The interactions of a spherical flame with an incident shock wave and its reflected shock wave in a confined space were investigated using the three-dimensional reactive Navier-Stokes equations, with emphasis placed o...The interactions of a spherical flame with an incident shock wave and its reflected shock wave in a confined space were investigated using the three-dimensional reactive Navier-Stokes equations, with emphasis placed on the effect of chemical reactivity of mixture on the flame distortion and detonation initiation after the passage of the reflected shock wave. It is shown that the spatio-temporal characteristics of detonation initiation depend highly on the chemi- cal reactivity of the mixture. When the chemical reactivity enhances, the flame can be severely distorted to form a reactive shock bifurcation structure with detonations initiating at different three-dimensional spatial locations. Moreover, the detonation initiation would occur earlier in a mixture of more enhanced reactivity. The results reveal that the detona- tions arise from hot spots in the unburned region which are initiated by the shock-detonation-transition mechanism.展开更多
Nanodiamonds(NDs)have been widely explored for applications in drug delivery,optical bioimaging,sensors,quantum computing,and others.Room-temperature nanomanufacturing of NDs in open air using confined laser shock det...Nanodiamonds(NDs)have been widely explored for applications in drug delivery,optical bioimaging,sensors,quantum computing,and others.Room-temperature nanomanufacturing of NDs in open air using confined laser shock detonation(CLSD)emerges as a novel manufacturing strategy for ND fabrication.However,the fundamental process mechanism remains unclear.This work investigates the underlying mechanisms responsible for nanomanufacturing of NDs during CLSD with a focus on the laser-matter interaction,the role of the confining effect,and the graphite-to-diamond transition.Specifically,a first-principles model is integrated with a molecular dynamics simulation to describe the laser-induced thermo-hydrodynamic phenomena and the graphite-to-diamond phase transition during CLSD.The simulation results elucidate the confining effect in determining the material’s responses to laser irradiation in terms of the temporal and spatial evolutions of temperature,pressure,electron number density,and particle velocity.The integrated model demonstrates the capability of predicting the laser energy threshold for ND synthesis and the efficiency of ND nucleation under varying processing parameters.This research will provide significant insights into CLSD and advance this nanomanufacturing strategy for the fabrication of NDs and other high-temperature-high-pressure synthesized nanomaterials towards extensive applications.展开更多
The behavior of the charge initiation of the coated-type projectile penetrating target is researched by means of numerical simulation. The influences on charge initiation of the projectile shape, shell thickness, char...The behavior of the charge initiation of the coated-type projectile penetrating target is researched by means of numerical simulation. The influences on charge initiation of the projectile shape, shell thickness, charge diameter, and projectile velocity are analyzed. Results show that projectile shape takes an obvious impact on critical detonation velocity, that for the projectile with the same quality, it is more vulnerable for the cylindrical projectile with the one length-diameter ratio to occurring shock initiation than the spherical projectile, the charge diameter is an important factor that affecting critical detonation velocity, which significantly decreases as the charge diameter increases.展开更多
By means of researching into sympathetic detonation of blasting detonators in air, the regular patterns are concluded from blasting detonators interaction with the shock loading. The aerial distribution of initiating ...By means of researching into sympathetic detonation of blasting detonators in air, the regular patterns are concluded from blasting detonators interaction with the shock loading. The aerial distribution of initiating ability of detonators looks like a butterfly. The initiating ability mainly consists of shock wave, explosive gases and fliers. But fundamental questions remain. When does shock wave take the leading role? When and how does the explosive gases or the fliers take function? For those questions, there is less quantitative research. Through the theoretic deduction of the overpressure, the energy calculation of fliers and the experiment of sympathetic detonation of detonators, we can learn the sympathetic detonation distances of several kinds of detonators and make an inquiry into the lateral initiating regulations of detonators. So, we can provide the base data for the research into no sympathetic detonation of herd blasting detonators and then control the detonation between them. Then we can make full use of detonators and reduce the frequency of accidents caused by detonators.展开更多
Pressure-gain combustion has gained attention for airbreathing ramjet engine applications owing to its better thermodynamic efficiency and fuel consumption rate. In contrast with traditional detonation induced by a si...Pressure-gain combustion has gained attention for airbreathing ramjet engine applications owing to its better thermodynamic efficiency and fuel consumption rate. In contrast with traditional detonation induced by a single wedge, the present study considers oblique shock interactions attached to double wedges in a hypersonic combustible flow. The temperature/pressure increases sharply across the interaction zone that initiates an exothermic reaction, finally resulting in an Oblique Detonation Wave(ODW). Compared with the case for a single-wedge ODW, the double-wedge geometry has great potential to control the initiation of the ODW. As a tentative study, two-dimensional compressible Euler equations with a two-step induction-reaction kinetic model are used to solve the detonation dynamics triggered by a double wedge. The effects of the wedge angles and wedge corner locations on the initiation structures are investigated numerically.The results show an ODW complex comprising three Oblique Shock Waves(OSWs), an induction zone, a curved detonation front, and an unburned/low-temperature gas belt close to the surface of the second wedge. Both the increasing wedge angle and downstream wedge corner location lead to an abrupt OSW–ODW transition type, whereas the former corresponds to the shock–shock interaction and the later has a greater effect on the exothermic chemical process. Analysis of the shock polar and flow scale confirms that the OSW–ODW initiation structure mainly depends on the coupling of shocks and heat release in a confined initiation zone.展开更多
基金supported by the National Natural Science Foundation of China (10972107)Open Fund of State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology (KFJJ12-4Y)Jiangsu Innovation Program for Graduate Education (CXLX11 0271)
文摘The interactions of a spherical flame with an incident shock wave and its reflected shock wave in a confined space were investigated using the three-dimensional reactive Navier-Stokes equations, with emphasis placed on the effect of chemical reactivity of mixture on the flame distortion and detonation initiation after the passage of the reflected shock wave. It is shown that the spatio-temporal characteristics of detonation initiation depend highly on the chemi- cal reactivity of the mixture. When the chemical reactivity enhances, the flame can be severely distorted to form a reactive shock bifurcation structure with detonations initiating at different three-dimensional spatial locations. Moreover, the detonation initiation would occur earlier in a mixture of more enhanced reactivity. The results reveal that the detona- tions arise from hot spots in the unburned region which are initiated by the shock-detonation-transition mechanism.
基金National Science Foundation(NSF)under award numbers CMMI-1826439 and CMMI-1825739。
文摘Nanodiamonds(NDs)have been widely explored for applications in drug delivery,optical bioimaging,sensors,quantum computing,and others.Room-temperature nanomanufacturing of NDs in open air using confined laser shock detonation(CLSD)emerges as a novel manufacturing strategy for ND fabrication.However,the fundamental process mechanism remains unclear.This work investigates the underlying mechanisms responsible for nanomanufacturing of NDs during CLSD with a focus on the laser-matter interaction,the role of the confining effect,and the graphite-to-diamond transition.Specifically,a first-principles model is integrated with a molecular dynamics simulation to describe the laser-induced thermo-hydrodynamic phenomena and the graphite-to-diamond phase transition during CLSD.The simulation results elucidate the confining effect in determining the material’s responses to laser irradiation in terms of the temporal and spatial evolutions of temperature,pressure,electron number density,and particle velocity.The integrated model demonstrates the capability of predicting the laser energy threshold for ND synthesis and the efficiency of ND nucleation under varying processing parameters.This research will provide significant insights into CLSD and advance this nanomanufacturing strategy for the fabrication of NDs and other high-temperature-high-pressure synthesized nanomaterials towards extensive applications.
基金Supported by the 11th Five-Year Defense Pre-research Fund(7130810)
文摘The behavior of the charge initiation of the coated-type projectile penetrating target is researched by means of numerical simulation. The influences on charge initiation of the projectile shape, shell thickness, charge diameter, and projectile velocity are analyzed. Results show that projectile shape takes an obvious impact on critical detonation velocity, that for the projectile with the same quality, it is more vulnerable for the cylindrical projectile with the one length-diameter ratio to occurring shock initiation than the spherical projectile, the charge diameter is an important factor that affecting critical detonation velocity, which significantly decreases as the charge diameter increases.
文摘By means of researching into sympathetic detonation of blasting detonators in air, the regular patterns are concluded from blasting detonators interaction with the shock loading. The aerial distribution of initiating ability of detonators looks like a butterfly. The initiating ability mainly consists of shock wave, explosive gases and fliers. But fundamental questions remain. When does shock wave take the leading role? When and how does the explosive gases or the fliers take function? For those questions, there is less quantitative research. Through the theoretic deduction of the overpressure, the energy calculation of fliers and the experiment of sympathetic detonation of detonators, we can learn the sympathetic detonation distances of several kinds of detonators and make an inquiry into the lateral initiating regulations of detonators. So, we can provide the base data for the research into no sympathetic detonation of herd blasting detonators and then control the detonation between them. Then we can make full use of detonators and reduce the frequency of accidents caused by detonators.
基金supported by the National Natural Science Foundation of China(No.11822202)。
文摘Pressure-gain combustion has gained attention for airbreathing ramjet engine applications owing to its better thermodynamic efficiency and fuel consumption rate. In contrast with traditional detonation induced by a single wedge, the present study considers oblique shock interactions attached to double wedges in a hypersonic combustible flow. The temperature/pressure increases sharply across the interaction zone that initiates an exothermic reaction, finally resulting in an Oblique Detonation Wave(ODW). Compared with the case for a single-wedge ODW, the double-wedge geometry has great potential to control the initiation of the ODW. As a tentative study, two-dimensional compressible Euler equations with a two-step induction-reaction kinetic model are used to solve the detonation dynamics triggered by a double wedge. The effects of the wedge angles and wedge corner locations on the initiation structures are investigated numerically.The results show an ODW complex comprising three Oblique Shock Waves(OSWs), an induction zone, a curved detonation front, and an unburned/low-temperature gas belt close to the surface of the second wedge. Both the increasing wedge angle and downstream wedge corner location lead to an abrupt OSW–ODW transition type, whereas the former corresponds to the shock–shock interaction and the later has a greater effect on the exothermic chemical process. Analysis of the shock polar and flow scale confirms that the OSW–ODW initiation structure mainly depends on the coupling of shocks and heat release in a confined initiation zone.
