Conception et étude expérimentale et numérique d'un système de contrôle de trajectoire et mélange des jets de gaz dans les brûleurs à oxygène.

Le contrôle de flammes multi-jets est étudié dans cette thèse et appliqué à des oxy-brûleurs à jets séparés d’Air Liquide. Le procédé de contrôle en question consiste à dévier un jet gazeux axisymmétrique par une injection transverse du même gaz. Un actionneur a été spécifiquement conçu à l'MFT pour réaliser cette injection et provoquer des déviations de jet de forte amplitude. L’aérodynamique de l’écoulement d’un injecteur à deux jets, équipés de ces actionneurs, a été étudiée expérimentalement et numériquement. Deux configurations différentes ont montré la capacité des actionneurs à améliorer le mélange des réactifs et contrôler la trajectoire globale de l’écoulement. Les visualisations expérimentales et les mesures par anémométrie à fil chaud coïncident avec les résultats du calcul LES, obtenus avec le code AVBP. Des calculs réactifs d’une configuration à trois jets ont aussi été menés ; comparés à des résultats expérimentaux du CORIA, ils montrent l’effet de l'ncidence des jets sur la structure de flamme et prouvent la capacité de la LES à capturer ces phénomènes. Au niveau industriel, un brûleur pilote de 1 MW a été équipé avec les actionneurs conçus à l'MFT. Les tests de ce brûleur ont prouvé l’efficacité des actionneurs pour orienter les transferts thermiques de la flamme vers une charge et ont aussi mis en évidence une augmentation nette du rendement thermique de ce brûleur par rapport à une configuration non-actionnée. En conséquence, le système et le procédé de contrôle à l’aide d’actionneurs ont été brevetés. ABSTRACT : This work deals with the control of multi-jet flames for an application to oxy-fuel multi-jet burners. The generic type of control that is studied here is an axisymmetric jet being vectored by a transverse fluid injection. An actuator, designed at IMFT, carries out this injection and gives a large amplitude to the jet deviation. The aerodynamics of the flow issuing from a double-jet injector, geared with actuators, is then studied experimentally and numerically. Two different flow configurations prove the ability of the actuator to enhance mixing and to control the trajectory of the global flow. The experimental visualization and quantitative measurements, achieved with hot-wire velocimetry, are retrieved well by the Large Eddy Simulations, performed with the code AVBP. Reactive calculations on a three-jet configuration are also undertaken. When compared to experimental results from CORIA, these calculations show the effect of jet incidence on the flame structure and prove the ability of LES to capture such phenomena. At the industrial level, a 1-MW pilot burner has been outfitted with the IMFT actuators. Tests of this burner prove the effectiveness of the actuators to orient the heat transfer from the flame to a load, and exhibit better overall performance than a "straight-flame" burner. As a result of these tests, the system and process of control have been patented

Whole-Body CT after Motor Vehicle Crash: No Benefit after High-Energy Impact and with Normal Physical Examination

Background Debate continues about the risks and benefits of systematic whole-body CT when no injury is clinically suspected. Risks of whole-body CT include high radiation exposure and iodine contrast agent, but its effectiveness in reducing mortality in low-risk motor vehicle crashes is unclear. Purpose To assess unsuspected injuries revealed at whole-body CT in patients following motor vehicle crash (MVC) meeting only kinetic elements of the Vittel criteria for the severity of trauma, with no evidence of trunk injury and a Glasgow Coma Scale score of 15. Materials and Methods This retrospective study included all consecutive adult patients who consulted an emergency department of a level 1 trauma center between August 2016 and July 2017 if they underwent whole-body CT for one or more kinetic elements of the Vittel criteria, had a normal examination of the trunk, and had a Glasgow Coma Scale score of 15. Data of the MVC mechanism and physical and biologic examinations were collected, as well as patient treatment data after whole-body CT. Whole-body CT examinations were read by two double-blinded readers to help detect unsuspected injuries. Results Ninety-three patients were included; 72 were men with a mean age of 30.8 years ± 12.0 (standard deviation). Sixty-nine patients were occupants of a car. Seventeen patients were hit by a car while on motorbikes, three while on bicycles, and four as pedestrians. Unsuspected injuries were depicted at 11 whole-body CT examinations: eight lung contusions, one acetabular fracture, one sternal fracture, and one adrenal hematoma. None of these injuries required a specific treatment. One patient with lung contusion of more than 30% of lung volume was followed without requiring further treatment. Conclusion In this population, whole-body CT did not lead to any change in patient treatment. These results suggest whole-body CT should not be systematically performed when no evidence of trunk injury is observed in patients following motor vehicle crash meeting only kinetic elements of Vittel criteria. © RSNA, 2019 See also the editorial by Munera and Durso in this issue

Étude expérimentale et numérique de l'allumage des turboréacteurs en conditions de haute altitude

Le développement et la certification de systèmes propulsifs aéronautiques nécessitent une phase d'essais sur banc moteur. Ces essais permettent entre autres de caractériser les limites d'allumage des foyers de combustion de turbomachines, mais sont extrêmement coûteux et générateurs de délais pour l'industriel. Afin de limiter leur recours, il est nécessaire de développer des méthodes permettant de prévoir de la façon la plus fiable possible les performances d'allumage d'un prototype de chambre de combustion, et ce aussi bien pour des conditions de décollage au niveau de la mer que pour le cas critique de la haute altitude.L'objectif de cette thèse est de contribuer au développement et à la validation d outils numériques pour la prévision de l'allumage des foyers de combustion à partir de données expérimentales obtenues sur le banc MERCATO de l ONERA. Ces travaux ont été conduits en étroite coopération avec TURBOMECA. Des améliorations ont été apportées à un modèle permettant de simuler l'allumage d'un brouillard de carburant suite à un dépôt d'énergie par bougie à arc électrique. Ce modèle a été couplé à un code de calcul multiphysique (code CEDRE) afin d'établir des cartographies d'allumage à partir d'un champ aérodiphasique moyenné, mais également de simuler la phase de propagation de la flamme à l ensemble du foyer par approche RANS pseudo-stationnaire. Afin de valider ces deux approches, une caractérisation expérimentale d'une maquette de chambre mono-secteur a été réalisée sur le banc d'essai MERCATO. Ces essais ont permis de constituer une banque de données très fournie pour différents cas tests. La comparaison de la cartographie d allumage expérimentale à celle fournie par la simulation numérique donne des résultats très satisfaisants et encourageants en vue d une application à un foyer réel de turbomachine. En parallèle, des résultats très prometteurs ont été obtenus sur une nouvelle maquette de chambre de combustion trisecteur,dérivée d'un foyer industriel, permettant de comparer ses limites d allumage à celles obtenues sur la chambre réelle. Cette configuration fera l objet par la suite d une étude détaillée de la propagation de la flamme intersecteurs, impossible à réaliser sur la géométrie d'un foyer annulaire complet.Design of aircraft engines requires tests on engine benches. These tests allow characterizing combustor ignition limits, but are extremely expensive and time consuming. In order to limit their number, it is necessary to develop alternative methods enabling to predict the ignition performances of a combustor prototype, for both ground conditions and high altitude conditions, the latter being particularly critical.The purpose of this thesis is to contribute to the development and validation of numerical tools enabling to predict ignition performances of combustor. Validation will be possible using an experimental data base obtained on the MERCATO test bench, at ONERA. This work results from a close cooperation with TURBOMECA. A numerical model, previously developed to predict the ignition of fuel spray following a spark discharge, has been improved. This model has been combined to a multiphysics CFD code (CEDRE) in orderto build ignition map from a mean two-phase flow field, and also to compute the flame propagation stage using RANS approach. In order to validate both methods, experimental characterization of a one-sectorcombustor has been performed on the MERCATO test rig. A complete data base for validation of CFD code isnow available. Comparison of experimental and numerical ignition mapping showed good agreements for the different tests cases, and seems encouraging for an application on an industrial combustor. In the same time,promising results have been obtained with a new experimental three-sector combustor. Its geometry is basedon an industrial combustor, allowing a comparison of ignition performances between the simplified and the industrial combustorsTOULOUSE-ISAE (315552318) / SudocSudocFranceF

A respiratory-gated micro-CT comparison of respiratory patterns in free-breathing and mechanically ventilated rats

© 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. In this study, we aim to quantify the differences in lung metrics measured in free-breathing and mechanically ventilated rodents using respiratory-gated micro-computed tomography. Healthy male Sprague-Dawley rats were anesthetized with ketamine/xylazine and scanned with a retrospective respiratory gating protocol on a GE Locus Ultra micro-CT scanner. Each animal was scanned while free-breathing, then intubated and mechanically ventilated (MV) and rescanned with a standard ventilation protocol (56 bpm, 8 mL/kg and PEEP of 5 cm H2O) and again with a ventilation protocol that approximates the free-breathing parameters (88 bpm, 2.14 mL/kg and PEEP of 2.5 cm H2O). Images were reconstructed representing inspiration and end expiration with 0.15 mm voxel spacing. Image-based measurements of the lung lengths, airway diameters, lung volume, and air content were compared and used to calculate the functional residual capacity (FRC) and tidal volume. Images acquired during MV appeared darker in the airspaces and the airways appeared larger. Image-based measurements showed an increase in lung volume and air content during standard MV, for both respiratory phases, compared with matched MV and free-breathing. Comparisons of the functional metrics showed an increase in FRC for mechanically ventilated rats, but only the standard MV exhibited a significantly higher tidal volume than free-breathing or matched MV. Although standard mechanical ventilation protocols may be useful in promoting consistent respiratory patterns, the amount of air in the lungs is higher than in free-breathing animals. Matching the respiratory patterns with the free-breathing case allowed similar lung morphology and physiology measurements while reducing the variability in the measurements

A test facility for assessing simulations of jets in cross flow configurations

International audienceA test facility featuring jet(s) in cross flow con-figuration is presented. The peculiarity of the rig stems from the presence of an acoustic forcing sys-tem that introduces planar acoustic waves in the cross flow. Microphones, PIV and LDV measure-ments have been conducted in forced and unforced configurations. The experimental database built so far already gives the possibility of assessing in depth the predictive capability of related steady or unsteady simulations

Investigating lung responses with functional hyperpolarized xenon-129 MRI in an ex vivo rat model of asthma

Purpose: Asthma is a disease of increasing worldwide importance that calls for new investigative methods. Ex vivo lung tissue is being increasingly used to study functional respiratory parameters independent of confounding systemic considerations but also to reduce animal numbers and associated research costs. In this work, a straightforward laboratory method is advanced to probe dynamic changes in gas inhalation patterns by using an ex vivo small animal ovalbumin (OVA) model of human asthma. Methods: Hyperpolarized (hp)129Xe was actively inhaled by the excised lungs exposed to a constant pressure differential that mimicked negative pleural cavity pressure. The method enabled hp129Xe MRI of airway responsiveness to intravenous methacholine (MCh) and airway challenge reversal through salbutamol. Results: Significant differences were demonstrated between control and OVA challenged animals on global lung hp129Xegas inhalation with P < 0.05 at MCh dosages above 460 µg. Spatial mapping of the regional hp gas distribution revealed an approximately three-fold increase in heterogeneity for the asthma model organs. Conclusion: The experimental results from this proof of concept work suggest that the ex vivo hp noble gas imaging arrangement and the applied image analysis methodology may be useful as an adjunct to current diagnostic techniques

Analysis of body mass index, weight loss and progression of idiopathic pulmonary fibrosis

Background: Nintedanib is an approved therapy for idiopathic pulmonary fibrosis (IPF). Some patients treated with nintedanib experience weight loss. Exploratory data suggest that low body mass index or weight loss are associated with worse outcomes in patients with IPF. We investigated whether BMI at baseline or weight loss over 52 weeks was associated with FVC decline, or influenced the effect of nintedanib, in patients with IPF. Methods: Using pooled data from the two INPULSIS trials, we analysed the rate of decline in FVC (mL/yr) over 52 weeks in patients treated with nintedanib and placebo in subgroups by baseline BMI ( 5%) using random coefficient regression. Results: In the placebo group, the mean rate of FVC decline over 52 weeks was numerically greater in patients with lower baseline BMI (− 283.3 [SE 22.4], − 207.9 [20.9] and − 104.5 [21.4] in patients with BMI 5% than ≤5% weight loss over 52 weeks (− 312.7 [SE 32.2] versus − 199.5 [SE 14.4] mL/year). Nintedanib reduced the rate of FVC decline versus placebo in both subgroups by weight loss, with a greater treatment effect in patients with > 5% weight loss (interaction p = 0.0008). The adverse event profile of nintedanib was similar across subgroups. Conclusions: In patients with IPF, lower BMI and weight loss may be associated with faster decline in FVC. Nintedanib reduces the rate of FVC decline both in patients who lose weight on treatment and those who do not. Trial registration: ClinicalTrials.gov; Nos. NCT01335464 and NCT01335477; URL: www.clinicaltrials.gov