Papers by Daniel Desbordes
Annales de Physique, 1989
A technique for establishing oblique detonations at hypersonic velocities is described. The techn... more A technique for establishing oblique detonations at hypersonic velocities is described. The technique is used to produce oblique detonations in C 2H2-air at an equivalence ratio of 0.75 (normal CJ velocity = 1770 m/s) at a velocity of 3300 m/s.
Journal of Hazardous Materials, 1993
This paper reviews laboratory, balloon and open-field experiments, which have been performed to s... more This paper reviews laboratory, balloon and open-field experiments, which have been performed to study the deflagration regime in free air. In the first part, the paper considers briefly the different models available to estimate deflagrative unconfined explosion effects, without turbulence. Then a description is given of the known tests conducted, which indicates the effective scale of the various experiments, their operating conditions and the kind of the measurements done. The main results are presented and discussed in some detail to assess the role on the explosion yields of important parameters such as the fuel concentration gradients, the shape and size of the inflammable mixture, and the ignition energy. The overall conclusion of this survey is that inflammable mixtures drifting over open field and ignited, will burn with a low flame speed and consequently will generate very weak pressure effects.
Acta Astronautica, 1978
R~sun:~ On a cherch6 ~ pr6ciser et ~ comparer les caract6ristiques de la perturbation (amplitude,... more R~sun:~ On a cherch6 ~ pr6ciser et ~ comparer les caract6ristiques de la perturbation (amplitude, dur6e de la surpression ~+, c616rit6 de propagation) produite par I'explosion (d6flagration, d6tonation) des charges sph6riques de m61anges r6actifs gazeux, clans rair environnant. Les m61anges stricts d'ac6tylc~ne (AO) et d'6thyli~ne (EO) avec I'oxyg~ne, 6talent irdtialement confin6s ~ la pression et ~ la teml~rature ambiantes dans des bulles de savon de rayon Ro = 50 mm. L'explosion a 6t6 engendr6e au moyen d'6tincelles 61ectriques ou de ills explosifs plac6s au centre de la bulle. En faisant varier le rapport E = W/Q de 1'6nergie 61ectrique nominale W ~ 1'6nergie chimique Q de ia charge, de 0/t 4.5 10-3, on a pu observer syst6matiquement: (a) la d6flagration ~, c616rit6 de propagation de la flamme de plus en plus 61ev6e selon I'intensit6 de I'onde de choc cr6e par les dispositifs d'amorgage, (b) ia d6tonation, fortune tr~s rapidement ou quasi instantan~ment, clans la charge. La visualisafion par chronostriographie de l'6volution spatiotemporelle des ph6nomc~nes ~ l'int&ieur et A I'ext6rieur de la charge et les enregistrements de la pression ont permis, en particulier, les constatations suivantes: (I) scion que ~ est sup~rieur ou inf6rieur i une certalne valeur ~o (2.4 10-3 pour le m61ange AO, 3 x 10-3 pour EO) on observe au sein de la charge une d6tonation ou une d6flagration. La c616rit6 de la d6tonation est sensiblement constante Iorsque le front a un rayon RF > 0.2 Ro. Dam les cas de d6flagrafion, la c616rit~ Dr absolue du front de flamme est quasi constante apr~s un parcours de I'ordre du quart du rayon final R~ (-!.6-1.7Ro) de la charge. Elle est, pour le m61ange AO, ind6pendante de ~ (D~-120m/s) Iorsque e < 1.5 10 .3 et croft avec ~ jusqu'/t 200m/s Iorsque > 1.5 10-3; pour le m61ange EO, Dr croi't ~gulii~rement avec E de 100/t 200 m/s. (2) ies surpressions maximales Apt propsg~es par l'onde a~rienne fls engendr~e par ia d~flagration lorsqu'eHe atteint la fronti~re de la charge (Re = Rz) sont pour R~ ~ R ~ 30 Ro, inf6rieures i ceHe de I'onde de souffle produite par la d~tonafion. Cependant, ~ tome distance R > 10 Ro du centre de la charge, ces surpressions sont prafiquement identiques lorsque la c~l~rit~ du front de la flamme tend vers la valeur maximale observ6e (D~ 200 m/s pour AO et EO). (3) a des distances du centre R >R~ (R~: distance oO I'onde de choc llt g~n6r~e en (~ a rattrap~ I'onde l~c produite en R = 0 au moment de I'inflammation de la charge) ii n'est plus possible de d6duire de I'examen d'un enregistrement de pression si la charge a 6t6 le sic~ge d'une d6tonation ou d'une d~flagration.
Dynamics of Explosions, 1986
The present research, carried out in the framework of a French working group CEA-EDF-ENSMA, was d... more The present research, carried out in the framework of a French working group CEA-EDF-ENSMA, was divided into four phases: 1) scaling effects on the pressure field generated by spontaneous accelerations of deflagrations in a medium uniform composition, 2) the effect of a sudden discontinuity in the concentration of the combustible gas on the deflagration speed in a stratified medium, 3) the effect of the ignition energy on the explosion mode of a spherical ethylene-air mixture, and 4) the study of the influence of cloud shape and size on the pressure field generated by the explosion. No volume effects were observed for unconfined volumes ranging from 12 to 125 m . The low speeds of all previous large-scale open field and balloon tests were reconfirmed. Flame accelerations, and consequent peak overpressure increases, occur at the edge of the cloud as well as at the concentration discontinuities or gradients.
39th Aerospace Sciences Meeting and Exhibit, 2001
Shock Waves, Explosions, and Detonations, 1983
The present research contract, carried out in the framework of a French working group CEA-EDF-ENS... more The present research contract, carried out in the framework of a French working group CEA-EDF-ENSMA, was divided into four phases: 1) Phase 1 : Scaling effects on a pressure field generated by spontaneous accelerations of deflagrations in a homogeneous medium : these “CHARLES” tests performed on completely unconfined charges of ethylene-air and acetylene-air mixtures (V≃12 m3) have demonstrated the high sensitivity of the pressure field to the flame acceleration, particularly at the end of the propagation. 2) Phase 2 : Effect of a sudden discontinuity in the concentration of the combustible gas on the deflagration speed in a heterogeneous medium : this discontinuity was obtained using two concentric latex balloons, filled with different hydrocarbon concentrations and also destroyed before firing. 3) Phase 3 : Study of pseudo-detonation modes for the explosion of spherical ethylene-air mixtures : these modes were sought by increasing an explosive plastic mass associated to the ignite...
Fluid Mechanics and Its Applications, 1997
The influence of a turbulent injection of reactive mixture on oblique shock-induced combustions i... more The influence of a turbulent injection of reactive mixture on oblique shock-induced combustions is experimentally studied for Mach number M of 6 in stoichiometric H2-Air mixture initially at p0 = 0.4 bar and T0 = 293 K. For the same conditions (mixture, p0, T0), previous experiments in quiescent mixture have shown the establishing of different configurations of supersonic combustion stabilized by an oblique shock wave produced in the Lab oblique shock tube facility. In this facility, the lateral expansion of a normal CJ detonation in the driven section induced an oblique shock wave (OSW) into the H2-Air driven mixture. Depending on strength of OSW (i.e. inclination angle θ) two essential configurations of the stabilization of supersonic combustion were displayed : i) the decoupled oblique flame attached to OSW only at the edge of the wedge, ii) the oblique detonation observed inside the range of possible theoretical solutions. This detonation, generally overdriven, occurs after a delay (the detonation is detached from the edge). During this delay, the above mentionned configuration is observed. Based essentially on schlieren pictures provided by high speed camera, it has been demonstrated than turbulent injection : (i) does not affect significantly the minimum conditions for onset of oblique decoupled shock-flame configuration and the configuration itself, (ii) lowers the minimum condition for observing the oblique detonation configuration and shortens considerably the delay.
Http Www Theses Fr, 2001
Les travaux realises dans le cadre de cette etude ont eu pour objectif de quantifier les performa... more Les travaux realises dans le cadre de cette etude ont eu pour objectif de quantifier les performances propulsives d'un moteur a detonations pulsees (moteur a reaction a fonctionnement alternatif) et d'aborder sa configuration aerobie. L'etude des performances propulsives (impulsion specifique, poussee) a ete realisee avec le melange C2H4 O2, l'usage du melange H2 air etant restreint au demonstrateur aerobie. Dans un premier temps, une etude analytique et theorique basee sur des resultats anterieurs a permis d'etablir un modele de performances pour le cas ideal de la chambre de combustion cylindrique entierement remplie, fermee a l'une de ses extremite et ouverte a l'autre sur l'atmosphere a la pression ambiante pa, l'ecart a l'idealite a ete aborde en diminuant la pression de detonation devant la pression pa. Dans un deuxieme temps, plusieurs etudes experimentales (realisees sur banc monocycle) ont ete menees pour evaluer l'influence de i) la presence d'entrees d'air, ii) le remplissage partiel de la chambre iii) la presence de tuyeres, iv) la presence d'obstacles proche de la section d'ejection, sur les performances reelles accessibles par ce type de moteur. Pour ce faire, des methodes experimentales specifiques ont ete mises en œuvre et validees (mesure de la pression sur le mur de poussee, visualisation par strioscopie, mesure de l'impulsion par pendule balistique) pour l'obtention des deux parametres fondamentaux controlant les performances, l'impulsion specifique et le temps de cycle, ce dernier determinant le debit massique de melange reactif maximal possible ou la frequence maximale de fonctionnement. La realisation d'un banc d'essai multicycle "en conditions reelles" a enfin permis de valider des solutions techniques (necessite d'initier la detonation du melange principal H2 - air- a l'aide d'un systeme de pre-detonation utilisant un melange reactif tres detonant C2H4 O2-) et d'observer certains phenomenes specifiques du fonctionnement multicycle.
Http Www Theses Fr, 2003
Cette etude concerne la detonabilite des melanges reactifs gazeux, en particulier sous l'aspe... more Cette etude concerne la detonabilite des melanges reactifs gazeux, en particulier sous l'aspect du diametre critique de transmission de la detonation d'un tube au demi-espace libre. L'objectif etait d'ameliorer la transmission de la detonation en jouant sur la geometrie de la diffraction, notamment par l'adjonction d'un blocage central (de forme variable) dans la section terminale du tube. Les applications de ce travail sont liees a la securite des installations traitant de systemes reactifs mais aussi a la propulsion par detonation (moteur a detonations pulsees). L'etude experimentale de la diffraction de la detonation a montre que l'adjonction d'un obstacle central (rapport de blocage 50%) favorise systematiquement la transmission de la detonation. L'etude numerique (2D-axisymetrique) au moyen du code " EFAE " a permis de reproduire fidelement les mecanismes complexes instationnaires observes experimentalement. En consequence, ce code apparait comme un outil predictif des phenomenes de detonation.
Shock Waves, 2012
A parametric numerical study is performed of a detonation cellular structure in a model gaseous e... more A parametric numerical study is performed of a detonation cellular structure in a model gaseous explosive mixture whose decomposition occurs in two successive exothermic reaction steps with markedly different characteristic times. Kinetic and energetic parameters of both reactions are varied in a wide range in the case of onedimensional steady and two-dimensional (2D) quasi-steady self-supported detonations. The range of governing parameters of both exothermic steps is defined where a "marked" double cellular structure exists. It is shown that the two-level cellular structure is completely governed by the kinetic parameters and the local overdrive ratio of the detonation front propagating inside large cells. Furthermore, since it is quite cumbersome to use detailed chemical kinetics in unsteady 2D case, the proposed work should help to identify the mixtures and the domain of their equivalence ratio where double detonation structure could be observed.
Combustion Science and Technology, 2000
Abstract Flame propagation in a tube of constant cross section with ignition at the closed end an... more Abstract Flame propagation in a tube of constant cross section with ignition at the closed end and propagation toward the open end was studied experimentally, in propane-air, ethylene-air and acetylene-air mixtures. The flame trajectory displays an oscillatory behaviour which can be correlated to pressure records. The overall phenomenon is highly dependent on the mixture composition and the tube length.
Annales de Physique, 1989
Size and regularity of the cellular structure of detonations in C 2H2-O2-Ar systems were consider... more Size and regularity of the cellular structure of detonations in C 2H2-O2-Ar systems were considered. Experiments were conducted over a wide range of dilutions by argon and of degrees of overdrive of detonations. The increase of dilution by argon or of the degree of overdrive of the detonation reduces the value of the effective activation energy EA/RT of the system
Several studies have shown that the presence of obstacles can promote transition to detonation in... more Several studies have shown that the presence of obstacles can promote transition to detonation in a tube. For example, Thomas and co-workers (2002) carried out an experimental and numerical study concerning critical conditions for detonation initiation by shock reflection in a tube. They used a conventional shock tube with rectangular cross-section and produced the shock reflection by means of an obstacle giving a blockage ratio of 50%. They expressed a
Le Centre pour la Communication Scientifique Directe - HAL - Diderot, 2009
Le Centre pour la Communication Scientifique Directe - HAL - hprints.org, 2006
O. Bozier, R. Sorin, R. Zitoun and D. Desbordes (2009). “Detonability of Binary H2/CH4-Air Mixtures”, International Conference of Hydrogen Safety, ICHS 2009, Ajaccio 2009, Sep 17, 2009
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Papers by Daniel Desbordes