Abstract:The ignition and combustion characteristics of NEPE propellant were studied based on a CO₂ laser ignition test platform established， in which the combustion processes of NEPE propellant in different gas environments were photographed using a high-speed camera and the ignition delay times of NEPE propellant were measured under the pressure of 0.1-3.0 MPa in nitrogen and air through a signal acquisition system. The results show that the ambient pressure and gas environment strongly affect the ignition and combustion process of NEPE propellant. The combustion of NEPE propellant becomes more intense as the increase of ambient pressure， and the burning of NEPE propellant appears more violent in air as compared to that in nitrogen. The ignition delay time of NEPE propellant decreases with the ambient pressure increases in the range of 0.1 MPa to 3.0 MPa. Specifically， the reduction in ignition delay time of NEPE propellant is observed from 0.51 s to 0.29 s in nitrogen and from 0.32 s to 0.18 s in air. However， when the ambient pressure exceeds 0.5 MPa， the influence of the ambient pressure on the ignition delay time becomes insignificant. In addition， the burning rate of NEPE propellant is also found to be effectively affected by the ambient pressure. With the ambient pressure increases from 0.1 MPa to 3.0 MPa， the enhancement in burning rate of NEPE propellant can be seen from 1.71 mm·s^-1 to 4.54 mm·s^-1 in nitrogen and from 2.51 mm·s^-1 to 11.4 mm·s^-1 in air， and thus a stronger increase in the burning rate is observed in air. Finally， the experimental data of burning rate were fitted by an empirical formula， which indicates the Vielle burning rate formula is more suitable for reproducing the burning rate characteristics of NEPE propellant especially at 0.1-3.0 MPa.

Abstract:To investigate the influence of the loading density of main propellant charge on the propagation characteristics of ignition charge gas in the granular propellant bed， the test platform for ignition and propagation of a large-diameter dense propellant bed was established， and the flame sequence diagram and the pressure changes of partial pressure gauges were recorded in tests. The porous medium model was used to simulate the granular propellant bed in the charge chamber， and the ignition and propagation model corresponding to the test device was established to numerically simulate the flow process of ignition charge gas in the granular propellant bed. The simulation results were compared with the test results to verify the reliability of the model， and then the propagation characteristics of temperature and pressure fields of gas in the propellant bed with different loading densities were calculated. The results show that the calculated results are in good agreement with the experimental flame propagation sequence process and the experimental pressure histories， which verifies the reliability of the model. Under the condition of any porosity， the axial displacement of flame front develops rapidly and the axial velocity decreases from 25-30 m·s^-1 to 10 m·s^-1 during 0-10 ms， ， and the axial velocity decreases to 2-3 m·s^-1 during 10-40 ms. Similarly， under the condition of any porosity， the development of radial displacement of flame front is concentrated during 2.2-3 ms， and the radial velocity decreases to 20-22 m·s^-1 at 3 ms. However， the radial velocity at the initial time is large for large porosity. When the porosity increases from 0.3 to 0.5， the pressure difference at different positions in the chamber decreases 16.7% from 0.24 MPa to 0.20 MPa， and the uniformity and instantaneity of ignition are improved. With the increase of porosity， the axial and radial resistances of the flame front in propagation process decrease， the axial expansion displacement of the flame front and the initial velocity of flame propagation in the axial and radial directions increase， but the final velocity tends to be the same. The smaller the pressure in the chamber， the smaller the pressure difference in the chamber.

Abstract:Three energetic coordination compounds with strong reducibility were prepared with cyanoborohydride （CBH） as anion， 1-vinyl imidazole （VIM） as ligand and transition metals Co， Mn and Ni as central ions. The crystal structures were determined by single crystal X-ray diffraction and their molecular formulas are Co（VIM）₄（CBH）₂， Mn（VIM）₄（CBH）₂ and Ni（VIM）₄（CBH）₂， respectively. The thermal decomposition performance， oxygen bomb calorimetry and mechanical sensitivities of the complexes were tested. The results show that the complexes have high burning calorific capacity （26.5-29.1 kJ·g^-1）， low friction sensitivity （>360 N） and impact sensitivity （>40 J）. Hypergolic testing with white fuming nitric acid shows that the complexes can combust spontaneously， and the ignition delay time is short （4-13 ms）， which confirm the high reduction activity of the complexes. To explore the application of active coordination compounds in initiating explosive devices， three new composite igniting powders were obtained by mixing three complexes with sodium bromate in the mass ratio of 1∶7， respectively. The composite powders were ignited and tested with electric heating wire. After being ignited by electric heating wire， the three composite agents can burn continuously and produce large flame. Results show that the composite agents have potential applications as new ignition agents.

Abstract:To obtain the reaction characteristics of tetraethylammonium decahydrodecaborate （（C₂ H₅）₄N］₂B₁₀H₁₀，BHN-10） under explosion and shock， the reaction pathways and decomposition products of BHN-10 under shock were studied by electrically exploded plasma shock and explosive blast shock. Results show that the gaseous decomposition products of BHN-10 under electrically exploded plasma shock are organic combustible gases， such as carbon alkanes， alkenes， alkynes， and etc. BHN-10 has good stability under explosive blast shock. The shock wave of 25 GPa magnitude generated by explosive blast cannot promote the decomposition of BHN-10， while the explosion heat is a main factor leading to the reaction of BHN-10. The combustion of BHN-10 occurs under explosive blast shock after 8 ms， and the combustion appears from the central position， lasting for more than 200 ms. The mixture of HMX and BHN-10 has an accelerated diffusion speed of fireball under explosive blast shock， and its combustion time is equivalent to that of BHN-10.

Abstract:In order to study the laser radiation effect on Octogen （HMX） crystal， various technical methods were used to characterize the microstructure evolution of HMX crystal under 360 nm ultraviolet laser. By optical microscope， the process from accumulation of defects to cracking under laser irradiation was observed in HMX crystals. In-situ Raman spectroscopy demonstrated that the absorption of UV photons would stimulate HMX molecules， causing the ring vibration. In-situ wide-angle X-ray scattering （WAXS）， single crystal X-ray diffraction （SCXRD） and in-situ small-angle X-ray scattering （SAXS） were also adopted to study the crystal changes and defects evolution of HMX under UV laser irradiation. It is found that phase transformation does not happen but some new defects generate in HMX. The in-situ SAXS results show that the pores in HMX increase continuously after 1170 minutes of laser irradiation and a bimodal distribution exists in the region ranging from 10 to 20 nm and 30 to 40 nm， respectively. During the laser irradiation process， small pores in HMX keep accumulating and gradually merge into larger pores. Due to the accumulation of defects， the microcosmic pores extend into micro-cracks， and then expand into macro-cracks.

Abstract:In this work， the auto-ignition behaviors of FOX-7/NC/NG powder were investigated by using rapid compression machine （RCM） under a high temperature environment. High speed images and pressure evolutions were used to record the responses of FOX-7/NC/NG samples under high temperature and pressure conditions. Results show that the samples were not able to ignite at 3.0 MPa and 598.1 K， with the heating rate of about 1.2×10⁴ K·s^-1. With the temperature increasing to 913.1 K （the heating rate is about 2.5×10⁴ K·s^-1）， the auto-ignition was observed. In addition， the validated tests of FOX-7/NC/NG samples were conducted. Results show that the experiment has a good repeatability. The uncertainties of ignition delay times （IDT_I） and burning duration are less than 20% and 5%， respectively. Lastly， the auto-ignition behaviors of FOX-7/NC/NG samples were studied at different thermal loading rates. It was found that the higher thermal loading rate， the faster ignition and the shorter burning duration.

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