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Nowadays, new technologies are pushing the road vehicle limits further. Promising applications, e.g., self-driving cars, require a suitable control system that can maintain the vehicle’s stability in critical scenarios. In most of current cars, the control systems actuates independently, meaning there is not a coordination or data sharing between them. This approach can produce a conflict between these standalone controllers and thus, no improvements on the vehicle’s stability are achieved or even a worse scenario can be generated. In order to overcome these problems, an integrated approach is developed in this work. This integration, defined in this work as Integrated Control (IC), is done by an intelligence coordination of all standalone controllers inside the vehicle, i.e., Anti-Lock Braking System (ABS), Electronic Stability Program (ESP) and Four-Wheel Steering System (4WS). The ABS model was built using Fuzzy logic, for which only three rules were necessary to get a good performance. To design the ESP and the 4WS, the simple handling vehicle model was used as a reference behavior. The IC was designed using the hierarchical approach with two layers, i.e., the upper and lower layer. The upper one, observes the side slip angle and depends of its value the upper layer triggers the ESP or the 4WS. Finally, in order to prove the improvements of the IC system over the non-integrated approach, a full-size vehicle model was used to perform simulation in run-off-road and μ-split scenarios.
The present papers deals with the usability of an extended Maxwell model to describe the tyre dynamics during transient driving manoeuvres. In the present article, the para-metrisation process of a dynamic tyre model is investigated in a first step, using measurement data of tyre forces from a flat trac tyre test bench, (IABG 2016). Two tyre types of dimensions 255/50 R19 and 175/55 R15 are used. The practical applicability is discussed, considering the measurement procedure and the parameter optimisation process. In a second step, the performance of the dynamic tyre model is validated using measurements of manoeuvres under higher dynamic excitation. As a last step, an outlook is given on further research planned in which the presented model and parametrisation are adapted to a larger frequency range.
Magnetorheological elastomers are a type of smart hybrid material which combines elastic properties of a soft elastomer matrix with magnetic properties of magnetic micro particles. This leads to a material with magnetically controllable mechanical properties of which the magnetorheological effect is the best known. The addition of electroconductive particles to the polymer mix adds electrical properties to the material behaviour. The resulting electrical resistance of the sample can be manipulated by external magnetic fields and mechanical loads. This results in a distinct interplay of mechanical, electrical and magnetic effects with a highly complex time behaviour. In this paper a mechanical characterisation on multiple time scales was conducted to get an insight on the short and long-term electrical and mechanical behaviour of this novel material. The results show a complex resistivity behaviour on several timescales, sensitive to magnetic fields and strain velocity. The observed material exhibits fatigue and relaxation behaviour, whereas the magnetorheological effect appears not to interfere with the piezoresistive properties.
Objective:
Magneto-active Polymers (MAP) are smart materials whose mechanical characteristics, such as elastic and shear moduli, may be controllable by means of an externally applied magnetic field.
Methods:
Various additives may be used to influence the characteristics of the polymer matrix whilst a suspension of soft and/or hard magnetic particles determine the magnetic properties of the composite. Both pre-cure and post-cure magnetization is possible.
Results:
A range of control strategies have been investigated for evaluation of the system using fluids of differing kinematic viscosity.
Conclusion:
Depending on the degree of magnetic field homogeneity, magneto-deformation and magnetostriction contribute to MAP actuation. This paper presents a novel application in the form of a peristaltic MAP tube system, applicable to flow control and pumping of hemorheological fluids in blood circulatory systems for biomedical research purposes.
The OTH Regensburg has a broad variety of study programs in technical, business, social and health sciences. Up to now there is no integral connection in the bachelor curricula between business and technical faculties except for some small subjects. The scope of this project is to develop a new course specialization which connects engineering and business thinking. Electrical engineering students should learn basics of business science and how managers think. Business students should vice versa learn fundamentals of engineering and how engineers solve problems. Students from both faculties work together in projects where they act like start-up companies developing a new product and bringing it into the market. It is seen a transdisciplinary effect: These projects gain innovative results between the disciplines compared to student projects of one isolated discipline. Evaluation results from the first two cohorts indicate high student satisfaction, high learning success as well as directions for further improvement.
Detection and compensation of current sensor gain-faults regardless of the operating-point is a crucial aspect for safety-relevant servo-drives. This paper presents and investigates a new direct phase-gain re-balancing methodology, especially suited for interior permanent magnet machine (IPM) drives mostly operating at low speed-ranges including standstill. The proposed model-based approach utilizes high-frequency signal-injection (HFI) to facilitate fast and persistent sensor monitoring for any operating state of the drive. No additional sensing hardware is required. Extraction of the HFI-phase-current response enables detection and immediate compensation of sensor gain-faults. Implementation aspects of the proposed concept are discussed thoroughly. Experimental results are presented to prove and investigate robustness, reliability and fault-tolerant performance.
Parameterization Process of the Maxwell Model to Describe the Transient Force Behavior of a Tire
(2017)
The present technical article deals with the modeling of dynamic tire forces, which are relevant during interactions of safety relevant Advanced Driver Assistance Systems (ADAS). Special attention has been paid on simple but effective tire modeling of semi-physical type. In previous investigations, experimental validation showed that the well-known first-order Kelvin-Voigt model, described by a spring and damper element, describes good suitability around fixed operation points, but is limited for a wide working range. When aiming to run vehicle dynamics models within a frequency band of excitation up to 8 Hz, these models deliver remarkable deviations from measured tire characteristics. To overcome this limitation, a nonlinear Maxwell spring-damper element was introduced which is qualified to model the dynamic hardening of the elastomer materials of the tire. However, the advantage of a more realistic description of the transient behavior leads to a more complex parametrization process. Therefore, in the proposed article attention is paid to describe the identification process including defined maneuvers to parameterize the tire model, where the accuracy of the parameter strongly depends on the quality of the available input data from measurement. In order to study this important aspect of parameterization, the reference data from simulation of the full physical tire model FTire is applied like a “virtual measurement” of specified testing maneuvers. The procedure of simulation by means of the enhanced first order dynamics model is implemented by the semi-physical tire model TMeasy. Finally, the improvements of the extended model are discussed and an outlook for future work is given.
The importance of E-Mobility is rapidly increasing, not only for private vehicle traffic but also for public transport. In and around Regensburg, Germany there are a lot of automotive companies. Therefore E-Mobility is an important topic in the curriculum of several courses of study at the East-Bavarian Technical University of Applied Sciences Regensburg (OTH).
One Master of Applied Research student at OTH has chosen the topic to develop an open-source simulation tool for electric vehicles – the EMOTH Library – based on Modelica and to refine several aspects of the library during the one and a half year of the master course.
After one semester, the basic version of the library is available and will be presented in this paper.
Monitoring of structures and related decisions based on cost optimization are discussed in this contribution. Many research publications and experimental data are currently available on inspection and on monitoring and they represent the outcome of the remarkable work done. Not all the topics of interest are widely debated and implemented in standards. The current state-of-practice in standards is summarized and aspects to be included in future recommendations are proposed. The implementation of risk-based decisions is illustrated in a case study dealing with a stadium roof in Northern Italy. Snow actions are important especially in northern and mountainous regions where heavy snowfalls and related accumulation result to considerable loads. As the roof structure fails to comply with the requirements of Eurocodes, a permanent monitoring system has been installed to allow for real time evaluation of the reliability level of the structure. The system supplies the necessary information supporting immediate decisions on closure of the stadium in case of an extraordinary snow load. Cost-optimal decisions regarding the closure of the stadium are analysed based on a limit state function, on probabilistic models for the influencing parameters including measurement uncertainty, economic losses related to closure and failure consequences. The results demonstrate the potential of the use of the monitoring systems and probabilistic reliability analysis in order to support decisions and highlight the need for their implementation in future standards.
The successful market penetration of modern absorption heat pumps (AHP) today is critically dependent on their thermodynamic performance as well as other key factors like cost, reliability and inherent safety. Conventional AHPs have a proven record in the first two aspects but crucial shortcomings in the last two. For this reason it has been imperative to search for alternative working pairs that could potentially provide comparable performance while also satisfying the rest of the conditions to the best extent possible. As part of a systematic approach towards this direction, a detailed cycle analysis was performed, utilizing an idealized AHP system containing a real working pair, which enabled the identification of five dimensionless parameters and key thermophysical properties that influence the system's thermodynamic efficiency and the circulation ratio. In order to validate those findings, these parameters were calculated and compared between conventional and alternative AHP refrigerants. It turned out that low molecular weight ratios between absorbent and refrigerant have a beneficial effect on both coefficient of performance and the circulation ratio. Furthermore, both the refrigerant acentric factor and the absorbent vaporization enthalpy shall be minimized to obtain better performance. (C) 2016 Elsevier Ltd. All rights reserved.
The frequencies of ambient vibrations are often low (below 30 Hz). A broadband (3 dB bandwidth is larger than 10 Hz at an acceleration amplitude of 9.81 m s(-2)) vibration based energy harvester is proposed for transducing mechanical energy at such low frequencies into electrical energy. The mechanical setup converts low frequency mechanical vibrations into high frequency resonance oscillations of the transducer. This conversion is done by mechanical impacts on two mechanical stoppers. The originality of the presented design is that both low-frequency and high-frequency oscillators are permanently mechanically coupled. In the equivalent mechanical circuit, this coupling is achieved by connecting the ends of the stiff spring to both seismic masses, whereas one seismic mass (collison member) is also attached to the soft spring used as the constitutive element of a low-frequency oscillator. Further, both mechanical oscillators are not realized as conventional cantilever beams. In particular, the high frequency oscillator with the natural frequency of 340 Hz is a disc-shaped diaphragm with attached piezoelectric elements and a seismic mass. It is shown that it is possible to convert mechanical vibrations with acceleration amplitude of 9.81 m s(-2) in the region between approximately 7 and 25 Hz into electrical power larger than 0.1 mW with the maximum value of 0.8 mW. A simplified mathematical model based on piecewise linear coupled oscillators shows good agreement with experimental results. The ways to enhance the performance of the harvester and improve agreement with experiments are discussed.
In the present work, an experimental study on a lab-scale adsorption refrigerator, based on activated carbon/ethanol working pair is reported. An extensive testing campaign has been carried out at the CNR ITAE laboratory, with multiple aims. First, the performance has been evaluated in terms of both COP and Specific Cooling Power (SCP), under different boundary conditions, including both air conditioning and refrigeration applications. Attractive SCPs, up to 180 W/kg and 70 W/kg for air conditioning and refrigeration, respectively, were measured. Under the same conditions, COP between 0.17 and 0.08 were obtained. In addition, different management strategies, namely, heat recovery between adsorbers and re-allocation of phase durations, were evaluated to identify their influence on the system. Both strategies confirmed the possibility of increasing COP and SCP up to 40% and 25%, respectively. Moreover, a design analysis based on the experimental results has been carried out, to suggest possible improvements of the system. The obtained results demonstrated the possibility of employing a non-toxic refrigerant like ethanol reaching performance comparable with other harmful refrigerants like ammonia and methanol. (C) 2017 Elsevier Ltd. All rights reserved.
The flow of superfluid around a translationally oscillating sphere, levitating without mechanical support, can either be laminar or turbulent, depending on the velocity amplitude. Below a critical velocity that scales as and is temperature independent below 1 K, the flow is laminar (potential flow). Below 0.5 K, the linear drag force is caused by ballistic phonon scattering that vanishes as until background damping, measured in the empty cell, becomes dominant for K. Increasing the velocity amplitude above leads to a transition from potential flow to turbulence, where the large turbulent drag force varies as . In a small velocity interval % above , the flow is unstable below 0.5 K, switching intermittently between both patterns. From time series recorded at constant temperature and driving force, the lifetimes of both phases are analyzed statistically. We observe metastable states of potential flow which, after a mean lifetime of 25 min, ultimately break down due to vorticity created by natural background radioactivity. The lifetimes of the turbulent phases have an exponential distribution, and the mean increases exponentially with . We investigate the frequency at which the vortex rings are shed from the sphere. Our results are compared with recent data of other authors on vortex shedding by moving a laser beam through a Bose-Einstein condensate. Finally, we show that our observed transition to turbulence belongs to the class of "supertransient chaos" where lifetimes of the turbulent states increase faster than exponentially.
A huge upheaval emerges from the transition to autonomous vehicles in the domain of road vehicles, ongoing with a change in the vehicle architecture. Many sensors and Electronic Control Units are added to the current vehicle architecture and further safety requirements like reliability become even more necessary. In this paper we present a potential evolution of the Electrical/Electronic-Architecture, including a Zone Architecture, to enable future functionality. We reveal the impact on the communication network concerning these architectures and present a potential communication technology to facilitate such architectures.
Magnetodielectric properties of magnetoactive elastomers comprising micrometer-sized iron particles dispersed in compliant elastomer matrices are experimentally studied in stepwise time-varying dc magnetic fields. It is found that imposition of magnetic field significantly increases both the effective lossless permittivity of these composite materials as well as their effective conductivity. These magnetodielectric effects are more pronounced for larger concentrations of soft-magnetic filler particles and softer elastomer matrices. The largest observed relative change of the effective dielectric constant in the maximum magnetic field of 0.57 T is of the order of 1000%. The largest observed absolute change of the loss tangent is approximately 0.8. The transient response of the magnetodielectric effect to a step magnetic-field excitation can be rather complex. It changes from a simple monotonic growth with time for small magnetic-field steps (<0.1 T) to a non-monotonic behavior with a significant rapidly appearing overshoot for large magnetic-field steps (>0.3 T). The settling time to the magnetic-field step excitation can reach roughly 1000 s and it depends on the applied magnetic field and sample composition. There is also significant hysteresis of the magnetodielectric effect on the externally applied magnetic field. These findings are attributed to the rearrangement of ferromagnetic filler particles in external magnetic fields. The results will be useful for understanding and predicting the transient behavior of magnetoactive elastomers in applications where the control magnetic field is time dependent. (C) 2017 Elsevier Ltd. All rights reserved.
The dynamic shear modulus of magnetoactive elastomers containing 70 and 80 mass % of carbonyl iron microparticles is measured as a function of strain amplitude via dynamic torsion oscillations in various magnetic fields. The results are presented in terms of the mechanical energy density and considered in the framework of the conventional Kraus model. The form exponent of the Kraus model is further related to a physical model of Huber et al. [Huber et al., J. Phys.: Condens. Matter 8, 409 (1996)] that uses a realistic representation for the cluster network possessing fractal structure. Two mechanical loading regimes are identified. At small strain amplitudes the exponent beta of the Kraus model changes in an externally applied magnetic field due to rearrangement of ferromagnetic-filler particles, while at large strain amplitudes, the exponent beta seems to be independent of the magnetic field. The critical mechanical energy characterizing the transition between these two regimes grows with the increasing magnetic field. Similarities between agglomeration and deagglomeration of magnetic filler under simultaneously applied magnetic field and mechanical shear and the concept of jamming transition are discussed. It is proposed that the magnetic field should be considered as an additional parameter to the jamming phase diagram of rubbers filled with magnetic particles.
Wireless sensor networks usually rely on internal permanent or rechargeable batteries as a power supply, causing high maintenance efforts. An alternative solution is to supply the entire system by harvesting the ambient energy, for example, by transducing ambient vibrations into electric energy by virtue of the piezoelectric effect. The purpose of this paper is to present a simple engineering approach for the bandwidth optimization of vibration energy harvesting systems comprising multiple piezoelectric cantilevers (PECs). The frequency tuning of a particular cantilever is achieved by changing the tip mass. It is shown that the bandwidth enhancement by mass tuning is limited and requires several PECs with close resonance frequencies. At a fixed frequency detuning between subsequent PECs, the achievable bandwidth shows a saturation behavior as a function of the number of cantilevers used. Since the resonance frequency of each PEC is different, the output voltages at a particular excitation frequency have different amplitudes and phases. A simple power-transfer circuit where several PECs with an individual full wave bridge rectifier are connected in parallel allows one to extract the electrical power close to the theoretical maximum excluding the diode losses. The experiments performed on two- and three-PEC arrays show reasonable agreement with simulations and demonstrate that this power-transfer circuit additionally influences the frequency dependence of the harvested electrical power.
The influence of an external magnetic field on the static shear strain and the effective shear modulus of a magnetoactive elastomer (MAE) is studied theoretically in the framework of a recently introduced approach to the single-particle magnetostriction mechanism [V. M. Kalita et al., Phys. Rev. E 93, 062503 (2016)]. The planar problem of magnetostriction in an MAE with magnetically soft inclusions in the form of a thin disk (platelet) having the magnetic anisotropy in the plane of this disk is solved analytically. An external magnetic field acts with torques on magnetic filler particles, creates mechanical stresses in the vicinity of inclusions, induces shear strain, and increases the effective shear modulus of these composite materials. It is shown that the largest effect of the magnetic field on the effective shear modulus should be expected in MAEs with soft elastomer matrices, where the shear modulus of the matrix is less than the magnetic anisotropy constant of inclusions. It is derived that the effective shear modulus is nonlinearly dependent on the external magnetic field and approaches the saturation value in magnetic fields exceeding the field of particle anisotropy. It is shown that model calculations of the effective shear modulus correspond to a phenomenological definition of effective elastic moduli and magnetoelastic coupling constants. The obtained theoretical results compare well with known experimental data. Determination of effective elastic coefficients in MAEs and their dependence on magnetic field is discussed. The concentration dependence of the effective shear modulus at higher filler concentrations has been estimated using the method of Pade approximants, which predicts that both the absolute and relative changes of the magnetic-field-dependent effective shear modulus will significantly increase with the growing concentration of filler particles.
An effective way to reduce greenhouse gas emissions (GHGs) is to use rurally produced straight jatropha oil as a substitute for diesel fuel. However, the different physical and chemical properties of straight vegetable oils (SVOs) require a customized setup of the combustion engine, particularly of the injection timing and quantity. Therefore, this study demonstrates the differences in the injection and combustion processes of jatropha oil compared to diesel fuel, particularly in terms of its compatibility with exhaust gas recirculation (EGR).
A 2.2 l common-rail diesel engine with a two-stage turbocharging concept was used for testing. To examine the differences in injection rate shaping of diesel fuel and jatropha oil, the injector was tested with an injection rate analyzer using both the fuels. To investigate the combustion process, the engine was mounted at an engine test bench and equipped with a cylinder pressure indication system. All limited emissions, as well as fuel consumption, were measured.
Various injection strategies, boost and rail pressure levels were tested at different EGR rates in terms of their impact on the combustion process. EGR in particular offers a great potential in the case of jatropha oil combustion due to its oxygen content. In addition, the investigation of injection rate shaping in combination with cylinder pressure analysis allowed a detailed thermodynamic evaluation of the combustion process. Ignition delay (ID) was also analyzed using a new method to calculate the start of combustion (SOC)
Based on a prospective scenario analysis, possible vehicle fleet developments for the individual motor car traffic (vehicle categories N1 and M1) are investigated for Germany in order to determine the long-term vehicle fleet structure, final energy demand, and related carbon dioxide emissions until the year 2050. In this framework, a vehicle fleet model was developed which combines a bottom-up consumer demand model with a dynamic stock-flow approach. Special emphasis is thereby given to different electric power-trains and synthetic gaseous fuels based on the power-to-gas technology. In detail, two different main scenarios are developed and, in addition, the impact of different carbon dioxide taxation levels of fossil fuels on the vehicle fleet structure are analysed. The scenario results reveal a broad range of possible future vehicle fleet structures. In the short to medium timeframe, the internal combustion engine dominates the fleet as a result of efficiency improvements and an increased use of natural gas as automotive fuel. The development of electric power-trains is initially marked by hybrid vehicles, whereas battery electric vehicles dominate the fleet structure in the long-term. Under favourable conditions, also synthetic gaseous fuels are competitive which can reduce carbon dioxide emissions even further.
Exchange conditions at the forest floor are complex due to the heterogeneity of sources and sinks and the inhomogeneous radiation but are important for linking soil respiration to measurements in the trunk space or above canopy. Far more attention has therefore been paid to above and within canopy flows, but even studies that addressed forest floor exchange do not present measurements below 1 m or 2 m. We used a multilayer model that explicitly resolves the laminar layer, the buffer layer, and the turbulent layer to calculate fluxes from the measured profiles in the lowest meter above ground and to calculate effective surface concentrations from given fluxes. The calculated fluxes were compared to measured eddy covariance fluxes of sensible heat and O3 and to chamber derived soil fluxes of CO2 and 222Rn. Sensible heat fluxes agreed surprisingly well given the heterogeneity of radiative heating and the generally low fluxes (max. 25 W m−2). The chamber fluxes turned out to be not comparable as the chamber fluxes were too low, probably due to one of the well-known problems of enclosures such as pressure differences, disturbed gradients and exclusion of naturally occurring turbulence events and surface cooling. The O3 fluxes agreed well for high O3 values reaching down to the forest floor during full coupling of the canopy by coherent structures. During most of the time, the model overestimated the fluxes as chemical reactions were dominating within the profile. One new approach was to calculate the effective surface concentration from a given flux and compare this to measured surface concentrations. This allowed the identification of situations with a coupled and decoupled forest floor layer, which has important consequences for respiration measurements in the trunk space or above canopy and should be considered in upcoming studies.
Power-to-Gas
(2017)
This chapter provides an overview on the storage technology power-to-gas for the decarbonization of all energy sectors. Other than “negative emissions” with CCS or biomass, which have clear limits in potentials, costs and environmental benefits, storage and energy conversion technologies like power-to-gas and power-to-x enable the decarbonization by neutralizing the CO2 footprint of all energy services. Via the conversion of renewable electricity into chemical energy carriers like renewable hydrogen or renewable hydrocarbons, the existing fossil infrastructure with vast and sufficient storage and transport capacities can be used with carbon neutral renewable energy. After showing the demand for storage technologies, the technology components of power-to-gas are described, building the basis for the storage system power-to-gas itself that is described in detail, including efficiency, potential, CO2 emissions, and costs. In conclusion, a technical pathway of decarbonization including costs is described for the industrial nation of Germany and necessary policy frameworks are derived.
Die Autoren dieses Werkes geben einen umfassenden Überblick über die verschiedenen Aspekte der Energiespeicherung. Sie beschreiben zunächst die Bedeutung von Energiespeichern in der Energieversorgung und definieren ihre Rolle darin. Dann gehen sie auf den Speicherbedarf in der Strom-, Wärme- und Kraftstoffversorgung im Kontext der Energiewende ein. Im Hauptteil werden die verschiedenen Speichertechnologien ausführlich vorgestellt sowie ihre Vor- und Nachteile diskutiert. Praktische Anwendungsbeispiele und die Integration von Speichern über alle Energiesektoren hinweg runden das Buch ab. Zahlreiche Grafiken und Beispiele veranschaulichen das gesamte Feld der Energiespeicher und sind als Ergänzung mehrsprachig online in Farbe verfügbar.
Die 2. Auflage enthält ein neues Kapitel zu den rechtlichen Rahmenbedingungen, neue Studien zum Speicherbedarf, Power-to-X für die chemische Industrie, neue LOHC- und Lageenergiespeicher sowie neueste Trends zu Kostenentwicklung und Batterieanwendungen.
„Endlich ein umfassendes Buch zur Energiewende, das auch für technische Laien verständlich und inspirierend geschrieben ist." Franz Alt, Journalist und Buchautor
„Das großartige Werk sei allen empfohlen, die sich wirklich für die Zukunft unseres Landes interessieren. Es zeigt auf eindrucksvolle Weise: Es wird nicht einfach, aber wir schaffen das.“ Prof. Dr. Harald Lesch, Physiker und Fernsehmoderator
Mechanische Energiespeicher
(2017)
The initiated energy transition leads to extensive changes in the supply of energy. The increasing use of renewable energy causes a shift of the produced power from centralized conventional power plants to decentralized energy plants. Because of this redistribution and the related change of load-flows, new challenges and problems for distribution system operators appear. This includes the integration of new loads and plants into the existing power grid and the guarantee of a high supply security and quality. It also includes strengthened requirements for the use and provision of reactive power. The project “SyNErgie” (“Systemoptimierendes Netz- und Energiemanagement für Verteilungsnetze der Zukunft“) deals with the development of a new reactive power management, which gets embedded in grid planning and controlling processes. One focus of the project is on the integration of decentralized energy plants (DEPs) to the reactive power management. The aim is to develop a decentralized and self-sufficient reactive power control system, which only works with local available information (measures). Therefore is no necessity of a complex communication system to the grid control center. Self-controlled Q-controller in the DEPs get characteristic curves and control the reactive power sources with local measurements (e.g. current, voltage, effective power). This new reactive power control management aims for the reactive power compensation in order to increase the integration capacity of loads and plants in a grid [2]. In order to generate characteristic curves for DEPs, it is necessary to analyze the correlation behavior between the local available measurements at the DEPs and the overall-Q-behavior of the grid group at the transformer. In that regard, influencing quantities should be considered. The aim is to involve und evaluate all relevant influencing quantities in order to determine energy plants and certain operating points, in which the correlation behavior and the prediction for the overall-Q-behavior are sufficient. The next step is to develop a model that fits these correlation behaviors and generate characteristic curves. One method to generate characteristic curves for the Q-controllers is regression analysis. The developed Q-control-system with the characteristic curves will be tested, evaluated and optimized in a following field test in cooperation with distribution system operators.
Chemische Energiespeicher
(2017)
Challenges in fluid-structure modeling of crack propagation and arrest in modern steel pipelines
(2017)
Magnetoactive elastomers (MAE) based on soft silicone matrices, filled with various proportions of large diameter ( approximately 50 mu m) iron and small diameter ( approximately 0.5 mu m) magnetite particles are synthesized. Their rheological behavior in homogeneous magnetic fields up to 600 mT is studied in detail. The addition of small magnetite particles facilitates fabrication of uniformly distributed magnetic elastomer composites by preventing aggregation and sedimentation of large particles during curing. It is shown that using the proposed bimodal filler particles it is possible to tailor various magnetorheological (MR) properties which can be useful for different target applications. In particular, either absolute or relative magnetorheological effects can be tuned. The value of the damping factor as well as the range of deformation amplitudes for the linear viscoelastic regime can be chosen. The interdependencies between different MR properties of bimodal MAEs are considered. The results are discussed in the model framework of particle network formation under the simultaneous influence of external magnetic fields and mechanical deformation.
We address a novel probabilistic approach to estimate the Worst Case Response Time boundaries of tasks. Multi-core real-time systems process tasks in parallel on two or more cores. Tasks in our contribution may preempt other tasks, block tasks with semaphores to access global shared resources, or migrate to another core. The depicted task behavior is random. The shape of collected response times of a task within a processing time is multimodal. Extreme Value approaches need unimodal response time distributions to estimate the Worst Case Response Time of tasks. The new proposed method derives a set of three task set shapes from the source task set. It is used to minimize the uncertainty of random task behavior by maximizing the coverage of possible Worst Case Response Times. The case study evaluates the new proposed estimation method by the use of dynamically generated random tasks with varying task properties.
Ethical, intercultural and professional impulses integrated into a transmission systems lecture
(2017)
In the sixth semester of the bachelor study course “Electrical Engineering and Information Technology”, a lecture “Transmission Systems” is given. It explains basic principles, circuits and systems of electrical and optical transmission systems. Short intellectual impulses, which address professional, intercultural and ethical issues of engineers' working life are integrated into this regular lecture. In each lecture unit, an impulse with one specific topic is given approximately in the middle of the lecture hour. An evaluation was done at the end of the semester, which shows that most of the students remember the discussed topics and state high interest due to high importance for their professional life. Due to these encouraging results, this concept will be developed further.
The process of engineering models of existing real-time system components is often difficult and time consuming, especially when legacy code has to be re-used or information about the exact timing behaviour is needed. In order to tackle this reverse engineering problem, we have developed the tool CoreTAna. CoreTAna derives an AUTOSAR compliant model of a real-time system by conducting dynamic analysis using trace recordings.
Motivated by the challenge of assessing the quality of reverse engineered models of real-time software, we present a novel mathematical measure for comparing trace recordings from embedded real-time systems regarding their temporal behaviour. We also introduce a benchmark framework based on this measure, for evaluating reverse engineering tools such as CoreTAna. This considers common system architectures and also includes randomly generated systems and three systems of industrial automotive projects. Finally, an industrial case study demonstrates other use cases of our measure, such as impact analysis.
Several concepts are known for improving processor safety, all of them having their pros and cons. Some are very resource intensive, others have limited capabilities regarding the provided error safety. In this paper we use research on channel coding of noisy communication channels known from communication theory as an analogy to random bit errors in processors. We incorporate this knowledge into processor design to suggest a new error correction concept by using channel coding in processors. The new concept of a Channel Coded Processor could provide effective implementation of redundancy by the channel coding that enables error correction. The concept could also create a complete chain of redundancy in all areas and components of the processor ranging from the code compiler through the processing hardware to the output of the information.
Dieses Lehrbuch stellt die Methoden der Mehrkörpersimulation anschaulich dar und erläutert an einfachen Beispielen die Vor- und Nachteile bei der praktischen Anwendung. In den Text integrierte Matlab-Skripte und -Funktionen verdeutlichen die einzelnen Methoden. Die Modellbildung, die mathematische Beschreibung und die numerische Simulation von Systemen starrer Körper bilden dabei die Schwerpunkte. Konkrete Beispiele beinhalten die Eigendynamik eines Traktors mit Vorderachsfederung, das Hubschrauberrotorblatt sowie eine Pkw- Vorderachse. Die entsprechenden Matlab-Skripte und Lösungen zu den Übungsaufgaben können auf der Springer-Homepage beim Buch heruntergeladen werden. Neu aufgenommen wurden SparseMatrix Operationen sowie ein Beispiel zu einfach geschlossenen kinematischen Schleifen.
Modelling and simulation of safety relevant Driver Assistance Systems (DAS) and Vehicle Dynamics Controllers (VDC) which act in standard and limit situations lead to increasing accuracy demands in the description of dynamic reactions of tyre contact forces, e.g. For that purpose, first-order approaches are widely applied in this field of vehicle dynamics and handling, which originate from Schlippe & Dietrich, were modified by Pacejka and later on refined by Rill.
The present paper deals with the experimental validation of tyre dynamics approaches as it is widely applied in tyre models for vehicle dynamics and handling. Firstly it gives a brief derivation of two modelling principles regarding the deflection velocity in the considered direction of the tyre’s deformation. This is than followed by a brief description of the performed measurement procedure. From the measurements, a set of model parameters of the considered tyre, depending on different manoeuvre speeds and frequencies, is identified, where no particular fitting parameters for the tyre dynamics are needed. Based on these model parameters, the related dynamic simulations are carried out. The comparisons show that the applied first-order model describes the behaviour quite well within a certain operation range, whereas the second-order approach cannot deliver better results in spite of the longer computational time. However, for investigations within an enlarged frequency range of the steer input and at high slip angles, a more detailed model is recommended.
In the present paper design, realization and testing of a novel small scale adsorption refrigerator prototype based on activated carbon/ethanol working pair is described. Firstly, experimental activity has been carried out for identification of the best performing activated carbon available on the market, through the evaluation of the achievable thermodynamic performance both under air conditioning and refrigeration conditions. Once identified the best performing activated carbon, the design of the adsorber was developed by experimental dynamic performance analysis, carried out by means of the Gravimetric-Large Temperature Jump (G-LTJ) apparatus available at CNR ITAE lab. Finally, the whole 0.5 kW refrigerator prototype was designed and built. First experimental results both under reference air conditioning and refrigeration cycles have been reported, to check the achievable performance. High Specific Cooling Powers (SCPs), 95 W/kg and 50 W/kg, for air conditioning and refrigeration respectively, were obtained, while the COP ranged between 0.09 and 0.11, thus showing an improvement of the current state of the art. (C) 2016 Elsevier Ltd. All rights reserved.
Effects of Quality Control on Reliability of Reinforced Concrete Structures according to Eurocodes
(2016)
The effect of quality control on structural reliability represents an increasingly important concern of designers and thus is investigated in this contribution, focusing on reinforced concrete structures. Recent European documents for structural design – Eurocodes, fib Model Code 2010 and ISO 2394:2015 for general principles on structural reliability indicate that the partial factors may be adjusted to available information on the quality control of structures. In particular, the partial factors for concrete and steel strength may be significantly reduced taking into account actual execution quality and related available data. Using probabilistic methods of structural reliability, effects for execution quality are investigated in this contribution considering two fundamental reinforced concrete members: a beam (or slab) exposed to bending and a short column exposed to compression. It is shown that the reliability of reinforced concrete members may vary with the load ratio of variable and permanent actions. It appears also that the structural members of a basic quality, designed using unreduced partial factors, have a greater reliability level than the members of an increased quality, designed using the partial factors reduced according to EN 1992 1 1. This provides the basis for recommendations for further code developments.
For the dynamic simulation of on-road vehicles, the model-element "tire/road" is of special importance, according to its influence on the achievable results. Sufficient description of the interaction between tire and road is one of the most challenging tasks of vehicle modeling. Two groups of tire models can be classified: handling models and structural or high-frequency models. Usually, various assumptions are made in modeling vehicles as multibody systems. Therefore, in the interest of balanced modeling, the precision of the complete vehicle model should stand in reasonable relation to the performance of the applied tire model. Handling tire models are characterized by a useful compromise between user friendliness, model complexity, and efficiency in computation time on the one hand, and precision in representation on the other hand. The present paper describes the general approach of the semi-physical tire model TMeasy for vehicle dynamics and handling simulation and its enhancement for bore torque simulation in Version TMeasy 5. A parameter fitting process realized by TESIS DYNAware and the validation of real tire behavior by simulation with DYNA4 is presented. Even with first guess parameters, the TMeasy tire model behaves in a realistic and plausible manner. Parameter estimation is intuitive and datasets from previous model versions can be easily migrated. After parameter fitting, the simulation results correlate well with both the tire test rig and full vehicle measurements. The enhancement of a three-dimensional slip calculation in the latest version does not modify the model behavior for high slip conditions, but improves the results not only for highly dynamic situations but also for low speed maneuvers such as parking.
In the forming tools for pressing car body parts, heavy blankholders are used to prevent buckling and wrinkling of the blank. During each press cycle, those large masses need to be lifted, raising thereby the structural dynamic load on the forming tool and on the press. Therefore a detailed knowledge about the forming tool dynamics is essential for an accurate and robust design of forming tools. In this paper, a dynamic finite element method (FEM) simulation of selected automotive forming tool is presented enabling identification of regions of critical stresses. For validation of the simulation results, the kinematic responses of the tool's components are compared with the measurements obtained in an experiment.
The feasibility of implementing power-to-gas systems, to absorb surplus solar power from electricity distribution networks and carbon dioxide from biomass anaerobic digestion (AD) plant, in order to produce synthetic methane was investigated for a region of Southern Germany that has a high solar power penetration. The analysis was based on time series electricity data for 2012 from which future load profiles were computed in accordance with the expected installed capacities of solar power across the period 2015–2025. The electrolyser capacity required to absorb 20% of excess solar energy occurring within the region's low voltage network in 2025 was estimated to be 370 MWe. First order considerations of the region's gas grid, electricity network and existing AD sites suggest that such a deployment could be achieved by installing sub-MW (and some multi-MW) power-to-gas plant at several hundred AD sites.
The present paper gives an outlook on a bandwidth of required installed power-to-gas capacity in the German power sector fed by 100% renewable generation until 2050. Two scenarios were simulated to quantify cost effects of power-to-gas on the electricity system: once with, once without additional short-term flexibility options to a system using fossil natural gas as sole flexibility option instead.
As a result, at latest in 2035, power-to-gas capacity expansion has to take place to reach required installed capacities of up to 89-134 GW in 2050. Application of power-to-gas as long-term flexibility leads to cost savings of up to 11,7-19 bn Euro enabling a fully renewable system in 2050.
Power-to-Gas
(2016)
This chapter provides an overview on the storage technology power-to-gas for the decarbonization of all energy sectors. Other than “negative emissions” with CCS or biomass, which have clear limits in potentials, costs and environmental benefits, storage and energy conversion technologies like power-to-gas and power-to-x enable the decarbonization by neutralizing the CO2 footprint of all energy services. Via the conversion of renewable electricity into chemical energy carriers like renewable hydrogen or renewable hydrocarbons, the existing fossil infrastructure with vast and sufficient storage and transport capacities can be used with carbon neutral renewable energy. After showing the demand for storage technologies, the technology components of power-to-gas are described, building the basis for the storage system power-to-gas itself that is described in detail, including efficiency, potential, CO2 emissions, and costs. In conclusion, a technical pathway of decarbonization including costs is described for the industrial nation of Germany and necessary policy frameworks are derived.
Die Einhaltung der Spannungsbandgrenzen im Niederspannungsnetz durch die dezentrale Emspeisung von Erzeugungsanlagen ist oft der Grund für Netzausbaumaßnahmen. Dem Netzbetreiber stehen mittlerweile viele Losungsmaßnahmen zur Behebung des Spannungsbandproblems zur Verfügung Innovative Konzepte wie der regelbare Ortsnetztransformator (RONT) oder Blindleistungsregelung sind bereits serienreif und werden eingesetzt. Unklarheit herrscht oft noch darüber, welche Maßnahmen bzw Kombinationen langfristig wirtschaftlich günstig sind und sich hinsichtlich der Netzplanung als vorteilhaft erweisen. Ein Forschungsprojekt an der Ostbayerischen Technischen Hochschule Regensburg untersucht verschiedene Lösungsmaßnahmen systematisch, um sie wirtschaftlich, technisch und energetisch bewerten zu können. In 20 Netzen wird in diskreten Schritten die Integration von Erzeugungskapazität am Beispiel der PV simuliert. Der Zubau umfasst den Bereich von 0-100% des möglichen Dachflächenpotenzials. Nach jedem Zubauschritt wird die maximale Spannungsanhebung berechnet. Bei Überschreiten einer Spannungsanhebung in Höhe der in [VDE, FNN Erzeugungsanlagen am Niederspannungsnetz, VDE-AR-N 4105:2011-08] verankerten drei Prozentpunkte, oder der Stromtragfähigkeitsgrenze eines Betriebsmittels erfolgt ein Netzausbau. Dabei werden die Optionen RONT, die Parallelverkabelung, drei Stufen des Einspeisemanagements (Spitzenkappung auf 85%, 70% und 55%), die Blindleistungsregelung (cosφ(P)), der Zubau von zusätzlichen Ortsnetzstationen und die Verwendung von Strangreglern untersucht. Je kleiner das Ortsnetz, desto stärker bedingt sich die Kostenentwicklung durch die gewählte Primärmaßnahme. Klassischer Netzausbau ist in kleinen Netzen meist teurer als der Einsatz von RONT oder Strangreglern. In größeren Netzen können Parallelverkabelung oder zusätzliche ONS zu günstigen Ausbaupfaden führen. Maßnahmen die anfangs nahezu keine Investition in Netzbetriebsmittel benötigen (Einspeisemanagement, Blindleistungsregelung) sind initial mit Abstand am günstigsten. Im Mittel günstiger als RONT sind anfangs auch Verkabelung und Strangregler, jedoch bei höherer Ergebnisstreuung. Bereits nach fünf Perioden liegen die mittleren Gegenwartswerte für starke Spitzenkappung, Blindleistungsregelung und zusätzliche ONS häufig über der Maßnahme RONT. Die geringste Kostenstreuung tritt beim Einsatz von RONT auf. Mittel- und langfristig liegen die Mediane fast aller Primärmaßnahmen über den wahrscheinlich auftretenden Kosten für Strangregler und RONT. Bei Erschließung von zusätzlichen 25% des theoretisch maximalen Potenzials nach Erreichen der NAK betragen die Kosten bei RONT-Einsatz ca. 125/kWp. Parallelverkabelung verursacht rd. 45, Blindleistungsregelung rd. 55 €/kWp Mehrkosten. Bei 50% des Ausbaupotenzials führen Parallelverkabelung und Blindleistungsregelung mit im Mittel 50 bzw. 75 €/kWp sogar zu noch höheren Mehrkosten. Für 20 GW PV-Leistung in der Niederspannung bedeutet dies über 1 Mrd. Zusatzkosten. RONT und Strangregler erweisen sich zudem kostenrobust gegenüber unerwartet ausbleibendem Kapazitätszubau. Analysen dazu und Ergebnisse für andere Zinssätze und Zeitskalen befinden sich in [INA, Informationsportal: Regelbare Ortsnetztransformatoren, 2015. http://ront.info].
For the dynamic simulation of on-road vehicles, the model-element “tire/road” is of special importance, according to its influence on the achievable results. Sufficient description of the interaction between tire and road is one of the most challenging tasks of vehicle modeling. Two groups of tire models can be classified: handling models and structural or high-frequency models. Usually, various assumptions are made in modeling vehicles as multibody systems. Therefore, in the interest of balanced modeling, the precision of the complete vehicle model should stand in reasonable relation to the performance of the applied tire model. Handling tire models are characterized by a useful compromise between user friendliness, model complexity, and efficiency in computation time on the one hand, and precision in representation on the other hand.
Energieforschung
(2016)
Least squares pose estimation of cylinder axes from multiple views using contour line features
(2015)
In this paper, a new method for a minimum-error pose estimation of cylinder axes based on apparent contour line features from multiple views is presented. Novel model equations for both single and particularly multiple views are derived, and based upon these, an iterative algorithm for least squares fitting the model to imaged cylinder contour line features is introduced. The good performance and fast convergence of the proposed algorithm is shown by solving exemplary fitting problems.
In Sub-Saharan Africa less than 10% of the rural population has access to electricity [1]. Stand-alone power systems (SPS) can be a solution to the problem of the lack of electricity, which highlights challenges such as modules installation costs as well as the sufficient knowledge required for installing, maintaining and operating such systems. With this fact in mind, a 250 W Low Head turbine system was developed and optimized to have the advantage of the simplicity of installation and a construction from readily available materials. This design scores the electrical efficiency of 60%, reduces manufacturing unit coast to 130 € and takes into account the necessity of providing a clear and simple manual describing the manufacturing and installation. A better version of the load controller, using a microcomputer is under current development. Mounting of the system have been simplified to reduce the amount of construction material required to provide uninterrupted 230 V at 50 Hz AC or optional 12 V DC power supply. Current efforts aim on transferring the required mechanical and electrical knowledge for building, programming, installing and maintaining such system to schools in targeted countries. This project doesn’t only provide people in rural developing countries a gleam of hope to catch up with the developed countries, but also helps students to use their theoretical knowledge to realize practical applications.
Transient models of multi phase electric machines are already implemented in the Modelica Standard Library (MSL). However, advanced effects like saturation and skin effect are not taken into account. As an extension to the MSL models, the new EMachines library is presented. This package will be released as a supplemental library to the commercial EDrives library. The particular focus of this paper is on the deep bar effect of induction machines. A comparison of simulation results demonstrates the influence of the skin effect on the operational behavior of the machines. At the end of this publication further developments of the EMachines library will be outlined.
In this paper, a new method for a minimum-error pose estimation of cylinder axes based on apparent contour line features from multiple views is presented. Novel model equations for both single and particularly multiple views are derived, and based upon these, an algorithm for least squares fitting the model to imaged cylinder contour line features is introduced. The good performance of the proposed algorithm is shown by solving an exemplary fitting problem.
This paper presents the new open source Modelica libraryWindPowerPlants. For the economic assessment of either a wind power plant or an entire wind park, the accurate prediction of the energy output is essential. Such prediction is usually performed by means of calculations based on statistical wind data. The proposed WindPowerPlants library is capable of assessing the energy output both for statistical and real wind data based on time domain simulations.
In the presented version of the library wind turbine models are modeled with pitch control. The generator models have variable speed and an optional connector to the mains. The entire library is based on power balance conditions and losses are fully neglected. Yet, the library can be extended towards more detailed models considering different types of losses.
The structure and components of the library are presented. Simulations examples are shown and compared with reference data. The applicability of the proposed WindPowerPlants library is demonstrated and possible enhancements are discussed.
This book proposes a radically new approach for characterizing thermophysical and mechanical properties of zeolite-based adsorbent coatings for Adsorptive Heat Transformers (AHT). It presents a developed standard protocol for the complete characterization of advanced coated adsorbers. Providing an in-depth analysis of the different procedures necessary for evaluating the performance of adsorbers, it also presents an analysis of their stability under the hydrothermal and mechanical stresses during their entire life cycle. Adsorptive Heat Transformers (AHT), especially adsorption chillers and heat pumps, are considered to be promising technologies to increase thermal energy efficiency. Nevertheless, an overall increase in performance of this apparatus is necessary for them to be considered a mature technology to be used commercially. Development of innovative coated adsorbers can be perceived as a key issue for the enhancement of AHT technology. This procedure relies on the deposition, either by means of a binder or by direct crystallization, of the adsorbent material over a metallic heat exchanger, aiming at the improvement of the heat transfer between the external heat source and the adsorbent itself. This book offers a valuable resource to those working on the development of novel adsorbent materials and advanced adsorbent beds for heating and cooling applications. It is also intended for researchers interested in renewable energy and energy efficiency.
In der Automobilindustrie ist neben der Elektromobilität und dem Leichtbau auch das Gebiet der Fahrerassistenz ein Zukunftsfeld. Speziell Fahrerassistenzsysteme, wie z.B. der Stauassistent, sind in Hinblick auf das autonome Fahren als dessen Vorstufe zu sehen. Aktuelle Assistenzfunktionen basieren auf der Präsenz des Fahrers. Die Fahrerassistenzsysteme sind nur durch Funktionen der Elektrik/Elektronik ermöglicht worden. Durch Maßnahmen der "Funktionalen Sicherheit" müssen Risiken, die durch Fehler der Elektrik/Elektronik zu Gefahren führen könnten, unter eine akzeptierte Grenze gesenkt werden. Die Diskussion über die gesetzlichen Grundlagen für das autonome Fahren ist erst am Anfang des öffentlichen Interesses. In diesem Zusammenhang ist es sinnvoll, die Notwendigkeit der Anpassung der bestehenden normativen Anforderungen zur funktionalen Sicherheit in die Diskussion mit einzubeziehen. Im ersten Ansatz wird in diesem Paper untersucht, ob von anderen Anwendungen mit automatisiertem Fahrbetrieb, wie er bei Schienenfahrzeugen realisiert ist, Ableitungen möglich sind. Im zweiten Ansatzpunkt wird konkret unter dem Gesichtspunkt des autonomen Fahrens zum Automobil auf die Gefahren-und Risikoanalyse, gemäß ISO 26262 Teil 3 eingegangen. Im Rahmen dieser Diskussion werden die drei Bewertungskriterien der Gefahren- und Risikoanalyse (severity, probability of exposure and controllability) im Paper beleuchtet. Es wird gezeigt, dass für autonomes Fahren ein zusätzliches Bewertungskriterium der Situationskomplexität sinnvoll ist, das das Umfeld einbezieht. Denn die Kontrollierbarkeit ist auf den Fahrer bezogen. Bei dem neuen Kriterium werden unter anderem der Einfluss durch die Verkehrsdichte sowie die Car-2-Car Kommunikation oder auch Fehler bzw. Ausfälle in der Car-2-X Kommunikation (zur Infrastruktur) berücksichtigt.
In den Verteilungsnetzen (VN) besteht erheblicher Optimierungsbedarf, um die geplanten Leistungen an dezentralen Erzeugungsanlagen (EZA) aufnehmen und um die erzeugte Energie an das Übertragungsnetz abgeben zu können. Bislang konnte der Aufwand für die Netzplanung im VN mittels standardisierter Abläufe und großzügigen Reserven im Spannungsband und der Stromtragfähigkeit begrenzt werden. Im Zuge des Zubaus an EZA schwinden diese Reserven und Netzplanungsaufgaben müssen individueller für einzelne Netzabschnitte gelöst werden. Die Forschungsstelle für Energienetze und Energiespeicher (FENES) der OTH Regensburg beschäftigt sich u. a. mit der Fragestellung wie die Netzplanung im Verteilungsnetz hinsichtlich der neu entstandenen Herausforderungen optimiert werden kann und gleichzeitig praktikabel bleibt. Kernthemen sind dabei das Spannungs- und das Blindleistungsmanagement im Verteilungsnetz. Im Zuge der Energiewende gilt es die vorhandene Netzinfrastruktur noch effizienter auszunutzen und den Ausbau noch stärker bedarfsorientiert zu gestalten. Infolgedessen bewegt sich der Netzbetrieb näher an den Grenzen der Netzparameter (z. B. Spannungshaltung und Auslastung). Von daher müssen bislang praktizierte Verfahren weiter entwickelt werden, , um weiterhin einen sicheren und stabilen Netzbetrieb zu gewährleisten.
Smart Grid, Smart Metering, Electromobility and the regulation of the power network are keywords of the transition in energy policies. In the future, the power grid will be smart. Due to this the OTH Regensburg does research in this area based on different projects. This paper presents a data collection, analyzing and monitoring software for a reference Smart Grid. We discuss two possible architectures for collecting data from energy analyzers. The performance is analyzed with respect to real-time monitoring, analyzing load peaks and automated regulation of the power grid.
This article deals with the question to what extent the automotive standard for functional safety ISO 26262 is also applicable to motorbikes. It examines thereby, on the one hand where to find comparable criteria between cars and motorbikes from the standpoint of functional safety, and, on the other hand, where differences between the automobile and the motorbike must be considered. It shows the extent to which the safety-related automotive standard is applicable to motorbikes. Furthermore, the differences are determined, which must lead to the consequence of a new “state of the art” and to a new standard for motorbikes. On the example of a light function the new MSIL classification gets applied. In this article, the motorbike is viewed as a whole. For the most parts the standard is also valid for scooters.
Self-phase modulation in lithium niobate wave-guides with cascaded quadratic and cubic nonlinearities is characterized by comparison of amplitude and phase of input and output pulse envelopes and spectra. Cubic nonlinear susceptibility coefficients of lithium niobate were determined from the measured nonlinear phase shifts.
A design of a 3-phase inductive power and data transfer for multiple stationary loads is proposed. It focuses on stable load voltages while minimizing electromagnetic interference. Loads are contactless charging units of electric vehicles at car parks. Physical properties of the inductive couplers are modelled via 3-D FEM and lumped parameters are used for system studies. Design principles are verified at laboratory scale with a purpose built test stand.
The main objective of this work is to introduce an innovative hybrid heating appliance incorporating a gas condensing boiler and a zeolite-water adsorption heat pump. The condensing boiler is applied to drive the zeolite-water heat pump for the heating base-load and to assist the heat pump in the so called “mixed operation” mode, in which both the heat pump and the condensing boiler are working in series to cover medium heating demands. Peak heating demands are covered by the condensing boiler in the so called “direct heating” mode. The three operation modes of the hybrid heating appliance have been technically described.
In addition, the laboratory test conditions for estimating the seasonal heating performance according to the German Guideline VDI 4650-2 have been introduced. For both heating systems 35/28 °C and 55/45 °C, which represent the typical operating conditions of floor and high temperature radiating heating systems in Europe, seasonal heating gas utilization efficiencies of 1.34 and 1.26 have been measured, respectively with a ground heat source.
In two field test installations in one-family houses in Germany, the introduced heating appliance showed 27% more seasonal gas utilization efficiency for heating and domestic hot water production, which is equivalent to a CO2-emission reduction of 20% compared to the gas condensing boiler technology.
Festbettspeicher bieten die Möglichkeit, thermische Energie auf einem hohen Temperaturniveau zu speichern. Die oft kugelförmigen Schüttgüter bestehen aus Materialien hoher Dichte und Wärmekapazität. Neben der Wärmespeicherung können mithilfe dieser Schüttungen partikelbeladene Abgase entstaubt werden. Die Strömungs-, Wärmetransport- und Entstaubungsvorgänge bei der Speicherung von Wärme in einem Schüttschichtwärmeübertrager werden in Zusammenarbeit mit Fraunhofer Umsicht, Institutsteil Sulzbach-Rosenberg, untersucht. Einen entscheidenden Aspekt der Arbeiten stellt die numerische Simulation der im Wärmeübertrager ablaufenden Vorgänge dar. Die transiente Simulation von Schüttschichtwärmeübertragern ist nur mit Vereinfachungen möglich, da aufgrund der komplexen Geometrie und der daraus folgenden feinen Vernetzung eine enorme Rechenleistung benötigt wird. Bei den in diesem Beitrag vorgestellten Ergebnissen werden die physikalischen Vorgange in einem Ausschnitt der Schüttschicht simuliert, in dem die Kugelgeometrie detailliert modelliert ist. Die Ergebnisse der numerischen Simulation werden durch analytische Berechnungen aus der Literatur bestätigt. Eine Reihe von Parametervariationen zeigen die Einflüsse verschiedener Größen beispielsweise auf den Druckverlust sowie den Unterschied zwischen radialer und axialer Durchströmung einer Schüttschicht. Die Entstaubung partikelbeladener Gase innerhalb einer Schüttschicht wird zunächst anhand einer Einzelkugel untersucht; die Erweiterung auf die Entstaubung in einer Kugelpackung ist vorgesehen. Die Ergebnisse der numerischen Simulationen sollen mit den an einem Versuchsstand experimentell bestimmten Daten verglichen werden.
Differenzierte Kohlenwasserstoffanalytik im Dieselabgas bei verschiedenen Motorbetriebszuständen
(2014)
Die für Dieselfahrzeuge gesetzlich vorgeschriebenen Grenzwerte bezüglich der Schadstoffkomponenten Kohlenwasserstoffe und Kohlenmonoxid können nur durch den Einsatz eines Diesel-Oxidationskatalysators erfüllt werden. Um erhöhte Emissionen infolge eines geschädigten Katalysators zu vermeiden, gilt es, dieses abgasrelevante Bauteil auch während des Betriebes zu überwachen. Die zukünftigen gesetzlichen Anforderungen an die Überwachung erfordern ein Verfahren das eine zuverlässige und hochgenaue Diagnose zulässt. Deshalb entwickelt eine Forschungsgemeinschaft aus Industrieunternehmen und Hochschulen einen neuartigen Kohlenwasserstoffsensor zur hochgenauen Analyse von unverbrannten Kohlenwasserstoffen im Abgasstrang. Hierfür ist die Kohlenwasserstoffzusammensetzung des Dieselabgases bei verschiedenen Motorbetriebszuständen zu ermitteln. Zur differenzierten Untersuchung der Kohlenwasserstoffkomponenten wurde in der Arbeit ein Massenspektrometer eingesetzt, das mit chemischer Ionisation arbeitet. Anhand eines Abgasscreenings konnte eine Reihe von Kohlenwasserstoffen (Alkane, Alkene, Alkine, Alkadiene und aromatische Kohlenwasserstoffe) identifiziert werden, die typisch für das Dieselabgas stehen. Die Moleküle Ethin, Ethen und Propen wurden gezielt betrachtet. Die Ergebnisse zeigen, dass bei kalten Betriebsbedingungen diese drei Komponenten etwa die Hälfte der Gesamtkohlenwasserstoffkonzentration ergeben. Ein weiterer Punkt der Untersuchungen war die Diesel-Partikelfilter-Regeneration. Wie erwartet, lassen sich Kohlenwasserstoffmoleküle mit höheren Massen feststellen, die auf unverbrannten Dieselkraftstoff zurückzuführen sind. Anhand der Ergebnisse zeigte sich.dass sich das mit chemischer Ionisation arbeitende Massenspektrometer hervorragend für ein Abgasscreening eignet. Zahlreiche Kohlenwasserstoffe konnten identifiziert werden, die repräsentativ für das Dieselabgas stehen. Es sollten Moleküle bei verschiedenen Motorbetriebsbedingungen untersucht werden, die einen möglichst großen Anteil an der Gesamtkohlenwasserstoffkonzentration besitzen. Die Auswahl fiel aufgrund der gemessenen Massenspektren, vor und nach dem Diesel-Oxidationskatalysator, auf die Komponenten Ethin, Ethen und Propen. Zudem kann bei diesen Molekülen eine Masseninterferenz mit anderen Abgaskomponenten ausgeschlossen werden. Im unteren Teillastbereich und kaltem Motor machen diese Kohlenwasserstoffe bis zu 50%, gemittelt über alle Messstellen vor, im und nach dem Diesel-Oxidationskatalysator, der Gesamtkohlenwasserstoffkonzentration aus. Bei betriebswarmem Motor reduziert sich ihr Anteil auf ein Drittel Die höchste Konzentration unter den drei Komponenten besitzt dabei Propen. Mit steigendem Drehmoment nimmt der Anteil dieser drei Komponenten fortlaufend ab,was dafür spricht, dass Moleküle mit höheren Massen einen höheren Anteil einnehmen. Die Kohlenwasserstoff-Emissionen bewegen sich bei diesen Motorbetriebspunkten mit betriebswarmem Katalysator jedoch bereits bei sehr niedrigen Werten. Während der untersuchten Diesel-Partikelfilter-Regeneration mit späten Nacheinspritzungen zur Abgastemperaturerhöhung lassen sich Moleküle mit höheren Massen nachweisen. Diese sind typisch für die Reinkomponente Dieselkraftstoff. Der Anteil von Ethin, Ethen und Propen an der THC-Konzentration beträgt dann ca. 40%.
Solar energy represents a clean, natural and sustainable source of energy. Solar photovoltaic panels can be installed on roofs of structures or in the ground. This contribution focusses on ground-mounted systems, which are presently widely implemented. At present limited guidelines on the design of solar ground-mounted structures are available. Usually standards for the design of normal buildings are applied. However, the design of ground-mounted structures significantly differs from common structural design by: (1) a lower design lifetime (20-25 years) is accepted; (2) failure is not associated with the loss of human life; (3) resistance uncertainties need due attention; (4) uplift wind forces dominating structural reliability are associated with a large scatter. That is why the reliability analysis and optimal design of ground-mounted solar systems is investigated herein. The failure costs and especially their ratio to the initial costs are analyzed considering the data provided from the industry. Probabilistic reliability analyses are carried out and optimum design levels are computed for representative cost ratios. The optimal target reliability depends on the ratio between failure and initial costs; reliability index of 3.5 corresponds to a reasonable cost ratio of 10.
Beitrag und Praesentationsmaterial eines Vortrags ueber differenzierende Kohlenwasserstoffanalytik im Dieselabgas bei verschiedenen Motorbetriebszustaenden. Mit einem neu entwickelten, hochgenauen HC-Sensor werden unverbrannte HC im Abgas untersucht. Die differenzierende Untersuchung erfolgt an einem Massenspektrometer, das mit chemischer Ionisation arbeitet. Die Molekuele Ethin, Ethen und Propen wurden gezielt betrachtet. Es zeigt sich, dass bei kalten Betriebsbedingungen diese drei Komponenten etwa die Haelfte der gesamten HC Konzentration ergeben. Ein weiterer Punkt ist die Regeneration des Dieselpartikelfilters.
Bei Ottomotoren mit Direkteinspritzung besteht beim Kaltstart, den Warmlaufphasen und auch durch den Einfluss anderer Parameter wie z. B. des Einspritzzeitpunkts oder des Einspritzdrucks die Problematik, dass Kraftstoff an die Zylinderlaufbahn aufgetragen wird und sich mit dem Motoröl vermischen kann. Eine Verstärkung dieses Kraftstoffauftrags ist unter anderem der Verschiebung der Motorbetriebspunkte zu höheren Mitteldrücken und damit einem Wirkungsgrad optimaleren Betrieb geschuldet. Eine Veränderung der physikalischen und chemischen Eigenschaften des Motoröls durch die Verdünnung mit Kraftstoff ist die Folge. Durch die Verringerung der Viskosität des Motoröls kann es zu einer verminderten Schmierwirkung des Öls kommen, die im schlimmsten Fall zur Schädigung des Motors führt. Existierende Offline-Analysemethoden die zeitintensive Laboranalysen nach sich ziehen, als auch Online-Messverfahren die nicht den technischen Anforderungen hinsichtlich Genauigkeit und einer kurzen Messdauer entsprechen, stellen aktuell die einzigen Messmethoden zur Bestimmung der Schmierölverdünnung dar. Durch neue Entwicklungstrends bei Ottomotoren ist es jedoch unbedingt notwendig, die Mechanismen des Kraftstoffein- und -austrags in das und aus dem Motoröl genauer zu untersuchen. Mit der an der OTH Regensburg neu entwickelten Messtechnik wurde eine Vorgehensweise erarbeitet, mit der die zeitlichen Verläufe des Kraftstoffein- und -austragsverhaltens bei Ottomotoren quantitativ in kurzer Zeit bestimmt und optimiert werden können.
Especially at cold start and the warm-up operation GDI engines have an issue with oil dilution. Parameters such as injection timing and injection pressure impact the entry of fuel in the engine oil as well. With the adjustment of engine operating points to higher mean effective pressures resulting in downsizing concepts also an additional increase of fuel entry occurs. Fuel gets into the oil pan and is mixed with the engine oil so that the physical and chemical properties of the engine oil are changed. With the reduction of engine oil viscosity due to fuel entry a reduced lubricating effect can be caused. In the worst case damage to the engine occurs, To determine oil dilution online and offline measurement methods exist. A rather long analysis time in the laboratory is a disadvantage of the offline methods. Online methods are not correlating with technical requirements in terms of accuracy and a short measurement time. New trends in the development of gasoline engines require investigations of fuel in oil sorption and desorption processes. A new measurement technique which is developed at the OTH Regensburg enables to determine quantitative fuel in oil sorption and desorption processes. With this technique a procedure was generated to measure the oil dilution at gasoline engines and optimize them in a short time.
Entwicklung eines Experimentalsystems zur Validierung adaptiver Regelungen mit einem OEM-Steuergerät
(2014)
Im Rahmen des Kooperationsprojektes "ACES" (Integrated Adaption of Linear Controllers for Embedded Systems) ist ein Prüfstand zur Validierung adaptiver Regelungen entwickelt und aufgebaut worden, der das dynamische Verhalten eines Kfz-Antriebstrangs aufweist. Ziel ist es, verschiedene Adaptionsverfahren auf ihre Einsetzbarkeit in OEM-Steuergeräten, die im Automotive-Bereich auf breiter Basis verwendet werden, kostengünstig testen zu können. Das Problem der aktiven Schwingungsdämpfung in Kfz-Antriebssträngen mit unbekannten und veränderlichen mechanischen Parametern stellt eine Pilotanwendung dar. Ein leicht anpassbarer mechanischer Prüfstand dient hierbei als vereinfachtes Modell eines Antriebstrangs. Dieser ist Bestandteil eitles Experimentalsystems mit einer informationstechnischen Architektur, die einen Betrieb engebetteter Regelungssysteme auf verschiedenen Plattformen gestattet. Das flexible mechanische und informationstechnische Design des Experimentalsystems gestattet die Variation von Parametern der zu regelnden Applikation durch leicht austauschbare mechanische Komponenten und gezielte Einbringung von Störgrößen. Zudem kann die Berechnung der Regelungsarchitektur auf einem Industrie-PC oder einem Steuergerät erfolgen. Weitere Vorteile des entwickelten Experimentalsystems sind die Berücksichtigung von Effekten, die aus dem Verhalten realer Sensoren und der CAN-basierten Signalübertragung entstehen. Insbesondere der Einfluss von Wortbreite und Latenz übertragener Signale auf die Adaption von Regelungen kann mit Hilfe des vorgestellten Experimentalsystems eingehend untersucht werden.
A Practical Thermal Model for the Estimation of Permanent Magnet and Stator Winding Temperatures
(2014)
A thermal model for the determination of the temperatures of interior permanent magnets and stator windings is presented in this paper. The innovation of the model relies on one temperature sensor being located in the stator core of the machine. Such sensor is simple to implement in many applications such as traction or EV, where reliability is critical. The estimated stator winding and permanent magnet temperatures are determined by a simplified thermal lumped element network model with only two time constants. It is shown that the proposed thermal model is very robust due to the structure of the model and the measured stator core temperature. The distortion of the temperature estimates caused by the cooling circuit is inherently accounted for such that the model can be used for robust online prediction of temperatures. Experimental results based on a forced water-cooled interior permanent magnet synchronous machine setup are presented to validate the effectiveness of the presented model.
Abstract Electric machine theory and electric machine simulations models are often limited to three phases. Up to the Modelica Standard Libray (MSL) version 3.2 the provided machine models were limited to three phases. Particularly for large industrial drives and for redundancy reasons in electric vehicles and aircrafts multi phase electric machines are demanded. In the MSL 3.2.1 an extension of the existing FundamentalWave library has been performed to cope with phase numbers greater than or equal to three. The developed machine models are fully incorporating the multi phase electric; magnetic; rotational and thermal domain. In this publication the theoretical background of the machines models; Modelica implementation details; the parametrization of the models and simulation examples are presented.
Wie groß ist der Speicherbedarf in Deutschland in der weiteren Umsetzung der Energiewende? Welche Rolle spielen Batteriespeicher, Pumpspeicher, Power-to-Gas etc. im Kontext anderer Flexibilitätsoptionen auf den verschiedenen Netzebenen? Wie entwickelt sich der Markt für Batterien und Wasserstoff? In unserer Agora-Speicherstudie haben wir auch erstmalig den Begriff Power-to-X definiert und damit die bis dato entstandenen Begriffe Power-to-Gas, Power-to-Liquids, Power-to-Products, Power-to-Chemicals etc. zusammengefasst.
Investigation of running ductile fracture in gas transmission pipelines and the derivation of reliable crack arrest prediction methods belong to major topics in pipeline research. The yet available crack arrest criterion, known as the Battelle Two-Curve Method (BTCM), leads to reliable predictions up to grade X70 line pipe steels for which it has been validated. This includes specific limits in terms of mechanical properties, pressure and geometry. The application of this criterion to modern pipeline steels, i.e. especially grades X80 and beyond in combination with larger diameters and high pressure, has led to mispredictions of the BTCM. Hence, in order to ensure safe design of pipelines, new methods are required based on in depth knowledge and appropriate characterization of material resistance. This paper presents a procedure for the assessment of dynamic ductile fracture resistance based on combined experimental and numerical investigations. The procedure involves quasi-static and dynamic drop- weight tear testing (DWTT) on modified specimens with pre-fatigued crack for grades X65, X80 and X100 materials, and the application of cohesive zone (CZ) and Gurson-Tveergard-Needleman (GTN) models to describe ductile material damage. The damage model parameters are calibrated on basis of DWTT results and subsequently used to simulate dynamic crack propagation in a pipeline. The influence of material properties (strain hardening, toughness), pipe geometry, usage factor and decompression behaviour on ductile fracture propagation behaviour is studied and evaluated. The results will contribute to an enhanced understanding of major parameters controlling ductile fracture propagation and will help to establish a reliable procedure for safe design of new high-capacity pipelines with regard to crack arrest.
Im Kontext der Energiewende sind Energiespeicher ein zentrales technisches, wirtschaftliches und energiepolitisches Thema.Die Autoren dieses kompakten Werkes geben einen umfassenden Uberblick Uber die verschiedenen Aspekte der Energiespeicherung. Sie beschreiben zunachst die Bedeutung von Energiespeichern in der Energieversorgung und definieren ihre Rolle darin. Dann gehen sie auf den Speicherbedarf in der Strom-, Warme- und Kraftstoffversorgung im Kontext der Energiewende ein. Im Hauptteil werden die verschiedenen Speichertechnologien ausfUhrlich vorgestellt sowie ihre Vor- und Nachteile diskutiert. Praktische Anwendungsbeispiele und die Integration von Speichern Uber alle Energiesektoren hinweg runden das Buch ab. Zahlreiche Grafiken und Beispiele veranschaulichen das gesamte Feld der Energiespeicher und sind als Erganzung samt Animationen online in Farbe verfUgbar.Die ZielgruppenDas Lehr- und Fachbuch wendet sich an Ingenieure, Wissenschaftler, Energieplaner und Energiewirtschaftler in Forschung und Industrie sowie an Studierende an Hochschulen und Universitaten in den Bereichen Maschinenbau, Verfahrenstechnik, Elektrotechnik und Energietechnik.
In future energy systems with high shares of fluctuating renewable energy generation, electricity storage will become increasingly important for the utilization of surplus energy. The Power-to-Gas (PtG) technology is one promising option for solving the challenge of long-term electricity storage and is theoretically able to ease situations of grid congestion at the same time. This article presents the perspectives of PtG in an 85% renewable energy scenario for Germany, quantifying an economic optimum for the PtG capacity as well as an optimized spatial PtG deployment.
Kostenminimaler Netzanschluss einer 8-MW-PV-Anlage mithilfe regelbarer Ortsnetztransformatoren
(2014)
Die steigende Anzahl der Erzeugungsanlagen (EZA) in den Verteilnetzen zwingt viele Verteilnetzbetreiber zum kostenintensiven Netzausbau. Dabei sind die EZA gemäß EEG am technisch und wirtschaftlich günstigsten Verknüpfungspunkt anzuschließen. Zur Bestimmung dieses Punktes ist ein Vergleich sinnvoller Netzanschlussvarianten durchzuführen. Regelbare Ortsnetztransformatoren (RONT) erweitern seit Kurzem die Netzanschlussmöglichkeiten, auch auf Mittelspannungsebene. Das Beispiel eines Anschlusses für eine 8-MW-PV-Anlage zeigt, dass der optimale Netzanschluss eine Kombination zwischen RONT, Spannungsblindleistungsregelung, Trennstellenverlagerung und Leitungsverstärkung sein kann. In diesem Fall bemerkenswert ist, dass der RONT-Einsatz die Netzanschlusskosten um rd. 60 % gegenüber einer separaten Anbindung am Umspannwerk reduziert. Die Autoren beschreiben eingangs die Problematik hoher Netzausbaukosten beim Anschluss von Photovoltaik-Flächenanlagen. Das Vorgehen der durchgeführten Netzanalyse im konkreten Fall (Abb.: Grafische Darstellung des südlichen MS-Netzes der Stadtwerke Kehlheim mit angedeuteter Einspeiseleistung) und die 6 analysierten Netzanschlussvarianten werden beschrieben und diskutiert (Abb.: Gegenüberstellung der Investitionen der verschiedenen Netzausbauszenarien). Die oben genannte günstigste Anschlussvariante besteht aus folgender Kombination: Verlegung der vorhandenen Netztrennstelle zwischen zwei 20-kV-Stränge; Verstärkung einer bestehenden Freileitungsstrecke über 1 km; Einsatz von maximal 15RONT sowie Spannungsblindleistungsregelung durch die PV-Flächenanlage.
Die Liberalisierung der Blindleistung und Schaffung von regionalen nicht ausschreibungspflichtigen Q-Beschaffungsprozessen ermöglicht vor allem künftig erhebliche Kostenreduktionspotenziale. Allerdings ist die Etablierung mit umfangreichen Eingriffen in den heutigen Normen- und Gesetzesrahmen verbunden. Damit diese Potenziale gehoben werden können, bedarf es einerseits der Möglichkeit der Kostenanrechnung im Rahmen der Netznutzungsentgelte, andererseits eines Anreizsystems, sinnvoll und sorgsam mit Q umzugehen. Grundsätzlich ist vorher gründlich zu untersuchen, ob und ab welchem Zeitpunkt die Liberalisierung der Blindleistung zielführend ist und wie im Detail die Liberalisierung der Blindleistung auszugestalten wäre.
Verteilungsnetzbetreibern stehen mittlerweile viele Maßnahmen zur Behebung des Spannungsbandproblems zur Verfügung. Innovative Konzepte wie der regelbare Ortsnetztransformator werden in vielen Pilotprojekten erprobt. Unklar ist jedoch noch, welche Maßnahmen beziehungsweise Kombinationen langfristig wirtschaftlich am günstigsten sind. Die Ostbayerische Technische Hochschule Regensburg untersucht daher in einem Forschungsprojekt verschiedene Maßnahmen, um sie unter wirtschaftlichen, technischen und energetischen Gesichtspunkten bewerten zu können. Der Beitrag untersucht am Beispiel des Netzmodells eines Dorfnetzes mit zahlreichen Photovoltaikanlagen unterschiedliche Szenarien für die Spannungshaltung, wobei u. a. Maßnahmen wie die Parallelverkabelung, das Einspeisemanagement durch Spitzenlastkappung, die Spannungs-Blindleistungsregelung durch die Erzeugungsanlagen sowie ein RONT (regelbarer Ortsnetztransformator) betrachtet werden. Dabei zeigt sich, dass es keine Maßnahme gibt, die in allen Belangen die günstigste Lösung ist. Es zeichnet sich jedoch ab, dass der RONT in vielen Fällen (abhängig vom Durchdringungsgrad) die günstigste oder zumeist eine günstige Lösung zur Erhöhung der Netzanschlusskapazität darstellt.
The worldwide growing energy demand with the exploration of new gas fields has promoted the development of high toughness seamless pipeline steels which should sustain the increasing demands resulting from the complex loading situations. One of the most important prerequisites for safe installation and operation of long distance gas transmission pipelines is the detailed knowledge and characterization of their fracture performance for specific applications. However, recent industry experience has revealed concerns related to the limitations and reliability of current test methods for brittle-to-ductile transition evaluation. Regarding the transition temperature evaluation, the critical issues involve Drop-Weight Tear Testing (DWTT) and full-scale West-Jefferson (WJ) test applied to the smaller pipes with diameter less than 500mm. The DWTT leads frequently to invalid results in terms of abnormal fracture appearance and inverse fracture occurrence. It is still not clear if this behavior is only owed to a testing effect, which material characteristics cause it and how far it reflects the full-scale behavior. Similar observations were made for the West-Jefferson tests, which could not be assessed in the standard manner either. Again, the question was towards testing effects and the behavior of the pipeline transporting gaseous media remains unanswered. Therefore, this paper aims at identifying open questions on basis of a literature study and own experimental results and showing possible ways forward in demonstrating safety in design against propagating fracture.
Assessment of collapse resistance of UOE pipes – comparison of full-scale and ring collapse tests
(2014)
Fracture propagation control in gas transmission gas pipelines belongs to the major design requirements for safe operation at high internal pressures. However, the current tests such as Drop-Weight-Tear Test (DWTT) and full-scale West-Jefferson (WJ) test reach the limits of their applicability with respect to transition temperature evaluation for seamless quenched and tempered small diameter pipes reflecting nowadays alloying concepts related to mechanical properties. Hereby, different geometry and material effects are evident which might lead to misinterpretation and unreliability of testing results. This paper aims to discuss open issues addressed in the literature and in own experimental findings with respect to reliability and transferability of testing methods, fracture parameters and their representativeness of seamless quenched and tempered pipeline behavior. By applying damage mechanics approach, it is possible to quantify the prevailing stress state and thus to understand the mechanisms controlling specific fracture appearance (ductile or brittle). Furthermore, studies were performed with objective to quantify the effect of different parameters (geometry, material and loading) on the fracture performance of the pipeline. The results from these investigations will serve as a basis for a safe pipeline design against propagating fracture.
Simulation is an indispensable tool for the engineering of systems containing electric drives. Depending on the design phase and the engineering task different levels of modeling details are required: proof of concept; investigation of energy and power consumption; design of control; etc. The new EDrives library provides three levels of abstraction for inverters: quasi static (neglecting electrical transients); averaging (neglecting switching effects) and switching – for serving different demands. The inverters can feed the machine models of the Modelica Standard Library: Modelica.Magnetic.FundamentalWave and the new Modelica.Magnetic.QuasiStatic.FundamentalWave. The EDrives library copes with arbitrary phase numbers and can be easily extended to develop new control algorithms. In this publication the structure of the library and the implemented control principles are presented. Furthermore; examples comparing the three different levels of abstraction are included.
Dieses Lehrbuch vermittelt nicht nur Grundlagen, sondern stellt auch die Methoden der Mehrkörpersimulation anschaulich dar und erläutert an einfachen Beispielen die Vor- und Nachteile bei der praktischen Anwendung. In den Text integrierte Matlab-Skripte und -Funktionen verdeutlichen die einzelnen Methoden und ermöglichen es, Aufwand und Problematik bei der Umsetzung der Theorie innerhalb von Simulationsprogrammen einzuschätzen. Die Modellbildung, die mathematische Beschreibung und die numerische Simulation von Systemen starrer Körper bilden dabei die Schwerpunkte. Konkret behandelte Beispiele sind die Eigendynamik eines Traktors mit gefederter Vorderachse, das Rotorblatt eines Hubschraubers sowie die Vorderachse eines Pkws. Die entsprechenden Matlab-Skripte und Lösungen zu den Übungsaufgaben können auf der Springer-Homepage beim Buch heruntergeladen werden. Der Inhalt Dynamik des starren Körpers - Bewegungsgleichungen - Starre Körper mit elastischen und kinematischen Verbindungselementen - Integrationsverfahren - Rekursiver Algorithmus - Differential-Algebraische Gleichungen - Analyse von Mehrkörpersystemen - Anwendungs- und Übungsbeispiele aus der Technik Die Zielgruppen Studenten des Maschinenbaus, der Elektrotechnik und Mechatronik sowie der Biomechanik an Hochschulen und Universitäten Ingenieure in der Praxis, die sich mit Fragestellungen der Mehrkörpersimulation (MKS) befassen Entwickler aus der Kfz-Technik sowie Fachleute aus F+E Die Autoren Dr.-Ing. Georg Rill ist Professor mit den Lehrgebieten Technische Mechanik, Ingenieurinformatik, Fahrdynamik, Mehrkörperdynamik sowie Laborleiter Fahrdynamik. Dr.-Ing. Thomas Schaeffer ist Professor mit den Lehrgebieten Konstruktion, CAD, Maschinenelemente und Getriebetechnik, Mehrkörpersysteme und Bewegungstechnik sowie Laborleiter Mehrkörpersimulation, beide an der Ostbayerischen Technischen Hochschule (OTH) Regensburg.
Analysis of dynamic ductile fracture propagation in pipeline steels: a damage-T IS A WELL-ESTABLISHED fact that the successful application of new generation of high-strength steel grades for long-distance gas transmission depends strongly on full understanding and appropriate characterization of fracture resistance. A damage mechanics approach has found to be a very promising tool in supporting the experimental characterization of ductile fracture propagation. The major advantage of this approach lies in the consideration of the influence of local stress and strain variables on the damage evolution and thus its capability to describe the fracture resistance of the pipelines with different stress triaxiality level by using the same set of parameters. However, the wider application of this approach has been limited due to the issues such as reliable determination of input parameters and required material properties, mesh size dependence, etc..
The objective of this paper is to characterize dynamic ductile fracture resistance of X65 and X80 pipeline materials and to demonstrate the potential of damage mechanics approach for the simulation of dynamic fracture propagation by using two damage models: (1) Cohesive Zone (CZ) model and (2) Gurson-Tvergaard-Needleman (GTN) model. In the first step, results from quasi-static and dynamic tensile tests are used to describe plasticity in terms of flow curves. The calibration of input parameters for both models is performed by using the load-deformation curves from quasi-static tests on non-standard drop-weight tear (DWT) specimens with pre-fatigued crack. b. In the next step, estimated damage model parameters are verified by means of the dynamic tests on the pressed and Chevron notch DWT specimens. Different amounts of crack growth are established by varying the drop height. The experimental fracture resistance is quantified in terms of J-integral at specific crack length. The numerical results are evaluated with respect to global load-deformation and fracture resistance behavior. Furthermore, damage simulations are applied for quantification of local stress conditions in order to identify the major factors controlling the crack propagation. The results reported here serve as a basis for better understanding of fracture performance in dependences of geometry and material properties.
Fracture behavior of seamless pipeline material X65Q acc. to API 5L has been studied both experimentally and numerically at different loading conditions (quasi-static vs. dynamic) and temperatures. The recent findings have shown difficulties in applying well established methods for determination of transition behavior or prediction of ductile crack arrest for the new generation of high-toughness steels. The irregular fracture performance (e.g. so-called "abnormal inverse fracture" appearance, significant scattering in ductile-to-brittle-transition-temperature region, etc.) suggests that the influence of pipe dimensions, loading parameters, crack initiation resistance as well as testing procedure on the fracture behavior has been neither understood nor properly described. This work aims to shed light on these questions regarding the applicability of conventional methods and to better illuminate most relevant parameters affecting fracture behavior of high toughness steels. To achieve this goal, experimental data basis for analysis of fracture behavior in transition and upper shelf regime has been established by conducting quasi-static fracture mechanics tests and dynamic tests on Battelle Drop Weight Tear (BDWT or DWT) specimens at different temperatures. The evaluation of obtained test results in upper shelf has been additionally complemented by numerical simulation of damage behavior. The results highlight the influence of stress conditions on fracture behavior with reference to pipe dimensions and loading conditions and, subsequently, may be used as a basis for revision of existing design methods.
Die Arbeit befasst sich mit der Ladung von Elektrofahrzeugen durch Solarenergie in einem Inselsystem. Diese Art der Ladung entlastet die Netze und hat einen sehr hohen Leistungswirkungsgrad. Es wurde ein Prototyp einer Direkt-ladestation gebaut, welche verschiedene Elektrofahrzeuge mit einem neuartigen Verfahren aufladen kann. Sie enthält einen optionalen Pufferakkumulator und einen Vollbrücken-Gegentaktwandler für die Ladung bei schlechter Solarleistung. Ein Teil der Arbeit behandelt ausführlich die Auslegung, die Komponenten und bisher undokumentiertes Verhalten von Gegentaktwandlern. Des Weiteren wird das Prinzip der Solardirekt-ladung und deren Umsetzung sowie die Umsetzung des Gesamtsystems beschrieben. Es folgt ein Kapitel zur Wirtschaftlichkeit der Solardirektladung mit Handlungsempfehlungen. Insgesamt lässt sich schließen, dass Solardirektladung bei nutzungsorientierter Auslegung der Anlage und langer Laufzeit wirtschaftlich ist.
This work addresses the charging of electric vehicles with solar power in an off-grid system. Charging this way reduces the stress on the grid and has a very high power efficiency. A prototype of a direct charging station was built which is able to charge several different electric vehicles in a novel way. It includes an optional buffer battery and a full bridge converter for being able to charge electric vehicles at times o flow solar power. One chapter explains in detail the design, the components and so far undocumented properties of full and half bridge converters. The principle and the implementation of direct solar charging and the implementation of the whole system is described. The last chapter covers the cost effectiveness of solar chargin gas well as recommendations. All in all it can be stated that solar direct charging is ecomomically advantageous if it is projected according to the user’s demand.
This paper presents novel experimental methods for verification of both hydrothermal and mechanical stabilities of adsorbent coatings. Experiments have been carried out on zeolite-based coatings over aluminum substrates, prepared by a dip-coating technique developed at CNR-ITAE. Hydrothermal aging of several adsorbent coatings is ongoing. Adsorption and structural stability of some samples under test was successfully verified after 35000 aging cycles by isobars measurement and XRD analysis. Mechanical properties of coatings have been evaluated by applying different typologies of static and dynamic mechanical stresses. Results obtained have been compared with those achieved by subjecting adsorbent coatings prepared by Mitsubishi Plastic Incorporation (MPI) to the same characterization protocol. The comparison between the two types of coating returned that MPI coatings posses similar thermal stability and better mechanical strength than CNR-ITAE coatings.
Water vapor adsorption kinetics on small and full scale zeolite coated adsorbers; A comparison
(2013)
A possibility to enhance both heat and mass transfer characteristics of an adsorber heat exchanger is to apply the adsorbent directly to its surface in form of a consolidated layer. As the majority of the available publications on the effect of both coating technology and adsorbent layer thickness on the adsorption kinetics deals with small scale adsorbent samples, the results obtained can only represent the best case design of an adsorber heat exchanger. This article presents, therefore, a comparison between the adsorption kinetics of water vapour on small as well as two different full scale coated adsorber heat exchanger types with AQSOA-Z02 layers of Mitsubishi Plastics Incorporation under quasi isobaric conditions of adsorption heat pumps. The small scale coated samples have a zeolite dry mass of 200 mg and layer thicknesses of 200, 300 and 500 μm while the full scale adsorbers have a coated zeolite mass between 1.5 and 2.5 kg and layer thicknesses of 150, 200, 300, 400 and 500 μm. In the investigated adsorption heat pump module, up to 52.7 and 57.3% of the equilibrium differential water loading measured with the small scale coated substrates have been obtained after an adsorption-evaporation times of 300 and 600 s, respectively.