Features of ignition and combustion of a twocomponent gas suspension of coal particles
Physical and mathematical modeling of high-temperature heat and mass transfer and combustion kinetics of a two-fraction gas suspension of carbon particles at different gas temperatures is carried out. It was assumed that two parallel chemical reactions occur on the surface of the carbon particles:...
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nasplib_isofts_kiev_ua-123456789-1490582025-02-09T13:15:40Z Features of ignition and combustion of a twocomponent gas suspension of coal particles Особливості займання та горіння двокомпонентного газозавису вуглецевих частинок Особенности воспламенения и горения двухкомпонентной газовзвеси углеродных частиц Orlovskaya, S.G. Zuj, O.N. Chernyak, V.Ya. Низкотемпературная плазма и плазменные технологии Physical and mathematical modeling of high-temperature heat and mass transfer and combustion kinetics of a two-fraction gas suspension of carbon particles at different gas temperatures is carried out. It was assumed that two parallel chemical reactions occur on the surface of the carbon particles: C + O₂ = CO₂ (I), 2C + O₂ = 2CO (II). Molecular-conjugate heat exchange of particles with gas was taken into account, as well as heat exchange by radiation with the walls of the reaction apparatus. As a result of the numerical experiment, the characteristics of ignition and combustion of gas-suspension particles in air at various temperatures of the surrounding gas are determined. For calculations, a two-fraction gas suspension was chosen with equal mass fractions and particle diameters, which differ by a factor of 2: db₁ = 60 μm, db₂ = 120 μm. The range of the initial gas temperatures studied is 1100…1500 K. As a result of the calculations carried out, it was established that as the gas temperature decreases, the coarse fraction can ignite earlier than the fine fraction. At high gas temperatures, on the contrary: the induction period of fine particles is much larger than the period of induction of coarse particles. Critical parameters of ignition of two-fraction gases are found. The main characteristics of combustion are the time and temperature of combustion of the particles. It is proved that under the conditions of a two-fraction gas suspension the burning time of the particles depends weakly on the temperature of the gas. It has also been established that in the region of low gas temperatures, the combustion temperature of the fine fraction is smaller than that of the large fraction. This is explained by the large heat removal from small particles by the molecular-convective process and by the lack of oxidizer in the combustion stage. Oxygen is consumed in the combustion of large particles, which, at low temperatures, ignite earlier. The burning times of particles of coarse and fine fractions of a gas suspension were found. Comparison of the combustion time of small and large particles led to the conclusion that under the conditions of a gas suspension with an excess of an oxidizer close to unity, the particles burn in a diffusion mode. It is shown that the extinction of particles is degenerate. After the moment of extinction, the particles are oxidized in the kinetic regime at a high gas temperature. Проведено фізико-математичне моделювання високотемпературного тепломасообміну та кінетики горіння двофракційного газозавису вуглецевих частинок при різних температурах газу. Передбачалося, що на поверхні вуглецевих частинок протікають дві паралельні хімічні реакції: С+О₂=СО₂ (I), 2С+О₂=2СО (II). Враховувався молекулярно-конвективний теплообмін частинок з газом, а також теплообмін випромінювання зі стінками реакційної установки. В результаті проведеного чисельного експерименту визначені характеристики займання і горіння частинок газозавису в повітрі при різних температурах навколишнього газу. Для розрахунків вибирався двофракційний газозавис з рівними масовими концентраціями фракцій і діаметрами частинок, які відрізняються в 2 рази db₁ = 60 мкм, db₂ = 120 мкм. Діапазон досліджуваних початкових температур газу 1100…1500 К. В результаті проведених розрахунків встановлено, що при зменшенні температури газу частинки великої фракції можуть займатися раніше, ніж частинки дрібної фракції. При високих температурах газу навпаки: період індукції дрібних частинок значно перевищує період індукції частинок великої фракції. Знайдено критичні параметри займання двофракційного газозавису. Основними характеристиками горіння є час і температура горіння частинок. Доведено, що в умовах двофракційного газозавису час горіння частинок мало залежить від температури газу. Також встановлено, що в області низьких температур газу температура горіння частинок дрібної фракції менше, ніж великої. Це пояснюється великим тепловідводом від дрібних частинок молекулярноконвективним шляхом і недостачею окислювача на стадії горіння. Кисень витрачається на горіння великих частинок, які при низьких температурах спалахують раніше. Знайдено часи горіння частинок великої і дрібної фракцій газозавису. Проведено физико-математическое моделирование высокотемпературного тепломассообмена и кинетики горения двухфракционной газовзвеси углеродных частиц при различных температурах газа. Предполагалось, что на поверхности углеродных частиц протекают две параллельные химические реакции: С+О₂=СО₂ (I), 2С+О₂=2СО (II). Учитывался молекулярно-конвективный теплообмен частиц с газом, а также теплообмен излучения со стенками реакционной установки. В результате проведенного численного эксперимента определены характеристики воспламенения и горения частиц газовзвеси в воздухе при различных температурах окружающего газа. Для расчетов выбиралась двухфракционная газовзвесь с равными массовыми концентрациями фракций и диаметрами частиц, которые отличаются в 2 раза: db₁=60 мкм, db₂=120 мкм. Диапазон исследуемых начальных температур газа 1100…1500 К. В результате проведенных расчётов установлено, что при уменьшении температуры газа частицы крупной фракции могут воспламеняться раньше, чем частицы мелкой фракции. При высоких температурах газа наоборот: период индукции мелких частиц значительно превышает период индукции частиц крупной фракции. Найдены критические параметры воспламенения двухфракционных газовзвесей. Основными характеристиками горения являются время и температура горения частиц. Доказано, что в условиях двухфракционной газовзвеси время горения частиц слабо зависит от температуры газа. Также установлено, что в области низких температур газа температура горения частиц мелкой фракции меньше, чем крупной. Это объясняется большим теплоотводом от мелких частиц молекулярно-конвективным путем и недостатком окислителя на стадии горения. Кислород расходуется при горении крупных частиц, которые при низких температурах воспламеняются раньше. Найдены времена горения частиц крупной и мелкой фракций газовзвеси. 2018 Article Features of ignition and combustion of a twocomponent gas suspension of coal particles / S.G. Orlovskaya, O.N. Zuj, V.Ya. Chernyak // Вопросы атомной науки и техники. — 2018. — № 6. — С. 245-248. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 536.46 https://nasplib.isofts.kiev.ua/handle/123456789/149058 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
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| topic |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии |
| spellingShingle |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии Orlovskaya, S.G. Zuj, O.N. Chernyak, V.Ya. Features of ignition and combustion of a twocomponent gas suspension of coal particles Вопросы атомной науки и техники |
| description |
Physical and mathematical modeling of high-temperature heat and mass transfer and combustion kinetics of a
two-fraction gas suspension of carbon particles at different gas temperatures is carried out. It was assumed that two
parallel chemical reactions occur on the surface of the carbon particles: C + O₂ = CO₂ (I), 2C + O₂ = 2CO (II).
Molecular-conjugate heat exchange of particles with gas was taken into account, as well as heat exchange by
radiation with the walls of the reaction apparatus. As a result of the numerical experiment, the characteristics of
ignition and combustion of gas-suspension particles in air at various temperatures of the surrounding gas are
determined. For calculations, a two-fraction gas suspension was chosen with equal mass fractions and particle
diameters, which differ by a factor of 2: db₁ = 60 μm, db₂ = 120 μm. The range of the initial gas temperatures studied
is 1100…1500 K. As a result of the calculations carried out, it was established that as the gas temperature decreases,
the coarse fraction can ignite earlier than the fine fraction. At high gas temperatures, on the contrary: the induction
period of fine particles is much larger than the period of induction of coarse particles. Critical parameters of ignition
of two-fraction gases are found. The main characteristics of combustion are the time and temperature of combustion
of the particles. It is proved that under the conditions of a two-fraction gas suspension the burning time of the
particles depends weakly on the temperature of the gas. It has also been established that in the region of low gas
temperatures, the combustion temperature of the fine fraction is smaller than that of the large fraction. This is
explained by the large heat removal from small particles by the molecular-convective process and by the lack of
oxidizer in the combustion stage. Oxygen is consumed in the combustion of large particles, which, at low
temperatures, ignite earlier. The burning times of particles of coarse and fine fractions of a gas suspension were
found. Comparison of the combustion time of small and large particles led to the conclusion that under the
conditions of a gas suspension with an excess of an oxidizer close to unity, the particles burn in a diffusion mode. It
is shown that the extinction of particles is degenerate. After the moment of extinction, the particles are oxidized in
the kinetic regime at a high gas temperature. |
| format |
Article |
| author |
Orlovskaya, S.G. Zuj, O.N. Chernyak, V.Ya. |
| author_facet |
Orlovskaya, S.G. Zuj, O.N. Chernyak, V.Ya. |
| author_sort |
Orlovskaya, S.G. |
| title |
Features of ignition and combustion of a twocomponent gas suspension of coal particles |
| title_short |
Features of ignition and combustion of a twocomponent gas suspension of coal particles |
| title_full |
Features of ignition and combustion of a twocomponent gas suspension of coal particles |
| title_fullStr |
Features of ignition and combustion of a twocomponent gas suspension of coal particles |
| title_full_unstemmed |
Features of ignition and combustion of a twocomponent gas suspension of coal particles |
| title_sort |
features of ignition and combustion of a twocomponent gas suspension of coal particles |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2018 |
| topic_facet |
Низкотемпературная плазма и плазменные технологии |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/149058 |
| citation_txt |
Features of ignition and combustion of a twocomponent gas suspension of coal particles / S.G. Orlovskaya, O.N. Zuj, V.Ya. Chernyak // Вопросы атомной науки и техники. — 2018. — № 6. — С. 245-248. — Бібліогр.: 5 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-11-26T02:07:17Z |
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2025-11-26T02:07:17Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2018. №6(118)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2018, № 6. Series: Plasma Physics (118), p. 245-248. 245
FEATURES OF IGNITION AND COMBUSTION OF A TWO-
COMPONENT GAS SUSPENSION OF COAL PARTICLES
S.G. Orlovskaya1, O.N. Zuj1, V.Ya. Chernyak2
1Odessa National I.I. Mechnikov’s University, Odessa, Ukraine;
2Kyiv National Taras Shevchenko University, Kyiv, Ukraine
Physical and mathematical modeling of high-temperature heat and mass transfer and combustion kinetics of a
two-fraction gas suspension of carbon particles at different gas temperatures is carried out. It was assumed that two
parallel chemical reactions occur on the surface of the carbon particles: C + O2 = CO2 (I), 2C + O2 = 2CO (II).
Molecular-conjugate heat exchange of particles with gas was taken into account, as well as heat exchange by
radiation with the walls of the reaction apparatus. As a result of the numerical experiment, the characteristics of
ignition and combustion of gas-suspension particles in air at various temperatures of the surrounding gas are
determined. For calculations, a two-fraction gas suspension was chosen with equal mass fractions and particle
diameters, which differ by a factor of 2: db1 = 60 μm, db2 = 120 μm. The range of the initial gas temperatures studied
is 1100…1500 K. As a result of the calculations carried out, it was established that as the gas temperature decreases,
the coarse fraction can ignite earlier than the fine fraction. At high gas temperatures, on the contrary: the induction
period of fine particles is much larger than the period of induction of coarse particles. Critical parameters of ignition
of two-fraction gases are found. The main characteristics of combustion are the time and temperature of combustion
of the particles. It is proved that under the conditions of a two-fraction gas suspension the burning time of the
particles depends weakly on the temperature of the gas. It has also been established that in the region of low gas
temperatures, the combustion temperature of the fine fraction is smaller than that of the large fraction. This is
explained by the large heat removal from small particles by the molecular-convective process and by the lack of
oxidizer in the combustion stage. Oxygen is consumed in the combustion of large particles, which, at low
temperatures, ignite earlier. The burning times of particles of coarse and fine fractions of a gas suspension were
found. Comparison of the combustion time of small and large particles led to the conclusion that under the
conditions of a gas suspension with an excess of an oxidizer close to unity, the particles burn in a diffusion mode. It
is shown that the extinction of particles is degenerate. After the moment of extinction, the particles are oxidized in
the kinetic regime at a high gas temperature.
PACS: 536.46
1. PHYSICO-MATHEMATICAL MODELING
The use of plasma processes to activate the
combustion of pulverized coal dictates the need to
clarify the patterns of coal combustion in a high-
temperature gaseous oxidant. The fuel used for
combustion in power plants has a polydisperse
composition. The particle size and their concentration in
the gas suspension affect the heat and mass exchange
rate with the oxidant gas and the plant walls [1].
Two fraction dust-air mixture is a simplest case of
polydisperse suspension. So the purpose of this work is
to study the characteristics of ignition and combustion
of a two-fraction suspension of carbon particles in air at
different temperatures. The main characteristics of fuels
combustion are the ignition delay (induction period), the
burning temperature and time, critical parameters
(temperature, the particles diameters and mass
concentrations), corresponding to fuel ignition and
extinction.
The physico-mathematical model of high-
temperature heat and mass transfer of carbon particles-
gas suspension includes the differential equations of
thermal and mass balances for the particles of each
fraction and the corresponding equations for oxidizing
gas [2, 3].
When particles hit a heated oxidizer, chemical
reactions begin to occur on their surfaces and in the
pores, as a result of which, the particles ignite and burn.
The total density of chemical heat release for a particle
of the i-th fraction as a result of surface and internal
reaction with two parallel reactions (С+О2=СО2 (I),
2С+О2=2СО (II)), we find from the expression [2]:
ii
vi
iiis,Ogiiich
kk
k
KKnqkqkq
21
22211 , 1
(1),
ichq – the total density of chemical heat release at the
surface and in the pores of the particle, ii k,k 21 – the rate
constants of chemical reactions (I) and (II), 21 q,q –
thermal effects of chemical reactions (I) and (II), g –
gas density, is,On
2
– the relative mass concentration of
oxygen on the surface of the carbon particle,
iK – the
ratio of the constants of the internal and surface
responses,
vik
– effective internal reaction constant [3].
In the combustion chamber, molecular-convective
( iq ) and radiant heat exchange (
iwq ) of particles with
heated gas and with walls of the reaction volume occurs.
The densities of these flows can be found from the
equations:
sfiii qqq
, )TT(q giii
,
(2)
246 ISSN 1562-6016. ВАНТ. 2018. №6(118)
i
g
i
d
uN
.
)TT(q wiiw
44
. (3)
Where iq – is the component of the heat flux
density due to molecular-convective heat transfer, qsfi –
component of the heat flux density due to the Stefan
flow nt [4], i – coefficient of heat exchange of a
particle with a gas,
wi T,T,T g – respectively, the
temperature of the particle, gas and walls of the reaction
chamber,
g – coefficient of thermal conductivity of
gas,
id – particle diameter.
Let us write the heat and mass balance equations for a
particle of the i-th fraction:
ibiwiiich
iii T)t(T,qqq
t
Tdc
0
6
,
(4)
,dtd,nkk
M
M
W,W
t
d
ibigis,Oii
O
C
isis
i
i
02
2
1
221
2
(5)
.t,KW
t
d
ibiiis
i
i
0
6
1 (6)
Here c – specific heat of the particle; ρi – particle
density; t – time; CM ,
2OM – molar masses of carbon
and oxygen, respectively.
When burning pulverized coal suspended in the reaction
volume, over time, the temperature of the gas and the
concentration of oxygen change. Equations of heat and
mass balances for gas with allowance for external heat
and mass transfer have the form:
)TT(FqCS
t
T
c ggggiNi
n
i
g
gg
i
1
,
gg TtT )0( ,
(7)
,)0(
),()(
,
,21,
1
22
222
2
OgO
gOOggviiisOiN
n
i
gO
ntn
nnFkkknSC
t
n
ii
(8)
where
gс – the specific heat of the gas;
iS – the surface
area of the particle; gF
– the specific surface of the gas
suspension; g,On
2
– the relative mass concentration of
oxygen in the gas; g ,
g – the coefficients of heat
exchange and mass transfer of the gas suspension with
the surrounding medium; iNC – the numerical
concentration of particles of the i-th fraction, which is
related to the mass concentration of carbon fuel
relationship:
iNiiim CdС 3
6
1 ,
.CС
n
1i
mm i
2. CALCULATION RESULTS AND
DISCUSSION
Let us calculate the ignition and combustion of a
two-fraction gas suspension of carbon particles with
particle diameters that differ by several times and equal
to the mass concentrations of the fractions.
Fig. 1 shows the time dependences of the
temperatures and particle diameters of each of the
fractions, the gas temperature in the combustion of a
slurry with initial particle diameters:
1bd = 60 μm (fine
fraction) and
2bd =120 μm (coarse fraction) for different
initial gas temperatures. The initial mass concentration
of carbon fuel in the gas suspension was
Сmb = 0.016 kg/m3, the mass concentrations of each
fraction were:
1Сmb = 2Сmb = 0.008 kg/m3. The gas
suspension data are loose and are characterized by an
excess oxygen factor of 1.5.
Fig. 1. Dependences of T, Tg, d on time. a, b:
wg TT
=1450 K; c, d
wg TT
=1350 K.
1 –
1bd =60 μm; 2 –
2bd =120 μm;
3 – gas temperature
gT
The points I and E in (see Fig. 1) characterize,
respectively, the moments of ignition and extinction of
the particles. The time from the start of warming up to
point I determines the period of induction (tind), and
from point I to point E – the burning time (tbur) of the
particles. The diameter of the particles in the
combustion stage (see Fig. 1,b,d) decreases rapidly until
the moment of extinction (p.E). At this point, there is a
decrease in the rates of chemical reactions on the
surface of the carbon particles, which is characterized
by a fracture in the dependences d(t). As follows from
the figures, after the moment of extinction, the particle
diameter continues to decrease, but at a slower rate.
Oxidation of the particle takes place in the kinetic
regime. Consequently, in contrast to single particles, the
attenuation of the particles of a gas suspension is
degenerate. Analysis of the dependences d(t) makes it
ISSN 1562-6016. ВАНТ. 2018. №6(118) 247
possible to determine the time of the complete
transformation of the particles.
Analysis of the temperature curves shows that at a
high gas temperature, ignition and burnup of the fine
fraction first occurs (see Fig. 1,a,b). Particles of coarse
fraction ignite shortly before the extinction of fine
particles. During the burnout of the fine fraction, the
oxygen concentration decreases substantially, so that
combustion and subsequent combustion of the coarse
fraction occur at low values. At a lower gas temperature
(Fig. 1,c,d), larger particles ignite earlier (curves 2).
According to formulas (2), fine particles have a higher
heat transfer coefficient α, which leads to an increase in
the heat flux density qα. Therefore, the increase in the
ignition time of the fine fraction in comparison with the
coarse fraction is explained by the increase in the heat
flux from particles of small dimensions with a decrease
in the gas temperature. In this case, the time of the
chemical component of the induction period greatly
increases [5].
At a certain critical gas temperature (ignition
temperature) Tcr (Fig. 2), the gas suspension is not
ignited. The critical ignition temperature of a two-
fraction gas suspension is significantly lower than the
ignition temperature of single particles of the same
diameter. Moreover, the critical ignition temperatures
for single large and small particles are significantly
different, and under conditions of a two-fraction gas
suspension practically coincide.
Fig. 2. Dependences of the induction period of the
gas suspension from the initial gas temperature:
1 – db1=60 μm; 2 – db2=120 μm
Let us analyze the burning characteristics of a two-
fraction gas suspension. It can be seen from Fig. 3,a that
the burning time of the fine and coarse fractions of the
gas suspension depends only slightly on the temperature
of the gas. The burning time of the coarse fraction is
almost 4 times that of the fine fraction with a ratio of
their initial diameters db1/db2=2. This indicates that the
combustion of particles under gas-suspension conditions
occurs in the diffusion regime.
The combustion temperature of fine particles in the
region of low gas temperatures is less than the burning
temperature of large particles (see Fig. 3,b). This is due
to two reasons: a large heat loss to the gas by a
molecular-convective route and a lack of an oxidizer at
the stage of burning of small particles. A significant
decrease in the concentration of the oxidant occurs as a
result of its intensive consumption by burning large
particles that ignited earlier (see Fig. 1,с).
Fig. 3. Dependences of the burning time (a) and the
maximum burning temperature (b) of the particles on
the gas temperature: 1 – db1=60 μm; 2 – db2=120 μm
CONCLUSIONS
It has been established that at gas temperatures
above 1400 K, the ignition delay time (induction period)
of a two-fraction gas suspension is determined by the
ignition time of the fine fraction, below this value by the
ignition time of the coarse fraction. For example, for a
gas temperature of 1500 K, the induction period of fine
particles (fraction of 60 μm) is half the time of induction
of large particles (fraction of 120 μm). At gas
temperatures below 1400 K, the induction period of the
fine fraction is larger than that of the large fraction, and
this difference increases with decreasing gas
temperature. This is due to the increase in heat loss by
molecular convection to the surrounding gas
environment for the fine fraction.
The ignition temperatures of the two-fraction gases
are found. The critical temperature of ignition of
particles in the gas suspension is significantly lower
than for single particles of the same diameter. The
lowering of the ignition temperature of the gas
suspension is due to the heating of the gas due to the
heat of chemical reactions during the oxidation of the
aggregate of particles. Moreover, for large and small
single carbon particles, the critical gas temperatures
differ substantially, and under conditions of a two-
fraction gas suspension, they practically coincide.
The temperature range of the ambient gas and the
walls of the reaction unit is determined, for which the
combustion temperature of the fine particles is less than
that of the coarse fraction of the gas suspension. So for
gas temperatures above 1300 K, the combustion of the
fine fraction occurs at higher temperatures. It is found
that for a gas temperature of 1500 K, the combustion
temperature of fine particles is more than 200 degrees
higher than the burning temperature of large particles of
a gas suspension. Unlike single particles, the gas-
suspension damping proceeds in a degenerate regime,
since the temperature difference between the particles
and the gas is small. In this case, the oxidation of
particles of the gas suspension takes place in the kinetic
regime, which makes it possible to estimate the time of
their complete conversion.
248 ISSN 1562-6016. ВАНТ. 2018. №6(118)
REFERENCES
1. V.V. Pomerantsev. Fundamentals of the practical
theory of combustion. Leningrad: “Energia”, 1973.
2. S.G. Orlovska. Investigation of the regularities of
combustion of gas suspensions of carbon particles //
Physics and Chemistry of Solid State. 2015, v. 16, № 1,
p. 210-216.
3. S.G. Orlovskaya, V.V. Kalinchak, O.N. Zuy. Effect
of an internal reaction on the characteristics of high-
temperature heat and mass transfer of gas suspensions
of carbon particles // High Temperature. 2014, v. 52,
№ 5, p. 716-723.
4. V.V. Kalinchak, S.G. Orlovskaya, A.I. Kalinchak,
A.V. Dubinskiy. Heat and mass exchange of a carbon
particle with air, taking into account the Stefan flow and
heat losses by radiation // Thermophysics of High
Temperatures. 1996, v. 34, № 1, p. 83-91.
5. S.G. Orlovskaya, V.V. Kalinchak, O.N. Zuj,
M.V. Liseanskaia. Study of ignition and combustion of
two-fraction coal-air suspension // Ukr. J. Phys. 2018,
v. 63, № 4, p. 370-375.
Article received 15.09.2018
ОСОБЕННОСТИ ВОСПЛАМЕНЕНИЯ И ГОРЕНИЯ ДВУХКОМПОНЕНТНОЙ ГАЗОВЗВЕСИ
УГЛЕРОДНЫХ ЧАСТИЦ
С.Г. Орловская, О.Н. Зуй, В.Я. Черняк
Проведено физико-математическое моделирование высокотемпературного тепломассообмена и кинетики
горения двухфракционной газовзвеси углеродных частиц при различных температурах газа.
Предполагалось, что на поверхности углеродных частиц протекают две параллельные химические реакции:
С+О2=СО2 (I), 2С+О2=2СО (II). Учитывался молекулярно-конвективный теплообмен частиц с газом, а
также теплообмен излучения со стенками реакционной установки. В результате проведенного численного
эксперимента определены характеристики воспламенения и горения частиц газовзвеси в воздухе при
различных температурах окружающего газа. Для расчетов выбиралась двухфракционная газовзвесь с
равными массовыми концентрациями фракций и диаметрами частиц, которые отличаются в 2 раза:
db1=60 мкм, db2=120 мкм. Диапазон исследуемых начальных температур газа 1100…1500 К. В результате
проведенных расчётов установлено, что при уменьшении температуры газа частицы крупной фракции могут
воспламеняться раньше, чем частицы мелкой фракции. При высоких температурах газа наоборот: период
индукции мелких частиц значительно превышает период индукции частиц крупной фракции. Найдены
критические параметры воспламенения двухфракционных газовзвесей. Основными характеристиками
горения являются время и температура горения частиц. Доказано, что в условиях двухфракционной
газовзвеси время горения частиц слабо зависит от температуры газа. Также установлено, что в области
низких температур газа температура горения частиц мелкой фракции меньше, чем крупной. Это объясняется
большим теплоотводом от мелких частиц молекулярно-конвективным путем и недостатком окислителя на
стадии горения. Кислород расходуется при горении крупных частиц, которые при низких температурах
воспламеняются раньше. Найдены времена горения частиц крупной и мелкой фракций газовзвеси.
ОСОБЛИВОСТІ ЗАЙМАННЯ ТА ГОРІННЯ ДВОКОМПОНЕНТНОГО ГАЗОЗАВИСУ
ВУГЛЕЦЕВИХ ЧАСТИНОК
С.Г. Орловська, О.Н. Зуй, В.Я. Черняк
Проведено фізико-математичне моделювання високотемпературного тепломасообміну та кінетики
горіння двофракційного газозавису вуглецевих частинок при різних температурах газу. Передбачалося, що
на поверхні вуглецевих частинок протікають дві паралельні хімічні реакції: С+О2=СО2 (I), 2С+О2=2СО (II).
Враховувався молекулярно-конвективний теплообмін частинок з газом, а також теплообмін
випромінювання зі стінками реакційної установки. В результаті проведеного чисельного експерименту
визначені характеристики займання і горіння частинок газозавису в повітрі при різних температурах
навколишнього газу. Для розрахунків вибирався двофракційний газозавис з рівними масовими
концентраціями фракцій і діаметрами частинок, які відрізняються в 2 рази db1 = 60 мкм, db2 = 120 мкм.
Діапазон досліджуваних початкових температур газу 1100…1500 К. В результаті проведених розрахунків
встановлено, що при зменшенні температури газу частинки великої фракції можуть займатися раніше, ніж
частинки дрібної фракції. При високих температурах газу навпаки: період індукції дрібних частинок значно
перевищує період індукції частинок великої фракції. Знайдено критичні параметри займання
двофракційного газозавису. Основними характеристиками горіння є час і температура горіння частинок.
Доведено, що в умовах двофракційного газозавису час горіння частинок мало залежить від температури
газу. Також встановлено, що в області низьких температур газу температура горіння частинок дрібної
фракції менше, ніж великої. Це пояснюється великим тепловідводом від дрібних частинок молекулярно-
конвективним шляхом і недостачею окислювача на стадії горіння. Кисень витрачається на горіння великих
частинок, які при низьких температурах спалахують раніше. Знайдено часи горіння частинок великої і
дрібної фракцій газозавису.
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