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Solid oxide fuel cells (SOFCs) are highly efficient electrochemical energy converters. Currently, the main issues in SOFC system development are an increase the long-term stability and system efficiency. Therefore new sealing concepts for stacks are needed. The aim of this work was to develop a novel compressive composite gasket. The characteristics of leakage, thermal cyclability, and long-term chemical stability were studied at various operating conditions. An analytic model for the sealing mechanism with dependence of operating time, temperature, and normal load has been developed. The main property of the gasket is a layer of mica paper which remains elastic at SOFC operating temperatures. It is contained in a gas-tight encapsulation formed by two embossed steel sheets. For sealings between neighboring stack layers, an electrically insulating layer is still in development. To deliver the proof of concept for sealing concepts in stacks a test-bed was put into operation. The apparatus quantifies leakage fluxes within the stack and to the surroundings by mass flow measurements and mass spectroscopy. By performing ten stack tests, the proof of functionality for the test-bed was achieved, and mass balances were calculated for SOFC-stacks at any operating condition. Commercial feasibility of the composite gasket was demonstrated with an industrial partner. At manufacturing costs of £12/piece, a batch of 100 gaskets was produced in a semiautomatic process.

Thema der Arbeit ist die Analyse des Strömungsverhaltens in Einströmgehäusen und das Bestimmen der Leistungsverluste. Nach Erbringung des Eignungsnachweises für die Berechnung von Rohrströmungen und Einlassgehäusen mit dem Strömungslöser CFX wird gezeigt, dass durch den geschickten Einsatz poröser Medien die Genauigkeit der Berechnungen stark gesteigert wird. Die stromauf liegende und den Dampf zuführende Überströmleitung wird untersucht und deren Einfluss auf die Gehäuseströmung ermittelt. Anschließend werden Variationsrechnungen von Gehäuseformen ausgeführt, um den Einfluss der geometrischen Eigenschaften zu analysieren. Auch im spiegelgleichen Gehäuse kann sich eine asymmetrische Strömung einstellen. Daher werden die Eigenschaften der Gehäuse und der Einbauten auf ein der Asymmetrie entgegen wirkendes Verhalten hin untersucht. Die Ergebnisse werden auf ihren Einfluss auf die Anlagenleistung überprüft. Es wird Verbesserungspotential von bis zu 0.55 MW in einer 170 MW Turbine ermittelt.

The development of a novel resonance absorber is described. The vibrating elements of the "membrane absorber" are the perforation membrane, the air plug in the hole, the impermeable covering membrane with the air cushion enclosed in the chamber behind functioning as a spring. This complex resonator does not require any additional absorbing material to achieve a broad-band effect in the range of medium and low frequencies. Since the membrane absorber is hermetically sealed all around against its environment and has completely smooth outer surfaces, it is especially suitable for application in fields where high demands on hygiene conditions and fire protection, low frictional losses and small volume and weight are important. Silencer splitters completely made of stainless steel are described as an example for the application of the membrane absorber under harsh conditions in coal mines and air cleaning devices for industrial plants.