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Aiming at the problem that gun propellants are prone to deflagration under high-temperature chamber pressure, this paper proposes a high-temperature resistant coating using hydroxypropyl methyl cellulose (HPMC) as the film-forming material, and zirconia (ZrO 2 ) and titanium dioxide (TiO 2 ) as functional fillers. The results show that the 5s explosion point is increased by 28.9 °C, and the high-temperature resistance time at 200 °C is increased by 27.233 s. The research method for preparing high-temperature resistant composite coatings proposed in this study can effectively improve the high-temperature resistance performance of gun propellants.

To ensure the reliability of the Exploding Foil Deflagration Igniter (EFDI) and at the same time reduce its ignition energy, the standard B/KNO 3 composition was used as the ignition charge for the EFDI. The effects of variations in exploding foil bridge dimensions and flyer thickness on the ignition energy of the B/KNO 3 composition were investigated within the Slapper-BPN charge structure. The results show that both the bridge size and flyer thickness are critical factors influencing the ignition energy of B/KNO 3 composition. Within specific ranges, increasing the bridge size, the minimum ignition voltage of the EFDI first decreases then increases and increasing the flyer thickness reduces the minimum ignition voltage of the EFDI. Under the conditions of a 0.4 μF charging capacitor, a B/KNO 3 compaction density of 1.50 g.cm —3 , a bridge size of 0.35 mm × 0.35 mm, and a flyer thickness of 75 μm, the minimum ignition voltage of the EFDI was reduced to 1100 V. The feasibility of the standard B/KNO 3 composition for direct application to the engineering design of Slapper-BPN EFDI was verified.

To investigate the penetration-deflagration coupled characteristics of encased reactive fragments, a numerical simulation model of the encased reactive fragments penetration plate was developed based on Ansys/Lsdyna. Firstly, the mechanical response of the encased reactive fragments penetration plate was obtained using the Johnson-Cook material model, which yielded the internal pressure distribution of the reactive material. Subsequently, the JWL model was used to simulate the penetration-deflagration process, where the JWL parameters of the reactive material were determined based on the condensed reaction material detonation theory. The results indicate that a larger plate thickness value leads to a decrease in the overall internal pressure of the reactive material, thereby reducing the reaction rate of the reactive material. The plate thickness has a marginal impact on the reaction of the encased reactive fragments, but it significantly influenced the deformation and break of the shell, this paper gives the optimal shell and plate thickness under the impact conditions. coefficient and stability.

Future terrestrial and interplanetary travel will require high-speed flight and reentry in planetary atmospheres by way of robust, controllable means. This, in large part, hinges on having reliable propulsion systems for hypersonic and supersonic flight. Given the availability of fuels as propellants, we likely will rely on some form of chemical or nuclear propulsion, which means using various forms of exothermic reactions and therefore combustion waves. Such waves may be deflagrations, which are subsonic reaction waves, or detonations, which are ultrahigh-speed supersonic reaction waves. Detonations are an extremely efficient, highly energetic mode of reaction generally associated with intense blast explosions and supernovas. Detonation-based propulsion systems are now of considerable interest because of their potential use for greater propulsion power compared to deflagration-based systems. An understanding of the ignition, propagation, and stability of detonation waves is critical to harnessing their propulsive potential and depends on our ability to study them in a laboratory setting. Here we present a unique experimental configuration, a hypersonic high-enthalpy reaction facility that produces a detonation that is fixed in space, which is crucial for controlling and harnessing the reaction power. A standing oblique detonation wave, stabilized on a ramp, is created in a hypersonic flow of hydrogen and air. Flow diagnostics, such as high-speed shadowgraph and chemiluminescence imaging, show detonation initiation and stabilization and are corroborated through comparison to simulations. This breakthrough in experimental analysis allows for a possible pathway to develop and integrate ultra-high-speed detonation technology enabling hypersonic propulsion and advanced power systems.

Although the ignition-and-growth model can simulate the ignition and detonation behavior of traditional energy materials well, it seems insufficient to simulate the impact-induced deflagration behavior of reactive materials (RMs) using current finite element codes due to their more complicated ignition threshold and lower reaction rates. Therefore, a simulation method for the impact-induced deflagration behavior of a reactive materials projectile (RMP) is developed by introducing tunable ignition threshold conditions for RMs, and a user-defined subroutine is formed by the secondary development on the equation of state (EOS). High-velocity impact experiments were performed to prove the validity of simulations. The results show that the user-defined subroutine for RMs is competent in simulating the ignition and deflagration behavior under impact conditions, because the reaction ratio, morphology and temperature distribution of RMP fragments are all well consistent with experiments, theory, and current reports from other researchers. In this way, the quantitative study on the deflagration reaction of RMs can be implemented and relevant mechanisms are revealed more clearly.

AbstractFlame acceleration (FA) and the deflagration-to-detonation transition (DDT) are among the most interesting and exciting phenomena in the field of combustion and explosion of gases. From both practical and theoretical points of view, it is important to understand the basic laws governing these phenomena as well as the physical and/or chemical mechanisms and features of the process. High-speed flame-front photography during the deflagration of a premixed gas mixture in a long smooth tube with transparent walls was performed. A stoichiometric mixture of acetylene with oxygen diluted with argon by 25% is used. The experiments are carried out in a transparent cylindrical tube with an inner diameter of 60 mm and a length of 6 meters. The evolution of the structure and shape of the flame front from the moment of initiation of deflagration by a weak ignition source to the formation of a detonation wave is determined. Four characteristic phases of the propagation process are distinguished: at the first stage, the flame accelerates, then slows down, followed by flame propagation at an almost constant speed, and finally repeated acceleration, during which detonation is formed. It is shown how the dynamics of the process changes with a change in the initial pressure of the mixture. The most interesting and poorly studied stage of the DDT, the stage of intensive reacceleration, during which the flame abruptly changes shape, is described in detail.

Designing a pressure relief structure is an essential method to mitigate the intensity of the cookoff process in the fuze. In order to investigate the influence of the venting structure on the fast cook-off response characteristics of the fuze, a fast cook-off test with and without pressure relief structures was designed for typical naval gun ammunition fuses, and a universal cook-off model (UCM) suitable for fast cook-off was developed for simulation to obtain the response characteristics of fuzes under different conditions. The results indicate that the fuze with sealed structure undergoes deflagration reactions, while the fuze with a vented structure undergoes burning reactions. The venting structure significantly reduces the reaction intensity of the fuze but has a minor effect on response time. The ignition position is located in the central area at the bottom of the fuze, with the ignition temperature of JHX-1 approximately 483K, and the RDX component dominates the ignition process. The developed UCM model can accurately predict the impact of internal pressure variations on the reaction process within the fuze, the internal pressure of the fuze booster explosive decreases by 24.32% when the venting structure is flushed open, which effectively slowing down the chemical reaction process and reducing the reaction intensity. Additionally, there is minimal melting in the ignition area, and resulting in minimal impact on the fuze response characteristics.

Lithium-ion batteries (LIBs) are widely used in electric vehicles (EV) and energy storage stations (ESS). However, combustion and explosion accidents during the thermal runaway (TR) process limit its further applications. Therefore, it is necessary to investigate the uncontrolled TR exothermic reaction for safe battery system design. In this study, different LIBs are tested by lateral heating in a closed experimental chamber filled with nitrogen. Moreover, the relevant thermal characteristic parameters, gas composition, and deflagration limit during the battery TR process are calculated and compared. Results indicate that the TR behavior of NCM batteries is more severe than that of LFP batteries, and the TR reactions becomes more severe with the increase of energy density. Under the inert atmosphere of nitrogen, the primarily generated gases are H2, CO, CO2, and hydrocarbons. The TR gas deflagration limits and characteristic parameter calculations of different cathode materials are refined and summarized, guiding safe battery design and battery selection for power systems.

Changing the flow rate of reactants being injected into a rotating detonation combustor (RDC) results in interesting behavior of the system. Prior studies have found that an increase in mass flow rate gradually increases the detonation wave speed before splitting the wave into multiple fronts. The focus of this study is in understanding the physics of such behavior through a combination of experiments and numerical simulations. For this purpose, the axial air inlet-based RDC geometry is used. In the experiments, the wave velocity increased similar to prior studies. Corresponding full-scale simulations show that increase in mass flow rate by increasing pressure of the feed plenums shortens the recovery time of the injectors. This causes a more uniform fuel–air mixture to form prior to the arrival of the detonation wave. As a result, a more ideal detonation is observed, which leads to an increased wave velocity. Details of the detonation structure and variation with mass flow rate are analyzed. The presence and variation of the different deflagration zones in such non-premixed RDCs are also discussed.

Subluminous Type Ia supernovae, such as the Type Iax–class prototype SN 2002cx, are described by a variety of models such as the failed detonation and partial deflagration of an accreting carbon-oxygen white dwarf star or the explosion of an accreting, hybrid carbon-oxygen-neon core. These models predict that bound remnants survive such events with, according to some simulations, a high kick velocity. We report the discovery of a high proper motion, low-mass white dwarf (LP 40-365) that travels at a velocity greater than the Galactic escape velocity and whose peculiar atmosphere is dominated by intermediate-mass elements. Strong evidence indicates that this partially burnt remnant was ejected following a subluminous Type Ia supernova event. This supports the viability of single-degenerate supernova progenitors.