共查询到20条相似文献,搜索用时 31 毫秒
1.
N. E. Ermolin 《Combustion, Explosion, and Shock Waves》2007,43(5):549-561
To verify the adequacy of various models of heat release in ammonium dinitramide flame to real processes, chemical processes
in products of thermal decomposition at a pressure of 10 torr and in ammonium dinitramide [ADN; NH4N(NO2)2] flame at a pressure of 0.4 to 60 atm are numerically simulated. The calculations are performed on the basis of a detailed
kinetic mechanism and boundary conditions correlated with experimental data, thermodynamic properties, and chemical composition
of ADN. The kinetic mechanism includes submechanisms that describe high-temperature chemical processes in NH3/N2O/NO/NO2/HNO2/HNO3 and NH3/HN(NO2)2 mixtures, and the global stages of aerosol decomposition. Based on calculated and experimental data, the role of dinitraminic
acid HN(NO2)2, aerosols, and ADN vapor in heat release in the ADN flame zone adjacent to the burning surface is estimated. The calculations
predict that the main source of heat release in the cold flame zone at p ≥ 3 atm is dinitraminic acid incoming through the channel of dissociative evaporation ADNliq → NH3 + HN(NO2)2 from the burning surface. In the high-temperature flame zone, heat release is caused by the reaction that occurs in the NH3/N2O/NO/NO2/HNO2/HNO3 mixture. At moderate pressures, the high-temperature and low-temperature zones are separated by an induction zone. The stage
governing production of the OH radical, which plays an important role in combustion, in the induction zone is the reaction
HNO3 + M → OH + NO2 + M. Because of a high activation energy of the stage, small temperature perturbations in the induction zone at low pressures
lead to a finite change in the stand-off distance between the high-temperature flame zone and the burning surface. Therefore,
small temperature perturbations in the induction zone, which are caused by admixtures in the sample or by heat transfer between
the reacting gas and the ambient medium, may be responsible for disagreement between various experimental data and between
experimental and calculated data on the stand-off distance between the high-temperature flame zone and the burning surface.
In numerical calculations, the position of the high-temperature zone is effectively controlled by varying rate constants of
elementary stages within admissible limits.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 64–76, September–October, 2007. 相似文献
2.
A. A. Paletsky E. N. Volkov O. P. Korobeinichev 《Combustion, Explosion, and Shock Waves》2008,44(6):639-654
The chemical structure of HMX flame during combustion in air at a pressure of 1 atm was calculated using molecular beam mass
spectrometric sampling. HMX vapor was recorded for the first time near the burning surface. A total of 11 species were identified
in the HMX flame (H2, H2O, HCN, N2, CO, CH2O, NO, N2O, CO2, NO2, and HMX vapor), and their concentration profiles were measured. The HMX combustion was unstable. The species concentration
profiles exhibit periodic pulsations related to variation in the HMX burning rate. The HMX flame structure at various distances
to the burning surface was determined using the average value of the burning rate. Two main zones of chemical reactions in
the flame were found. In the first zone ≈0.8 mm wide adjacent to the burning surface, HMX vapor decomposes and NO2, N2O, and CH2O react with each other to form HCN and NO. In the second zone ≈0.8–1.5 mm wide, HCN was oxidized by nitric oxide to form
the final combustion products. The composition of the final combustion products was analyzed. The global reaction of HMX gasification
at a pressure of 1 atm was established. Heat release values in the condensed phase calculated by the global gasification reaction
and by the equation of heat balance on the burning surface (using literature data from microthermocouple measurements) were
analyzed and compared.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 26–43, November–December, 2008. 相似文献
3.
E. N. Volkov A. A. Paletsky O. P. Korobeinichev 《Combustion, Explosion, and Shock Waves》2008,44(1):43-54
The chemical structure of an RDX flame at a pressure of 1 atm was studied using probing molecular beam mass spectrometry.
The flame was found to contain RDX vapor, and its concentration profile was measured in a narrow zone adjacent to the burning
surface. In addition to RDX vapor, ten more species were identified (H2, H2O, HCN, N2, CO, CH2O, NO, N2O, CO2 and NO2), and their concentration profiles were measured. Two main chemical-reaction zones were found in the RDX flame. In the first,
narrow, zone 0.15 mm wide adjacent to the burning surface, decomposition of RDX vapor and the reaction of NO2, N2O, and CH2O with the formation of HCN and NO occur. In the second, wide, zone 0.85 mm wide, HCN is oxidized by NO to form the final
combustion products. The composition of the final combustion products was analyzed from an energetic point of view. The measured
composition of the products near the burning surface was used to determine the global reaction of RDX gasification at a pressure
of 1 atm. Values of heat release in the condensed-phase calculated by the global gasification reaction and by the equation
of heat balance on the burning surface (using data of microthermocouple measurements) were analyzed and compared.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 49–62, January–February, 2008. 相似文献
4.
E. N. Volkov A. A. Paletsky A. G. Tereshchenko O. P. Korobeinichev 《Combustion, Explosion, and Shock Waves》2006,42(6):663-671
A study was performed of the chemical and thermal structure of flames of model composite propellants based on cyclic nitramines
(RDX and HMX) and an active binder (glycidyl azide polymer) at a pressure of 1 MPa. Propellant burning rates were measured.
The chemical structure of the flame was studied using molecular-beam mass spectrometry, which previously has not been employed
at high pressures. Eleven species (H2, H2O, HCN, N2, CO, CH2O, NO, N2O, CO2, NO2, and nitramine vapor) were identified, and their concentration profiles, including the composition near the burning surface
were measured. Two chemical-reaction zones were observed. It was shown that flames of nitramine/glycidyl azide polymer propellants
are dominated by the same reactions as in flames of pure nitramines.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 6, pp. 48–57, November–December, 2006. 相似文献
5.
A comprehensive review of thermal decomposition and combustion of ammonium dinitramide (ADN) has been conducted. The basic
thermal properties, chemical pathways, and reaction products in both the condensed and gas phases are analyzed over a broad
range of ambient conditions. Detailed combustion-wave structures and burning-rate characteristics are discussed. Prominent
features of ADN combustion are identified and compared with other types of energetic materials. In particular, the influence
of various condensed- and gas-phase processes in dictating the pressure and temperature sensitivities of the burning rate
is examined. In the condensed phase, decomposition proceeds through the mechanisms ADN → NH4NO3 + N2O and ADN → NH3 + HNO3 + N2O, the former mechanism being the basic one. In the gas phase, the mechanisms ADN → NH3 + HDN and ADN → NH3 + HNO3 + N2O are prevalent. The gas-phase combustion-wave structure in the range of 5–20 atm consists of a near-surface primary flame
followed by a dark-zone temperature plateau at 600–1000°C and a secondary flame followed by another dark-zone temperature
plateau at 1000–1400°C. At higher pressures (60 atm and above), a final flame is observed at about 1800°C without the existence
of any dark-zone temperature plateau. ADN combustion is stable in the range of 5–20 atm and the pressure sensitivity of the
burning rate has the form r
b = 20.72p
0.604 [mm/sec] (p = 0.5–2.0 MPa). The burning characteristics are controlled by exothermic decomposition in the condensed phase. Above 100
atm, the burning rate is well correlated with pressure as r
b = 8.50p
0.608 [mm/sec] (p = 10–36 MPa). Combustion is stable, and intensive heat feedback from the gas phase dictates the burning rate. The pressure
dependence of the burning rate, however, becomes irregular in the range of 20–100 atm. This phenomenon may be attributed to
the competing influence of the condensed-phase and gas-phase exothermic reactions in determining the propellant surface conditions
and the associated burning rate.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 54–79, November–December, 2005. 相似文献
6.
The combustion wave structure and thermal decomposition process of azide polymer were studied to determine the parameters which control the burning rate. The azide polymer studied was glycidyl azide polymer (GAP) which contains energetic – N3 groups. GAP was cured with hexamethylene diisocyanate (HMDI) and crosslinked with trimethylolpropane (TMP) to formulate GAP propellant. From the experiments, it was found that the burning rate of GAP propellant is significantly high even though the adiabatic flame temperature of GAP propellant is lower than that of conventional solid propellants. The energy released at the burning surface of GAP propellant is caused by the scission of N N2 bond which produces gaseous N2. The heat flux transferred back from the gas phase to the burning surface is very small compared with the heat generated at the burning surface. The activation energy of the decomposition of the burning surface of GAP propellant, Es, is determined to be 87 kJ/mol. The burning rate is represented by r = 9.16 × 103 exp(–Es/RTs) where r (m/s) is burning rate, Ts (K) is the burning surface temperature, and R is the universal gas constant. The observed high temperature sensitivity of burning rate is correlated to the relationship of (∂Ts/∂T0)p = 0.481 at 5 MPa, where T0 is the initial propellant temperature. 相似文献
7.
M. B. Gonchikzhapov A. A. Paletsky A. G. Tereshchenko I. K. Shundrina L. V. Kuibida A. G. Shmakov O. P. Korobeinichev 《Combustion, Explosion, and Shock Waves》2016,52(3):260-272
The combustion of ultrahigh molecular weight polyethylene (UHMWPE) in airflow perpendicular to the polyethylene surface (counterflow flame) was studied in detail. The burning rate of pressed samples of UHMWPE was measured. The structure of the UHMWPE–air counterflow flame was first determined by mass spectrometric sampling taking into account heavy products. The composition of the main pyrolysis products was investigated by mass spectrometry, and the composition of heavy hydrocarbons (C7—C25) in products sampled from the flame at a distance of 0.8 mm from the UHMWPE surface was analyzed by gas-liquid chromatography mass-spectrometry. The temperature and concentration profiles of eight species (N2, O2, CO2, CO, H2O, C3H6, C4H6, and C6H6) and a hypothetical species with an average molecular weight of 258.7 g/mol, which simulates more than 50 C7—C25 hydrocarbons were measured. The structure of the diffusion flame of the model mixture of decomposition products of UHMWPE in air counterflow was simulated using the OPPDIF code from the CHEMKIN II software package. The simulation results are in good agreement with experimental data on combustion of UHMWPE. 相似文献
8.
V. P. Sinditskii 《Combustion, Explosion, and Shock Waves》2007,43(3):297-308
For model systems with known kinetics of elementary reactions (CH3NO2 and HN3), temperature ranges are established in which the rate-controlling reactions are the initial endothermic decomposition of
the starting material or the subsequent secondary reactions. Heat release in reactions of NO2, NO, and N2O with various fuels, such as CH2O, CO, H2, and HCN, is modeled to establish the kinetic parameters and nature of the rate-controlling reactions in gas flames of nitro
compounds. It is shown that the activation energy of the heat-release reaction due to the interaction of NO2 with a hydrocarbon fuel (which is characteristic of the first flame of nitro compounds) is in the range of 29–33 kcal/mole,
depending on the type of fuel. According to the calculations performed, the activation energy of the rate-controlling heat-releasing
process due to the deoxidation of NO and N2O (which is typical of the second flame of nitro compounds) is 43–58 kcal/mole. In the range of high pressures, where the
flames merge, the kinetic parameters of heat release are determined by the reactions of the most reactive nitrogen oxide NO2.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 3, pp. 59–71, May–June, 2007. 相似文献
9.
T. A. Bolshova A. A. Paletsky O. P. Korobeinichev V. D. Knyazev 《Combustion, Explosion, and Shock Waves》2014,50(1):10-24
A kinetic mechanism for combustion of hydrogen azide (HN3) comprising 61 reactions and 14 flame species (H2, H, N, NH, NH2, NNH, NH3, HN3, N3, N2H2, N2H3, N2H4, N2, and Ar) was developed and tested. The CHEMKIN software was used to calculate the flame speed at a pressure of 50 torr in mixtures of HN3 with various diluents (N2 and Ar), as well as the self-ignition parameters of HN3 (temperature and pressure) at a fixed ignition delay. The modeling results of the flame structure of HN3/N2 mixtures show that at a 25–100% concentration of HN3 in the mixture, the maximum temperature in the flame front is 25–940 K higher than the adiabatic temperature of the combustible mixture. Analysis of the mechanism shows that burning velocity of a HN3/N2 mixture at a pressure of 50 torr is described by the Zel’dovich-Frank-Kamenetskii theory under the assumption that the burn rate controlling reaction is HN3 + M = N2 + NH + M (M = HN3) provided that its rate constant is determined at a superadiabatic flame temperature. The developed mechanism can be used to describe the combustion and thermal decomposition of systems containing HN3. 相似文献
10.
The combustion wave structure and thermal decomposition process of HMX were examined in order to elucidate the burning rate characteristics of HMX. The combustion wave can be divided into three zones: nonreactive solid-phase, surface reaction, and gas-phase reaction zones. Measurements with micro-thermocouples revealed that the heat flux produced in the surface reaction zone is approximately equal to the heat flux transferred back from the gas phase to the burning surface. Accordingly, the reaction process in the suface reaction and the gas phase zones plays a dominant role in the burning rate of HMX. The gas phase reaction zone consists of a two-stage reaction process: the first stage is the exothermic rapid reaction process between NO2 and aldchydes, and the second stage is the exothermic slow reaction process between NO and N2O and remaining fuel species. The luminous flame zone which is determined to be the second stage reaction process approaches rapidly the burning surface as pressure increases. However, the luminous flame reaction appears to be little responsible for the burning rate of HMX. Examinations of the quenched burning surface of HMX samples revealed that the burning surface melts and forms a noncrystallized intermediate material. The surface structure appears to be different from the structure of thermally degraded HMX samples which were obtained by a thermogravnmetric analysis. 相似文献
11.
Maria Wojciechowska Mariusz Pietrowski Bogdan Czajka Sławomir Łomnicki 《Catalysis Letters》2003,85(3-4):153-157
The effect of water and reductants (CO and H2) on the decomposition of NO
x
stored on BaO/Al2O3 at 300 °C has been investigated. Water eliminates the initial rapid total uptake of NO2 but has little effect on the subsequent formation of nitrates that is accompanied by evolution of NO. Water hinders liberation of NO2 and NO during temperature-programmed decomposition of stored NO
x
. Both CO and H2 lower the temperatures required for decomposition through reduction of NO2 to NO and N2 thus restricting NO2 readsorption. The rate of reduction is lower with H2 than with CO. 相似文献
12.
The reaction of (NO + C3H8 + O2) can result in selective formation of NO2 over H-ZSM5, Cu,H-ZSM5, Ag,H-ZSM5, and Li,H-ZSM5 catalysts when the concentrations of NO and O2 are 0.1 and 9%, SV > 60,000 h−1 (typical for automotive exhausts), and C3H8/NO > 1. Despite stoichiometric excess of reductant hydrocarbon below this limit, the in situ formed NO2 does not react with C3H8, thus conversion of NO to N2 is negligible. NO can be reduced by C3H8 selectively to N2 only when C3H8/NO ≧ 1. Contrary to many suggestions the reaction temperature, concentration of oxygen, space velocity, and type of exchange
ions have minor influence on the selectivity for N2. These parameters affect the rates of reactions (NO + 2), (C3H8 + NOx) and (C3H8 + O2), therefore they also affect the production of N2 in the HC-SCR process, but only when the ratio of C3H8/NO permits. The metal-exchanged zeolites were prepared in situ by solid-state ion exchange from H-ZSM5. Despite the low degree
of copper exchange (63%), Cu,H-ZSM5 produces substantially more N2 than H-ZSM5, Ag,H-ZSM5, or Li,H-ZSM5. However, the selectivity for N2 is lowest over Cu,H-ZSM5, which also produces considerable NO2 in the reaction of (NO + C3H8 + O2) even at C3H8/NO ≧ 1. Contrary to prior findings, the catalytic activity of Cu,H-ZSM5 for the oxidation of NO by O2 to NO2 in absence of hydrocarbon was comparable to that of H-ZSM5 at high space velocities (2.3 l g−1 min−1). By replacing 30 and 40% of the protons of H-ZSM5 by Ag+ and Li+ ions in Ag,H-ZSM5 and Li,H-ZSM5, respectively, the catalytic activity for this reaction becomes negligible at temperatures
≧100°C. Some mechanistic consequences of these experimental observations are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
J. D. J. Nelson J. J. Schoenau S. S. Malhi K. S. Gill 《Nutrient Cycling in Agroecosystems》2007,78(3):291-303
Wetland fringe areas in prairie agricultural landscapes may be subjected to burning of vegetation in autumn followed by cultivation
in spring. The objective of this study was to examine the greenhouse gas (CO2, N2O and CH4) emissions and plant nutrient (NO3, PO4 and SO4) supplies in wetland fringe soils as affected by simulated burning + cultivation, at field capacity and saturation moisture
content. Using undisturbed soil cores collected from grassed wetland fringes at four sites in southern Saskatchewan, the impacts
were examined over a 20-day period. The burning + cultivation treatment generally reduced CO2 emissions, tended to increase NO3–N availability, and had no consistent effect on N2O emissions, or PO4–P and SO4–S supply. Production of CH4 occurred only at one site, and only under saturated conditions. Compared to field capacity, saturation reduced CO2 emissions and NO3–N supply, tended to increase PO4–P availability, and had no consistent effect on N2O emissions and SO4–S. The CO2 emissions and SO4–S were greater for soil cores with higher organic matter and salinity, respectively. The N2O emissions were only occasionally related to soil NO3–N supply rate. 相似文献
14.
Helmi Keskinen Jyrki M. Mäkelä Ritva Heikkinen Aslak Suopanki Jorma Keskinen 《Catalysis Letters》2007,119(1-2):172-178
Catalytic materials of alumina and lanthana supported nanosized palladium particles (7 wt%) in a water suspension were prepared
by Liquid Flame Spray (LFS) method. The particle production rate was 90 g/h, using liquid precursors containing Al(NO3)3 · 9H2O, La(NO3)3 · 6H2O and Pd(NH3)4NO3 in water solution. In the LFS method, a turbulent, high-temperature (Tmax ∼ 2,700 °C) H2–O2 flame is used. The liquid precursor is atomized into micron sized droplets by high velocity H2 flow and introduced into the flame where the droplets will evaporate. The evaporated compounds decompose and the reaction
product re-condenses into particulate material. Here, the nanosized particles are formed by gas-to-particle conversion and
the micron sized particles via liquid-to-solid route. In this study, the produced particulate material was collected by thermophoresis
along with condensing water into a suspension (nanoparticles in water) in a one-step process. Thus, the whole suspension was
produced from the end products of the flame. According to TEM-EDS analysis, the particulate material contained micron sized
porous aluminum oxide or lanthanum oxide carrier particles, coated by nanosized palladium particles (∼2–10 nm). The surfactant
(Rhodasurf-La 42) was injected into the suspension just after collection to reduce agglomeration. Catalytic performance of
the produced Pd–lanthana containing suspension was tested in laboratory with synthetic gases, in order to use it as a possible
raw material for three-way catalyst (TWC). The suspension was used as Pd raw material in TWC washcoat and dispersed onto a
metallic honeycomb. 相似文献
15.
16.
V. A. Bunev 《Combustion, Explosion, and Shock Waves》2009,45(3):251-257
The effect of the addition of nitric oxides (NO and NO2) on rich hydrogen-air flames was studied using the tracer method in numerical simulation. It is shown that the effects of
these additives are not similar. Both oxides promote the formation of OH and H2O in the low-temperature zone of the front. The addition of NO reduces the first maximum of the OH profile and the burning
velocity. The addition of NO2 increases the first maximum of the OH profile and does not change the burning velocity.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 3, pp. 19–25, May–June, 2009. 相似文献
17.
Naon Chang Huijun Won Sangyoon Park Heechul Eun Seonbyeong Kim Bumkyung Seo Yongsoo Kim 《International journal of molecular sciences》2021,22(14)
Radiolysis of chemical agents occurs during the decontamination of nuclear power plants. The γ-ray irradiation tests of the N2H4–Cu+–HNO3 solution, a decontamination agent, were performed to investigate the effect of Cu+ ion and HNO3 on N2H4 decomposition using a Co-60 high-dose irradiator. After the irradiation, the residues of N2H4 decomposition were analyzed by Ultraviolet-visible (UV) spectroscopy. NH4+ ions generated from N2H4 radiolysis were analyzed by ion chromatography. Based on the results, the decomposition mechanism of N2H4 in the N2H4–Cu+–HNO3 solution under γ-ray irradiation condition was derived. Cu+ ions form Cu+N2H4 complexes with N2H4, and then N2H4 is decomposed into intermediates. H+ ions and H● radicals generated from the reaction between H+ ion and eaq− increased the N2H4 decomposition reaction. NO3− ions promoted the N2H4 decomposition by providing additional reaction paths: (1) the reaction between NO3− ions and N2H4●+, and (2) the reaction between NO● radical, which is the radiolysis product of NO3− ion, and N2H5+. Finally, the radiolytic decomposition mechanism of N2H4 obtained in the N2H4–Cu+–HNO3 was schematically suggested. 相似文献
18.
《Applied catalysis. B, Environmental》2005,55(3):185-194
The temperature-programmed activity of a series of oxide-supported (TiO2, Al2O3 and SiO2) Cu catalysts formed from two different Cu precursors (Cu(NO3)2 and CuSO4) for the selective catalytic reduction of NOx using solutions of urea as a reductant have been determined. These activities are compared to those found using NH3 as a reducing agent over the same catalysts in the presence of H2O and it is found that catalysts that are active for the selective reduction of NOx with NH3 are inactive for its reduction using solutions of urea. Poisoning of the surface by H2Oads is not responsible for all of this decrease in activity and it is postulated that the urea is not hydrolysing to form NH3 over the catalysts but rather is oxidising to form N2 or forming passivated layers of polymeric melamine complexes on the surface. The catalysts were characterised by temperature-programmed reduction while temperature-programmed desorption and oxidation of NH3 and temperature programmed decomposition of urea are used to characterise the interaction of both reductants with the various catalysts. 相似文献
19.
The present paper reports the effects of N2 addition and preheating of reactants on bluff-body stabilized coaxial LPG jet diffusion flame for two cases, namely, (I)
preheated air and (II) preheated air and fuel. Experimental results confirm that N2 addition to the fuel stream leads to an enhancement in flame length, which may be attributed to the reduction in flame temperature.
The soot free length fraction (SFLF) also increases, which might be caused by the decrease in fuel concentration and flame
temperature. The flame length and also the SFLF are observed to be reduced with increasing temperature of reactants and lip
thickness of the bluff body. The NO
x
emission level for all burner configurations are found to be attenuated with nitrogen addition, which can be attributed to
the reduction of the residence time of the gas mixture in the flame. The emission index of NO
x
(EINO
x
) also becomes enhanced with increasing lip thickness and reactant temperature due to an increased residence time and thermal
effect, respectively.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 3–10, January–February, 2009. 相似文献
20.
Combustion Aspects of Sodium Azide and its mixtures with potassium perchlorate and burning catalysts
Linear burning rate, thermal aualysis, temperature profile, flame structure and cryogenic burnability for the mixtures of sodium azide (SA) of different particle sizes (3.5 μm, 22 μm, and 67 μm), potassium perchlorate (KP) and with or without three kinds of burning catalysts (GeO2, Er2O3, and Y2O3) have been investigated. The linear burning rates increase with the KP content up to 33Wt% for similar SA particle size. The temperature-time histories in the vicinity of burning surface were obtained with 20 μm Type K thermocouple embedded in a Strand. The burning surface temperaturres of neat SA and of the SA/KP mixtures are nearly 350°C and 350°C ∼ 550°C, respectively, while the existence of the decomposition surface at 250 °C and condensed layer was suggested with SA/KP mixtures. In visual observation for the flame structure, the front of luminous flame zone appers to be in contact with the condensed phase surface. For example, however, the temperature profile suggests that there exists finitc distance from decomposition surface to flame front in the order of 0.05 mm ∼ 0.1 mm at 1 MPa for SA/KP = 80/20. The differential thermal analysis indicates that the tested catalysts have retarding effect on SA combustion, but a positive effect on neat KP decomposition in spite of being impotent for the burning rate increase of the SA/KP mixture. It was also found that SA strands containing appropatiae fractions of KP can hurn even in liquid nitrogen. 相似文献