Recensies

Ingo Schmitz

Magere vorgemischte Verbrennung von leichtem Heizöl in Mikrogasturbinen: Grundlagen, Entwurf und experimentelle Untersuchung eines Brenner-/Brennkammersystems

Micro gas turbines are an interesting alternative for decentral power supply. The droplet size is a decisive factor in lean premixed combustion. In this process, substoichiometric air supply reduces the combustion temperature so that a minimum of thermal NOx will be produced. The compressor air must be distributed inside the combustion chamber so that stable and low-polluting combustion is ensured over a wide load range. Prior to the onset of combustion, the fuel must be mixed homogeneously with air in a premix section whose design should prevent self-ignition during mixing as well as flame backlash. In a specially constructed test stand, a combustion chamber designed on the basis of CFD calculations and theoretical considerations was tested under micro gas turbine conditions. During the first test phase, the influence of various constructive changes on pollutant emission was investigated. The effects of combustion chamber pressure and air preheating temperature on the emissions were assessed in a second test phase. It was found that both a pressure increase and a temperature increase will stabilize combustion in the direction of higher global air rates while the NOx emissions will increase slightly as a result of the higher combustion temperatures. On the basis of fundamental scientific investigations, it was possible to develop a MGT combustion chamber which meets the goals of low-pollution, low-cost and efficient power generation. In the load range of 40 - 100 percent, stable and low-polluting combustion was ensured, with NOx emissions below 25 ppm, CO emissions below ppm and 15 percent O2. The combustion chamber pressure loss is very low at 1.6 percent, as is the heat loss at 3.1 percent at the most. (orig.)

Quelle: ETDE - Energy Database-production no.:DE09GC142

Matthias Schmidt

Ein selbstadaptierender, dynamischer Energiemanagementansatz für das elektrische Kraftfahrzeugbordnetz

A substantial result of the contribution under consideration is the development of an energy management approach which can coordinate a small up to middle number of consumers, producers and storages and meets the vehicle-specific requirements. Thus, the self adaptation ability enables a simple handling with the variant variety. The dimensioning the size of the matrix enables a simple scaling of the System. It could be shown that not only the pure consumer management and battery management can be performed by means of the energy management approach but also well-known strategies such as the recupative generator management. This results in a saving of fuel and reduction of the emission of CO2.

Quelle: ETDE - Energy Database des Leibniz-Instituts für Informationsinfrastruktur (FIZ Karlsruhe), production no.: DE10GC095

Anja Wick

Untersuchungen zur Desaktivierung und Regeneration von Katalysatoren zur Wasserstofferzeugung für Brennstoffzellensysteme

A new natural gas fuelled 2kWe PEM domestic power supply system for a single-family dwelling was investigated. The work described in the publication comprised the characterisation, operating characteristics and long-term Performance of the catalysts for gas generation and purification. Purification is achieved by low-temperature conversion (single shift) followed by methanation in order to reduce the CO concentration to less than 30 ppm prior to entering the fuel cell. The service life should be similar to conventional heating technologies. The experimental and theoretical investigations of the catalyst stages suggest that both the steam reformer for gas generation and the single shift meet the requirements of the domestic power supply system. The methanation investigations suggested an activity decrease of the catalyst which resulted in higher CO concentrations that may damage the PEM fuel cell. The activity decrease may be explained in terms of carbon accumulation at the active catalyst cells which blocks their activity. In oxidation experiments, the adsorbed carbon could be removed completely from the catalyst surface below reaction temperature. In consequence, methanation can be used as the final gas purification stage if a regeneration phase is integrated in the process. Using a one-dimensional process model, the experimental results were modelled reliably both for the individual catalyst stages and for the overall system. Optimisation studies in the field of gas purification showed that the resulting CO concentration can be reduced even further by appropriate reaction control; this will also simplify the process and make the system more robust.

Quelle: ETDE - Energy Database des Leibniz-Instituts für Informationsinfrastruktur (FIZ Karlsruhe), production no.: DE10GC094

Jens Berkan

Modellierung des Schlepp- und Startverhaltens von Verbrennungsmotoren bei tiefen Temperaturen

The modelling of complex starting systems makes high demands on the accuracy and informative capability of the results. Thus, a calculation program is developed. The program is built up modular and expandable. Experimental investigations are performed at an air-conditioned system and component test stand. Simulation models for combustion engines are derived on the basis the experimental results. Beyond this, models for voltage supply are produced in form of lead acid batteries as well as double-layer condensers. The parametrization of the models is performed on the basis of the behaviour of new construction units. The different designs of electrical starter engines are illustrated in detailed models, whereby the emphasis lies on direct current machines being usually used today. Furthermore, an interface is programmed for the simulation of a combustion process and, thus, for the simulation of a complete starting procedure. The efficiency of this interface is demonstrated on the basis a simple combustion model. Complex starting systems in a very early development stage can be simulated and be evaluated regarding their dynamic behaviour.

Quelle: ETDE - Energy Database des Leibniz-Instituts für Informationsinfrastruktur (FIZ Karlsruhe), production no.: DE10GC460

Andreas Rau

Analyse und Optimierung des ottomotorischen Starts und Stopps für eine Start Stopp Automatik

In the background of an automatic start-stop function as a possible measure for the reduction of emissions of CO2 at motor vehicles, the author of the contribution under consideration examines the starting procedure and stop procedure of a internal-combustion engine. The author presents an optimization of the internal-combustion engine concerning to comfort, emission, costs and energy conversion. The analysis of the stop procedure shows that one can renounce on an optimization concerning emissions and energy. The relevant criterion is the stop comfort due to non-ignited compressions in the engine discharge. By controlling the pressure in the suction tube by means of suitable functions in digital engine electronics an optimization is reached concerning to comfort and costs.

Quelle: ETDE - Energy Database des Leibniz-Instituts für Informationsinfrastruktur (FIZ Karlsruhe), production no.: DE10GC101

Markus Reinhard

Permanentmagneterregter Synchronmotor mit integrierter Energieübertragung in das Läufersystem

A variety of applications requires electric power on a moving and especially rotating part. One example is the power supply of a measurement device on a rotating or moving part. Another example is the supply of energy to clump a tool on a direct driven spindle. Also the subsequent electric machines of multi axis industrial robots have to be powered. The thesis deals with the analysis, optimization, construction and measurement of a new electric machine with integrated contactless power transmission on the rotor system. Today´s technology uses contact or non-contact solutions. Contact solutions are slip rings and trailing cables. Non-contact solutions are ferrite transducers. These solutions have in common an additional component that has to be attached to the drive housing. Hence, additional construction space is necessary. In addition the complexity and the costs of the system will rise. Therefore it is reasonable to investigate solutions with integrated non-contact power delivery. With this contribution a concept is elaborated that features a motor with integrated contactless inductive power transmission. Problems like brush wear and broken trailing cables can be overcome. Both functions, drive and energy transmission, are completely independent. The hardware of both functions is separated, which means both functions feature their own hardware. There are two inverters and two windings sharing the same stator slots. Above this, the control of both functions is independent. The two functions may operate at the same time or alternating. Through the separated realization, the design process of the machine is simplified, the optimization of both functions can be done independently within specific limits. Also the operational reliability increases. The proposed motor is a permanent excited synchronous machine with one additional three-phase winding in the stator and one additional three-phase winding in the rotor for the energy transmission. The independence of both functions is gained by a appropriate choice of the winding parameters.

Quelle: ETDE - Energy Database des Leibniz-Instituts für Informationsinfrastruktur (FIZ Karlsruhe), production no.: DE10GC412

Thorsten Biermann

Entwicklung eines aktiven Fahrwerks für Gegengewichtstapler

Das Buch ist eine veröffentlichte Dissertation, die Thorsten Biermann im Fachbereich Maschinenbau der Helmut-Schmidt-Universität Hamburg erarbeitet. Innerhalb eines Forschungsprojekts wurde im Jahr 2008 für den Gegengewichtstapler R 70-30 der Marke Still ein aktives Fahrwerk entwickelt, das den Anforderungen an Fahrstabilität und Schwingungsdämpfung Rechnung trägt. Es wurden geeignete Achskonzepte, eine Hubgerüstlagerung sowie das Hydrauliksystem und die Fahrwerksregelung entwickelt. Das Buch gliedert sich in folgende Kapitel: Einführung; Konzeptentwicklung de Gegengewichtstaplers mit aktivem Fahrwerk; Auslegung des Fahrwerks; Simulationsmodell des aktiv gefederten Gegengewichtsstaplers; Entwurf der Regelung; Realisierung des Funktionsmusters; Fahrversuche; Zusammenfassung und Ausblick. Der Autor beschriebt zusammenfassend, dass durch ein aktives Fahrwerk bei Gegengewichtstaplern signifikante Verbesserungen der Fahrsicherheit - vor allem der dynamischen Kippsicherheit - und des Fahrkomforts erreichbar sind. Die gesamte Forschungsaufgabe, von der Konzeption über den ganzheitlichen Entwicklungsprozess bis hin zur Realisierung des Funktionsmusters, war für ihn in diesem Umfang nur durch den Konsequenten und intensiven Einsatz von Computer Aided Engineering (CAE)-Methoden lösbar. Eine weitergehende Optimierung, die vor allem die konstruktive Ausführung der Radaufhängungen und die Integration der Fahrwerkhydraulik in das Hydrauliksystem des Staplers betrifft, erscheint vielversprechend und möglich.

Quelle: Hebezeuge Fördermittel 10/2009

Ingo Kühne

Resonante mikromechanische Energiewandler

This work focuses on the investigation of resonantly driven micromechanical energy harvesters. They are based on electromechanically coupled spring-mass-systems, converting mechanical vibrations into electrical energy by employing appropriate physical transduction mechanisms, such as the inductive, the piezoelectric and the capacitive principle. These three approaches are compared to each other, especially with respect to electrical energy density, scaling behaviour and microtechnological fabricability. Theoretical considerations lead to the decision to implement both a capacitive and a piezoelectric micromechanical energy harvester. The capacitive energy transducer essentially consists of a mass suspended by silicon springs. This mass simultaneously serves as a movable electrode. A fixed counter electrode completes the variable capacitor. In order to function properly, the parallel-plate capacitor needs to be based electrically. In contrast to existing state of the art a new approach is introduced, employing two different electrode materials with a large difference in their work functions. A periodical mechanical excitation leads to a variation of the electrical energy content within the biased capacitor, thus inducing a current flow, which can be used for driving an external electrical load. For the piezoelectric energy harvester, the concept of a piezoelectric diaphragm with a mass attached to the surface was used and devices were implemented. A mechanical excitation leads to a periodic deflection of the diaphragm caused by the stiffly coupled inertial mass and, thus, to a changing mechanical stress distribution within the diaphragm. This, in turn, induces a periodic charge separation within the piezoelectric diaphragm. The energy generated in this way can be consumed by an external electrical load with appropriate impedance matching. Theoretical model descriptions are established for both types of energy harvesters based on systems of state space equations. On the basis of these models appropriate concepts for the realisation of the energy harvester with MEMS technology are conceived. The capacitive energy transducer consists of a stack of three hermetically bonded wafers (Pyrex-SOI-Pyrex, 100 mm). The piezoelectric energy harvester is manufactured on standard 150 mm wafers. Finally, both types of energy harvesters are characterised by means of impedance measurements and by comprehensive shaker tests. The results prove the functionality of the developed energy harvesters and verify the validity of the respective model description.

Quelle: Rezension: 09.11.2009 ETDE - Energy Database des Leibniz-Instituts für Informationsinfrastruktur (FIZ Karlsruhe), production no.: DE09GA154