A REVIEW ON CURRENT TRENDS IN WATER IN OIL EMULSIONS...This paper reviews the current trends of water in fuel emulsions to bring the undergoing research in this area, which includes

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 4, April 2017, pp. 359–371 Article ID: IJMET_08_04_038

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=4

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

A REVIEW ON CURRENT TRENDS IN WATER

IN OIL EMULSIONS

Kiran Raj Bukkarapu, Y. Jyothi, L. S. Raju, G. Chitti Babu and Karthik Narayanan

Department of Mechanical Engineering,

VFSTR University, Guntur, Andhra Pradesh, India

ABSTRACT

Introduction of water into diesel/biodiesel could be an answer to simultaneous

reduction of NOX and PM, with increased combustion efficiency. Micro explosion

phenomenon plays a vital role in influencing the combustion and emission characteristics

of the emulsion, which is explained in detail. The stability of water in oil emulsions is

better explained by surfactant concentration, HLB of the surfactant, water concentration

in the emulsion which are discussed in this paper. This review paper collects and

discusses the recent advances in water in diesel and water in biodiesel emulsion fuel

studies and their impact on the performance and emission of diesel engines.

Key words: Emulsion, Diesel, Biodiesel, Micro Explosion, Emissions.

Cite this Article: Kiran Raj Bukkarapu, Y. Jyothi, L. S. Raju, G. Chitti Babu and Karthik

Narayanan, A Review on Current Trends in Water in Oil Emulsions, International

Journal of Mechanical Engineering and Technology, 8(4), 2017, pp. 359-371.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=4

1. INTRODUCTION Diesel engines have found wide applications in many industrial, agricultural and transport

sectors due to their better fuel to power conversion efficiency and fuel economy. Apart from

being a fuel of wide applications, it is also a major contributor to the atmospheric emissions

leading to shrinking snow and ice, rise in sea level, severe droughts and floods. Reportedly, 57%

of green house gases are from fossil fuel combustion owing to transport and industrial sectors

[1]. Emissions from fossil fuel combustion not only harm the nature but also deteriorate human

health by nitrogen oxides and particulate matter [2]. The emissions from diesel engines include

carbon monoxide (CO), carbon dioxide (CO2), unburned hydrocarbon (HC), nitrogen oxides

(NOX), particulate matters (PM) and traces of sulphur oxides (SOX) [3, 4, 5]. The emission

regulations introduced are being continuously revised and are driving the researchers to search

for techniques reducing the emissions [2, 4, 6]. Among all the diesel engine emissions, oxides of

nitrogen and particulate matter are of most significance. According to Euro 5, NOx and PM

emission limits for passenger cars are be reduced from 0.25 g/km to 0.18 g/km and 0.025 g/km to

A Review on Current Trends in Water in Oil Emulsions


0.005 g/km, respectively. For the other emissions, carbon monoxide and total hydrocarbon, no

further development in engines seems to be necessary to meet future limits. Since NOx and PM

emissions are close to the limits permitted by regulations these two emissions have become a

major concern for researchers [5]. With an intention of pulling down the NOx emissions, devices

like NOx Absorber Catalysts (NAC) and Selective Catalytic Reduction (SCR) are employed

which are able to meet the purpose to a large extent [2, 4]. To reduce PM, Diesel Oxidation

Catalysts (DOCs) and Diesel Particulate Filters (DPFs) are commonly used. DPFs are able to

reduce PM to 90% while DOCs are able to reduce PM to 25%. But, DOCs are cheaper to DPFs.

[2, 7]. However, simultaneous control of both NOx and PM is difficult [2, 8]. An alternative to

all these techniques, which does not demand any engine modifications, simultaneously reduces

both the emissions is, to make possible alterations to the fuel. Introduction of water into the

diesel could serve the purpose and apparently, researchers have proved a measurable reduction in

NOx and PM by using water in diesel emulsions as an alternative fuel in diesel CI engines [9-12].

Diesel being a non-renewable fuel, experiments using vegetable oils which are renewable,

were conducted [13-18]. High fuel viscosity of the vegetable oils resulting in injector fouling is

one of the major problems associated with their use as fuels for Diesel engines. Vegetable oils as

alternative fuels in diesel engines are disadvantageous in terms of their higher viscosity, higher

cloud point, higher pour point, higher flash point, higher density and the reactivity of unsaturated

hydrocarbon chains [19-23]. The high viscosity which is nearly 10 times higher than that of

conventional diesel is reduced by transesterification in which the oil is allowed to react with

methanol or ethanol, in the presence of a catalyst, to convert triglycerides to monoglycerides and

glycerol. The obtained fatty acid methyl/ethyl esters are termed as biodiesel [24-26]. Biodiesel is

found to be an appreciable alternative to both non-renewability and the harmful emissions of

diesel [27, 28]. The presence of oxygen in biodiesel helps in achieving lesser CO and HC than

those of diesel [29]. However, it promotes NOX formation and hence NOX is found to be more

than that in diesel [30, 31]. The soot and PM are not of major concern when biodiesel is used.

Increase in NOX can be addressed by introducing water to biodiesel.

The comparative advantage of water in fuel emulsions to diesel fuel is not precisely known

and understood. The reasons behind this could be insufficient knowledge on micro-explosion

phenomenon and the associated combustion phenomenon. The other reasons could be

confinement of the research to engine tests on water in diesel emulsions only, which are

inconsistent [33], with no much concentration on influence of water concentration, surfactant

concentration, HLB of surfactant on the emulsion stability. This paper reviews the current trends

of water in fuel emulsions to bring the undergoing research in this area, which includes emulsion

stability, performance and emission characteristics, under one document and to further enlighten

the possible area of intervention for researchers.

2. WATER IN OIL EMULSIONS

Introduction of water into diesel or biodiesel helps in simultaneous reduction of NOX and PM

[34, 35]. Water can be introduced by injecting it into the intake manifold which is called intake

manifold fumigation [36, 37, 38] or by direct injection into the combustion chamber [39, 40] or

by preparing water in fuel emulsions. Intake manifold fumigation methods needs a special

provision for water supply. The injected water enters the cylinder along with the intake air and

gets vaporized during the compression stroke as both the water and the air get heated up [34].

Injecting water directly into the combustion chamber using a separate injector reduces NOX to an

extent greater than that in intake manifold fumigation, as the water droplets are closer to the



flame during the combustion [41]. However, in addition to increase in HC and CO [42, 43], these

methods demand necessary modifications in the engine [44].

A mixture of two or more immiscible liquids, one as a droplet dispersed throughout the other

continuous phase liquid is known as an emulsion [2, 7, 46]. The dispersed droplet falls under

internal phase while the other liquid is external. Based on the diameter of the dispersed droplet a

mixture is termed as an emulsion if it lies between 1-10 μm, micro emulsion if it is less than 0.2

μm [47] and nano emulsion if it is less than 300 nm [48].

Water in oil emulsions can be promising alternatives which do not demand any engine

modifications and simultaneously reduce NOX and PM, with an increase in the combustion

efficiency [8, 35]. The oil mentioned above can be either diesel or biodiesel. Injecting water into

gasoline is generally not preferred as the its boiling point (~85`C) is near to water (~100`C),

while the difference is generally high in case of diesel (~180-340`C) [45].

3. WATER IN OIL EMULSION-CHARACTERISTICS

3.1. Stability of the Emulsion Fuel

Micro-emulsions are thermodynamically stable [47], while emulsions are thermodynamically

unstable [47, 49]. Typically, water-in-diesel emulsion fuel can be stable for a period of 3 months

[42] but it will depend on various factors, such as the type and percentage of surfactant, the

temperature, viscosity, specific gravity and water content [7]. Emulsions will separate into two

phases in due course of time. Water in diesel emulsion loses its stability progressively through

creaming, aggregation, flocculation and coalescence [50, 51]. Creaming is the initial stage of

destabilization where density difference of two liquids comes into action. Followed by creaming,

aggregation takes place where the droplets are attracted towards to each other. Thus these

droplets form bigger droplets, like a bunch of grapes, separated by a thin layer. This process is

termed as flocculation. The thickness of the layer separating the grouped droplets gets reduced

progressively due to strong Vander-Waals forces and thus it breaks leading to formation of a

larger droplet. This process is known as coalescence. Consequently, these droplets either settle at

the bottom or float on top, based on the densities of internal and external phases. This is called

sedimentation. All these processes continue and finally lead to separation of both the phases.

3.1.1. Effect of surfactant concentration on stability of water in oil emulsions

Surfactant acts like an emulsifying agent that increases the areas of contact of the two immiscible

liquids, thus helping to form one stable solution [52]. As the surfactant gets blended into the

mixture of water and oil, its polar groups orient toward the water and the non-polar group toward

the oil, thus lowering the interfacial tension between the two liquids [53]. 20% W/D emulsion

with no surfactant added, 3 minutes of agitation and a mixing speed of 15000 rpm got separated

in less than 5 minutes [55]. This clearly proves the importance of a surfactant. Span 80 and

Tween 80, Octyl phenoxy poly ethoxy ethanol also known as Triton X-100 and liquid soap or

glycerin are the surfactants which are mostly used by the researchers [54]. The surfactant is

generally added to the mixture of two immiscible liquids in a percentage of 0.1 to 2%. M. T.

Ghannam et al studied the stability behavior of water in diesel emulsions and concluded that

stabilization of water in diesel emulsions with higher water concentration (>20%) requires

increased surfactant concentration. In order to enhance the stability of W/D emulsion with 30%

of water in it, the authors have added surfactant in different concentrations from 0.2% to 1.75%

for a mixing speed of 20,000 rpm and a mixing time of 30 minutes. They have observed that the



presence of surfactant in different concentrations has a strong impact on the stability

enhancement of the emulsion [55, 56]. The amount of water separated from the emulsion

strongly decreased with the increase of surfactant concentration. The emulsion with surfactant

concentration of 1.75%, 30% Water and 68.25% of diesel emulsion remained stable for almost 1

week [55]. Another sample with 2% of surfactant in 30% W/D emulsion retained its stability for

4 hours only. As the percentage of surfactant is increased further from its maximum value of 2%,

the stability of the emulsion will deteriorate. This is due to the rapid coalescence that occurs

when high surfactant concentration is added [7, 55, 57]. They have observed that the optimal

concentration of the surfactant was 0.5% by volume. Similar trends can be observed even in case

of water in biodiesel emulsions. Experiments have proved that increasing the surfactant

concentration would increase the stability of the W/B emulsions.

3.1.2. Effect of surfactants’ HLB on stability of water in oil emulsions

There are numerous surfactants available in the market, which are categorized based on their

Hydrophilic-Lypophilic balance (HLB). HLB (Hydrophilc-Lipophilc Balance) of a surfactant

talks about its water loving and water hating nature. Surfactants with different ranges of HLB

and their applications are shown in Table 1.

Table 1. HLBs of different surfactants and their applications

S. No HLB Surfactant function

1. 2-3 Antifoaming agent

2. 3-6 W/D emulsions

3. 7-9 Wetting and spreading agents

4. 8-16 D/W emulsions

5. 13-15 Detergents

HLB ranges from 0-20 only. Span 80 has an HLB of 4.3 while Twine 80 has 15.0 which

indicates that Span 80 is a lipophilic (water hating) surfactant while Twin 80 is hydrophilic

(water loving). HLB is the ratio of molecular mass of the hydrophilic portion to the molecular

mass of the whole molecule. C. Y. Lin et al prepared O/W/O emulsions using a surfactant

mixture of Span 80 and Tweed 80, which has an HLB of 13. On their observation, this emulsion

was the most stable emulsion among others prepared with different HLBs [58]. Surfactant

mixture with HLB of 6 exhibited least emulsion stability. They also observed that the stability of

B/O/B emulsions is inferior to that of D/W/D emulsion, when same mixture of Span-80 and

Tween-80 is used for both the emulsions [58].

3.1.3. Effect of water concentration on stability of water in oil emulsions

M. T. Ghannam et al have prepared W/D emulsions with 0.2% surfactant, at a mixing speed of

15,000 rpm and mixing time of 2 minutes. It is observed that the 10% W/D emulsion remained

stable for almost 4 weeks, while the 20% W/D remained stable for 10 days. The emulsions

prepared by 30%, 40% and 50% of water remained stable for only 5 hours, and then the water

gradually separated from the emulsion. It is concluded that with the same surfactant

concentration, same mixing speed and mixing time, one with more water content will have least

stability. Also, as the water concentration increases, the percentage of water that gets separated

increases, as shown in Figure 1 [55]. Increasing the surfactant concentration would make the



emulsion more stable, as mentioned in the earlier sections, but it would be too costly to prepare

and thus uneconomical. Gonglun Chen et al suggest the optimum ratio of water to diesel to be

1:1, after observing that the emulsion stability increased with decreasing diesel-to-water ratio

[57].

Figure 1 Stability profile for different W/D emulsions.

3.1.4. Effect of mixing speed on stability of water in oil emulsions

There are many ways to prepare an emulsion of two immiscible liquids. Emulsification is in

general achieved by the application of mechanical energy. The purpose of mixing is to break the

large droplets into smaller ones, thereby forming a stable mixture. 10% W/D emulsion is found

to be stable or 4 weeks, when the emulsion is prepared at 30000 rpm and with 0.2% surfactant.

For a higher concentration of water content, the mixing speed has to be increases significantly

[55]. Higher stirring intensity results in more stable emulsion. The optimum mixing speed was

2500 rpm for the emulsion system investigated by Gonglun Chen et al. [57]. However, speed

higher than the optimum value would break the emulsifier away from oil-water interface.

3.2. Viscosity of the emulsion fuel

Viscosity is an important property that affects its atomization characteristics [59]. If the viscosity

of the fuel is too high, then it would lead to poor spray characteristics while a less viscous fuel

results in excessive wear. It is observed that the viscosity of diesel increases with the increasing

water content in it, as shown in Figure 2 [60]. It is also found that the kinematic viscosity of W/B

emulsions is higher than that of neat diesel [58].



Figure 2 Viscosity of the tested fuel versus water content.

3.3. Heating Value of the Emulsion Fuel

Heating value of a fuel signifies its energy content and thereby its specific fuel consumption. It is

observed that the lower heating value of diesel decreases with increasing water content in it, as

shown in Figure 3 [60]. C. Y. Lin et al have concluded form their experiments that the W/B

emulsion has a heating value 7.6-8.7% more than that of neat biodiesel, when the water content

is not considered while calculating the heating value [58].

Figure 3 Reduction of relative low heating value versus water content in emulsion

4. ICRO EXPLOSION: A BOON TO W/O OR O/W EMULSION FUELS

Apart from properties like heating value, kinematic viscosity that influence the performance and

emission characteristics of water in oil run diesel engine, micro-explosion phenomenon also

plays an important role. It has a huge impact on increasing the combustion efficiency and in

reducing the emissions. As W/O emulsion fuel is sprayed into the combustion chamber, the

droplet picks up the heat by convection. As soon as the water droplet reaches its superheat

temperature, it explodes, thus getting torn up into very fine particles [54, 62, 63]. This process is

termed as micro explosion. It leads to secondary atomization of the droplet and hence better



mixing of fuel and air. Therefore, it is important to understand micro explosion phenomenon and

the factors influencing it [2]. The factors affecting the phenomenon of micro explosion are

tabulated as Table 2.

Table 2 Factors Affecting the Phenomenon of Micro Explosion

S. No Factor Effect on micro explosion process

1.

Size of dispersed water particle As the size of the dispersed water particle increases

strength of the explosion also increases but up to 4.7

microns only.

2. Droplet size of the emulsion It should be at least twice the size of the dispersed water

droplet for strong micro explosion to occur.

3. Water-content in the emulsion Higher water content leads to vigorous micro explosion.

4. Ambient temperature Relatively higher temperature leads to quicker micro

explosion

5. Ambient pressure If the ambient pressure is relatively higher, then the

occurrence of micro explosion is quicker.

5. PERFORMANCE AND EMISSION CHARACTERISTICS OF DIESEL

ENGINE USING WATER IN OIL EMULSION FUEL

5.1. Combustion Characteristics

As a consequence of micro explosion, the oil droplet enclosing the water droplet, gets distributed

and atomized well, leading to better combustion, thus increasing the combustion efficiency [6,

42, 63-67]. Sheng et al have observed that the usage of W/D emulsions increases the ignition

delay when compared to neat diesel. However, the combustion rate and flame propagation seem

to increase due to micro explosion [63]. Ghojel and Honnery [68] and Armas et al. [12], reported

a slightly longer ignition delay and longer combustion duration as a consequence of lower flame

temperatures. Ahmad Muhsin Within et al have prepared W/D emulsions with water content

varying from 5% to 20% to understand the nature of combustion of W/D emulsions in a diesel

engine and they have reported that the emulsion with 20% water exhibits a peak pressure and

maximum heat release rate which is comparable to diesel almost at all loads, among all the

prepared emulsions [6]. Irrespective of lesser heating value, emulsion with higher water content

has a higher peak pressure which accounts to the vigorous micro explosion that takes place with

increasing water content. Namasivayam et al reports that the emulsified rapseed methyl ester fuel

has longer ignition delay than that of neat diesel and neat rapseed biodiesel by an amount of 10%

with 30% lower peak pressures [32].

5.2. Engine power

A slight reduction in the brake power and torque is reported in the literature [34, 42, 69, 70, 71].

This reduction is attributed to the lesser heating value of the emulsions [42, 69, 71]. Nadeem et al

observed a reduction in the torque with an emulsified fuel when compared to neat diesel [7].

Alahmer et al. reported that the engine produces maximum torque and hence power when it is

fuelled with 5% water content in it [46]. Barnes et al. reported a power loss of 7-8% on the

application of W/D emulsified fuel with 10% water content by volume [72]. Abu Zaid et al

report in contrast to all the researchers’ reports that the engine torque and power increase with



increasing water content [73]. They explain that the reason might be additional effort put by

steam in pushing the piston down, irrespective of the reduced heating value with increased water

content. However, as these experiments are based on different engine set ups, the conflict in the

results cannot be explained and hence a much detailed study is necessary to understand the effect

of water content on brake power and torque of the diesel engine.

5.3. Brake Specific Fuel Consumption

Several researchers have reported that there is slight increase in the BSFC, if the whole emulsion

is considered as a fuel, when compared to neat diesel and that it has improved when only diesel

in the emulsion is considered as the fuel. The reason can be replacement a proportionate amount

of diesel with water, having lesser heating value when compared to diesel, thus reducing the

overall heating value relative to neat diesel [42, 69, 73].

5.4. Exhaust Emissions

The water droplet enclosed in the oil droplet picks up heat from the surroundings to undergo

evaporation. Thus, this endothermic reaction favors in lowering the surrounding in cylinder

temperatures. A. M. Ithnin et al have reported lesser NOX emissions in W/D emulsions when

compared to that of neat diesel. Emulsion with 20% water is reported to have the least NOx

emissions which is 41% lesser than that of neat diesel, at all load conditions [2, 6]. M.E.A. Fahd

et al also have observed the same results [69]. Several researchers [4, 60, 72] concluded that it is

this endothermic reaction resulting in lesser NOx emissions. However, these lower temperatures

do not promote oxidation of CO to CO2 and combustion of HC, thus increasing both these

emissions. CO emissions are found be higher in all emulsions compared to neat diesel as

reported by A.M. Within [2, 6]. Emulsion with 20% water has highest CO emissions at all loads

when compared to those of 5%, 10% and 15% W/D emulsions. At low load conditions, the

temperatures are not sufficient enough for better combustion, in addition to which the

evaporation of water droplet which is an endothermic reaction lowers down the temperatures

further more thus promoting CO emissions and lowering CO2 emissions. In support to this

argument, researchers have found that at low load conditions, CO emissions are higher than that

of diesel while CO2 emissions are comparable to that of diesel. However, micro explosion

phenomenon helps in improving the combustion efficiency at higher loads and thus CO

emissions are found to be comparable to diesel at higher loads, while CO2 emissions increase [2,

4, 6, 60, 72]. PM emissions are reduced in all water diesel emulsions compared to neat diesel

[6]. Emulsion with 20% of water has the least PM emissions ie.35% lesser than ordinary diesel,

at all load conditions. It is attributed to the increased homogeneity because of micro explosion

and reduced temperatures because of evaporation.



6. CONCLUSION

This paper helps in gaining quick knowledge on water in oil emulsions and the following points

can be concluded from the review

1. The surfactant is generally added to the mixture of two immiscible liquids in a percentage of 0.1

to 2%. Lower surfactant concentrations make the emulsion less stable and higher surfactant

concentrations could not stabilize the emulsions, owing to rapid coalescence. HLB of the

surfactant to be used should not be too high or too low. An optimum value of HLB is preferred,

which can be attained by mixing two surfactants too.

2. The stability of B/O/B emulsions is inferior to that of D/W/D emulsion, when same mixture of

Span-80 and Tween-80 is used for both the emulsions.

3. With the same surfactant concentration, same mixing speed and mixing time, W/O emulsion with

more water content will have least stability. Also, as the water concentration increases, the

percentage of water that gets separated increases.

4. Higher stirring intensity results in more stable emulsion. However, speed higher than the

optimum value would break the emulsifier away from oil-water interface.

5. It is observed that the viscosity of diesel increases with the increasing water content in it. It is also

found that the kinematic viscosity of W/B emulsions is higher than that of neat diesel.

6. It is observed that the lower heating value of diesel decreases with increasing water content in it.

7. As the size of the dispersed water particle increases strength of the micro explosion also increases

but up to 4.7 microns only. The size of whole emulsion droplet should be at least twice the size of

the dispersed water droplet for strong micro explosion to occur. Higher water content in an

emulsion leads to vigorous micro explosion.

8. The usage of W/D emulsions increases the ignition delay when compared to neat diesel.

However, the combustion rate and flame propagation seem to increase due to micro explosion.

9. Several researchers have reported that there is slight increase in the BSFC, if the whole emulsion

is considered as a fuel, when compared to neat diesel and that it has improved when only diesel in

the emulsion is considered as the fuel.

10. Water in diesel emulsions has a potential to reduce NOX emission and PM simultaneously, which

could not be attained by conventional methods. It is the evaporation of dispersed water droplet

which is an endothermic reaction that lowers down the NOx emissions in W/D emulsions. Micro

explosion leads to increased homogeneity and thus reduces PM. Reduction in NOX and PM is at

an expense of increased CO and HC, attributed to lower temperatures.

REFERENCES

[1] T. Barker, Climate Change 2007: An Assessment of the Intergovernmental Panel on Climate

Change, 2007, pp. 12–17.

[2] A.M. Ithnin, H. Noge, H. A. Kadir, W. Jazair, An overview of utilizing water-in-diesel

emulsion fuel in diesel engine and its potential research study, Journal of the Energy Institute

87 (2014) 273–288.

[3] C. Lin and K. Wang, The fuel properties of three-phase emulsions as an alternative fuel for

diesel engines,” Fuel, vol. 82, no. 11, pp. 1367–1375, 2003.

[4] Mohammed Yahaya Khan, Z. A. Abdul Karim, Ftwi Yohaness Hagos, A. Rashid A. Aziz

and Isa M. Tan, Current Trends in Water-in-Diesel Emulsion as a Fuel, The Scientific World

Journal, Volume 2014, Article ID 527472, 15 pages.



[5] Magın Lapuerta, Octavio Armas, Jose Rodrıguez-Fernandez, Effect of biodiesel fuels on

diesel engine emissions, Progress in Energy and Combustion Science 34 (2008) 198–223.

[6] Ahmad Muhsin Ithnin, Mohamad Azrin Ahmad, Muhammad Aiman Abu Bakar, Srithar

Rajoo, Wira Jazair Yahya, Combustion performance and emission analysis of diesel engine

fuelled with water-in-diesel emulsion fuel made from low-grade diesel fuel, Energy

Conversion and Management 90 (2015) 375–382.

[7] M. Nadeem, C. Rangkuti, K. Anuar, M.R.U. Haq, I.B. Tan, S.S. Shah, Diesel engine

performance and emission evaluation using emulsified fuels stabilized by conventional and

gemini surfactants, Fuel 85 (2006) 2111–2119.

[8] J.S. Basha, R.B. Anand, An experimental study in a CI engine using nanoadditive blended

water–diesel emulsion fuel, Int. J. Green Energy 8 (2011) 332–348.

[9] A. Lif and K.Holmberg, Water-in-diesel emulsions and related systems, Advances in Colloid

and Interface Science, vol. 123-126, pp. 231–239, 2006.

[10] T. Kadota and H. Yamasaki, Recent advances in the combustion of water fuel emulsion,

Progress in Energy and Combustion Science, vol. 28, no. 5, pp. 385–404, 2002.

[11] O. Armas, R. Ballesteros, F. J. Martos, and J. R. Agudelo, Characterization of light duty

diesel engine pollutant emissions using water-emulsified fuel, Fuel, 84(7-8), pp. 1011–1018,

2005.

[12] J. Ghojel, D. Honnery, and K. Al-Khaleefi, “Performance, emissions and heat release

characteristics of direct injection diesel engine operating on diesel oil emulsion,”

AppliedThermal Engineering, vol. 26, no. 17-18, pp. 2132–2141, 2006.

[13] Bhatia S, Heng JK, Lim ML, Mohamed AR. Production of biofuel by catalytic cracking of

palm oil: performance of different catalyst. In: Proceedings of the biofuel, PORIM

international biofuel and lubricant conference, Malaysia; 1998. p. 107–12.

[14] Nagai K, Seko T. Trends of motor fuel quality in Japan. JSAE Rev 2000;21:457–62.

[15] Bhatia S, Sang OY, Twaiq F, Zakaria R, Mohamed AR. Biofuel production from catalytic

cracking of palm oil. Energy Source 2003;25:859–69.

[16] Zhenyi C, Xing J, Shuyuan L, Li L. Thermodynamics calculation of the pyrolysis of

vegetable oils. Energy Source 2004;26:849–56.

[17] Demirbas A. Biodiesel fuels from vegetable oils via catalytic and noncatalytic supercritical

alcohol transesterifications and other methods: a survey. Energy Convers Manage

2003;44:2093–109.

[18] Giannelos PN, Zannikos F, Stournas S, Lois E, Anastopoulos G. Tobacco seed oil as an

alternative diesel fuel: physical and chemical properties. Ind Crop Prod 2002;16:1–9.

[19] Goering E, Schwab W, Daugherty J, Pryde H, Heakin J. Fuel properties of eleven vegetable

oils. Trans ASAE 1982;25:1472–83.

[20] Pryor RW, Hanna MA, Schinstock JL, Bashford LL. Soybean oil fuel in a small diesel

engine. Trans ASAE 1982;26:333–8.

[21] Saka S, Kusdiana D. Biodiesel fuel from rapeseed oil as prepared in supercritical methanol.

Fuel 2001;80:225–31.

[22] Komers K, Stloukal R, Machek J, Skopal F. Biodiesel from rapeseed oil, methanol and KOH

3. Analysis of composition of actual reaction mixture. Eur J Lipid Sci Technol

2001;103:363–3471.



[23] Darnoko D, Cheryan M. Kinetics of palm oil transesterification in a batch reactor. JAOCS

2000;77:1263–7.

[24] Otera J. Transesterification. Chem Rev 1993;93(4):1449–70.

[25] Freedman B, Butterfield RO, Pryde EH. Transesterification kinetics of soybean oil. J Am Oil

Chem Soc 1986;63(10):1375–80.

[26] Noureddini H, Zhu D. Kinetics of transesterication of soybean oil. J Am Oil Chem Soc

1997;74(11): 1457–63.

[27] Oliveria L. E, Da Silva M. L. C. P., Relationship between cetane number and calorific value

of biodiesel from Tilapia visceral oil blends with mineral diesel, Renewable energy and

power quality journal, ISSN 2172-038 X, No. 11, March 2013.

[28] Arida V. P, A. Atienza, F.C. Borlaza and D.L. Binlayo, Pilot Plant Production and

Development of a Diesel Fuel Substitute from Coconut Oil, Alternative Energy Sources. V

Part D:(1983).

[29] J.Xue, T.E.Grift and A.C.Hansen, Effect of biodiesel on engine performances and emissions,

Renewable and Sustainable Energy Reviews 15 (2011) 1098–1116.

[30] J.A. Bittle, B.M. Knight and T.J. Jacobs, Interesting behaviour of biodiesel ignition delay and

combustion duration, Energy & Fuels 24 (2010) 4166–4177.

[31] S. Fernando, C. Hall and S. Jha, NOx reduction from biodiesel fuels, Energy & Fuels 20

(2005) 376–382.

[32] A. M. Namasivayam, R. J. Crookes and T. Korakianitis Combustion Characteristics of Dual-

Fuel Diesel Engine Using Emulsified Bio-Fuel for Pilot Ignition SAE International, 2009-01-

0490.

[33] X. T. Tran and J. Ghojel, “Impact of introducing water into the combustion chamber of diesel

engines on emissions-an overview,” in Proceedings of the 5th Asia pacific Conference on

Combustion, The University of Adelaide, Adelaide Australia, July 2005.

[34] M.Y.E. Selim, M.T. Ghannam, Performance and engine roughness of a diesel engine running

on stabilized water diesel emulsion, SAE Pap. (2007), 2007-24-01.

[35] A. Bertola, R. Li, K. Boulouchos, Influence of water-diesel fuel emulsions and EGR on

combustion and exhaust emissions of heavy duty DI-diesel engines equipped with common-

rail injection system, SAE Pap. (2003), 2003-01-31.

[36] M.A.A. Nazha, H. Rajakaruna, S.A. Wagstaff, The use of emulsion, water induction and

EGR for controlling diesel engine emissions, SAE Pap. (2001), 2001-01-19.

[37] R. Udayakumar, S. Sundaram, S.C. Johnson, Reduction of NOx emissions by water injection

in to the inlet manifold of a DI diesel engine, SAE Pap. (2003), 2003-01-02.

[38] X. Tauzia, A. Maiboom, S.R. Shah, Experimental study of inlet manifold water injection on

combustion and emissions of an automotive direct injection Diesel engine, Energy 35 (2010)

3628–3639.

[39] F. Bedford, C. Rutland, P. Dittrich, A. Raab, F. Wirbeleit, Effects of direct water injection on

DI diesel engine combustion, SAE Pap. (2000) 1–10, 2000-01-29.

[40] M.A. Psota, W.L. Easley, T.H. Fort, A.M. Mellor, Water injection effects on NOx emissions

for engines utilizing diffusion flame combustion, SAE Pap. (1997), 971657.



[41] M.S. Kumar, J. Bellettre, M. Tazerout, The use of biofuel emulsions as fuel for diesel

engines: a review, Proc. Inst. Mech. Eng. Part A J. Power Energy 223 (2009) 729–742.

[42] W.M. Yang, H. An, S.K. Chou, K.J. Chua, B. Mohan, V. Sivasankaralingam, et al., Impact of

emulsion fuel with nano-organic additives on the performance of diesel engine, Appl. Energy

(2013).

[43] M. Christensen, B. Johansson, Homogeneous charge compression ignition with water

injection, SAE Pap. (1999), 1999-01-01.

[44] M.S. Kumar, J. Bellettre, M. Tazerout, Investigations on a CI engine using animal fat and its

emulsions with water and methanol as fuel, SAE Pap. (2005), 2005-01-17.

[45] A. Lif, K. Holmberg, Water-in-diesel emulsions and related systems, Adv. Colloid Interface

Sci. 123–126 (2006) 231–239.

[46] A. Alahmer, J. Yamin, A. Sakhrieh, M.A. Hamdan, Engine performance using emulsified

diesel fuel, Energy Convers. Manag. 51 (2010) 1708–1713.

[47] Ochoterena, R. et al. Optical studies of spray development and combustion of water-in-diesel

emulsion and microemulsion fuels. Fuel, Vol. 89, 2010, pp. 122-132.

[48] Anton, N., Vandamme, T.F. Nano-emulsions and micro-emul-sions: Clarifications of the

critical differences. Springer Science Business Media, LLC, 2010.

[49] Fu, Z. et al. Stabilization of water-in-octane nano-emulsion. Part I: Stabilized by mixed

surfactant systems. Fuel, Vol. 89, 2010, pp. 2838-2843. [50] Urbina-Villalba, G., Garcia-Sucre, M. Brownian dynamics simulation of emulsion stability.

Langmuir, Vol. 16, 2000, pp. 7975-7985.

[51] Song, M.-G. et al. Novel evaluation method for the water-in-oil (W/O) emulsion stability by

turbidity ratio measurements. Korean Chem. Eng., Vol. 19(3), 2002, pp. 425-430.

[52] J. Schramm, R. Sigvardsen, M. Forman, Bitumen/water emulsions as fuels for high-speed CI

engines preliminary investigations, SAE Pap. (2003), 2003-01-31.

[53] J. Jiao, D.J. Burgess, Rheology and stability of water-in-oil-in water multiple emulsions

containing Span 83 and Tween 80, AAPS Pharm. Sci 5 (1) (2003) 62–73.

[54] F.Y. Hagos, R.A. Aziz a., I.M. Tan,Water-in-diesel Emulsion and its Micro-explosion

Phenomenon-review, in: Commun. Softw. Networks (ICCSN), 2011 IEEE 3rd Int. Conf.,

IEEE, 2011, pp. 314–318.

[55] M. T. Ghannam, M. Y. E. Selim, Stability Behavior of Water-in-Diesel Fuel Emulsion,

Journal of Petroleum Science and Technology, Volume 27, 2009 - Issue 4.

[56] G. Ostberg, B. Bergenstahl, M. Hulden, Colloids and Surfaces. A, Physicochemical and

Engineering Aspects 94 (2-3) (1995) 161 – 171.

[57] Gonglun Chen, Daniel Tao, An experimental study of stability of oil–water emulsion, Fuel

Processing Technology 86 (2005) 499 – 508.

[58] Cherng-Yuan Lin, Shiou-An Lin, Effects of emulsification variables on fuel properties of

two- and three-phase biodiesel emulsions, Fuel 86 (2007) 210–217.

[59] Fan, X. et al. A new emulsifier behavior of the preparation for micro-emulsified diesel oil.

Petroleum Science and Technology, Vol. 26, 2008, pp. 2125–2136.

[60] Dan Scarpete, Diesel-water emulsion, an alternative fuel to reduce diesel engine emissions. A

Review, Machines, Technologies, Materials, ISSN 1313-0226. Issue 7/2003.



[61] Armas O, Ballesterosa R, Martosb FJ, Agudeloc JR. Characterization of light duty diesel

engine pollutant emissions using water-emulsified fuel. Fuel 2005;84:1011–8.

[62] W.B. Fu, L.Y. Hou, L. Wang, F.H. Ma, A unified model for the micro-explosion of

emulsified droplets of oil and water, Fuel Process Technol. 79 (2002) 107–119.

[63] H. Sheng, L. Chen, C. Wu, The droplet group micro-explosions in W/O diesel fuel emulsion

sprays, SAE Pap. (1995), 950855.

[64] B.D. Hsu, Combustion of water-in-diesel emulsion in an experimental medium speed diesel

engine, SAE Pap. (1986), 860300.

[65] T. Miyauchi, Y. Mori, T. Yamaguchi, Effect of steam addition on N O formation, Symp.

Combust. 18 (1981) 43–51.

[66] T. Murayama, Experimental Reduction of NOx, smoke, and BSFC in a diesel engine using

uniquely produced water, SAE Pap. (1979), 780224.

[67] M. Abu-Zaid, Performance of single cylinder, direct injection diesel engine using water fuel

emulsions, Energy Convers. Manag. 45 (2004) 697–705.

[68] J. Ghojel and D. Honnery, “Heat release model for the combustion of diesel oilemulsions in

di diesel engines,” Applied Thermal Engineering, vol. 25, no. 14-15, pp. 2072–2085, 2005.

[69] M.E.A. Fahd, Y. Wenming, P.S. Lee, S.K. Chou, C.R. Yap, Experimental investigation of the

performance and emission characteristics of direct injection diesel engine by water emulsion

diesel under varying engine load condition, Appl. Energy 102 (2013) 1042–1049.

[70] M.Y.E. Selim, M.T. Ghannam, Combustion study of stabilized water-in-diesel fuel emulsion,

Energy Sources, Part A Recover Util. Environ. Eff. 32 (2009) 256–274.

[71] F.L. Dryer, Water addition to practical combustion systems, concepts and application, Symp.

Combust. 16 (1976) 279–295.

[72] A.Barnes, D. Duncan, J.Marshall, A. Psaila, J.Chadderton, and A. Eastlake, Evaluation of

water-blend fuels in a city bus and an assessment of performance with emission control

devices, in Proceedings of the Better air Quality Motor Vehicle Control & Technology

Workshop 2000, 2000.

[71] K Santa Rao, Dr. S V Ramana and Dr. C L V R S V Prasad, Influence of Solid Lubricant

Emulsions on Surface Roughness of Hardened Steel When Machining On Shaper,

International Journal of Mechanical Engineering and Technology, Volume 4, Issue 5,

September - October (2013), pp. 63-70

[73] M. Abu-Zaid, Performance of single cylinder, direct injection Diesel engine using water fuel

emulsions, Energy Conversion and Management, 45 (5), pp. 697–705, 2004.

Documents

A REVIEW ON CURRENT TRENDS IN WATER IN OIL EMULSIONS...This paper reviews the current trends of water in fuel emulsions to bring the undergoing research in this area, which includes