Horst E. Friedrich

Design of future concepts and variants of The Free Piston Linear Generator

The Free Piston Linear Generator (FPLG) is capable of transforming chemical stored energy into electric energy by means of an internal combustion process. As explained in [6], it achieves high degrees of efficiency at full and particularly at part load. Besides a wide area of applications, the FPLG especially meets the requirements of vehicles with range extenders or serial hybrid drives. Hence, this publication deals with the explanation of different package concepts of the FPLG for the use in electric vehicles with a generating unit. For this purpose, two different FPLG modules for future production cars are designed and the package for different combinations are illustrated in a vehicle model. This comparison presents an outlook for possible vehicle concepts of the future.

Market Prospects of Electric Passenger Vehicles

According to the United Nations Intergovernmental Panel on Climate Change n(UN IPCC), “warming of the climate system is unequivocal” and “most of the observed nincrease in globally averaged temperatures since the mid-20th century is very likely due nto the observed increase in anthropogenic greenhouse gas (GHG) concentrations” [1]. In norder to limit the expected future increase of temperature to a maximum of 2°C above nthe preindustrial level and avoid irreversible effects, it is necessary to dramatically ndecrease GHG emissions from industrialized countries and furthermore to slowdown nemissions from developing nations. nTransport constitutes a significant portion of carbon dioxide (CO2) and therefore nGHG emissions (Fig. 21.1). For example, in the western part of the European Union n(EU-15) approximately 24% of an overall 3.15 billion tons (Gt) of CO2 emissions are nassigned to transport activities. More than 90% of these emissions are from road transport, nwith cars and vans making up the largest proportion [2]. Emissions from pollutants nare decoupling from a continuously increasing mileage for the most part due to the nongoing introduction of emission after treatment systems for vehicles (Fig. 21.2). In ncontrast, for CO2 emissions there is no clear reversal of trend observable to date, making nit necessary to find solutions for lowering emissions in the future. nElectric vehicles are one important pillar of strategies to reduce GHG emissions from ntransport in the long run. At the local level, they do not emit any pollutants and in ncombination with electricity from renewable energy sources they allow reaching an nemission level close to zero even on a well-to-wheel (WTW) basis. Furthermore, they ncould provide a way to end dependence on liquid fuels based on crude oil and ensure a ndrastic reduction of noise emission level especially for inner cities.

Strom aus Abgasen — Fahrzeuggerechte Entwicklung Thermoelektrischer Generatoren

Im Zuge der zunehmenden Forderung nach Reduktion des Kraftstoffverbrauchs und CO2-Ausstoses verbrennungsmotorisch betriebener Fahrzeuge gilt es, bisher ungenutzte Energieflusse als Nutzenergie zu verwenden. Da hier bekanntermasen von der zugefuhrten Energie ein Drittel als Abgaswarme gewandelt wird, macht es Sinn, an der Nutzung dieser Potenziale zu arbeiten: Der Einsatz von thermoelektrischen Generatoren (TEG) erlaubt, Teile der bisher verlorenen Abgasexergie kunftig zur Konvertierung in elektrische Energie zu nutzen. Das Deutsche Zentrum fur Luft- und Raumfahrt (DLR) hat hierzu fahrzeuggerechte TEG entwickelt, wobei in Zusammenarbeit mit der BMW Group 200 W elektrischer Leistung in einem Versuchsfahrzeug demonstriert wurden. Mit zukunftigen Materialien sind Leistungen von bis zu 600 W und damit ein Verbrauchspotenzial von 5 % zu erwarten. Die aktuellen Forschungsschwerpunkte zielen daraufhin die Fertigungstechnik vor dem Hintergrund eines spateren Serieneinsatzes zu verbessern.

Preliminary investigations of an inductive power transfer system for the rotor power supply of an electric traction drive

The paper is devoted to the substitution of slip rings through an inductive power transfer system (IPT) for field winding supply in wound rotor traction drives. By an inductively coupled rotational transformer, the rotor-side energizing of the excitation windings can be provided isolated and free of wear. For preliminary investigations, an analytical model of the inductive link and the compensation network has been set up. Based on this, possible types of compensation networks regarding an optimal integration into an electric traction drive were carried out and compared among themselves by parameter studies. Using an experimental prototype system and on the basis of accompanying FEM calculations, the analytical model has been validated and the system tested both stationary and transient.

Integrating Phase-Change Materials into Automotive Thermoelectric Generators

Because the heat emitted by conventional combustion-engine vehicles during operation has highly transient properties, automotive thermoelectric generators (TEG) are intended for a particular operating state (design point). This, however, leads to two problems. First, whenever the combustion engine runs at low load, the maximum operating temperature cannot be properly utilised; second, a combustion engine at high load requires partial diversion of exhaust gas away from the TEG to protect the thermoelectric modules. An attractive means of stabilising dynamic exhaust behaviour (thereby keeping the TEG operating status at the design point for as long as possible) is use of latent heat storage, also known as phase-change materials (PCM). By positioning PCM between module and exhaust heat conduit, and choosing a material with a phase-change temperature matching the module’s optimum operating temperature, it can be used as heat storage. This paper presents results obtained during examination of the effect of integration of latent heat storage on the potential of automotive TEG to convert exhaust heat. The research resulted in the development of a concept based on the initial integration idea, followed by proof of concept by use of a specially created prototype. In addition, the potential amount of energy obtained by use of a PCM-equipped TEG was calculated. The simulations indicated a significant increase in electrical energy was obtained in the selected test cycle.

Influence of Tension-Compression Asymmetry on the Mechanical Behavior of AZ31B Magnesium Alloy Sheets in Bending

Magnesium alloys are promising materials for lightweight design in the automotive industry due to their high strength-to-mass ratio. This study aims to study the influence of tension-compression asymmetry on the radius of curvature and energy absorption capacity of AZ31B-O magnesium alloy sheets in bending. The mechanical properties were characterized using tension, compression, and three-point bending tests. The material exhibits significant tension-compression asymmetry in terms of strength and strain hardening rate due to extension twinning in compression. The compressive yield strength is much lower than the tensile yield strength, while the strain hardening rate is much higher in compression. Furthermore, the tension-compression asymmetry in terms of r value (Lankford value) was also observed. The r value in tension is much higher than that in compression. The bending results indicate that the AZ31B-O sheet can outperform steel and aluminum sheets in terms of specific energy absorption in bending mainly due to its low density. In addition, the AZ31B-O sheet was deformed with a larger radius of curvature than the steel and aluminum sheets, which brings a benefit to energy absorption capacity. Finally, finite element simulation for three-point bending was performed using LS-DYNA and the results confirmed that the larger radius of curvature of a magnesium specimen is mainly attributed to the high strain hardening rate in compression.

Bending Collapse Behaviour of Polyurethane Foam-Filled Rectangular Magnesium Alloy AZ31B Tubes

Quasi-static/dynamic three-point bending tests were conducted to assess the crash performance of magnesium alloy AZ31B extruded and sheet tubes at the German Aerospace Centre (DLR) – Institute of Vehicle Concepts in Stuttgart. Different foam-filled AZ31B beams with a variation of foam density and thickness were fabricated through several manufacturing processes: cold bending, tungsten inert gas welding, cathodic dip painting and polyurethane foam injection. The experimental results were compared with those from mild steel DC04 tubes. It shows that empty magnesium alloy AZ31B outperforms steel DC04 in terms of specific energy absorption for the empty tubes with equivalent volume when subjected to bending loads. It was found that the foam-filled tubes achieved much higher load carrying capacity and specific energy absorption than the empty tubes. Moreover, there is a tendency showing that a foam-filled beam with a higher foam density reaches higher load carrying capacity, but fractures earlier. The foam-filled AZ31B tube with 0.20 g/cm3 foam obtained the highest specific energy absorption, but this outperformance was weakened due to the earlier fracture. In addition, the numerical simulation utilising material model MAT_124 in LS-DYNA explicit FEA package was performed. The simulation results indicate that using calibrated stress-strain curves and failure parameters, material model MAT_124 yields a general good agreement with the experimental results.

Sandwich Lightweight Design in Automotive Usage

State of the Art

Modelling customer choice and market development for future automotive powertrain technologies

The paper introduces an innovative utility-based approach to model customer choice for alternative powertrain technologies within a dynamic scenario tool. The study covers a wide portfolio of different powertrain concepts from conventional combustion engines to advanced hybrid and electric cars. The assessment of their economic and technical attributes builds on a large set of vehicle simulation data and detailed cost models. In contrast to previous cost-based studies the applied methodology maps the observed diversity of user characteristics more realistically. Therefore, the driving behaviour and preferences of car buyers are analysed empirically based on major representative surveys and the resulting distribution functions are integrated in the model. After testing and validation with historic data the model is applied to the German vehicle market and a potential scenario for the prospective composition of the new passenger car fleet by 2030 is presented. The scenario simulation shows that a significant reduction of CO2 emissions is feasible especially by the introduction of plug-in hybrids and range extended electric vehicles. However, the growing technical complexity and the additional effort for efficiency improvements also result in increasing total costs of ownership for the customer.

Methodological Approach for Reducing Computational Costs of Vehicle Frontal Crashworthiness Analysis by Using Simplified Structural Modelling

ABSTRACT A challenge in the design and optimisation of the vehicle front structures is the high computational costs required for crash analysis. A methodological approach to simplifying finite element vehicle models and crash barriers is presented in this paper. The methodology uses global deformation characteristics of structures which are obtained from the global crash model. For the simplification of the vehicle crash model, structural regions which sustain only elastic deformations during the frontal crash are replaced by kinematic numerical representations which describe both stiffness and load paths at the interface of the substituted structures. Verification studies of the simplified vehicle model show a very good agreement of the global and local structural response during the frontal crash. Further simplifications were applied to the offset deformable barrier by replacing its detailed crushing behaviour by kinematic descriptions. Through the combined use of both simplified numerical representations, the computational cost of a Euro new car assessment program (NCAP) offset crash analysis can be reduced by around 92%. With the obtained time reduction, structural optimisation studies of the remaining structure can be conducted efficiently for the identification of weight reduction potentials.