Exploring the design space for a hybrid-electric regional aircraft with multidisciplinary design optimisation methods

Envisioned in the next 15 to 30 years in the aviation industry, hybrid-electric propulsion offers theopportunity to integrate new technology bricks providing additional degrees of freedom to improveoverall aircraft performance, limit the use of non-renewable fossil resources and reduce the aircraftenvironmental footprint. Today, hybrid-electric technology has mainly been applied to groundbased transports, cars, buses and trains, but also ships. The feasibility in the air industry has to beestablished and the improvement in aircraft performance has still to be demonstrated. This thesisaims to evaluate the energy savings enabled by electric power in the case of a 70-seat regionalaircraft. First, energy saving opportunities are identified from the analysis of the propulsion andaerodynamic efficiencies of a conventional twin turboprop aircraft. The potential benefits comingfrom the variation of the size of prime movers and the new power managements with the use ofbatteries are studied. Also, possible aerodynamic improvements enabled by new propellerintegrations are considered. For each topic, simplified analyses provide estimated potential ofenergy saving. These results are then used to select four electrified propulsion systems that arestudied in more detail in the thesis: a parallel-hybrid, a turboelectric with distributed propulsion, apartial-turboelectric with high-lift propellers and an all-electric. Evaluating the selected hybrid-electric aircraft is even more challenging that the sizing of the different components, the energymanagement strategies and the mission profiles one can imagine are many and varied. Inaddition, the overall aircraft design process and the evaluation tools need to be adaptedaccordingly. The Airbus in-house Multidisciplinary Design Optimisation platform named XMDO,which includes most of the required modifications, is eventually selected and further developedduring the thesis. For examples, new parametric component models (blown wing, electrical motor,gas turbine, propeller, etc…) are created, a generic formulation for solving the propulsion systemequilibrium is implemented, and simulation models for take-off and landing are improved. In orderto evaluate the energy efficiency of the hybrid-electric aircraft, a reference aircraft equipped with aconventional propulsion system is first optimised with XMDO. Different optimisation algorithms aretested, and the consistency of the new design method is checked. Then, all the hybrid-electricconfigurations are optimised under the same aircraft design requirements as the reference. Forthe electrical components, two levels of technology are defined regarding the service entry date ofthe aircraft. The optimisation results for the turboelectric and the partial-turboelectric are used tobetter understand the potential aerodynamic improvements identified in the first part of the thesis.Optimisations for the parallel-hybrid, including different battery recharge scenarios, highlight thebest energy management strategies when batteries are used as secondary energy sources. All theresults are finally compared to the reference in terms of fuel and energy efficiencies, for the twoelectrical technology levels. The last part of the thesis focuses on the all-electric aircraft, and aimsat identifying the minimum specific energy required for batteries as a function of the aircraft designrange. A trade study is also carried-out in accordance with the service entry date for the otherelectrical component

Etude de la répartition spatiale des précipitations en milieu sahélien à l'aide du réseau dense de pluviographes de l'expérience EPSAT-Niger : application à la détermination de la précision des moyennes surfaciques au pas de temps de l'événement pluvieux

La connaissance de la répartition spatiale et temporelle des précipitations dans les régions sahéliennes est une demande exprimée par les états concernés. Dans cette optique, la répartition spatiale des précipitations à l'échelle de la saison des pluies, puis de l'événément pluvieux a été étudiée. Les données utilisées proviennent d'un réseau dense de pluviographes implanté au Niger. La méthode d'interpolation choisie est le krigeage. A l'échelle de la saison des pluies, l'analyse a montré une grande variabilité spatiale et temporelle. L'incidence sur le calcul des isohyètes et des pluies surfaciques en a été déduite. L'influence de la densité de postes a également été soulignée. Au pas de temps de l'événement pluvieux, une classe d'événements a été définie et étudiée. Leur structure spatiale s'est révélée stable dans le temps. On a pu en déduire des abaques, donnant l'erreur d'estimation de la pluie surfacique en fonction de la densité du réseau et de la taille de la surface. Ces abaques permettront aux modélisateurs de connaître la précision de leurs variables d'entrée. (Résumé d'auteur

Maximum Loads on a One Degree of Freedom Model-scale Offshore Wind Turbine

AbstractThis paper presents the results of an experiment carried out in a wave flume aiming at reproducing a 50-year wave condition on an extra-large bottom-fixed offshore wind turbine mounted on a monopile. The model is a stiff cylinder mounted on a spring allowing rotation of the system around its base only in the wave propagation direction. Under these conditions, the turbine is assumed to be idling, and the damping ratio of the system is 2.4%. The overturning moment at the base of the cylinder is measured, and it is found that the maximum responses are recorded when long steep breaking or near-breaking waves hit the cylinder and excite the first eigenperiod of the structure. For a selected event involving a breaking wave, the response of the system is compared to numerical simulations using the FNV method. The higher order excitation loads from the FNV are approximated as sinusoid pulse loads, and it is shown that since the duration of these pulses lies close to the eigenperiod of the structure, they suffice to trigger the first mode motion, without the need for a slamming model. A consequence of the low damping is that if the structure has been previously excited at its 1st mode (linearly or by higher order phenomena such as springing), the structure can already have a motion that adds up to the transient response to the pulse loads. The findings of this study also challenge some of the load models currently used by the industry to estimate the response of offshore wind turbines during extreme events

Oral-Facial-Digital syndrome Type I cells exhibit impaired DNA repair; unanticipated consequences of defective OFD1 outside of the cilia network

Defects in OFD1 underlie the clinically complex ciliopathy, Oral-Facial-Digital syndrome Type I (OFD Type I). Our understanding of the molecular, cellular and clinical consequences of impaired OFD1 originate from its characterised roles at the centrosome/basal body/cilia network. Nonetheless, the first described OFD1 interactors were components of the TIP60 histone acetyltransferase complex. We find that OFD1 can also localise to chromatin and its reduced expression is associated with mislocalization of TIP60 in patient-derived cell lines. TIP60 plays important roles in controlling DNA repair. OFD Type I cells exhibit reduced histone acetylation and altered chromatin dynamics in response to DNA double strand breaks (DSBs). Furthermore, reduced OFD1 impaired DSB repair via homologous recombination repair (HRR). OFD1 loss also adversely impacted upon the DSB-induced G2-M checkpoint, inducing a hypersensitive and prolonged arrest. Our findings show that OFD Type I patient cells have pronounced defects in the DSB-induced histone modification, chromatin remodelling and DSB-repair via HRR; effectively phenocopying loss of TIP60. These data extend our knowledge of the molecular and cellular consequences of impaired OFD1, demonstrating that loss of OFD1 can negatively impact upon important nuclear events; chromatin plasticity and DNA repair

Liming impacts barley yield over a wide concentration range of soil exchangeable cations

Liming has widespread and significant impacts on soil processes and crop responses. The aim of this study was to describe the relationships between exchangeable cation concentrations in soil and the relative yield of spring barley. The hypothesis was that yield is restricted by the concentration of a single exchangeable cation in the soil. For simplicity, we focused on spring barley which was grown in nine years of a long-term experiment at two sites (Rothamsted and Woburn). Four liming rates were applied and in each year the relative yield (RY) and the concentrations of exchangeable cations were assessed. Liming had highly significant effects on the concentrations of most exchangeable cations, except for Cu and K. There were significant negative relationships (either linear or exponential) between the exchangeable concentrations of Mn, Cd, Cr, Al, Fe, Cu, Co, Zn and Ni in soil and soil pH. The relationships between RY and the concentrations of selected exchangeable cations (Mn, Ca and Al) were described well using log-logistic relationships. For these cations a significant site effect was probably due to fundamental differences in soil properties. At both sites the concentrations of exchangeable soil Al were excessive ([ 7.5 mg kg-1) and were most likely responsible for reduced barley yields (where RY B 0.5) with soil acidification. At Rothamsted barley yield was nonlimited (where RY C 1) at soil exchangeable Mn concentrations (up to 417 mg kg-1) greater than previously considered toxic, which requires further evaluation of critical Mn concentrations

Evaluation de la durabilité du béton armé vis à vis des ions chlorure à l'aide de capteurs noyés dans le béton versus des auscultations en parement

GC'2019, le Génie Civil au coeur des mutations technologiques et numériques , CACHAN, FRANCE, 20-/03/2019 - 21/03/2019L'évaluation du processus de corrosion de structures en béton armé en milieu chloruré a été étudiée en utilisant deux approches complémentaires : l'auscultation non destructive (ND) du béton d'enrobage et la corrosion des armatures. Différentes méthodes d'évaluation non destructives basées, soit sur de l'instrumentation avec des capteurs noyés dans le béton armé, soit sur des auscultations réalisées en parement, ont été utilisées afin de caractériser la phase d'incubation puis la phase de propagation de la corrosion. Dans cette première phase d'étude, les différents objectifs étaient les suivants : 1) Etudier des bétons différents formulés avec du ciment Portland ou des laitiers, en termes de réaction de transfert dans le béton et de réactions électrochimiques armature/béton/environnement, 2) Analyser les résultats des capteurs noyés dans le béton armé (formulé avec du ciment Portland ou des laitiers) qui permettent de suivre en continu l'évolution des phénomènes, 3) Comparer les résultats entre les capteurs noyés et les mesures réalisées sur parement, 4) Démontrer l'intérêt du Corrosion Health Monitoring sur ouvrages neufs et/ou réparés en termes de surveillance (système d'alerte plutôt qu'alarme) dans le temps. Les différentes méthodes basées sur des mesures de résistivité (capteurs noyés et auscultation en surface) permettent d'accéder à des profils traduisant la pénétration d'eau de mer par imbibition. Des méthodologies d'inversion et de calibration ont été consolidées. Une expérience sur les capteurs de corrosion a été capitalisée. Enfin, de nouvelles méthodes ont été explorées (SUSI, radar de fréquence,...) et certaines sont prometteuses. Les interprétations des résultats peuvent s'avérer délicates et il convient de bien énoncer les hypothèses et les limites notamment dans une prise de décision (maintenance et/ou réparation par ex). Enfin, il est nécessaire de poursuivre cette étude sur du plus long terme afin d'affiner les résultats et les applications fortes pour la gestion du parc d'ouvrages vieillissants

Les stations mésolithiques du Raumarais, commune de Digulleville (Manche)

À la suite d’un projet de construction d’une nouvelle usine dans le centre atomique de La Hague, une opération de sauvetage archéologique fut entreprise en 1980. Deux gisements mésolithiques ont été reconnus (locus 1 et 3). La fouille du locus 3 a permis la découverte d’un foyer en cuvette. L’analyse du matériel lithique recueilli dans son comblement et ses abords nous incite à placer cette série au début du stade moyen du Mésolithique. L’outillage commun est caractérisé par un taux élevé de petits grattoirs. Les lamelles étroites à bord abattu, dont quelques exemplaires sont tronqués, prédominent les armatures à plus de 80 %. Ce taux n’a pas été confirmé pour l’instant sur d’autres sites du nord-Cotentin.The Mesolithic sites of Le Raumarais, commune of Digulleville (Manche) As a result of the construction of a new building at the Hague Nuclear Centre, archaeological investigation was conducted in 1980. Two mesolithic sites (locus 1 and 3) were identified. Excavation on locus 3 revealed a hearth. Analysis of the lithic artefacts found in this and in the vicinity suggest that the Digulleville assemblage should be dated to the beginning of the middle Mesolithic period. Common tools include a high proportion of small scrapers and narrow backed bladelets with some truncated examples, where points represent more than 80 % of the total. This ratio has not been yet observed at other sites of North Cotentin

Surface patterning of carbon nanotubes can enhance their penetration through a phospholipid bilayer

Nanotube patterning may occur naturally upon the spontaneous self-assembly of biomolecules onto the surface of single-walled carbon nanotubes (SWNTs). It results in periodically alternating bands of surface properties, ranging from relatively hydrophilic to hydrophobic, along the axis of the nanotube. Single Chain Mean Field (SCMF) theory has been used to estimate the free energy of systems in which a surface patterned nanotube penetrates a phospholipid bilayer. In contrast to un-patterned nanotubes with uniform surface properties, certain patterned nanotubes have been identified that display a relatively low and approximately constant system free energy (10 kT) as the nanotube traverses through the bilayer. These observations support the hypothesis that the spontaneous self-assembly of bio-molecules on the surface of SWNTs may facilitate nanotube transduction through cell membranes.Comment: Published in ACS Nano http://pubs.acs.org/doi/abs/10.1021/nn102763

Hybrid Regional Aircraft: A Comparative Review of New Potentials Enabled by Electric Power

This article assesses the benefits of hybridization within the regional aircraft scale using a conventional twin-turbo propeller aircraft as reference. For a fair comparison, this reference aircraft was designed assuming a 2035 technology level. The propulsion system of the reference aircraft is analyzed along the mission and the phases of flight with low efficiencies are highlighted. Then the potential benefits of new power management through the use of secondary power generation systems but also through the variation of the size of prime movers are presented and discussed. In particular, the effect of the gas turbine size on its efficiency is studied. Finally, the article focuses on aerodynamic improvements enabled by new propeller or fan integrations and the associated concepts such as differential thrust, blown wing and boundary layer ingestion. For each topic, simplified analyses provide estimated potential of energy saving. These results can be used as indicators for selecting the most promising hybrid architecture concepts for a regional aircraft