Heavy-Duty-, On- und Off-Highway-Motoren 2022

The development of a hydrogen internal combustion engine (HICE) represents special challenges in combustion development. The HICE is being developed with external mixture formation and injection of hydrogen upstream of the intake valves. The paper presents simulation results to show the challenges for the hydrogen injection (H₂-injection) system to avoid backfire into the air tract. The achievable engine performance and emission behavior of the PFI-engine are significantly influenced by the turbocharging technology and its ability to rise charge pressure to necessary level. The maximum achievable engine power is optimized by simulating the complete system. The permissible operating conditions are respected to avoid overloading the components. In NRMM applications in particular, the high engine dynamics required (load step) must be considered. Experience in real-world applications enables the suitability of the HICE to be evaluated. It can also be used to evaluate the robustness of the engine concept. For this purpose, several demonstrator projects with different applications are being realized, which are also briefly presented in this paper.

Hydrogen internal combustion engine (H2-ICE) has the potenzial to be an enabler for fast decarbonization in several sectors. In this context, Liebherr is developing a hydrogen combustion engine based on spark ignition. This new powertrain is a part of a strategic approach toward zero emission technologies for off-highway sectors.

This technology has gained an important interest from the off-highway sector due to several reasons such as:

Currently, the diesel engine finds its way in a wide range of vehicles in the Off-highway sector and transformation of the current power train to the new zero emission technologies (Hydrogen Engine) will require considering several aspects:

The development of the technology started with several investigation in the combustion engine test bench; this new power train has been then introduced in vehicle integration and used to build-up a zero emission excavator.

This paper reviews the current investigations regarding the transformation/adaptation of an excavator powertrain (Diesel-hydraulic excavators) to a hydrogen combustion engine powered machine: Description of the excavator characteristics and analysis of the different characteristics of this new powertrain. Thenceforth, the fuel and storage system is explained and illustrated, followed by a review of several safety precaution aspect. The paper concludes with an evaluation of the new proposed powertrain in terms of dynamic, efficiency and emission. At the end an outlook regarding the further application of the hydrogen combustion engine in different other type of machines in construction and off-highway sector has been given.

This paper discusses the adaption of a single cylinder research engine for a retrofit application with an ammonia diesel dual-fuel combustion process and the build of an ammonia fuel system. The gaseous ammonia will be injected in the air intake pipe and the premixed ammonia air mixture will enter the combustion chamber. The diesel injection is carried out via a high-pressure common rail system. All relevant parameters can be freely adjusted via a freely programmable control unit. With the help of experimental data from a single cylinder research engine at the chair of piston machines and internal combustion engines of the University of Rostock (LKV), a dual-fuel combustion model based on detailed chemistry will be developed and optimized. This model will be integrated in a full research engine model, which ensures the best possible representation of the real engine. The combustion model is being developed by LOGE Deutschland GmbH. The full research engine model is developed by FVTR GmbH. The analysis of the combustion process starts with pure diesel operating points and is successively substituted by ammonia in the course of the measurement campaigns. Both the combustion characteristics are relevant, as they significantly influence the resulting performance and engine operation, as well as the exhaust emissions, as the carbon emissions can be reduced, but the nitrogen oxides and ammonia slip increase significantly in relevance due to the ammonia. The results obtained will be used to derive initial recommendations for action and to estimate the potential for application in the inland waterway shipping. In addition, the development of the systematic simulation tools covers a broad spectrum of research questions and aims to increase the efficiency of the necessary R&D.

For commercial vehicles, the hydrogen internal combustion engine (H2 ICE) is a propulsion variant that enables fast defossilisation in the HD vehicle segment. MAHLE is intensively investigating this kind of engines and develops components for this application. A research engine was built and operated with a combustion system with direct injection of hydrogen (H2 ICE DI) whereas experience is used from operating the same aggregate in port fuel injection configuration (H2 ICE PFI) in the preceding project. The results demonstrate the potentials of the DI combustion system in terms of engine load and efficiency. Furthermore, a direct comparison to the PFI combustion system is done. Boundary condition is the realization on a typical commercial vehicle engine and the use of components that were developed for a future series use of H2 ICE engines. MAHLE deducts important insight related to requirements for the components from these investigations and uses the opportunity to test further subsystems for this application, e.g. in the field of crank case ventilation.

Hydrogen-fuelled internal combustion engines (ICE) offer a zero-carbon fuel option for many ICE applications. As part of a global interest to characterise and study the behavior of hydrogen fuel in existing ICE applications Ricardo is collaborating with the University of Brighton to test hydrogen fuel in a Ricardo designed Proteus single cylinder engine. The engine is representative of a 13 litre Euro VI heavy duty (HD) production application converted to run on hydrogen fuel with minimal changes. The engine is fitted with a 35-bar direct injection (DI), hydrogen injector which gives improved flexibility for injection strategies and greatly reduces the presence of hydrogen in the intake system compared to a PFI system. Steady-state testing was carried out at an array of speed load points covering a large part of a typical heavy duty (HD) drive cycle area. An extract of the test results are shared and discussed in this paper. Lambda (λ) sweeps show the system is capable of running out to values exceeding λ = 5.0, exhaust gas recirculation (EGR) sweeps show over 40% EGR can be tolerated at given lambda conditions. Abnormal combustion events present sizeable challenges at lower lambdas due to very large knocking pressures and pre ignition risks. The lambda-threshold where the majority of these events are observed increases with speed and load thus narrowing the initial operating range of the engine prior to introducing mitigating measures like cooled EGR. The basic impact of lambda, EGR, injection and ignition timing sweeps are presented in this paper and show how the system responds to the corresponding changes in specific heat capacity, mixture preparation, and combustion phasing.

Currently the OEMs of commercial vehicles (using an internal combustion engine) are preparing for the new emission legislation EU-VII und EPA-27. The challenge is an improved NO_x-reduction at cold-start and low load conditions as well as reduced CO₂. In the meantime, also in the Off-Road sector (NRMM) the first discussions started on next steps. The existing exhaust aftertreatment systems are typically showing very high NO_x-conversion rates when operated at the appropriate temperature. OEMs are investigating a variety of possible solutions to increase the temperature level of the SCR catalysts for the critical operation points: cold start and low load. “Pure” electrical heating has quite a high CO₂-disadvantage in the case that the electrical power is coming from alternator and battery. The high power-demand for higher exhaust mass-flow is another challenge for the electrical system. Fuel dosing into the exhaust system is a state-of-the-art process for DPF regeneration and shows a high efficiency in energy release. Combining electrical heating with fuel dosing results in an efficient heating with moderate electrical power demand. “Engine-independent” heating of the exhaust system allows in turn the engine to operate in the “CO₂-bestpoint” and thus reduce the fuel consumption. The innovative compact catalytical heater as an add-on component upstream of a well proven CV-muffler allows to begin fuel dosing very early in the cold-start phase, generating high amount of energy for the fast heat-up of all components (including catalysts) within the muffler. It is also intended to operate for keeping the exhaust system warm in low load operation. The goal is to continue using already existing and well-established exhaust components (muffler) to reduce R&D efforts & tooling costs. This paper describes the development of the system including simulation as well as test results on a dynamic heavy-duty engine test bench resulting an improvement of 11%-points in the FTP cold start and in the Low Load Cycle (LLC) a NO_x conversion of 99% with active heating.

Liebherr develops hydrogen fuel injection system solutions to be used in on- and off-highway hydrogen combustions engines. Heavy-duty off-highway applications have partly different requirements compared to on-highway applications. Robustness against dust, dirt & vibrations and other harsh environmental conditions must be given. Additionally higher peak power demand and more dynamic load cycles increase the requirements on the transient performance of the engine. To meet these requirements, Liebherr has developed a complete hydrogen injection system that includes all the components needed for pressure regulation and fuel dosing. Throughout the development, real load cycles of heavy-duty mobile machinery have been considered to properly design the system and its components. This paper will provide detailed insights on the layout, design and functionality of the hydrogen injection system. In particular, the dynamic pressure regulation by means of a gas metering valve is shown and how this approach enables diesel-like transient engine behavior. Furthermore, first test results on the system performance are provided. Additionally an overview on the common platform approach to the Liebherr portfolio of hydrogen fuel injectors for port fuel injection (PFI) and direct injection (DI) incl. actual test results will be given. Liebherr’s approach to hydrogen fuel injection systems are not only limited to heavy duty commercial engines. Also components for large engines are considered in the overall platform approach.

Hydrogen dosing systems for large engines are available as low pressure gas admission valves in the intake manifold, as mid pressure port fuel or direct injection systems and high pressure dual fuel systems. Here the first three options are used to operate the engine in an Otto-cycle mode, where the last injection system allows a Diesel-like combustion process.

All four engine concepts have their validity in their individual application. Key aspects for choosing one of the combustion technologies are system and operating costs – strongly related to the tank and periphery technologies needed to provide a certain system pressure for the dosing system.

The pressure and power range as well as the functionality of all systems, operating conditions and limitations will be discussed. Main challenges in the development and the practical application on an engine are shown as well as the corresponding technical solutions.

Where available, combustion results will be shared to support the working hypothesis for the selection of individual concepts / systems. A final conclusion will indicate individual benefits and will give an outlook, which system has to be expected on which engine application in the field.

In order to achieve the globally agreed carbon dioxide reductions for a heavy-duty vehicle (HDV) several technologies are currently pursued, battery electrical vehicles (BEV), fuel cell electrical vehicles (FCEV), hydrogen-internal combustion engines (H₂-ICE) and e-fuels. The total cost of ownership (TCO) is a very important aspect in the transportation sector. The fuel cell electrical vehicle (FCEV) is a very interesting alternative powertrain technology especially for long haul applications. The hydrogen storage technology is a key success factor to achieve the overall TCO requirements. The paper describes the specific requirements and challenges for a hydrogen storage system in a HDV application and compares the three different hydrogen storage technologies, such as compressed gaseous hydrogen (CGH₂), liquid hydrogen (LH₂) and cryo-compressed hydrogen (CcH₂).

Im Zusammenhang mit dem Ziel der Europäischen Kommission bis 2030 die CO₂-Emissionen um 55 % zu senken, ist besonders der Verkehrssektor gefordert alternative Antriebsysteme für unterschiedlichste Anwendungen zu entwickeln.

Der Fokus dieser Arbeit liegt dabei auf der Untersuchung unterschiedlicher Antriebssysteme in der Nutzfahrzeuganwendung. Neben dem Standard Dieselantrieb werden die Well-to-Wheel CO₂-Emissionen eines Erdgasfahrzeugs, eines batterieelektrischen Fahrzeugs und eines Wasserstoffverbrenners in verschiedenen Anwendungsfällen untersucht. Die Lastprofile erstrecken sich von dem hochspezifischen Müllsammelbetrieb bis hin zur Warenlieferung auf der Langstrecke. Dabei spielen die Zuladung und die Topographie ebenfalls eine wichtige Rolle.

Methodologisch erfolgen die Untersuchungen aller Fahrszenarien nach folgendem Schema. Eine im realen Fahrzeug aufgenommene Strecke wird in die Virtuelle IPG-Truckmaker Umgebung überführt. Anschließend wird das Modell des realen Referenzfahrzeugs erstellt und die erzeugte Simulationsumgebung wird anhand des Vergleichs von realen und simulierten Kraftstoffverbräuchen validiert. Das validierte Referenzfahrzeug dient von nun an als Basis für den Aufbau der Nutzfahrzeuge mit alternativen Antrieben. In diesem Zusammenhang können die Verbräuche der unterschiedlichen Antriebssysteme in den ausgewählten Anwendungen verglichen werden. Zusammen mit den ermittelten Well-to-Wheel Emissionen der betrachteten Energiespeicher erfolgt schließlich die Bewertung des Anwendungsspezifischen CO₂-Impakts der einzelnen Antriebssysteme.

Das Ergebnis dieses Vergleichs ist neben der variierbaren Simulation durch veränderte Randbedingungen oder Streckenprofile auch die Beantwortung der für Logistikunternehmen aller Art relevanten Frage des ökologischen Optimums. Sie dient im hierbei spezifischen Fall als Orientierungshilfe, um bei einer möglichen Flottenanpassung den ökologischen Aspekt stärker zu berücksichtigen.

The global drive to increase the use of renewable energy requires new approaches for energy storage and transportation to be developed. Blending hydrogen into the existing natural gas pipeline network is one strategy to store surplus electric energy in the form of green hydrogen. This strategy is currently being seriously considered in both the US and Europe.

The INNIO approach is to enable INNIO’s entire Jenbacher product line for power generation to run on pipeline gas – hydrogen mixtures, with the permitted hydrogen content allowed to fluctuate between 0 and 25% vol. The challenges for engine development are as follows: The solution must enable operation with varying hydrogen contents and be applicable to the entire pipeline gas product program. Engine parameters like NOx, peak firing pressure, power control reserve, combustion knock margin, and turbocharger surge margin must stay within defined limits. Critical events like mega knock at high BMEP (engine damage) and autoignition during fault ride though events (grid code non-compliance) must be avoided.

The selected strategy involves the measurement of the hydrogen content in natural gas and the pre-definition of various engine operating parameters. The final concept consists of a hardware/software package that includes additional sensors as well as hydrogen compensation software. Gas train size/version and fuel metering size/version must be checked and adapted to each individual engine if required.

The development project ran over two years and included hydrogen sensor selection and validation, component certification, controls strategy development, and single and multi-cylinder engine testing. The testing was carried out with defined mixtures of natural gas, propane, and hydrogen on various Jenbacher engines from INNIO platforms and included steady-state and transient operation. The final solution is retrofittable.

INNIO’s Jenbacher engines are now ready for hydrogen ad-mixed in the gas pipeline. The applied technical concept offers robust power plant operation at best performance. Any potenzial customer demands with hydrogen in natural gas contents above 25% (up to 100%) also can be handled but will require further engine hardware and software packages affecting pure natural gas operation.

Hydrogen-based powertrains are hopeful prospects in the development of climate-friendly transport systems of the future. Testing in a safe way is absolutely essential for the development and testing of hydrogen-based powertrains.

Our attention is to ensure sustainable testing.

Green hydrogen and green electricity, as well as feeding them back into the power grid, are important elements in the issue of sustainability. The production of green hydrogen through electrolysis is a goal we will achieve in 2024.

Safety is a priority issue, when testing with hydrogen. This is in our interest, but also in the interest of all our customers. A comprehensive safety package for the operation of hydrogen powertrains serves as a basis for this. This includes hazard assessment, fire and explosion protection documents, as well as a safety strategy.

The results of the risk assessment are the cornerstone for the safety concept.

The risk assessment reveals the hazards that can occur during hydrogen testing. With the help of various countermeasures, the probability of occurrence or risks of these events can be reduced.

These countermeasures have been worked out for a wide range of scenarios and include requirements for sensors, redundancies, as well as room air exchange rates and line evacuations.

The entire spectrum was then summarized in the safety strategy and is being implemented for all hydrogen test benches. This strategy relates to the test bench side. Special walls, explosion protection documents and ram protection are also installed for trailer stations in order to the safety of the hydrogen suplly process.

PEM fuel cell drivetrains in heavy duty applications are mostly implemented using multiple fuel cell systems and as battery hybrid systems. The complex architecture of those hybrid system results in various degrees of freedom in the operating strategy. Those have a major influence on aspects such as dynamics, efficiency and lifetime of the entire system. In order to be able to analyze and evaluate the capability of an efficiency optimized operating strategies, the ZBT fuel cell model is integrated into a fuel cell system and a full vehicle simulation. The dimensioning and also the load profiles are inspired by the Hyundai XCIENT Fuel Cell with 20 t total permitted mass. Starting from a rudimentary and purely functional operating strategy, an efficiency optimized operating strategy is presented. A mere optimization of the fuel cell system operation is not sufficient, since the losses in the battery system must also be considered. The numerous effects of the operating strategy are described.

Fuel Cell propulsion systems offer high energy density and short refueling times. These are the key facts for their application to heavy-duty vehicles. In the fuel cell propulsion system the layout of the fuel cell system itself is crucial. Based on the requirements like lifetime – and efficiency targets as well as package boundary conditions the components in the fuel cell system like stack and the so called BoP (Balance of plant) components such as compressor, hydrogen gas injector and humidifier are defined. Besides this the high temperature – and low temperature circuits and the high voltage system with DCDC’s and bleeding resistor are specified.

The paper describes the fundamental aspects and processes for defining the layout of a fuel cell system with all its subcomponents. Starting with 1D simulation the BoP components and their interactions are optimized for overall high system efficiency and performances. The system packaging ensures the integration in the heavy-duty vehicle and the connection to the vehicle air intake – and hydrogen storage system, high voltage architecture and thermal management. The software of the fuel cell system adjusts the system actuators based on the targeted fuel cell system state like idle, nominal power, peak power and transient operation. Finally, the system is tested on the fuel cell test bench.