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 paper,we apply high-order finite difference(FD)schemes for multispecies and multireaction detonations(MMD).In MMD,the density and pressure are positive and the mass fraction of the ith species in the chemical ...In this paper,we apply high-order finite difference(FD)schemes for multispecies and multireaction detonations(MMD).In MMD,the density and pressure are positive and the mass fraction of the ith species in the chemical reaction,say zi,is between 0 and 1,withΣz_(i)=1.Due to the lack of maximum-principle,most of the previous bound-preserving technique cannot be applied directly.To preserve those bounds,we will use the positivity-preserving technique to all the zi'is and enforceΣz_(i)=1 by constructing conservative schemes,thanks to conservative time integrations and consistent numerical fluxes in the system.Moreover,detonation is an extreme singular mode of flame propagation in premixed gas,and the model contains a significant stiff source.It is well known that for hyperbolic equations with stiff source,the transition points in the numerical approximations near the shocks may trigger spurious shock speed,leading to wrong shock position.Intuitively,the high-order weighted essentially non-oscillatory(WENO)scheme,which can suppress oscillations near the discontinuities,would be a good choice for spatial discretization.However,with the nonlinear weights,the numerical fluxes are no longer“consistent”,leading to nonconservative numerical schemes and the bound-preserving technique does not work.Numerical experiments demonstrate that,without further numerical techniques such as subcell resolutions,the conservative FD method with linear weights can yield better numerical approximations than the nonconservative WENO scheme.展开更多
The cell size variation in overdriven gaseous detonations is studied in hydrogen/oxygen and acetylene/oxygen mixtures.The local self-similarity of Mach reflection of detonations on the wedge in the far field renders t...The cell size variation in overdriven gaseous detonations is studied in hydrogen/oxygen and acetylene/oxygen mixtures.The local self-similarity of Mach reflection of detonations on the wedge in the far field renders the presence of a steady overdriven Mach stem to be possible.The study focuses on the cell size change of overdriven Mach stem on the wedge surface other than on the sidewall.The detonation cell pattern on the wedge surface has a complicated process of three-stage pattern,i.e.,the cells decreasing from large to small size,and then increasing asymptotically to a medium size and keeping constant.The cell size ratio with increasing the degree of overdrive is also examined.It is found that the ratio decays as the degree of overdrive increases.However,as the wedge angle increases to a critical value,finer cells are not created on the smoke foils.Ng’s model used to predict the cell size is also found to be valid only for detonations with relative large instability parameters,but presents large errors for highly overdriven detonations with low instability.A modification to Ng’s model is proposed based on the experimental results.展开更多
The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism, The numerical results demonstrate that as the radius of the curvatur...The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism, The numerical results demonstrate that as the radius of the curvature decreases, detonation fails near the inner wall due to the strong expansion effect. As the radius of the curvature increases, the detonation front near the inner wall can sustain an underdriven detonation. In the case where deto- nation fails, a transverse detonation downstream forms and re-initiates the quenched detonation as it propagates toward the inner wall. Two kinds of propagation modes exist as the detonation is propagating in the curved channel. One is that the detonation fails first, and then a following transverse detonation initiates the quenched detonation and this process repeats itself. The other one is that without detonation failure and re-initiation, a steady detonation exists which consists of an underdriven detonation front near the inner wall subject to the diffraction and an overdriven detonation near the outer wall subject to the compression.展开更多
The direct initiation of detonations in one-dimensional （1D） and two-dimensional （2D） cylindrical geometries is investigated through numerical simulations. In comparison of 1D and 2D simulations, it is found that ...The direct initiation of detonations in one-dimensional （1D） and two-dimensional （2D） cylindrical geometries is investigated through numerical simulations. In comparison of 1D and 2D simulations, it is found that cellular instability has a negative effect on the 2D initiation and makes it more difficult to initiate a sustaining 2D cylindrical detonation. This effect associates closely with the activation energy. For the lower activation energy, the 2D initiation of cylindrical detonations can be achieved through a subcritical initiation way. With increasing the activation energy, the 2D cylindrical detonation has increased difficulty in its initiation due to the presence of unreacted pockets behind the detonation front and usually requires rather larger source energy.展开更多
The dynamics of frontal and transverse shocks in gaseous detonation waves is a complex phenomenon bringing many difficulties to both numerical and experimental research.Advanced laser-optical visualization of detonati...The dynamics of frontal and transverse shocks in gaseous detonation waves is a complex phenomenon bringing many difficulties to both numerical and experimental research.Advanced laser-optical visualization of detonation structure may provide certain information of its reactive front,but the corresponding lead shock needs to be reconstructed building the complete flow field.Using the multi-layer perceptron(MLP)approach,we propose a shock front reconstruction method which can predict evolution of the lead shock wavefront from the state of the reactive front.The method is verified through the numerical results of one-and two-dimensional unstable detonations based on the reactive Euler equations with a one-step irreversible chemical reaction model.Results show that the accuracy of the proposed method depends on the activation energy of the reactive mixture,which influences prominently the cellular detonation instability and hence,the distortion of the lead shock surface.To select the input variables for training and evaluate their influence on the effectiveness of the proposed method,five groups,one with six variables,and the other with four variables,are tested and analyzed in the MLP model.The trained MLP is tested in the cases with different activation energies,demonstrates the inspiring generalization capability.This paper offers a universal framework for predicting detonation frontal evolution and provides a novel way to interpret numerical and experimental results of detonation waves.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
Multi-dimensional direct numerical simulations （DNS） of astrophysical detonations in degenerate matter have revealed that the nuclear burning is typically characterized by cellular structure caused by transverse ins...Multi-dimensional direct numerical simulations （DNS） of astrophysical detonations in degenerate matter have revealed that the nuclear burning is typically characterized by cellular structure caused by transverse instabilities in the detonation front. Type Ia supernova modelers often use one- dimensional DNS of detonations as inputs or constraints for their whole star simulations. While these one-dimensional studies are useful tools, the true nature of the detonation is multi-dimensional. The multi-dimensional structure of the burning influences the speed, stability, and the composition of the detonation and its burning products, and therefore, could have an impact on the spectra of Type Ia supernovae. Considerable effort has been expended modeling Type Ia supernovae at densities above 1 ~ 107 g.cm-3 where the complexities of turbulent burning dominate the flame propagation. How- ever, most full star models turn the nuclear burning schemes off when the density falls below 1 ~ 107 g.cm-3 and distributed burning begins. The deflagration to detonation transition （DDT） is believed to occur at just these densities and consequently they are the densities important for studying the properties of the subsequent detonation. This work will review the status of DNS studies of detona- tions and their possible implications for Type Ia supernova models. It will cover the development of Detonation theory from the first simple Chapman-Jouguet （C J） detonation models to the current models based on the time-dependent, compressible, reactive flow Euler equations of fluid dynamics.展开更多
To elucidate the dispersion and explosion characteristics of multi-metal powder and liquid composite fuel formulations,high-energy metal powders(aluminum(Al),boron(B),and magnesium hydride(MgH_(2)))are incorporated in...To elucidate the dispersion and explosion characteristics of multi-metal powder and liquid composite fuel formulations,high-energy metal powders(aluminum(Al),boron(B),and magnesium hydride(MgH_(2)))are incorporated into a liquid fuel primarily composed of diethyl ether(DEE)and isopropyl nitrate(IPN).The explosion characteristics of different solid-liquid fuel-air-explosive(FAE)under unconfined conditions are investigated using a high-speed camera,infrared thermal imaging,and a pressure measurement system.Results demonstrate that high-energy metal powders significantly enhance detonation energy dissipation,with aluminum exhibiting the most pronounced effect.Fuel 5#(45.4 wt%DEE,9.2 wt%IPN,29.5 wt%Al,9.1 wt%B,6.8 wt%MgH_(2))exhibits superior explosion performance,achieving higher values of overpressure,impulse,and thermal radiation damage during the detonation stage compared to other fuels.However,Fuel 5#also displays faster decay rates,attributed to accelerated heat release rates induced by B and MgH_(2)powders.This study reveals that different metal powders in solid-liquid FAE exhibit distinct enhancements in explosion performance,providing critical insights for optimizing composite fuel design.展开更多
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
Rectangular explosive charges are usually used in military or civilian explosive transportation and storage.The effects of shape parameters and detonation positions on the peak overpressure and maximum impulse of blas...Rectangular explosive charges are usually used in military or civilian explosive transportation and storage.The effects of shape parameters and detonation positions on the peak overpressure and maximum impulse of blasts lack comprehensive investigation,which is significant for the design of blast-resistant structures.In this paper,the side-length ratio of the rectangle,orientation,and detonation position of the charge are chosen as controlling parameters to investigate their influence on blast loads in the scaled distances of the gauges ranging from 0.63 to 10.54 m/kg^(1/3) with well validated 3D numerical simulations.The results show that there is a large difference in the near-field spatial distribution of the blast load of the rectangular charge;if the blast load of the rectangular charge is simply evaluated with the spherical charge,the maximum peak overpressure(maximum impulse)will be underestimated by a factor of 7.46(4.84).This must be taken seriously by blast-resistant structure designers.With the increase in the scaled distance,when the critical scaled distance is greater than 6.32(7.38)m/kg^(1/3),the influence of the charge shape on the maximum peak overpressure(maximum impulse)of the spatial blast load can be ignored.In general,the impact of detonation of the charge at the end on the maximum peak overpressure is greater compared with central detonation,but for the impact of the maximum impulse,it is necessary to pay attention to the side-length ratio of the rectangular charge and the specific detonation position on the end face.Furthermore,the structural response of steel plates placed at different azimuths under the blast load of a rectangular charge is preliminarily analyzed,and the results show that the deformation and energy of the plates are consistent with the distribution of the blast load.These analysis results provide a reference for the explosion protection design in near-field air explosions.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
In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and compreh...In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and comprehensive understanding of the failure mechanisms of electronic detonators subjected to impact loading is of great significance to the reliability design and field safety use of electronic detonators.The spatial distribution characteristics and failure modes of misfired electronic detonators under different application scenarios are statistically analysed.The results show that under high impact loads,electronic detonators will experience failure phenomena such as rupture of the fuse head,fracture of the bridge wire,falling off of the solder joint,chip module damage and insufficient initiation energy after deformation.The lack of impact resistance is the primary cause of misfire of electronic detonators.Combined with the underwater impact resistance test and the impact load test in the adjacent blasthole on site,the formulas of the impact failure probability of the electronic detonator under different stress‒strength distribution curves are deduced.The test and evaluation method of the impact resistance of electronic detonators based on stress‒strength interference theory is proposed.Furthermore,the impact failure model of electronic detonators considering the strength degradation effect under repeated random loads is established.On this basis,the failure mechanism of electronic detonators under different application environments,such as open-pit blasting and underground blasting,is revealed,which provides scientific theory and methods for the reliability analysis,design and type selection of electronic detonators in rock drilling and blasting.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
Research on detonation has traditionally focused on forward solutions,with limited attention to inverse design methods,which has significantly hindered the development of detonation engines.In this paper,the Method of...Research on detonation has traditionally focused on forward solutions,with limited attention to inverse design methods,which has significantly hindered the development of detonation engines.In this paper,the Method of characteristics for Curved-Detonation(MOCD)is proposed to enable the inverse design of detonation waves.MOCD is based on the Method of Curved-shock Characteristics(MOCC)and integrates higher-order aerodynamic parameters from Curved Detonation Equations(CDE),allowing the calculation of the wedge angle given specific wave angle.The effectiveness of MOCD is validated using both oblique and curved detonation waves with single-step and detailed chemical reactions.Various applications demonstrate the ability to meet the inverse design requirements of detonation engines.For example,inverse design for given wave angles can optimize engine thrust and prevent Mach reflections.Additionally,inverse design schemes tailored to incoming flow conditions,such as varying Mach numbers and equivalence ratios,enhance the feasibility of detonation engines.Applying the method to given post-wave aerodynamic parameters enables more precise engine design,which is crucial for improving propulsion performance and effective thermal protection.In summary,the advantages of MOCD include not only performing a fast solution of the detonation flow field,but also allowing the inverse design of the detonation wave.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
In this study,we aimed to investigate the detonation wave characteristics of a gel propellant with high boron content.A steady-state detonation wave model of a boron-based gel propellant considering the latent heat of...In this study,we aimed to investigate the detonation wave characteristics of a gel propellant with high boron content.A steady-state detonation wave model of a boron-based gel propellant considering the latent heat of phase change was proposed.The detonation wave model was validated through a comparative analysis with shock tube experiments,which revealed that the maximum deviation in the calculated peak detonation pressure was 8%based on various initial pressures.Upon iterative calculations,the eigenvalue detonation velocity of the boron-based gel propellant under default working conditions was obtained as 1831.5 m/s.Subsequently,the refined model was used to study the structure and characteristics of the detonation wave flow field.The effects of incoming flow conditions,fuel parameters,and initial operating state on the detonation wave flow field of the propellant were investigated numerically.The findings revealed that stable and self-sustaining propagation of the detonation wave can be achieved only when its propagation velocity matches the eigenvalue detonation velocity.Note that an increase in initial temperature resulted in elevated gas phase temperature,density,detonation pressure,and particle phase temperature.An increase in boron content within the gel propellant increased the gas phase temperature but decreased the gas phase density and detonation pressure.At the Chapman-Jouguet(CJ)plane,the gas phase temperature and density,along with the particle phase temperature and detonation pressure,reached their peak values when the oxidizer reacted with the propellant in accordance with the stoichiometric ratio.展开更多
The distribution of exothermic reaction rates is jointly influenced by reduced activation energy and reaction rate constant.This study focuses on the effect of distribution of exothermic reaction rates on detonation w...The distribution of exothermic reaction rates is jointly influenced by reduced activation energy and reaction rate constant.This study focuses on the effect of distribution of exothermic reaction rates on detonation wave propagation instability,specifically under conditions where the length of the induction and exothermic reaction remains constant.It is found that the distribution variation of exothermic reaction rates significantly influences the detonation wave propagation characteristics.Specifically,under conditions of high activation energy,the exothermic reaction rate profile exhibits a smoother distribution but becomes more prone to perturbations.This heightened sensitivity,coupled with the augmented overdriven degree associated with pulsating detonation and cellular detonation wave propagation,further exacerbates the instability characteristics of detonation waves.Especially to the two-dimensional detonation waves with high activation energies,the distribution of exothermic reaction rates becomes more sensitive to these displacements,reinforcing the transverse shock wave and leading to a transformation of the wavefront and cellular structure towards more unstable configurations.This research delves into the intricate interactions between the distribution of exothermic reaction rates and detonation wave instability,aiming to provide an explanatory of detonation instability.展开更多
In order to find the optimal anions and cations for designing energetic salts with excellent detonation properties,the properties of 140 salts formed from the anions(A–G)of 3,3′-dinitroamino-4,4′-azoxyfurazan(DAAF)...In order to find the optimal anions and cations for designing energetic salts with excellent detonation properties,the properties of 140 salts formed from the anions(A–G)of 3,3′-dinitroamino-4,4′-azoxyfurazan(DAAF)derivatives substituted with the—NH_(2),—N_(3) or—NO_(2) group and the cations(1–20)of guanidine,triazole,or tetrazole derivatives were investigated by means of density-functional theory.The predicted densities,heats of formation,detonation velocities(D),and detonation pressures(P)of 140 salts were 11.72 to 2.06 g·cm ^(−3),570.2 to 2333.4 kJ·mol^(−1),8.29 to 10.02 km·s^(−1) and 30.16 to 47.57 GPa,respectively.Most of the salts had better detonation properties than the widely used hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX).Salts containing—NO_(2) group anions(C and F)have better detonation properties(D is 8.88 to 10.02 km·s^(−1) and P is 35.75 to 47.75 GPa)than other salts.Salts containing the cations NH_(4)^(+)(1),NH_(3)OH^(+)(2)and CH_(2)N_(4)NO_(2)^(+)(20)had good detonation properties(D is 9.38 to 10.02 km·s^(−1) and P is 40.72 to 47.75 GPa).Depending on the detonation properties,anions(C and F)and cations(1,2 and 20)are the recommended ions for the generation of energetic salts.展开更多
This study investigates the mixing enhancement mechanism and propagation characteristics of the detonation flow field of a Rotating Detonation Engine(RDE).Three-dimensional numerical simulations of a non-premixed ramj...This study investigates the mixing enhancement mechanism and propagation characteristics of the detonation flow field of a Rotating Detonation Engine(RDE).Three-dimensional numerical simulations of a non-premixed ramjet-based RDE fueled by gaseous ethylene are performed in OpenFOAM for configurations with 15,30,45,and 60 orifices at a flight Mach number of 4.The results show that fuels with a stripped distribution are primarily mixed via tangential diffusion in the cold flow field.The configuration with more orifices has a better upstream mixing efficiency,whereas its downstream mixing efficiency,which is limited by the depth of penetration,is difficult to improve further.Backward Pressure Perturbations(BPPs)opposite to the propagation direction of Rotating Detonation Waves(RDWs)are produced by the reflection of the upstream oblique shock wave with the incoming stream and the hot release of local reactions after RDWs,which significantly affects the propagation mode and mixing.The RDWs propagate in the stable single-wave mode in configurations with 45 or 60 orifices and in the multi-wave mode in configurations with 30 orifices,whereas they fail in configurations with 15 orifices.Compared with that in the cold flow field,deceleration of the main flow,pressurization,and tangential velocity perturbation caused by the RDW substantially enhance the mixing efficiency.Moreover,the tangential velocity perturbations of upstream oblique shock waves and BPPs reduce the unevenness of the fuel distribution for the next cycle.This study reveals the mixing enhancement mechanism of RDWs and can contribute to the design of the injection scheme of the RDE.展开更多
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the National Natural Science Foundation of China under Grant Number NSFC 11801302Tsinghua University Initiative Scientific Research Program.Yang Yang is supported by the NSF Grant DMS-1818467.
文摘In this paper,we apply high-order finite difference(FD)schemes for multispecies and multireaction detonations(MMD).In MMD,the density and pressure are positive and the mass fraction of the ith species in the chemical reaction,say zi,is between 0 and 1,withΣz_(i)=1.Due to the lack of maximum-principle,most of the previous bound-preserving technique cannot be applied directly.To preserve those bounds,we will use the positivity-preserving technique to all the zi'is and enforceΣz_(i)=1 by constructing conservative schemes,thanks to conservative time integrations and consistent numerical fluxes in the system.Moreover,detonation is an extreme singular mode of flame propagation in premixed gas,and the model contains a significant stiff source.It is well known that for hyperbolic equations with stiff source,the transition points in the numerical approximations near the shocks may trigger spurious shock speed,leading to wrong shock position.Intuitively,the high-order weighted essentially non-oscillatory(WENO)scheme,which can suppress oscillations near the discontinuities,would be a good choice for spatial discretization.However,with the nonlinear weights,the numerical fluxes are no longer“consistent”,leading to nonconservative numerical schemes and the bound-preserving technique does not work.Numerical experiments demonstrate that,without further numerical techniques such as subcell resolutions,the conservative FD method with linear weights can yield better numerical approximations than the nonconservative WENO scheme.
基金This work was funded by the National Natural Science Foundation of China(Grants 12072036 and 11532012)Project of State Key Laboratory of Explosion Science and Technology(Grant QNKT19-01).
文摘The cell size variation in overdriven gaseous detonations is studied in hydrogen/oxygen and acetylene/oxygen mixtures.The local self-similarity of Mach reflection of detonations on the wedge in the far field renders the presence of a steady overdriven Mach stem to be possible.The study focuses on the cell size change of overdriven Mach stem on the wedge surface other than on the sidewall.The detonation cell pattern on the wedge surface has a complicated process of three-stage pattern,i.e.,the cells decreasing from large to small size,and then increasing asymptotically to a medium size and keeping constant.The cell size ratio with increasing the degree of overdrive is also examined.It is found that the ratio decays as the degree of overdrive increases.However,as the wedge angle increases to a critical value,finer cells are not created on the smoke foils.Ng’s model used to predict the cell size is also found to be valid only for detonations with relative large instability parameters,but presents large errors for highly overdriven detonations with low instability.A modification to Ng’s model is proposed based on the experimental results.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11390363 and 11325209
文摘The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism, The numerical results demonstrate that as the radius of the curvature decreases, detonation fails near the inner wall due to the strong expansion effect. As the radius of the curvature increases, the detonation front near the inner wall can sustain an underdriven detonation. In the case where deto- nation fails, a transverse detonation downstream forms and re-initiates the quenched detonation as it propagates toward the inner wall. Two kinds of propagation modes exist as the detonation is propagating in the curved channel. One is that the detonation fails first, and then a following transverse detonation initiates the quenched detonation and this process repeats itself. The other one is that without detonation failure and re-initiation, a steady detonation exists which consists of an underdriven detonation front near the inner wall subject to the diffraction and an overdriven detonation near the outer wall subject to the compression.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91541206 and 91441131
文摘The direct initiation of detonations in one-dimensional （1D） and two-dimensional （2D） cylindrical geometries is investigated through numerical simulations. In comparison of 1D and 2D simulations, it is found that cellular instability has a negative effect on the 2D initiation and makes it more difficult to initiate a sustaining 2D cylindrical detonation. This effect associates closely with the activation energy. For the lower activation energy, the 2D initiation of cylindrical detonations can be achieved through a subcritical initiation way. With increasing the activation energy, the 2D cylindrical detonation has increased difficulty in its initiation due to the presence of unreacted pockets behind the detonation front and usually requires rather larger source energy.
基金This work was supported by the National Natural Science Foundation of China(Grant 11822202).
文摘The dynamics of frontal and transverse shocks in gaseous detonation waves is a complex phenomenon bringing many difficulties to both numerical and experimental research.Advanced laser-optical visualization of detonation structure may provide certain information of its reactive front,but the corresponding lead shock needs to be reconstructed building the complete flow field.Using the multi-layer perceptron(MLP)approach,we propose a shock front reconstruction method which can predict evolution of the lead shock wavefront from the state of the reactive front.The method is verified through the numerical results of one-and two-dimensional unstable detonations based on the reactive Euler equations with a one-step irreversible chemical reaction model.Results show that the accuracy of the proposed method depends on the activation energy of the reactive mixture,which influences prominently the cellular detonation instability and hence,the distortion of the lead shock surface.To select the input variables for training and evaluate their influence on the effectiveness of the proposed method,five groups,one with six variables,and the other with four variables,are tested and analyzed in the MLP model.The trained MLP is tested in the cases with different activation energies,demonstrates the inspiring generalization capability.This paper offers a universal framework for predicting detonation frontal evolution and provides a novel way to interpret numerical and experimental results of detonation waves.
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.
文摘Multi-dimensional direct numerical simulations （DNS） of astrophysical detonations in degenerate matter have revealed that the nuclear burning is typically characterized by cellular structure caused by transverse instabilities in the detonation front. Type Ia supernova modelers often use one- dimensional DNS of detonations as inputs or constraints for their whole star simulations. While these one-dimensional studies are useful tools, the true nature of the detonation is multi-dimensional. The multi-dimensional structure of the burning influences the speed, stability, and the composition of the detonation and its burning products, and therefore, could have an impact on the spectra of Type Ia supernovae. Considerable effort has been expended modeling Type Ia supernovae at densities above 1 ~ 107 g.cm-3 where the complexities of turbulent burning dominate the flame propagation. How- ever, most full star models turn the nuclear burning schemes off when the density falls below 1 ~ 107 g.cm-3 and distributed burning begins. The deflagration to detonation transition （DDT） is believed to occur at just these densities and consequently they are the densities important for studying the properties of the subsequent detonation. This work will review the status of DNS studies of detona- tions and their possible implications for Type Ia supernova models. It will cover the development of Detonation theory from the first simple Chapman-Jouguet （C J） detonation models to the current models based on the time-dependent, compressible, reactive flow Euler equations of fluid dynamics.
基金supported by the National Natural Science Foundation of China(Grant No.12402432)Natural Science Foundation of Jiangsu Province of China(Grant No.BK20230936)Graduate Education and Teaching Reform Project of Nanjing University of Science and Technology(Grant No.KT2024_C14)。
文摘To elucidate the dispersion and explosion characteristics of multi-metal powder and liquid composite fuel formulations,high-energy metal powders(aluminum(Al),boron(B),and magnesium hydride(MgH_(2)))are incorporated into a liquid fuel primarily composed of diethyl ether(DEE)and isopropyl nitrate(IPN).The explosion characteristics of different solid-liquid fuel-air-explosive(FAE)under unconfined conditions are investigated using a high-speed camera,infrared thermal imaging,and a pressure measurement system.Results demonstrate that high-energy metal powders significantly enhance detonation energy dissipation,with aluminum exhibiting the most pronounced effect.Fuel 5#(45.4 wt%DEE,9.2 wt%IPN,29.5 wt%Al,9.1 wt%B,6.8 wt%MgH_(2))exhibits superior explosion performance,achieving higher values of overpressure,impulse,and thermal radiation damage during the detonation stage compared to other fuels.However,Fuel 5#also displays faster decay rates,attributed to accelerated heat release rates induced by B and MgH_(2)powders.This study reveals that different metal powders in solid-liquid FAE exhibit distinct enhancements in explosion performance,providing critical insights for optimizing composite fuel design.
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supported by the National Science Foundation of China(Grant No.14102428)the Fundamental Research Funds for the Central Universities(Grant Nos.WK2090000019 and YD2480002002)the Open Research Fund of Anhui Province Key Laboratory of Green Building and Assembly Construction,Anhui Institute of Building Research&Design(Grant No.2021-JKYL-005).
文摘Rectangular explosive charges are usually used in military or civilian explosive transportation and storage.The effects of shape parameters and detonation positions on the peak overpressure and maximum impulse of blasts lack comprehensive investigation,which is significant for the design of blast-resistant structures.In this paper,the side-length ratio of the rectangle,orientation,and detonation position of the charge are chosen as controlling parameters to investigate their influence on blast loads in the scaled distances of the gauges ranging from 0.63 to 10.54 m/kg^(1/3) with well validated 3D numerical simulations.The results show that there is a large difference in the near-field spatial distribution of the blast load of the rectangular charge;if the blast load of the rectangular charge is simply evaluated with the spherical charge,the maximum peak overpressure(maximum impulse)will be underestimated by a factor of 7.46(4.84).This must be taken seriously by blast-resistant structure designers.With the increase in the scaled distance,when the critical scaled distance is greater than 6.32(7.38)m/kg^(1/3),the influence of the charge shape on the maximum peak overpressure(maximum impulse)of the spatial blast load can be ignored.In general,the impact of detonation of the charge at the end on the maximum peak overpressure is greater compared with central detonation,but for the impact of the maximum impulse,it is necessary to pay attention to the side-length ratio of the rectangular charge and the specific detonation position on the end face.Furthermore,the structural response of steel plates placed at different azimuths under the blast load of a rectangular charge is preliminarily analyzed,and the results show that the deformation and energy of the plates are consistent with the distribution of the blast load.These analysis results provide a reference for the explosion protection design in near-field air explosions.
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supported by the Chongqing Youth Talent Support Program(Cstc2022ycjh-bgzxm0079)the Chinese National Natural Science Foundation(52379128,51979152)+2 种基金Science Fund for Distinguished Young Scholars of Hubei Proivnce(2023AFA048)Educational Commission of Hubei Province of China(T2020005)the Young Top-notch Talent Cultivation Program of Hubei Province.
文摘In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and comprehensive understanding of the failure mechanisms of electronic detonators subjected to impact loading is of great significance to the reliability design and field safety use of electronic detonators.The spatial distribution characteristics and failure modes of misfired electronic detonators under different application scenarios are statistically analysed.The results show that under high impact loads,electronic detonators will experience failure phenomena such as rupture of the fuse head,fracture of the bridge wire,falling off of the solder joint,chip module damage and insufficient initiation energy after deformation.The lack of impact resistance is the primary cause of misfire of electronic detonators.Combined with the underwater impact resistance test and the impact load test in the adjacent blasthole on site,the formulas of the impact failure probability of the electronic detonator under different stress‒strength distribution curves are deduced.The test and evaluation method of the impact resistance of electronic detonators based on stress‒strength interference theory is proposed.Furthermore,the impact failure model of electronic detonators considering the strength degradation effect under repeated random loads is established.On this basis,the failure mechanism of electronic detonators under different application environments,such as open-pit blasting and underground blasting,is revealed,which provides scientific theory and methods for the reliability analysis,design and type selection of electronic detonators in rock drilling and blasting.
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the support of the National Natural Science Foundation of China,China(Nos.U20A2069,U21B6003,and 12302389)the Advanced Aero-Power Innovation Workstation,China(No.HKCX2024-01-017)。
文摘Research on detonation has traditionally focused on forward solutions,with limited attention to inverse design methods,which has significantly hindered the development of detonation engines.In this paper,the Method of characteristics for Curved-Detonation(MOCD)is proposed to enable the inverse design of detonation waves.MOCD is based on the Method of Curved-shock Characteristics(MOCC)and integrates higher-order aerodynamic parameters from Curved Detonation Equations(CDE),allowing the calculation of the wedge angle given specific wave angle.The effectiveness of MOCD is validated using both oblique and curved detonation waves with single-step and detailed chemical reactions.Various applications demonstrate the ability to meet the inverse design requirements of detonation engines.For example,inverse design for given wave angles can optimize engine thrust and prevent Mach reflections.Additionally,inverse design schemes tailored to incoming flow conditions,such as varying Mach numbers and equivalence ratios,enhance the feasibility of detonation engines.Applying the method to given post-wave aerodynamic parameters enables more precise engine design,which is crucial for improving propulsion performance and effective thermal protection.In summary,the advantages of MOCD include not only performing a fast solution of the detonation flow field,but also allowing the inverse design of the detonation wave.
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 Science and Technology Innovation Program of Hunan Province(No.2022RC3045)the Hunan Provincial Natural Science Foundation of China(No.2023JJ30635)the National Natural Science Foundation of China(No.12302394).
文摘In this study,we aimed to investigate the detonation wave characteristics of a gel propellant with high boron content.A steady-state detonation wave model of a boron-based gel propellant considering the latent heat of phase change was proposed.The detonation wave model was validated through a comparative analysis with shock tube experiments,which revealed that the maximum deviation in the calculated peak detonation pressure was 8%based on various initial pressures.Upon iterative calculations,the eigenvalue detonation velocity of the boron-based gel propellant under default working conditions was obtained as 1831.5 m/s.Subsequently,the refined model was used to study the structure and characteristics of the detonation wave flow field.The effects of incoming flow conditions,fuel parameters,and initial operating state on the detonation wave flow field of the propellant were investigated numerically.The findings revealed that stable and self-sustaining propagation of the detonation wave can be achieved only when its propagation velocity matches the eigenvalue detonation velocity.Note that an increase in initial temperature resulted in elevated gas phase temperature,density,detonation pressure,and particle phase temperature.An increase in boron content within the gel propellant increased the gas phase temperature but decreased the gas phase density and detonation pressure.At the Chapman-Jouguet(CJ)plane,the gas phase temperature and density,along with the particle phase temperature and detonation pressure,reached their peak values when the oxidizer reacted with the propellant in accordance with the stoichiometric ratio.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB3207000)National Natural Science Foundation of China(Grant No.12132017)Youth Cross Team CAS(Grant No.JCTD-2022-02)and Youth Innovation Promotion Association CAS(Grant No.2020019).
文摘The distribution of exothermic reaction rates is jointly influenced by reduced activation energy and reaction rate constant.This study focuses on the effect of distribution of exothermic reaction rates on detonation wave propagation instability,specifically under conditions where the length of the induction and exothermic reaction remains constant.It is found that the distribution variation of exothermic reaction rates significantly influences the detonation wave propagation characteristics.Specifically,under conditions of high activation energy,the exothermic reaction rate profile exhibits a smoother distribution but becomes more prone to perturbations.This heightened sensitivity,coupled with the augmented overdriven degree associated with pulsating detonation and cellular detonation wave propagation,further exacerbates the instability characteristics of detonation waves.Especially to the two-dimensional detonation waves with high activation energies,the distribution of exothermic reaction rates becomes more sensitive to these displacements,reinforcing the transverse shock wave and leading to a transformation of the wavefront and cellular structure towards more unstable configurations.This research delves into the intricate interactions between the distribution of exothermic reaction rates and detonation wave instability,aiming to provide an explanatory of detonation instability.
文摘In order to find the optimal anions and cations for designing energetic salts with excellent detonation properties,the properties of 140 salts formed from the anions(A–G)of 3,3′-dinitroamino-4,4′-azoxyfurazan(DAAF)derivatives substituted with the—NH_(2),—N_(3) or—NO_(2) group and the cations(1–20)of guanidine,triazole,or tetrazole derivatives were investigated by means of density-functional theory.The predicted densities,heats of formation,detonation velocities(D),and detonation pressures(P)of 140 salts were 11.72 to 2.06 g·cm ^(−3),570.2 to 2333.4 kJ·mol^(−1),8.29 to 10.02 km·s^(−1) and 30.16 to 47.57 GPa,respectively.Most of the salts had better detonation properties than the widely used hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX).Salts containing—NO_(2) group anions(C and F)have better detonation properties(D is 8.88 to 10.02 km·s^(−1) and P is 35.75 to 47.75 GPa)than other salts.Salts containing the cations NH_(4)^(+)(1),NH_(3)OH^(+)(2)and CH_(2)N_(4)NO_(2)^(+)(20)had good detonation properties(D is 9.38 to 10.02 km·s^(−1) and P is 40.72 to 47.75 GPa).Depending on the detonation properties,anions(C and F)and cations(1,2 and 20)are the recommended ions for the generation of energetic salts.
基金supported from support from the National Natural Science Foundation of China(Nos.12441204,12302451 and 1202491)the Postgraduate Scientific Research Innovation Project of Hunan Province,China(No.CX20210075)。
文摘This study investigates the mixing enhancement mechanism and propagation characteristics of the detonation flow field of a Rotating Detonation Engine(RDE).Three-dimensional numerical simulations of a non-premixed ramjet-based RDE fueled by gaseous ethylene are performed in OpenFOAM for configurations with 15,30,45,and 60 orifices at a flight Mach number of 4.The results show that fuels with a stripped distribution are primarily mixed via tangential diffusion in the cold flow field.The configuration with more orifices has a better upstream mixing efficiency,whereas its downstream mixing efficiency,which is limited by the depth of penetration,is difficult to improve further.Backward Pressure Perturbations(BPPs)opposite to the propagation direction of Rotating Detonation Waves(RDWs)are produced by the reflection of the upstream oblique shock wave with the incoming stream and the hot release of local reactions after RDWs,which significantly affects the propagation mode and mixing.The RDWs propagate in the stable single-wave mode in configurations with 45 or 60 orifices and in the multi-wave mode in configurations with 30 orifices,whereas they fail in configurations with 15 orifices.Compared with that in the cold flow field,deceleration of the main flow,pressurization,and tangential velocity perturbation caused by the RDW substantially enhance the mixing efficiency.Moreover,the tangential velocity perturbations of upstream oblique shock waves and BPPs reduce the unevenness of the fuel distribution for the next cycle.This study reveals the mixing enhancement mechanism of RDWs and can contribute to the design of the injection scheme of the RDE.
