The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and ...The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.展开更多
This study investigates the paradoxical detonation behavior of TKX-50,a nitrogen-rich energetic material,exhibiting higher detonation velocities but lower metal acceleration ability compared to HMX.Through experimenta...This study investigates the paradoxical detonation behavior of TKX-50,a nitrogen-rich energetic material,exhibiting higher detonation velocities but lower metal acceleration ability compared to HMX.Through experimental measurements and theoretical calculations,we propose a novel three-factor competition mechanism to explain this phenomenon.TKX-50-based PBX formulations achieved detonation velocities up to 9100 m/s,surpassing HMX-based counterparts.However,cylinder expansion tests revealed a 15%reduction in metal acceleration ability.Thermochemical measurements showed lower detonation heat for TKX-50(4900 J/g)versus HMX(5645 J/g).Our mechanism involves:(1)compositional effects prevailing at high pressures;(2)Energy release becoming essential as pressure drops;(3)Pressure-dependent product composition evolution functioning at low pressure.VLW code calculations unveiled a"crossover"in Hugoniot curves,lending support to this mechanism.This study furnishes a new framework for comprehending the performance of nitrogen-rich energetic materials,with significant implications for the design and optimization of future high-energy density materials.展开更多
Excellent detonation performances and low sensitivity are prerequisites for the deployment of energetic materials.Exploring the underlying factors that affect impact sensitivity and detonation performances as well as ...Excellent detonation performances and low sensitivity are prerequisites for the deployment of energetic materials.Exploring the underlying factors that affect impact sensitivity and detonation performances as well as exploring how to obtain materials with desired properties remains a long-term challenge.Machine learning with its ability to solve complex tasks and perform robust data processing can reveal the relationship between performance and descriptive indicators,potentially accelerating the development process of energetic materials.In this background,impact sensitivity,detonation performances,and 28 physicochemical parameters for 222 energetic materials from density functional theory calculations and published literature were sorted out.Four machine learning algorithms were employed to predict various properties of energetic materials,including impact sensitivity,detonation velocity,detonation pressure,and Gurney energy.Analysis of Pearson coefficients and feature importance showed that the heat of explosion,oxygen balance,decomposition products,and HOMO energy levels have a strong correlation with the impact sensitivity of energetic materials.Oxygen balance,decomposition products,and density have a strong correlation with detonation performances.Utilizing impact sensitivity of 2,3,4-trinitrotoluene and the detonation performances of 2,4,6-trinitrobenzene-1,3,5-triamine as the benchmark,the analysis of feature importance rankings and statistical data revealed the optimal range of key features balancing impact sensitivity and detonation performances:oxygen balance values should be between-40%and-30%,density should range from 1.66 to 1.72 g/cm^(3),HOMO energy levels should be between-6.34 and-6.31 eV,and lipophilicity should be between-1.0 and 0.1,4.49 and 5.59.These findings not only offer important insights into the impact sensitivity and detonation performances of energetic materials,but also provide a theoretical guidance paradigm for the design and development of new energetic materials with optimal detonation performances and reduced sensitivity.展开更多
To explore the design criteria for composite charges and reveal the intrinsic relationship between the detonation wave propagation in composite charges and the overall energy distribution of shock waves,this study ana...To explore the design criteria for composite charges and reveal the intrinsic relationship between the detonation wave propagation in composite charges and the overall energy distribution of shock waves,this study analyzes the propagation and interaction processes of detonation waves in composite charges with different structural dimensions and explosive combinations. It also investigates the spatial distribution characteristics of the resulting shock wave loads. Based on dimensional analysis theory, a theoretical analysis of the shock wave overpressure distribution in free air fields is conducted. Utilizing the derived dimensionless function relationships, the hydrocode AUTODYN is employed to investigate the effects of charge structure parameters and explosive combinations on the internal overdriven detonation phenomena and the distribution of shock wave loads. It is found that the overdriven detonation phenomenon in the inner layer of composite charges increases the strength of the axial detonation wave,thereby enhancing the intensity of the primary end wave formed upon refraction into the air, which affects the distribution characteristics of the shock wave overpressure. Research has shown that increasing the thickness ratio and detonation velocity ratio of composite charges is beneficial for exacerbating the phenomenon of overdriven detonation, improving the primary end wave intensity and axial overpressure. This gain effect gradually weakens with the propagation of shock waves. When overdriven detonation occurs inside the composite charge, the detonation pressure first increases and then decreases. The Mach reflection pressure of the composite charge with a larger aspect ratio is attenuated to a greater extent. In addition, as the aspect ratio of the composite charge increases, the shock wave energy gradually flows from the axial direction to the radial direction. Therefore, as the aspect ratio of the composite charge increases, the primary end wave intensity and axial overpressure gradually decrease.展开更多
Detonation performance is crucial for evaluating the power of high explosives(HEs),and the equation of state(EOS)that accurately describes the high-temperature,high-pressure,and high-temperature,medium-pressure states...Detonation performance is crucial for evaluating the power of high explosives(HEs),and the equation of state(EOS)that accurately describes the high-temperature,high-pressure,and high-temperature,medium-pressure states of detonation products is key to assessing the damage efficiency of these energetic materials.This article examines the limitations of the VLW EOS in representing the thermodynamic states of explosive detonation gas products under high-temperature and medium-to high-pressure conditions.A new gas EOS for detonation products,called VHL(Virial-Han-Long),is proposed.The accuracy of VHL in describing gas states under high-temperature and medium-to high-pressure conditions is verified,and its performance in evaluating explosive detonation and working capabilities is explored.The results demonstrate that VHL exhibits high precision in calculating detonation performance.Subsequently,the detonation performance of three new HEs(ICM-101,ONC,and TNAZ)was calculated and compared to traditional HEs(TATB,CL-20,and HMX).The results indicate that ONC has superior detonation performance compared to the other explosives,while ICM-101 shows a detonation velocity similar to CL-20 but with slightly lower detonation pressure.The detonation characteristics of TNAZ are comparable to those of the standard HE HMX.From the perspective of products,considering the comprehensive work performance(mechanical work and detonation heat),both ONC and ICM-101demonstrate relatively superior performance.展开更多
Recent advancements have led to the synthesis of various new metal-containing explosives,particularly energetic metal-organic frameworks(EMOFs),which feature high-energy ligands within well-ordered crystalline structu...Recent advancements have led to the synthesis of various new metal-containing explosives,particularly energetic metal-organic frameworks(EMOFs),which feature high-energy ligands within well-ordered crystalline structures.These explosives exhibit significant advantages over traditional compounds,including higher density,greater heats of detonation,improved mechanical hardness,and excellent thermal stability.To effectively evaluate their detonation performance,it is crucial to have a reliable method for predicting detonation heat,velocity,and pressure.This study leverages experimental data and outputs from the leading commercial computer code to identify suitable decomposition pathways for different metal oxides,facilitating straightforward calculations for the detonation performance of alkali metal salts,and metal coordination compounds,along with EMOFs.The new model enhances predictive reliability for detonation velocities,aligning more closely with experimental results,as evi-denced by a root mean square error(RMSE)of 0.68 km/s compared to 1.12 km/s for existing methods.Furthermore,it accommodates a broader range of compounds,including those containing Sr,Cd,and Ag,and provides predictions for EMOFs that are more consistent with computer code outputs than previous predictive models.展开更多
With the increasing demand for secure infrastructure such as hydrogen refueling stations,chemical plants,and energy storage systems,the need for protective structures capable of withstanding close-in detonations has b...With the increasing demand for secure infrastructure such as hydrogen refueling stations,chemical plants,and energy storage systems,the need for protective structures capable of withstanding close-in detonations has become more critical.Existing design guidelines for protective walls(e.g.,UFC 3-340-02)primarily address mid-and far-field explosions,providing limited insights into near-field effects.Considering the effect of slight slopes(<40°)on reducing maximum reflected overpressure is deemed negligible.This study investigated the effectiveness of a reinforced concrete(RC)modular protection system(MPS)incorpo rating a diagonally tapered wall in attenuating re flected overpressures from closein detonations.Full-scale field experiments using a 51.3 kg TNT charge,representing the explosion energy of a typical hydrogen vessel rupture,demonstrated that a wall with a 7°slope significantly outperformed a vertical wall of equivalent concrete volume in terms of blast resistance.Observed structural responses included cracking,horizontal shear failure,and overturning.Complementary simulations using a validated computational fluid dynamics(CFD)model showed that the tapered wall reduced peak overpressure by 30%-40%compared to an equivalent vertical wall.This result highlights the potential of minor geometric modifications to enhance blast resilience.The tapered design effectively redirects incident blast waves,reducing localized damage while also conserving material,thus preserving modular benefits such as ease of transport and reusability.These findings suggest that diagonally tapered RC-based MPSs can offer a practical and resilient solution for industrial and military applications subject to near-field or sequential blast threats.展开更多
In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The e...In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The effects of the divergence, straight, and convergence isolators on the rotating detonation wave dynamics and the upstream oblique shock wave propagation mechanism are analyzed. The differences in the rotating detonation wave behaviors between ground and flight operations are clarified.The results indicate that the propagation regimes of the upstream oblique shock wave depend on the isolator configurations and operation conditions. With a divergence isolator, the airflow is accelerated throughout the isolator and divergence section, leading to a maximum Mach number(~1.8) before the normal shock. The total pressure loss reaches the largest, and the detonation pressure drops. The upstream oblique shock wave can be suppressed within the divergence section with the divergence isolator.However, for the straight and convergence isolators, the airflow in the isolator with a larger ψ_(1)(0.3 and0.4) can suffer from the disturbance of the upstream oblique shock wave. The critical incident angle is around 39° at ground operation conditions. The upstream oblique shock wave tends to be suppressed when the engine operates under flight operation conditions. The critical pressure ratio β_(cr0) is found to be able to help in distinguishing the propagation regimes of the upstream oblique shock wave. Slightly below or above the β_(cr0) can obtain different marginal propagation results. The high-speed airflow in the divergence section affects the fuel droplet penetration distance, which deteriorates the reactant mixing and the detonation area. Significant detonation velocity deficits are observed and the maximum velocity deficit reaches 26%. The results indicate the engine channel design should adopt different isolator configurations based on the purpose of total pressure loss or disturbance suppression. This study can provide useful guidance for the channel design of a more complete two-phase rotating detonation engine.展开更多
Predictions of extreme near-field blast wave for cylindrical charge is crucial for designing sympathetic detonation protection structures,yet the quantitative analysis of detonation products and shock wave field are s...Predictions of extreme near-field blast wave for cylindrical charge is crucial for designing sympathetic detonation protection structures,yet the quantitative analysis of detonation products and shock wave field are still insufficient.The present work conducted experiments and numerical simulations of nearfield explosion for kilogram scale cylindrical charge,and investigated the propagation and spatial distribution characteristics of incident and reflected blast waves.The results show that near-field reflected overpressure exhibits multi-peak structures,which are primarily governed by reflections of detonation products and shock wave.The reflected peak overpressure dominated by detonation products shows higher sensitivity to scaled distance.Meanwhile,the Rayleigh-Taylor instability(RTI)effect induces the evolutions of detonation products and shock wave interface from smooth to random microjets,increasing dispersion of secondary re flected peak overpressure.In free-field explosion,the incident peak overpressure exhibits a dual-peak structure,governed by the shock wave front and detonation products flowing past the gauge points.The incident peak overpressure dominated by detonation products is sensitive to orientations due to the charge structures.As the aspect ratio of charge increases from 0.6 to 8,the dominant radial azimuth angle region expands from 60°-90°to 30°-90°.An empirical model was developed to predict the spatial distributions of incident peak loads at arbitrary orientations for cylindrical charge with 0.6≤L/D≤8.0 and 0.06 m·kg^(-1/3)展开更多
The impact safety of explosive charges has been focused in these decades. The fragment impact is widely used to evaluate the response of explosive charges. In our work, the explosive detonation driving technique was u...The impact safety of explosive charges has been focused in these decades. The fragment impact is widely used to evaluate the response of explosive charges. In our work, the explosive detonation driving technique was used to generate a high velocity fragment with large mass. When the fragment masses are10 g, 16 g, 25 g, and 50 g, the highest velocity of fragments can reach 2400 m/s, 2100 m/s, 1900 m/s, and1400 m/s, respectively. The high velocity fragment with large mass was used to evaluate the safety of two kinds of CL-20 based explosive charges. The effects of the fragment mass and velocity were analyzed.Especially, the reaction extent was obtained based on visible phenomenon. The CL-20-based explosive charge containing Al had a higher safety level than that without Al. It was because Al had good ductility,and further improved the mechanical property of the material. Also, the numerical simulation was conducted to understand the reaction characteristics of the CL-20-based explosive charge. The results showed that as the fragment mass and velocity increased, the reaction became more violent.展开更多
The new CL-20(hexanitrohexaazaisowurtzitane)type aluminized explosives in the overdrive detonation(ODD)conditions of the core problem is how to accurately represent the state of the overdrive detonation products.To th...The new CL-20(hexanitrohexaazaisowurtzitane)type aluminized explosives in the overdrive detonation(ODD)conditions of the core problem is how to accurately represent the state of the overdrive detonation products.To this end,this paper is based on the impedance matching method to test the ODD conditions of CL-20 type aluminium explosive particle velocity.Calculated the interfacial pressure of the shock wave in different media.Determined the characteristic parameters of the reaction zone of the detonation of CL-20 aluminized explosives.Calibrated the parameters of the JoneseWilkinseLee(JWL)+γ equation for the detonation products(DPs).Revealed the effect of different DPs equation of state(EOS)on the Hugoniot pressure of ODD.The results indicate that when the content of aluminum powder ranges from 0%to 30%,the duration of the ODD reaction zone and the width of the detonation reaction zone of the CL-20-based aluminized explosive are directly proportional to the content of aluminum powder.The width of the detonation reaction zone is increased by 1.97 times to 2.7 times compared to that of the reaction zone without the addition of aluminum powder.However,the energy release efficiency of the detonation reaction zone is inversely proportional to the content of aluminum powder.When the aluminum powder content was held constant,the incorporation of AP caused a 25%reduction in the energy release efficiency of the detonation reaction zone.Compared with existing ODD state equations,the JWL +γ equation is superior in calibrating overpressure Hugoniot data and the isentropic expansion in the C-J state.The deviation between calculated pressure results and experimental measurements is within 6%.展开更多
Due to the strong unsteadiness of pulse detonation,large flow losses are generated when the detonation wave interacts with the turbine blades,resulting in low turbine efficiency.Considering that the flow losses are di...Due to the strong unsteadiness of pulse detonation,large flow losses are generated when the detonation wave interacts with the turbine blades,resulting in low turbine efficiency.Considering that the flow losses are dissipated into the gas as heat energy,some of them can be recycled during the expansion process in subsequent stages by the reheat effect,which should be helpful to improve the detonationdriven turbine efficiency.Taking this into account,this paper developed a numerical model of the detonation chamber coupled with a two-stage axial turbine,and a stoichiometric hydrogen-air mixture was used.The improvement in turbine efficiency attributable to the reheat effect was calculated by comparing the average efficiency of the stages with the efficiency of the two-stage turbine.The research indicated that the first stage was critical in suppressing the flow unsteadiness caused by pulse detonation,which stabilized the intake condition of the second stage and consequently allowed much of the flow losses from the first stage to be recycled,so that the efficiency of the two-stage turbine was improved.At a 95%confidence level,the efficiency improvement was stable at 4.5%—5.3%,demonstrating that the reheat effect is significant in improving the efficiency of the detonation-driven turbine.展开更多
Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This s...Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This study is based on developing a safer laser driven flyer plate prototype comprised of a laser initiator and a flyer plate subsystem that can be used with secondary explosives.System parameters were optimized to initiate the shock-to-detonation transition(SDT)of a secondary explosive based on the impact created by the flyer plate on the explosive surface.Rupture of the flyer was investigated at the mechanically weakened region located on the interface of these subsystems,where the product gases from the deflagration of the explosive provide the required energy.A bilayer energetic material was used,where the first layer consisted of a pyrotechnic component,zirconium potassium perchlorate(ZPP),for sustaining the ignition by the laser beam and the second layer consisted of an insensitive explosive,cyclotetramethylene-tetranitramine(HMX),for deflagration.A plexiglass interface was used to enfold the energetic material.The focal length of the laser beam from the diode was optimized to provide a homogeneous beam profile with maximum power at the surface of the ZPP.Closed bomb experiments were conducted in an internal volume of 10 cm^(3) for evaluation of performance.Dependency of the laser driven flyer plate system output on confinement,explosive density,and laser beam power were analyzed.Measurements using a high-speed camera resulted in a flyer velocity of 670±20 m/s that renders the prototype suitable as a laser detonator in applications,where controlled employment of explosives is critical.展开更多
The study of non-axisymmetric fuel dispersal and detonation can provide reference for the prevention of industrial cloud explosion accidents and the design of fuel air explosive(FAE).The concentration and detonation f...The study of non-axisymmetric fuel dispersal and detonation can provide reference for the prevention of industrial cloud explosion accidents and the design of fuel air explosive(FAE).The concentration and detonation fields of 85 kg cylindrical and fan-shaped fuel are investigated by experiments and numerical simulations.A dynamic model of the whole process for fuel dispersal and detonation is built.The concentration distribution of fuel is used as the initial condition to calculate the detonation stage,thus solving the initial value problem of detonation field.The phase and component changes of fuel cloud at different locations are compared.The fuel cloud is divided into directions of 0°,90°,135°and 180°.The results show that the maximum cloud radius is 20.94 m in 135°and the minimum is 12.04 m in 0°.The diameter of the detonation fireball is 53.6 m,and the peak temperature is 3455 K.The highest peak overpressure is 3.44 MPa in 0°and the lowest is 2.97 MPa in 135°.The proportion of liquid phase in 0°is22.90%,and the fuel loss is 11.8% and 9% higher than that in 135°and cylindrical charge,respectively.The stable propagation distance of blast wave in 135°is 42.50% longer than 0°and 28.37% longer than cylindrical charge.展开更多
The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine(RRDE),which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines,oblique detona...The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine(RRDE),which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines,oblique detonation engines,and rotating detonation engines.The RRDE organizes the processes of reactant compression,detonation combustion,and burned gas expansion in a single rotor,allowing it to achieve an ideal detonation cycle under a wide range of inlet Mach numbers,thus significantly improving the total pressure gain of the propulsion system.The feasibility and performance of RRDE are discussed through theoretical analysis and numerical simulations.The theoretical analysis indicates that the performance of the RRDE is mainly related to the inlet velocity,the rotor rim velocity,and the equivalence ratio of reactant.Increasing the inlet velocity leads to a decrease in the total pressure gain of the RRDE.Once the inlet velocity exceeds the critical value,the engine cannot achieve positive total pressure gain.Increasing the rim velocity can improve the total pressure gain and the thermodynamic cycle efficiency of RRDE.Increasing the equivalence ratio can also improve the thermodynamic cycle efficiency and enhance the total pressure gain at lower inlet velocities.While at higher inlet velocities,increasing the equivalence ratio may reduce the total pressure gain.Numerical simulations are also performed to analyze the detailed flow field structure in RRDE and its variations with the inlet parameters.The simulation results demonstrate that the detonation wave can stably stand in the RRDE and can adapt to the change of the inlet equivalence ratio within a certain range.This study provides the preliminary theoretical basis and design reference for the RRDE.展开更多
Shock wave focusing is an effective way to create a hot spot or a high-pressure and hightemperature region at a certain place,showing its unique usage in detonation initiation,which is beneficial for the development o...Shock wave focusing is an effective way to create a hot spot or a high-pressure and hightemperature region at a certain place,showing its unique usage in detonation initiation,which is beneficial for the development of detonation-based engines.The flame propagation behavior after the autoignition induced by shock wave focusing is crucial to the formation and self-sustaining of the detonation wave.In this study,wedge reflectors with two different angles(60°and 90°)and a planar reflector are employed,and the Mach number of incident shock waves ranging from 2.0 to 2.8 is utilized to trigger different flame propagation modes.Dynamic pressure transducers and the high-speed schlieren imaging system are both employed to investigate the shock-shock collision and ignition procedure.The results reveal a total of four flame propagation modes:deflagration,DDT(Deflagration-to-Detonation Transition),unsteady detonation,and direct detonation.The detonation wave formed in the DDT and unsteady detonation mode is only approximately 75%-85%of the Chapman-Jouguet(C-J)speed;meanwhile,the directly induced detonation wave speed is close to the C-J speed.Transverse waves,which are strong evidence for the existence of detonation waves,are discovered in experiments.The usage of wedge reflectors significantly reduces the initial pressure difference ratio needed for direct detonation ignition.We also provide a practical method for differentiating between detonation and deflagration modes,which involves contrasting the speed of the reflected shock wave with the speed of the theoretically nonreactive reflected shock wave.These findings should serve as a reference for the detonation initiation technique in advanced detonation propulsion engines.展开更多
In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such events.These pulsed X-rays can be captured using a satellite-borne X-ray detect...In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such events.These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission.To quantitatively analyze the effects of different satellite detection altitudes,burst heights,and transmission angles on the physical processes of X-ray transport and energy fluence,we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction.The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays.The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method.Our improved method reduces this error to within 10% under the same conditions,even reaching 1% in certain scenarios.Moreover,its computation time is 48,000 times faster than that of the Monte Carlo method.These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors,inverting nuclear detonation source terms,and assessing ionospheric effects.展开更多
Afterburning behind the detonation front of an aluminized explosive releases energy on the millisecond timescale,which prolong the release of detonation energy and the energy release at different stages also shows sig...Afterburning behind the detonation front of an aluminized explosive releases energy on the millisecond timescale,which prolong the release of detonation energy and the energy release at different stages also shows significant differences.However,at present,there are few effective methods for evaluating the energy release characteristics of the middle reaction stage of such explosives,which can have a duration of tens to hundreds of microseconds.The present work demonstrates an approach to assessing the midstage of an aluminized explosive detonation based on a water push test employing a high degree of confinement.In this method,the explosive is contained in a steel cylinder having one end closed that is installed at the bottom of a transparent water tank.Upon detonation,the gaseous products expand in one direction while forcing water ahead of them.The resulting underwater shock wave and the interface between the gas phase products and the water are tracked using an ultra-high-speed framing and streak camera.The shock wave velocity in water and the expansion work performed by the gaseous detonation products were calculated to assess the energy release characteristics of aluminized explosives such as CL-20 and RDX in the middle stage of the detonation reaction.During the middle stage of the detonation process of these aluminized explosives,the aluminum reaction reduced the attenuation of shock waves and increased the work performed by gas phase products.A higher aluminum content increased the energy output while the presence of oxidants slowed the energy release rate.This work demonstrates an effective means of evaluating the performance of aluminized explosives.展开更多
Insensitive explosive detonation has wide applications in compressing and driving inert materials,and thereby the interaction between detonation and inert materials has received more attention.In this paper,a two-dime...Insensitive explosive detonation has wide applications in compressing and driving inert materials,and thereby the interaction between detonation and inert materials has received more attention.In this paper,a two-dimensional numerical simulation based on the Euler multiphase flow framework is used to investigate the reflection behavior of the insensitive explosive detonation propagating around a cylinder.The results show that there is a critical incident angle,defined as transition angle for detonation propagating around the cylinder,below which the regular reflection(RR)on the cylinder surface is observed.When the incident angle is greater than the transition angle,RR changes to Mach reflection.This transition angle is larger than that obtained by polar curve theory and the change of incident angle is used to interpret above phenomenon.In addition,the influence of cylindrical radius and detonation reaction zone width on the reflection behavior is examined.As the cylindrical radius increases,the height of Mach stem increases while the transition angle decreases and gradually approaches the value in pole curve theory.Von Neumann reflection is observed when the reaction zone width is relatively small.This is because the energy release rate in the reaction zone is high for small reaction zone width,resulting in the formation of a series of compression waves near the cylindrical interface.展开更多
Computational simulations on structurally different detonation generator are carried out to study the phenomena,the mechanism and the gas dynamics characteristics of flame implosion and shock wave focusing.Two-dimensi...Computational simulations on structurally different detonation generator are carried out to study the phenomena,the mechanism and the gas dynamics characteristics of flame implosion and shock wave focusing.Two-dimensional axisymmetric and unsteady Navier-Stokes equations are numerically solved and detailed chemical reaction kinetics of hydrogen/air mixture is used.The simulation results show that the laminar flame generated by low energy spark in the jet flame burner is accelerated under the narrow channel,the jet flame impinging on the axis strengthens shock wave and the shock wave enhances flame acceleration.Under the function of multiple shock waves and flame,a number of hot spots appear between the wave and the surface.The spots enlarge rapidly,thus forming an over-drive detonation with high pressure,and then declining to stable detonation.Through calculation and analysis,the length of detonation initiation and stable detonation are obtained,thus providing the useful information for further experimental investigations.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U20A2069,62376234 and 123B2037)the Advanced Aero-Power Innovation Workstation,China(No.HKCX2024-01-017)。
文摘The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.
基金support provided by the National Natural Science Foundation of China(Grant No.12102405)the Presidential Foundation of CAEP(Grant No.YZJJZQ2023008).
文摘This study investigates the paradoxical detonation behavior of TKX-50,a nitrogen-rich energetic material,exhibiting higher detonation velocities but lower metal acceleration ability compared to HMX.Through experimental measurements and theoretical calculations,we propose a novel three-factor competition mechanism to explain this phenomenon.TKX-50-based PBX formulations achieved detonation velocities up to 9100 m/s,surpassing HMX-based counterparts.However,cylinder expansion tests revealed a 15%reduction in metal acceleration ability.Thermochemical measurements showed lower detonation heat for TKX-50(4900 J/g)versus HMX(5645 J/g).Our mechanism involves:(1)compositional effects prevailing at high pressures;(2)Energy release becoming essential as pressure drops;(3)Pressure-dependent product composition evolution functioning at low pressure.VLW code calculations unveiled a"crossover"in Hugoniot curves,lending support to this mechanism.This study furnishes a new framework for comprehending the performance of nitrogen-rich energetic materials,with significant implications for the design and optimization of future high-energy density materials.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.2682024GF019)。
文摘Excellent detonation performances and low sensitivity are prerequisites for the deployment of energetic materials.Exploring the underlying factors that affect impact sensitivity and detonation performances as well as exploring how to obtain materials with desired properties remains a long-term challenge.Machine learning with its ability to solve complex tasks and perform robust data processing can reveal the relationship between performance and descriptive indicators,potentially accelerating the development process of energetic materials.In this background,impact sensitivity,detonation performances,and 28 physicochemical parameters for 222 energetic materials from density functional theory calculations and published literature were sorted out.Four machine learning algorithms were employed to predict various properties of energetic materials,including impact sensitivity,detonation velocity,detonation pressure,and Gurney energy.Analysis of Pearson coefficients and feature importance showed that the heat of explosion,oxygen balance,decomposition products,and HOMO energy levels have a strong correlation with the impact sensitivity of energetic materials.Oxygen balance,decomposition products,and density have a strong correlation with detonation performances.Utilizing impact sensitivity of 2,3,4-trinitrotoluene and the detonation performances of 2,4,6-trinitrobenzene-1,3,5-triamine as the benchmark,the analysis of feature importance rankings and statistical data revealed the optimal range of key features balancing impact sensitivity and detonation performances:oxygen balance values should be between-40%and-30%,density should range from 1.66 to 1.72 g/cm^(3),HOMO energy levels should be between-6.34 and-6.31 eV,and lipophilicity should be between-1.0 and 0.1,4.49 and 5.59.These findings not only offer important insights into the impact sensitivity and detonation performances of energetic materials,but also provide a theoretical guidance paradigm for the design and development of new energetic materials with optimal detonation performances and reduced sensitivity.
基金funded by the National Natural Science Foundation of China(Grant No. 12302437)Jiangsu Provincial Natural Science Foundation (Grant No.SBK2023045424)。
文摘To explore the design criteria for composite charges and reveal the intrinsic relationship between the detonation wave propagation in composite charges and the overall energy distribution of shock waves,this study analyzes the propagation and interaction processes of detonation waves in composite charges with different structural dimensions and explosive combinations. It also investigates the spatial distribution characteristics of the resulting shock wave loads. Based on dimensional analysis theory, a theoretical analysis of the shock wave overpressure distribution in free air fields is conducted. Utilizing the derived dimensionless function relationships, the hydrocode AUTODYN is employed to investigate the effects of charge structure parameters and explosive combinations on the internal overdriven detonation phenomena and the distribution of shock wave loads. It is found that the overdriven detonation phenomenon in the inner layer of composite charges increases the strength of the axial detonation wave,thereby enhancing the intensity of the primary end wave formed upon refraction into the air, which affects the distribution characteristics of the shock wave overpressure. Research has shown that increasing the thickness ratio and detonation velocity ratio of composite charges is beneficial for exacerbating the phenomenon of overdriven detonation, improving the primary end wave intensity and axial overpressure. This gain effect gradually weakens with the propagation of shock waves. When overdriven detonation occurs inside the composite charge, the detonation pressure first increases and then decreases. The Mach reflection pressure of the composite charge with a larger aspect ratio is attenuated to a greater extent. In addition, as the aspect ratio of the composite charge increases, the shock wave energy gradually flows from the axial direction to the radial direction. Therefore, as the aspect ratio of the composite charge increases, the primary end wave intensity and axial overpressure gradually decrease.
基金supported by the National Natural Science Foundation of China(Gant Nos.11372291 and 11902298)。
文摘Detonation performance is crucial for evaluating the power of high explosives(HEs),and the equation of state(EOS)that accurately describes the high-temperature,high-pressure,and high-temperature,medium-pressure states of detonation products is key to assessing the damage efficiency of these energetic materials.This article examines the limitations of the VLW EOS in representing the thermodynamic states of explosive detonation gas products under high-temperature and medium-to high-pressure conditions.A new gas EOS for detonation products,called VHL(Virial-Han-Long),is proposed.The accuracy of VHL in describing gas states under high-temperature and medium-to high-pressure conditions is verified,and its performance in evaluating explosive detonation and working capabilities is explored.The results demonstrate that VHL exhibits high precision in calculating detonation performance.Subsequently,the detonation performance of three new HEs(ICM-101,ONC,and TNAZ)was calculated and compared to traditional HEs(TATB,CL-20,and HMX).The results indicate that ONC has superior detonation performance compared to the other explosives,while ICM-101 shows a detonation velocity similar to CL-20 but with slightly lower detonation pressure.The detonation characteristics of TNAZ are comparable to those of the standard HE HMX.From the perspective of products,considering the comprehensive work performance(mechanical work and detonation heat),both ONC and ICM-101demonstrate relatively superior performance.
基金the research committee at Malek Ashtar University of Technology (MUT) for their invaluable support of this project
文摘Recent advancements have led to the synthesis of various new metal-containing explosives,particularly energetic metal-organic frameworks(EMOFs),which feature high-energy ligands within well-ordered crystalline structures.These explosives exhibit significant advantages over traditional compounds,including higher density,greater heats of detonation,improved mechanical hardness,and excellent thermal stability.To effectively evaluate their detonation performance,it is crucial to have a reliable method for predicting detonation heat,velocity,and pressure.This study leverages experimental data and outputs from the leading commercial computer code to identify suitable decomposition pathways for different metal oxides,facilitating straightforward calculations for the detonation performance of alkali metal salts,and metal coordination compounds,along with EMOFs.The new model enhances predictive reliability for detonation velocities,aligning more closely with experimental results,as evi-denced by a root mean square error(RMSE)of 0.68 km/s compared to 1.12 km/s for existing methods.Furthermore,it accommodates a broader range of compounds,including those containing Sr,Cd,and Ag,and provides predictions for EMOFs that are more consistent with computer code outputs than previous predictive models.
基金supported by the Dong-A University of the Republic of Korea research fund。
文摘With the increasing demand for secure infrastructure such as hydrogen refueling stations,chemical plants,and energy storage systems,the need for protective structures capable of withstanding close-in detonations has become more critical.Existing design guidelines for protective walls(e.g.,UFC 3-340-02)primarily address mid-and far-field explosions,providing limited insights into near-field effects.Considering the effect of slight slopes(<40°)on reducing maximum reflected overpressure is deemed negligible.This study investigated the effectiveness of a reinforced concrete(RC)modular protection system(MPS)incorpo rating a diagonally tapered wall in attenuating re flected overpressures from closein detonations.Full-scale field experiments using a 51.3 kg TNT charge,representing the explosion energy of a typical hydrogen vessel rupture,demonstrated that a wall with a 7°slope significantly outperformed a vertical wall of equivalent concrete volume in terms of blast resistance.Observed structural responses included cracking,horizontal shear failure,and overturning.Complementary simulations using a validated computational fluid dynamics(CFD)model showed that the tapered wall reduced peak overpressure by 30%-40%compared to an equivalent vertical wall.This result highlights the potential of minor geometric modifications to enhance blast resilience.The tapered design effectively redirects incident blast waves,reducing localized damage while also conserving material,thus preserving modular benefits such as ease of transport and reusability.These findings suggest that diagonally tapered RC-based MPSs can offer a practical and resilient solution for industrial and military applications subject to near-field or sequential blast threats.
基金supported by the National Natural Science Foundation of China (Grant No. 12202204)the Natural Science Foundation of Jiangsu Province (Grant No. BK20220953)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Science and Technology Association's Young Talent Nurturing Program of Jiangsu Province (Grant No. JSTJ-2024-004)
文摘In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The effects of the divergence, straight, and convergence isolators on the rotating detonation wave dynamics and the upstream oblique shock wave propagation mechanism are analyzed. The differences in the rotating detonation wave behaviors between ground and flight operations are clarified.The results indicate that the propagation regimes of the upstream oblique shock wave depend on the isolator configurations and operation conditions. With a divergence isolator, the airflow is accelerated throughout the isolator and divergence section, leading to a maximum Mach number(~1.8) before the normal shock. The total pressure loss reaches the largest, and the detonation pressure drops. The upstream oblique shock wave can be suppressed within the divergence section with the divergence isolator.However, for the straight and convergence isolators, the airflow in the isolator with a larger ψ_(1)(0.3 and0.4) can suffer from the disturbance of the upstream oblique shock wave. The critical incident angle is around 39° at ground operation conditions. The upstream oblique shock wave tends to be suppressed when the engine operates under flight operation conditions. The critical pressure ratio β_(cr0) is found to be able to help in distinguishing the propagation regimes of the upstream oblique shock wave. Slightly below or above the β_(cr0) can obtain different marginal propagation results. The high-speed airflow in the divergence section affects the fuel droplet penetration distance, which deteriorates the reactant mixing and the detonation area. Significant detonation velocity deficits are observed and the maximum velocity deficit reaches 26%. The results indicate the engine channel design should adopt different isolator configurations based on the purpose of total pressure loss or disturbance suppression. This study can provide useful guidance for the channel design of a more complete two-phase rotating detonation engine.
基金supported by the National Natural Science Foundation of China(No.12172051,12172050,12141201,and 12221002)。
文摘Predictions of extreme near-field blast wave for cylindrical charge is crucial for designing sympathetic detonation protection structures,yet the quantitative analysis of detonation products and shock wave field are still insufficient.The present work conducted experiments and numerical simulations of nearfield explosion for kilogram scale cylindrical charge,and investigated the propagation and spatial distribution characteristics of incident and reflected blast waves.The results show that near-field reflected overpressure exhibits multi-peak structures,which are primarily governed by reflections of detonation products and shock wave.The reflected peak overpressure dominated by detonation products shows higher sensitivity to scaled distance.Meanwhile,the Rayleigh-Taylor instability(RTI)effect induces the evolutions of detonation products and shock wave interface from smooth to random microjets,increasing dispersion of secondary re flected peak overpressure.In free-field explosion,the incident peak overpressure exhibits a dual-peak structure,governed by the shock wave front and detonation products flowing past the gauge points.The incident peak overpressure dominated by detonation products is sensitive to orientations due to the charge structures.As the aspect ratio of charge increases from 0.6 to 8,the dominant radial azimuth angle region expands from 60°-90°to 30°-90°.An empirical model was developed to predict the spatial distributions of incident peak loads at arbitrary orientations for cylindrical charge with 0.6≤L/D≤8.0 and 0.06 m·kg^(-1/3)
文摘The impact safety of explosive charges has been focused in these decades. The fragment impact is widely used to evaluate the response of explosive charges. In our work, the explosive detonation driving technique was used to generate a high velocity fragment with large mass. When the fragment masses are10 g, 16 g, 25 g, and 50 g, the highest velocity of fragments can reach 2400 m/s, 2100 m/s, 1900 m/s, and1400 m/s, respectively. The high velocity fragment with large mass was used to evaluate the safety of two kinds of CL-20 based explosive charges. The effects of the fragment mass and velocity were analyzed.Especially, the reaction extent was obtained based on visible phenomenon. The CL-20-based explosive charge containing Al had a higher safety level than that without Al. It was because Al had good ductility,and further improved the mechanical property of the material. Also, the numerical simulation was conducted to understand the reaction characteristics of the CL-20-based explosive charge. The results showed that as the fragment mass and velocity increased, the reaction became more violent.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11872120,12102050)Key Laboratory of Explosion Science and Technology(Grant No.QNKT22-01).
文摘The new CL-20(hexanitrohexaazaisowurtzitane)type aluminized explosives in the overdrive detonation(ODD)conditions of the core problem is how to accurately represent the state of the overdrive detonation products.To this end,this paper is based on the impedance matching method to test the ODD conditions of CL-20 type aluminium explosive particle velocity.Calculated the interfacial pressure of the shock wave in different media.Determined the characteristic parameters of the reaction zone of the detonation of CL-20 aluminized explosives.Calibrated the parameters of the JoneseWilkinseLee(JWL)+γ equation for the detonation products(DPs).Revealed the effect of different DPs equation of state(EOS)on the Hugoniot pressure of ODD.The results indicate that when the content of aluminum powder ranges from 0%to 30%,the duration of the ODD reaction zone and the width of the detonation reaction zone of the CL-20-based aluminized explosive are directly proportional to the content of aluminum powder.The width of the detonation reaction zone is increased by 1.97 times to 2.7 times compared to that of the reaction zone without the addition of aluminum powder.However,the energy release efficiency of the detonation reaction zone is inversely proportional to the content of aluminum powder.When the aluminum powder content was held constant,the incorporation of AP caused a 25%reduction in the energy release efficiency of the detonation reaction zone.Compared with existing ODD state equations,the JWL +γ equation is superior in calibrating overpressure Hugoniot data and the isentropic expansion in the C-J state.The deviation between calculated pressure results and experimental measurements is within 6%.
基金financially supported by the National Natural Science Foundation of China through Grant Nos.12372338 and U2241272the Natural Science Foundation of Shaanxi Province of China through Grant Nos.2023-JC-YB-352 and 2022JZ-20+1 种基金the Guangdong Basic and Applied Basic Research Foundation through Grant No.2023A1515011663the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University through Grant No.PF2023010。
文摘Due to the strong unsteadiness of pulse detonation,large flow losses are generated when the detonation wave interacts with the turbine blades,resulting in low turbine efficiency.Considering that the flow losses are dissipated into the gas as heat energy,some of them can be recycled during the expansion process in subsequent stages by the reheat effect,which should be helpful to improve the detonationdriven turbine efficiency.Taking this into account,this paper developed a numerical model of the detonation chamber coupled with a two-stage axial turbine,and a stoichiometric hydrogen-air mixture was used.The improvement in turbine efficiency attributable to the reheat effect was calculated by comparing the average efficiency of the stages with the efficiency of the two-stage turbine.The research indicated that the first stage was critical in suppressing the flow unsteadiness caused by pulse detonation,which stabilized the intake condition of the second stage and consequently allowed much of the flow losses from the first stage to be recycled,so that the efficiency of the two-stage turbine was improved.At a 95%confidence level,the efficiency improvement was stable at 4.5%—5.3%,demonstrating that the reheat effect is significant in improving the efficiency of the detonation-driven turbine.
文摘Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This study is based on developing a safer laser driven flyer plate prototype comprised of a laser initiator and a flyer plate subsystem that can be used with secondary explosives.System parameters were optimized to initiate the shock-to-detonation transition(SDT)of a secondary explosive based on the impact created by the flyer plate on the explosive surface.Rupture of the flyer was investigated at the mechanically weakened region located on the interface of these subsystems,where the product gases from the deflagration of the explosive provide the required energy.A bilayer energetic material was used,where the first layer consisted of a pyrotechnic component,zirconium potassium perchlorate(ZPP),for sustaining the ignition by the laser beam and the second layer consisted of an insensitive explosive,cyclotetramethylene-tetranitramine(HMX),for deflagration.A plexiglass interface was used to enfold the energetic material.The focal length of the laser beam from the diode was optimized to provide a homogeneous beam profile with maximum power at the surface of the ZPP.Closed bomb experiments were conducted in an internal volume of 10 cm^(3) for evaluation of performance.Dependency of the laser driven flyer plate system output on confinement,explosive density,and laser beam power were analyzed.Measurements using a high-speed camera resulted in a flyer velocity of 670±20 m/s that renders the prototype suitable as a laser detonator in applications,where controlled employment of explosives is critical.
基金supported by the National Key Research and Development Program of China (Grant No.2021YFC3001204)。
文摘The study of non-axisymmetric fuel dispersal and detonation can provide reference for the prevention of industrial cloud explosion accidents and the design of fuel air explosive(FAE).The concentration and detonation fields of 85 kg cylindrical and fan-shaped fuel are investigated by experiments and numerical simulations.A dynamic model of the whole process for fuel dispersal and detonation is built.The concentration distribution of fuel is used as the initial condition to calculate the detonation stage,thus solving the initial value problem of detonation field.The phase and component changes of fuel cloud at different locations are compared.The fuel cloud is divided into directions of 0°,90°,135°and 180°.The results show that the maximum cloud radius is 20.94 m in 135°and the minimum is 12.04 m in 0°.The diameter of the detonation fireball is 53.6 m,and the peak temperature is 3455 K.The highest peak overpressure is 3.44 MPa in 0°and the lowest is 2.97 MPa in 135°.The proportion of liquid phase in 0°is22.90%,and the fuel loss is 11.8% and 9% higher than that in 135°and cylindrical charge,respectively.The stable propagation distance of blast wave in 135°is 42.50% longer than 0°and 28.37% longer than cylindrical charge.
基金support from the National Natural Science Foundation of China(No.52306152)the China Postdoctoral Science Foundation(No.2023M731912)。
文摘The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine(RRDE),which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines,oblique detonation engines,and rotating detonation engines.The RRDE organizes the processes of reactant compression,detonation combustion,and burned gas expansion in a single rotor,allowing it to achieve an ideal detonation cycle under a wide range of inlet Mach numbers,thus significantly improving the total pressure gain of the propulsion system.The feasibility and performance of RRDE are discussed through theoretical analysis and numerical simulations.The theoretical analysis indicates that the performance of the RRDE is mainly related to the inlet velocity,the rotor rim velocity,and the equivalence ratio of reactant.Increasing the inlet velocity leads to a decrease in the total pressure gain of the RRDE.Once the inlet velocity exceeds the critical value,the engine cannot achieve positive total pressure gain.Increasing the rim velocity can improve the total pressure gain and the thermodynamic cycle efficiency of RRDE.Increasing the equivalence ratio can also improve the thermodynamic cycle efficiency and enhance the total pressure gain at lower inlet velocities.While at higher inlet velocities,increasing the equivalence ratio may reduce the total pressure gain.Numerical simulations are also performed to analyze the detailed flow field structure in RRDE and its variations with the inlet parameters.The simulation results demonstrate that the detonation wave can stably stand in the RRDE and can adapt to the change of the inlet equivalence ratio within a certain range.This study provides the preliminary theoretical basis and design reference for the RRDE.
基金the financial support from the National Natural Science Foundation of China(No.12272234)the Innovation Program of Shanghai Municipal Education Commission,China(No.2023KEJI05-75)the Shanghai Science and Technology Planning Project,China(No.22190711500)。
文摘Shock wave focusing is an effective way to create a hot spot or a high-pressure and hightemperature region at a certain place,showing its unique usage in detonation initiation,which is beneficial for the development of detonation-based engines.The flame propagation behavior after the autoignition induced by shock wave focusing is crucial to the formation and self-sustaining of the detonation wave.In this study,wedge reflectors with two different angles(60°and 90°)and a planar reflector are employed,and the Mach number of incident shock waves ranging from 2.0 to 2.8 is utilized to trigger different flame propagation modes.Dynamic pressure transducers and the high-speed schlieren imaging system are both employed to investigate the shock-shock collision and ignition procedure.The results reveal a total of four flame propagation modes:deflagration,DDT(Deflagration-to-Detonation Transition),unsteady detonation,and direct detonation.The detonation wave formed in the DDT and unsteady detonation mode is only approximately 75%-85%of the Chapman-Jouguet(C-J)speed;meanwhile,the directly induced detonation wave speed is close to the C-J speed.Transverse waves,which are strong evidence for the existence of detonation waves,are discovered in experiments.The usage of wedge reflectors significantly reduces the initial pressure difference ratio needed for direct detonation ignition.We also provide a practical method for differentiating between detonation and deflagration modes,which involves contrasting the speed of the reflected shock wave with the speed of the theoretically nonreactive reflected shock wave.These findings should serve as a reference for the detonation initiation technique in advanced detonation propulsion engines.
文摘In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such events.These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission.To quantitatively analyze the effects of different satellite detection altitudes,burst heights,and transmission angles on the physical processes of X-ray transport and energy fluence,we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction.The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays.The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method.Our improved method reduces this error to within 10% under the same conditions,even reaching 1% in certain scenarios.Moreover,its computation time is 48,000 times faster than that of the Monte Carlo method.These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors,inverting nuclear detonation source terms,and assessing ionospheric effects.
基金supported by the National Natural Science Foundation of China(Grant No.11832006)。
文摘Afterburning behind the detonation front of an aluminized explosive releases energy on the millisecond timescale,which prolong the release of detonation energy and the energy release at different stages also shows significant differences.However,at present,there are few effective methods for evaluating the energy release characteristics of the middle reaction stage of such explosives,which can have a duration of tens to hundreds of microseconds.The present work demonstrates an approach to assessing the midstage of an aluminized explosive detonation based on a water push test employing a high degree of confinement.In this method,the explosive is contained in a steel cylinder having one end closed that is installed at the bottom of a transparent water tank.Upon detonation,the gaseous products expand in one direction while forcing water ahead of them.The resulting underwater shock wave and the interface between the gas phase products and the water are tracked using an ultra-high-speed framing and streak camera.The shock wave velocity in water and the expansion work performed by the gaseous detonation products were calculated to assess the energy release characteristics of aluminized explosives such as CL-20 and RDX in the middle stage of the detonation reaction.During the middle stage of the detonation process of these aluminized explosives,the aluminum reaction reduced the attenuation of shock waves and increased the work performed by gas phase products.A higher aluminum content increased the energy output while the presence of oxidants slowed the energy release rate.This work demonstrates an effective means of evaluating the performance of aluminized explosives.
文摘Insensitive explosive detonation has wide applications in compressing and driving inert materials,and thereby the interaction between detonation and inert materials has received more attention.In this paper,a two-dimensional numerical simulation based on the Euler multiphase flow framework is used to investigate the reflection behavior of the insensitive explosive detonation propagating around a cylinder.The results show that there is a critical incident angle,defined as transition angle for detonation propagating around the cylinder,below which the regular reflection(RR)on the cylinder surface is observed.When the incident angle is greater than the transition angle,RR changes to Mach reflection.This transition angle is larger than that obtained by polar curve theory and the change of incident angle is used to interpret above phenomenon.In addition,the influence of cylindrical radius and detonation reaction zone width on the reflection behavior is examined.As the cylindrical radius increases,the height of Mach stem increases while the transition angle decreases and gradually approaches the value in pole curve theory.Von Neumann reflection is observed when the reaction zone width is relatively small.This is because the energy release rate in the reaction zone is high for small reaction zone width,resulting in the formation of a series of compression waves near the cylindrical interface.
文摘Computational simulations on structurally different detonation generator are carried out to study the phenomena,the mechanism and the gas dynamics characteristics of flame implosion and shock wave focusing.Two-dimensional axisymmetric and unsteady Navier-Stokes equations are numerically solved and detailed chemical reaction kinetics of hydrogen/air mixture is used.The simulation results show that the laminar flame generated by low energy spark in the jet flame burner is accelerated under the narrow channel,the jet flame impinging on the axis strengthens shock wave and the shock wave enhances flame acceleration.Under the function of multiple shock waves and flame,a number of hot spots appear between the wave and the surface.The spots enlarge rapidly,thus forming an over-drive detonation with high pressure,and then declining to stable detonation.Through calculation and analysis,the length of detonation initiation and stable detonation are obtained,thus providing the useful information for further experimental investigations.
