共查询到20条相似文献,搜索用时 15 毫秒
1.
Mathematical modeling of the stripping of combustible forest materials by explosion of a cord charge
The stripping of combustible forest materials (thin twigs and needles) by explosion of a cord charge are studied by mathematical
modeling of blast-wave propagation in a forest canopy for the placement of the cord charge at different heights. The calculation
results allow one to reduce the consumption of explosives in extinguishing crown forest fires.
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Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 3, pp. 92–99, May–June, 2006. 相似文献
2.
A. M. Grishin A. N. Golovanov L. Yu. Kataeva E. L. Loboda 《Combustion, Explosion, and Shock Waves》2001,37(1):57-66
The drying of combustible forest materials is the most important and least studied stage of the multiphase process of their burning under natural conditions. Physical and mathematical modeling of the drying of a layer of combustible forest materials is performed in a conjugate formulation by solving the equations of a binary boundary layer and the equations of heat and mass transfer in a layer of combustible forest materials with corresponding boundary and initial conditions. Solutions of this problem for diurnal and seasonal changes in environmental temperature are obtained for three scenarios of development of weather conditions. The data obtained are compared with experimental data on drying of needles of pine and some other coniferous trees. A rigorous physicomathematical basis for prediction of forest fires is given. 相似文献
3.
Relying on the laws of the mechanics of multiphase reacting media, we construct a mathematical model of the ignition of forests
by radiation emitted as a result of the explosion of the Tungusskii meteorite. The forest canopy is modelled by a multiphase
porous reacting medium. The ignition regimes realized at different distances from the center of the explosion are analyzed.
It has been established that the maximum radius of the ignition zone is 6–9 km for the forest canopy and 12–16 km for the
ground cover, depending on the stock and moisture content of combustible forest materials. This corresponds to an explosion
energy of 25·1016 J.
V. V. Kuibyshev Tomsk State University, Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 8–14, November–December,
1993. 相似文献
4.
A. P. Golub’ 《Combustion, Explosion, and Shock Waves》2006,42(4):456-462
A mathematical modeling study demonstrated the fundamental possibility of the formation of a heated layer (a meter-long layer
of erosion vapor and air with temperatures of a few thousand degrees and a density 20–50 times lower than the normal air density)
at the ground surface under the action of the long-distance traveling fireball radiation from an intense explosion at a moderate
radiant flux density of about 1 GW/m2 for a time of about 10 msec. The results of the numerical study agree with data from observations of the heated layer effect
in nuclear-weapon tests.
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Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 100–106, July–August, 2006. 相似文献
5.
Results are presented for experimental studies of the thermal conductivity of expanded vermiculite. Tests are performed in
an experimental test unit by a steady-state heat flux. Thermal studies are carried out in the range 300–1100 K. It is shown
that thermal conductivity increases uniformly with an increase in temperature. The most probable reason for an increase in
thermal conductivity is the effect of heat radiation. Results are provided for an approximate second power polynomial.
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Translated from Novye Ogneupory, No. 11, pp. 41–43, November 2007. 相似文献
6.
A. M. Grishin A. A. Dolgov V. P. Zima D. A. Kryuchkov V. V. Reino A. N. Subbotin R. Sh. Tsvyk 《Combustion, Explosion, and Shock Waves》1998,34(6):613-620
Theoretical and experimental studies of the ignition of forest combustible materials by real ignition sources, which are modeled
by a reference source, are reported. The time of ignition by the reference source is determined. The critical ignition energy
is estimated, and its variation under real conditions is analyzed.
Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 6, pp. 14–22, November–December 1998.
The paper is reported at the 2nd International Conference on Forest Fires (Irkutsk, 10–15 June, 1997). 相似文献
7.
V. I. Besshaposhnikova S. E. Artemenko L. G. Panova T. V. Kulikova O. A. Grishina V. A. Shteinle M. V. Zagoruiko 《Fibre Chemistry》2008,40(1):61-65
A method of giving flameproof properties to materials and articles in light industry by modification with phosphorus-containing
flame retardants under the effect of the energy from CO2 laser radiation was developed. The optimum modification parameters (LR power density of 5.3 W/cm2, treatment time of 30 sec, concentration of flame retardant (FR) in 5–10% solution, impregnation time of 100–120 sec), which
allow obtaining flameproof materials with high performance properties were determined. The oxygen index of the cloth increased
to 29.5–42%, the breaking strength increased by 8.5–21%, and the abrasion resistance increased by 5–12% without worsening
the hygroscopicity and air permeability. The activating effect of laser radiation on the modification process was demonstrated;
it resulted in an increase in the sorption capacity of the fibre structure of the materials, diffusion of FR into the bulk
of the fibres, uniform distribution of the fibres in the form of finely disperse particles, intensification of the reaction
of the components, ordering of the structure, and improvement in the physicomechanical properties of materials and articles
in light industry. The method saves on expensive raw materials — flame retardants — due to conducting the modification from
low-concentration solutions and allows expanding the line of flameproof materials.
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Translated from Khimicheskie Volokna, No. 1, pp. 48–52, January–February, 2008. 相似文献
8.
A. V. Dedov 《Fibre Chemistry》2007,39(5):397-399
Incorporation of a bicomponent fibre in needle-punch materials and then treating them with heat by different methods results
in a significant increase in their compressive strength. The compressive strength of needle-punch and modified materials is
a function of the size and orientation of the fibre bundles. Increasing the needle-punching density does not significantly
increase the compressive strength of the materials.
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Translated from Khimicheskie Volokna, No. 5, pp. 34–36, September–October, 2007. 相似文献
9.
A. M. Grishin V. P. Zima V. T. Kuznetsov A. I. Skorik 《Combustion, Explosion, and Shock Waves》2002,38(1):24-29
The paper reports results of experimental ignition of litter layers consisting of needles of cedar, pine, and fir-tree, birch leaves, lichen (Cladonia), and moss (Pleurozium shreberi). It is established that the moss is ignited faster than the other combustible forest materials. It is shown that with equal moisture contents, the ignition times of needle litter from different trees are identical within the experimental error, and for litter of birch leaves, the ignition time is shorter than that for litter of coniferous trees. This difference is found to be due to differences in the interaction of the radiant flux with litter layers of needles and leaves. Minimum values of the ignition heat pulses for needle and leaf litter layers are estimated for various heat-flux densities. These values tend to a minimum for a heat-flux density of 0.5–0.8 MW/m2. 相似文献
10.
11.
Flame propagation in chlorine-containing combustible systems under ignition by a constant light beam
I. R. Begishev V. A. Poluéktov G. M. Makhviladze 《Combustion, Explosion, and Shock Waves》1998,34(1):1-5
The action of the light emission of a mercury—quartz lamp on combustible mixtures of chlorine and difluoromethane and hydrogen
at atmospheric pressure increases the upper concentration limit of flame propagation and flame velocity in mixtures similar
in concentration to the upper concentration limit, because, during flame propagation in these mixtures, the rates of the thermal
and photochemical dissociation of chlorine molecules are comparable, and the chlorine concentration behind the flame front
is minimum.
Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 1, pp. 3–8, January–February, 1998. 相似文献
12.
A. N. Golovanov 《Combustion, Explosion, and Shock Waves》1999,35(3):275-280
Experiments indicate that the thermochemical decomposition of composite materials is sensitive to small periodic perturbations
in the external flux and to wall vibrations. Stable, unstable, and self-oscillatory combustion regimes are found for these
materials, and limiting conditions for the binder concentration and vibration intensity are determined for which it is possible
to reduce thermal loads to the wall and control heat and mass transfer. Monostationarty and stability boundaries are constructed
and the results are compared with theory.
Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 3, pp. 67–73, May–June 1999. 相似文献
13.
V. V. Medvedev 《Combustion, Explosion, and Shock Waves》2008,44(5):583-585
Abstact Initiation of slightly compacted powders of lead azide of density not greater than 1.2 g/cm3 by laser radiation with a wavelength of 1.06 μm was studied experimentally over a wide range of pulse lengths (10−5–10−3 sec). It is shown that the ignition threshold of the slightly compacted samples does not change as the laser pulse length
is increased. It is found that the explosion products contain molten lead particles whose sizes are an order of magnitude
larger than the sizes of similar particles from explosion of samples of density 4.0 g/cm3.
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Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 98–100, September–October, 2008. 相似文献
14.
Curing of filled systems previously treated with UV radiation is a first-order process with respect to the oligomers that
takes place in the diffusion region. The slowing effect of viscose fibres in the initial stage of curing increases the impact
strength of the reinforced material. The UV radiation increases the probability of linear chain growth during curing and results
in material with a high average weight of crosslinked chains. UV treatment increases the impact strength and static bending
breaking stress by 20–50% in comparison to materials obtained without irradiation and is an effective method of modification.
The polymer reinforcement decreases the density and increases the strength characteristics of concrete articles in comparison
to unreinforced concrete.
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Translated from Khimicheskie Volokna, No. 1, pp. 45–48, January–February, 2008. 相似文献
15.
Yu. I. Babenko 《Combustion, Explosion, and Shock Waves》2006,42(2):144-148
A method is proposed to determine the moment of ignition of a semi-infinite massif of a condensed material exposed to an external
heat flux specified as an arbitrary function of time. The method uses the fractional-differentiation formalism. For large
values of the heat flux, the calculation results coincide with the results obtained using well-known methods.
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Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 23–28, March–April, 2006. 相似文献
16.
V. G. Prokof’ev A. V. Pisklov V. K. Smolyakov 《Combustion, Explosion, and Shock Waves》2007,43(1):56-61
The effect of a heat-conducting element on the ignition and combustion of a cylindrical layer of a gasless mixture with a
nonadiabatic lateral surface is studied. It is shown that the introduction of an element with high heat conductivity allows
one to extend the region of ignition of the gasless composition by a heated surface and to increase burning rate under conditions
of external heat release.
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Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 66–71, January–February, 2007. 相似文献
17.
This paper demonstrates the successful use of an infrared pyrometer, operating in the 8–10 µm wavelength band, to measure the surface temperature of combustible specimens in a heat release calorimeter. The temperature histories of ten different materials were measured in the ICAL (intermediate scale calorimeter). The set of materials comprised four wood products, gypsum board, polyisocyanurate foam, PVC floor tile, PMMA and two non‐combustible boards. A small‐diameter bare thermocouple was installed on each specimen in order to determine an accurate temperature for comparison. The spectral emissivity and the spectral flux reflected from the surface were measured simultaneously and used to correct the apparent temperature measured by the pyrometer. The spectral emissivity and reflected spectral flux were both constant prior to ignition for all the combustible materials. During the burning phase all the combustible materials had a spectral emissivity very close to unity. The agreement between the temperatures measured with the pyrometer and thermocouple was not affected by the flame. The wood products, the polyisocyanurate foam and the calcium silicate board required no correction for reflected spectral flux over the whole temperature range. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
The studies demonstrated the possibility of practical implementation of a method of fabricating difficultly combustible polyethylene
by incorporating chlorinated paraffin stabilized with CaCO3 and fireproof fibres in the polymer. The PCM based on the modified polyethylene have high physicomechanical characteristics
and low combustibility, which places them in the class of construction materials for engineering and technical applications.
Engels Engineering Institute, Saratov State Engineering University. Translated fromKhimicheskie Volokna, No. 6, pp. 46–49, November–December, 1999. 相似文献
19.
The possibility of obtaining high-melting fibre materials from plant fibres and textile production wastes containing 40–60
wt. % cellulose was demonstrated. The optimum conditions of preliminary chemical treatment of natural raw material to increase
the sorption capacity of the materials were determined. The conditions of heat treatment of salt-containing natural fibre
materials which would allow regulating the crystal and pore structure of oxide fibres were established.
Translated from Khimicheskie Volokna, No. 5, pp. 27–31, September–October, 1997. 相似文献
20.
Temperature profiles and combustion-wave parameters are obtained experimentally for combustion of pressed HMX at room temperature
and pressures of 1–500 atm and in the case of a change in the initial temperature of the specimens from −170 to +100°C at
pressures of 1–75 (90) atm. The following combustion-zone parameters are determined: the heat effect in the c-phase, the heat
transfer from the gas to the c-phase by thermal conduction and radiation, the rate of heat release in the gas near the surface,
and the dimensions and temperature of the combustion zones. The authorsé previous conclusion that there is one process of
decomposition and evaporation of HMX during its gasification in the condensed-phase reaction layer of the combustion wave
is confirmed. Dependences of the fraction of decomposed HMX on the initial temperature of the specimens and the pressure are
obtained. The differential characteristics of the combustion rate, surface temperature, and radiative heat transfer, required
for the nonlinear theory of HMX combustion stability, are evaluated.
Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 2, pp. 59–66, March–April, 1998. 相似文献