A mixed midelity conceptual design process for Boundary Layer Ingestion concepts

Boundary Layer Ingestion (BLI) is a promising concept that helps improving aircraft aeropropulsive performance. However, it remains difficult to bring together OAD (Overall Aircraft Design) process and high-fidelity tools due to the time of response of complex disciplinary tools. ONERA has thus developed a mixed fidelity approach inside its in-house OAD platform. The purpose is to mix conventional and robust OAD methods with high levels of fidelity from disciplinary tools such as CFD (Computational Fluid Dynamics), FEM (Finite Element Model) or CAA (Computational Aero Acoustics). This paper focuses on the integration of rapid CFD tools inside the OAD process, in order to assess BLI benefits. The resulting process is validated against reference and experimental cases when available, or high-fidelity RANS data elsewhere. The paper intends to present the tools and their validation process. These modules are applied to the common inlet concept, which aims at ingesting00% of the fuselage boundary layer. The results demonstrate the potential gain on the Power Saving Coefficient (up to 3% obtained with the L2 BLI module without resizing loop) but with non-negligible fan losses (up to 1.5%)

Exploration and Sizing of a Large Passenger Aircraft with Distributed Electric Ducted Fans

In order to reduce the CO2 emissions, a disruptive concept in aircraft propulsion has to be considered. As studied in the past years hybrid distributed electric propulsion is a promising option. In this work the feasibility of a new concept aircraft, using this technology, has been studied. Two different energy sources have been used: fuel based engines and batteries. The latters have been chosen because of their exibility during operations and their promising improvements over next years. The technological horizon considered in this study is the 2035: thus some critical hypotheses have been made for electrical components, airframe and propulsion. Due to the uncertainty associated to these data, sensivity analyses have been performed in order to assess the impact of technologies variations. To evaluate the advantages of the proposed concept, a comparison with a conventional aircraft(EIS 2035), based on evolutions of today's technology (airframe, propulsion, aerodynamics)has been made

Sensitivity of Boundary Layer Ingestion Effects to Tube and Wing Airframe Design Features

Conceptual design of boundary layer ingesting (BLI) aircraft requires a methodology that captures the aero-propulsive interactions in a parametric fashion. This entails modeling the impacts of BLI as a function of the airframe and propulsor design. Previous work has analyzed the sensitivity of these BLI effects to the propulsor size and throttle. This paper assesses the sensitivity of the BLI effects to the airframe design through a series of experiments, using CFD. The scope of this analysis is restricted to tube and wing type BLI concepts. Results from these studies help identify the critical airframe design space that needs to be considered when generating a parametric model of the BLI effects. Guidelines regarding the level of detail required for the airframe geometry model are discussed

Future Aircraft and the Future of Aircraft Noise

In order to cope with increasing air traffic and the requirement to decrease the overall footprint of the aviation sector - making it more sustainably and acceptable for the whole society - drastic technology improvements are required beside all other measures. This includes also the development of novel aircraft configurations and associated technologies which are anticipated to bring significant improvements for fuel burn, gaseous and noise emissions compared to the current state and the current evolutionary development. Several research projects all over the world have been investigating specific technologies to address these goals individually, or novel - sometimes also called "disruptive" - aircraft concepts as a whole. The chapter provides a small glimpse on these activities - mainly from a point of view of recent European funded research activities like Horizon2020 projects ARTEM, PARSIFAL, and SENECA being by no-way complete or exhaustive. The focus of this collection is on noise implications of exemplary novel concepts as this is one of the most complicated and least addressed topics in the assessment of aircraft configurations in an early design stage. Beside the boundary layer ingestion concept, the design process for a blended wing body aircraft is described, a box-wing concept is presented and an outlook on emerging supersonic air transport is given

Exergy-Based Formulation for Aircraft Aeropropulsive Performance Assessment: Theoretical Development

International audienceAircraft have evolved into extremely complex systems that require adapted methodologies and tools for an efficient design process. A theoretical formulation based on exergy management is proposed for assessing the aeropropulsive performance of future aircraft configurations. It consists in the combina-tion of a momentum balance and a fluid flow analysis involving on the first and second laws of thermo-dynamics. The exergy supplied by the propulsion system and its partial destruction within the control volume is associated with the aircraft mechanical equilibrium. Characterization of the recoverable mechanical and thermal outflows is made along with the identification of the irreversible phenomena that destroy their work potential. Restriction of the formulation to unpowered configurations yields connections to some well-known far-field drag expressions and shows that their underlying theory can be related to exergy considerations. As the exergy balance does not rely on the distinction of thrust and drag, it is especially suitable for the performance evaluation of highly integrated aeropropulsive concepts like boundary layer ingestion

Adjoint and direct characteristic equations for two-dimensional compressible Euler flows

The method of characteristics is a classical method for gaining understanding in the solution of a partial differential equation. It has recently been applied to the adjoint equations of the 2D Euler equations and the first goal of this paper is to present a linear algebra analysis that greatly simplifies the discussion of the number of independant characteristic equations satisfied along a family of characteristic curves. This method may be applied for both the direct and the adjoint problem and our second goal is to directly derive in conservative variables the characteristic equations of 2D compressible inviscid flows. Finally, the theoretical results are assessed for a nozzle flow with a classical scheme and its dual consistent discrete adjoint

Etude de l'oxydation radiolytique de l'uranium de degré d'oxydation +IV par radiolyses pulsée et stationnaire induites par divers rayonnements (hélions, électrons accélérés et gamma )

Dans chaque étape du cycle du combustible nucléaire, la compréhension des effets des rayonnements alpha, gamma et bêta sur les matériaux, dont l un des éléments essentiels est l uranium (U), joue un rôle physico-chimique important. Ce travail consiste donc à comprendre l effet de ces rayonnements ionisants sur UIV et en particulier, sur son oxydation radiolytique. L élément est inséré dans une solution aqueuse acidifiée (HCl) pour stabiliser cet état d oxydation très instable en présence de O2 et en fixant la force ionique (NaCl) pour une comparaison plus aisée des résultats. Premièrement, l oxydation radiolytique de UIV a été observée en radiolyse stationnaire à la fois a et g nous informant sur le bilan global de cette réaction par la mesure des rendements radiolytiques de disparition de UIV et d apparition de UVI sous différentes atmosphères. Deuxièmement, un système pompe sonde picoseconde couplé à l accélérateur d électrons ELYSE a été développé pour comprendre le mécanisme d oxydation initiée par des particules à bas T.E.L dont la rapidité est imposée par la forte concentration en capteurs. Le rendement de formation du radical hydroxyle HO issu de la radiolyse de l eau a donc été estimé. De cette étude, le mécanisme d oxydation de UIV a été déduit, confirmé ensuite par des simulations. Troisièmement, un dispositif de spectroscopie transitoire couplé à un faisceau pulsé d hélions a été élaboré dans le but de sa future adaptation et utilisation sur le cyclotron ARRONAX . Le but de ce travail est de préparer en amont l arrivée de ce cyclotron afin de favoriser son installation et donc commencer ces études en radiolyse impulsionnelle alpha.In each step of the nuclear fuel cycle, the understanding of effects of ionizing radiations (alpha, beta, gamma) on some matters of which one of elements is uranium (U), has an important physical chemistry role. This work aims to understand the effect of these ionizing radiations on UIV and in particular, on its radiolytic oxidation. This one is inserted in an acidified aqueous solution (HCl) so as to stabilize this very unstable oxidation degree in the presence of O2 and by fixing the ionic strength (NaCl) for an easier comparison of the results. Firstly, the radiolytic oxidation of UIV had been observed during a and g stationary radiolysis which informs on the overall balance of this reaction by measuring the radiolytic yields of disappearance for UIV and appearance for UVI under different atmospheres. Secondly, a picosecond pulse probe setup connected with the electron accelerator ELYSE had been developed in order to understand the mechanism of the oxidation initiated by low L.E.T particles of which the fastness is due to the high concentration of scavengers. The formation radiolytic yield of the hydroxyl radical HO had been estimated. From this study, the oxidation mechanism of UIV had been deduced, confirmed then by some simulations.Thirdly, a transient spectroscopy setup linked with a hellion pulse beam had been established for the future adaptation and use on the cyclotron ARRONAX . The aim of this work is to prepare the arrival of this cyclotron in order to facilitate its installation and then, begin quickly the study of alpha pulse radiolysisNANTES-BU Sciences (441092104) / SudocSudocFranceF

Processus de conception de fidélité mixte pour des concepts d'avion à ingestion de couche limite

International audienceBoundary Layer Ingestion (BLI) is a promising concept that helps improving aircraft aeropropulsive performance. However, it remains difficult to bring together OAD (Overall Aircraft Design) process and high-fidelity tools due to the time of response of complex disciplinary tools. ONERA has thus developed a mixed fidelity approach inside its in-house OAD platform. The purpose is to mix conventional and robust OAD methods with high levels of fidelity from disciplinary tools such as CFD (Computational Fluid Dynamics), FEM (Finite Element Model) or CAA (Computational Aero Acoustics). This paper focuses on the integration of rapid CFD tools inside the OAD process, in order to assess BLI benefits. The resulting process is validated against reference and experimental cases when available, or high-fidelity RANS data elsewhere. The paper intends to present the tools and their validation process. These modules are applied to the common inlet concept, which aims at ingesting 100% of the fuselage boundary layer. The results demonstrate the potential gain on the Power Saving Coefficient (up to 3% obtained with the L2 BLI module without resizing loop) but with non-negligible fan losses (up to 1.5%).L'ingestion de la couche limite (BLI) est l'un des concepts prometteurs permettant d'améliorer les performances aéropropulsives des avions. Plusieurs études ont déjà mis en évidence les avantages de cette technologie, soit au niveau de l'OAD (Overall Aircraft Design), soit avec la CFD (Computational Fluid Dynamics) haute-fidélité. Cependant, il reste difficile de rapprocher les outils OAD et haute-fidélité en raison du temps de réponse des outils disciplinaires complexes. L'ONERA a donc développé une approche de fidélité mixte au sein de sa plateforme interne OAD, en y intégrant des outils disciplinaires rapides. Le but est de mélanger des méthodes OAD conventionnelles et robustes avec des niveaux de fidélité élevés provenant d'outils disciplinaires tels que CFD, FEM ou CAA. Cet article se concentre sur l'intégration d'outils rapides de CFD dans le processus d'OAD, afin d'évaluer les avantages de la BLI.Le processus qui en résulte est validé par rapport à des cas de référence et expérimentaux lorsqu'ils sont disponibles, ou par rapport à des données RANS haute-fidélité. L'article a pour but de présenter les outils, leur processus de validation et les résultats globaux au niveau de l'OAD pour différentes familles d'avions (tels que les avions à moyen courriers ou les jets d'affaires) en utilisant les différents niveaux de fidélité disponibles

Adjoint and Direct Characteristic Equations for Two-Dimensional Compressible Euler Flows

The method of characteristics is a classical method for gaining understanding in the solution of a partial differential equation. It has recently been applied to the adjoint equations of the 2D steady-state Euler equations and the first goal of this paper is to present a linear algebra analysis that greatly simplifies the discussion of the number of independent characteristic equations satisfied along a family of characteristic curves. This method may be applied for both the direct and the adjoint problem. Our second goal is to directly derive in conservative variables the characteristic equations of 2D compressible inviscid flows. Finally, the theoretical results are assessed for a nozzle flow with a classical scheme and its dual consistent discrete adjoint

Overview of Aerodynamic Design Activities Performed at ONERA to Reduce Aviation's Climate Impact 1

International audienceThis paper aims at summarizing the recent aerodynamic design activities performed at ONERA on promising innovative aircraft and engine integration concepts with the objective to strongly reduce Aviation's climate impact. Within different projects of the Clean Sky 2 European Programme, ONERA explores two specific aircraft configurations combined with two innovative engine integration technologies for a typical Small Medium Range (SMR) mission. Three concepts are proposed in this paper with three different targets in terms of entrance into service (2035, 2045, 2050+). First, a summary of first aerodynamic optimizations based on Overall Aircraft inputs for a High Aspect Ratio Strut-Braced Wing (HAR SBW) concept performed in the frame of the U-HARWARD project is proposed. The results show important potential benefits compared to a classical cantilever wing. Then, aerodynamic design and optimization studies on a Blended Wing Body concept are described with a two step approach: the design of the glider configuration first and then a derivative configuration with Boundary Layer ingestion. The synergy between the aircraft concept and this innovative engine integration technology underlines important potential benefits in terms of aerodynamic performance. Finally, the aerodynamic design of an hybrid electric concept equipped with distributed propulsion is described. The integration of such engine concept is very challenging in transonic conditions, a first configuration is proposed with a proper aerodynamic behavior