Automotive and Engine Technology最新文献

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.

Dual-fuel combustion is a well-known measure to enable the combustion of low-reactivity fuels (LRF) in compression-ignited engines with high thermal efficiency through a pilot injection of a high-reactivity fuel (HRF). In most cases, the LRF is introduced into the intake manifold and therefore premixed with the air before entering the combustion chamber during the intake stroke (premixed charge operation, PCO). In this work, this approach is investigated for bioethanol-diesel dual-fuel combustion using external and internal exhaust gas recirculation (EGR) to improve emissions and engine efficiency. In addition, PCO is compared to an alternative concept in which bioethanol and diesel are blended shortly upstream of the high-pressure pump (premixed fuel operation, PFO) at variable mixing ratios. The results show that higher ethanol shares of up to 70% can be achieved at low engine load when using PCO, while at medium and high load, the maximum energy share of ethanol is higher with PFO. While PCO is limited by engine knock, PFO rather suffers from the reduction in cetane number. In PCO, external and internal EGR allow for a reduction of unburned hydrocarbons (up to − 82%) and carbon monoxide (up to -60%), while nitrous oxide emissions are simultaneously lowered by up to − 65%. Both with and without EGR, PFO shows low emissions of unburned hydrocarbons and carbon monoxide (similar to conventional diesel combustion) and a significant reduction in nitrous oxide and soot formation. Brake thermal efficiency (BTE) drops in both modes compared to conventional diesel combustion, in PCO operation due to unburned and partially unburned fuel and in PFO due to increased friction in the high-pressure fuel pump caused by an increased fuel flow.

This work deals with the influence of the variation of the air–fuel-ratio on the emissions as well as on the soot reactivity of a commercial vehicle diesel engine. The emissions and the associated soot reactivity are compared between conventional fossil diesel fuel and the regeneratively produced paraffinic diesel fuel HVO (hydrotreated vegetable oils). All investigations were carried out on a single-cylinder engine and the gaseous and particulate emissions were recorded. Additionally, the collected engine out soot samples were analyzed by thermogravimetric balance (thermogravimetric analysis = TGA) to determine the reactivity of the soot. Regardless of the set engine operating point, it was shown that the particulate mass is significantly reduced when operating with HVO compared to fossil diesel fuel. Other gaseous emissions are also minimally lower compared to fossil diesel. In contrast, however, the HVO fuel has an increased number of particles due to smaller particles. The variation of the engine operating parameters showed the same tendencies with regard to soot reactivity, regardless of the fuel used. However, the parameter variations were more or less pronounced depending on the respective fuel. It is particularly noticeable that the reactivity of soot, which is produced when using HVO, is reduced at every operating point despite the lower particulate mass compared to fossil diesel fuel.

In automated vehicles, environment perception is performed by various sensor types, such as cameras, radars, lidars, and ultrasonics. Simulation models of these sensors, as required in virtual validation methods, are available in various degrees of detail. However, proving the validity of such models is a subject of research. New metrics and methods for credibility assessment of simulation are needed to standardize the validation process in the future. The so-called double validation metric (DVM) has shown advantages and allows an intuitive interpretability of the validation results. The DVM has so far only been applied to lidar sensor models. In this paper, an extension to the DVM is introduced, which is called the DVM Map. A static measurement scenario is conducted in reality and transferred into simulation. The novel method is demonstrated on the obtained real and simulated radar sensor data. In this simple scenario special focus is put on the position accuracy of GNSS reference sensors. Therefore, their impact on the result of sensor model validation is discussed. The paper shows that the method provides a more detailed and accurate validation in comparison to the state of the art of a radar simulation, revealing previously undetected simulation errors. Errors due to the environment model, signal propagation, and signal processing are separated and satellite imagery is used for intuitive visualization of the results. This method is a complementary tool to existing validation techniques to improve the interpretability and judging the trustworthiness of radar simulations.

The Institute of Vehicle Systems Engineering at Ulm University of Applied Sciences is currently developing the autonomous concept vehicle Nimbulus-e in the strategic field “Intelligent Commercial Vehicles” with the aim of maneuvering as agilely as possible in confined spaces. To achieve high agility under the conditions mentioned, large road wheel steering angles are necessary. As part of the basic vehicle concept, the first step is to select a suitable chassis for this purpose. Conventional suspensions cannot be applied due to the mechanical connection of the tie rod to the steering knuckle limiting the road wheel angles. Therefore, the approaches published so far for individual chassis concepts with large steering angles are analyzed and evaluated for use. In this paper, the concept of a novel individually steerable five-link suspension is described. The concept includes a vehicle body mounted steering actuator connected to the chassis via a self-locking worm gear. Due to the body mounted connection of the steering actuator, it does not contribute to the unsprung mass. An analysis of the kinematic and elastokinematic properties and the achievable road wheel steering angle is presented. In the Nimbulus e concept vehicle, the individually steerable corner module is used on both the front and the rear axle. The system is driven by four wheel hub motors. This means that eight control variables are available for the vehicle.

Continuously increasing country-specific emission standards for passenger vehicles demand additional development steps in complex exhaust gas aftertreatment systems for a more effective reduction of harmful gases. The efficiency of the aftertreatment system declines over its lifecycle due to specific load profiles and other boundary conditions, resulting in increasing emissions over vehicle mileage. As a result, the durability of the exhaust system becomes more important. Fuel cut is an intended, temporary interruption of the fuel supply of modern combustion engines of passenger cars to reduce fuel consumption and emissions. During this fuel reduction event, unconsumed oxygen of rich and cool fresh air is introduced to the combustion chamber and to the exhaust system. Besides a catalyst cool down, oxidation effects are provoked by enhanced oxygen reactions processes within the catalyst’s washcoat and surface layers. In this publication, specific aging cycles with a variation of fuel-cut programs were examined on their effects on a modified modern eight-cylinder turbo-charged engine, especially on their oxidation effects correlating to catalyst aging. Light-off curves and conversion heat maps were used to evaluate possible damaging impacts of fuel-cut events on the aging behavior of the catalyst systems. Results indicate that higher frequency of fuel-cut events results in a reduced catalyst conversion efficiency, whereas thermal sintering might be reduced due to overall lower temperature load. Temporary oxidation processes on catalyst’s surfaces occur only in a short timespan after changing the air fuel ratio to lean, resulting in a weaker thermal sintering during longer fuel-cut events. Sound optimized torque reduction functions, used in sports cars for a better drivability and powertrain response, exhibit a stronger aging influence due to additional thermal shock effects on the catalysts front face, as demonstrated via optical infrared sensor technology during catalyst aging cycles on the modified engine bench setup. A theoretical calculation of aging processes as a combination of thermal sintering by Arrhenius equation as well as oxidation process is discussed to describe an aging classification induced via oxidation processes. Additional physisorption measurements of different catalyst probes support the results which indicate the direction of future experimental approaches.

To counteract the anticipated consequences of climate change, significant efforts are required across all industries. The use of hydrogen in internal combustion engines can make a valuable contribution as a carbon-neutral bridging technology. One challenge in developing a suitable combustion process is the high ignition propensity of hydrogen, impacting combustion stability due to combustion anomalies. Avoiding such combustion phenomena is of utmost relevance to ensure a long-term stable engine operation. Oil entry into the combustion chamber can impact the occurrence of combustion anomalies. Therefore, a specific method for controlled oil entry into the combustion chamber has been developed, and this method is detailed in the following article.

For an efficient reduction of methane slip, a precise understanding of exhaust gas after treatment under real conditions is essential. Since it is not possible to produce catalytic converters in near-series geometry on a laboratory scale, it is necessary to resort to significantly smaller sample catalysts. Therefore, an engine test bench was designed to ensure real operating conditions for such samples with the help of space velocity and temperature control. A comparison between the actual and reference values of the space velocity results in a small deviation of 0.1% on average. Furthermore, the pressure conditions at the catalyst have been measured showing a propagation of pressure oscillations from the engine outlet which in combination with the space velocity regulation show that real conditions could be applied to the catalyst sample. Subsequently, the exhaust gas concentrations were monitored with a Fourier transform infrared spectrometer. The catalyst material used is PdO on Al₂O₃, common for methane oxidation. The measurements show that the CH₄ conversion is higher under lean conditions, but is below complete conversion. In a final comparison between purely stoichiometric operation and dithering, the course of the CH₄ conversion rate over the test period is examined more closely. In addition to sampling pre- and post-catalyst, the exhaust gas composition is measured spatially resolved within a catalyst channel using special measurement technology. In the temporal course of the CH₄ emissions, a stabilizing effect due to the change of the operating mode can be seen, showing that dithering seems to prevent further deactivation.

Synthetic fuels from a renewable base are an essential part of a greenhouse gas-neutral mobility, especially in transport sector. While scaling production of e-fuels (fuels based on electrolysis hydrogen) is ongoing, HVO called paraffinic diesel fuels are already available. Their production is based on the hydrogenation of waste and residues and they are established as diesel substitute in several applications. With regard to the approval of these fuels in German regulation, the question repeatedly arises as to whether they can be used easily and what effects can be achieved. This article describes an application in a real logistics application, in which both the everyday use and the concrete comparability to a refueling with conventional gas station diesel were ensured. The use of several parallel active and different truck pairs has shown that the use of HVO in existing vehicles has achieved the desired CO₂ reduction. A detailed analysis of the engine oil also showed that no undesirable effects could be observed here either. From the perspective of this project, HVO fuels are ready for use for a significant greenhouse gas reduction in logistics.

The objective of the current study is to investigate the effect of tunable valve timings on the performance and emissions of a dual-fuel marine engine. A simulation model was developed in MATLAB to simulate the valvetrain mechanism. The model generates different valve lift curves depending on the input conditions, and after that, it tests them against any possible collision with the piston. The valid valve lift curves were exported to a two-zone combustion model in AVL CRUISE-M platform. The combustion model depends on the fractal principle and aims to predict the in-cylinder parameters. In addition, it contains sub-models to calculate the ignition delay and emissions formation. Model results were compared against experimental data, as the latter were obtained from a heavy-duty, medium-speed, single-cylinder research engine, which employs natural gas as a main fuel. The results showed good agreement and the model was used for further investigations with other cam pairs. It has been found that the fractal combustion model can effectively represent the combustion behavior in the dual-fuel engine. Furthermore, valve timing has a significant influence on the engine performance and exhaust emissions. Results also revealed that applying Miller cycle can reduce the nitrogen oxides emissions, while the higher valve overlap period had a negative effect on methane slip.