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The use of advanced pedagogical methodologies in connection with advanced use of modern information technology for delivery enables new ways of communicating, of exchanging knowledge, and of learning that are gaining increasing relevance in our society. Remote laboratory exercises offer the possibility to enhance learning for students in different technical areas, especially to the ones not having physical access to laboratory facilities and thus spreading knowledge in a world-wide perspective. A new “Remote Flutter Laboratory” has been developed to introduce aeromechanics engineering students and professionals to aeroelastic phenomena in turbomachinery. The laboratory is world-wide unique in the sense that it allows global access for learners anywhere and anytime to a facility dedicated to what is both a complex and relevant area for gas turbine design and operation. The core of the system consists of an aeroelastically unstable turbine blade row that exhibits self-excited and self-sustained flutter at specific operating conditions. Steady and unsteady blade loading and motion data are simultaneously acquired on five neighboring suspended blades and the whole system allows for a distant-based operation and monitoring of the rig as well as for automatic data retrieval. This paper focuses on the development of the Remote Flutter Laboratory exercise as a hands-on learning platform for online and distant-based education and training in turbomachinery aeromechanics enabling familiarization with the concept of critical reduced frequency and of flutter phenomena. This laboratory setup can easily be used “as is” directly by any turbomachinery teacher in the world, free of charge and independent upon time and location with the intended learning outcomes as specified in the lab, but it can also very easily be adapted to other intended learning outcomes that a teacher might want to highlight in a specific course. As such it is also a base for a turbomachinery repository of advanced remote laboratories of global uniqueness and access. The present work documents also the pioneer implementation of the LabSocket System for the remote operation of a wind tunnel test facility from any Internet-enabled computer, tablet or smartphone with no end-user software or plug-in installation.

AbstractThe electrodes are crucial components for fuel cells, since this is where the electrochemical reactions take place. In order to provide an insight into the structure/activity relationships of the rather complex electrodes, a high‐resolution measuring technique, based on a scanning tunneling microscope operating in an electrochemical cell, has been developed. The structure of the electrode surface can be imaged from the microscale to the nanoscale, under conditions quite close to those in a working fuel cell. The relative reactivity is measured by using the STM tip as a sensor electrode for the ORR. Here, the first results of the surface structure of the electrode materials are presented, as well as measurements of the local reduction current, related to the oxygen reduction reaction, giving a relative measure for the local reactivity.

The present work demonstrates that EC-AFM is a very useful new tool for identification and spatially resolved characterization of proton conductivity at the membrane surface in comparison with topography, however it does not provide insight into the 3D pore structure within the membrane. The results are consistent with those of conventional macroscopic measurements, confirming the reliability of the method. It will allow careful analysis of the homogeneity, the nature and the consequences of microphase separation as well as the effect of humidity on novel alternative membranes, and it will thus be essential for tailored developments of new materials for fuel-cell membranes. The present initial work is followed up with further experiments which provide a more complete understanding of the proton conductivity of the polymers, determine the influence of relative humidity on the size of conductive regions and investigate the reproducibility of the results.

Abstract In this paper the influence of pressure on the performance of solid oxide electrolysis cells is theoretically analyzed in a pressure range between 0.05 and 2 MPa. A previously validated electrochemical model of a solid oxide fuel cell stack is used to predict electrolysis behavior. The effect of pressure on thermodynamics, kinetics and gas diffusion is discussed. It is shown that thermodynamics are negatively influenced by an increase in pressure whereas kinetics and gas transport are improved. Overall pressure effects are therefore only small. At low current density the electrolysis cell shows better performance at low pressure whereas performance improves with pressure at high current densities.

Abstract A detailed computational model of a direct-flame solid oxide fuel cell (DFFC) is presented. The DFFC is based on a fuel-rich methane–air flame stabilized on a flat-flame burner and coupled to a solid oxide fuel cell (SOFC). The model consists of an elementary kinetic description of the premixed methane–air flame, a stagnation-point flow description of the coupled heat and mass transport within the gas phase, an elementary kinetic description of the electrochemistry, as well as heat, mass and charge transport within the SOFC. Simulated current–voltage characteristics show excellent agreement with experimental data published earlier (Kronemayer et al., 2007 [10] ). The model-based analysis of loss processes reveals that ohmic resistance in the current collection wires dominates polarization losses, while electronic loss currents in the mixed conducting electrolyte have only little influence on the polarized cell. The model was used to propose an optimized cell design. Based on this analysis, power densities of above 200 mW cm −2 can be expected.

In order to provide insight into the interfacial relationships at fuel cell electrodes, a measuring technique based on a scanning tunneling microscope working in an electrochemical cell has been developed. The structure of model electrodes consisting of carbon supported Pt and ionomer mixtures as well as MEA electrode surfaces is imaged by the electrochemical scanning tunneling microscope (EC-STM) from microscale to nanoscale. Images with subnanometer resolution are obtained indicating that some ordering of the particles on the carbon support is present in the model system and in the MEA. It is demonstrated that in both cases nanometer structures can be imaged reliably and that the interface is rather clean and active under reaction conditions. In addition, a technique has been developed to measure the local reactivity by using the STM tip as a sensor electrode for the ORR.

Abstract Polymer electrolyte membrane (PEM) fuel cells are a promising technology for automotive applications. To achieve the cost versus durability required for the commercialization of this technology, material production and its associated challenges have gained much interest. To reduce the production time per fuel cell stack, it is important to increase the number of units produced. A time-consuming step in the production of stacks is the activation, also known as break-in, which is necessary to carry out a subsequent factory-acceptance-test. The state-of-the-art studies found in literature are mainly tailored towards investigating various break-in procedures without taking into consideration the possible mechanisms behind the performance increase during the initial operation. This interconnection between break-in procedures and physical phenomena is hence missing. In this review, we describe the optimized state for the membrane and catalyst layer in regards to their morphology and composition. We compare this to the known state after production and discuss which mechanisms change the initial state. This information is then used to put into perspective the mechanisms that improve the cell performance and the time scale on which they will take place. Despite the high dependency of the activation behavior on the production steps and the material used, we can conclude that the main sluggish activation mechanisms for state-of-the-art CCMs are the removal of solvents from production and changes in the catalyst layer ionomer and at the membrane surface. Membrane bulk protonic conductivity and changes in platinum structure are expected to have a subordinate role in the activation process. High humidities or even liquid water in the cell and the cycling between oxidizing and reducing conditions at the electrodes accelerate the activation process. Thus, this review serves the development of “smart” and “fast” break-in procedures.