High amplitude/high frequency acoustic field effects on coaxial inkection

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Acoustic response of an injection system to high-frequency transverse acoustic fields

International audienceThe acoustic coupling between the injection system and the acoustic fluctuations in liquid rocket engine combustion chambers is an important issue in the understanding of the thermo-acoustic instability phenomenon. This paper presents the results of a wide-ranging parametric investigation of the acoustic response of a two-phase injection system submitted to a forced high-amplitude transverse acoustic field. Two domes, one for the gas and one for the liquid, were expressly designed to feed three identical coaxial injectors. The internal mode shapes of the domes were characterized by measuring pressure signals at different locations in the domes. Experimental mode shapes showed good agreement with those predicted by numerical simulations. Acoustic pressure amplitudes up to 23% of those induced in the main cavity can be found in both the gas and liquid domes. The response efficiency in a dome depends on the position of the injectors' exit in the acoustic field

Comparison of LOX/Methane and LOX/Hydrogen cryogenic spray combustion with simultaneous optical diagnostics

International audienceONERA and CNES are collaborating to prepare the next engine generation for reusable launchers thatwill use liquid oxygen (LOX) and methane (CH4) as propellants. The present experimental study wascarried out on the MASCOTTE test bench located at ONERA, Palaiseau center. The main goal was tocharacterize the LOX jet, under reacting conditions, with simultaneous droplet-size measurements andhigh-speed chemiluminescence and shadowgraphy visualizations for two propellant couples:LOX/CH4 and LOX/H2, under similar operating conditions. High-speed visualizations were used toassign the locations of drop-size measurements obtained in the cryogenic jet flames, to explain theresults and to analyse the peculiarities of combustions with both propellants

La fonte lipidique du foie gras à la cuisson

La connaissance des facteurs biologiques, zootechniques et technologiques ainsi que des mécanismes qui contrôlent le taux de fonte des foies gras à la cuisson est primordiale pour la maîtrise du rendement technologique des foies gras. En effet, le taux de fonte à la cuisson a des répercussions sur les qualités organoleptiques des foies gras et sur les performances des unités de production

Diagnostics optiques simultanés pour l'étude de la combustion cryotechnique LOX/CH4

International audienceL’ONERA et le CNES contribuent à la préparation la future génération de moteurs pour lanceurs réutilisables qui seront propulsés par le couple d’ergols oxygène liquide (LOX) et méthane (CH4). La présente étude expérimentale, réalisée sur le banc MASCOTTE de l’ONERA, a pour but de montrer, du point de vue des diagnostics optiques, les particularités de la combustion cryotechnique de l’oxygène liquide et du méthane en comparaison de l’hydrogène gazeux (H2) [1], dans des conditions opératoires similaires, avec une pression dans la chambre de combustion de 10 bar. Pour ce faire, trois diagnostics optiques ont été mis en œuvre simultanément: l’interférométrie phase Doppler (PDI), la chimiluminescence du radical OH et l’ombroscopie à haute cadence. Les visualisations sont utilisées pour positionner les points de mesures PDI par rapport à la flamme et expliquer les différences constatées sur les taux de validation PDI dans les deux cas de combustibles

Prediction and analysis of combustion instabilities in a model rocket engine

This paper is a compilation of the research efforts of five different groups (Bertin Technologies and CNES, IMFT, ONERA, Purdue University and Technische Univer- sität München) on the prediction of combustion instabilities in a model rocket engine. This research was initiated by the REST group (Rocket Engine Stability iniTiative) for the 2nd REST Workshop on Combustion Instability Modeling, which took place in October 2010 at Astrium GmbH in Ottobrunn. The target experiment consists of a single shear coaxial injector using methane and decomposed hydrogen peroxide as reactants. Both the inlet of the injector and the outlet of the chamber are choked, resulting in well-defined acoustic boundary conditions. The length of the oxidizer tube could be varied continuously and its influence on the stability is studied. Many numerical strategies were tested, addressing different physical phenomena at play during unstable combustion. Acoustic solvers, both with and without mean-flow effects were used to draw stability maps. The weak spot of these solvers is that they require the flame response to acoustic perturbations as an input. Large-Eddy Simulations, requiring no such a priori knowledge, were performed with the intent to elucidate flame stabilization and flame response mechanisms

A Shift from Cellular to Humoral Responses Contributes to Innate Immune Memory in the Vector Snail Biomphalaria glabrata

International audienceDiscoveries made over the past ten years have provided evidence that invertebrate anti-parasitic responses may be primed in a sustainable manner, leading to the failure of a secondary encounter with the same pathogen. This phenomenon called " immune priming " or "innate immune memory" was mainly phenomenological. The demonstration of this process remains to be obtained and the underlying mechanisms remain to be discovered and exhaustively tested with rigorous functional and molecular methods, to eliminate all alternative explanations. In order to achieve this ambitious aim, the present study focuses on the Lophotrochozoan snail, Biomphalaria glabrata, in which innate immune memory was recently reported. We provide herein the first evidence that a shift from a cellular immune response (encapsulation) to a humoral immune response (biomphalysin) occurs during the development of innate memory. The molecular characterisation of this process in Biompha-laria/Schistosoma system was undertaken to reconcile mechanisms with phenomena

Skin temperature influence on transcutaneous carbon dioxide (CO2) conductivity and skin blood flow in healthy human subjects at the arm and wrist

Objective: present transcutaneous carbon dioxide (CO2)—tcpCO2—monitors suffer from limitations which hamper their widespread use, and call for a new tcpCO2 measurement technique. However, the progress in this area is hindered by the lack of knowledge in transcutaneous CO2 diffusion. To address this knowledge gap, this study focuses on investigating the influence of skin temperature on two key skin properties: CO2 permeability and skin blood flow.Methods: a monocentric prospective exploratory study including 40 healthy adults was undertaken. Each subject experienced a 90 min visit split into five 18 min sessions at different skin temperatures—Non-Heated (NH), 35, 38, 41, and 44°C. At each temperature, custom sensors measured transcutaneous CO2 conductivity and exhalation rate at the arm and wrist, while Laser Doppler Flowmetry (LDF) assessed skin blood flow at the arm.Results: the three studied metrics sharply increased with rising skin temperature. Mean values increased from the NH situation up to 44°C from 4.03 up to 8.88 and from 2.94 up to 8.11 m·s−1 for skin conductivity, and from 80.4 up to 177.5 and from 58.7 up to 162.3 cm3·m−2·h−1 for exhalation rate at the arm and wrist, respectively. Likewise, skin blood flow increased elevenfold for the same temperature increase. Of note, all metrics already augmented significantly in the 35–38°C skin temperature range, which may be reached without active heating—i.e. only using a warm clothing.Conclusion: these results are extremely encouraging for the development of next-generation tcpCO2 sensors. Indeed, the moderate increase (× 2) in skin conductivity from NH to 44°C tends to indicate that heating the skin is not critical from a response time point of view, i.e. little to no skin heating would only result in a doubled sensor response time in the worst case, compared to a maximal heating at 44°C. Crucially, a skin temperature within the 35–38°C range already sharply increases the skin blood flow, suggesting that tcpCO2 correlates well with the arterial paCO2 even at such low skin temperatures. These two conclusions further strengthen the viability of non-heated tcpCO2 sensors, thereby paving the way for the development of wearable transcutaneous capnometers

Influence of 'Trichobilharzia regenti' (Digenea: Schistosomatidae) on the defence activity of 'Radix lagotis' (Lymnaeidae) haemocytes

Radix lagotis is an intermediate snail host of the nasal bird schistosome Trichobilharzia regenti. Changes in defence responses in infected snails that might be related to host-parasite compatibility are not known. This study therefore aimed to characterize R. lagotis haemocyte defence mechanisms and determine the extent to which they are modulated by T. regenti. Histological observations of R. lagotis infected with T. regenti revealed that early phases of infection were accompanied by haemocyte accumulation around the developing larvae 2–36 h post exposure (p.e.) to the parasite. At later time points, 44–92 h p.e., no haemocytes were observed around T. regenti. Additionally, microtubular aggregates likely corresponding to phagocytosed ciliary plates of T. regenti miracidia were observed within haemocytes by use of transmission electron microscopy. When the infection was in the patent phase, haemocyte phagocytic activity and hydrogen peroxide production were significantly reduced in infected R. lagotis when compared to uninfected counterparts, whereas haemocyte abundance increased in infected snails. At a molecular level, protein kinase C (PKC) and extracellular-signal regulated kinase (ERK) were found to play an important role in regulating these defence reactions in R. lagotis. Moreover, haemocytes from snails with patent infection displayed lower PKC and ERK activity in cell adhesion assays when compared to those from uninfected snails, which may therefore be related to the reduced defence activities of these cells. These data provide the first integrated insight into the immunobiology of R. lagotis and demonstrate modulation of haemocyte-mediated responses in patent T. regenti infected snails. Given that immunomodulation occurs during patency, interference of snail-host defence by T. regenti might be important for the sustained production and/or release of infective cercariae

L'écriture inclusive et ses usages dans les revues de sciences humaines et sociales

Le langage inclusif est depuis quelques années en débat dans l'espace public. L'écriture scientifique n'échappe pas aux questions soulevées par ces nouvelles formes d'écriture qui s'inscrivent dans un mouvement de visibilisation des femmes, de remise en question du masculin « neutre » et de lutte contre le sexisme et les inégalités de genre. L'article présente les résultats d'une enquête exploratoire auprès de revues de SHS, dont l'objectif est de rendre compte des usages actuels de l'écriture inclusive dans ces revues. L'enquête indique que l'écriture inclusive (EI) est d'un usage largement accepté sur le principe par les revues étudiées, mais celles-ci communiquent peu sur leurs règles éditoriales en matière d'EI et publient des textes utilisant des formes variables et non stabilisées de cette nouvelle forme d'écriture. Mots-clé : Écriture inclusive, revues SHS, édition, langage Non-sexist writing and its uses in humanities and social sciences journal