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deflagration to detonation transition in weakly confined conditions for a type of potentially novel green primary explosive:Al/Fe_(2)O_(3)/RDX hybrid nanocomposites

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Defence Technology（防务技术） 2023年第4期22卷 28-36页

作者： Qing-ping Luo Xin-ping Long Fu-de Nie Gui-xiang Liu Chao Wu State Key Laboratory of Environmental-friendly Energy Materials Southwest University of Science and TechnologyMianyang621010China Institute of Chemical Materials Chinese Academy of Engineering PhysicsMianyang621900China

The properties of the combustion and deflagration to detonation transition(DDT)of Al/Fe_(2)O_(3)/RDX hybrid nanocomposites,a type of potentially novel lead-free primary explosives,were tested in weakly confined conditions,and the interaction of Al/Fe_(2)O_(3)nanothermite and RDX in the DDT process was studied in *** show that the amount of the Al/Fe_(2)O_(3)nanothermite has a great effect on the DDT properties of Al/Fe_(2)O_(3)/RDX *** addition of Al/Fe_(2)O_(3)nanothermite to RDX apparently improves the firing properties of RDX.A small amount of Al/Fe_(2)O_(3)nanothermite greatly increases the initial combustion velocity of Al/Fe_(2)O_(3)/RDX nanocomposites,accelerating their DDT *** the contents of Al/Fe_(2)O_(3)nanothermite are less than 20 wt%,the DDT mechanisms of Al/Fe_(2)O_(3)/RDX nanocomposites follow the distinct abrupt mode,and are consistent with that of RDX,though their DDT processes are *** RDX added into the Al/Fe_(2)O_(3)nanothermite increases the latter's peak combustion velocity and makes it generate the DDT when the RDX content is at least 10 wt%.RDX plays a key role in the shock compressive combustion,the formation and the properties of the DDT in the flame propagation of *** with RDX,the fast DDT of Al/Fe_(2)O_(3)/RDX nanocomposites could be obtained by adjusting the chemical constituents of nanocomposites.

关键词： Green primary explosives Al/Fe_(2)O_(3)/RDX nanocomposites deflagration to detonation transition Mechanism

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deflagration to detonation transition in Heterogeneous Mixtures Containing Ethanol/Acetone and Oxygen

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JOURNAL OF PROPULSION AND POWER 2023年第6期39卷 840-848页

作者： Kadosh, Hertzel Michaels, Dan Technion Israel Inst Technol Fac Aerosp Engn IL-32000 Haifa Israel Technion Israel Inst Technol Rocket Propuls Ctr IL-32000 Haifa Israel Technion Israel Inst Technol Aerothermodynam Lab Fac Aerosp Engn IL-32000 Haifa Israel

Liquid fuel is the choice for volume-limited propulsion systems, including detonation-based propulsion. A liquid fuel with high vapor pressure has the advantage of more fuel vapor in the mixture, which supports the transition from deflagration to detonation. This paper reports on an experimental study of deflagration-to-detonation transition (DDT) in a pulse detonation engine with heterogenous mixtures of oxygen and ethanol or acetone. Single-cycle tests were taken for different fuels, equivalence ratios, and DDT enhancement methods. The size distribution of fuel droplets was characterized at the atomizer and engine exit. The effect of the fuel evaporation was dominant for the acetone spray only. Comparing the measured detonation velocities of the two mixtures, a lower velocity deficit relative to the theoretical Chapman-Jouguet detonation velocity was measured for the acetone-oxygen mixtures, and this behavior is related to the higher amount of fuel vapor that existed in the mixtures. Moreover, a shorter transition to detonation was observed in the acetone-oxygen mixture. The addition of a Shchelkin spiral reduced the DDT distance;however, the Chapman-Jouguet condition could be reached only downstream of the obstacle. The measured detonation cell size of the heterogeneous acetone-oxygen mixture was smaller than that of the ethanol-oxygen mixture, indicating that it is more detonable.

关键词： Liquid Fuels detonation Waves Acetone Fuel Oxygen Ethanol Fuel deflagration to detonation transition detonation Cell Size Heterogeneous Mixture Pulse detonation Engine detonation

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Experimental study of the perturbation of the cavity on the deflagration to detonation transition

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COMBUSTION AND FLAME 2025年 273卷

作者： Ma, Tianbao Wu, Deyao Li, Jian Beijing Inst Technol State Key Lab Explos Sci & Safety Protect Beijing 100081 Peoples R China

The perturbation in the deflagration to detonation transition process is investigated experimentally by utilizing one cavity and three successive cavities to induce weak and strong turbulences, respectively. The cavity serves as a "hot spot" in propagating deflagration, generating a pulse of shock waves locally and accelerating its velocity. The results suggest three modes of cavity perturbation on deflagration acceleration: direct transition to detonation, secondary acceleration to detonation after a long distance of steady propagation or mild decline in velocity, and failure to transition to detonation. This variation can primarily be attributed to various strengths of the precursor shock resulting from the acceleration of the flame by the cavity disturbance. The cavity perturbation must satisfy specific critical conditions to directly assist in the deflagration-to-detonation transition. Firstly, the escalated flame velocity due to the cavity perturbation must exceed the sound speed in combustion products. Secondly, the acceleration of the velocity rise must surpass specific critical values for the transition to detonation to be smoothly completed without a secondary acceleration.

关键词： detonation deflagration to detonation transition Cavity Perturbation

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deflagration to detonation transition in fast flames and tracking with chemical explosive mode analysis

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PROCEEDINGS OF THE COMBUSTION INSTITUTE 2021年第3期38卷 3529-3536页

作者： Jaravel, T. Dounia, O. Male, Q. Vermorel, O. CERFACS 42 Ave Gaspard Coriolis F-31057 Toulouse France Renault SAS 1 Ave Golf F-78288 Guyancourt France

In the context of vapour cloud explosion, the flame acceleration process can lead to conditions promoting deflagration to detonation transition (DDT), potentially leading to increased damages in accidental scenarios. This study focuses on this phenomenon by performing simulations of detonation reinitiation for fast flames in the Chapman?Jouguet deflagration regime. It is obtained experimentally by the attenuation of an incident detonation by an array of obstacles. A primary objective of the paper is to demonstrate the ability of the numerical model to reproduce the major experimental trends, namely the variation of the reinitiation propensity for different initial pressures and blockage ratios (BRs). Chemical explosive mode analysis (CEMA) is also adapted to the context of this study, in order to identify locally the propagation regime and to provide insights on the reinitiation mechanism. An a priori validation of the CEMA methodology is first performed on relevant canonical one-dimensional configurations. Subsequently, ensembles of five realizations are computed at different initial pressures and BRs and compared to experimental data. They are shown to reproduce the major observed trends in terms of detonation reinitiation length with respect to the operating conditions, with significant variability from one realization to another. In addition, the reinitiation mechanism is also found to be consistent with experimental observations and a previous numerical study of the same configuration. The CEMA methodology adapted to this context is able to identify locally the different propagation regimes, and to track the highly reactive zones that coherently couple with transverse pressure perturbations, leading to the formation of a strongly reacting kernel which eventually triggers the detonation reinitiation. (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

关键词： Fast flame detonation deflagration to detonation transition Chemical explosive mode analysis

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Plasma-assisted deflagration to detonation transition in a microchannel with fast-frame imaging and hybrid fs/ps coherent anti-Stokes Raman scattering measurements

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PROCEEDINGS OF THE COMBUSTION INSTITUTE 2023年第1期39卷 5561-5569页

作者： Vorenkamp, Madeline Steinmetz, Scott A. Chen, Timothy Y. Mao, Xingqian Starikovskiy, Andrey Kliewer, Christopher Ju, Yiguang Princeton Univ Dept Mech & Aerosp Engn Princeton NJ 08544 USA Sandia Natl Labs Livermore CA 94550 USA

This study examines kinetic enhancement by nanosecond dielectric barrier discharge (ns-DBD) plasma on fuel-lean, (13 = 0.7, dimethyl ether (DME), oxygen (O 2 ), and argon (Ar) premixture during deflagration to detonation transition (DDT) experiments in a microchannel. Nonequilibrium plasma produces active species and radicals as well as fast and slow heating of a mixture to promote ignition due to energetic electrons, ions, and electronic and vibrational excitations. Experiments are conducted to examine the influence of the plasma discharge on the premixture and on the resultant deflagration to detonation transition (DDT) onset time and distance through the use of high-speed imaging and one-dimensional, two-beam, femtosecond/picosecond, coherent anti-Stokes Raman scattering (CARS). A high-speed camera is used to trace the time histories of flame front position and velocity and to identify the dynamics and onset of DDT. The results show that plasma discharge can nonlinearly affect the onset time and distance of DDT. It is shown that a small number of plasma discharge pulses prior to ignition result in reduced DDT onset time and distance by 60% and 40%, respectively, when compared to the results without pre-excitation by ns discharges. The results also show that an increase of number of the plasma discharge pulses results in an extended DDT onset time and distance of 224% and 94%, respectively. Time history of the deflagration wave speed of DME and the analysis of ignition timescale under the choking condition of the burned gas of the deflagration wave suggest low temperature ignition may play a role for DME near the isobaric choking condition of the burned gas and the DDT. Plasma-induced low temperature oxidation of the reactive mixture is assessed via the CO 2 to O 2 ratio as measured through fs/ps CARS during the gas excitation in discharges. CARS measurements also confirm negligible vibrational and rotational heating of the gas by discharge. The present experiment

关键词： Nonequilibrium plasma deflagration to detonation transition Coherent anti-Stokes Raman scattering Dimethyl ether Low temperature chemistry

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The effects of flame generated turbulence for turbulent-induced deflagration to detonation transition

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PROCEEDINGS OF THE COMBUSTION INSTITUTE 2023年第3期39卷 2817-2824页

作者： Hytovick, Rachel Rising, Cal Morales, Anthony Genova, Tommy Berson, Joshua Ahmed, Kareem Univ Cent Florida Orlando FL 32828 USA Univ Cent Florida Mech & Aerosp Engn Eng 1Rm 217 Orlando FL 32828 USA

The turbulent deflagration to detonation transition (DDT) process occurs when a subsonic flame interacts with intense turbulence resulting in spontaneous acceleration and the onset of DDT. The mechanisms that govern the spontaneous ignition are deduced intricately in numerical simulations. This work experimentally explores the conditions that are known precursors to detonation initiation. More specifically, the experiment presented investigates the role of flame-generated compression as a cycle that continuously amplifies until a hotspot forms on the flame front and ignites. The study quantifies the compression comparatively against other flame regimes through ultra-high speed pressure measurements while qualitatively detailing flame generated compression through density gradients via schlieren imaging. Additionally, flow field measurements are quantified throughout the flow using simultaneous particle image velocimetry (PIV) and OH * chemiluminescence. The turbulence fluctuations and flame speeds are extracted from these measurements to identify the reactant conditions where flame-generated compression begins. Collectively, these simultaneous high-speed measurements provide detailed insight into the flame and flow field characteristics where the runaway process occurs. This work ultimately documents direct flow field measurements to extract the contribution of flame-generated turbulence on the turbulent deflagration to detonation transition process.& COPY;2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

关键词： Pressure Gain Combustion deflagration to detonation transition

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Effect of Plasma on the deflagration to detonation transition

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COMBUSTION SCIENCE AND TECHNOLOGY 2022年第13期194卷 2752-2770页

作者： Tropina, Albina A. Mahamud, Rajib Texas A&M Univ Dept Aerosp Engn College Stn TX 77843 USA Los Alamos Natl Lab T3 Fluid Dynam & Solid Mech Los Alamos NM USA

Numerical results of plasma supported deflagration to detonation transition have been presented. The mathematical model includes Reynolds averaged Navier-Stokes equations for the compressible medium, enthalpy equation, the standard k-omega turbulence model, transport equations for the progress variable and flame wrinkling factor. Non-equilibrium plasma was modeled as a source of radicals. Initial concentrations of radicals were taken from the detailed plasma simulation using a three-temperature plasma model. To model equilibrium plasma we used a Joule heating source with the conductivity depending on the energy deposition time. Simulations showed that the injection of radicals was more efficient than a thermal effect of plasma in the deflagration to detonation transition time and distance. We observed changes in the detonation cell size and improvement of the detonation structure stability with the plasma addition. Because the oxygen atoms injection primarily controls the phenomenon, the detonation cell size depends on the oxygen atoms concentration and on the orientation of the plasma energy spot with respect to the detonation wave.

关键词： deflagration to detonation transition non-equilibrium plasma numerical simulation detonation cell

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ANALYSIS OF PLASTIC DEFORMATION OF PIPES DUE TO deflagration to detonation transition USING STATIC EQUIVALENT PRESSURE

ANALYSIS OF PLASTIC DEFORMATION OF PIPES DUE TO DEFLAGRATION...

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ASME Pressure Vessels and Piping Conference (PVP)

作者： Mueller, Matthias Bernhardi, Otto-Ernst Denecke, Jens Schildberg, Hans-Peter Schmidt, Juergen Univ Appl Sci Karlsruhe Germany CSE Ctr Safety Excellence CSE Inst Pfinztal Germany BASF SE Safety Engn Ludwigshafen Germany

ISBN: (纸本)9780791886151

Explosions of premixed gases with DDT, the transition from deflagration to detonation, are a risk in the process industry with potentially catastrophic consequences. Robust and simple design methods are required for industrial use. Such a simplified design method based on finite element analysis is proposed to model the dynamic behavior of pipes loaded by gas explosions of premixed gases including DDT. First, it is reviewed how the pressure load of the gas explosion and the resulting material behavior has been modeled in previous publications. The analytical equations are then extended for describing the pressure load as a function of time and location by considering the leading compression wave as it affects the pressure load of the overdriven detonation. The extended analytical equations are parameterized using Chapman-Jouguet conditions and experimental results from publications for both static equivalent pressure and the location of the DDT. To describe the plastic material behavior at high strain rates, the well-known Johnson-Cook plasticity model is used. The material parameters of the model are derived from simple experiments, which are available in an industrial environment. The comparison of a finite element simulation with experimental data shows that the concept of equivalent static pressure can be extended to an FEM analysis, which in the future will allow the sizing of complete pipe systems including tees, bends and flanges while considering plastic deformation.

关键词： gas explosion deflagration to detonation transition DDT premixed gases plasticity pipe sizing finite element modelling

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Numerical modeling of plasma assisted deflagration to detonation transition in a microscale channel

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PROCEEDINGS OF THE COMBUSTION INSTITUTE 2024年第1-4期40卷

作者： Shi, Zhiyu Mao, Xingqian Thawko, Andy Ju, Yiguang Princeton Univ Dept Mech & Aerosp Engn Princeton NJ 08544 USA Princeton Plasma Phys Lab Princeton NJ 08540 USA

This work numerically studies the plasma assisted deflagration to detonation transition (DDT) of H2/O2 2 /O 2 mixtures in a microscale channel with detailed chemistry and transport. The results show that the DDT onset time is non- monotonically dependent on the discharge pulse number. The DDT is accelerated with small pulse numbers, whereas retarded with large ones. Two different DDT regimes, respectively at a small and large plasma discharge number, via acoustic choking of the burned gas and plasma-enhanced reactivity gradient without acoustic choking, are observed. Without plasma discharge, pronounced pressure and temperature gradients in front of the flame are generated by acoustic compression after the choking of the burned gas, triggering DDT via auto- ignition. With small plasma pulse numbers, the plasma-generated species enhance the ignition kinetics and lead to an increased reactivity in the boundary layer. After the choking of the burned gas, the plasma-enhanced reactivity advances the sequence of autoignition near the wall, strengthens ignition-shock wave coupling, and accelerates DDT. However, with a large discharge pulse number, a direct autoignition initiating DDT can occur without the acoustic choking of the burned gas due to the strongly accelerated reactivity and elevated temperature. In this case, DDT onset is retarded because the elevated temperature increases sonic velocity and the increased reactivity accelerates fuel oxidation in front of the flame, decelerating the formation of a leading shock and subsequent pressure buildup ahead of the flame. The present modeling reveals that no matter with or without plasma discharge, DDT is initiated by autoignition in thermal, pressure, and reactivity gradient fields via the Zel'dovich gradient mechanism. The acoustic choking of the burned gas may not be the necessary condition of DDT with strong plasma-enhanced reactivity gradient. This work provides an answer to the experimentally observed non-monotonic

关键词： Non-equilibrium plasma deflagration to detonation transition Zel'dovich gradient mechanism Autoignition Ignition-shock wave coupling

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deflagration to detonation transition in Chemical Rockets with Sudden Expansion / Divergence Regions

Deflagration to Detonation Transition in Chemical Rockets wi...

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AIAA Propulsion and Energy Forum

作者： Kumar, V. R. Sanal Chandrasekaran, Nichith Sankar, Vigneshwaran Sukumaran, Ajith Nejaamtheen, Mohammed Niyasdeen Doddi, Hema Sai Nagaraju Rafic, Sulthan Ariff Rahman Mohamed Baskaran, Roshan Vignesh Mariappan, Amrith Thianesh, U. K. Anandmoorthi Mohan, E. Pradeep, Rahul Ajay, M. Indian Space Res Org Trivandrum 695022 Kerala India Kumaraguru Coll Technol Coimbatore 641049 Tamil Nadu India Kumaraguru Coll Technol Dept Aeronaut Engn Coimbatore 641049 Tamil Nadu India IISc Indo Russian Project Bangalore Karnataka India Indian Inst Sci Dept Aerosp Engn Bangalore Karnataka India IIT Kanpur Dept Aerosp Engn Kanpur Uttar Pradesh India

ISBN: (数字)9781624106026

ISBN: (纸本)9781624106026

We discovered through theoretical studies that, at the creeping inflow conditions, any chemical rocket having port with the sudden expansion / divergent could predispose to deflagration-to-detonation-transition (DDT) at a critical total-to-static pressure ratio (TSPR) due to the phenomenon of Sanal flow choking. At the Sanal flow choking condition, the subsonic flow will get accelerated in the port of a rocket having uniform cross-sectional area due to the area blockage caused by the boundary layer displacement thickness (BLDT). At the Sanal flow choking condition, the lower critical detonation index (LCDI) is an exclusive function of the lowest heat capacity ratio (HCR) of the evolved gases;and the non-dimensional BLDT is an exclusive function of the HCR and the igniter/inflow Mach number. The mathematical model presented herein predicts the possibilities of DDT in all real-world fluid flow systems (continuum / non-continuum), at a critical TSPR, having port with sudden expansion and/or divergence regions or in constricted streamtubes. Note that when the pressure of the non-continuum fluid/nanofluid increases, average-mean-free-path decreases and thus, the Knudsen number reduces leading to a no-slip boundary condition with compressible viscous (CV) flow effect. The Sanal flow choking is a CV flow effect at which both the thermal choking and the wall-friction induced the flow choking converge at the sonic-fluid-throat creating the real-world fluid flow effect, which satisfies all the conservation laws of nature. The offshoot of this study reveals that the Sanal flow choking could lead to asymptomatic hemorrhage in biological systems, and susceptible to catastrophic failures of chemical energy systems including micro and nano thrusters due to the detonation. The risk of Sanal flow choking could be reduced by breaking the blockage, reducing the TSPR and/or increasing the HCR of the gases generating from the upstream region of the port of an internal flow system for ke

关键词： Chemical Rocket deflagration to detonation transition Mach Number In Compressible Viscous Flows Fluid Flow Heat Capacity Ratio Static Pressure Chemical Energy Catastrophic Failure Reynolds Averaged Navier Stokes

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