143 research outputs found
Pyrolysis in porous media: Part 1. Numerical model and parametric study
No full textTranspiration cooling of structures by means of hydrocarbon fuel is a way to sustain the large heat load encountered in combustion chambers. An European collaboration has been set up to investigate the fluid flow through porous media by means of numerical simulation in order to help analysing the experimental results obtained under pyrolysis regime (1200 K, 6 MPa). A parametric study is conducted to understand the effect of numerical modelling of velocity in the porous media, multi-component diffusion, the deployment of in situ adaptive tabulation for chemistry and the use of perfect or real fluid properties. Due to the complexity of multi-physics phenomena, this work intends to ensure the reliability of the calculations before comparing them with experiments. Two semi-detailed kinetic schemes for dodecane pyrolysis (up to 15 species and 20 reactions) are tested. © 2013 Elsevier Ltd. All rights reserved.sponsorship: This work was supported by the ESA-ESTEC, Contract No.: 3-12861/09/NL/PA. The authors would like to sincerely thank F. Travajno and B. Le Naour from MBDA-France, G. Fau, P. Gillard and C. Strozzi from PRISME, D. Blanc and D. Courilleau from IUT Bourges, D. Davidenko from CNRS-ICARE Orleans, A. Ingenito from the University of Rome La Sapienza (Italy) and all the students involved in the projects head by I. Fedioun for their technical and scientific support involving the computations and the experiments. (ESA-ESTEC|3-12861/09/NL/PA)status: Publishe
Étude numérique du transitoire d'injection adapté au fonctionnement d'un moteur fusée à détonation rotative
No full textInternational audienceDetonation applied to propulsion could result in a promising increase of the thermodynamic efficiency of the engine cycle. Numerical simulations of the detonation propagating in the Continuous Detonation Wave Rocket Engine (CDWRE) are currently performed but still do not account for realistic injection process. The assumption of an ideal injected premix is generally chosen for convenience to obtain theoretical results. Comparison of the numerical results with experiments is difficult because of the clear difference of the injection configurations. Some physical aspects of the separate injection of the components used in experiments are not clearly assessed. This study is included in a wider numerical project aimed at designing and optimizing a realistic CDWRE. The optimization process is presently focused on the injector. One element of the injection hole pattern is considered assuming that this element is periodically repeated over the injector head. The aim of the work presented here is to model and analyze the refill process of the components in the combustion chamber behind the rotating detonation. The simulation starts just after the passage of the detonation over the considered injection element. This simulation gives information on the way the injected propellants recreate the reactive mixture for the next detonation. In the first step, two-dimensional (2D) computations helped us to set up the methodology and to study the dynamic response of the fresh components injected. A comparison between 2D homogeneous and separate injections is provided. In the second step, three-dimensional (3D) computations have been performed with a separate injection suitable for the CDWRE operation. Some performance parameters are evaluated such as mixing efficiency or filling of the domain.La détonation appliquée à la propulsion pourrait conduire à une augmentation prometteuse du rendement thermodynamique du cycle moteur. Les simulations numériques actuelles de la propagation d'une détonation dans un moteur fusée à détonation rotative (CDWRE) ne tiennent pas compte d'une injection réaliste en majorité. On adopte généralement l'hypothèse simplificatrice de l'injection d'un prémélange pour obtenir des résultats théoriques. La comparaison entre les résultats numériques et expérimentaux est difficile par la nette différence entre les configurations d'injection utilisée. Quelques aspects physiques de l'injection séparée des ergols utilisée dans les expériences ne sont pas encore bien connus. Cette étude est incluse dans un projet numérique plus large destiné à concevoir et optimiser un CDWRE réaliste. La procédure d'optimisation est ici centrée sur l'injecteur. Un élément du motif d'injection constitué de trous est considéré en supposant que cet élément est périodiquement répété sur le plan d'injection. Le but de ce travail est de modéliser et d'analyser le processus de réinjection des ergols dans la chambre de combustion derrière la détonation rotative. La simulation commence juste après le passage de la détonation au-dessus de l'élément d'injection considéré. Cette simulation donne des informations sur la façon dont l'injection des ergols permet de recréer la couche de mélange réactive pour la prochaine détonation. Premièrement, des simulations 2D ont permis de mettre en place la méthodologie et d'étudier la réponse dynamique du mélange frais injecté. Une comparaison entre les résultats 2D d'injections homogène et séparée est montrée. Ensuite, des simulations 3D ont été réalisées avec une injection séparée adaptée au fonctionnement du CDWRE. Quelques indices de performance sont évalués comme l'efficacité de mélange et le remplissage du domaine
Optimization of supersonic axisymmetric nozzles with a center body for aerospace propulsion
No full textThis study is aimed at optimization of axisymmetric nozzles with a center body, which are suitable for thrust engines having an annular duct. To determine the flow conditions and nozzle dimensions, the Vinci rocket engine is chosen as a prototype. The nozzle contours are described by 2nd and 3rd order analytical functions and specified by a set of geometrical parameters. A direct optimization method is used to design maximum thrust nozzle contours. During optimization, the flow of multispecies reactive gas is simulated by an Euler code. Several optimized contours have been obtained for the center body diameter ranging from 0.2 to 0.4 m. For these contours, Navier-Stokes (NS) simulations have been performed to take into account viscous effects assuming adiabatic and cooled wall conditions. The paper presents an analysis of factors influencing the nozzle thrust
Numerical simulation of a Rotating Detonation with a realistic injector designed for separate supply of gaseous hydrogen and oxygen
No full text
Numerical Optimisation in Non Reacting Conditions of the Injector Geometry for a Continuous Detonation Wave Rocket Engine
No full textInternational audienceThe paper presents the methodology and the results of a numerical study, which is aimed at the investigation and optimisation of different means of fuel and oxidizer injection adapted to rocket engines operating in the rotating detonation mode. As the simulations are achieved at the local scale of a single injection element, only one periodic pattern of the whole geometry can be calculated so that the travelling detonation waves and the associated chemical reactions can not be taken into account. Here, separate injection of fuel and oxidizer is considered because premixed injection is handicapped by the risk of upstream propagation of the detonation wave. Different associations of geometrical periodicity and symmetry are investigated for the injection elements distributed over the injector head. To analyse the injection and mixing processes, a nonreacting 3D flow is simulated using the LES approach. Performance of the studied configurations is analysed using the results on instantaneous and mean flowfields as well as by comparing the mixing efficiency and the total pressure recovery evaluated for different configurations
Optimization of supersonic axisymmetric nozzles with a center body for aerospace propulsion
No full textInternational audienceThis study is aimed at optimization of axisymmetric nozzles with a center body, which are suitable for thrust engines having an annular duct. To determine the §ow conditions and nozzle dimensions, the Vinci rocket engine is chosen as a prototype. The nozzle contours are described by 2nd and 3rd order analytical functions and speci¦ed by a set of geometrical parameters. A direct optimization method is used to design maximum thrust nozzle contours. During optimization, the §ow of multispecies re-active gas is simulated by an Euler code. Several optimized contours have been obtained for the center body diameter ranging from 0.2 to 0.4 m. For these contours, Navier Stokes (NS) simulations have been performed to take into account viscous e¨ects assuming adiabatic and cooled wall conditions. The paper presents an analysis of factors in §uencing the nozzle thrust
Optimization of supersonic axisymmetric nozzles with a center body for aerospace propulsion
No full textInternational audienceThis study is aimed at optimization of axisymmetric nozzles with a center body, which are suitable for thrust engines having an annular duct. To determine the §ow conditions and nozzle dimensions, the Vinci rocket engine is chosen as a prototype. The nozzle contours are described by 2nd and 3rd order analytical functions and speci¦ed by a set of geometrical parameters. A direct optimization method is used to design maximum thrust nozzle contours. During optimization, the §ow of multispecies re-active gas is simulated by an Euler code. Several optimized contours have been obtained for the center body diameter ranging from 0.2 to 0.4 m. For these contours, Navier Stokes (NS) simulations have been performed to take into account viscous e¨ects assuming adiabatic and cooled wall conditions. The paper presents an analysis of factors in §uencing the nozzle thrust
First Observation of a narrow Charm-Strange Meson D+(SJ)(2632)-->D+(S) eta and D0 K+
No full textWe report the first observation of a charm-strange meson D-sJ(+)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D(s)(+)eta and (DK+)-K-0. In the D(s)(+)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode (DK+)-K-0. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma((DK+)-K-0)/Gamma(D(s)(+)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(s)(+)eta decay mode
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