Research Reports of Nagaoka National College of Technology, Vol.48, 2012

Paper

Kinematic Viscosity of Mechanically Emulsified
Gas Oil
Hiroki ISHIDA
Department of Electronic Control Engineering, Nagaoka National College of Technology

Kinematic viscosity of the emulsified Gas oil, produced mechanically by a gear pump typemechanical emulsifier, was examined. The effects of some conditions for emulsification; thetemperature, the content of water and the revolution of driving gear of the emulsifier, on the kinematic
viscosity were studied experimentally. The present study revealed some important dependence of thekinematic viscosity on the running conditions of the gear pump type mechanical emulsifier. The
kinematic viscosity increases with increases in the water content and in the gear revolution, but
decreases with increase in the temperature of emulsion.

Key Words: W/O type emulsion, gear pump mechanism, kinematic viscosity, Gas oil

1. Introduction
In the recent several years, as same as in overabout thirty years ago, the technology of applicationof emulsion fuels to many boilers, furnaces anddiesel engines has attracted much attention from thepoint of view of the energy saving and of theprevention of atmospheric pollution caused by theexhaust from many combustion facilities. It is,mainly, due to the recent high cost of crude oil andto the prevalence of the national consensus of theprotection of environment.
The kind of emulsion fuels, consisting of usual
petroleum fuels and water, is divided into two types;
W/O and O/W emulsions. W/O type emulsion fuelhas dispersed many fine water particles in the basepetroleum fuel. On the other hand, O/W typeemulsion fuel has, inversely, dispersed many finepetroleum fuel particles in the water phase.
Many excellent studies on the combustion ofemulsified petroleum fuels in furnaces have beenreported experimentally1-4,8-17,21-23,25-32,34,37,38,41) andtheoretically 5-7,11,35).㩷 From the point of view of fire
hazard prevention also, some studies have reported
the pool burning characteristics of emulsified

petroleum fuels10,15, 18-20, 24, 36). An excellent review
by Kadota and Yamasaki has reported the recent
advances of the study on the emulsion combustion40).
In the recent decade, some studies have reported the
new technology for the emulsification of
miscellaneous fuels33,39,41,42).
Since over twenty years ago, Nakayama has
devised and improved successfully an excellent
mechanical emulsification device using a gearpumping mechanism consisting of some specified
gears, which is described in his patent43). Thismechanical emulsification device gives a strong
shear stress to the mixture of water and petroleum
fuel in the squish among the rotating gears and in
the clearance between the gears and surrounding
housing wall. Water particles are thereby strongly
ground and mixed with base petroleum fuel, andsome of them become extremely fine (less thanabout 10㱘m in diameter), which cannot be attainedby the usual mechanical methods of mixing,
atomizing or both. This mechanical emulsification
device has enabled also the new recycling fueltechnology for some waste oils (from machine andfood) in boilers and many combustion furnaces.
Our previous paper has reported some important― 13 ―

Hiroki Ishida

performance of the gear pump type emulsification
device including the stability of emulsions of Gas
oil and A-heavy oil44,45). Now the kinematic
viscosity of emulsified fuel also is an important
property for the characteristics of sprayed fuel jet
into many combustion furnaces. In general, thedecrease in the kinematic viscosity of fuel leads tothe wide-angle spray area and the short length offuel jet from the exit of nozzle. On the other hand,
the increase in the kinematic viscosity of fuel leads
to the long length of fuel jet from the exit of nozzle
although the spray area angle will decrease. The
present study reports the kinematic viscosity of theemulsified Gas oil, produced by the gear pump typemechanical emulsifier44,45).

Fig.2

The side view of mechanical emulsifier (3 Gearstype) used in this study.

2. Gear Pump Type Emulsifier
The concept and the outline of the three gears
pump type mechanical emulsifier used in this study
are described in our previous paper44). Figures 1
and 2 show the top and the side views of the present
gear pump type emulsifier, where the first gear isdriven directly by a motor at 300~1300 rpm. Thisemulsifier has a series of 3 gears: the diameters ofgear tip circle and pitch circle; 27.5~22.5 mm and25~20 mm respectively, the numbers of teeth;
20~16, the modules of gears; 1.25~1.23, the teeth
length in the axis direction of gears; 40 mm. The
clearance between the gear tip and the housing wall;
0.05 mm for the first gear, 0.5 mm at one side of thesecond gear, about 0.15 mm at one side of the thirdgear and about 0.4 mm at the opposed side of thethird gear. Owing to the very strong shear stress inthe wider clearances around the second and the thirdgears, the fuel and water are mixed and emulsified.

Fig.3

Scheme of the water injection (Velocity: Vw ) from thefine exit of nozzle to the first gear for the emulsification.

Fig.4 Schematic model of the emulsification region in theclearance between the gear teeth and the housing wall.

Fig.5
Fig.1

The scheme of top view of mechanical emulsifier(3 Gears type) used in this study.

― 14 ―

Representative photograph of emulsified Gas oil(Water: 9 vol.% for Fuel, 800 rpm).

Kinematic Viscosity of Mechanically Emulsified Gas Oil

In the present mechanical emulsifier, water istransported by water pump and injected at highspeed (9~13 m/s) from the fine exit hole (0.7 mm india.) nozzle toward the first gear aiming to enhancethe emulsification effect, as shown in Fig.3.
Figure 4 shows the schematic model of
emulsification region in the wider clearance(Emulsification Path shown in Fig.1) between thegear tip and the housing wall. In this wider
clearance the mixture of fuel and water istransferred (by the pressure due to the revolution of
the first gear) in the opposite direction to therevolution of the second gear.
Although the theoretical explanation of thisemulsification mechanism is not easy and cannot begiven in the present stage, it should be noted that
there is no other region for the emulsification except
this wider clearance, where the very strong shear
stress exists. We can expect thereby that the increasein the revolution of gear will enhance the stability ofemulsion.
A typical W/O emulsified Gas oil is shown in
Fig.5, where the water content is about 9 vol.% for
Gas oil. As shown in this photograph, the color ofW/O type emulsified Gas oil become whitish
compared with that of the original Gas oil.

3. Kinematic Viscosity
The kinematic viscosity of the W/O typeemulsified Gas oil in this study was measured byusual Cannon-Fenske Viscometer shown in Fig.6.㩷

By the elapsed time of flow down of emulsion (T),from A to B shown in Fig.6, and the characteristic
viscometer constant (C), the kinematic viscosity (Qof emulsified Gas oil can be estimated as follows;Q PUm C7  
where Pis the viscosity of emulsion, and Umis thedensity of emulsion.
Figures 7, 8 and 9 show the effects of thetemperature, the water content and the revolution of
the first gear on the kinematic viscosity of the W/Otype emulsified Gas oil respectively.
The density of emulsion (Um may be expressed
as follows, using the ratio of water in emulsion (W);Um UA (1-W)+UwW(2)

where UA is the density of Gas oil (0.82 g/cm3), and
Uw is the density of water (1.0 g/cm3). At thestandard state; 20oC, the kinematic viscosities (Q ofwater and Gas oil are about 1.0 (mm2/s) and 2.7(mm2/s) respectively.
From the result shown in Fig.7, we can see aninteresting and important fact that the kinematic
viscosity of W/O type emulsified Gas oil is slightly
higher than those of original Gas oil and of theestimation by volume fractions of Gas oil and water.
This may be attributable to the existence and the
motion of many fine water particles. In addition,
the kinematic viscosity decreases only slightly withincrease in the near room temperature.

4.0

Emulsified Gas Oil (Water:3.0 vol.%)

Kinematic Viscosity(mm2/s)

3.5
3.0

Gas Oil

2.5

Estimation by Volume fraction of Gas Oil anfd Water

2.0

Emulsifier:3 Gears Type, 800rpm

1.5

Water

1.0
0.5

20

Fig.7
Fig.6

Cannon-Fenske Viscometer.

― 15 ―

22

24

26

Temperature(oC)

28

30

32

Effect of temperature on the kinematic viscosity.

Hiroki Ishida

From the Eq. (1), we can assume that the changeof kinematic viscosity of emulsion due to the watercontent is small because the viscosity of emulsion
can be assumed to increase with increase in thedensity. From the results shown in Figs.8 and 9,
however, we can see obviously that the increase
both in the water content and in the gear revolution
increases the kinematic viscosity of emulsion.
The increase in the water content will mean theincrease in the number of fine water particles in
emulsion, shown in Fig.10. The increase in the gear
revolution will lead to the strong smash of waterparticles in the emulsification path (shown in Fig.1)
and to the extremely finer water particles in theemulsion. Thus, the increase both in the watercontent and in the gear revolution will increase thecontact surface area between the water and thehydrocarbon fuel.

Kinematic Viscosity (mm2/s)

Emulsifier : 3 Gears Type
Emulsified Gas Oil
Temp.: 22 oC

1000

3.5

800

3.4
3.3
2.5

3.0

3.5

4.0

4.5

5.0

5.5

Water Content (vol.%)

Effect of water content on the kinematic viscosity.

Kinematic Viscosity (mm2/s)

3.8

Emulsifier: 3 Gears TypeW/O emulsified Gas Oil
3.7 Temp:22 0C

Water Content:5 vol.%

3.6

4

3.5

3

3.4
3.3
700

800

900

1000

1100

1200

Revolution of the First Gear (rpm)Fig.9

The increase in the contact surface area will
increase the kinematic viscosity of emulsion. We
can find many reports through the Internet, referring
the increase in the kinetic viscosity of emulsion due
to the increase in the water content and to thedecrease in the size of water particles.

For the kinematic viscosity of the W/O typeemulsions of Gas㩷 oil, produced by the gear pump
type mechanical emulsifier without surface-active
agent, the present study revealed some interestingand important characteristics as follows;(1) The kinematic viscosity of W/O typeemulsified Gas oil is higher than that of originalGas oil, which may be due to the existence of manyfine water particles.
(2) Both the increase in the water content and theincrease in the gear revolution increase thekinematic viscosity of W/O type emulsified Gas oil.
(3) The increase in the kinematic viscosity ofW/O type emulsion may be attributable to theincrease in the contact surface area between thewater and the original hydrocarbon fuel.

1200 rpm

3.6

Fig.8

Microscopic Photograph of Water Particles in theEmulsified Gas Oil (Water: 9 vol.%, 800 rpm).

4. Concluding Remarks

3.8
3.7

Fig. 10

Effect of revolution on the kinematic viscosity.

1300

Acknowledgments: The author would like toexpress his sincere thanks to Mr. T. Nakayama,
N-Techno Co., Ltd. for his great help inconstructing the experimental setup and providing
the gear pump type mechanical emulsifier. Messrs.
S. Tai and Y. Kosuge are appreciated for their great
help in the experiment. The author is indebted forthe financial support by Sasaki Environment
Technology Foundation through this study.

― 16 ―

Kinematic Viscosity of Mechanically Emulsified Gas Oil

References
1) Dryer, F.L.: Water Addition to Practical Combustion
Systems-Concepts and Applications. Proc. Combust. Inst.,
Vol.16, pp. 279-295, 1976.
2) Sjorgen, A.: Burning of Water-in-Oil Emulsions, Proc.
Combust. Inst., Vol.16, pp. 297-305, 1976.
3) Jacques, M.T. et al.: The Combustion of Water-in-Oil
Emulsions and The Influence of Asphaltene Content, Proc.
Combust. Inst., Vol.16, pp. 307-319, 1976.
4) Hall, R.E.: The Effect of Water/Residual Oil Emulsions on
Air Pollutant Emissions and Efficiency of Commercial
Boilers, Journal of Engineering for Power, Transactions of
ASME October, pp. 425-433, 1976.
5) Jacques, M.T.: Transient Heating of a Emulsified
Water-in-Oil Droplet, Combustion and Flame, Vol.29, pp.
77-85, 1977.
6) Birchley, J.C. and Riley, N.: Transient Evaporation andCombustion of a Composite Water-Oil Droplet, Combustion
and Flame, Vol. 29, pp. 145-165, 1977.
7) Law, C.K.: A Model for the Combustion of Oil/Water
Emulsion Droplets, Comb. Sci. and Tech., Vol. 17, pp. 29-38,
1977.
8) Cook, D.H. and Law, C.K.: A Preliminary Study on the
Utilization of Water-in-Oil Emulsions in Diesel Engines,
Comb. Sci. and Tech., Vol. 18, pp. 217-221, 1978.
9) Lasheras, J.C., et al.: Initial Observations on the Free
Droplet Combustion Characteristics of Water-in-FuelEmulsions, Comb. Sci. and Tech., Vol. 21, pp. 1-14, 1979.
10) Weatherford Jr., W.D., et al.: Army Fire-Resistant Diesel
Fuel, SAE Technical Paper Series, No. 790926, 1979.
11) Law, C.K., et al.: Combustion Characteristics ofWater-in-Oil Emulsion Droplets, Combustion and Flame,Vol. 37, pp. 125-143, 1980.
12) Jahani, H. and Gollahalli, S.R.: Characteristics of Burning
Jet A Fuel and Jet A Fuel-Water Emulsion Sprays,
Combustion and Flame, Vol. 37, pp. 145-154, 1980.
13) Lasheras, J.C., et al.: On the Disruptive Burning of Free
Droplets of Alcohol/n-Paraffin Solutions and Emulsions,
Proc. Combust. Inst., Vol. 18, pp. 293-305, 1981.
14) Gollahalli, S.R., et al.: Combustion of Drops and Sprays of
No.2 Diesel Oil and Its Emulsions with Water, Proc.
Combust.Inst., Vol. 18, pp. 349-360, 1981.
15) Law, C.K.: On the Fire Resistant Nature of Oil/Water
Emulsions, Fuel, Vol. 60, pp. 998-999, 1981.
16) Marrone, N.J., et al.: Internal Phase Size Effect on
Combustion of Emulsions, Comb. Sci. and Tech., Vol.33, pp.
299-307, 1983.
17) Yap, L.T., et al.: Disruptive and Micro-Explosive
Combustion of Free Droplets in Highly Convective
Environments, Comb. Sci. and Tech., Vol. 41, pp. 291-313,
1984.
18) Ishida, H. and Iwama, A.: Ignition Characteristics of Gelled(O/W Emulsified) Hydrocarbon Fuel Pool, Comb. Sci. andTech., Vol. 36, pp. 51-64, 1984.

19) Ishida, H. and Iwama, A.: Flame Spreading along theSurface of Gelled (O/W Emulsified) Hydrocarbon Fuelpool, Comb. Sci. and Tech., Vol. 36, pp. 65-82, 1984.
20) Ishida, H. and Iwama, A.: Flame Spread along Gelled (O/W
Emulsified) Pool of High-Volatile Hydrocarbon Fuel, Comb.
Sci. and Tech., Vol. 37, pp. 79-92, 1984.
21) Wang, C.H. and Law, C.K.: Microexplosion of Fuel
Droplets under High Pressure, Combustion and Flame, Vol.
59, pp. 53-62, 1985.
22) Kimura, M., et al.: Combustion behaviors of Emulsified
Petroleum and JP-4/N2H4 Droplets at Weightless and Free
falling Conditions, Comb. Sci. and Tech., Vol. 44, pp.
289-306, 1986.
23) Randrolph, A.L. and Law, C.K.: Time-Resolved
gasification and Sooting Characteristics of Droplets of
Alcohol/Oil Blends and Water/Oil Emulsions, Proc.
Combust. Inst., Vol. 21, pp. 1125-1131, 1986.
24) Ishida, H. and Watanabe, H.: Flame Suppression overLiquid Pool by W/O Emulsification, Comb. Sci. and Tech.,
Vol.71, pp. 145-154, 1990.
25) Adiga, K.C. and Shah, D.O.: On the Vaporization Behaviorof Water-in-Oil Microemulsions, Combustion and Flame, Vol.
80, pp. 412-414, 1990.
26) Chung, S.H. and Kim, J.S.: An Experiment on Vaporizationand Microexplosion of Emulsion Fuel Droplets on a Hot
Surface, Proc. Combust. Inst., Vol. 23, pp. 1431-1435, 1990.
27) Yamasaki, H. and Tsue, M.: Evaporation and Combustionof Emulsified Fuel, JSME Int’l J. (B), Vol. 36, pp.
677-681,1993.
28) Ballester, J.M., et al.: Detailed Measurements in Heavy Oil
and Oil/Water Emulsion Flames, Comb. Sci. and Tech., Vol.
106, pp. 383-391, 1995.
29) Tsue, M., et al.: Observation of Sooting Behavior in
Emulsion Droplet Flame by Planar Laser Light Scatteringin Microgravity, Proc. Combust. Inst., Vol. 26, pp.
1251-1258, 1996.
30) Tsue, M., et al.: Statistical Analysis on Onset ofMicroexplosion for an Emulsion Droplet, Proc. Combust.
Inst. , Vol. 26, pp. 1629-1635, 1996.
31) Yamasaki, H., et al.: Time Histories of Water Contents in a
Burning Emulsion Droplet, Proc. The First Asia-PacificConf. on Combustion, pp. 603-606, 1997.
32) Tsue, M., et al.: Effect of Gravity on Onset ofMicroexplosion for an Oil-Water Emulsion Droplet, Proc.
Combust. Inst., Vol. 27, pp. 2583-2593, 1998.
33) Kufferath, A., et al.: Continuous Generation and
Air-Assisted Atomization of Fuel Oil-Water-Emulsions,Comb. Sci. and Tech., Vol. 148, pp. 17-26, 1999.
34) Nachmoni, G. and Natan, B.: Combustion Characteristics ofGel Fuels, Comb. Sci. and Tech., Vol. 156, pp. 139-157,
2000.
35) Leite, L.F.T. and Lage, P.L.C.: Modeling of Emulsion
Droplet Vaporization and Combustion Including
Microexplosion Analysis, Comb. Sci. and Tech., Vol. 157,

― 17 ―

Hiroki Ishida

pp. 213-242, 2000.
36) Walavalkar, A.Y. and Kulkarni, A.K.: Combustion of
Water-in-Oil Emulsion Layers Supported on Water,
Combustion and Flame, Vol. 125, pp. 1001-1011, 2001.
37) O-Barrera, R. and Vilasenor, R.: An Experimental study of
the Effect of Water Content on Combustion of Heavy Fuel
Oil/Water Emulsion Droplets, Combustion and Flame, Vol.
126, pp. 1845-1855, 2001.
38) Gong, J-S. and Fu, W-B.: A Study on the Effect of More
Volatile Fuel on Evaporation and Ignition for Emulsified
Oil, Fuel, Vol. 80, pp. 437-445, 2001.
39) Dantas, T.NdeC., et al.: New Microemulsion System using
Diesel and Vegetable Oils, Fuel, Vol. 80, pp. 75-81, 2001.
40) Kadota, T. and Yamasaki, H.: Recent Advances in the
Combustion of Water Fuel Emulsion, Progress in Energy
and Comb. Sci., Vol. 28, pp. 385-404, 2002.
41) Hernandez, J.F. and Morla, J.C.: Fuel Emulsions Using
Biomass Pyrolysis products as an Emulsifier Agent, Energy&Fuels, Vol. 17, pp. 302-307, 2003.
42) Wang, C.H. et al.: Combustion and Micro-explosion ofCollision-merged Methanol/Alkane Droplets, Proc.
Combust. Inst., Vol. 30, pp. 1965-1972, 2005.
43) Nakayama, T.: International Patent Application, B01F 3/08
(2006.01), No. PCT/JP2005/022850 (WO 2007/069298 A1).
44) Ishida, H. and Tachibana, K.: A mechanical Emulsification
Technology of Petroleum fuels without Surface Active
Agent, Research Rep. of Nagaoka National College ofTechnology, Vol. 45, No.2, pp. 47-54, 2009.
45) Ishida, H.: Kinematic Viscosity of Mechanically Emulsified
A-Heavy oil, Research Rep. of Nagaoka National College㩷
of Technology, Vol. 46, pp. 25-29, 2010.
(Received August 2, 2012)― 18 ―