Automotive and Engine Technology最新文献

Heavy-duty fuel cell trucks are a promising approach to reduce the CO₂ emissions of logistic fleets. Due to their higher powertrain energy density in comparison to battery-electric trucks, they are especially suited for long-haul applications while transporting high payloads. Despite these great advantages, the fleet integration of such vehicles is made difficult due to high costs and limited performance in thermally critical environmental conditions. These challenges are addressed in the European Union (EU) funded project ESCALATE, which aims to demonstrate high-efficiency zero-emission heavy-duty vehicle (zHDV) powertrains that provide a range of 800 km without refueling or recharging. Powertrain components and their corresponding thermal components account for a large part of the production costs. For vehicle users, higher costs are only acceptable if a significantly higher benefit can be achieved. Therefore, it is important to size these components for the actual vehicle mission to avoid oversizing. In this paper, an optimization method, which determines the optimum component sizes for a given mission scenario under consideration of multiple criteria (e.g. costs, performance, and range), is presented.

Green methanol is a renewable fuel with many advantages when used in a spark ignition combustion process. Methanol has a comparatively high enthalpy of vaporization, leading to lower combustion temperatures (compared to gasoline combustion) and, hence, lower wall heat losses as well as a reduced tendency to pre-ignition. Therefore, a brake efficiency of more than 40% and, furthermore, minimal emissions are possible. The serial combination of a combustion engine with an electric powertrain provides a disconnection of the load demand of the powertrain and the operating point of the combustion engine. In this case, a high volumetric and gravimetric power density, easy energy storage, and a very cost effective already existing infrastructure of fuel distribution is combined with electric driving, high efficiencies, minimal emissions and a closed carbon cycle for the energy provision. Nevertheless, the high flash point of methanol at 11 °C indicates a challenging cold start. Heating the fuel or intake air or blending lightly boiling components are feasible solutions, but are related to additional expenses regarding packaging and cost. The described procedure enables the cold start of pure methanol down to −20 °C, without the necessity for additional engine components, when using a serial hybrid propulsion system. Besides, a serial hybrid powertrain offers the possibility of preheating the exhaust aftertreatment in addition to a reliable methanol cold start, while the vehicle is already running on its electric power train.

This study investigates nitrogen oxide emissions (NO(_x)) in a heavy-duty hydrogen engine by comparing Port Fuel Injection (PFI) with two Direct Injection (DI) configurations under various load conditions. A fast chemiluminescence detector (CLD) enables cycle-resolved nitrogen monoxide emission (NO) measurements, providing detailed insights into the emission characteristics of each injection strategy. The findings reveal that the PFI configuration consistently results in the lowest NO(_x) emissions due to superior air–fuel mixture homogenization. Additionally, it exhibits minimal cycle-to-cycle variations in both pressure traces and NO emissions. The indicated efficiency of the PFI setup is also higher compared to DI, likely due to the higher charge air pressures required to maintain a constant air–fuel ratio and reduced wall-heat losses. Conversely, the DI configurations, especially the 4-hole cap design, produce significantly higher NO(_x) emissions and show considerable variability between cycles. A strong exponential correlation between NO emissions and peak cylinder pressure (p(_{max})), which directly influences in-cylinder temperature, is observed across all configurations. The DI setups exhibit faster combustion, driven by increased turbulent kinetic energy from the hydrogen jet, leading to higher in-cylinder pressures and temperatures. This rapid combustion process complicates emission control by increasing NO(_x) formation. Despite similar combustion behavior and efficiency between the 1-hole and 4-hole DI setups, the latter generates much higher NO(_x) emissions, highlighting the crucial role of mixture homogenization. Cycle-based analysis further indicates that DI configurations, particularly the 4-hole cap design, experience single-cycle NO emissions spikes, making consistent emission control more challenging. While PFI presents clear advantages in emission reduction and efficiency, DI setups provide comparable power output with lower charge air pressure requirements. However, challenges in mixture formation must be addressed to optimize DI strategies for hydrogen engines. Overall, the study underscores the significance of optimizing mixture formation to mitigate NO(_x) emissions in hydrogen engines.

Sustainability strategies and lightweight construction measures are central to current and future product development processes. In the best case, creating a direct dependency between both is possible. In the project, “RePro AMC” components of a vehicle damper are specifically substituted and replaced with aluminum matrix composite (AMC). In this scenario, silicon carbide is used as a reinforcing component with a proportion of up to 15 percent by volume. The advantage here is not only the lower mass of aluminum over steel but also the fact that AMC can also be produced from so-called secondary aluminum (recycled aluminum). The following section reports on the realization of the AMC components and their significance for vehicle dynamics. A twin-tube damper is installed on the rear axle of an SUV, serving as a demonstrator.

The combustion anomaly of pre-ignition presents a particular challenge, especially in downsized engines. The interaction between the injected fuel and the oil-wetted cylinder wall plays a central role in the formation of reactive deposits, which are suspected of promoting pre-ignition. This paper investigates the influence of different tribological cylinder surfaces on this interaction. Plates with different surface properties are used and analysed using laser-induced fluorescence and optical measurements. The results will help to understand how surface properties influence the fuel-oil interaction and thus the probability of pre-ignition.

In this work, the ride quality of the novel multi-link torsion axle (MLTA) was experimentally evaluated. The kinematic topology of this suspension concept is designed to maximise the coherent package space in the underbody of small- to medium-sized battery electric vehicles (BEVs) to offer an increased installation space for the traction battery. Because of this suspension design, several compromises concerning longitudinal and vertical behaviour dynamics must be made. This work transfers the relevant kinematic and compliance characteristics on the suspension level to the full-vehicle ride comfort. Therefore, a full vehicle equipped with the novel MLTA as well as a conventional twist-beam axle (TBA) was tested on different uneven roads and single obstacles. As a result, the level of discomfort on the driver and on the chassis was assessed according to the international standards and best practices established in the literature. It was found that in its current state, the vehicle variant with MLTA has a higher level of discomfort in the vertical direction than the variant with TBA. However, the difference is in a tuneable range. Also, it was found that the MTLA offers a significant improvement for longitudinal chassis acceleration when driving over cleat-type obstacles.

Air-spring-dampers offer a novel alternative to traditional hydraulic damping within suspension systems. However, due to the intricate damping behavior and a multitude of configuration possibilities, the design process of air-spring-dampers proves to be challenging. This paper proposes a solution to address these challenges by introducing a simulation framework integrated with parameter optimization, enabling the simulation and design of any air-spring-damper. The simulation framework incorporates three fundamental modules: volume, mass exchange, and heat exchange. By abstracting the air-spring-damper as a graph and representing it via adjacency matrices, these modules will automatically be connected to construct a simulation model for any air-spring-damper configuration. Furthermore, leveraging the framework simplifies the design process through a parameter optimization. This method allows for a target damping curve to be set. The optimization algorithm then adjusts the air-spring-damper's design parameters until the target curve is achieved. A comparison of algorithms is conducted to determine the most suitable for this optimization problem. The pattern search and surrogate algorithms emerge as strong performers, effectively producing the target damping curve. To simplify the design process further, the common objective of enhancing driving safety and comfort is transformed into an optimization problem within the framework. This leads to the generation of a Pareto front, which presents design recommendations that balance safety and comfort optimally.

Internal combustion engines are a significant contributor to global CO₂ emissions. Sustainable fuels are seen as having great potential to significantly reduce these emissions. Hydrogen has the potential to significantly reduce local emissions. It can also be injected directly into the combustion chamber, where the resulting jet interacts with the cylinder wall and can influence the engine process. To be able to quantify this influence, fuel impingement has been investigated in this work. As fluids with different states of aggregation interact with each other in this process, a special measurement technique has to be applied. The gaseous fuel is visualised using a background oriented schlieren technique. The liquid phase of the oil is visualised using laser induced fluorescence. Using this technique, it was observed that the impact of a gaseous jet can deform a thin oil film and that isolated detachment effects can be observed.

The exact investigation of the thermal management of battery electric vehicles requires the precise simulation of the processes inside the cell. However, there is a broad trade-off between the complexity and manageability of the simulative methodology on the one hand and the necessary spatial accuracy of the simulation result on the other, which is why complex models that describe the cell down to local current densities and diffusion processes are not suitable for this overriding purpose. An equivalent circuit model proves to be the most suitable for the desired objectives. This model reproduces the electrochemical processes by means of an equivalent circuit and simulates the thermal processes through the cell layers to the surface by means of a thermal network model. Such an approach was pursued in the previous work, using various literature references and empirically obtained parameters (Lorbeck and Fruehwirth in Autom Engine Technol 10:2 https://doi.org/10.1007/s41104-024-00146-2, 2025). This approach proved to be pragmatic, but it quickly became clear that a more precise method to parameterize the equivalent circuit diagram was required for this specific application. The improved parametrization includes the measurement of several cells in terms of electrochemical impedance spectroscopy and open-circuit voltage, which are carried out and processed on site. This method makes it possible to achieve an adapted parametrization relatively quickly by measuring other cells. After carrying out these measurements and integrating the new parameters into the simulation methodology, a validation against measured cells and against the previously used simulation methodology (literature-based, partly empirically determined parameters) could be carried out. Despite the additional effort involved in measuring the cells, the validation speaks in favor of introducing the new simulation methodology, as the accuracy of the predictions and in particular the simulation of transient parts within the cycles has improved. This means that in future, it will be possible to better illuminate and understand various areas of thermal and electrical cell stress that are of interest for the observations. A further validation, which compares different real driving measurements and testbed cycles on cell level with the according simulation data, is planned for 2025 and is currently being analyzed as part of ongoing investigations.

Battery tests require a high degree of safety-related preparation and constant monitoring of the operating parameters to guarantee the smooth running of tests without incidents or exceptional events such as a thermal runaway. As the handling before, during, and especially after the tests is relatively complex and sometimes just as costly, it is important to reduce these risks and costs as well as to find an alternative to conventional battery tests. Such an approach is being developed by the T-cell project of the Institute of Thermodynamics and Sustainable Propulsion Systems at Graz University of Technology, founded by the Austrian Research Promotion Agency (FFG). A thermal substitution cell, which resembles a battery cell on the outside, is to reflect the surface temperature distribution of a chemical cell without there being any cell chemistry inside the substitution cell. Rather, the interior should not be part of the observation and the thermal requirements should be provided by an internal heating option. Such a measurement approach requires, among other things, a control and regulation unit, without which it would not be possible to transfer the thermal behavior of a battery cell to the substitution cell. Together with the electronic structure of the substitution cell and a circuit environment including a battery simulation model established at a later date, this control/regulation module forms an overall package that considerably facilitates investigations at cell, module, and pack level by substitution of a certain amount of cells using system symmetry advantages. A suitable simulation model was constructed and parameterized for this purpose from an electrochemical and a thermal network. As a first step, the data, which were partly determined empirically but also derived from real cell measurements in the literature, were adapted to the requirements of the simulation environment, so that the real cell used could be simulated thermally in principle. The simulation observations represent the state of the art of the model and are continuously improved by measurements carried out at the institute, thus building up the overall system in more detail.