a quasi-discrete model for droplet heating and evaporation ... · ahmed elwardany supervised by:...
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The Sir Harry Ricardo Laboratories-Centre for Automotive Engineering,
University of Brighton, UK.
Research workshop: Droplets and Sprays: modelling and experimentation 13th January 2012
A quasi-discrete model for droplet heating and evaporation: application to
Diesel and gasoline fuels Presented by:
Ahmed Elwardany Supervised by: Prof. Sergei Sazhin Prof. Morgan Heikal
Ø Introduction
Ø Concept of quasi-component
Ø Thermophysical properties of n-alkanes
Ø Preliminary results for Diesel fuel
Ø Advanced results for Diesel and gasoline fuels
Ø Conclusions
Plan
Multi-component Models
Models applicable for Small number of components
(DCM)
Models applicable for Large number of components
(CT or Distillation Curve)
Introduction Ø Models for multi-component droplets can be subdivided
into two groups:
Ø Most of these models assume that the species diffusivity
within the droplet is assumed to be infinitely large or small
while each component has its own volatility.
Concept of quasi-discrete model
Ø The model is based on the assumption that the
components can be described as CnH2n+2 (n-alkanes).
Ø The model is based on replacing a large number of actual
components with a small number of quasi-components.
Ø These quasi-components are then treated as actual
components, taking into account the diffusion of quasi-
components in droplets.
Concept of quasi-discrete model
Concept of quasi-discrete model
0
0.04
0.08
0.12
0.16
0.2
5 10 15 20 25
diesel
gasoline
n
f m(n
)
Diesel gasoline
n1 n2 n3 n4
Concept of quasi-discrete model
Ø The initial mole fraction of each quasi-component is
calculated as:
Ø where are the molecular weights, ,
, is Gamma function, and α, β, γ are
parameters that determine the shape of the distribution and
the original shift.
Concept of quasi-discrete model
Ø Following Arias-Zugasti and Rosner (2003), we
assumed that: , and (Diesel Fuel)
and (gasoline fuel)
Ø The choice of assures that:
Ø Each quasi-component carbon atoms estimated as:
Concept of quasi-discrete model
Thermophysical properties of n-alkanes
11
• Critical and Boiling Temperatures
Following Poling et al (2000), the dependence of critical and
boiling temperatures on number of carbon atoms n:
where the constants are:
Coef%icient a b c d
Critical 242.3059898052 55.9186659144 - 2.1883720897 0.0353374481
Boiling 118.3723701848 44.9138126355 - 1.4047483216 0.0201382787
Poling B.E., Prausnitz J.M. and O’Connell J., (2000), The Properties of Gases and Liquids, New York: McGraw-Hill.
12
• Critical and Boiling Temperatures
300
400
500
600
700
800
5 10 15 20 25
Tcr (K)
check_Tcr
Tb (K)
check Tb
T (K
)
values of Tcr approximation for Tcr values of Tb approximation for Tb
n
13
• Saturation pressure and Latent heat of vaporization
Following Arias-Zugasti and Rosner (2003) the saturation
pressure of n-alkanes (n = 4-17).
where , and
Latent heat:
where
,
Arias-Zugasti M, Rosner DE. Multicomponent fuel droplet vaporization and combustion using spectral theory for a continuous mixture. Combustion and Flame 2003;135:271-284.
14
• Liquid Density
Following Yaws (2008), the dependence of liquid density on
number of carbon atoms n and temperature (n = 5-25):
The values of , and are approximated as follows:
Yaws C.L., (2008), Thermophysical properties of chemicals and hydrocarbons, William Andrew.
15
• Liquid Density
300
400
500
600
700
800
900
5 10 15 20 25
T = 300 K
approximation - T = 300 K
T = 450 K
approximation - T = 450 K
n
dens
ity (k
g/m
3 )
16
• Liquid Viscosity
Following Mehrotra (1994), the dependence of liquid viscosity
on number of carbon atoms n and temperature (n = 4-44):
where
Mehrotra A.K. (1994), Correlation and prediction of the viscosity of pure hydrocarbon, The Canadian Journal of Chemical Engineering, (72) 554-557.
17
• Liquid Viscosity
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
5 10 15 20 25
T =300 K approximation - T = 300 K T= 450 K approximation - T = 450 K
n
visc
osity
(Pa.
s)
The approximations are reproduced using the equation suggested by Mehrotra (1994). The symbols are reproduced from http://webbook.nist.gov/chemistry/
18
• Liquid Heat Capacity
Following van Miltenburg (2000), the dependence of liquid
heat capacity on number of carbon atoms n and temperature
(n = 2-26):
van Miltenburg J.C.(2000), Fitting the heat capacity of liquid n-alkanes: new measurements of n-heptadecane and n-octadecane, Thermochimica Acta (343) 57-62.
19
• Liquid Heat Capacity
2000
2200
2400
2600
2800
5 7 9 11 13 15 17 19 21 23 25
T =300 K approximation - T = 300 K approximation - T = 450 K
n
heat
cap
acity
(J/k
g.K
)
The data of n-heptadecane and n-octadecane (triangles) reproduced from van Miltenburg (2000), the other data (squares) reproduced from http://webbook.nist.gov/chemistry/.
20
• Liquid Thermal Conductivity
Following Yaws (1995), the dependence of liquid thermal
conductivity on number of carbon atoms n and temperature (n
= 5-20):
where
Yaws C.L., (1995), Handbook of thermal conductivity, Vol (2): Organic compounds, C5 to C7 and Vol (3): Organic compounds, C8 to C28. Gulf Publishing Company, Houston, Texas, USA.
21
• Liquid Thermal Conductivity
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
5 10 15 20 25
T = 300 K approximation - T = 300 K T = 450 K approximation - T = 450 K
n
ther
mal
con
duct
ivity
(W/m
.K)
Hollow symbols are reproduced from http://webbook.nist.gov/chemistry/. Solid Symbols are reproduced form Yaws (1995) using the corresponding values of the constants.
Preliminary results
Diesel Results
Pg =3 Mpa, Rd =10 µm, Ud =1 m/s,Tg = 880 K, Td,initial = 300 K
0
2
4
6
8
10
12
300
400
500
600
700
800
0 0.25 0.5 0.75 1 1.25 1.5
Ts_n=1 Ts_n=10 Ts-n=20,ITC
Time (ms)
T s (K
) Rd (µm
)
One quasi-component-ETC/ED Twenty quasi-components-ETC/ED Twenty quasi-components-ITC/ID
Diesel Results
450
460
470
480
0 5 10 15 20
Ts-ETC-ED Ts-ITC_ID ETC/ED model ITC/ID model
Time = 0.25 ms
Number of quasi-components
T s (K
)
(a)
9.925
9.95
9.975
10
0 5 10 15 20
Rd-ETC-ED Rd-ITC_ID ETC/ED model ITC/ID model
Time = 0.25 ms
Number of quasi-components
Rd (µm
)
(b)
Diesel Results
605
610
615
620
625
0 5 10 15 20
Ts-ETC-ED
ETC/ED model ITC/ID model
Time = 1 ms
T s (K
)
Number of quasi-components
(a)
6.8
7
7.2
7.4
7.6
0 5 10 15 20
Rd-ETC-ED Rd-ITC_ID ETC/ED model ITC/ID model
Time = 1 ms
Rd (µ
m)
Number of quasi-components
(b)
Advanced results
Diesel Results
0
2
4
6
8
10
12
300
400
500
600
700
800
0 0.4 0.8 1.2 1.6
Ts_n=1 Ts_n=10 Ts-n=20,ITC Ts_old
Time (ms)
T s (K
) Rd (µm
)
One quasi-component-ETC/ED Twenty quasi-components-ETC/ED Twenty quasi-components-ITC/ID Twenty quasi-components-ETC/ED (n-dodecane)
Diesel fuel
Pg =3 Mpa, Rd =10 µm, Ud =1 m/s,Tg = 880 K, Td,initial = 300 K
Diesel Results
537
539
541
543
0 4 8 12 16 20
ETC, ED models ITC, ID models
Time =0.5 ms
Number of quasi-components
T s (K
)
(a)
ETC/ED model ITC/ID model
9.55
9.6
9.65
9.7
0 4 8 12 16 20
ETC, ED models ITC, ID models
Time =0.5 ms
Number of quasi-components
Rd (µ
m)
(b)
ETC/ED model ITC/ID model
Diesel Results
600
610
620
630
0 4 8 12 16 20
ETC, ED models ITC, ID models
Time =1 ms
Number of quasi-components
T s (K
)
(a)
ETC/ED model ITC/ID model
6.9
7.1
7.3
7.5
7.7
0 4 8 12 16 20
ETC, ED models ITC, ID models Time =1 ms
Number of quasi-components
Rd (µ
m)
(b)
ETC/ED model ITC/ID model
30
Gasoline Results
Pg =3 bar, Rd =10 µm, Ud =10 m/s,Tg = 450 K, Td,initial = 300 K
0
2
4
6
8
10
12
300
350
400
450
500
0 2 4 6 8
Ts_n=1 Ts_n=10 Ts-n=20,ITC
Time (ms)
T s (K
) Rd (µm
)
One quasi-component-ETC/ED Thirteen quasi-components-ETC/ED Thirteen quasi-components-ITC/ID
Gasoline Results
330
335
340
345
350
0 3 6 9 12
ETC, ED models ITC, ID models
Time =0.5 ms
Number of quasi-components
T s (K
)
(a)
ETC/ED model ITC/ID model
9.25
9.3
9.35
9.4
9.45
9.5
0 3 6 9 12
ETC, ED models ITC, ID models
Time =0.5 ms
Number of quasi-components
Rd (µ
m)
(b) ETC/ED model ITC/ID model
Gasoline Results
340
360
380
400
0 3 6 9 12
ETC, ED models ITC, ID models Time =2 ms
Number of quasi-components
T s (K
)
(a)
ETC/ED model ITC/ID model
5.6
5.8
6
6.2
6.4
6.6
6.8
7
0 3 6 9 12
ETC, ED models ITC, ID models Time =2 ms
Number of quasi-components
Rd (µ
m)
(b)
ETC/ED model ITC/ID model
Suggested composition for Diesel and gasoline fuels
Gasoline Fuel Diesel Fuel 60% C6H14 10% C8H18
30% C9H20 57% C12H26
8% C12H26 29% C16H34
3% C15H32 4% C21H44
Conclusions
Ø A new quasi-discrete model for multi-component droplets heating and evaporation, applicable for large number of components, has been developed. Ø This model takes into account the effect of heat and mass diffusion within the droplet and it takes into account the dependence of the thermophysical properties of the fuel on the number of carbon atoms and temperature.
Ø We applied this model for Diesel and gasoline fuels.
Ø Diesel and Gasoline fuels could be presented by a mixture of only four quasi-components.
• Kristyadi T., Deprédurand V., Castanet G., Lemoine F., Sazhin S.S., Elwardany A., Sazhina E.M. and Heikal M.R. (2010), Monodisperse monocomponent fuel droplet heating and evaporation, Fuel 89 (2010) 3995–4001. • Sazhin S.S., Elwardany A.E., Krutitskii P.A., Castanet G., Lemoine F., Sazhina E.M. and Heikal M.R. (2010), A simplified model for bi-component droplet heating and evaporation, Int. J. Heat Mass Transfer 53, 4495–4505.
• Abdelghaffar, W.A., Elwardany, A.E., Sazhin, S.S. (2011), Modelling of the processes in Diesel engine-like conditions: effects of fuel heating and evaporation, Atomization and Sprays, 53(13-14), 2826-2836.
• Sazhin S.S., Elwardany A.E., Krutitskii P.A., Deprédurand V., Castanet G., Lemoine F., Sazhina E.M., Heikal M.R. (2011), Multi-component droplet heating and evaporation: numerical simulation versus experimental data, Int. J. Thermal Sciences, 50(2011) 1164-1180. • Sazhin S.S., Elwardany A.E., Sazhina E.M., Heikal M.R. (2011), A quasi-discrete model for heating and evaporation of complex multicomponent hydrocarbons fuel droplets, Int. J. Heat Mass Transfer 54, 19-20, 4325-4332.
Publications: International Journals
Thank you
Ahmed Elwardany The Sir Harry Ricardo Laboratories-Centre for Automotive Engineering,
University of Brighton, UK.
Research workshop: Droplets and Sprays: modelling and experimentation 13th January 2012