen.

As stated by the EU commission, on-road HD vehicles (including busses, lorries and coaches) are responsible for approximately 25% of CO₂ emissions from road transport within Europe. This equates to ~6% in total CO₂ emissions in Europe and is expected to increase by 9% by 2030. This is despite continued advances in HD vehicle fuel economy. To combat this and help meet the Paris Agreement GHG targets, the EU commission has set performance standards for new HD vehicles to reduce CO₂ emissions by 15% for the year 2025 onwards and 30% (subject to review in 2022) for the year 2030 onwards. This reduction is compared to a reference 2019 fleet CO₂ figure and is determined using the VECTO simulation tool. For HD OEMs to meet these challenges in the short timeframe, new technologies, some not represented in the current version of VECTO, such as waste heat recovery, alternative fueled engines, predictive control strategies and hybridization will be required.

This paper will evaluate the potential CO₂ benefit of selected HD technologies and technology packages expected to meet the EU HDV 2030 CO₂ legislation. It will focus on the 4x2 tractor unit application over the VECTO long haul and regional delivery drive cycles. Additionally, the commercial viability of these packages will be investigated. The use of VECTO as an effective certification tool for measuring Heavy Duty Vehicle (HDV) CO₂ emissions will also be discussed.

Carbon dioxide (CO₂) emissions can be reduced through newer powertrain concepts with electrification, efficiency optimization, and through alternative fuels. The focus of this work is on alternative fuels and optimizing engine efficiency for selected fuels on a large bore engine (> 170 mm). We surveyed alternative fuels with a lower carbon to hydrogen ratio than diesel fuel, or fuels without carbon. Examples of such fuels are: natural gas (including liquified natural gas (LNG) and its variability), methanol, ethanol, liquefied petroleum gas, ammonia, and hydrogen. The knock limited loads and possible efficiency targets were estimated using a closed cycle simulation with chemical kinetics. The achievable power densities and emitted CO₂ levels are presented. In addition to simulation, single cylinder test results are presented for natural gas fuels. The total cost of ownership (TCO) analysis focused on a high fuel use application, in this case, stationary electric power generation. Natural gas is a good alternative fuel for heavy duty applications based on cost and availability.

In this contribution we focus on Europe, on heavy duty applications and on liquefied methane-based fuels (both fossil and renewable LNG).

Auf der ATZlive-Konferenz Heavy-Duty, On- und Off-Highway Motoren in Friedrichshafen am Bodensee diskutieren über 190 Teilnehmer und 22 Aussteller über die Herausforderungen, die auf den Transportsektor und die Landwirtschaft in den nächsten Jahren zukommen. Im Fokus der Diskussionen steht vor allem die Senkung von Treibhausgas (GHG)-Emissionen. Synthetische Kraftstoffe scheinen hier ein nötiges Mittel, um die im Pariser Abkommen vereinbarten Ziele zu erreichen.