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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)
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.
Dynamical Investigation of Crawling Motion System based on a Multistable Tensegrity Structure
(2018)
The basic idea of this article is the utilization of the multistable character of a compliant tensegrity structure to control the direction of motion of a crawling motion system. A crawling motion system basing on a two-dimensional tensegrity structure with multiple stable equilibrium states is considered. This system is in contact with a horizontal plane due to gravity. For a selected harmonic actuation of the system small oscillations around the given equilibrium state of the tensegrity structure occur and the corresponding uniaxial motion of the system is evaluated. A change of the equilibrium state of the tensegrity structure yields to novel configuration of the entire system. Moreover, the motion behavior of the novel configuration is totally different although the actuation strategy is not varied. In particular, the direction of motion changes. Therefore, this approach enables a uniaxial bidirectional crawling motion with a controllable direction of motion using only one actuat or with a selected excitation frequency.
Technologies status and perspectives of Power-to-Gas in connection with seasonal underground storage
(2019)
Durch das in Paris beschlossene Ziel, die globale mittlere Temperatur auf deutlich unter 2 Grad Celsius gegenüber dem vorindustriellen Niveau zu begrenzen, ist ein Ausstieg aus der Nutzung fossiler Energieträger und Rohstoffe bis zum Jahr 2050 notwendig (WBGU 2016).
Daher hat sich die Bundesregierung das Ziel gesetzt, bis zur Mitte des Jahrhunderts eine weitgehende Treibhausgasneutralität zu erreichen. Hierzu ist neben einer Steigerung der Energieeffizienz in allen Sektoren ein Ausbau erneuerbaren Energien notwendig. Dies beinhaltet hauptsächlich den Zubau von Wind‐ und Solarstromanlagen. Somit gewinnt die Sektorkopplung immer mehr an Bedeutung und wird in Zukunft eine tragende Rolle für die Defossilisierung des Energiesystems spielen (BMUB 2016). Als zentrales Element der Sektorkopplung gilt Strom, der über Power‐to‐X (PtX) sowohl energetisch im Wärme‐, und Verkehrssektor als auch stofflich in der Industrie und vor allem im Chemiesektor eingesetzt werden kann (Ausfelder et al. 2018a). Im Rahmen des P2X‐Vorhabens der Kopernikus Forschungsinitiative wird die Sektorkopplung durch die Umwandlung von Strom mittels elektrochemischer Prozesse in stoffliche Ressourcen wie Wasserstoff, Synthesegas oder Kohlenstoffmonoxid untersucht. Der Schwerpunkt liegt auf der Betrachtung der Kopplung von Strom und Verkehr sowie Strom und Chemie und der Untersuchung von Prozessen und Pfaden, die aus ökologischer, ökonomischer und gesellschaftlicher Sicht vorteilhaft sind. Eine vergleichende Einordnung in den Gesamtkontext der Energiewende mit Abwägung zahlreicher Alternativen und Konkurrenztechnologien ist dort allerdings nicht vorgesehen. Zudem werden einige relevante PtX‐Technologien wie Power‐to‐Heat nicht betrachtet. Aus diesem Grund wurden in SPIKE ergänzende PtX‐Technologiepfade aus systemanalytischer Sicht untersucht. Dies sind Power‐to‐Heat (PtH) und Power‐to‐Gas (PtG) über Elektrolyse und optionaler anschließender Methanisierung sowie die Herstellung ausgewählter Pfade der strombasierten Herstellung von Produkten der energieintensiven Industrie. Ziel des Forschungsvorhabens war die Analyse von PtX‐Technologien und Pfaden, deren vergleichende Einordnung im Gesamtkontext der Energiewende sowie die Unterstützung des P2X Roadmapping Prozesses und die Ableitung von Handlungsempfehlungen. Ein besonderer Schwerpunkt lag auf dem Einsatz von PtX im Industriesektor. Für das Vorhaben wurden Arbeitspakete (AP) erstellt, die Untersuchungen zu Technologie, Potenzial, Ökonomie und Ökologie von PtH (AP 1), PtG (AP 2), Power‐to‐Ammoniak, Power‐to‐Ethen und Power‐to‐Propen (AP 3) umfassten. Daraus wurde in AP 4 ein Systemvergleich mit Einordnung von PtX in die Energiewende durchgeführt. Auf dieser Basis und der Identifizierung regulatorischer Rahmenbedingungen für PtX (AP 5) wurde das deutsche Energiesystem samt PtX‐Pfaden in einem Energiesystemmodell abgebildet (AP 6). Die Ergebnisse flossen in das Roadmapping ein (AP 7). Zudem erfolgte ein Austausch mit den Projektpartnern und das Verfassen wissenschaftlicher Abhandlungen (AP 8).
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.
Diese Arbeit befasst sich mit automatisierten Netzplanungsprozessen und gibt einen kurzen Einblick in das Entscheidungsunterstützungssystem, welches im EU-Projekt CrossEnergy entwickelt wird. Detaillierter wird aber auf die Konzipierung und Umsetzung eines automatisierten Einsatzes der Blindleistungsregelung von dezentralen Erzeugungs analgen eingegangen, die als spannungshaltende Netzausbaumaßnahme zur Verfügung stehen. Die vorgestellten Methoden und Algorithmen fokussieren sich auf die Q(U)- und coscp(P)-Regelungsarten.
This paper presents a digitalized concept for teaching control theory as minor subject with an integrated approach for lectures, exercises and practical sessions and first results of the implementation at the department of electrical engineering at the OTH Regensburg. The concept uses activating methods like blended learning and possibilities of digitalization of teaching implementing Just in Time Teaching and Peer Instruction. The base of the new concept is the idea of constructive alignment. Furthermore this paper presents the feedback of the students along with an accompanying scientific research over several semesters. The data obtained from the presented module are compared with the data from other blended learning approaches in Germany.
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.
This paper presents different options to provide reactive power in electricity grid systems. Since conventional power plants are being phased out and the reactive power demand tends to increase, alternative technologies are needed to cover it. reactive power sources are being defined and specified in this submission. A technical evaluation and an economic analysis of selected reactive power sources are carried out, based on interviews with manufacturers and operators. As well a multifactorial techno-economic comparison of the evaluated reactive power sources is presented. The technical analysis addresses reactive power control-ranges, stochastic parameters, lifespans, electrical losses and dynamics of re-active power sources. It states that power electronics allow faster setpoint changes than mechanical technologies can achieve, but at the same time this is associated with the highest electrical losses of the reactive power sources considered here. Considering the economic analysis, relative investment costs per reactive power of conventional compensation systems turn out to be the most cost-efficient. With regard to the multifactorial techno-economic comparison, it is im-portant not only to standardize on reactive power that can be provided, but also to include the additional system-relevant properties of technologies in the evaluation as well as the costs in operation.
Electric vehicles are one of the important components of the energy transition, which is necessary for the CO2 emission reduction. In order to estimate the influence of electromobility on electric grids at present day and in the future, the generation of realistic charge profiles is necessary. The main objective of this study is the development of an algorithm, which generates realistic charge time series of electric vehicles. The very huge and detailed input surveys enable to define different population groups, representing specific driving behaviour. These groups are then composed and scaled up, according to the statistical population structure of a chosen town or city in Germany, and show typical driving behaviour of all inhabitants. The charge profiles are calculated for several charge station types, based on daily electric vehicle user mobility, day type and household type. In addition, charge process occurrence is evaluated through a model, involving charge infrastructure presence, attractiveness of corresponding charge station type and charge process necessity.