Bibliografie tematiche / Combustion-Deflagration-Detonation transition

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Letteratura scientifica selezionata sul tema "Combustion-Deflagration-Detonation transition"

Autore: Grafiati

Pubblicato: 5 aprile 2025

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Articoli di riviste sul tema "Combustion-Deflagration-Detonation transition"

Debnath, Pinku, e Krishna Murari Pandey. "Computational Study of Deflagration to Detonation Transition in Pulse Detonation Engine Using Shchelkin Spiral". Applied Mechanics and Materials 772 (luglio 2015): 136–40. http://dx.doi.org/10.4028/www.scientific.net/amm.772.136.

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Detonation combustion wave is much more energetic combustion process in pulse detonation engine combustion system. Numerous experimental, theoretical and numerical analyses have been studied in pulse detonation engine to implement in practical propulsion system. In this present computational study the simulation was carried out for deflagration flame acceleration and deflagration to detonation transition of hydrogen air combustible mixture inside the detonation tube with and without Shchelkin spiral. A three dimensional computational analysis has been done by finite volume discretization method using ANSYS Fluent 14 CFD commercial software. The LES turbulence model with second order upwind discretization scheme was adopted with standard boundary conditions for unsteady combustion wave simulations. From the computational study it was found that intensity of detonation wave velocity and dynamic pressure is higher near to the boundary of Shchelkin spiral in detonation tube. The contour plots comparisons clearly show that deflagration flame accelerates in detonation tube as present of Shchelkin spiral. The contour plots also suggest that deflagration flame velocity and pressure are less in without Shchelkin spiral in detonation tube. The accelerating detonation waves are approximately near about Chapment-Jouguet values in detonation tube with Shchelkin spiral.

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Ma, Hu, Zhenjuan Xia, Wei Gao, Changfei Zhuo e Dong Wang. "Numerical simulation of the deflagration-to-detonation transition of iso-octane vapor in an obstacle-filled tube". International Journal of Spray and Combustion Dynamics 10, n. 3 (13 febbraio 2018): 244–59. http://dx.doi.org/10.1177/1756827718758047.

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Flame acceleration and deflagration-to-detonation transition of an iso-octane vapor–air mixture in an obstacle-filled detonation tube were simulated by solving Navier–Stokes equations with a single-step reaction mechanism. A variable specific heat ratio was used in these simulations. Detonation cell size was successfully simulated for the iso-octane vapor–air mixture. Two methods for initiating detonation waves were revealed in a detonation tube with obstacles. Pressure and flame parameters, such as the temporal variation of total energy release rate, flame front location, propagation velocity of the flame front, and flame front area, were investigated during the flame acceleration and deflagration-to-detonation transition process. According to the variation of these parameters, flame acceleration and deflagration-to-detonation transition processes could be divided into four stages, i.e. the early stage of flame acceleration, the middle stage of flame acceleration, the end stage of flame acceleration, and the detonation transition stage. The effects of activation energy and pre-exponential factor on deflagration-to-detonation transition processes were examined. The results indicate that the pre-exponential factor and activation energy influence the flame parameters, but not the development law of flame acceleration or deflagration-to-detonation transition processes. For lower reactants activity, detonation wave is easy to fail in couple while bypassing obstacles in the obstacle-filled detonation tube, which causes a large fluctuation in flame propagation velocity and total energy release rate. The length of detonation tube filled by obstacles should not be more than deflagration-to-detonation transition distance. These investigations are conducive to understanding the flame acceleration and deflagration-to-detonation transition and developing detonation combustion chamber of pulse detonation engine.

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Davis, Scott, Derek Engel, Kees van Wingerden e Erik Merilo. "Can gases behave like explosives: Large-scale deflagration to detonation testing". Journal of Fire Sciences 35, n. 5 (settembre 2017): 434–54. http://dx.doi.org/10.1177/0734904117715648.

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A large vapor cloud explosion followed by a fire is one of the most dangerous and high consequence events that can occur at petrochemical facilities. However, one of the most devastating explosions is when a deflagration transitions to a detonation, which can travel at speeds greater than 1800 m/s and pressures greater than 18 barg. This phenomenon is called a deflagration-to-detonation transition, whereby the deflagration (flame front) continues to accelerate due to confinement or flow-induced turbulence (e.g. obstacles) and ultimately transitions at flame speeds greater than the speed of sound to a detonation. Unlike a deflagration that requires the presence of confinement or obstacles to generate high flame speeds and associated elevated overpressures, a detonation is a self-sustaining phenomenon having the shock front coupled to the combustion. Once established, the resulting detonation will continue to propagate through the vapor cloud at speeds (1800 m/s) that are of similar order as high explosives (7000–8000 m/s). While there are differences between high explosives and vapor cloud explosions (e.g. high explosives can have pressures well in excess of 100 bar), vapor cloud explosions that transition to detonations can cause significant damage due to the extremely high pressures not typically associated with gas phase explosions (>18 barg), high energy release rate per unit mass, and higher impulses due to large cloud sizes. While the likelihood of deflagration-to-detonation transitions is lower than deflagrations, they have been identified in some of the most recent large-scale explosion incidents. The consequences of deflagration-to-detonation transitions can be orders of magnitude larger than deflagrations. This article will present the results of large-scale testing conducted in a newly developed test rig of 1500 m3 gross volume involving stoichiometric, lean, and rich mixtures of propane and methane.

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Qiu, Hua, Zheng Su e Cha Xiong. "Experimental investigation on multi-cycle two-phase spiral pulse detonation tube of two configurations". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, n. 11 (4 dicembre 2018): 4166–75. http://dx.doi.org/10.1177/0954410018817455.

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The spiral tube structure is an effective method to shorten the axial length of the pulse detonation chamber. In this article, spiral pulsed detonation tube with two kinds of spiral configuration was experimentally investigated. Liquid gasoline and air were used as fuel and oxidant, respectively, and equivalence ratios were controlled to about 1.0. Based on the transient pressure along the tube, the propagation characteristics of the pressure waves in the multi-cycle spiral pulsed detonation tubes, such as pressure peaks, wave velocities and propagation process, were analyzed. Results showed that propagation of double compression waves was the common feature during the process of deflagration to detonation transition in the presented spiral tubes, and the onset of detonation was initiated by a local explosion in the second compression wave. The deflagration to detonation transition characteristics with detonation initiation and combustion characteristics without initiation in the spiral sections were both related to the dimensionless distance. Propagation characteristics of the pressure waves were influenced by the use of different spiral configuration. And some interesting phenomena were also found.

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Smirnov, Nickolay, e Valeriy Nikitin. "Three-dimensional simulation of combustion, detonation and deflagration to detonation transition processes". MATEC Web of Conferences 209 (2018): 00003. http://dx.doi.org/10.1051/matecconf/201820900003.

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The paper presents results of numerical and experimental investigation of mixture ignition and detonation onset in shock wave reflected from inside a wedge. Contrary to existing opinion of shock wave focusing being the mechanism for detonation onset in reflection from a wedge or cone, it was demonstrated that along with the main scenario there exists a transient one, under which focusing causes ignition and successive flame acceleration bringing to detonation onset far behind the reflected shock wave. Several different flow scenarios manifest in reflection of shock waves all being dependent on incident shock wave intensity: reflecting of shock wave with lagging behind combustion zone, formation of detonation wave in reflection and focusing, and intermediate transient regimes. Comparison of numerical and experimental results made it possible to validate the developed 3-D transient mathematical model of chemically reacting gas mixture flows incorporating hydrogen – air mixtures.

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Adoghe, Joseph, Weiming Liu, Jonathan Francis e Akinola Adeniyi. "Investigation into mechanisms of deflagration-to-detonation using Direct Numerical Simulations". E3S Web of Conferences 128 (2019): 03002. http://dx.doi.org/10.1051/e3sconf/201912803002.

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Detonation, a combustion phenomenon is a supersonic combustion wave which plays critical role in the theory and application of combustion. This work presents numerical investigation into indirect initiation of detonation using direct numerical simulations (DNS). The Adaptive Mesh Refinement in object–oriented C++ (AMROC) tool for parallel computations is applied in DNS. The combustion reactions take place in a shock tube and an enclosure with a tube respectively and are controlled by detailed chemical kinetics. The database produced by DNS accurately simulates the process of transition of deflagration to detonation (DDT), and investigates the influence of overpressure and kinetics on flame propagations during combustion processes. The numerical simulations showed the influence of pressure and kinetics to the transition of slow and fast flames and DDT during flame propagations. When the reaction rate is fast, DDT is achieved, but when slow, DDT will not occur and therefore, there will be no detonation and consequently no strong explosion. Exploring the influence of free radical H on flame propagation showed that the concentration of the reacting species decreased with flame speed increase for each propagation. Hence, the heat generated was very fast with a greater chance of DDT beingtriggered because flame speed increased.

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Cojocea, Andrei Vlad, Ionuț Porumbel, Mihnea Gall e Tudor Cuciuc. "Experimental Investigations on the Impact of Hydrogen Injection Apertures in Pulsed Detonation Combustor". Energies 17, n. 19 (1 ottobre 2024): 4918. http://dx.doi.org/10.3390/en17194918.

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Combustion through detonation marks an important leap in efficiency over standard deflagration methods. This research introduces a Pulsed Detonation Combustor (PDC) model that uses Hydrogen as fuel and Oxygen as an oxidizer, specifically targeting carbon-free combustion efforts. The PDC aerodynamic features boost operating cycle frequency and facilitate Deflagration-to-Detonation Transition (DDT) within distances less than 200 mm by means of Hartmann–Sprenger resonators and cross-flow fuel/oxidizer injection. The achievement of quality mixing in a short-time filling process represents not only higher cycle operation but also enhanced performances. The scope of this paper is to assess the impact of different fuel injectors with different opening areas on the performances of the PDC. This assessment, expressed as a function of the Equivalence Ratio (ER), is conducted using two primary methods. Instantaneous static pressures are recorded and processed to extract the maximum and average cycle pressure and characterize the pressure augmentation. Thrust measurements obtained using a load cell are averaged over the detonation cycle to calculate the time-averaged thrust. The specific impulse is subsequently determined based on these thrust measurements and the corresponding mass flow data.

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Huang, Xiaolong, Ning Li e Yang Kang. "Research on Optical Diagnostic Method of PDE Working Status Based on Visible and Near-Infrared Radiation Characteristics". Energies 14, n. 18 (10 settembre 2021): 5703. http://dx.doi.org/10.3390/en14185703.

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Fill fraction not only has a profound impact on the process of deflagration to detonation in pulsed detonation engine, but also affects the propulsion performance in both flight and ground tests. In this paper, a novel optical diagnostic method based on detonation exhaust radiation in visible and near-infrared region within 300–2600 nm is developed to determine the current working state in the gas–liquid two-phase pulsed detonation cycle. The results show that the radiation characteristic in each stage of detonation cycle is unique and can be a good indicator to infer the fill fraction. This is verified experimentally by comparison with the laser absorption spectroscopy method, which utilizes a DFB laser driven by ramp injection current to scan H2O transition of 1391.67 nm at a frequency of 20 kHz. Due to concentrated radiation intensity, time duration reaching accumulated radiant energy ratio of 50% in detonation status would be smaller than 1.2 ms, and detonation status would be easily distinguished from deflagration with this critical condition. In addition, the variation of important intermediates OH, CH, and C2 radicals during detonation combustion are obtained according to the analysis of detonation spectrum, which can also be proposed as a helpful optical diagnostics method for the combustion condition based on C radical concentration. The study demonstrates the feasibility of optical diagnostics based on radiation in visible and near-infrared regions, which could provide an alternative means to diagnose and improve pulsed detonation engine performance.

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Frolov, Sergey M., Igor O. Shamshin, Viktor S. Aksenov, Vladislav S. Ivanov e Pavel A. Vlasov. "Ion Sensors for Pulsed and Continuous Detonation Combustors". Chemosensors 11, n. 1 (1 gennaio 2023): 33. http://dx.doi.org/10.3390/chemosensors11010033.

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Presented in the article are the design and operation principles of ion sensors intended for detecting the propagating reaction fronts, the deflagration/detonation mode, apparent subsonic/supersonic propagation velocity of the reaction front, and duration of heat release by measuring the ion current in the reactive medium. The electrical circuits for ion sensors without and with intermediate amplifiers, with short response time and high sensitivity, as well as with the very wide dynamic range of operation in the reactive media with highly variable temperature and pressure, are provided and discussed. The main advantages of ion sensors are their very short response time of about 1 ms, versatility of design, and capability of detecting and monitoring reaction fronts of different intensities directly in combustion chambers. Several examples of ion sensor applications in sensing deflagration-to-detonation transition in pulsed detonation engines and developed detonations in rotating detonation engines operating on different fuel–air and fuel–oxygen mixtures are presented and discussed.

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Brailovsky, I., L. Kagan e G. Sivashinsky. "Combustion waves in hydraulically resisted systems". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, n. 1960 (13 febbraio 2012): 625–46. http://dx.doi.org/10.1098/rsta.2011.0341.

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The effects of hydraulic resistance on the burning of confined/obstacle-laden gaseous and gas-permeable solid explosives are discussed on the basis of recent research. Hydraulic resistance is found to induce a new powerful mechanism for the reaction spread (diffusion of pressure) allowing for both fast subsonic as well as supersonic propagation. Hydraulic resistance appears to be of relevance also for the multiplicity of detonation regimes as well as for the transitions from slow conductive to fast convective, choked or detonative burning. A quasi-one-dimensional Fanno-type model for premixed gas combustion in an obstructed channel open at the ignition end is discussed. It is shown that, similar to the closed-end case studied earlier, the hydraulic resistance causes a gradual precompression and preheating of the unburned gas adjacent to the advancing deflagration, which leads (after an extended induction period) to a localized autoignition that triggers an abrupt transition from deflagrative to detonative combustion. In line with the experimental observations, the ignition at the open end greatly encumbers the transition (compared with the closed-end case), and the deflagration practically does not accelerate up to the very transition point. Shchelkin's effect, that ignition at a small distance from the closed end of a tube facilitates the transition, is described.

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Più fonti

Tesi sul tema "Combustion-Deflagration-Detonation transition"

Chapin, David Michael. "A Study of Deflagration To Detonation Transition In a Pulsed Detonation Engine". Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7526.

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A Pulse Detonation Engine (PDE) is a propulsion device that takes advantage of the pressure rise inherent to the efficient burning of fuel-air mixtures via detonations. Detonation initiation is a critical process that occurs in the cycle of a PDE. A practical method of detonation initiation is Deflagration-to-Detonation Transition (DDT), which describes the transition of a subsonic deflagration, created using low initiation energies, to a supersonic detonation. This thesis presents the effects of obstacle spacing, blockage ratio, DDT section length, and airflow on DDT behavior in hydrogen-air and ethylene-air mixtures for a repeating PDE. These experiments were performed on a 2 diameter, 40 long, continuous-flow PDE located at the General Electric Global Research Center in Niskayuna, New York. A fundamental study of experiments performed on a modular orifice plate DDT geometry revealed that all three factors tested (obstacle blockage ratio, length of DDT section, and spacing between obstacles) have a statistically significant effect on flame acceleration. All of the interactions between the factors, except for the interaction of the blockage ratio with the spacing between obstacles, were also significant. To better capture the non-linearity of the DDT process, further studies were performed using a clear detonation chamber and a high-speed digital camera to track the flame chemiluminescence as it progressed through the PDE. Results show that the presence of excess obstacles, past what is minimally required to transition the flame to detonation, hinders the length and time to transition to detonation. Other key findings show that increasing the mass flow-rate of air through the PDE significantly reduces the run-up time of DDT, while having minimal effect on run-up distance. These experimental results provided validation runs for computational studies. In some cases as little as 20% difference was seen. The minimum DDT length for 0.15 lb/s hydrogen-air studies was 8 L/D from the spark location, while for ethylene it was 16 L/D. It was also observed that increasing the airflow rate through the tube from 0.1 to 0.3 lbs/sec decreased the time required for DDT by 26%, from 3.9 ms to 2.9 ms.

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Hamon, Émilien. "Endommagement, fragmentation et combustion d’un matériau explosif comprimé". Electronic Thesis or Diss., Bourges, INSA Centre Val de Loire, 2025. http://www.theses.fr/2025ISAB0003.

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Dans le cadre de la sécurité des structures pyrotechniques, il est important de prédire le niveau de réaction atteint lors d’agressions thermiques ou mécaniques (impact). À ce jour, il n’existe pas de démarche unifiée et approuvée par la communauté scientifique internationale permettant de décrire le processus complexe menant à des réactions violentes telles que la transition Combustion-Déflagration-Détonation (TCoDD). Cette thèse a pour objectif d’étudier l’influence de l’endommagement dû à un impact à basse vitesse sur la combustion d’un explosif comprimé.Dans un premier temps, nous étudierons l’influence d’une sollicitation mécanique sur le comportement en combustion de notre matériau. Nous montrerons que la surface en combustion joue un rôle important dans le phénomène de la TCoDD, et nous chercherons à déterminer cette surface à partir des essais en bombe manométrique. Ensuite, nous nous attacherons à quantifier l’endommagement au sein de la microstructure (densité de fissures, porosité, etc.) suite à une sollicitation mécanique. Enfin, nous modéliserons le comportement mécanique de notre matériau et relierons l’endommagement de celui-ci à la densité de fissures ayant une influence sur la combustion du matériau
In the context of the safety of pyrotechnic structures, it is important to evaluate by simulation the level of reaction reached during thermal or mechanical aggressions (impact). Nowadays, there is no unified approach approved by the international scientific community to describe the complex process leading to violent reactions such as the Combustion-Deflagration-Detonation transition (CoDDT). The objective of this thesis is to study the influence of the damage, resulting from low velocity impact damage on the combustion of a pressed explosive.First, we will study the influence of mechanical loading on the combustion behavior of our material. We will show that the burning surface plays an important role in the TCoDD phenomenon, and we will seek to determine this surface from manometer bomb tests. Next, we will quantify the damage within the microstructure (crack density, porosity, etc.) following mechanical loading. Finally, we will model the mechanical behavior of our material and relate its damage to the crack density influencing material combustion

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Charignon, Camille. "Transition Déflagration-Détonation dans les Supernovae Thermonucléaires". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00874701.

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Les supernovæ de type Ia (SNe Ia) sont devenues un outil important pour retracer l'expansion de notre Univers, leur étude est donc importante pour la cosmologie. Le modèle le plus populaire est celui de l'explosion d'une naine blanche (NB) accrétante dont la contraction relance la combustion sous la forme d'une déflagration subsonique, qui transiterait ensuite en une détonation supersonique. Ce scénario de détonation retardée repose sur un mécanisme physique de Transition Déflagration-Détonation (TDD) encore très mal compris, que nous étudions dans cette thèse.Les modèles actuels de détonation retardée reproduisent les observations en se fondant sur le mécanisme des gradients de Zel'dovich. Cependant, les échelles d'ignition n'étant pas résolues, ces simulations n'expliquent pas à elles seules la TDD, phénomène mal compris, même sur Terre, lorsqu'il s'agit de milieux non-confinés. D'autre part, ce mécanisme requiert une turbulence trop intense et impose des conditions probablement trop restrictives.C'est dans ce contexte que nous avons proposé un nouveau mécanisme de TDD: le chauffage acoustique de l'enveloppe du progéniteur. Un modèle simplifié, en géométrie plane, permet de mettre en évidence l'amplification d'ondes acoustiques (générés par une flamme turbulente) dans un gradient de densité similaire à ceux d'une NB. Selon leur fréquence et leur amplitude, leur amplification peut aller jusqu'à la formation d'un choc suffisamment fort pour initier une détonation. Ensuite, ce mécanisme est analysé en géométrie sphérique dans le cadre plus réaliste d'une NB en expansion. Une étude paramétrique montre la validité de notre mécanisme sur une gamme raisonnable de fréquences et d'amplitudes acoustiques.Finalement, quelques simulations MHD 2D et 3D, où l'on recherche une source de perturbations acoustiques, sont présentées pour démontrer le caractère réaliste de notre nouveau mécanisme de TDD.

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Kristoffersen, Kjetil. "Gas explosions in process pipes". Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-235.

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In this thesis, gas explosions inside pipes are considered. Laboratory experiments and numerical simulations are the basis of the thesis. The target of the work was to develop numerical models that could predict accidental gas explosions inside pipes.

Experiments were performed in circular steel pipes, with an inner diameter of 22.3 mm, and a plexiglass pipe, with an inner diameter of 40 mm. Propane, acetylene and hydrogen at various equivalence ratios in air were used. Pressure was recorded by Kistler pressure transducers and flame propagation was captured by photodiodes, a SLR camera and a high-speed camera. The experiments showed that acoustic oscillations would occur in the pipes, and that the frequencies of these oscillations are determined by the pipe length. Several inversions of the flame front can occur during the flame propagation in a pipe. These inversions are appearing due to quenching of the flame front at the pipe wall and due to interactions of the flame front with the longitudinal pressure waves in the pipe. Transition to detonation was achieved in acetylene-air mixtures in a 5 m steel pipe with 4 small obstructions.

Simulations of the flame propagation in smooth pipes were performed with an 1D MATLAB version of the Random Choice Method (RCMLAB). Methods for estimation of quasi 1D burning velocities and of pipe outlet conditions from experimental pressure data were implemented into this code. The simulated pressure waves and flame propagation were compared to the experimental results and there are good agreements between the results.

Simulations were also performed with the commercial CFD code FLACS. They indicated that to properly handle the longitudinal pressure oscillations in pipes, at least 7 grid cells in each direction of the pipe cross-section and a Courant number of maximum 1 should be used. It was shown that the current combustion model in FLACS gave too high flame speeds initially for gas explosions in a pipe with an inner width of 40 mm.

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Gray, Joshua Allen Terry [Verfasser], Christian Oliver [Akademischer Betreuer] Paschereit, Jonas Pablo [Akademischer Betreuer] Moeck, Christian Oliver [Gutachter] Paschereit, Jonas Pablo [Gutachter] Moeck e Ephraim [Gutachter] Gutmark. "Reduction in the run-up distance for the deflagration-to-detonation transition and applications to pulse detonation combustion / Joshua Allen Terry Gray ; Gutachter: Christian Oliver Paschereit, Jonas Pablo Moeck, Ephraim Gutmark ; Christian Oliver Paschereit, Jonas Pablo Moeck". Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1156180090/34.

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Schild, Ilissa Brooke. "Influence of Spark Energy, Spark Number, and Flow Velocity on Detonation Initiation in a Hydrocarbon-fueled PDE". Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7527.

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Pulsed Detonation Engines (PDEs) have the potential to revolutionize fight by better utilizing the chemical energy content of reactive fuel/air mixtures over conventional combustion processes. Combustion by a super-sonic detonation wave results in a significant increase in pressure in addition to an increase in temperature. In order to harness this pressure increase and achieve a high power density, it is desirable to operate PDEs at high frequency. The process of detonation initiation impacts operating frequency by dictating the length of the chamber and contributing to the overall cycle time. Therefore a key challenge in the development of a practical PDEs is the requirement to rapidly initiate a detonation in hydrocarbon-air mixtures. This thesis evaluates the influence of spark energy and airflow velocity on this challenging initiation process. The influence of spark energy, number of sparks and airflow velocity on Deflagration-to-Detonation Transition (DDT) was studied during cyclic operation of a small-scale PDE at the General Electric Global Research Center. Experiments were conducted in a 50 mm square transitioning to cylindrical channel PDE with optical access operating with stoichiometric ethylene-air mixture. Total spark energy was varied from 250 mJ to 4 J and was distributed between one and four spark plugs located in the same axial location. Initial flame acceleration was imaged using high-speed shadowgraph and was characterized by the time to reach 20 cm from the spark plug. Measurements of detonation wave velocity and emergence time, the time it takes the detonation wave to exit the tube, was measured using dynamic pressure transducers and ionization probes. It was found that the flame front spread was faster at higher spark energies and with more spark locations. Initial flame acceleration was 16% faster for the 4-spark, 4 J case when compared to the baseline 1-spark, 1 J case. When looking at the effect of airflow on the influence of spark energy, it was found that airflow had a larger effect on emergence time at high energies, versus energies less than 1 J. Finally, for a selected case of 0.25 J spark energy and 4 sparks, the velocity of the fuel-air mixture during fill was found to have a varying influence on detonation initiation and emergence time.

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Nicoloso, Julien. "Combustion confinée d'explosif condensé pour l'accélaration de projectile. Application en pyrotechnie spatiale". Phd thesis, ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2014. http://tel.archives-ouvertes.fr/tel-01060036.

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L'opto-pyrotechnie (amorçage de la détonation par système optique) est l'une des innovations les plus prometteuses en termes de fiabilité, de sécurité et de performances pour les futurs lanceurs spatiaux. Le but de la thèse est d'étudier et de modéliser le premier des deux étages d'un Détonateur Opto-Pyrotechnique, constitué d'un explosif confiné dans une chambre de combustion fermée où se déroulent les premières phases d'une Transition Déflagration-Détonation. L'amorçage par laser de l'explosif puis la combustion en chambre isochore sont traités par le code EFAE, lequel est couplé au logiciel LS-DYNA qui simule la déformation et la rupture du disque de fermeture de la chambre, puis la propulsion du projectile résultant vers le second étage. En parallèle, diverses techniques expérimentales (adsorption de gaz, vélocimétrie hétérodyne, microscopie) ont mis en valeur plusieurs procédés physiques, ce qui a permis de tester le couplage entre EFAE et LS-DYNA, puis de déterminer et de hiérarchiser les paramètres affectant les critères industriels.

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Lindstedt, R. Peter. "Deflagration to detonation transition in mixtures containing LNG/LPG constituents". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37764.

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Myers, Charles B. "Initiation mechanisms of low-loss swept-ramp obstacles for deflagration to detonation transition in pulse detonation combustors". Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FMyers.pdf.

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Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2009.
Thesis Advisor(s): Brophy, Christopher M. Second Reader: Hobson, Garth V. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Pulse Detonation Combustors, PDC, Pulse Detonation Engines, PDE, PDE ignition, PDE initiation, low-loss obstacles, ramp, swept ramp, DDT, DDT initiation. Includes bibliographical references (p. 89-90). Also available in print.

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Bhat, Abhishek R. "Experimental and Computational Studies on Deflagration-to-Detonation Transition and its Effect on the Performance of PDE". Thesis, 2014. http://etd.iisc.ac.in/handle/2005/3181.

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This thesis is concerned with experimental and computational studies on pulse detonation engine (PDE) that has been envisioned as a new concept engine. These engines use the high pressure generated by detonation wave for propulsion. The cycle efficiency of PDE is either higher in comparison to conventional jet engines or at least has similar high performance with much greater simplicity in terms of components. The first part of the work consists of an experimental study of the performance of PDE under choked flame and partial fill conditions. Detonations used in classical PDEs create conditions of Mach numbers of 4-6 and choked flames create conditions in which flame achieves Mach numbers near-half of detonation wave. While classical concepts on PDE's utilize deflagration-to-detonation transition and are more intensively studied, the working of PDE under choked regime has received inadequate attention in the literature and much remains to be explored. Most of the earlier studies claim transition to detonation as success in the working of the PDE and non-transition as failure. After exploring both these regimes, the current work brings out that impulse obtained from the wave traveling near the choked flame velocity conditions is comparable to detonation regime. This is consistent with the understanding from the literature that CJ detonation may not be the optimum condition for maximum specific impulse. The present study examines the details of working of PDE close to the choked regime for different experimental conditions, in comparison with other aspects of PDEs. The study also examines transmission of fast flames from small diameter pipe into larger ducts. This approach in the smaller pipe for flame acceleration also leading to decrease in the time and length of transition process. The second part of the study aims at elucidating the features of deflagration-to-detonation transition with direct numerical simulation (DNS) accounting for and the choice of full chemistry and DNS is based on two features: (a) the induction time estimation at the conditions of varying high pressure and temperature behind the shock can only be obtained through the use of full chemistry, and (b) the complex effects of fine scale of turbulence that have sometimes been argued to influence the acceleration phase in the DDT cannot be captured otherwise. Turbulence in the early stages causes flame wrinkling and helps flame acceleration process. The study of flame propagation showed that the wrinkling of flame has major effect on the final transition phase as flame accelerates through the channel. Further, flame becomes corrugated prior to transition. This feature was investigated using non-uniform initial conditions. Under these conditions the pressure waves emanating from corrugated flame interact with the shock moving ahead and transition occurs in between the flame and the forward propagating shock wave. The primary contributions of this thesis are: (a) Elucidating the phenomenology of choked flames, demonstrating that under partial fill conditions, the specific impulse can be superior to detonations and hence, allowing for the possibility of choked flames as a more appropriate choice for propulsive purposes instead of full detonations, (b) The use of smaller tube to enhance the flame acceleration and transition to detonation. The comparison with earlier experiments clearly shows the enhancements achieved using this method, and (c) The importance of the interaction between pressure waves emanating from the flame front with the shock wave which leads to formation of hot spots finally transitioning to detonation wave.

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Capitoli di libri sul tema "Combustion-Deflagration-Detonation transition"

Liberman, Michael A. "Flame Acceleration and Deflagration-To-Detonation Transition". In Combustion Physics, 415–63. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-85139-2_15.

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"Transient Combustion of Solid Propellants: An Important Aspect of Deflagration-to-Detonation Transition". In Nonsteady Burning and Combustion Stability of Solid Propellants, 441–64. Washington DC: American Institute of Aeronautics and Astronautics, 1992. http://dx.doi.org/10.2514/5.9781600866159.0441.0464.

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"Deflagration-to-Detonation Transition in Reactive Granular Materials". In Numerical Approaches to Combustion Modeling, 481–512. Washington DC: American Institute of Aeronautics and Astronautics, 1991. http://dx.doi.org/10.2514/5.9781600866081.0481.0512.

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Smirnov, N. N., V. F. Nikitin, V. M. Shevtsova e J. C. Legros. "THE ROLE OF GEOMETRICAL FACTORS IN DEFLAGRATION-TO-DETONATION TRANSITION". In Combustion Processes in Propulsion, 305–14. Elsevier, 2006. http://dx.doi.org/10.1016/b978-012369394-5/50032-9.

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Atti di convegni sul tema "Combustion-Deflagration-Detonation transition"

Zangiev, A. E., V. S. Ivanov e S. M. Frolov. "NUMERICAL SIMULATION OF DEFLAGRATION-TO-DETONATION TRANSITION IN A PULSED DETONATION ENGINE". In 8TH INTERNATIONAL SYMPOSIUM ON NONEQUILIBRIUM PROCESSES, PLASMA, COMBUSTION, AND ATMOSPHERIC PHENOMENA. TORUS PRESS, 2020. http://dx.doi.org/10.30826/nepcap2018-2-31.

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The air-breathing pulsed detonation engine (PDE) for an aircraft designed for a subsonic flight when operating on the products of pyrolysis of polypropylene was developed using the analytical estimates and parametric multivariant threedimensional (3D) calculations. The PDE consists of an air intake with a check valve, a fuel supply system, a prechamber-jet ignition system, and a combustion chamber with an attached detonation tube. Parametric 3D calculations allowed choosing the best length of the PDE combustor, which provides an efficient mixing of air with fuel, the best way to ignite the mixture (prechamber-jet ignition), the best location of the prechamber, the minimum length of the section with turbulizing obstacles for flame acceleration and deflagration-to-detonation transition (DDT), and the best degree of filling the detonation tube with the fuel mixture to achieve the maximum completeness of combustion.

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Hwang, Eduardo, Felipe Porto Ribeiro e Jian Su. "CFD Simulation of Deflagration to Detonation Transition for Nuclear Safety". In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-31010.

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The present work aims to develop an efficient methodology for evaluating the Deflagration to Detonation Transition (DDT) in accidental scenarios from inherent hydrogen risk in water-cooled NPPs (Nuclear Power Plants). The physical problem is flame acceleration through a confined geometry congested with periodic obstacles, up to formation of a travelling shock wave. The problem was modeled by the Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-ε turbulence model. There are two main combustion models: EDC (Eddy Dissipation Concept) whose equations are the transport equations for chemical species involved; and BVM (Burning Velocity Model) a transport equation for reaction progress (one scalar), to be used with three available turbulent flame speed correlations (Peters, Mueller and Zimont), and a new formulation based on Piston Action of the expanding burnt gas. The present work compared characteristics of these combustion models regarding flame acceleration in the midsize mc043 experiment, in order to apply the proposed combustion model in large scale DDT simulations. Experiment mc043 is consists of igniting a 12-meter long tube with 70 annular obstacles, filled with lean hydrogen-air mixture. The numerical results revealed that the proposed model is superior to BVM model correlations in predicting shock wave formation, and may provide a computationally more efficient option to the EDC model.

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FROLOV, S. M., V. S. AKSENOV e I. O. SHAMSHIN. "DEFLAGRATION-TO-DETONATION TRANSITION IN A STRATIFIED SYSTEM “GASEOUS OXYGEN-LIQUID FILM OF N-DECANE”". In 8TH INTERNATIONAL SYMPOSIUM ON NONEQUILIBRIUM PROCESSES, PLASMA, COMBUSTION, AND ATMOSPHERIC PHENOMENA. TORUS PRESS, 2020. http://dx.doi.org/10.30826/nepcap2018-2-30.

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Deflagration-to-detonation transition (DDT) in the system “gaseous oxygen- liquid film of n-decane” ' with a weak ignition source was obtained experimentally. In a series of experiments with ignition by an exploding wire that generates a weak primary shock wave (SW) with a Mach number ranging from 1.03 to 1.4, the DDT with the detonation run-up distances 1 to 4 m from the ignition source and run-up time 3 ms to 1.7 s after ignition was observed in a straight smooth channel of rectangular 54 x 24-millimeter cross section, 3 and 6 m in length with one open end. The DDT is obtained for relatively thick films with a thickness of 0. 3-0.5 mm, which corresponds to very high values of the overall fuel-to-oxygen equivalence ratios of 20-40. The registered velocity of the detonation wave (DW) was 1400-1700 m/s. In a number of experiments, a high-velocity quasi-stationary detonation-like combustion front was recorded running at an average velocity of 700-1100 m/s. Its structure includes the leading SW followed by the reaction zone with a time delay of 90 to 190 s. The obtained results are important for the organization of the operation process in advanced continuous-detonation and pulsed-detonation combustors of rocket and air-breathing engines with the supply of liquid fuel in the form of a wall film.

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Ren, Ke, Alexei Kotchourko, Alexander Lelyakin e Thomas Jordan. "Numerical Reproduction of DDT in Small Scale Channels". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67150.

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Deflagration to detonation transition (DDT) is a quite challenging subject in computational fluid dynamics both from a standpoint of the phenomenon nature understanding and from extremely demanding computational efforts. In the article the hybrid DDT combustion model is introduced as an efficient method to simulate the DDT problems. As verification, two DDT experiments made in experimental facility MINI RUT are used.

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FROLOV, S. M., V. I. ZVEGINTSEV, V. S. AKSENOV, I. V. BILERA, M. V. KAZACHENKO, I. O. SHAMSHIN, P. A. GUSEV e M. S. BELOTSERKOVSKAYA 3,8. "RANKING OF FUEL–AIR MIXTURES IN TERMS OF THEIR PROPENSITY TO DEFLAGRATION-TO-DETONATION TRANSITION". In International Colloquium on Pulsed and Continuous Detonations. TORUS PRESS, 2021. http://dx.doi.org/10.30826/icpcd12b02.

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A new experimental method for evaluating the detonability of fuel–air mixtures (FAMs) based on measuring the deflagration-to-detonation transition (DDT) run-up distance and/or time in a standard pulse detonation tube (SDT) is used to rank gaseous premixed and nonpremixed FAMs by their detonability under substantially identical thermodynamic and gasdynamic conditions. In the experiments, FAMs based on hydrogen, acetylene, ethylene, propylene, propane–butane, n-pentane, and natural gas (NG) of various compositions as well as FAMs based on the gaseous pyrolysis products of polyethylene (PE) and polypropylene (PP) are used: from extremely fuel-lean to extremely fuel-rich at normal temperatures and pressures. The concept of ''equivalent'' FAMs exhibiting the same or similar detonability under the same conditions is proposed. ''Equivalent'' FAMs can be used for predictive physical modeling of detonation processes involving FAMs of other fuels. The ranking of FAMs in terms of their relative detonability allows choosing a propylene FAM for physical modeling of the operation process in the PP-fueled solid-fuel ramjets operating on detonative combustion.

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Hasti, Veeraraghava Raju, e Reetesh Ranjan. "Numerical Investigation of Wave Dynamics During Mode Transition in a Hydrogen-Fueled Rotating Detonation Engine Combustor". In ASME 2024 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2024. https://doi.org/10.1115/imece2024-145858.

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Abstract We present results from the numerical investigation of mode transition with associated wave dynamics in a practical rotating detonation engine (RDE) combustor. The computational setup follows a past experimental study of an RDE combustor, which utilizes hydrogen as the fuel and air as the oxidizer. We consider a configuration at the global equivalence ratio, ϕ = 1, which exhibits the presence of a single detonation front propagating in a cyclic manner in the annular combustion chamber. After establishing the single wave mode, we alter the mass flow rates of fuel and oxidizer ensuring the same value of ϕ. The simulation was able to capture the wave mode transition from a sustained single detonation wave structure to a double co-rotating detonation wave structure in good agreement with experiments. The transition occurs due to inhomogeneities of fuel/air mixing and a nonlinear interaction of thermo-chemical variables with the propagating waves in the chamber. We analyzed the behavior of pressure, heat-release rate, and other thermo-chemical quantities during the wave mode transition, which shows the effects of fuel/air mixing leading to the presence of deflagration mode of burning apart from the cyclic propagation of the detonation fronts.

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Schildberg, Hans-Peter. "Experimental Determination of the Static Equivalent Pressures of Detonative Decompositions of Acetylene in Long Pipes and Chapman-Jouguet Pressure Ratio". In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28197.

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Gaseous acetylene (C2H2), which is used in industry in large quantities, is well known for being prone to detonative decomposition. Existing guidelines provide advice for a safe handling but are still deficient with regard to quantifying the static equivalent pressures experienced by the wall of a pipe when exposed to an internal detonative decomposition reaction. By applying the pipe wall deformation method we determined the static equivalent pressures occurring in long pipes. Once the static equivalent pressure is known, the well-established pressure vessel design guidelines, which can cope with static loads, can be applied for detonation pressure proof pipe design in all cases where the detonation speed is not close to the propagation speed of the flexural waves in the pipe. The tests revealed further important new details characterizing the detonative decomposition of C2H2: 1) The static equivalent pressure at the location of the occurrence of the deflagration to detonation transition (DDT) turned out to decrease relatively with increasing initial pressure. 2) When exceeding an initial pressure of approximately 12 bar abs there was no longer a stage of instable detonation after the occurrence of the deflagration to detonation transition, but the reaction front immediately propagated as a stable detonation. 3) It was found that the Chapman-Jouguet theory, which provides reasonably precise predictions for the propagation speed of the stable detonation and the Chapman-Jouguet pressure ratio in the case of common stoichiometric combustible/oxidant mixtures, seems to fail in the case of the decomposition of C2H2. A possible reason for this could be the fact that the decomposition reaction, in contrast to all other combustion reactions, generates both gaseous and solid reaction products. 4) By combining the results of recent work on detonations in ethylene/O2/N2-mixtures published in PVP2013-97677 and the present tests, a good estimate for the Chapman-Jouguet pressure ratio of the detonative decomposition reaction of C2H2 could be derived.

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Habicht, Fabian E., Fatma C. Yücel, Niclas Hanraths, Neda Djordjevic e Christian Oliver Paschereit. "Lean Operation of a Pulse Detonation Combustor by Fuel Stratification". In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-16169.

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Abstract Pressure gain combustion is a promising concept to substantially increase the thermal efficiency of gas turbines. One possible implementation that has been frequently investigated are pulse detonation combustors (PDCs), as they permit stable and reliable operation. At the same time, the need for part-load operation and low NOx emissions requires combustion concepts in the lean regime. However, realizing lean combustion is still very challenging in PDCs since the deflagration to detonation transition (DDT) is very sensitive to the reactant composition. The present work investigates an approach to realize lean combustion in PDC by applying fuel stratification experimentally. The scope is to find the necessary increase of fuel concentration inside the pre-detonation chamber to provide reliable DDT with respect to the overall equivalence ratio. Emission measurements in the exhaust of the PDC allow for a quantification of the NOx emissions as a function of the injected fuel profile. A valveless PDC test rig is used, which contains a shock focusing geometry for detonation initiation and is ignited by a spark plug close to the upstream end wall. The subsequent expansion of the burned gas and interaction of the flame front with turbulence leads to the formation of a leading shock inside the pre-detonation chamber, which is then focused inside a converging-diverging geometry. The successful initiation of a detonation wave by shock focusing is very sensitive to the pressure ratio across the leading shock, which can be influenced by initial pressure, reactant composition and flow velocity. Results reveal that fuel stratification allows for reliable detonation initiation at a global equivalence ratio of ϕglob = 0.65, whereas repeatable successful operation with non-stratified fuel injection is limited to ϕglob ≥ 0.85.

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Schildberg, Hans-Peter. "Experimental Determination of the Static Equivalent Pressures of Detonative Explosions of Ethylene/O2/N2-Mixtures and Cyclohexane/O2/N2-Mixtures in Long and Short Pipes". In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84493.

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In the recent past (PVP2013-97677, PVP2014-28197, PVP2015-45286, PVP2016-63223) we had started to determine the static equivalent pressures (pstat) of the eight detonative pressure scenarios in long and short pipes for different detonable gas mixtures. The pstat-values are of vital importance for process design: by assigning static equivalent pressures to the highly dynamic detonative pressure peaks it is possible to apply the established pressure vessel guidelines, which can only cope with static loads, in the design of detonation pressure resistant pipes. In the previous publications the parameter R was defined as the ratio between pstat at the location where transition from deflagration to detonation occurs and pstat in the region of the stable detonation. One important finding was that R depends on the reactivity of the gas mixture. So far, R cannot be predicted from first principles or from combustion parameters, but can only be determined experimentally. The ratio R has a special significance, because it not only determines pstat for the Deflagration to Detonation Transition (DDT) in long pipes (first detonative pressure scenario), but also gives a good estimate for two of the three scenarios relevant in the design of short pipes: DDT and the coalescence of DDT and reflection. The present paper concludes the test series conducted at BASF during the last 4 years. It presents additional experimental data showing the variation of R over the entire detonative range of Ethylene/O2/N2 mixtures and along the stoichiometric line of Cyclohexane/O2/N2 mixtures. Based on the variation of R for these ternary mixtures and for the mixtures presented in the preceding publications, a typical variation of R for a general combustible/O2/N2-mixture is estimated over the entire explosive range. By means of this estimation the static equivalent pressures of the six design-relevant detonative pressure scenarios of any combustible/O2/N2-mixture can now be derived combining the parameter R with the Chapman-Jouguet pressure ratio, which can be calculated in a straightforward manner from thermodynamic properties.

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Zou, Zhiqiang, Jian Deng e Yu Zhang. "CFD Analysis on Hydrogen Risk in Subcompartment of the Containment". In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-16171.

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Hydrogen combustion in the containment building may be a threat to containment integrity. Especially in some subcompartments, local hydrogen detonation likely to happen, which may destroy the containment structure or the safety equipments in the containment. A study has been carried out using the GASFLOW three-dimensional CFD code to evaluate the hydrogen distribution in the subcompartment during a severe accident. The GASFLOW calculation has provided detailed results for the spatial distribution of gas concentrations in the reactor coolant pump (RCP) compartment and the steam generator (SG) compartment within containment, the high local hydrogen concentration was found in the local area. Then, three kinds of different hydrogen mitigation measures which were optimizing compartment structure, hydrogen recombiner and igniter were analyzed and compared. The σ criterion and λ criterion are used for conservative estimates of the flame acceleration (FA) potential and the possibility of deflagration to detonation transition (DDT) in the compartment after using the mitigation measures, respectively.

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