B. S. Seplyarskii, R. A. Kochetkov, T. G. Lisina
Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Russia
Keywords: SHS, combustion models, powder mixtures, titanium particle size, granules, impurity gas release.
For the first time, experimental dependences of the combustion rate of powder and granular mixtures 5Ti + 3Si, Ti + Cam, (Ti + Cam) + 20% Cu, (Ti + Cam) + 20% Ni, Ti + Ccr (with amorphous carbon in the form of soot and crystalline carbon in the form of graphite) on the size of titanium particles are discussed using different models of combustion front propagation in a condensed medium. The theory of gasless combustion (taking into account the mechanism of capillary spreading and without it), microheterogeneous models do not even qualitatively explain the difference in the dependences of the combustion rate on the size of titanium particles for powder mixtures of titanium with soot and with graphite or the increase in the combustion rate of powder mixtures Ti + Cam when diluted with nickel and copper, accompanied by a decrease in combustion temperature. Changing the structure of the medium – granulation of powder mixtures – leads to a change in the combustion rate without changing the phase composition of the synthesis products. Within the framework of the convective-conductive combustion model, all these results are explained uniformly by the inhibitory influence of impurity gases released ahead of the combustion front in powder mixtures when the conditions for heating the component particles are met. The influence of impurity gas release on the combustion rate of powder mixtures can be assessed for each composition by the difference in the combustion rates of granular and powder samples. For all studied compositions of granular mixtures, where the influence of impurity gases on the combustion rate is leveled, the analytical approximation of the experimental dependence of the combustion rate on the size of titanium particles showed qualitative agreement with the dependence that follows from the convective-conductive combustion model.
A. A. Syrovaten, I. A. Bedarev, D. A. Tropin
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: ignition, combustion, boron particles, PSU combustion model of boron, numerical simulation
A physico-mathematical model and a computational method have been developed to model the ignition and combustion of a suspension of boron particles in an oxidizer gas behind shock waves of varying intensity. Calculations were carried out for particles with a diameter of 1-20 μm at their volumetric concentrations m2 = 10-4 and 10-5, corresponding to a lightly dusty medium. Oxygen and a mixture of oxygen and water vapor at a mass concentration of water vapor of 10- 90% were considered as an oxidizer. The the structure of combustion waves was examined, and the behavior of the main parameters of the gas and particles was described. The influence of water vapor on the ignition delay time and burning time of boron particles was analyzed. The results were compared with experimental data available in the literature, and agreement on the ignition delay time at a surrounding gas temperature of 2200-3000 K was obtained.
A. M. Astakhov1, D. B. Lempert2 1Reshetnev Siberian State University of Science and Technology, Krasnoyarsk, Russia 2Federal Research Center for Problems of Chemical Physics and Medical Chemistry, Russian Academy of Sciences, Chernogolovka, Russia
Keywords: nitrohydrazine, ammonium dinitramide, solid composite propellant, specific impulse, effective impulse, combustion temperature, two-phase impulse loss
The energy capabilities of a hypothetical zwitterionic nitrohydrazine H3N+N-NO2 as a component of solid composite propellants are estimated. Two-component compositions with a hydrocarbon or active binder and three-component compositions with the addition of aluminum or aluminum hydride are considered. Compositions with an active binder and aluminum hydride show the highest calculated ballistic efficiency. Their specific impulse exceeds 280 s, and with allowance for two-phase losses, the maximum effective impulse of the third stage rocket motor, it reaches 265.4 s, whereas for an optimized similar composition based on ammonium dinitramide, this value is significantly lower (262.5 s).
A. A. Kotomin, S. A. Dushenok, A. S. Kozlov
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Keywords: solid explosives, liquid explosives, mixtures and solutions of explosives, nitromethane, suspensions, detonability, critical detonation diameter, specific surface
The detonability of mixtures of solid and liquid explosives (explosive suspensions) has been little studied, although they are part of plastisol and paste explosive compositions widely used in practice. In this work, the critical detonation diameters of suspensions of PETN, RDX, HMX, and FOX-7 os various dispersion (specific surface area 350-7000 cm2/g) in nitromethane. The content of crystalline explosives in suspensions was 3-60 wt.%. Suspensions were prepared using a vibrovacuum method. The sedimentation stability and homogeneity of suspensions was ensured by their thickening with a small addition of aerosil (2.0-2.5%). Charges of suspensions were prepared in thin-walled polyethyleneterephthalate tubes of various diameter. Thus, the critical detonation diameter of explosive suspensions was determined in fact for charges without a shell. The dependences of the critical detonation diameter of suspensions on the volume fraction of solid explosives have the same S-shaped form. The effect of the dispersion of explosives on these dependences was shown. Obtained dependences for suspensions of solid explosives in nitromethane were compared with similar experimental dependences for other explosive systems: solutions of liquid explosives in nitromethane; solutions of solid explosives in nitromethane; binary mixtures of finely dispersed solid explosives; binary mixtures of coarsely and finely dispersed explosives; compositions containing mixtures of coarsely and finely dispersed explosives and inert binder. It is shown that the dependences for binary mixtures of coarsely and micron-size explosives and compositions based on these mixtures (distinct heterogeneous systems) the same form as for suspensions.
Y.-H. Liu1,2, L. Bao3,4, H.-Z. Wang3,4, B.-Q. Xin1,2, A.-F. Yu3,4, C.-T. Ge1,2 1SINOPEC Research Institute of Safety Engineering Co., Qingdao, China 2SINOPEC National Petrochemical Project Risk Assessment Technical Center Co., Ltd, Qingdao, China 3SINOPEC Research Institute of Safety Engineering Co., Ltd, Qingdao, China 4State Key Laboratory of Safety and Control for Chemicals, Qingdao, China
Keywords: hydrogenation unit, hydrogen cloud explosion, FLACS, flame propagation law, antiknock engineering transformation
During the operation of a hydrogenation unit, there is the danger of leakage and explosion of high-pressure hydrogen. In order to study the evolution of the flame and shock wave in hydrogen explosion accidents, the explosion process and the impact range of hydrogen leakage in the hydrogenation unit are simulated based on the FLACS simulation software. First, we have established a high-precision three-dimensional physical model for the hydrogenation unit and investigated the influence of different equivalence ratio (ER) on the overpressure of the hydrogen cloud explosion. The result shows that, at ER= 0.8-1.4, the peak temperature, flame propagation velocity, and overpressure peak value generated by the hydrogen cloud explosion increase first and then decrease with an increase in the equivalence ratio. At ER = 1.05, the peak temperature and overpressure after the explosion have the largest values, and the flame propagation velocity at this time is 38.2 and 31.7% higher than that at ER = 0.8 and 1.4, respectively. At the same time, flame acceleration during its propagation can effectively promote an increase in the explosion overpressure inside the flame. In addition, the simulation results of this paper also provide theoretical guidance for the antiknock engineering transformation of chemical plant buildings.
A. A. Vasil'ev1,2, V. A. Vasiliev1 1Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia
Keywords: hydrogen power engineering, explosion hazard, ignition delay, kinetic data on detonation, fuel-oxygen mixture (FOM), fuel-air mixture (FAM)
A large pool of data on the detonation hazard of hydrogen in mixtures with oxygen and air in the range of concentrations from the lean to rich limit with variations of the initial pressure and temperature (individually or jointly) are reported. The most important parameter is the critical energy of detonation initiation, which serves as a measure of the explosion hazard of combustible systems: the smaller the value of this parameter, the more hazardous the mixture. The number of reliable measurements of the critical energy of detonation initiation in scientific publications is rather limited (which is even more true for waves with different symmetries) owing both to difficulties in measuring this parameter and to imperfection of mathematical models of energy transfer from the external booster to the combustible mixture.
A. A. Vasil'ev1,2, V. A. Vasiliev1 1Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia
Keywords: hydrogen power engineering, safety of atomic power plants, ignition delay, kinetic data on detonation, fuel-oxygen mixture (FOM), fuel-air mixture (FAM)
A large pool of data on the detonation hazard of hydrogen in mixtures with oxygen and air additionally diluted by inert gases and in the presence of steam in the mixture are reported. The most important parameter is the critical energy of detonation initiation, which serves as a measure of the explosion hazard of combustible systems: the smaller the critical energy, the more hazardous the mixture. The number of reliable measurements of the critical energy of detonation initiation in scientific publications is rather limited (which is even more true for waves with different symmetries).
T. A. Khmel, S. A. Lavruk
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: hybrid detonation, hydrogen-oxygen mixture, aluminum particles, cellular structures, numerical modeling
A physical and mathematical model of hybrid detonation in a mixture of hydrogen - oxygen - argon with additives of microdispersed aluminum particles is presented. The combustion of hydrogen and aluminum is described within the framework of the given kinetics. The combustion reaction of aluminum takes into account the formation of suboxides and particles of solid aluminum oxide. Using numerical simulation methods of two-dimensional flows in a flat channel 10 cm wide, the processes of formation and propagation of cellular detonation in a mixture of 0.72H2 + O2 + 2.58Ar at an initial pressure of 0.26 atm with additions of aluminum particles of size 3.5 were studied. and 5 μm. The properties of regularization and reduction of cell size, an increase in front velocity, peak pressures and temperatures in the hybrid mixture in comparison with gas detonation have been established. Two-front regimes have been obtained that exist for a limited time. After the fronts merge, detonation accelerates and transitions to a fine-cell structure. The relationship between cell size and average detonation velocity is similar to the formula for overcompressed gas detonation.
F. A. Bykovskii, S. A. Zhdan, E. F. Vedernikov
Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: continuous multifront detonation, fuel-water emulsions, kerosene, hot air, transverse detonation waves, annular combustor
Regimes of continuous multifront detonation of a fuel-water emulsion (kerosene TS-1 - water) mixed with hot air preheated by a firing method in the settling chamber from 600 to 1200 K in a flow-type annular combustor 503 mm in diameter are obtained and studied. Regimes with one and two pairs of colliding waves are observed in the range of specific flow rates of air through the slot 600-1400 kg/(s·m2) for the equivalence ratio varied from 0.53 to 1.0. The frequency of rotation of transverse detonation waves is 1.0 ± 0.1 kHz for one pair of detonation waves and 2.4 ± 0.2 kHz for two pairs of detonation waves. For air temperatures up to 800 K, the limits of regimes of continuous multifront detonation are determined in terms of the mass fraction of water in kerosene: 0.38-0.53. It is shown that an increase in the water content in the fuel-water emulsion reduces the degree of dissociation of detonation products. At high air temperatures (1200 К), the specific impulse increases and approaches 2150 s if the impulse of cold species (with no combustion) is taken into account.
E. S. Prokhorov
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: explosion, detonation, chemical equilibrium, gas suspension, carbon, coal
This paper presents the results of calculation of the detonation of a homogeneous gas suspension of ultrafine carbon particles with an oxidizer (oxygen or air) assuming chemical equilibrium in the products of detonation combustion. The influence of the mass fraction of carbon in such mixtures on the velocity of the detonation front and the main gas-dynamic parameters of combustion products was studied numerically. The calculation results correlate with available experimental data on detonation velocity in a suspension of coal particles in oxygen and air.
