Étude numérique du transitoire d'injection adapté au fonctionnement d'un moteur fusée à détonation rotative

International 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

Dipole radio-frequency power from laser plasmas with no dipole moment

The radio-frequency power radiated from laser-target plasmas in a vacuum can be orders of magnitude greater than expected from such sources that have a negligible electric dipole moment. A model combining the Tidman-Stamper circuit model of a laser-target plasma with the theory of radiation from currents immersed in plasmas, however, predicts scaling of electric-dipole power radiated from laser plasmas in agreement with experiments.Comment: 3 pages, 2 figures, as published in Applied Physics Letter

On the origin of negative target currents during laser ablation of polyethylene

The exposure of a target to a focused laser beam results in the occurrence of a time-varying current between the target itself and the grounded vacuum chamber. This current is composed by three distinct phases, namely the ignition phase, in which the laser pulse drives the electron emission, while electrons coming from the ground through the target holder balance the positive charge generated on the target. The active phase appears at post-pulse times and it is characterized by the presence of peaked structures in the time-resolved current, representing characteristics of the target composition. Lastly, the afterglow phase is determined by a current of electrons flowing from the target to the ground. During the active phase of the target current resulting from polymers ablation with an UV KrF laser, negative target current peaks are observed, whose origin is still unknown. We investigate the dependence of these current structures on the dimensions of the target, using ultra-high molecular weight polyethylene disks of different thickness

ВАСИЛИЙ ИВАНОВИЧ БЕРНИК (К СЕМИДЕСЯТИЛЕТИЮ)

This work is devoted to the seventieth Doctor of Physical and Mathematical Sciences, Professor Vasily Ivanovich Bernik. In her curriculum vitae, a brief analysis of his scientific work and educational and organizational activities. The work included a list of 80 major scientific works of V.I. Bernik.Данная работа посвящена семидесятилетию доктора физико-математических наук, профессора Василия Ивановича Берника. В ней приводятся биографические данные, краткий анализ его научных работ и педагогической и организационной деятельности. В работу включён список из 80 основных научных работ В. И. Берника

Experimental Research on Transition Regions in Continuously Rotating Detonation Waves

Continuously rotating detonation waves of thousands of Hz, indicating the merit of continuously rotating detonation waves that ignite only once to keep working, are experimentally gotten in the combustion chamber designed by Peking University. The steady continuously rotating detonation waves have jarless peak pressures and cycles microcosmicly, showing that during this stage, flux, pressure and temperature of working medium are steady. However, transition regions do exist between two groups of steady continuously rotating detonation waves. Related data of transition regions are fitted to find out the basic rule. The paper also figures out the velocity of ideal detonation waves by C-J theory, and obtains the cycle and number of continuously rotating detonation waves with experimental data. ? 2012 by Yu-Hui Wang.EI