New TRNSYS types to simulate air-to-air energy recovery

Presentation on new TRNSYS types to simulate air-to-air energy recovery. Implementation of energy conservation measures in buildings can extend our use of finite resources while simultaneously reducing our impact on the environment

Adult age differences in monetary decisions with real and hypothetical reward

Age differences in monetary decisions may emerge because younger and older adults perceive the value of outcomes differently. Yet, age‐differential effects of monetary rewards on decisions are not well understood. Most laboratory studies on aging and decision making have used scenarios in which rewards were merely hypothetical (decisions did not have any real consequences) or in which only small amounts of money were at stake. In the current study, we compared younger adults' (20–29 years) and older adults' (61–82 years) decisions in probabilistic choice problems with real or hypothetical rewards. Decision‐contingent rewards were in a typical range of previous studies (gains of up to ~4.25 USD) or substantially scaled up (gains of up to ~85 USD per participant). Reward type (real vs. hypothetical) affected decision quality, including value maximization, switching between options, and dominance violations (choices of an option that was inferior to another option in all respects). Decision quality was markedly better with real than hypothetical rewards in older adults and correlated with numeracy in both age groups. However, we found no evidence that reward type affected people's risk preferences. Overall, the findings portray a fairly positive picture regarding the use of hypothetical scenarios to assess preferences: With carefully prepared instructions, people from different age groups indicate preferences in hypothetical scenarios that match their decisions with real and much higher rewards. One advantage of using real rewards is that they help to reduce decision noise

CFK-Flüssigwasserstofftanks von Größe S bis XXL für ein CO2-freies Fliegen

Zukünftige CO2-freie Wasserstoffantriebe erfordern effiziente Technologien und Systeme zur Treibstoffspeicherung. Für Verkehrsflugzeuge ist die Wasserstoffspeicherung in kryogener Form die interessanteste Variante. Wasserstoff ist zwar deutlich leichter als Kerosin, beansprucht jedoch mehr Volumen und einen dedizierten Platz für die benötigten Druckbehälter. Sind große Tanks als Gondel unter den Flügeln oder im Rumpfheck die Lösung für zukünftige Flugzeuge

Optimization of filament wound cryogenic composite tanks with unconventional geometries for future aircraft configurations

Eine vielversprechende Technologie zur Minimierung von CO2 Emissionen in der Luftfahrt ist der Einsatz flüssigen und unter kryogenen Bedingungen gespeicherten Wasserstoffs. Dieser weist allerdings zeitgleich aufgrund der geringen volumetrischen Energiedichte Herausforderungen in Bezug auf die Integration des Tanks im Flugzeug auf. Ein Konzept verfolgt die Integration in der hinteren konischen Rumpfsektion, was eine hohe Flexibilität der Tankgeometrie in Verbindung mit einer geringen Masse voraussetzt. Daraus leitet sich die Zielsetzung der Arbeit ab, eine bestehende Software zur Simulation des Wickelprozesses für zylindrische Tanks um konische Geometrien sowie verschiedene Domtypen zu erweitern und diese, auch im Kontext des Flugzeugdesigns, zu analysieren und zu bewerten. Basierend auf einer relativen geometrischen Parametrisierung, die die radialen und longitudinalen Dimensionen des Tanks ins Verhältnis setzt, wurde die Simulationssoftware erweitert, sowie neben halbkugelförmigen und elliptischen Domkonturen mit variablen Halbachsenverhältnissen auch torispherische und isotensoide Domformen implementiert. In einer Voranalyse wurden die beschriebenen Domtypen für zylindrische und konische Tankformen gegenübergestellt und die resultierenden Massen sowie geometrischen Dimensionen bewertet. Unabhängig von der Form des Tanks bieten isotensoide Döme den besten Kompromiss der in Betracht gezogenen Kriterien. Basierend auf diesen Erkenntnissen und den zuvor implementierten geometrischen Erweiterungen der Software wurden auf Basis eines bestehenden Flugzeugkonzepts die Auswirkungen verschiedener Tankformen untersucht. Dazu wurde die Position der Tanks im vordefinierten Designraum so variiert, dass zylindrische als auch rein konische Tankformen erstellt, ausgewertet sowie der Einfluss auf die Flugzeugmasse bewertet wurden. Daraus konnte geschlussfolgert werden, dass konische Tankformen, trotz der höheren Eigenmasse, aufgrund der geringeren Rumpflänge, Vorteile gegenüber zylindrischen Formen haben. Diese Erkenntnisse konnten im Ersatzmodell bestätigt werden, in dem der Einfluss der verschiedenen geometrischen Designparameter auf die Tankmasse sowie -oberfläche analysiert wurden

Automated liquid hydrogen tank design optimization using filament winding simulation and subsequent comparison with aluminium vessels

The design of hydrogen fuel storages in future aircraft configurations is one key enabler for drastic reduction in climate impact of aviation. Due to the volumetric efficiency, liquid hydrogen pressure vessels are the most promising storage solution for short and medium range hydrogen-based aircraft. The aircraft configurations may contain tanks in wing pods as well as in the rear fuselage section which results in a big parameter range of the tank geometries. This study presents an automated design optimization process employing a detailed CFRP winding simulation, which is used to create tank models for aircraft pre design. Additionally, a comparison with aluminium based vessels is shown and mass advantages are presented. The winding process is based on MeFeX's µChain. It features a winding simulation on geodesic paths on liners with arbitrary axially symmetric contours. In addition, a fast analytical structural solver and a FEM model can be used. This allows detailed designs but also features fast, automated models for design optimization of a big variety of tanks. During the design process, each new layer is optimized. The optimization process chooses between hoop and helical layers and minimizes the maximal failure criterion. When all failure criteria are met, the design optimization is finished and no more layer needs to be added. In order to supply an even faster method for tank mass assessment in aircraft pre design, a surrogate model based on machine learning is created. This is achieved by the definition of the parameter space, the setup of a design of experiments and the creation of a kriging model. As third model, an aluminium tank design method is employed in order to evaluate possible mass savings of the CFRP design. This method features the wall thickness estimation, also accounting for fatigue. The fatigue model is based on load cycle sets of two different kinds, S-N curves and a damage accumulation method. The CFRP winding model and the surrogate model are compared and discussed with respect to accuracy and the discrete nature of CFRP layers. The differences in mass for the CFRP and aluminium tank designs are assessed and additional influence factors are discussed

Damage tolerance criteria for composite laminates under tension and compression load

Any composite aircraft structure exposed to impact has to be designed accounting for damage tolerance (DT). Impact damage has to be endured throughout the structure's service life. The damage tolerant design has to guarantee a load-sustaining capability above the limit load at any time. An exceptional challenge to the damage tolerant design of composites is the multiplicity of failure modes in a composite laminate. Considerable effort is necessary to characterize the damage behavior and the respective residual properties through physical experiments or numerical high-fidelity methods. The common proceeding during the preliminary design phase is a fixed strain allowable that may not be exceeded. To relax the existing single allowable and to open the design space allowing composite structures with arbitrary laminates, specific allowables for each laminate have to be determined. The methods presented in this work shall enable this specific calculation for the preliminary phase of the aircraft design. In this phase, efficient DT criteria building on elementary material parameters are required. To derive suitable calculation methods, the driving failure mechanisms of the damage evolution are identified for cyclic tension and compression loading, separately. Under tensile loading, the mechanism driving the damage propagation results from an interaction of delamination and fiber fracture. The corresponding mode II energy release rate (ERR) GIIx at the delamination crack tip can be calculated through an elementary energy balance approach and the principle of maximum energy release. Under compression load, fiber kinking and delamination growth characterize the damage evolution of an impact damage. A sublaminate buckling criterion combined with a virtual crack extension method permits one to calculate the ERRs GIx and GIy in each propagation direction. The results are validated through the data of cyclic tension after impact and compression after impact tests

Influence of electrospray deposition on C_60 molecular assemblies

Maintaining clean conditions for samples during all steps of preparation and investigation is important for scanning probe studies at the atomic or molecular level. For large or fragile organic molecules, where sublimation cannot be used, high-vacuum electrospray deposition is a good alternative. However, because this method requires the introduction into vacuum of the molecules from solution, clean conditions are more difficult to be maintained. Additionally, because the presence of solvent on the surface cannot be fully eliminated, one has to take care of its possible influence. Here, we compare the high-vacuum electrospray deposition method to thermal evaporation for the preparation of C; 60; on different surfaces and compare, for sub-monolayer coverages, the influence of the deposition method on the formation of molecular assemblies. Whereas the island location is the main difference for metal surfaces, we observe for alkali halide and metal oxide substrates that the high-vacuum electrospray method can yield single isolated molecules accompanied by surface modifications

Operational Loads Monitoring and CFRP Damage Accumulation for Predictive Maintenance

A flexible aircraft maintenance scheme based on predictive maintenance allows a higher structural uti-lization. This leads to reduced mass for new aircraft designs or longer maintenance intervals for existingaircraft. Current aircraft are designed to endure predefined operating load and to fulfil standard main-tenance requirements with fixed intervals for damage inspection. For a predictive maintenance, theutilization the actual load history of an aircraft as well as evaluating the development of a damage will beanalysed. The workflow in figure 1 uses the concept of a digital twin by evaluating data from on-boardsensors. The Operational Loads Monitoring System (OLMS) transforms this data into operating globalloads. These are converted to local strain spectra and fed into a damage tolerance calculation estimatingthe remaining useful life (RUL) of a structu

HYTAZER: Towards the qualification and certification of (liquid) hydrogen tanks in aviation and shipping

The project Hytazer is the first to bundle the developments of hydrogen tanks within the DLR. On the one hand, its goal is to enable a broad usage of hydrogen in various transportation systems such as aviation, space, rail, automotive and ship building. On the other hand, with liquid, compressed, cryo-compressed hydrogen and metal hydride, a broad range of hydrogen storages and energy carriers are under consideration. In the project, for selected hydrogen storage systems in the specific context of the application in a transportation system, the current state of the certification specification is reviewed and the need for tailoring, extension or the deduction of new specifications will be identified. This talk presents an overview of the project. It focusses on selected challenges in the design, manufacturing and qualification of hydrogen storages. The talk covers the definition of requirements by simulating the transportation system itself and based on existing certification criteria. Secondly simulation-based approaches for challenges such as design, sloshing and crash worthiness are presented, that will be used to show compliance against certification requirements. Next, manufacturing processes under consideration for CFRP storages with a reproducible quality and material fulfilling permeation boundary conditions are shown. Lastly a test pyramid for the qualification of liquid hydrogen storages is presented. From this, existing test setups, possible extensions and future test stands are discussed. They are used to define appropriate means of compliance for certification but also validate simulation based approaches to reduce test effort

Preserved bioactivity and tunable release of a SDF1-GPVI bi-specific protein using photo-crosslinked PEGda hydrogels

AbstractChemokine-induced stem cell recruitment is a promising strategy for post myocardial infarction treatment. Injection of stromal cell-derived factor 1 (SDF1) has been shown to attract bone marrow-derived progenitor cells (BMPCs) from the blood that have the potential to differentiate into cardiovascular cells, which support angiogenesis, enabling the improvement of myocardial function. SDF1-GPVI bi-specific protein contains a glycoprotein VI (GPVI)-domain that serves as an anchor for collagen type I (Col I) and III, which are exposed in the wall of injured vasculature. In this study, we generated a cytocompatible hydrogel via photo-crosslinking of poly(ethylene glycol) diacrylate that serves as a reservoir for SDF1-GPVI. Controlled and sustained release of SDF1-GPVI was demonstrated over a period of 7 days. Release features were modifiable depending on the degree of the crosslinking density. Functionality of the GPVI-domain was investigated using a GPVI-binding ELISA to Col I. Activity of the SDF1-domain was tested for its CXCR4 binding potential. Preserved functionality of SDF1-GPVI bi-specific protein after photo-crosslinking and controllable release was successfully demonstrated in vitro supporting the implementation of this drug delivery system as a powerful tool for therapeutic protein delivery in the treatment of cardiovascular ischemic disease