Characterization of ethane jet from sub-critical to super-critical conditions through visible light and X-ray imaging

International audienceThe injection of fuel in a high-pressure gaseous environment, for automotive, aeronautical or rocket applications leads to thermodynamic conditions where pressure exceeds the critical pressure of working fluids and thus, the supercritical state of matter is reached. Providing reliable experimental results under these particular conditions is still nowadays a challenge, but it is of great importance for the validation of numerical codes. Indeed, at such a high pressure, the distinction between gaseous and liquid phases becomes blurred as surface tension decreases and the interface disappears completely. For such special conditions, experimental data are scarce and need to be consolidated. As an example, the modification of the local refractive index induced by density gradient makes the visible-light imaging technique to be used with care. The REFINE testbench (Real-gas Effect on Fluid Injection: a Numerical and Experimental study) has been designed at CORIA Lab to study the non-reactive injection of Ethane and Propane under sub-and supercritical conditions. The ambient gas pressure can be raised up to 6 MPa and warmed up to 573 K to scan sub-and trans-critical injection conditions. The chamber is equipped with two perpendicular accesses allowing different simultaneous diagnostics to be applied to the jet. Experimental data are collected from shadowgraph, diffused backlight illumination techniques and X-Ray. Quantitative measurements of jet spreading angle, breakup length and density maps are compared to literature results. Introduction The study of high pressure injection is a major topic of research in the transport industry (cars, aircrafts, rockets) because it conditions the combustion performance and therefore the formation of pollutants. Under certain conditions of pressure and temperature the liquid injected into the chamber does not behave as usual and the atom-ization process is replaced by a diffusion one [1, 2]. The experimental study of this transition is a challenge because it requires the development of a robust, precise and well-controlled experiment as well as adapted diagnostics. The number of experiments dealing with supercritical injection is therefore small and the amount of experimental data that can be used for modeling validation [3, 4, 5] is all the more scarce [6]. In particular, the high ambient pressure locally affects the refractive index gradient making the use of laser-based diagnostics questionable [7, 6] to provide quantitative local experimental data. Nevertheless, classical diagnostics such as shadowgraphy or schlieren techniques have been used up to now to observe the transition from a system composed of distinct liquid and gaseous phases [6, 8, 9] to a system where dense and light fluids mix together because the surface tension and the heat of vaporization diminish [10, 11]. Under supercritical conditions, a dense and dark core is visible at the injector exit on shadowgraph [12] and the analysis of the spreading angle shows that supercritical jet has a behavior closer to a gaseous jet than to a liquid jet [13, 14]. In this study, the first results coming from the research program REFINE (Real-gas Effect on Fluid Injection: a Numerical and Experimental study) are provided. It consists in an injection of Ethane into an environment of Nitrogen or Helium at high pressure and moderate temperature. The objective is to deliver a set of quantitative data for the dark core length and the spreading angle of a non-assisted jet, from subcritical to supercritical pressure with respect to the liquid injected, and for various levels of ambiant temperature. A tentative to deliver the value of density on the jet axis through the radiography of the liquid jet is also presented. Radiography is an X-ray imaging technique that has been used for the study of diesel jets [15, 16] or cryogenic injections under supercritical considerations [17]. The physical principle of radiography is the absorption of X-rays by the dense fluid. The transmission of X-rays thus depends on the mixture composition, i.e. the injected fluid and its surrounding. An advantage of X-ray absorption technique is that X-rays are not subject to deflection due to optical index gradients, contrary to laser-based techniques, and the attenuation of the transmitted light is proportional to the mass of fluid crossed by the X-ray beam

Etude de l'interaction cinétique chimique/turbulence dans une flamme cryotechnique LOx/CHA4

Le travail de cette thèse porte sur la modélisation de la combustion du méthane et de l oxygène dans des conditions de pression et température typiques de celles rencontrées au sein des moteur-fusées. Pour cette application, des modèles de transports, de thermodynamiques et des équations d état de type gaz réel ont été implémentés au sein du code de calcul compressible utilisé. Le formalisme des conditions aux limites a été étendu aux gaz réels. La validation de l ensemble de cette modélisation a été effectuée. Pour la modélisation de la combustion, une méthode de chimie tabulée a été considérée. La méthode de calcul de la température TTC a été choisie et étendue au formalisme des gaz réels. Deux formes pour la tabulation de l équation d état gaz réel ont été proposées. Le formalisme du couplage entre la thermodynamique tabulée et les conditions aux limites caractéristiques est établi puis validé. L étude de l interaction chimie-turbulence au sein de la combustion LOx/CH4 à haute pression a ensuite été menée au travers de simulations basées sur des essais expérimentaux effectués sur le banc MASCOTTE de l ONERA.This work focuses on the methane and oxygene combustion modelisation under conditions typically uncountered in rocket engines. Modelisation under such conditions requires high pressure models for equation of state and transport and thermodynamic properties evaluation. Those models are implemented in the compressible CFD code used during this thesis and validated. Characteristic boundary conditions are also extended to high pressure formulation. The PCM-FPI method coupled with the TTC method for the temperature computation are chosen to model the combustion. Coupling between this evolved model and characteristic boundary conditions formulation is extended to the high pressure framework. Then the study of interaction between chemical kinetic and turbulence in a oxygen/methane high pressure flame is realised through simulations based on ONERA MASCOTTE test bench cases.ROUEN-INSA Madrillet (765752301) / SudocSudocFranceF

Real-gas effects on fluid injection: numerical and experimental study

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Real-gas effects on fluid injection: numerical and experimental study

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Large eddy simulation of supersonic H2-O2 combustion

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La science des nuages : entre représentation artistique et phénomène météorologique

The Science of Clouds : Between Artistic Representation and Meteorological Phenomenon The cloud motif appears throughout the history of European painting. The present article is a study of the significance of clouds in 19th-century painting and more precisely in John Constable’s work, during a period of a growing interest in meteorology, at the time of its beginnings. As weather-related observations became more and more frequent, artists such as Constable participated in the phenomenon in which society as a whole developed a passion for weather reports. He was thus a pioneer and especially a paragon of a larger movement at the junction of science, philosophy and aesthetics. Indeed, a deliberate combination of picturesque rendering and objective representation associated to depict real weather phenomena can be observed in his work. The painter was familiar with Luke Howard’s classification (Essay on the Modifications of Clouds, 1803) either first or second hand. Moreover he owned an edition by the astronomer Thomas Forster (Researches about Atmospheric Phenomena, 1812) which he had annotated himself. It is therefore the authors’ goal to reconsider the work of this painter who hoped to create “a natural history of skies” by studying his paintings within the context of the rising science of meteorology during the 19th century.Le nuage traverse l’histoire de la peinture occidentale. Les auteurs proposent d’étudier spécifiquement sa place dans la peinture du XIXe siècle et plus précisément dans l’œuvre de John Constable, à une époque où commence à se faire jour un intérêt croissant pour la science météorologique balbutiante. En effet, les observations météorologiques étaient de plus en plus courantes au XIXe siècle et des artistes comme Constable participèrent de ce phénomène où la société dans son ensemble fut prise de passion pour les relevés. Il s’inscrit dans un mouvement plus large au confluent de la science, de la philosophie et de l’esthétique, mais il en est à la fois l’un des précurseurs et surtout le parangon. On constate en effet dans son œuvre une volonté d’entremêler le dessin pittoresque à la représentation objective traduisant un phénomène météorologique réel. Le peintre connaissait d’ailleurs la classification de Luke Howard (Essay on the Modifications of Clouds, 1803), de première ou de seconde main, et possédait en outre une édition de l’ouvrage de l’astronome Thomas Forster (Researches about Atmospheric Phenomena, 1812) qu’il avait annotée. Il s’agit donc de reconsidérer particulièrement l’œuvre de celui qui souhaitait faire une « Histoire naturelle des deux » en la replaçant dans l’histoire de la météorologie naissante au XIXe siècle.Mosseron Maxence, Ribert Guillaume. La science des nuages : entre représentation artistique et phénomène météorologique. In: Histoire de l'art, N°67, 2010. Art, science et technologie. pp. 19-32

Modeling and simulation of supercritical flows

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Modelling and simulation of high-pressure flows

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Direct Numerical Simulation and Large-Eddy Simulation of Supersonic Channel Flow

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