Automotive and Engine Technology最新文献

An efficient thermal management in vehicles can reduce fuel consumption or improve the electrical range. Optimized control strategies adapting to various load cases can reduce the energy consumption of the cooling system and keep components in efficient operating temperature ranges. Current cooling control strategies use performance maps or rules, which are time- and cost-consuming to develop due to a high manual workload and the necessity of vehicle prototypes. In this paper, a highly automatized process is proposed to create control strategies with machine learning methods and simulation models. A new tool is introduced, which can couple Python code with Dymola to extend simulation models by calibration and optimization features. Simplified control models are created with the dataset of optimized control settings using machine learning implementations for a multivariant linear and polynomial regression as well as a decision tree and a random forest classification. The performance of the different control models is compared on a dynamic drive cycle in a co-simulation.

Proton exchange membrane (PEM) fuel cell vehicles require an electrical intermediate storage system to compensate for dynamic load requirements. That storage system uses a battery and has the task to increase tolerance to dynamic operation. In addition, energy can be recuperated and stored in supercapacitors to increase the fuel cell vehicle’s efficiency. To determine the optimal battery capacity according to the recuperation potential and possible use of a supercapacitor, a reference vehicle with PEM fuel cell was transferred to the simulation environment Matlab/Simulink. The model is based on a cell model describing the electrochemical and physical interactions within the cell. It has been implemented in a complete vehicle model for the representation of a fuel cell vehicle. Various legal driving cycles, such as the WLTP (“Worldwide harmonized Light Vehicles Test Procedure”), were used for the calculations. A further step sets the optimal battery capacity depending on the dynamic of the fuel cell system. With this simulation model, dynamic requirements—for the fuel cell and the associated system components—can be determined in the future, scalable for each vehicle depending on the battery capacity and recuperation potential.

A vaporizer is a key component in a liquified natural gas (LNG) engine, whose heat dissipation capacity determines the reliability of LNG engines. In the present study, the heat dissipation performance of LNG vaporizers is investigated using numerical simulation by a thermal-solid coupling method. Simulation results were first compared with experimental data to validate the thermal-solid coupling method and a good agreement between the numerical and experimental results was achieved. The experimentally validated numerical method was then used to predict the heat dissipation performance of the LNG vaporizers. The simulation results show that the temperature of the vaporized natural gas at the outlet of the vaporizer is quite uniform, which is about 40 °C and high enough for the vaporizer to provide a stable gas supply to the LNG engine. A unique design of the vaporizer’s coolant inlet can take advantage of coolant flows to enhance heat transfer in the engine cooling process, thereby promoting the heat exchange within the engine and increasing the heat exchange capacity of the LNG vaporizer.

Cast engine components are experiencing ever tighter tolerance requirements and at the same time a more complex cast design. The geometries, some of which are inaccessible, are tested for quality assurance on the basis of relevant component characteristics, among other things. The position check measures the actual position of a feature in a spatial dimension. Information about the alignment and geometry of the combustion chamber cannot be derived from the measurement methods applied. The use of three-dimensional measuring methods, e.g., imaging by computer tomography, can additionally record the spatial component position and the component geometry. Further measurement data can be derived from this, which serves to increase process reliability and component quality, and to increase component quality within an entire component batch. On the one hand, the cylinder head limits the working space by the roof of the combustion chamber, on the other hand, the cylinder head has a significant influence on the charge movement, especially at the beginning of the intake flow, due to the geometry of the intake ducts. On account the high demands of modern gasoline engines with tumble combustion process paired with Miller operation at partial load, variable timing, etc., mixture formation is important for efficient operation. Mixture formation in air- and wall-guided combustion processes depends on the components air duct and injection. From the point of view of cylinder head production, the mixture formation component air guiding is an elementary development approach for implementing efficient and sustainable component production while ensuring component properties. From this, the question can be derived as to what influence, for example, different dimensional tolerances in the combustion chamber size have on engine operation. To address this question, 3D simulations and physical test bench measurements were performed. With a variation of the above-mentioned intake duct and combustion chamber geometries and due to manufacturing tolerances, simulation results and measurement data were evaluated, analysed and presented in this paper. The influence of manufacturing-relevant tolerance deviations in the early process step of cylinder head production on combustion engine operation can be recognised in different ways.

This paper describes the CO₂ emissions of the additional electricity generation needed in Germany for battery electric vehicles. Different scenarios drawn up by the transmission system operators in past and for future years for expansion of the energy sources of electricity generation in Germany are considered. From these expansion scenarios, hourly resolved real-time simulations of the different years are created. Based on the calculations, it can be shown that even in 2035, the carbon footprint of a battery electric vehicle at a consumption of 22.5 kWh/100 km including losses and provision will be around 100 g CO₂/km. Furthermore, it is shown why the often-mentioned German energy mix is not suitable for calculating the emissions of a battery electric vehicle fleet. Since the carbon footprint of a BEV improves significantly over the years due to the progressive expansion of renewable-energy sources, a comparison is drawn at the end of this work between a BEV (29.8 tons of CO₂), a conventional diesel vehicle (34.4 tons of CO₂), and a diesel vehicle with R33 fuel (25.8 tons of CO₂) over the entire useful life.

Real urban driving conditions challenge exhaust gas aftertreatment systems for diesel passenger cars. One promising approach is the transfer of the selective catalytic reduction to a pre-turbocharger position, resulting in a thermal adjustment of the boundary conditions for the system. The design and functional behaviour of two new pre-turbo concepts are discussed. Challenges arise when the dosing of a urea–water solution and thermal mass are integrated upstream of the turbocharger. The design and results of these new concepts are presented using an integrated methodology. Three-dimensional computational fluid dynamics are used as a tool to fundamentally analyse the flow fields and the preparation process of urea–water-based solution to the reducing agent ammonia. The preparation process includes spray injection, spray interaction phenomena, and mixing of the reducing agent. The prototypically built-up hardware is integrated into an Engine-in-the-Loop test setup. In stationary engine operation, the basic measurement of temperatures and nitrogen oxides allows for the validation of the simulations. Using a simulated vehicle approach, the experimental test setup is capable of being operated in real driving scenarios. An additional 48 V boosting system is integrated and operated in the air pass to analyse and overcome thermal delay. Realistic dynamic load test results and boosted WLTC measurements of a virtual passenger car are presented.

Urban air quality and climate protection are two major challenges for future mobility systems. Despite the steady reduction of pollutant emissions from vehicles over past decades, local immission load within cities partially still reaches heights, which are considered potentially hazardous to human health. Although traffic-related emissions account for a major part of the overall urban pollution, modelling the exact interaction remains challenging. At the same time, even lower vehicle emissions can be achieved by using synthetic fuels and the latest exhaust gas cleaning technologies. In the paper at hand, a neural network modelling approach for traffic-induced immission load is presented. On this basis, a categorization of vehicle concepts regarding their immission contribution within an impact scale is proposed. Furthermore, changes in the immission load as a result of different fleet compositions and emission factors are analysed within different scenarios. A final comparison is made as to which modification measures in the vehicle fleet offer the greatest potential for overall cleaner air.

This paper demonstrates the advantages of stochastic design optimization on a passenger car diesel engine: the emission distribution in the vehicle fleet can be significantly reduced by optimizing the base engine calibration taking into account component tolerances. This paper is an extension to the work presented in [25]. The conventional calibration approach of using empirical safety coefficients is replaced by explicitly taking into account the uncertainty stemming from manufacturing tolerances. The method enables us to treat low-emission spread in a fleet as an optimization target. This process enables a more robust design and helps to avoid recalibration steps that potentially generate high costs. The method consists of four steps: an initial uncertainty analysis, which accounts for engine component tolerances and determines the underlying parameter uncertainty of the engine model—with parameter uncertainty being deviations in the model parameters resulting from component tolerances. Followed by a measurement campaign according to the design of experiments principles, the training of a stochastic engine model and the solving a stochastic optimization problem. The latter two are discussed in more detail. First, the stochastic models are validated on transient testbed measurements with different setups, which are subject to uncertainty. The model error for both engine-out particulate matter and nitrogen oxides (({text{NO}}_{{ x}})) is extremely low. Then, stochastic optimization is performed on a calibration task aiming to minimize engine-out PM for the entire fleet while ensuring that the ({text{NO}}_{{ x}}) emission remains below a given upper threshold, again for the entire fleet. Boundary constraints and smoothness constraints are employed to ensure feasibility and smooth engine maps. The optimization results are compared to the original calibration of the test engine—both for a representative nominal engine and the expected fleet behavior. The results show a significant improvement in engine-out PM while complying with the imposed constraints, including the ({text{NO}}_{{ x}}) emission limit for the entire fleet.

This paper focuses on handling improvements enabled through Steer-by-Wire systems, which have increasingly become subject of R&D, as they not only offer the potential for improving vehicle handling but also have many advantages in combination with automated driving. Handling improvements through a steering ratio depending on vehicle speed, as well as steering-wheel angle, are known from Active Front Steering systems. A new overall concept is proposed, that also takes into account lateral and longitudinal acceleration as well as steering rate, which are all available signals in a production car. The overall concept is designed in an optimization process to modify a range of established characteristic parameters known from open-loop maneuvers and the objective evaluation of vehicle handling. In this context, validated models for a vehicle and a Steer-by-Wire system are used to obtain reliable results in simulation. Possibilities for tuning the non-linear steering behavior as well as improvements in the dynamic behavior, especially in yaw damping and response time, are demonstrated.

Understanding how engine design and operation affect blow-by aerosol characteristics is key to reducing the emission of particulate matter (PM) via the crankcase ventilation system. To this end, representative aerosol data from four different diesel engines are compared on the basis of brake mean effective pressure (BMEP) and engine speed. The data were obtained from comparable sampling positions, using the same sampling system and optical particle counter. The discussion is based on the narrow particle size range of 0.4–1.3 µm, chosen for its significance with regard to blow-by aerosol sources, as well as for the challenges it poses for separation systems. Key findings include particle size distributions (PSD) of virtually identical shape, indicating that these engines share the same aerosol sources and underlying generation mechanisms. However, absolute concentrations differed by a factor of about six, presumably due to differences in engine design, which in turn affect key parameters such as temperature, pressure and flow rates. At BMEPs ≤ 10 bar all engines exhibited similarly low aerosol concentrations. With increasing BMEP the concentration rose exponentially. The engine with the smallest rise and the lowest total concentration featured an aluminum alloy piston, the smallest displacement, the lowest peak BMEP as well as the lowest maximum oil temperature. At maximum torque the aerosol concentration scaled fairly linearly with engine displacement. Increasing the engine speed had a minor impact on aerosol concentrations but affected blow-by flows, hence leading to a rise of aerosol mass flows. Within the limits of this comparative measurement studies, three generation mechanisms are provided for blow-by aerosols.