07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/8
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Item Open Access Driving profiles of light commercial vehicles of craftsmen and the potential of battery electric vehicles when charging on company premises(2024) Heilmann, Oliver; Bocho, Britta; Frieß, Alexander; Cortès, Sven; Schrade, Ulrich; Casal Kulzer, André; Schlick, MichaelThis paper examines the extent to which it is possible to replace conventional light commercial vehicles in the heating, ventilation and air conditioning and plumbing trade with battery electric vehicles with an unchanged usage profile. GPS trackers are used to record the position data of 22 craft vehicles with combustion engines from eleven companies over the duration of one working week. Within this paper, various assumptions (battery capacity and average consumption) are made for battery electric vehicles and the charging power on the company premises. The potential of battery electric vehicles is evaluated based on the assumption that they are charged only on company premises. Using the collected data and the assumptions made, theoretical state of charge curves are calculated for the vehicles. The driving profiles of the individual vehicles differ greatly, and the suitability of battery electric vehicles should be considered individually. Battery capacity, vehicle energy consumption and charging power at the company have a substantial influence on the suitability of battery electric vehicles. Furthermore, there are differences between vehicles that can charge on the company premises at night and those that cannot or can only do so on some days.Item Open Access Approach to design of piezoelectric energy harvester for sensors on electric machine rotors(2024) Brandl, Lukas; Reuss, Hans-Christian; Heidle, DanielThe reliability and efficiency of components are key aspects in the automotive industry. Electric machines become the focus of development. Thus, improvements in efficiency and reliability have gained significance. While it is established to attach sensors to the fixed parts of machines, such as stators, moving parts like rotors pose a major challenge due to the power supply. Piezoelectric generators can operate as energy harvesters on rotors and thus enable the rotor-based integration of sensors. The research in this article proposes the first approach to the design of a piezoelectric energy harvester (PEH) for an electric machine rotor dedicated to powering a wireless sensor system. After introducing the field of PEHs, the integration of the proposed device on a rotor shaft is presented. Further, a gap between the provided and needed data for the design of a PEH is identified. To overcome this gap, a method is presented, starting with the definition of the rotor shaft dimensions and the applied mechanical loads, including a method for the calculation of the imbalance of the rotor. With the first set of dimensions of the shaft and PEH, a co-simulation is performed to calculate the power output of this rotor and PEH set. The results of the simulation indicate the feasible implementation of the PEH on the rotor, providing enough energy to power a temperature sensor.Item Open Access A quasi-dimensional burn rate model for pre-chamber-initiated SACI combustion(2024) Salerno, Francesco; Bargende, Michael (Prof. Dr.-Ing.)Tackling climate change demands an intersectoral restructuring towards a sustainable economy and way of living. Since the transport sector accounts for considerable amounts of manmade greenhouse gas emissions, incisive technical solutions are required for its fast and sustainable defossilization. Evaluating different drive types seems rational, considering the expanse of application areas with highly diverging requirements. This includes developing highly hybridized and advanced combustion engines operated with sustainable fuels and striving for optimum energy conversion efficiencies. For the latter, fast-running quasi-dimensional simulations allow conducting robust design studies and complement further testing methodologies. Therefore, phenomenological models able to assess the behavior of different combustion mechanisms based on the boundary conditions are required. This work addresses the development of such a model for a promising combustion method: Pre-Chamber (PC) initiated flame propagation coupled with Spark-Assisted Compression Ignition (SACI) combustion. Despite significant development efforts to optimize the spark ignition engine combustion (quasi-hemispherical flame propagation combustion) while avoiding knock phenomena, achieved indicated efficiencies remain around 35–40 %. Further optimizations are enabled by significant dilution or increased combustion speed. However, flammability limits and decreasing flame speeds with increasing dilution prevent substantial improvements. PC-initiated jet ignition combustion systems improve flame stability and shift flammability limits towards higher dilution levels due to increased turbulence and a larger flame area in the early Main-Chamber (MC) combustion stages. Simultaneously, the much-increased combustion speed reduces knock tendency, allowing the implementation of the innovative PC-initiated SACI combustion. The jets penetrating the MC establish a flame propagation combustion that triggers a controlled volume reaction in the remaining charge. The resulting ultra-fast combustion process converges to the ideal thermodynamic constant-volume cycle leading to indicated efficiencies of > 45 %. Physically sound modeling is enabled by first developing and validating quasi-dimensional burn rate models for the mentioned individual combustion mechanisms: SACI and PC-initiated jet ignition. The former model is based on a previous work assessing homogeneous charge compression ignition combustion. The SACI model includes the initial flame propagation combustion by employing a two-zone entrainment approach, while the volume reaction is covered by a multi-pseudo-zone approach based on a temperature-distributed auto-ignition integral. The auto-ignition integral calculation approach is based on wide-ranging reaction kinetic calculations of different fuels, including gasoline blends, ethanol, and methanol. Moreover, a calculation specification is implemented to consider the volume reaction conversion time relevant for highly diluted mixtures. Based on literature research, a burn rate model for PC-initiated flame propagation is implemented, considering two thermodynamic systems (PC and MC) connected through orifices. Both systems use a two-zone entrainment model for flame propagation combustion. The effects of the PC combustion on the MC are displayed by considering the jet-shaped flame area, the jet-induced turbulence, and a separate jet entrainment term. Moreover, the jet turbulence’s impact on the MC WHT is implemented. Finally, the burn rate models for PC-initiated flame propagation and SACI combustion are merged, including physical interaction terms between the PC effects and the volume reaction. The combined model gets along with a manageable number of understandable calibration parameters. The models are integrated into the so-called cylinder module developed at the Institute of Automotive Engineering Stuttgart. Furthermore, the individual and combined burn rate models are validated with experimental data from different geometrical engine setups. The experimental campaigns cover different loads and speeds, fuels (ethanol, standard gasoline with up to 10 vol. % ethanol), excess air dilutions (λ = 1-2.8), and compression ratios (12.6-16.4). Overall, the burn rate models show noteworthy predictive capabilities employing a fixed set of calibration parameters for a given geometric engine setup. Although significant simplifications are (necessarily) used, satisfactory prediction of the burn rates and pressure curves can be achieved for the different combustion mechanisms.Item Open Access Eine Methode zur Vibrationsanregung und -regelung in Fahrsimulatorfahrzeugen(2024) Holzapfel, Christian; Reuss, Hans-Christian (Prof. Dr.-Ing.)In dieser Arbeit wird der Einsatz eines Schwingerregers in einem bewegten Fahrsimulator mit Regelung der Schwingungsanregung beschrieben. In der Regelung wird die Stellgröße für das Signal zur Schwingungsanregung im durch Wavelet-Transformation erhaltenen Skalenbereich adaptiert. Die Anwendbarkeit der beschriebenen Methode erstreckt sich über zeitvariante Systeme und beliebig breite Frequenzbereiche. Durch das System wird ein ganzheitliches Spektrum an Fahrzeugschwingungen im Simulatorfahrzeug erzeugt. Der Einsatz der Methode in einer Probandenstudie im Fahrsimulator zeigt den Einfluss der Vibrationen auf das Fahrempfinden und Fahrerverhalten.Item Open Access Development of a low-expansion and low-shrinkage thermoset injection moulding compound tailored to laminated electrical sheets(2024) Braunbeck, Florian; Schönl, Florian; Preußler, Timo; Reuss, Hans-Christian; Demleitner, Martin; Ruckdäschel, Holger; Berendes, PhilippThis study presents a thermoset moulding compound designed for electrical machines with high power densities. The compound reduces residual stresses induced by the difference in thermal expansion during use and by shrinkage in the compound during the manufacturing process. To reduce the internal stresses in the compound, in the electrical sheet lamination and at their interface, first the moulding’s coefficient of thermal expansion (CTE) must match that of the lamination because the CTE of the electrical sheets cannot be altered. Second, the shrinkage of the compound needs to be minimized because the moulding compound is injected around a prefabricated electrical sheet lamination. This provides greater freedom in the design of an electric motor or generator, especially if the thermoset needs to be directly bonded to the electrical sheet. The basic suitability of the material for the injection moulding process was iteratively optimised and confirmed by spiral flow tests. Due to the reduction of the residual stresses, the compound enables efficient cooling solutions for electrical machines with high power densities. This innovative compound can have a significant impact on electric propulsion systems across industries that use laminated electrical sheets.Item Open Access Modeling of hydrogen combustion from a 0D/1D analysis to complete 3D-CFD engine simulations(2024) Gal, Thomas; Schmelcher, Robin; Vacca, Antonino; Cupo, Francesco; Chiodi, Marco; Casal Kulzer, AndréHydrogen and its unique properties pose major challenges to the development of innovative combustion engines, while it represents a viable alternative when it is based on renewable energy sources. The present paper deals with the holistic approach of hydrogen combustion modeling from a 0D/1D reactor evaluation with Cantera up to complete engine simulations in the 3D-CFD tool QuickSim. The obtained results are referenced to the current literature and calibrated with experimental data. In particular, the engine simulations are validated against measurements of a single-cylinder research engine, which was specifically adapted for lean hydrogen operation and equipped with port fuel injection and a passive pre-chamber system. Special attention is hereby given to the influence of different engine loads and varying lambda operation. The focus of this work is the complementary numerical investigation of the hydrogen flame speed and its self-ignition resistance under the consideration of various reaction mechanisms. A detailed transfer from laminar propagation under laboratory conditions to turbulent flame development within the single-cylinder engine is hereby carried out. It is found that the relatively simple reaction kinetics of hydrogen can lead to acceptable results for all mechanisms, but there are particular effects with regard to the engine behavior. The laminar flame speed and induction time vary greatly with the inner cylinder conditions and significantly affect the entire engine’s operation. The 3D-CFD environment offers the opportunity to analyze the interactions between mixture formation and combustion progress, which are indispensable to evaluate advanced operating strategies and optimize the performance and efficiency, as well as the reliability, of the engine.