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Numerical simulation of flame acceleration and DDT(deflagration to detonation transition) in hydrogen-air mixtures with concentration gradients

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ENERGY SOURCES PART A-RECOVERY UTILIZATION AND ENVIRONMENTAL EFFECTS 2021年

作者： Liu, Yang Yang, Xing Fu, Zhixi Chen, Peng China Univ Min & Technol Beijing Sch Emergency Management & Safety Engn Beijing 100083 Peoples R China

In this paper, a coupled new solver is used to simulate the acceleration and deflagration to detonation transition (DDT) of inhomogeneous mixtures flame under obstacle conditions. Analyzed the variations of flame front, pressure and density with time. The experimental results show that the vertical concentration gradient affects the chemical reaction rate in the combustion reaction zone, resulting in the flame front stretching along the "front up-back down." At the same time, the flame propagation velocity is affected by obstacles. After multi-stage "acceleration-deceleration," it reaches 2700 m/s at 1.23 m from the ignition center, and the pressure jumps to 5.0 MPa. Finally, the transition from detonation to detonation is completed. It is worth noting that the local explosion point is in the corner of the obstacle or pipe wall. This simulation method is compatible with low Mach number laminar flow, turbulent flow, and compressible reaction flow problems under high Mach number. It provides prospective prediction for flame acceleration and detonation formation during hydrogen combustion and detonation engine operation.

关键词： OpenFOAM H-2 concentration gradient flame acceleration deflagration to detonation transition

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Experimental Study on the deflagration-to-detonation transition Distance in Millimeter-Scale Smooth Tubes

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AIAA JOURNAL 2021年第8期59卷 3144-3151页

作者： Zhang, Penggang Pan, Zhenhua Zhu, Yuejin Wang, Qian He, Zhixia Pan, Jiaying Jiangsu Univ Sch Energy & Power Engn Zhenjiang 212013 Jiangsu Peoples R China Jiangsu Univ Sch Energy & Power Engn Inst Energy Res Zhenjiang 212013 Jiangsu Peoples R China Tianjin Univ State Key Lab Engines Tianjin 300072 Peoples R China

The deflagration-to-detonation (DDT) run-up distance LDDT for small-sized tubes is an important parameter for determining the position of a detonation initiation in the pulse detonation propulsion device as well as industrial safety. However, its variation tendency is insufficiently clarified, owing to complex multiple competing mechanisms between the properties of mixtures and the negative displacement effect of the boundary layer (the heat and momentum losses from wall). In this paper, the authors assess the LDDT of a stoichiometric ethylene/oxygen mixture in four capillary tubes based on high-speed photography measurements. Compared with macrotubes, the experimental results indicate that the area divergence xi induced by the boundary layer causes the relationship between LDDT and p0 and/or d to vary. Further comparative analysis suggests that a critical value of about xi =0.1 can be employed to distinguish between microtube and macrotube behavior. As such, microtube behavior is defined according to the area divergence xi, and not only based on the tube diameter. Finally, a theoretical model is introduced to predict the LDDT and is reliable for a stoichiometric ethylene/oxygen mixture in micro- and macrotubes. The conclusions in this study can provide potential applications for practical predetonator and micropulse detonation engines.

关键词： deflagration to detonation transition Boundary Layer Thickness Industrial Safety detonation Waves Viscosity Energy Density Viscous Drag Quenching Effect Metal Oxide Semiconductors Charge Coupled Device

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Numerical investigation of deflagration to detonation transition in closed ducts under various working conditions

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ACTA ASTRONAUTICA 2019年 162卷 109-120页

作者： Soleimanpour, Reza Nemati, Hossain Islamic Azad Univ Marvdasht Branch Dept Mech Marvdasht Iran

In the present study, a turbulent deflagration to detonation transition in gas mixtures of H-2-O-2 with a vertical concentration gradient in a closed duct was investigated numerically using OpenFOAM package. In this regard, the computational model is based on accounts for deflagrative flame propagation, autoignition as well as the formulation of a reaction progress variable. The simulation was carried out with several reaction mechanisms such as Warnatz, Oran, O-Conaire, Detailed, Skeletal, and GRI 2.11 mechanisms. It works on relatively coarse grids and indicates a good agreement with available experiment data when the O-Conaire mechanism was used. After validation of the numerical results, the DDT behavior was investigated under different working conditions including detonation in wavy closed ducted. Furthermore, the effects of the initial ignition power were investigated. The results were shown that changes in the duct geometry and initial ignition power have sensitive effects of DDT structure.

关键词： deflagration to detonation transition Reaction mechanisms Initial ignition power

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Investigation of Controlled deflagration-to-detonation transition of Hydrocarbon Fuels

Investigation of Controlled Deflagration-to-Detonation Trans...

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Hytovick, Rachel Chin, Hardeo Ahmed, Kareem Univ Cent Florida Prop & Energy Res Lab Orlando FL 32826 USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

The current work attempts to characterize the turbulent transition from deflagration to detonation (DDT) in oxygen-enriched methane flames. As detonation engines enter the aviation propulsion community offering a more efficient alternative to traditional combustion engines, there becomes a need to provide a dependable fuel source. Previously, hydrogen and air at varying equivalence ratios were studied, which revealed the various mechanisms behind how detonations form as well as the general characteristics of DDT. However, hydrocarbons, notably methane, remain a favorable and more reliable fuel source. To experimentally examine these traits, a premixed nitrogen-oxygen-methane flame is ignited in a semi-confined channel. The propagating combustion products and unburned reactants propagate through a series of perforated plates which induces turbulence in the mixture. Eventually the flame undergoes rapid acceleration, forming a leading shockwave followed by a region of compressed reactants. As the compressed region becomes hot, a flame kernel then ignites and expands throughout the flame forming a detonation wave. This experiment will observe the phenomenon of DDT through high speed schlieren and pressure transducers. Pressure and velocity measurements are then extracted through the diagnostics and used to help quantify the DDT phenomenon.

关键词： deflagration to detonation transition Hydrocarbon Fuels Pressure Transducers detonation Waves Aviation Rotating detonation Engine Aerospace Engineering Particle Image Velocimetry Chemiluminescence Isotropic Turbulence

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Mechanistic insights into the initial explosion in the deflagration-to-detonation transition

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COMBUSTION AND FLAME 2022年 242卷

作者： Feagin, Trevor A. Heatwole, Eric M. Eastwood, David S. Lopez-Pulliam, Ian Connolley, Thomas Bourne, Neil K. Parker, Gary R. Los Alamos Natl Lab Explos Applicat & Special Projects M 6 POB 1663 Los Alamos NM 87545 USA Univ Manchester Harwell Campus Didcot OX11 0DE Oxon England Diamond Light Source Ltd Harwell Sci & Innovat Campus Didcot OX11 0DE Oxon England Univ Manchester Sch Engn Manchester M13 9PL England

This work presents an imaging study of the complex and often overlooked early-onset mechanisms of the deflagration-to-detonation transition (DDT). Columns of granular octahydro-1,3,5,7-tetranitro-1,3,5,7tetrazocine (HMX) doped with tungsten tracer particles are ignited thermally by hot wire and the resulting reactions are studied via high-speed X-ray radiography utilizing the Diamond Light Source synchrotron. The observed results provide insights into the initial development of the DDT process, resulting in a proposed mechanism for the slow initial steps in DDT for thermally ignited, low bulk-density granular explosive contained in a quasi-one dimensional tube configuration. In order to clarify the proposed mechanism, the terms preferential flow channel and matrix burning are adapted from the soil mechanics and hydrology literature to further elucidate the role of convective burning in DDT. The proposed mechanism helps to clarify the ongoing debate on the transport of gases in the Baer-Nunziato and reduced Baer-Nunziato models and suggests that applicability of each interpretation depends on which step in the mechanism is being described.

关键词： DDT deflagration to detonation transition

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deflagration-to-detonation transition inside reactant-product mixing layers

Deflagration-to-detonation transition inside reactant-produc...

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Shi, Xian Crane, Jackson Wang, Hai Stanford Univ Mech Engn Stanford CA 94305 USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

The deflagration-to-detonation transition (DDT) process inside reactant-product mixing layers is studied using one-dimensional transient simulations of stoichiometric hydrogen-air mixtures. Such processes are seen to be responsible for the multi-front detonation propagation in rotating detonation engines (RDEs). For a given mixture, two modes of combustion dynamics, detonation and deflagrative flame, are observed at different mixing layer lengths. A critical mixing layer length can be identified for detonation formation using the Zeldovich theory, where the local characteristic velocity - the inverse of spatial gradient of ignition delay time - is equal to the theoretical Chapman-Jouguet (CJ) speed. As the mixing layer is comprised of mostly diluted or partially reacted mixtures, detonation formation is not possible in regions of relatively high burnt mixture content even if the Zeldovich criterion is met. The impact of initial pressure and addition of ignition promoter on the DDT process are also investigated. At higher initial pressures, the critical mixing layer length becomes smaller, in agreement with the experimental observation that the multi-front operation mode occurs more favorably at elevated pressures. Ignition promoting additives such as ozone does not affect the DDT behavior, as the reduction in ignition delay time does not change the location of critical characteristic velocity. Knowing the critical mixing layer length scales, the occurrence of multi-front RDE operation can be estimated by comparing the residence time of a single detonation front in RDEs to the developing time of the mixing layer.

关键词： deflagration to detonation transition Characteristic Velocity Rotating detonation Engine Chemical Energy Adaptive Mesh Refinement Internal Combustion Engines Finite Volume Method Numerical Simulation Runge Kutta Methods Chemical Kinetics

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deflagration to detonation transition in JP-10 mist/air mixtures in a large-scale tube

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JOURNAL OF HAZARDOUS MATERIALS 2017年第Oct.5期339卷 100-113页

作者： Li, Shuzhuan Liu, Qingming Chen, Xu Huang, Jinxiang Li, Jing Beijing Inst Technol State Key Lab Explos Sci & Technol Beijing 100081 Peoples R China Beijing Municipal Inst Labour Protect Beijing 100081 Peoples R China

deflagration to detonation transitions (DDTs) in JP-10 mist/air mixtures have been studied in a horizontal multiphase combustion and explosion tube with inner diameter of 199 mm and length of 32.8 m. The mist/air mixtures were generated by injecting liquid samples into the experimental tube. Experiments were performed at 298 k and 101 kPa with equivalence ratio ranged from 0.51 to 2.09. The coupling process of deflagration wave with leading shock wave and low-velocity self-sustained detonation were observed in JP-10 mist/air mixture with a concentration of 142.86 g/m(3), and the average velocity of the self-sustained detonation wave is 510 m/s, which is as low as 26% of C-J value. The low-velocity detonation in JP-10 mist/air mixture can be explained by the low-volatile property of JP-10 liquid and boundary condition. The leanest and richest critical detonable concentrations were studied. The detonation structure was studied by using pressure sensors array mounted in the wave structure test section. A single-head spin detonation wave front was observed and the cellular structure resulting from the spinning movement of the triple point was analyzed. (C) 2017 Elsevier B.V. All rights reserved.

关键词： deflagration to detonation transition detonation structure JP-10 mists

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Effects of jet in crossflow on flame acceleration and deflagration to detonation transition in methane-oxygen mixture

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COMBUSTION AND FLAME 2018年第Dec.期198卷 69-80页

作者： Peng, Han Huang, Yue Deiterding, Ralf Luan, Zhenye Xing, Fei You, Yancheng Xiamen Univ Sch Aerosp Engn Xiamen 361005 Peoples R China Univ Southampton Fac Engn & Environm Southampton SO17 1BJ Hants England

The fluidic jet turbulator has been a novel perturbation generator in the pulse-detonation engines research field for the past few years. In this paper, an experiment is performed to study the deflagration to detonation transition (DDT) process in a detonation chamber with a reactive transverse methane-oxygen mixture jet in crossflow (JICF). The jet injection arrangement is fundamentally investigated, including single jet and various double jets patterns. Corresponding two-dimensional direct numerical simulations with a multistep chemical kinetics mechanism are employed for analyzing details in the flow field, and the interaction between the vortex and flame temporal evolution is characterized. Both the experiments and simulations demonstrate that the JICF can distinctly accelerate flame propagation and shorten the DDT time and distance. The vortex stream induced by the jet distorts and wrinkles the flame front resulting in local flame acceleration. Moreover, the double jet patterns enhance flame acceleration more than the single jet injection because of the intrinsic counter-rotating vortex pairs and enhanced turbulence intensity. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

关键词： Flame acceleration deflagration to detonation transition Jet in crossflow Flame-vortex interactions Methane flame

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Numerical Simulation of the deflagration to detonation transition in Granular High-Energy Solid Propellants

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CENTRAL EUROPEAN JOURNAL OF ENERGETIC MATERIALS 2019年第4期16卷 504-519页

作者： Zhen, Fei Wang, Liqiong Wang, Zhuoqun Beijing Inst Technol State Key Lab Explos Sci & Technol Beijing 100081 Peoples R China

This paper describes a one-dimensional code developed for analyzing the two-phase deflagration to detonation transition (DDT) phenomenon in granular high-energy solid propellants. The deflagration to detonation transition model was established based on a one-dimensional two-phase reactive flow model involving basic flow conservation equations and constitutive relations. The whole system was solved using a high resolution 5th-order WENO (Weighted Essentially Non-Oscillatory) scheme for spatial discretization, coupled with a 3rd-order TVD Runge-Kutta method for time discretization, to improve the accuracy and prevent excessive dispersion. An inert two-phase shock tube problem was carried out to access the developed code. The DDT process of high-energy solid propellants was simulated and the parameters of detonation pressure, run distance to detonation and time to detonation were calculated. The results show that for a solid propellant bed with solid volume fraction 0.65. the run distance to detonation was about 120 mm, the detonation induced time was 28 mu s, and the detonation pressure was 18 GPa. In addition, the effects of solid volume fraction (phi(s)) and pressure exponent (n) on the deflagration to detonation transition were also investigated. The numerical results for the DDT phenomenon are in good agreement with experimental results available in the literature.

关键词： deflagration to detonation transition two-phase reactive flow model WENO solid volume fraction pressure exponent

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Numerical simulation of deflagration to detonation transition in granular HMX explosives under thermal ignition

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JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY 2017年第1期127卷 975-981页

作者： Dong, Hefei Zan, Wentao Hong, Tao Zhang, Xiaoli Inst Appl Phys & Computat Math 2 Fenghao Donglu Beijing 100094 Peoples R China

To study the deflagration to detonation transition process in granular explosive under thermal ignition condition, the conductive burning is introduced into the classical model. The novel space-time conservation element and solution element method is applied to solve the mathematical governing equations. The transition process in granular HMX bed which is packed to 85 % of theoretical maximum density is simulated. The development of conductive burning, convective burning and detonation is analyzed. In the early stage, the combustion propagates slowly. It moves no more than 0.2 mm within 8.16 ms. After onset of convective burning, it takes only 20 mu s to form a steady detonation with the velocity of 8165 m s(-1). The time to detonation increases with the decrease in particle diameter.

关键词： deflagration to detonation transition Conductive burning Convective burning Granular explosive Numerical simulation

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