Real Application Conditions Research Articles

Evaporation Modeling of Water Droplets in a Transonic Compressor Cascade under Fogging Conditions

High-fogging is widely used to rapidly increase the power outputs of stationary gas turbines. Therefore, water droplets are injected into the inflow air, and a considerable number enter the compressor. Within this paper, the primary process of droplet evaporation is investigated closely. A short discussion about the influential parameters ascribes a major significance to the slip velocity between ambient gas flow and droplets. Hence, experimental results from a transonic compressor cascade are shown to evaluate the conditions in real high-fogging applications. The measured parameter range is used for direct numerical simulations to extract evaporation rates depending on inflow conditions and relative humidity of the air flow. Finally, an applicable correlation for the Sherwood number in the form of S h ( R e 1 / 2 S c 1 / 3 ) is suggested.

Evaluation of analytical model for magnetic field distribution in magnetizing fixture study

A simple analytical model for magnetic field of a circular current was evaluated for the case of 4-multilayer solenoid of single-pole magnetizing fixture. The exact solution of the analytical model was computationally simulated and presented as 2D spatial distribution of magnetic field strength as functions of applied current and the position of each single coil in the solenoid. The results were compared with experimental measurements performed on commercial magnetizing fixture in order to gauge the effectiveness of the model in real application conditions. Qualitatively, the model shows an excellent agreement to the general trend of spatial distribution of magnetic field patterns obtained from experimental data despite of a considerable percentage error between the model and experimental results.

About calculations of composite plate tensile failure in cross-section with bolt hole of single-shear bolted joint

Background. Bolted joints (BJ) are the main type of detachable connection. When designing the BJ with plates of layered composite material, there is a problem of calculating the BJ strength, in particular, the cross-sections weakened by the bolt hole. It is due to the complex nature of the interaction of the layers of the composite plate with each other and also with bolts, as well as the presence of a number of structural and technological parameters of the connection.Objective. The main task of this research is to find the functions of influence of the magnitude of the bolt / hole gap, also structure and secondary bending of the bolt and plate on the value of the generalized stress concentration coefficient (SCC) in the cross-sections with bolt hole of the layered carbon fiber reinforced plastic (CFRP) plate using the results of BJ numerical simulation.Methods. It was used a method of finite-elements and the 3D contact model as much as possible approached to real geometry and conditions of load application. Earlier, the authors created 24 3D models of samples of single-shear two-row bolted joint with CFRP (contact task), in which the structures of CFRP (6 variants) varied, as well as the bolt / hole gap (4 values). The magnitudes of bolt tightening force and the force that stretched the sample were unchanged. Based on the results of calculations, stress distributions were determined and values of SCC in CFRP plates in the bolt holes (tables, graphs) were obtained.Results. Based on these results and additional calculations, the following conclusions were reached:in the static calculation of composite plate tensile failure in cross-section with hole of single-shear bolted joint the upper value estimate of the theoretical SCC in the pin-loaded hole in the plate of orthotropic material can be obtained in accordance with the formula arising from the solution of EHS (Echavarrı’a, C., Haller, P. and Salenikovich, A).in order to obtain a generalized SCC , which additionally takes into account a number of factors of BJ with CFRP, the upper value estimate of the theoretical SCC must be multiplied by next factors:function of influence of the bolt / hole gap, structure and the secondary bending of the CFRP plate; - taking into account the interplay of CFRP layers. For the considered BJ with CFRP an evaluation was obtained ;Conclusions. There is an easy-to-use formula for the upper estimation of SCC in a pin-loaded bolt-hole in an orthotropic material plate. The functions of influence of the bolt / hole gap, structure, and bending of the CFRP plate at first approximation are linear. The refined value of the correction factor, which takes into account the interplay of the layers of the CFRP, should be obtained in additional experiments (physical or numerical).

Chips Classification for Suppressing Transient Current Imbalance of Parallel-Connected Silicon Carbide MOSFETs

This article addresses the influence of parameters spread on transient current distribution among parallel-connected silicon carbide (SiC) mosfet s and proposes a chips classification method to suppress current imbalance. A comprehensive comparison of parameter spread between silicon (Si) and SiC mosfet s is first presented. Then, a new classification criterion, referred to in this article as a distance coefficient of transfer curves (DCTC), is proposed to characterize device spread. In addition, the sensitivity analysis of transient current imbalance (TCI) to device spread is carried out. It is found that TCI increases almost linearly with increasing DCTC. Furthermore, a hierarchical cluster algorithm is developed to achieve an automated chips classification for multiple devices intended for paralleled application. This algorithm may as well facilitate the chip selection process for multiple-chip power module packaging. Moreover, the influence of operating temperature on classification is also discussed. It should be noted that chips classification needs to consider real application conditions and package parasitic. Finally, a test bench with a round layout is designed, to keep circuit layout asymmetry to a minimum, and used to experimentally verify the performance of the classification method. The experimental results validate the effectiveness of the proposed classification method for suppressing TCI.

Preparation and characterization of waste papers based composites and their applications in leather industries

In this work, the utilization of waste paper in the preparation of cellulous-based composite is described, with latex as a binder. Paraffin wax and acrylic woven fibers were also used at various weight ratios to get the best mechanical and physical properties. The results were compared with the performance the Dixon, regularly used material in shoes manufacturing. The following tests were performed: compression resistance, density, water absorption, shrinkage, and moisture content. Manual method was employed in the preparation of test specimens in addition to laboratory forging machine for finishing of the specimens. Results of compression test (Modulus of elasticity, compressive strength, resistance to crushing) of the Specimens that contain pulp paper and reinforced with latex and acrylic fibers and low content of paraffin wax showed the highest resistance to compression, The increase of additives contents within the mix resulted in an increase in density. To mimic the real application conditions of the insole, the specimens were subjected to water absorption test by irrigation for 2 hours. The best specimen compositions for the water resistance test are those with high (5-10%) wax content due to the fact that the wax is a water repellent material. The shrinkage is another important parameter for the use of the composite in shoe industry. Result of shrinkage and humidity of all specimens show comparable results to commercially available and Dixon are also very close to the requirements of the specification of leather industry. However, in comparison with the available carton and dixon, our specimens contain from weight fraction (50g) waste pulp, (20g) latex, (4g) paraffin wax, (0.7g) acrylic fibers, proved comparable performance.

Classification of hydrocolloids based on small amplitude oscillatory shear, large amplitude oscillatory shear, and textural properties.

Dynamic rheological and mechanical properties of seven commercial (xanthan [XG], guar [GG], high methoxylated pectin [HMP], κ-carrageenan [κ-Car], agar [AG], alginate [ALG], and carboxymethylcellulose [CMC]) and four emerging hydrocolloids (basil seed gum [BSG], sage seed gum [SSG], Balangu-Shirazi seed gum [BSSG], and cress seed gum [CSG]) were investigated and the classification of the hydrocolloids were carried out based on them. AG belonged to the first class with 0.81 membership function (MF), κ-Car and HMP grouped in the second class with 0.68 and 0.71 MFs, respectively, XG, BSG, and SSG were depended to the third class with 0.61-0.70 MFs, finally, CMC, GG, BSSG, ALG, and CSG related to the fourth class, as the most populated class, with MF > 0.61. The first class contained the highest amount of hardness parameter (43.40 ± 2.76 g), the second class included the highest pseudoplasticity parameter (shear-thinning ratio = -0.54 ± 0.03) and relaxation time (66.25 ± 2.61 s) and the fourth cluster comprised the highest frequency dependency of viscous modulus (exponent of power-law model for viscous modulus vs. frequency = 0.30 ± 0.05). In addition, the results of this study showed that there was a distinct relationship between nonlinear harmonics in the stress wave and fundamental characteristics of hydrogel networks. The investigation of the rheo-mechanical properties of biopolymers in large deformation under shear and normal forces can have an important role in the prediction of the behavior of the material in real processes and application conditions, especially in the food industry. Due to the inconvenience of large deformation mechanical tests, such as Weissenberg effect, the complication of the results analyzing and sampling difficulty of semi-dilute samples; herein, we determined the correlation between large deformation (LAOS and texture analysis) and small deformation (SAOS) tests properties. The studied rheo-mechanical parameters showed high correlation with the four mentioned network parameters (more than 65% similarity index). Using these results, other scientists could rationally design the experiments and avoid experiments with similar parameters.

Assessment of spray drift potential reduction for hollow-cone nozzles: Part 2. LiDAR technique

Pesticide spray drift poses health hazards to humans and causes a significant impact on the environment. In this work the capacity of an ad hoc light detection and ranging (LiDAR) system to differentiate spray nozzles according to their potential drift risk is evaluated for the first time. A total of 23 drift potential tests using 10 hollow-cone nozzles were carried out with the sprayer kept in a static position. Drift potential reduction (DPR) values of between 88.6% and 93.6% were obtained when comparing standard and drift reduction nozzle types. It was also possible to order different standard nozzle sizes according to their DPR. The LiDAR signal was correlated with several droplet size parameters measured by a phase Doppler particle analyzer (PDPA), being V100 the best indicator. In the four field tests that were performed, the LiDAR system was also able to differentiate between standard and drift reduction nozzles under real application conditions, obtaining a DPR of 56.7%. The results of this work demonstrate that the developed LiDAR system is an advantageous alternative for the assessment of drift potential reduction.

Robust RGB-D Face Recognition Using Attribute-Aware Loss.

Existing convolutional neural network (CNN) based face recognition algorithms typically learn a discriminative feature mapping, using a loss function that enforces separation of features from different classes and/or aggregation of features within the same class. However, they may suffer from bias in the training data such as uneven sampling density, because they optimize the adjacency relationship of the learned features without considering the proximity of the underlying faces. Moreover, since they only use facial images for training, the learned feature mapping may not correctly indicate the relationship of other attributes such as gender and ethnicity, which can be important for some face recognition applications. In this paper, we propose a new CNN-based face recognition approach that incorporates such attributes into the training process. Using an attribute-aware loss function that regularizes the feature mapping using attribute proximity, our approach learns more discriminative features that are correlated with the attributes. We train our face recognition model on a large-scale RGB-D data set with over 100K identities captured under real application conditions. By comparing our approach with other methods on a variety of experiments, we demonstrate that depth channel and attribute-aware loss greatly improve the accuracy and robustness of face recognition.

Rationally Designed PdAuCu Ternary Alloy Nanoparticles for Intrinsically Deactivation-Resistant Ultrafast Plasmonic Hydrogen Sensing.

Hydrogen sensors are a prerequisite for the implementation of a hydrogen economy due to the high flammability of hydrogen-air mixtures. They are to comply with the increasingly stringent requirements set by stakeholders, such as the automotive industry and manufacturers of hydrogen safety systems, where sensor deactivation is a severe but widely unaddressed problem. In response, we report intrinsically deactivation-resistant nanoplasmonic hydrogen sensors enabled by a rationally designed ternary PdAuCu alloy nanomaterial, which combines the identified best intrinsic attributes of the constituent binary Pd alloys. This way, we achieve extraordinary hydrogen sensing metrics in synthetic air and poisoning gas background, simulating real application conditions. Specifically, we find a detection limit in the low ppm range, hysteresis-free response over 5 orders of magnitude hydrogen pressure, subsecond response time at room temperature, long-term stability, and, as the key, excellent resistance to deactivating species like carbon monoxide, notably without application of any protective coatings. This constitutes an important step forward for optical hydrogen sensor technology, as it enables application under demanding conditions and provides a blueprint for further material and performance optimization by combining and concerting intrinsic material assets in multicomponent nanoparticles. In a wider context, our findings highlight the potential of rational materials design through alloying of multiple elements for gas sensor development, as well as the potential of engineered metal alloy nanoparticles in nanoplasmonics and catalysis.

Impedance Spectroscopy Based on Linear System Identification.

Impedance spectroscopy is a commonly used measurement technique for electrical characterization of a sample under test over a wide frequency range. Most measurement methods employ a sine wave excitation generator, which implies a point-by-point frequency sweep and a complex readout architecture. This paper presents a fast, wideband, measurement method for impedance spectroscopy based on linear system identification. The main advantage of the proposed method is the low hardware complexity, which consists of a three-level pulse waveform, an inverting voltage amplifier, and a general purpose analog-to-digital converter (ADC). A proof-of-concept prototype, which is implemented with off-the-shelf components, achieves an estimation fit of approximately96%. The prototype operation is validated electrically using known RC component values and tested in real application conditions.

Oxygen permeation studies in surface Pd-activated asymmetric Ce0.9Gd0.1O1.95 membranes for application in CO2 and CH4 environments

Oxygen Transport Membranes (OTMs) present a high potential for being considered in the integration of O2 supply systems in oxyfuel installations, as well as for the conduction of chemical reactions when operating Catalytic Membrane Reactors (CMRs). Several solutions are being prospected for overcoming the main drawbacks regarding materials stability and membrane performance. A highly stable material such as Ce0.9Gd0.1O1.95 (CGO) doped with 2% mol. Co was studied as a 40 μm-thick CGO supported CGO membrane. This membrane was characterized by studying its performance as oxygen permeation membrane for the production of oxygen under oxyfuel conditions and for the conduction of chemical reactions involving CH4. In order to improve oxygen surface reactions and consequently, the oxygen permeation, the membrane was surface activated with the addition of Pd nanoparticles. A broad characterization consisting of the study of O2 production under different environments simulating real application conditions was conducted by subjecting the membrane to Ar, CO2 and CH4 environments in the temperature range of 750 to 1000 °C. A peak oxygen flux of 7.8 ml·min−1·cm−2 was obtained at 1000 °C when using a sweep consisting of 75% CH4 in Ar. This flux corresponds to a 16-fold improvement in the O2 permeation at 1000 °C when sweeping with Ar, with an oxygen flux of 0.47 ml·min−1·cm−2. An oxygen flux of 1.2 ml·min−1·cm−2 was obtained at 1000 °C when feeding with pO2 = 1 atm in feed side. Membrane performance under CO2-containing environments showed a positive effect of CO2 on permeation at 1000–900 °C, reaching up to 0.59 ml·min−1·cm−2 O2 at 1000 °C. A continuous exposure of CO2 during 48 h at 750 °C resulted in a slight J(O2) increase, with a reversible reduction in performance when returning to clean conditions, thus demonstrating high stability of CGO membranes.

Antifungal and Photocatalytic Activity of Smart Paint Containing Porous Microspheres of TiO2

In this study, porous microspheres of TiO2 (µTiO2) were synthesized, characterized and incorporated into an acrylic paint formulation to obtain a photocatalytically active paint. In a novel approach, the antifungal properties of the µTiO2 paint were evaluated using Monascus ruber as the representative microorganism and compared to those of a photocatalyst-free paint. The photocatalytic activity of paint films was determined by methylene blue (MB) degradation under real conditions of application. High photocatalytic and antifungal activity was observed, with the microorganism culture showing the formation of growth inhibition halos, typical of materials that produce biocides that diffuse into the culture medium.

Verification of the reaction to fire of water-based and oil-based enamel paints used as finish of walls in residential buildings

Among that materials whose behavior facing fire has not yet been understood thoroughly lie paints used as finish of interior and exterior walls of buildings. This study aimed to analyses the reaction to fire of enamel paints exposed to elevated temperatures, so two paints were tested: one water-based and one oil-based, both applied over a white undercoat designed specifically for this purpose, simulating the real conditions of application. The paints were evaluated regarding their ignitability per ISO 11925-2:2010 and isolated combustion, by EN 13823:2010. Moreover, the enamels were subjected to thermogravimetric analysis with mass spectrometry to assess variations of mass during the temperature increase process. Lastly, a calorific value test was performed with the intent of comparing the values with those from the EN 13823:2010 test. It was noted that the paints evaluated, no matter their chemical composition, do not bolster the development of flames as they reduced smoke release by up to 6.7% and heat release by up to 60.4%, not hindering user safety in room under fire situation. Even more, the paints turned out to be protectors of the substrate Keywords: paints, finishing material, fire, building performance.

About calculations of bearing holes in a plate from a carbon fibre reinforced plastic a bolted joint

Purpose. In order to carry out calculations of net-tension failure of the weakened cross-section of bolted joints with CFRP, it is necessary to estimate the value of the generalized stress concentration factor at the hole. Methodology. Used a method of finite-elements and the 3D contact model as much as possible approached to real geometry and conditions of load application. Earlier, the authors created 24 3D models of samples of single-shear two-row bolted joint with CFRP (contact task), in which the structures of CFRP (6 variants) varied, as well as the side gap of bolts with holes (4 values). The magnitude of the contraction force of the packet and the force that stretched the sample were unchanged. Based on the results of calculations, stress distributions are determined in CFRP plates at the holes (tables, graphs) are calculated. Findings. Based on these results and additional calculations, the following conclusions were reached: - in static strength analysis of bolted joints on bearing have entered the correction function which parameters are characteristics of structure composite and bend factor; - the specified kind of correction function is necessary for receiving in additional researches (natural or numerical), that will allow to create a database for sizes of this function for actual variants in branch power bolted joints with composites. Originality. The possible algorithms for estimating the static tensile strength of bearing of bolted joints with CFRP are substantiated.

Influence of nitric oxide on the oxygen permeation behavior of La0.6Sr0.4Co0.2Fe0.8O3−δ perovskite membranes

• NO influence on oxygen permeation of perovskite membrane is probed. • The presence of NO would decrease the oxygen permeability below 900 °C. • The presence of NO can change the membrane surface. • NO influence can be avoided by lifting the operation temperature above 900 °C. Mixed conducting perovskite membrane has been intensively investigated as a possible new technology for oxygen production to replace the conventional cryogenic distillation which is capital and energy intensive. The perovskite membrane has the potential to be applied in the clean energy projects like oxy-fuel coal combustion if the membrane can withstand the real application conditions. Nitric oxide (NO) is an inevitable ingredient of flue gas from power plants, and it is important to understand the possible influence from NO on the perovskite membranes for producing pure oxygen for oxy-fuel project where the flue gas would be used as the sweep gas for the membrane operation. The influence of NO on the oxygen permeation properties of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF) perovskite membrane is investigated by a variety of characterization techniques. The results indicate that the oxygen permeability of the LSCF membrane decreases significantly at the temperature below 900 °C. XRD, SEM and SEM-EDX characterizations indicate the generation of another porous phase damaging the membrane and accounting for the oxygen flux decrease. However, the negative effect from NO on the oxygen permeation would disappear when the temperature is elevated above 900 °C, on which NO would be decomposed to nitrogen and oxygen and no longer negatively influences the membrane.

HARDWARE-SOFTWARE COMPLEX FOR TESTING OF BEHIND-THE-HORIZON RADAR STATIONS USING THE METHOD OF AUTOMATIC PASSIVE AIRSPACE SURVEILLANCE

The basis of the work of over-horizon radar stations is a jump mechanism of propagation of short-range radio waves, which involves the adaptation of the equipment to continuously changing geophysical and noise conditions. The review of the station’s area of responsibility is usually carried out sequentially at a number of frequencies. To assess the probability of correct detection of air objects and other characteristics of over-horizon radar stations, a comprehensive test simulation stand and an algorithm for assessing the current combat capabilities are used. A comprehensive simulation test stand to test and confirm compliance with the achieved characteristics of the station simulates different variants of the air situation in the field of view of the radar. It is proposed to use the technology to obtain the parameters of the routes of scheduled aircraft, which are equipped with dependent observation equipment, compare them automatically with the parameters of the finally detected route of the station and to evaluate the characteristics of over-horizon radar in real helio and geophysical conditions. Thus, the hardware and software complex for testing over-horizon stations for flight air objects using the method of automatic passive review of airspace, including outside the territory of the Russian Federation will allow to evaluate their tactical and technical characteristics in automatic mode, in real conditions of application.

Dowel connections securing roof-diaphragms to perimeter walls in historic masonry buildings and in-field testing for capacity assessment

In the seismic retrofit of existing masonry constructions, global interventions are often needed to inhibit the onset of local mechanisms and to engage the whole building box-like structural behaviour. Such interventions are represented by perimeter ties and roof and floor diaphragms. This paper considers the roof diaphragm strengthening solution and investigates the use of stud connections securing the roof thin-folded shell to the perimeter walls. Stud connections serve the dual purpose of collecting and transferring the out-of-plane inertia forces of the masonry walls to the roof diaphragm, as well as transferring the diaphragm reaction forces to the shear walls. Specific detailing of the stud connection and the adoption of an improved lime-mortar overlay on the top of the masonry walls are proposed to improve the connection strength; without such improvements, the connection capacity would be jeopardised by the reduced shear resistance of the masonry wall due to the absence of significant vertical confining action at the roof level. The intervention entirely changes the behaviour of the connection and significantly reduces shear stresses on the masonry wall. The structural behaviour of the connection is analysed and discussed. Emphasis is made on the conceptual design of laboratory and in-field test procedures and testing frames in order to replicate the boundary conditions in real applications. In-situ tests may help during the design of the roof thin-folded shell system and allow for the efficiency assessment of the connections prior to the final intervention, thereby proving the actual feasibility of the retrofit solution.

Comparative evaluation of fire resistance of partition wall blocks prepared with waste materials

Partition wall blocks produced by using recycled concrete as aggregates may be exposed to fire conditions in real applications. It is of great significance to keep the thermal conductivity of the block as low as possible to minimize damages due to the outbreak of a fire. To do so, alternative and/or additional materials can be used in the preparation of the blocks, which can reduce the heat transfer rate with little degradation of strength. In this study, three kinds of waste materials derived from construction and demolition (C&D) waste were respectively used to add or replace fine aggregates by volume or weight, including polypropylene fiber (PP fiber), recycled glass (RG) and recycled polystyrene (RP) in preparing the partition blocks. The compressive strength, water absorption, density, thermal conductivity, porosity of the blocks before and after exposure to elevated temperatures of 300 °C, 500°Cand 800 °C were examined. The results indicated that at room temperature, the incorporation of PP fibers had negligible influence on the physical properties of the blocks with little reduction of compressive strength, while the replacement of fine aggregate by RP resulted in significant reduction in compressive strength as well as thermal conductivity. The use of RG as a fine aggregate could reduce the thermal conductivity without significant effects on the compressive strength of the block samples. Although the exposure to elevated temperatures brought about reduction in thermal conductivity, the increase in porosity led to a large reduction in compressive strength of the blocks prepared with RP. The most significant finding of the study was that using 100% RG as fine aggregate was beneficial to conservation of compressive strength especially after exposure to 800 °C due to the re-solidification of the melted RG upon cooling, which led to a better thermal insulation property of the blocks. A further study on the influence of RG on compressive strength based on the mortar blocks prepared with glass cullet as fine aggregates convincingly proved the improved fire resistance of using 100% RG especially after 800 °C. The use of RG for partition blocks production has significant advantages in terms of sustainability and fire resistance.

BROADBAND ANTENNAS AND ANTENNA ARRAYS WITH REACTIVE LOADS

Results are presented on investigation of actual methods of extending the frequency range of dipole bent stub and loop antennas, as well as of antenna arrays on their basis. Optimum designs of broadband antennas with lumped reactive loads inserted in their arms are considered. The method of integral equations is applied to calculate the electrical parameters of the antennas that have made it possible to more thoroughly investigate new versions of broadband stub and loop antennas and antenna arrays. Two kinds of the antennas that are promising for application in the microstrip design as single antennas or as elements of antenna arrays are analyzed. The first kind is represented by a Z-shaped antenna of orthogonal linear polarization supplemented by lumped capacitive loads and the second one is a loop antenna with capacitive loads as well. To simulate the nearly real application conditions, the parameters of the antennas are determined for the case of their location at a small height above a conducting screen (plane). As a result of calculation of the electrical parameters of the Z-shaped antennas with capacitive loads and antenna arrays on their basis for the wide frequency range 0.9...1.2...2.7 GHz, a considerable improvement (decrease) of the voltage standing-wave ratio has been obtained. Specifically, its magnitude did not exceed 5 while for similar antennas without loads this parameter reach 30 and more. As compared with the conventional rectilinear antennas of the same length and stub thickness, the antenna gain at the central frequency of the analyzed range has increased from 7.8 to 9.8 dB with decreasing the voltage standing-wave ratio from 3.5 to 3.1. The voltage standing-wave ratio for the loop antennas with capacitive loads does not exceeds 5 within the same frequency range. The parameter magnitudes are less than 1.9 at the central frequency of the range, whereas for the antennas without loads this parameter is considerably greater (up to 30) with a relatively high magnitude (up to 15) at the central frequency of the range. Coplanar linear cophased antenna arrays consisting of three Z-shaped and three loop antennas with capacitive loads are investigated. It is shown that because of different relative location of the antennas in the arrays the voltage standing-wave ratios for the extreme antennas of the array differ from that of the central one. To provide the Z-shaped and loop antennas (as well as the antenna arrays on their basis) to operate in the nearly current traveling wave mode and, as a consequence, to reduce the frequency dependence of the input parameters and directional patterns of these antennas, it is sufficient to insert no more than four capacitive loads in the arm of a symmetrical antenna, in contrast to the known paper suggesting to insert several dozens of capacitive loads in the antenna arm.

Progress of SOFC/SOEC Development at DTU Energy: From Materials to Systems

DTU Energy has many years of experience in solid oxide fuel cell and electrolysis (SOFC/SOEC) research and development. Currently, the volume of SOFC/SOEC related projects exceeds 40 man-years per year. The main sources of financing are Danish R&D programs, counting for ~½ of all activities. In addition, activities are funded through European projects, commercial partners and finally from internal funds. The presentation will cover highlights from the SOFC/SOEC activities at DTU Energy, which span over a broad range in the value chain, from materials to cells, stacks and analyses at energy system level. These highlights also include progress of method development that supports SOFC/SOEC research such as ceramic processing methods, micro structural analysis, electro chemical characterization, and modelling. Recent achievements involve electrode development on Ni-free fuel electrodes with high carbon tolerance, redox stability, and tolerance towards impurities in the gas. Building on the concept of nanostructured fuel-electrodes, symmetric cells with zirconia based backbones were successfully prepared by freeze-casting and showed a small area specific resistance of ca. 0.012 Ohm cm2 at 650 oC after infiltration of nano sized ceria. DTU Energy has been among leading groups in the area of metal supported SOFCs. Our approach is based on a “co-firing” route utilizing ceramic manufacturing methods such as tape casting for the supporting metal layer. Recently the focus has been on developing a new cell concept that enables long term operation under conditions of high fuel utilization, where previous cell types have failed. Progress was achieved through micro structural optimization and use of an active and stable electrode material, LSFNT. Apart from development and improvement of fuel and electrolysis cells, comprehensive testing with the aim to understand the processes determining performance and durability has been carried out. Specific emphasis has been on matching real application conditions also in the lab. Such realistic conditions comprise both, the operating regimes – such as dynamic profiles (considering SOFC/SOEC applications in an energy system dominated by wind or solar power) – and the fuels – such as biogas. Biogas - a mixture of mainly methane and CO2 – is formed through anaerobic digestion of for example domestic or farming waste and is already produced at large scale throughout the world. SOFC allow for the direct use of biogas as fuel and offer the unique potential to produce electricity with high efficiency. Recently, a successful SOFC test was performed under dry reforming conditions, i.e. a mixture of a real biogas from a landfill unit and added CO2. With the SOFC technology approaching longer life times of thousands and tens of thousands of hours, durability testing for degradation analysis and life time prediction becomes more time consuming. Accelerated aging tests are therefore highly desired. DTU Energy has several activities in this area and has for example applied a new strategy for degradation analysis, recently. It was shown how the steam content determined by the inlet gas composition and the operating conditions current load and fuel utilization is one of the possible accelerating parameters for SOFC degradation. Also in the area of SOEC an extensive test program has been running over the past 10 years, including durability tests of several thousands of hours, both for steam and co-electrolysis of steam and CO2. This has involved test of various generations of cells, all based on a Ni/YSZ-structural support, but with different oxygen electrodes, as well as long term tests at stack level. Recent learnings on the impact of running cells in glavano static or potentio static regime and of the conversion degree will be presented. In electrolysis operation, the oxygen activity on the oxygen electrode will be higher than in fuel cell mode. This has an adverse effect on interconnect corrosion. The impact of oxygen activity on corrosion and performance of recently developed protective coatings will be presented. Finally, the importance of mechanical robustness for reliable operation of stacks shall be discussed based on newly acquired data on the mechanical properties of both cells and interfaces in the stack.