Internationaler Motorenkongress 2023

Within the joint project “H₂ ICE Democar”, funded by the Federal Ministry for Economic Affairs and Climate Action, Ford, Bosch, MAHLE, Umicore, Institute of Automotive Engineering (IFS, University of Stuttgart), Research Institute for Automotive Engineering and Powertrain Systems (FKFS), Chair of Thermodynamics of Mobile Energy Conversion Systems (tme, RWTH Aachen University), DHL and Shell are identifying key requirements for the powertrain of a light commercial vehicle with H₂ engine and hybrid powertrain. The potential of the technical solution will be demonstrated for a logistics application by a demo car. Besides engine and vehicle testing, simulations and experiments are carried out to gain a deeper understanding about the specifics of H₂ engine operation in a hybrid powertrain.

This paper focuses on selected aspects of the project such as modification of the well-known 1.0 L Ford EcoBoost three-cylinder gasoline engine for H₂ operation. The analysis and optimization of the mixture preparation, verified by high-speed Schlieren measurements, 3D-simulation and thermodynamic analysis performed on multicylinder engines is discussed in detail as well as the selection of a suitable turbo charging system to enable lean operation (λ > 2) in the complete engine map.

Emission legislation limits have tightened in recent years. With regards to the European Union, the new Euro 7 legislation is expected to come into force within 2025. Furthermore, discussions on zero-impact emission levels are ongoing, which in addition are relevant for the assessment of future propulsion systems. In this study, the exhaust aftertreatment system (EAS) of an SI DI 2 l hydrogen engine with dedicated emission control is experimentally evaluated in stationary operation. After that, transient experiments with both low- and high-load RDE driving cycles are conducted. A special focus is put on the heat-up phase of the EAS. Various heat-up measures, including retarded ignition timing, load point shifting and an electrically heated catalyst (EHC) are considered. The 3 kW EHC showed good performance and was further used for the EAS heat-up. The driving cycles are then experimentally conducted with an EAS consisting of an EHC, an SCR catalyst, an ammonia slip catalyst (ASC) and a particulate filter (PF). In the WLTC, NO_x tailpipe emissions as low as 1.7 mg/km are achieved, which means a reduction rate of 98 %. In the low- and high-load RDE cycle NO_x reduction rates amount to 90 %. Measurement results are assessed towards upcoming Euro 7 emission limits and – in a first approach – towards recently published zeroimpact emission levels. The obtained results underline the potential of a hydrogen engine towards zero-impact emission propulsion technology.

Alternative fuels are increasingly important in the redesign of commercial vehicle engines. So far natural gas (methane) was the pioneer for the conversion of existing commercial vehicle drives. The market penetration on the different continents however varies a lot: In the EU the market share of commercial natural gas vehicles play a minor role, whereas in China around a tenth of all heavy commercial vehicles run on methane. In the USA the sales numbers for gas-powered commercial vehicles are below the expectations from a decade ago, although a local commercial engine manufacturer is constantly expanding its portfolio and preparing for higher sales volumes in near future.

The rising prices of precious metals in the methane three-way catalytic converter and the higher costs for natural gas additionally damp the sales increase of gas engines. Furthermore, the refueling infrastructure is still not fully established in the entire EU. The CO₂ fleet reduction targets in the EU are more favoring the penetration of completely CO₂-free drives, which in recent years draw the attention to hydrogen as a fuel for engines.

The hydrogen engine has a lot of economic advantages compared to other CO₂ free powertrain concepts, however the development taking the Diesel as baseline has some challenges.

Currently more and more commercial vehicle manufacturers are considering the use of alcohol fuels. Ethanol turns out to be very popular on the American continent, Methanol is of particular interest for Chinese OEMs. Non-road applications (e.g. agricultural machinery) could become one of the most important for alcohol fuels which turned out to be particularly challenging in view of mixture formation, cold start and mechanical durability.

All alternative fuels mentioned (natural gas, hydrogen, ethanol, methanol) bring their individual development challenges with regard to mixture formation, combustion anomalies, cold start behavior, thermomechanical strength and mechanical durability. What they all have in common is an otto-engine combustion concept. AVL shows possibilities of adapting existing engine platforms in the best possible way for these fuels, so that maximum availability of identical parts with a highly efficient diesel concept (e.g.: HVO) is ensured.

One of society’s major goals for the coming years and decades is to reduce greenhouse gas (GHG) emissions. To reduce emissions in on- and off-highway applications, Liebherr develops injection components for greenhouse gas-neutral combustion engines. This paper provides an overview of Liebherr’s portfolio strategy regarding fuel injection solutions that run on zero-emission fuels.

The requirements of different applications as well as infrastructural and logistical limits will require the use of different fuels in the future to achieve the above-mentioned goals. Liebherr has been investigating the possibilities of eFuels and methanol since 2017 and started development activities for hydrogen injection solutions in 2019. For hydrogen, the market demands both direct injection (DI) and port fuel injection (PFI) solutions. Liebherr’s DI and PFI solutions are based on a common design concept and platform to exploit synergies in product design. In addition to hydrogen, its derivatives are also needed as potential fuels, especially in shipping and mining. This leads to the demand for fuel-independent engine platforms. Due to the modular approach of the hydrogen injector platform, ammonia and methanol are investigated in addition to hydrogen. This article gives insights into the first component investigations.

“FVV Fuels Study IV” (published in 2021) provided a comprehensive analysis of different powertrain technologies and energy pathways for the European transport sector, all of which are exclusively based on renewable energy sourcing through wind and solar power generation capacities, with regards to their overall infrastructure requirement, costs and associated “Well-to-Wheel” (WtW) greenhouse gas (GHG) emissions. The study concluded that overall cumulated GHG emissions vary much less across different technology pathways (e.g. electric vehicles vs. vehicles with combustion engines operated with carbon-neutral fuels) than typically expected. In fact, the “ramp-up” speed of deploying GHG-neutral mobility solutions is much more important than the choice of technologies itself, since the majority of GHG emissions is caused by the phase-out of the vehicle legacy fleet which is still operated with fossil energy carriers. Therefore, the faster defossilised vehicle operation can be introduced, the lower are the cumulated GHG emissions and thus the impact on climate change. Therefore, the achievable ramp-up potential is of upmost importance to meet the Paris climate targets.

In this context, “FVV Fuels Study IVb” further explores the achievable transition (ramp-up) of the European road sector towards climate-neutrality to achieve GHG neutrality as early as possible.

As main conclusion, a favorable mix of carbon-neutral mobility pathways can speed up the transition to GHG neutral mobility significantly. With such a mix – achievable under ideal regulatory conditions provided in 2023 – GHG-neutrality can be achieved by the year 2039 already, while a single technology battery-electric- vehicle (BEV) scenario cannot achieve carbon neutrality by 2050 due to binding bottlenecks (as e.g., electrical grid extension) and will have emitted 39 % more GHG emissions until 2050 than the optimum mix scenario. In this context drop-in capable e-fuels provide a unique technology option to GHG-neutrally operate the existing fleet once they become available at large scale. Despite long lead times for setting up large-scale synthesis plants, e-fuels can accelerate overall GHG reductions considerably.

This paper covers the challenges within China for the reduction in CO₂ emissions including within the automotive sector, to meet the 2015 Paris climate agreement of net zero by 2060, while balancing the need for increased energy consumption as the country continues to economically grow and balancing the aspirations of the general populous. The demographic challenges due to the size and the geography of the country mean a complete step to a fully electrified passenger car market is not possible in a time frame followed within Europe because the base energy production is still coal based. Therefore, a pragmatic approach of using hybridization in parallel is being followed with increasingly challenging fuel economy targets to ensure efficiency is continually maximized. To this end Geely has developed and continues to develop a modular hybrid platform under the Nord Thor Powertrain name, that covers all potential permutations of applications to offer the customer covering HEV, PHEV, Flex fuel and Range Extender applications.

The 2050 zero cradle to grave CO₂e emission commitment of Volkswagen has started in the group subsidiaries strategic studies and actions to find the most feasible “Way to Zero” for each region. For South America, especially regarding its biggest market, Brazil, the stablished European trend for high volume battery electric vehicles (BEV) will most likely not take place for passenger cars and light commercials in the middle term. The reason are local hurdles, common in emerging markets, such as the affordability for the average customers, a still in-construction charging infrastructure in a continental-size country and more urgent social priorities for public investments. On the other hand, the region vocation for agriculture make it attractive to take the opportunity of the already stablished biofuels infrastructure as a short and middle term action to reduce CO₂e emission related to individual mobility. Nevertheless, this reduction will face technical, political and sustainability related challenges, becoming a multidisciplinary subject. This paper aims to describe the current situation of the main biofuel of Brazil, ethanol, and discuss the possibilities to use its potential as a complementary strategy for mobility decarbonization in this part of world.

The influence of hydrogen combustion on engine components – especially in full load operation – is still largely unknown. For this reason, a series engine was converted for operation with hydrogen and a 350 h durability run was carried out in full load operation. The engine was operated with direct injection and exhaust gas turbocharging adapted for lean-burn operation. After the durability test, the pistons, pins, ring package, valves and valve seat inserts were analysed for hydrogen embrittlement, corrosion and wear, as well as other changes. In addition to the actual examination and analysis of the engine components, it was necessary to develop suitable boundary conditions regarding the ignition and injection system to be able to complete the durability run at full load.

Additionally, to the challenges posed by the direct contact of hydrogen with engine components, the consequences of irregular combustion (high mechanical and thermal stress) must be considered in component design. Reasons for these combustion anomalies can be oil droplets or hot particles in the combustion chamber and residual discharges of the ignition system. In order to avoid detached particles from deposits on the piston, the input of engine oil into the combustion chamber, which is already minimized in current applications, must be further reduced. The durability run provided first important findings regarding deposit formation and its influence on irregular combustion.

The aim of the test is a screening of crankshaft and valve train components in hydrogen operation at full load and the derivation of suitable measures for materials and coatings for series use.

Clear messages are coming from the Asian region in particular, both in terms of economic policy and industry, that the internal combustion engine is once again gaining strategic importance in the context of open-technology competition with the fuel cell and battery-electric drive.

So far, the focus on hydrogen combustion has been on combustion process development. Starting from PFI, with relatively low power output, current investigations are moving toward direct injection. Water injection for hydrogen engines is also the subject of discussion, and the first runs on the test bench are being completed. These increasing demands on the tribological system, such as the interaction between pistons and piston rings on the cylinder bore, require intense interaction between a number of disciplines. Corrosion and material compatibility are not the only challenges, but also the washing off of the engine oil, which have to be solved by a carefully targeted choice of materials and optimized honing. In addition to the basic setup, which makes the system durable for its lifetime, the focus is on the 1 g/km CO₂ target. The conflict of goals of low oil consumption with low friction is countered with new approaches to surface finishes. New tooling and software solutions make it possible to qualify the cylinder bore for the tasks of hydrogen combustion without a significant increase in cycle time in series production.

For the piston-group/liner system, an expanded understanding has been built up in recent years, which can now be used in hydrogen engines in combined form.

Regarding CO₂ reduction on commercial vehicles, hydrogen engine is becoming a strong complementary solution, especially for high load profiles. In addition, costs and durability make internal combustion engine a very attractive and effective solution based on current powertrain layouts. The first generation of hydrogen engines follows spark ignited engine combustion processes, which are operated lean with intake manifold or low-pressure direct injection. These concepts have some limitations on the achievable efficiencies and power densities. To achieve significant increase in efficiency, an alternative combustion process close to diesel combustion is required. That demands hydrogen to be injected under high pressure near top dead center. The available or necessary approaches to initiate the diffusion combustion of the hydrogen are also discussed to show path to the target of 50% BTE.

Different engine technologies will expose Hydrogen in different levels, which can create concern of embrittlement. Hydrogen embrittlement is caused by two main mechanisms: high pressure and temperature exposure or high corrosion. In a Hydrogen combustion engine, the key mechanism is high pressure exposure. Hydrogen penetration mechanisms are related to voids and soft materials where it positions on the grain boundaries. Cast irons are favorable to resist embrittlement due to the high number of graphites, serving as an accommodation to hydrogen, delaying embrittlement effect. The shape of graphites and different alloy elements will play an important role on embrittlement resistance combined to the mechanical and fatigue resistance, also necessary on such highly efficient engines. Bench tests and measurements in parallel to dyno evaluations are presented to support the alloy development.

In order to meet global climate targets in time, there is no other solution than the application of carbon removal technologies and thus Direct Air Capturing (DAC) as a key technology. The large-scale deployment of DAC technology will require a relevant investment based on viable business opportunities.

A cost efficient removal technology relies on a robust capturing approach. The filter materials are crucial for DAC as they define the boundary conditions for the overall process and have a massive influence on the operating as well as capital expenditures. Therefore, the design of a plant must be accompanied by simulation methods, whereas, depending on the task, the depth of simulation covers several length and time scales.

Engine tests of a ReFuel as a desirable CCU-product point out, that an optimal ReFuel contributes to improving consumption and emissions not only due to its sustainable base stock, but also due to its fuel properties. Further improvements could be achieved if the engine management system was prepared by objecting the calibration data for the future use of an optimal ReFuel (to be developed).

Only if the global political framework conditions are set, ReFuels as a product could generate a relevant return on investment and thus refinance the scale up of sustainable carbon capture technologies for a closed loop carbon economy. This would open up the urgently needed options to address a solution for unavoidable CO₂ emissions on a global way towards a net-zero-society in the upcoming decades.

The subject of these investigations at the Institute for Internal Combustion Engines and Powertrain Systems is the evaluation of a variable valve train system in terms of the potentials with alternative fuels (HVO and OME). In the context of this article, tests are carried out on a single cylinder research engine (SCRE) with a variable valve train, that allows internal EGR in different amounts on the exhaust side as well as a Miller stroke on the air intake. Each exhaust valve can be switched between two camshaft contours, which allows four setups on the exhaust side. On the intake, the camshaft contours of both valves are switched at the same time, which allows Miller and regular setting. Previous investigations have shown, that exhaust temperatures decrease with OME in comparison to Diesel. With the variable valve train, the exhaust gas temperature can be increased and at the same time raw emissions be lowered. The investigation of these effects compared between Diesel, HVO and OME are part of this investigation. Additionally to these investigations, the Miller stroke is under investigation. Less fresh air enters the combustion chamber and the effective compression ratio is reduced. On the other hand, the efficiency of the combustion itself can decrease. Higher efficiency is achieved when the reduced compression work overcompensates the combustion disadvantages or boost pressure is used for compensation. Especially with OME and its higher amount of molecular bounded oxygen the advantage regarding the less sensitive efficiency decrease with high EGR rates is expected to be higher than with Diesel and can show the potential of a synthetic fuel with low NOx-emissions in combination with a variable valve train system.

Along with the ongoing discussion to define a future EU7 emission legislation, the idea of so-called On-Board Monitoring (OBM) was highlighted as well. OBM will be designed to ensure that vehicle emission limits will not be exceeded over lifetime. This will require monitoring of tailpipe emissions in the vehicle by using emissions sensors and model-based emission prediction. Targets coming along with tailpipe emissions monitoring will be a timely detection of high emitting vehicles and enforcement to repair these vehicles to minimize on road emissions. Technically, such an OBM introduction needs to be prepared well and high development efforts for hardware, emission modelling and engine control software are expected. Sensor values as well as the emission behavior of vehicles underlie certain tolerances which need to be identified and considered for a justified and reliable detection of high emitting vehicles. The combination of sensor information as well as predicted tailpipe emissions from ECU internal models and statistical data will be required to fulfill future OBM requirements.

The results of conducted hardware investigations and advanced Raw and Tailpipe emission modelling are key elements for a future realization of OBM.

Hydrogen-powered internal combustion engines (HICE) offer a longterm solution to ensure a more sustainable mobility service. NO_x-free combustion is not feasible since high combustion temperatures and lean operation result in nitrogen oxides formation, which can be reduced to a minimum by an intelligent controlled combustion process in lean operation and with exhaust gas recirculation. However, to comply with the Euro VII climate targets, the implementation of an aftertreatment system is required. The lean NO_x trap (LNT) is a well-known solution that provides an alternative for NO_x conversion in internal combustion engines other than the selective catalyst reduction (SCR) system. This solution can offer robustness and low operation complexity, optimizing the already low exhaust gas NO_x emissions. In this paper, an LNT installed on a HICE was experimentally investigated. The LNT loading behaviour, when submitted to the hydrogen engine exhaust gases, was demonstrated. The LNT operation was assessed, being the loading operation demonstrated and an overview of the regeneration process conducted. For regeneration, a rich lambda setpoint is necessary. The influence of the NO_x concentration and space velocity on the loading capacity was evaluated graphically. Regulated European cycles were conducted utilizing precise, energy-efficient, and compliant internally developed controls. After being freshly regenerated, the LNT provided a highly efficient operation, showing a NO_x conversion efficiency of over 80 %. Moreover, the potential of this exhaust aftertreatment solution was further confirmed by performing consecutive cycles. It was concluded that the LNT is a robust, suitable, and a promising approach for the deNO_x strategy, allowing hydrogen combustion engines to comply with current and future emission regulations.

Restrictive future CO₂ emission regulations are incentivizing evaluation of carbon-free fuels. This is particularly true in the difficult to electrify heavy commercial vehicle segment. The reemergence of hydrogen internal combustion (H₂ ICE) for large displacement engines can both expedite hydrogen adoption and reduce total cost of ownership. This paper will cover how the application of a SuperTurbo can address challenges unique to H₂ ICE. The research being presented is joint simulation conducted by AVL List GmbH and SuperTurbo Technologies on a 13L H₂ ICE. The GT Power model is calibrated from dyno testing at AVL of an operational engine and then modified with known and tested data from a mechanically variable SuperTurbo. The first H₂ ICE challenge that will be addressed is the requirement for the engine to maintain a lean-burn combustion strategy. Maintaining H₂ lean-burn is key to controlling NO_x formation and minimizing aftertreatment requirements. The high lambda requirement can create challenges for turbocharges when available turbine power is insufficient for the desired compressor power. The on-demand air functionality of the SuperTurbo negates this problem and can be used to optimize air-fuel ratio in steady-state and transient cycles. The simulation will show low NO_x formation through combustion optimization and time to torque transients equivalent to diesel. The second H₂ ICE challenge that will be addressed is how to maintain highest BMEP and BTE for hydrogen internal combustion engines with a SuperTurbo in order to close the gap to diesel and FCEV respectively. The availability of SuperTurbo enabled exhaust energy recovery through turbo-compounding, in combination with combustion optimization, will demonstrate an ability to improve H₂ ICE BMEP/BTE/BSFC

As carbon-free clean combustion has become crucial to help achieve the increasingly stringent climate targets, alternative fuels are gaining more interests in the technology sector of internal combustion engines. Hydrogen and ammonia are considered as promising zero-carbon fuels in addressing the decarbonisation challenges of the global mobility turnaround. The present study introduces the method of developing neural network models to predict the laminar flame speed (LFS) of ammonia and hydrogen mixtures. Representing the LFS in a neural network increases fidelity in predictive combustion simulation without a big penalty in calculation time. The original data-generation process, based on detailed chemistry calculation in a 1-D simulation tool, is also discussed. This illustrates a wide range of engine-like operating conditions and how the quality and quantity of the data sets influence the neural network model fidelity. A trendwise study on LFS varying as hydrogen fractions in the fuel (ranging from 0 vol% to 100 vol%) was carried out using the introduced methodology. Results show increasing laminar flame speeds as hydrogen fraction increases. The developed artificial neural network (ANN) model achieves acceptable quality with a coefficient of determination > 0.99.

Today, the world is witnessing an energy transition driven by climate change. At its essence, there is the need to develop zero or low CO₂ emissions solutions for the transport sector. In addition to electrified powertrains, the automotive community is focusing on the substitutes of hydrocarbon fuels to propel existing vehicles. Ammonia is such a potential fuel by virtue of its competitive cost, energy density and a well-established supply chain. The combustion of ammonia in preexisting internal combustion engines is quite challenging. Moreover, it is not well explored and understood in the automotive industry. The present study utilizes three-dimensional computational fluid dynamics (3D-CFD) as a tool, to deepen the understanding of a fully premixed ammonia/air combustion in a single cylinder engine equipped with a swirl driven flat cylinder head. Previously, three different piston geometries were evaluated on the test bench to investigate the sensitivity of piston design on premixed NH3-air combustion. In the present work, the combustion has been modelled for these three configurations using 3D-CFD simulations. First, the modelling has been validated against the experiments in terms of in-cylinder pressure and heat release rates. Then, the combustion characteristics of each configuration have been critically analyzed and explained by means of 3D visualisation. The analysis revealed that the combustion correlates quite well with in-cylinder flow dynamics generated by the different piston shapes. The key piston design parameters influencing the combustion process at different stages were identified and discussed. The turbulent kinetic energy (TKE) in the piston bowl and the reverse squish flow were found to govern the process in the beginning and late stage of combustion, respectively. Finally, piston design ideas were proposed to optimize the premixed ammonia combustion.

UNITI Bundesverband mittelständischer Mineralölunternehmen e. V. (UNITI federal association of medium-sized mineral oil companies) represents about 90 percent of the mineral oil companies in Germany and brings together expertise in fuels, the heating market and lubricants. Around 70 percent of independent petrol stations and about 40 percent of roadside petrol stations are members of UNITI. Every day, more than three million customers visit petrol stations run by UNITI member companies.

The automation of longitudinal vehicle dynamics is one of the major challenges of today’s automotive development and is of great importance for driver assistance systems and autonomous driving. In hybrid electric vehicles, this automation offers great potential for saving fuel due to the additional degree of freedom in the powertrain. To minimize fuel consumption, it is of central importance how to link the driving strategy and the operating strategy of the hybrid electric powertrain. A possible solution for this is offered by the multicriteria driving strategy planning presented in [1], which computes fuel-efficient speed trajectories for following other road users, where the planning is restarted after a certain distance (driving horizon). In addition to [1] the aim of the paper at hand is to quantify the fuel-saving potential of this speed trajectory planning with a study using real data of different route types (urban, extra-urban, combined, highway) and emission test cycles such as the WLTC. For this purpose, design of experiments was used to identify the parameters that have a decisive influence on the fuel-saving potential. The multi-criteria driving strategy planning is based on an algorithm that uses a parameter variation of the car-following model Intelligent Driver Model (IDM) to compute many possible speed trajectories to follow the driver ahead for a certain driving horizon. The most suitable trajectory is then selected by means of a cost function and the operating strategy is rescheduled with this trajectory. The operating strategy can be integrated into the algorithm in different ways: The operating strategy can be rescheduled only for the current driving horizon, or from the current position to the end of the trip – which is called the local, respectively global approach of rescheduling. Furthermore, the stochastic method of a Sequential Importance Resampling particle filtering algorithm can be used to determine the speed trajectory instead of simply considering all possible trajectories in a driving horizon, which greatly reduces computing time. To quantify the fuel-saving potential of the multi-criteria speed trajectory planning, it is investigated which of the two operating strategy integration approaches shows better fuel consumption results, which route type provides the highest fuelsaving potential and whether the use of the particle filtering algorithm has a negative effect on the fuel-saving potential. The fuel-saving potential is defined here as the reduction of fuel consumption by using the multi-criteria driving strategy planning when following another road user compared to the use of a car following model with static standard driving parameters as defined in [2]. To set up the study, the system understanding was first deepened by an algorithm analysis. Moreover, improvements in the parametrization of the cost function, the IDM and the particle filtering algorithm were made and a new standardized approach was created as a reference for the study. Results of the design of experiments identified the length of the driving horizon, the weighting of energy and time efficiency in the trajectory planning and the use of the particle filtering algorithm as the most influencing parameters for the fuel-saving potential. In summary, the results show that the use of multi-criteria driving strategy planning to plan speed trajectories for hybrid electric vehicles offers a general fuel-saving potential and that the maximum potential is 9,75 %. Furthermore, the global approach is 1,57 % more fuel efficient than the local approach of rescheduling the operating strategy. Overall, urban driving profiles showed the highest fuel-saving potential of all possible route types. The use of the particle filter algorithm reduces the fuelsaving potential by 0,89 % compared to the simulation with all trajectories, because it calculates only an approximate optimal speed trajectory with respect to the cost function. However, this stochastic method is currently the only way to achieve real-time capability for road use. Finally, the most profitable driving horizon was found to be 100 m in length for planning the speed trajectory. The paper concludes with a recommendation for the parameterization of the algorithm and further steps for implementation in a real vehicle.

The future renewal of bus fleets with the licensed public transport companies will be significantly affected by Switzerland’s 2050 energy strategy. The energy source, operation, maintenance and TCO will be completely different in the future and will make for a challenging replacement of an existing bus fleet.

A detailed feasibility study [1], funded by the Swiss Federal Office of Transport (FOT) and carried out in close collaboration with the Transports Publics Fribourgeois (TPF), evaluates the technical and economic feasibility of replacing the Diesel buses in the TPF fleet with buses equipped with a hydrogenpowered combustion engine (H2ICE).

An extensive measurement campaign on various bus lines of the TPF network was carried out and served as a basis for the simulations used to define the TCO of the future Hydrogen Bus with Internal Combustion Engine (H2BICE). In parallel, an engine base was identified in Fiat Powertrain Technologies (FPT) range to be converted to hydrogen combustion and a vehicle base was selected from the bus manufacturer HESS.

The conditions necessary for the integration of the various components required for the realisation of a bus equipped with an H2ICE were considered to verify the feasibility of the vehicle.

The work carried out has shown that the realisation of such a vehicle is possible both technically and in terms of safety, and that it is for extra-urban journeys economically very competitive compared to the CO2-neutral technologies known to date.

Over the past two decades, it has become clear what the consequences of climate change are and that short-term action is needed to stop further global warming. In consequence the EU Commission has staked out the framework for the transport sector with the Green Deal: CO₂ emissions are to be reduced by 30 percent by 2030 and climate neutrality is to be achieved by 2050. To help meet these targets and comply with fleet emissions regulations, a significant increase in energy efficiency and/or a move away from fossil fuels is required in the commercial vehicle sector. To this end, MAN has made the Battery Electric Vehicle (BEV) the focus of its development. MAN is simultaneously investigating hydrogen driven powertrain solutions as a possible complementary technology to BEV for specific applications. MAN is following two technology paths here – the hydrogen combustion engine and the HD fuel cell. This paper will concentrate on our MAN H45 HD truck engine, which, with a power range of up to 520 hp and a maximum torque of 2600 Nm, matches the performance level of a conventional diesel engine. Different measurements, both on engine test benches and on the road, show ultra-lowest pollutant emissions so that the requirements of a Zero Emissions Vehicle (ZEV) are met.

Transport is at the center of many economic and social development challenges, accounting for about 64% of the global oil consumption.

We are in the midst of a fundamental paradigm shift of how we power mobility. Mobility will be powered by a wide range of solutions, including electricity, hydrogen and renewable fuels. This paradigm shift is driven by an urgent need to reduce transport-related emissions, and only by combining all available solutions will we meet climate goals. The climate cannot wait.

Regulation is one of the keys to drive this shift, regulation has been successful in promoting battery electric and fuel cell vehicles but technology neutrality is still missing as well as a Well-to-Wheels or Life cycle approach, including that would also promote the usage of renewable fuels.

Availability of renewable fuels is essential, current solutions like HVO (Renewable Diesel) can still be scaled up significantly but there is an upper limit of how much feedstock is available, that why it’s also important to investigate future technologies in parallel. Solutions with high volume potential includes, Lignocellulosic residues (agriculture; forestry), Municipal solid waste and Power-toliquids.

Road transport is the largest user of renewable fuels, but other sectors are starting to make the shift also, the non-road sector that in many cases is hard to electrify shows a large interest as well as the aviation industry.

None of the alternatives available, e.g. electrification or renewable fuels will be sufficient alone, especially not according to the required schedule. Remaining to focus on a single solution would be a grave mistake. The necessary technical breakthroughs already exist or are, at least, very close. All we have to do is to create an operating environment and culture that allow us to make optimum use of technologies to combat climate change.

To minimize the CO₂ footprint of combustion engines, synthetic fuels provide a sustainable alternative to conventional fuels when produced with renewable energy and a suitable carbon source. Efficiency and exhaust gas characteristics are very important criteria in this context. In this paper research regarding synthetic fuels conducted at a single cylinder spark-ignition engine is represented. Thereby the geometry of inlet ports and piston were varied to achieve higher efficiency. The results show an increase in efficiency of up to 14%rel when utilizing the high knock resistance of the synthetic fuel with a compression ratio of 19 compared to gasoline with a compression ratio of 11. Furthermore, the efficiency breakdown showed that the adapted engine design is not able to meet the production setup in terms of combustion speed and combustion losses. Additional research with a refined engine geometry could lead to even further improvements.

The C₁-oxygenates methanol (MeOH), dimethyl carbonate (DMC) and methyl formate (MeFo) which, due to their absence of C-C bonds, show a significant decrease in particle emission during combustion, were investigated in the NAMOSYN project on long-term and decomposition stability. The tested systems were blends consisting of MeOH or DMC and MeFo in varying compositions to adjust the vapour pressure. To investigate potential decompositions of MeFo to MeOH and formic acid, caused by hydrolysis, long-term measurements with NMR spectroscopy were carried out. Here, the focus was on the blends C65F35 (DMC 65 V%, MeFo 35 V%), M86F14 (MeOH 86 V%, MeFo 14 V%) and M70F30 (MeOH 70 V%, MeFo 30 V%) including varying amounts of H₂O. It was proven that the water content has a significant influence on the decomposition of MeFo and the equilibrium concentration of formic acid. Furthermore, it was shown that the M86F14 blend is stable in the long term without additives up to a maximum H₂O amount of 2000 ppm. In addition, using the ILSB-setup [1] (ideal ionic liquid salt bridge), pH measurements were conducted in the above blends to establish a new method for the direct determination of formed formic acid. First promising results were accomplished even though a more precise measurement setup requires additional refinement.