A numerical investigation of methanol droplet combustion in a zero-gravity and low-pressure convective environment is presented. Simulations have been carried out using a predictive, transient and axisymmetric model, which includes droplet heating, liquid-phase circulation and water absorption. First, a suspended droplet (constant relative velocity) burning in an ambient of air at 300K is considered. A nearly quiescent environment (initial Reynolds number Re0=0.01) is used to impose a weak gas-phase convective flow, introducing a deviation from spherical symmetry. The resulting weak liquid-phase circulation is greatly enhanced due to surface tension effects, which create a complex, time-varying, multicellular flow pattern within the liquid droplet. The complex flow pattern, which, in the presence of surface tension, results in nearly perfect mixing, causes increased water absorption within the droplet, leading to larger extinction diameters. Surface tension effects are shown to be dominant in causing water absorption, even at initial Reynolds numbers as high as 5. Results for combustion in a nearly quiescent environment (Re0=0.01) with varying initial droplet diameters, (d0 = 0.16 to 1.72 mm), show that predictions of droplet extinction diameters, although they are still below the experimental data, do improve substantially when surface tension effects are included. Next, results for suspended droplets and for moving droplets burning in an ambient of air at 1200K, for a range of initial Reynolds numbers that are of interest in spray combustion (Re0=1-100) are presented. It is shown that, for moving droplets, due to the presence of an envelope flame at some stage during the droplet lifetime, surface tension is important over the entire range of Re0 considered; the extinction diameter decreases with increasing Re0. Extinction is not observed for a moving droplet when surface tension effects are neglected. For suspended droplets, when transition or envelope flame is present, which corresponds to Re0 less than approximately 15, surface tension is important; when an envelope flame is present (Re0 less than approximately 10), the extinction diameter increases with Re0. The variation of droplet lifetime with Re0 is much stronger for suspended droplets than for moving droplets. Depending on the Reynolds number, results on methanol droplet lifetimes and extinction diameters measured through suspended droplet experiments may not be applicable to moving droplets.

1.
Yang
J. C.
,
Jackson
G. S.
, and
Avedisian
C. T.
,
Proc. Combust. Inst.
,
23
(
1990
)
1619
1625
.
2.
Cho
S. Y.
,
Choi
M. Y.
, and
Dryer
F. L.
,
Proc. Combust. Inst.
,
23
(
1990
)
1611
1617
.
3.
Lee
and
Law
C. K.
,
Combust. Sci. Tech.
,
86
(
1992
)
235
265
.
4.
Marchese
A. J.
,
Dryer
F. L.
,
Colantonio
R. O.
, and
Nayagam
V.
,
Proc. Combust. Inst.
,
26
(
1996
)
1209
1217
.
5.
Choi
M. Y.
,
Cho
S. Y.
,
Dryer
F. L.
, and
Haggard
J. B.
,
Eastern States Section Meeting
,
The Combustion Institute, Albany NY
, Paper No.
73
(
1989
)
1
4
.
6.
Dietrich
D. L.
,
Haggard
J. B.
,
Dryer
F. L.
,
Nayagam
V.
,
Shaw
B. D.
, and
Williams
F. A.
,
Proc. Combust. Inst.
,
26
(
1996
)
1201
1207
.
7.
Okai
K.
,
Moriue
O.
,
Araki
M.
,
Tsue
M.
,
Kono
M.
,
Sato
J.
,
Dietrich
D. L.
, and
Williams
F. A.
,
Combust. Flame
,
121
(
2000
)
501
512
.
8.
Hara
H.
, and
Kumagai
S.
,
Proc. Combust. Inst.
,
25
(
1994
)
423
430
.
9.
Shaw
B. D
,
Combust. Flame
,
81
(
1990
)
277
288
.
10.
Zhang
B. L
,
Card
J. M.
, and
Williams
F. A.
,
Combust. Flame
,
105
(
1996
)
267
290
.
11.
Marchese
A. J.
, and
Dryer
F. L.
,
Combust. Flame
,
105
(
1996
)
104
122
.
12.
Spalding
D. B.
,
Fuel
,
32
(
1953
),
169
185
.
13.
Gollahalli
S. R.
, and
Brzustowski
T. A.
,
Proc. Combust. Inst.
,
15
(
1975
)
409
417
.
14.
Sami
H.
, and
Ogasawara
M.
,
JSME. Bulletin
,
13
(
1970
)
395
404
.
15.
Raghavan
V.
,
Babu
V.
,
Sundararajan
T.
, and
Natarajan
R.
,
Int. Journal of Heat and Mass Transfer
,
48
(
2005
)
5354
5370
.
16.
Okajima
S.
, and
Kumagai
S.
,
Proc. Combust. Inst.
,
19
(
1982
)
1021
1027
.
17.
Nayagam, V., Hicks, M. C., Ackerman, M., Haggard, J. B. Jr. and Williams, F. A., Seventh International Microgravity Combustion Workshop, NASA CP-2003–212376 (2003) 157–160.
18.
Gokalp
I.
,
Chauveau
C.
,
Richard
J. R.
,
Kramer
M.
and
Leuckel
W.
,
Proc. Combust. Inst.
,
22
(
1988
)
2027
2035
.
19.
Okajima
S.
and
Kumagai
S.
,
Proc. Combust. Inst.
,
15
(
1975
)
401
407
.
20.
Dwyer
H. A.
, and
Sanders
B. R.
,
Proc. Combust. Inst.
,
22
(
1988
)
1923
1929
.
21.
Aharon
I.
and
Shaw
B. D.
,
Physics of Fluids
,
8
(
1996
)
1820
1827
.
22.
Dwyer
H. A.
,
Aharon
I.
,
Shaw
B. D.
and
Niazmand
H.
,
Proc. Combust. Inst.
,
26
(
1996
)
1613
1619
.
23.
Dwyer
H. A.
,
Shaw
B. D.
and
Niazmand
H.
,
Proc. Combust. Inst.
,
27
(
1998
)
1951
1957
.
24.
Dwyer
H. A.
and
Shaw
B. D.
,
Comb. Sci. and Tech.
,
162
(
2001
)
331
346
.
25.
Shih
A. T.
, and
Megaridis
C. M.
,
Int. Journal of Heat and Mass Transfer
,
39
(
2)
(
1996
)
247
257
.
26.
Pope
D. N.
and
Gogos
G.
,
Numerical Heat transfer, Part B
,
48
(
2005
)
213
233
.
27.
Pope
D. N.
and
Gogos
G.
,
Combust. Flame
,
142
(
2005
)
89
106
.
28.
Pope
D. N.
,
Howard
D.
,
Lu
K.
and
Gogos
G.
,
AIAA J. of Thermo. Heat Trans.
,
19
(
3)
(
2005
)
273
281
.
29.
Raghavan
V.
,
Pope
D. N.
,
Howard
D.
and
Gogos
G.
,
Combust. Flame
,
145
, (
2006
)
791
807
.
30.
Kurihara
K.
,
Nakamichi
M.
and
Kojima
K.
, “
Isobaric vapor-liquid equilibria for the methanol + ethanol + water and the three constituent binary systems
,”
American Chemical Engineering Society
, Vol.
38
,
1993
, pp.
446
449
.
31.
Reid, R. C., Prausnitz, J. M. and Poling, B. E., The Properties of Gases and Liquids, McGraw-Hill Inc., New York, 1987.
32.
McBride, B. J., Sanford, G. and Reno, M. A., “Coefficients for calculating thermodynamic and transport properties of individual species,” NASA Tech. Memorandum 4513, 1993.
33.
Teja
A. S.
, “
Simple method for the calculation of heat capacities of liquid mixtures
,”
American Chemical Engineering Society
, Vol.
28
,
1983
, pp.
83
85
.
34.
Teja
A. S.
and
Rice
P.
, “
Generalized corresponding states method for the viscosities of liquid mixtures
,”
Industrial Engineering Chemical Fundamentals
, Vol.
20
,
1981
, pp.
77
81
.
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