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Energy Conversion and Management 45 (2004) 697–705www.elsevier.com/locate/enconman

Performance of single cylinder, direct injection Dieselengine using water fuel emulsions

M. Abu-Zaid *

Faculty of Engineering, Department of Mechanical Engineering, Mutah University, Al-Karak, Jordan

Received 13 February 2003; accepted 5 July 2003

Abstract

A single cylinder Diesel engine study of water-in-Diesel emulsions was conducted to investigate the effect

of water emulsification on the engine performance and gases exhaust temperature. Emulsified Diesel fuels

of 0, 5, 10, 15 and 20 water/Diesel ratios by volume, were used in a single cylinder, direct injection Diesel

engine, operating at 1200–3300 rpm. The results indicate that the addition of water in the form of emulsion

improves combustion efficiency. The engine torque, power and brake thermal efficiency increase as the

water percentage in the emulsion increases. The average increase in the brake thermal efficiency for 20%

water emulsion is approximately 3.5% over the use of Diesel for the engine speed range studied. The proper

brake specific fuel consumption and gases exhaust temperature decrease as the percentage of water in theemulsion increases.

� 2003 Elsevier Ltd. All rights reserved.

Keywords: Emulsified fuel; Diesel fuel; Engine performance; Diesel engine; Gases exhaust temperature

1. Introduction

Recently, the emphasis on fuel conservation and reduction of undesirable emissions has gen-erated much interest in utilizing water-in-oil emulsions in conventional liquid fueled combustors.It has been demonstrated experimentally that the use of oil–water emulsions produces somesignificant effects in the combustion of liquid fuels. Ref. [1] shows that the total duration of burn,the volume of the oil residue and the burn efficiency decrease with increasing water content of theemulsion in a laboratory scale tests for combustion of water-in-oil emulsions of Diesel. Ref. [2]concluded that the use of oil–water emulsions is an effective method for the reduction of

* Fax: +962-6-4654061.

E-mail address: [email protected] (M. Abu-Zaid).

0196-8904/$ - see front matter � 2003 Elsevier Ltd. All rights reserved.

doi:10.1016/S0196-8904(03)00179-1

mail to: [email protected]

698 M. Abu-Zaid / Energy Conversion and Management 45 (2004) 697–705

particulate emission in heavy oil combustion. Ref. [3] measured a significant reduction in NOx andsoot when performing experiments on internal combustion engines using emulsion fuels.

A theoretical study on emulsified droplet combustion [4] indicates that the combination of ahigh pressure environment and a high boiling temperature fuel is particularly favorable in en-hancing smoke reduction. It is, therefore, logical to expect that water–oil emulsions are parti-cularly suitable for applications in Diesel engines, where high pressure combustion exists, arelatively non-volatile fuel is used and a serious smoke emission problem exists [5].

Several Diesel engine tests using water/oil emulsions have been conducted. The combustioncharacteristics of various water–Diesel emulsion fuels were investigated in a rapid compressionand expansion machine [6]. They found that the best performance of the machine with respect toefficiency and NOx and soot emissions was when operating at 40% water by volume. Dyna-mometer tests conducted on a Diesel engine using emulsions with 5% and 10% of water by vol-ume, showed no obstacles to the operation of the Diesel engine during a series of steady stateengine tests and the twenty hour endurance tests [7]. The results show that the accumulation ofwear metal debris in crankcase oil samples as lower with emulsion than with the baseline ordinaryDiesel fuel. An experimental investigation has been conducted to study the effects of using water/diesel emulsion fuel on heat flow and thermal loading in a Diesel engine [8]. It was found that theaddition of water to Diesel fuel has a great influence on reducing the heat flux, the metal tem-peratures and the thermal loading of combustion chamber components.

While the use of emulsified fuel in Diesel engines has been an active area of research in recentyears, some of these studies have only measured external effects on exhaust emissions, and othersmeasured effects on thermal loading metal wear and fuel consumption. However, to the bestknowledge of the author, there has been no systematic investigation of the effects on the engineperformance. The aim of the present work is to investigate experimentally the effect of the wateraddition in the form of emulsion on the performance of a Diesel engine.

2. Experimental procedure

The engine used was the PETTER PHIW single cylinder, direct injection engine. The enginespecifications are listed in Table 1.

Engine torque was measured by an electric dynamometer, the instantaneous speed was readthrough a digital counter and the exhaust temperature was measured using a thermocouplelocated downstream of the exhaust valve. In addition, fuel consumptions was measured.

The water-in-diesel emulsions consisting of Diesel fuel and ordinary tap water, were prepared inan electrical blender at a speed of about 1500 rpm. To stabilize the emulsions, a 2% by volume

Table 1

Engine specifications

Type PETTER PHIW, single cylinder engine

Bore 87.3 mm

Stroke 110 mm

Swept volume 659 cc

Compression ratio 17

M. Abu-Zaid / Energy Conversion and Management 45 (2004) 697–705 699

surfactant mixture consisting of Span 80 and Tween 80 was used [9]. Six blends were tested: pureDiesel, Diesel fuel plus surfactant and Diesel fuel plus surfactant plus 5%, 10%, 15% and 20%water by volume. For each run the engine was started on pure Diesel and then switched to the testblend, All tests were performed at constant load, variable engine speed and constant injectiontiming of 13� BTDC.

3. Experimental errors

Three runs of tests were performed under identical conditions to check for the repeatability ofall results. In general, the repeatability of the results was found to be within 4%. Each reading ofthe basic quantities measured is the average of three values.

The error in the measurement of the engine torque is ±0.1 Nm. Hence, the uncertainty in thetorque values is in the range 0.77–0.94%. The error in the measured value of the instantaneousspeed of the engine may be estimated by considering the error in the digital counter. Such an erroris ±1 rpm. Thus, the uncertainty in the values of rpm are estimated to be in the range 0.03–0.083%.

The error in the measurement of the fuel mass flow rate may be estimated by considering theerror in the measurement of the time used for the engine to consume 25 cc of fuel. The timer usedhas a resolution of 0.1 s. Thus, the uncertainty in the values of the fuel mass flow rate is estimatedin the range 0.167–0.25%. The error in the measurement of the gases exhaust temperature may beestimated by considering the error in the thermocouple used. Such an error is 2.2 �C or 0.75%,which ever is greater. Hence, the uncertainty in the measurement of the gases exhaust temperatureis estimated to be in the range 2.96–4.39%.

An error analysis for the derived quantities, such as power, brake specific fuel consumption andthermal efficiency, based on the method of Kline and McClintrok [10] was performed. The erroranalysis indicates that the uncertainty in such quantities is in the range 4–6%. It is clear that theestimated error in the measurement of the basic and derived quantities do not significantly in-fluence the overall uncertainty in the final results.

4. Results and discussion

The effect of water addition in the form of emulsions on the engine output torque for variousspeeds is shown in Fig. 1. The torque is a function of engine speed. At low speed, torque increasesas the engine speed increases, reaches a maximum and then, as engine speed increases further,torque decreases as shown in Fig. 1. The torque decreases because the engine is unable to ingest afull charge of air at the higher speeds. It is clear from Fig. 1 that as the percentage of water in theemulsion increases, the torque produced increases. This may be attributed to the additional forceon top of the piston provided by the pressure exerted by the steam. When the charge is fired in thecylinder, the water would turn to high pressure steam. In addition, the higher viscosity of theemulsified fuel than that of the base fuel [11] and the presence of water promote a finer, cloud likeatomization of the emulsified mixture during injection. Resulting in improving combustion effi-ciency significantly, Dryer [12] states that the water in the emulsified fuel improves the combustion

10

10.5

11

11.5

12

12.5

13

13.5

1200 1500 1800 2100 2400 2700 3000 3300

Engine speed (rpm)

Torq

ue (N

.m)

DieselDiesel+surfactantDiesel+surfactant+5% waterDiesel+surfactant+10% waterDiesel+surfactant+15% waterDiesel+surfactant+20% water

Fig. 1. Engine torque output versus engine speed using water–diesel emulsions.

1.5

2

2.5

3

3.5

4

1200 1500 1800 2100 2400 2700 3000 3300Engine speed (rpm)

Pow

er o

utpu

t (K

W)


Fig. 2. Engine power output versus engine speed using diesel–water emulsions.


process owing to the simultaneous additional braking of the droplets, to the increase in evapo-ration surface of the droplets and to better mixing of the burning fuel in air.

The effect of the emulsions on the engine power is shown in Fig. 2. The power increases to amaximum and then decreases at higher speeds. This is because friction losses increase with speed


and become the dominant factor at very high speeds. Maximum power occurs at 3000 rpm asshown in Fig. 2, whereas the maximum torque occurs at 1500 rpm as shown in Fig. 1. Obert [13]has reported that torque peaks usually at a speed about half that of power. Fig. 2 shows that thepower increases slightly as the water percentage increases. The increase in power output for theemulsions is because water in the emulsion influences combustion of the fuel. Harbach and Agosta[14] found that the introduction of water in Diesel for a single cylinder engine prolongs the ig-nition delay. The ignition delay period is when the fuel that has been injected into the cylinder isundergoing chemical and physical preparation for combustion. Thus, the emulsion fuel requiresless compression (negative) work than the Diesel fuel due to the longer ignition delay during thecompression stroke. This helps to reach a higher peak pressure after TDC to produce more poweroutput during the expansion stroke. In addition, when the ignition delay increases, more Dieselwould be physically prepared (evaporation, mixing) for chemical reaction, which increases theamount of Diesel burned and the rate of heat release in the premixed burning. This results inenhancement of combustion and improvement of combustion efficiency.

The variation of brake specific fuel consumption (BSFC) with engine speed for the differentemulsions is shown in Figs. 3 and 4. Two conventions are adopted for the BSFC. The first iscalculated by considering the Diesel fuel plus water as the total fuel, shown in Fig. 3. The secondis the proper value calculated by considering the total fuel as strictly the amount of Diesel that isburned, shown in Fig. 4. The BSFC in both figures decreases as engine speed increases, reaches aminimum and then increases at high speeds. At low speeds, the heat loss to the combustionchamber walls is proportionately greater and combustion efficiency is poorer, resulting in higherfuel consumption for the power produced. At high speeds, the friction power is increasing at a

0.3

0.32

0.34

0.36

0.38

0.4

1200 1500 1800 2100 2400 2700 3000 3300Engine speed (rpm)

Bra

ke s

pesi

fic fu

el c

onsu

mpt

ion

(Kg/

KW

.hr)

DieselDiesel+surfactantDiesel +sufactant+5% waterDiesel+surfactant+10% waterDiesel+surfactant+15% waterDiesel+surfactant+20% water

Fig. 3. Brake specific fuel consumption versus engine speed using diesel–water emulsions by considering diesel +water

as total fuel.

0.25

0.3

0.35

0.4

1200 1500 1800 2100 2400 2700 3000 3300

Engine speed (rpm)

Bra

ke s

peci

fic fu

el c

onsu

mpt

ion

(Kg/

KW

.hr) Diesel

Diesel+surfactant

Diesel+surfactant+5% water




Fig. 4. Brake specific fuel consumption versus engine speed using diesel–water emulsions by considering diesel as total

fuel.


rapid rate, resulting in a slower increase in the power than in fuel consumption with a consequentincrease in BSFC. Fig. 3 shows that as the percentage of water in the emulsion increases, theBSFC increases. This is because, as the percentage of water in the emulsion increases, a largeramount of Diesel is displaced by an equal amount of water. This means that less Diesel fuel isactually contained within each volume of the emulsion. It is clear from Fig. 4 that as the per-centage of water in the emulsion increases, the BSFC decreases. The minimum value occurs whenthe percentage of water is 20%. Tsukahara and Yoshimoto [15] have also reported a reduction inBSFC in a Diesel engine fueled by emulsion fuel. The reduction in BSFC with water emulsifiedDiesel may be attributed to formation of a finer spray due to rapid evaporation in the water,longer ignition delay results in more fuel burning in premixed combustion and suppression ofthermal dissociation due to lower cylinder average temperature. The evaporation and additionalmass of water cause the cylinder average temperature to become lower as the water amount wasincreased. Hsu [16] found that water lowers the maximum cylinder average temperature in amedium speed Diesel engine.

Fig. 5 shows the effect of emulsion on the brake thermal efficiency. As expected, the maximumincrease in brake thermal efficiency occurs when 20% water in the emulsion is used, and this is dueto the fact that the BSFC was at its minimum value, as shown in Fig. 4. The average increase inbrake thermal efficiency for 20% water emulsion is approximately 3.5% over the use of Diesel forthe engine speed range studied. Ganesan and Ramesh [17] found that the emulsion (0.3:1 by mass)led to an improvement in brake thermal efficiency of �3% over the use of Diesel fuel for a singlecylinder air cooled Diesel engine. Sawa and Kajitani [11] demonstrated experimentally that awater/oil emulsified fuel increases the brake thermal efficiency in internal combustion engines.

20

22

24

26

28

30

32

1200 1500 1800 2100 2400 2700 3000 3300

Engine speed (rpm)

Bra

ke th

erm

al e

ffici

ency

%


Fig. 5. Brake thermal efficiency versus engine speed using diesel–water emulsions.

390

430

470

510

550

590

1200 1500 1800 2100 2400 2700 3000 3300Engine speed (rpm)

Gas

es e

xhau

st te

mpe

ratu

res

( o C)


Fig. 6. Gases exhaust temperatures versus engine speed using diesel–water emulsions.


The variation of the gases exhaust temperature with engine speed for the different emulsions isshown in Fig. 6. It is clear that as the percentage of water in the emulsion increases, the exhausttemperature decreases. The heat absorbed by the additional water can explain the decrease in the


exhaust temperature. The latent heat of water will cool the charge due to the evaporation of water,and the cylinder average temperature following injection and before ignition becomes lower as thewater percentage increases. This results in lower peak combustion temperatures. Park et al. [6]show a lower flame temperature with increasing water–oil ratio in a Diesel engine.

The addition of 2% surfactant to the emulsions seems to have almost negligible effects on theengine power output, BSFC, brake thermal efficiency and gases exhaust temperatures as shownin Figs. 2–6.

5. Conclusions

From this study, it may be concluded that the addition of water in the form of emulsion im-proves the combustion efficiency in the Diesel engine, hence the performance of the engine. As thewater percentage in the emulsion increases up to 20% by volume, the engine torque, power andbrake thermal efficiency increase. The average increase in the brake thermal efficiency for 20%water emulsion is approximately 3.5% over the use of Diesel for the engine speed range studied.The BSFC calculated by considering the total fuel as strictly the amount of Diesel fuel that isburned and the gases exhaust temperature decrease as the percentage of water increases. Also, itwas found that the addition of 2% surfactant to the emulsions seems to have almost negligibleeffects on the engine performance parameters measured.

References

[1] Walavalkar AY. Combustion of water-in-oil emulsions of Diesel and fresh and weathered crude oil floating on

water, PhD Thesis, August 2001, The Pennsylvania State University.

[2] Ballester JM, Fueyo N, Dopazo C. Combustion characteristics of heavy oil–water emulsions. Fuel 1996;75(6):

695–705.

[3] Gunnerman RW, Russel RL. Emission and efficiency benefits of emulsified fuels to internal combustion engines.

SAE technical paper 1997; 972099.

[4] Law CK. A model for the combustion of water/oil emulsion droplets. Combust Sci Technol 1977;17:29.

[5] Cook DH, Law CK. A preliminary study on the utilization of water-in-oil emulsions in Diesel engines. Combust

Sci Technol 1978;18:217–21.

[6] Park JW, Huh KY, Park KH. Experimental study on the combustion of emulsified diesel in a RCEM. World

Automotive Congress 2000 FISITA; F 2000A073 Korea.

[7] Sii HS, Masjuki H, Zaki AM. Dynamometer evaluation and engine wear characteristics of palm oil Diesel

emulsions. J Am Oil Chem Soc 1995;72(8):905–9.

[8] Selim MY, Elfeky SM. Effects of Diesel/water emulsion on heat flow and thermal loading in a precombustion

chamber Diesel engine. Appl Thermal Eng 2001;21(15):1565–82.

[9] Abu-Zaid M. An experimental study of the evaporation characteristics of emulsified liquid droplets. Heat Mass

Transfer J. Accepted for publication.

[10] Holman JP. Experimental methods for engineers. 5th ed. McGraw-Hill, Inc.; 1989. p. 41.

[11] Sawa N, Kajitani S. Physical properties of emulsion fuel (water-oil-type) and its effect on engine performance under

transient operation. International Congress and Exposition. Detroit 1992:97–107.

[12] Dryer FL. Water addition to practical combustion system––concepts and applications. 16th Combust Symp (Int)

1976:279–95.

[13] Obert E. Internal combustion engines and air pollution. Harper & Row, Publishers; 1973.


[14] Harbach J, Agosta V. Effects of emulsified fuel on combustion in a four-stroke Diesel engine. J Ship Res

1991;35(4):356–63.

[15] Tsukahara M, Yoshimoto Y. Reduction of NOx, smoke, BSFC and maximum combustion pressure by low

compression ratio in a Diesel engine fuelled by emulsion fuel. International Congress and Exposition. Detroit,

Publ.; SAE: 1992. p. 71–7.

[16] Hsu BD. Combustion of water-in-Diesel emulsion in an experimental medium speed Diesel engine. SAE paper

860300. 1987:2.285–96.

[17] Ganeson S, Ramesh A. An experimental study of the characteristics of a LPG- based dual-fuel engine using a

water/Diesel emulsions as the pilot fuel. J Inst Energy 2002;75(502):2–10.

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