Academic literature on the topic 'Écoulement réactif prémélangé'
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Dissertations / Theses on the topic "Écoulement réactif prémélangé":
Albouze, Guillaume. "Simulation aux grandes échelles des écoulements réactifs non prémélangés." Phd thesis, Toulouse, INPT, 2009. http://oatao.univ-toulouse.fr/7796/1/albouze.pdf.
Robin, Vincent. "Contribution à la modélisation des écoulements turbulent réactifs partiellement prémélangés." Phd thesis, Université de Poitiers, 2007. http://tel.archives-ouvertes.fr/tel-00258526.
Les modèles développés ici sont implantés dans le logiciel de mécanique des fluides numérique Code-Saturne et validés en utilisant tout d'abord la configuration ORACLES du LCD puis la flamme en V turbulente étudiée expérimentalement au CORIA. Ces deux dispositifs expérimentaux permettent l'étude de la combustion partiellement prémélangée. Les simulations numériques de ces deux écoulements, utilisant le modèle LW-P, ont donné des résultats en bon accord avec les données expérimentales.
Robin, Vincent. "Contribution à la modélisation des écoulements turbulents réactifs partiellement prémélangés." Poitiers, 2007. http://www.theses.fr/2007POIT2303.
The present study is devoted to the numerical modeling of turbulent reactive flows in situations where reactants are not ideally premixed. In this case, the description of the local thermochemistry requires at least two variables. Here we chose the mixture fraction to describe the local composition of fresh mixture and the fuel mass fraction Y to evaluate the progress of the chemical reaction. The numerical model is based on the LW-P analysis but here the joint velocity-scalar discrete PDF made of Dirac delta functions is considered in the context of a second order modeling. New algebraic closures for the scalar dissipation terms are proposed to represent the mixing at small scales. Special attention is paid to the closure of pressure fluctuating terms which appear in the turbulent transport equations. The proposed closure is able to take into account the counter-gradient diffusion and flame generated turbulence effects. Numerical simulations are performed with the CFD code Code-Saturne and the model is validated using first the experimental configuration ORACLES from LCD and second the turbulent V-shaped flame studied at CORIA. Numerical results obtained for these two configurations are in good agreement with experimental data in both cases of perfectly and partially premixed turbulent reactive flows
Matino, Alessandra. "Characterisation of the Early Ignition Phase Generated by a Sunken Fire Igniter." Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2024. http://www.theses.fr/2024ESMA0008.
Environmental restrictions tackle the reduction of the use of primary sources of energy motivating research to advance towards upgraded technologies. Alongside with these efforts, reliability and performance need to be ensured, especially for detrimental conditions of pressure and temperature, i.e. high altitude. In gas turbine engines, both these elements are crucial to offer products that fit to both the needs and expectations set by the present scenario. Ignition is a multiphase process constituted by several phases and events that span a diversified range of characteristic time scales. The numerical resolution of the early ignition phase, for which fine and detailed information is lacking, is investigated in this study. The efficiency of the igniter is estimated through calorimetry in pure air, which shows that variations of initial pressure have an influence on efficiency. The same investigation revealed that temperature (20° C; - 20°C) has a negligible effect. Physical properties of the kernel in terms of volume, surface, projection surface, radius of the arc channel in the cavity, are estimated adopting different optical diagnostics, including schlieren and shadowgraphy imaging at 1 MHz. Calculations are done to obtain a temporal evolution during energy depositing time (130 μs). An effect of initial pressure is observed on kernel properties such that reducing the initial pressure, kernel volume increases. Furthermore, filtered direct visualizations of the igniter cavity show that an effect of pressure is discerned from 20 μs. Kernel size is also measured for methane premixed mixtures of different equivalence ratios. This is intended to determine the influence of composition variation with respect to a reference case in pure N2 which is compared to measurements in gaseous premixed mixtures (both of inert CH4 / N2 and reactive CH4 / O2 / N2 nature). A comparison between inert and reactive cases exposes active combustion reactions already during energy deposition. To investigate the exposure to real life environment elements, the impact of a transverse flow at ambient conditions is studied in a wind tunnel. This was adapted to simulate the combined effect of a transverse flow and cooling air spilled from the liner that the igniter is exposed to by being mounted in a sleeve. The effect of the sleeve on kernel projection is investigated, which reveales an impact on projection and kernel deformation depending on the imposed velocity. The generation of the kernel is examined in a reactive premixed swirled mixture at 0.45 and 1 bar. The velocity field have been studied beforehand by PIV to know the velocity in the vicinity of the igniter and in the spatial domain where the kernel is projected. Three velocity conditions are retained to perform the discharge. Initial pressure is observed to influence the deformation the kernel undergoes depending on initial velocity. At 1 bar, the kernel appears to be preserved for longer. A secondary effect of equivalence ratio is found. The existing model of Taylor-Sedov is tested to predict kernel properties and compare them to experimental measurements. A preliminary study is performed to explore the interaction between the kernel and a spray at 0.45 bar and 1 bar. High magnification shadowgraphy is used to run statistics on a spatial window of 2 x 2 cm where droplets are observed impinging on the electrodes. Properties variations are detected depending on the synchronization with the discharge. Schlieren visualizations are further performed to observe phenomena to qualitatively explore the dynamics appearing in a time window of 1 ms
Roche, Bruno. "Prédiction numérique des écoulements turbulents réactifs : Flamme turbulente oblique prémélangée et interaction flamme/tourbillons." Ecully, Ecole centrale de Lyon, 1995. http://www.theses.fr/1995ECDL0028.
The analysis and modelisation of the turbulent combustion is an important step for the study and simulation of industrial devices such as reciprocating engines of burners. The problem complexity is linked to the interaction between the thermo-chemical phenomena of the flame front and the scales of the turbulence spectrum. This problem can be simplified if we discretize the turbulence spectrum by treating each turbulent scale as a vortex. Our work in this domain follows two main axis : the prediction of a turbulent flame front and the simulation between an oblique flame front and a von Karman vortex street. The first part starts with the simulation of a laminar reference case. Then, the turbulent premixed oblique flame front is studied. The problem of the Lewis number influence on the flame structure is treated using two cases of mixing, hydrogen-air and methane-air. In a second part, we study the interaction between laminar premixed hydrogen-air oblique flame front and a von Karman vortex street. The prediction of this phenomenon show the vortex influence on the wrinkling and the extinction of the flame front. For each step, the comparison between numerical predictions and experimental data is realized. It allows us to analyze the performance of the modelisations and gives complementary data on the studied phenomena
Nguyen, Phuc Danh. "Contribution expérimentale à l'étude des caractéristiques instationnaires des écoulements turbulents réactifs prémélangés stabilisés en aval d'un élargissement brusque symétrique." Poitiers, 2003. http://www.theses.fr/2003POIT2295.
Corvellec, Catherine. "Etude numérique et analytique des caractéristiques propagatives d'une zone de combustion se développant au sein d'un écoulement turbulent prémélangé modélisée par une approche de type "flammelette"." Poitiers, 1998. http://www.theses.fr/1998POIT2337.