Energy Conversion and Management 94 (2015) 84–94

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Energy Conversion and Management

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Effect of n-butanol and diethyl ether as oxygenated additiveson combustion–emission-performance characteristics of a multiplecylinder diesel engine fuelled with diesel–jatropha biodiesel blend

http://dx.doi.org/10.1016/j.enconman.2015.01.0470196-8904/� 2015 Elsevier Ltd. All rights reserved.

⇑ Corresponding authors. Tel.: +60 146985294; fax: +60 3 79675245 (S. Imtenan).Tel.: +60 3 79675245; fax: +60 3 79675245 (H.H. Masjuki). Tel.: +60 3 79674448;fax: +60 3 79675245 (I.M. Rizwanul Fattah).

E-mail addresses: sayeed.imtenan@gmail.com (S. Imtenan), masjuki@um.edu.my (H.H. Masjuki), rizwanul.buet@gmail.com (I.M. Rizwanul Fattah).

S. Imtenan ⇑, H.H. Masjuki ⇑, M. Varman, I.M. Rizwanul Fattah ⇑, H. Sajjad, M.I. ArbabCentre for Energy Sciences, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

a r t i c l e i n f o

Article history:Received 1 November 2014Accepted 18 January 2015Available online 7 February 2015

Keywords:Diesel–biodiesel blendn-ButanolDiethyl etherCombustionEngine performance-emission

a b s t r a c t

Jatropha biodiesel is considered as one of the most prospective renewable energy sources of Malaysia inrecent years. Hence, an investigation was conducted for the improvement of jatropha biodiesel–dieselblend with the addition of 5–10% n-butanol and diethyl ether by vol. which are commonly known as oxy-genated cold starting additive. Engine tests were conducted at variable speed, ranging from 1000 rpm to3000 rpm at constant 80 N m torque on a 4-cylinder turbocharged indirect injection diesel engine. Engineperformance parameters like brake specific fuel consumption, brake specific energy consumption, brakethermal efficiency and engine emissions like carbon monoxide, unburned hydrocarbons, nitrogen oxideand smoke opacity were measured. Performance and exhaust emissions variation of the modified blendsfrom the baseline fuel (jatropha biodiesel–diesel blend) were compared for the assessment of theimprovement quantitatively. In-cylinder pressure diagram of all the test fuels were acquired and the heatrelease rate analysis was conducted at different operating conditions to explore the features of combus-tion mechanism and correlate them with the performance and emission characteristics to acquirebetter understanding of the scenario. However, in a nut-shell, the investigation reveals the potential ofn-butanol and diethyl ether to be used as the additive of jatropha biodiesel–diesel blend in the contextof combustion, performance and emission characteristics.

� 2015 Elsevier Ltd. All rights reserved.

1. Introduction

Biodiesel refers to the fatty acid methyl esters which arederived from lipid substances from oils, fats, waste greases, recy-cled oils, etc. To produce biodiesel, vegetable oils of edible originwere treated as one of the potential feedstocks once. Due to foodvs. fuel controversy of usage of edible oil for fuel production, othersources e.g. non-edible oils of plant origin with high free fatty acid(FFA) content, etc. are now being used for biodiesel production.Malaysia is one of the leading palm oil producers in the world[1]. In addition, it also facilitates the use of palm oil as fossil dieselreplacement. The government of Malaysia has recently mandatedthe use of 5% palm biodiesel with diesel nationwide for all dieselvehicle [2]. However, because of the edible nature of the palmoil, recently jatropha has drawn immense attention of both private

and government sectors in Malaysia. Jatropha curcas is non-ediblein nature, physicochemical properties of its biodiesel are quite sim-ilar to the palm biodiesel and most interestingly, it has beenreported as one of the best contestants of cheap biodiesel sourcein future [3]. Hence, Malaysian government started a project con-cerning jatropha cultivation and economic viability study of jatro-pha biodiesel production [4]. It has been reported that, ForestResearch Institute of Malaysia (FRIM) has completed a 6000J. curcas tree plantation project and the agency has confirmed thatit is ready to proceed to commercial scale [5]. Therefore, being aprospective non-edible renewable energy source with satisfactoryphysicochemical properties, jatropha biodiesel deserves profoundinvestigation regarding its viability in the diesel engines.

Many experiments were done with neat jatropha biodiesel or itsblends with diesel to study their effects on engine performance andemission characteristics. Huang et al. [6] studied with jatropha bio-diesel and reported 3.6% higher brake thermal efficiency (BTE)compared to diesel at higher loads in expense of higher brake spe-cific fuel consumption (BSFC). Sundaresan et al. [7] also found fromtheir study that the engine efficiency and BSFC for jatropha wereinferior to that of diesel fuel. However, pre-heating and blending

Table 1GC operating condition for determination of fatty acid composition.

Item Specification

Column 0.32 mm ⁄ 30 m, 0.25 lmInjection volume 1 lmCarrier gas Helium, 83 kPaInjector Split/splitless 1177, full EFC controlTemperature 250 �CSplit flow 100 mL/minColumn 2 flow Helium at 1 ml/min constant flowOven 210 �C isothermalColumn temperature 60 �C for 2 min

10 �C/min to 200 �C5 �C/min to 240 �CHold 240 �C for 7 min

Detector 250 �C, FID, full EFC control

S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94 85

with diesel have been reported conducive for engine performancecharacteristics [8]. Manieniyan and Sivaprakasam [9] reported sig-nificant improvement of performance while they tried 20% blend ofjatropha biodiesel which was also supported by the work of Sahooet al. [10]. Therefore, blending with petroleum diesel as a singlebiodiesel [11] or as an optimized multiple biodiesel blend [12]have already been studied by several researchers.

The problems associated to biodiesel is its high viscosity andauto ignition temperature (AIT) compared to that of diesel. To min-imize these drawbacks as well as to increase the fuel bound oxygen(to facilitate combustion) and to keep lubricity at reasonable levels,oxygenated additives such as n-butanol and diethyl ether (DEE) areusually added in a small portion [13]. n-butanol has emerged as apotential oxygenated additive to improve the fuel properties ofboth diesel and biodiesels recently. n-butanol, also better knownas 1-butanol, is produced from alcoholic fermentation of biomassfeedstocks [14]. Hence, it is a renewable additive with astraight-chain structure with the OH group at the terminal carbon.n-butanol is a strong competitor of ethanol and has less hydrophilictendency, higher cetane number, higher miscibility with diesel andbiodiesels and higher calorific value [15]. Yao et al. [16] investigatedthe influence of n-butanol-diesel blend on the performance andemissions of a heavy-duty diesel engine with multi-injection andvarious EGR (exhaust gas recirculation) ratios. They reported that,the soot and CO emissions can be improved by the addition ofn-butanol without a severe impact on the BSFC. Altun et al. [17]studied the effect of n-butanol on cottonseed biodiesel–diesel blendand reported that, emissions of NOx, HC and CO reduced in expenseof higher BSFC. Lebedevas et al. [18] experimented with butyl estersof rapeseed oil-diesel blend with the addition of 15–25% n-butanoland reported improvement on emission characteristics and overallefficiency factor. In their study, Mehta et al. [19] studied the effectof varying percentage of n-butanol with jatropha biodiesel–dieselblend and reported significant reduction in CO and NO emissionin expense of lower engine performance. However, they did notanalyse their data with sufficient insight on combustion phenom-ena at each condition. Thus, the disadvantage of higher viscosityof biodiesel and the lower cetane number of n-butanol than biodie-sel can be offsetted with the addition of n-butanol as additive.

Diethyl ether is another biomass based oxygenated additiveproduced from ethanol, which is produced itself from biomass[20]. It is a colorless liquid with high volatility and flammability.It has got very high cetane number, reasonable energy densityand low AIT with high oxygen content. It has high miscibility withboth diesel and biodiesel. Consequently, it is very much suitable tobe used in diesel engine either with diesel or biodiesels [21]. Manyresearchers have studied diesel-DEE blend to improve the perfor-mance and emission characteristics. Blending with neat biodieselor biodiesel–diesel blend has also been tried by the researchers.Babu et al. [22] evaluated the effect of DEE on mahuva methyl esterand reported that, CO and smoke emission decreased more than50% after addition of DEE. Sivalaksmi and Balusamy [23] added5–15% DEE on neat neem biodiesel and reported improvement ofBSFC and BTE. Qi et al. [24] studied effect of 5% DEE addition withsoybean biodiesel–diesel blend. They observed significantly lowerCO emission with better BSFC with the addition of DEE into the die-sel–biodiesel blend. Thus, it can be concluded that, addition of DEEresults in improved performance and emission characteristics ofdiesel engines.

Jatropha biodiesel has the potential to be used as partialreplacement of diesel in Malaysia after palm oil. Therefore, anattempt was taken previously by the authors for the improvementwith the addition of n-butanol and DEE [4]. On that investigation itwas observed that addition of 5% n-butanol and DEE improved thebrake power (3.5%), brake thermal efficiency (3.4%) and alsoreduced the emissions of NOx (9%), CO (20%) and smoke opacity

(22%) of the modified blends than J20 blend on average with anunmodified single cylinder diesel engine. Apart from that, thereis an absence of comparative study in the literature on the effectsof higher percentages of n-butanol and DEE as additives on jatro-pha biodiesel–diesel blends on multiple cylinder engines. There-fore, in the present investigation the authors have attempted toincrease the percentage of n-butanol and DEE in the quest of study-ing the effects in a four cylinder, water cooled turbocharged dieselengine. In addition, combustion analysis has been incorporated atdifferent operating conditions to get in-depth understanding ofthe combustion mechanisms and their correlation with the perfor-mance and emission characteristics. Cost analysis of all the modi-fied blends have also been incorporated into this study toprovide an economic comparison of different tested fuels.

2. Materials and method

2.1. Feedstock and additive

FRIM (Forest Research Institute Malaysia) supplied the jatrophabiodiesel. n-butanol and DEE were purchased from Nacalai Tesque,Inc., Kyoto, Japan; certified as 99.5% pure. Petroleum diesel wassupplied from the local market supplier.

2.2. Fatty acid composition (FAC)

In this investigation Shidmadzu, GC-2010A series gas chro-matograph was used to explore the FAC of jatropha biodiesel.Tables 1 and 2 show the GC operating conditions and the FACresults of the biodiesel. Jatropha biodiesel contains 24.3% satu-rated, 42.6% mono-unsaturated and 33.1% poly-unsaturatedmethyl esters. Higher portion of saturation indicates higher oxida-tion stability and CN (cetane number). On the contrary it also indi-cates lower iodine value and CFPP according to the literaturereview [25].

2.3. Test fuels

The preparation of the test fuels and characterization of theproperties were carried out at the Engine Tribology Laboratory,Department of Mechanical Engineering, University of Malaya. Atotal of six test fuels were selected for this investigation. The testfuels were (a) 100% petroleum diesel, (b) 20% Jatrophabiodiesel + 80% diesel (J20), (c) 15% Jatropha biodiesel + 5% n-butanol + 80% diesel (J15B5), (d) 10% Jatropha biodiesel + 10%n-butanol + 80% diesel (J10B10), (e) 15% Jatropha biodiesel + 5%DEE + 80% diesel (J15D5), (f) 10% Jatropha biodiesel + 10%DEE + 80% diesel (J10D10). The proportions mentioned here wereall volume based. Diesel and biodiesel blending was completed

Table 2Fatty acid composition of biodiesels.

FAME Structure Molecular weight Formula JBD (wt.%)

Methyl laurate 12:00 214.34 CH3(CH2)10COOCH3 0Methyl myristate 14:00 242.4 CH3(CH2)12COOCH3 0.1Methyl palmitate 16:00 270.45 CH3(CH2)14COOCH3 17.7Methyl palmitoleate 16:01 268.43 CH3(CH2)5CH@CH(CH2)7COOCH3 0.8Methyl stearate 18:00 298.5 CH3(CH2)16CO2CH3 6.4Methyl oleate 18:01 296.49 CH3(CH2)7CH@CH(CH2)7COOCH3 41.8Methyl linoleate 18:02 294.47 CH3(CH2)3(CH2CH@CH)2(CH2)7COOCH3 32.9Methyl linolenate 18:03 292.46 CH3(CH2CH@CH)3(CH2)7COOCH3 0.2Methyl archidate 20:00 326.56 CH3(CH2)18COOCH3 0.1Methyl eicosenoate 20:01 324.54 CH3(CH2)16CH@CHCOOCH3 0Methyl behenate 22:00 354.61 CH3(CH2)20COOCH3 0Methyl lignocerate 24:00 382.66 CH3(CH2)22COOCH3 0Saturation 24.3Mono-unsaturation 42.6Poly-unsaturation 33.1Unsaturation 75.7

86 S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94

by a blending machine at 4000 rpm for 15–20 min. As n-butanoland DEE are volatile in nature, after addition of n-butanol andDEE, the blends were taken into a closed container and shakedwith a shaker machine for about 30 min.

2.4. Equipment for fuel property test

Table 3 shows the list of the equipment used to measure thephysicochemical properties of the base fuels (diesel and biodiesels)and fuel blends. The following equations were used to calculate thesaponification number (SN), iodine value (IV) and cetane number(CN) of the biodiesel [25].

SN ¼X 560� Ai

MWi

� �ð1Þ

IV ¼X 254� D� Ai

MWi

� �ð2Þ

CN ¼ 46:3þ 5458SN

� �� ð0:225� IVÞ ð3Þ

Here, Ai = percentage of each component, D = number of doublebonds, MWi = mass of each component. Molecular weight of eachcomponent is given in Table 2.

2.5. Fuel properties

Tables 4 and 5 show the physicochemical properties of the basefuels and the blends respectively. Each property was tested severaltimes and then mean value was taken.

Kinematic viscosity of the biodiesels depends on the fatty acidprofile [28]. Table 4 shows that, kinematic viscosity of the jatrophabiodiesel satisfies the ASTM-D6751 and EN 14214 standards.

Table 3Equipment of fuel property test.

Property Equipment

Kinematic viscosity at 40 �C SVM 3000-automaticDensity at 40 �C SVM 3000-automaticFlash point Pensky–Martens flash point-automatic NPM 440Oxidation stability 873 Rancimat-automaticHigher heating value C2000 basic calorimeter-automaticCloud point Cloud and Pour point tester-automatic NTE 450Pour point Cloud and Pour point tester-automatic NTE 450CFPP Cold filter plugging point-automatic NTL 450Acid value G-20 Rondolino automated titration system

Though jatropha biodiesel is meeting the standard, still it is 15%higher than the diesel fuel. From Table 5 it can be seen that, addi-tion of n-butanol and DEE reduced the value of kinematic viscosi-ties of the modified blends at best 26%. All the blends meet theASTM D7467 standard of viscosity. Lower kinematic viscosity issupposed to assist the modified blends to get better atomizationduring the injection than the J20 blend.

Density of the jatropha biodiesel was 3.4% higher than dieselfuel. However, blending with diesel (J20) reduced the density tosome extent. Compared to J20, n-butanol and DEE blends showedfurther reduction. Up to 4.4% reduced density was observed forthe modified blends than J20. Increasing portion of n-butanol andDEE reduced the density accordingly which made the values muchsimilar to diesel fuel.

The calorific value of jatropha biodiesel was lower than diesel asexpected. On top of that, calorific values of n-butanol and DEE wereeven lower than the biodiesel. Consequently, all the blends J20,J15B5, J10B10, J15D5 and J10D10 showed lower calorific valuesthan diesel, yet the values were only 2.95% lower on average thandiesel.

Flash point of the jatropha biodiesel was very much higher thandiesel fuel, which is positive in terms of transportation and han-dling. Flash points of n-butanol and DEE were very low, thereforemodified blends showed quite lower flash points than J20. How-ever, generally a flash point higher than 66 �C is considered as safe[29] and on top all the modified blends satisfy the ASTM D7467standard for flash point. Therefore, in this study it can be said thatall the fuels were safe to handle.

The cloud point and pour point values are of limited concern intropical and hot countries of Asia, but it has much greater impor-tance in countries where the weather is cold. It can be seen fromTable 4 that cloud point and pour point of jatropha biodiesel wasquite higher than the diesel. However, as the n-butanol and DEE

Manufacturer Standardmethod

ASTM D6751limit

Accuracy

Anton Paar, UK D7042 1.9–6.0 ±0.35%Anton Paar, UK D7042 n.s. 0.0005 g/cm3Normalab, France D93 130 min ±0.1 �CMetrohm, Switzerland EN 14112 3 h ±0.01 hIKA, UK D240 n.s. ±0.1% of readingNormalab, France D2500 Report ±0.1 �CNormalab, France D97 ±0.1 �CNormalab, France D6371 n.s.Mettler Toledo, Switzerland D664 0.5 max ±0.001 mg KOH/g

Table 4Property of the base fuels.

Property Unit Diesel JBD n-butanolc Diethyl etherc ASTM D6751a EN 14214b

Kinematic viscosity at 40 �C mm2/s 3.46 4.27 3.00 0.22 1.9–6.0 3.5–5.0Density at 40 �C kg/m3 833 861 812 712 n.s. n.s.Lower heating value MJ/kg 44.66 39.83 34.33 33.89 n.s. n.s.Oxidation stability h 59.10 3.11 – 3 (min) 6 (min)Flash point �C 69.5 202.5 35 �40 130 (min) 120 (min)Cloud point �C 8 3 report n.s.Pour point �C 7 2 �89 – n.s. n.s.CFPP �C 8 8 n.s. n.s.Acid value Mg KOH/g – 0.18 – 0.5 (max) 0.5 (max)Saponification number (SN) 192.6 – n.s. n.s.Iodine value (IV) G I2/100 g 93.8 – n.s. 120Cetane number (CN) 48 53.5 25 �125 47 (min) 51 (min)

n.s. = not specified.a Data obtained from [26].b Data obtained from [27].c Provided by the supplier, measured at 20 �C.

Table 5Property of the fuel blends.

Property Diesel J20 J15B5 J10B10 J15D5 J10D10 ASTM D7467

Kinematic viscosity at 40 �C 3.46 3.60 3.29 3.24 3.22 3.15 1.9–4.1Density at 40 �C 833 837 834 831 830 823 n.s.

Lower heating valueMJ/kg 44.66 43.69 43.40 43.15 43.39 43.10 n.s.Flash point �C 69.5 96.5 87.5 79.5 83.5 71.5 52 (min)

S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94 87

are well accepted as the cold starting additives, it is not necessaryto measure the cloud point and pour point of the modified blends[30].

2.6. Experimental setup

This investigation was performed using an inline four-cylinder,water-cooled, turbocharged diesel engine without any catalyticconverter. Schematic diagram of the test setup is given in Fig. 1.Engine specifications are listed in Table 6. An eddy current dyna-mometer, which can be operated at a maximum power of250 kW was coupled to the engine. Measurement of HC, NO andCO emissions were conducted by Bosch BEA-350 exhaust gas ana-lyzer. Smoke opacity was measured by Bosch RTM 430 smokeopacimeter. The method for measuring the HC and CO emissions

Fig. 1. Schematic diagram

was Non-dispersive infrared and the method for NO was electro-chemical. Smoke opacity was measured by photodiode receivermethod.

Engine performance and emission tests were carried out vary-ing the engine speed ranging from 1000 to 3000 rpm at constant80 N m torque. For data acquisition, REO-DEC data control systemwas used, which was monitored with the help of REO-DCA soft-ware. Measured engine performance parameters of this investiga-tion were BSFC (brake specific fuel consumption), BSEC (brakespecific energy consumption) and BTE (brake thermal efficiency).

2.7. Combustion characteristics analysis

The test system was equipped with necessary sensors for com-bustion analysis. In-cylinder pressure was measured by using a

of the engine test bed.

Table 6Engine testbed equipment specification.

Description Specification

No. and arrangement ofcylinders

4 in-line, longitudinal

Rated power 65 kW at 4200 rpmCombustion chamber Swirl chamberTotal displacement 2477 ccCylinder bore � stroke 91.1 � 95 mmValve mechanism SOHCCompression ratio 21:1Lubrication system Pressure feed, full flow filtrationFuel system Distributor type injection pumpAir flow TurbochargedFuel injection pressure 157 barDynamometer Froude Hofmann eddy current

dynamometerMax. Power: 250 kWMax. Torque: 1200 N mMax. Speed: 6000 rpm

Fuel flow meter Positive displacement flow meter

Table 7Measurement accuracy and uncertainty.

Measured quantity Upper limit Accuracy Uncertainty (%)

Fuel flow 36 l/h ±0.02 l/h –Speed 6000 rpm ±2 rpm –Power 250 kW ±0.02 kW –Smoke opacity 100% 0.1% ±0.5%CO 10.00 vol% 0.02 vol% ±0.01 vol%HC 9999 ppm vol 1 ppm vol ±1 ppmNO 5000 ppm vol 1 ppm vol ±5 ppm

88 S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94

Kistler 6058A type pressure sensor. It was installed in the swirlchamber through the glow plug port. Kistler 2614B4 type chargeamplifier was used to amplify the charge signal outputs from thepressure sensor. A high precision incremental encoder (2614Atype) was used to acquire the top dead center (TDC) position andcrank angle signal for every engine rotation. Simultaneous sam-plings of the cylinder pressure and encoder signals were performedby a computer with Dewe-30-8-CA data acquisition card. One hun-dred consecutive combustion cycles of pressure data were col-lected and averaged to eliminate cycle-to-cycle variation in eachtest. To reduce noise effects, Savitzky–Golay smoothing filteringwas applied to the sampled cylinder pressure data. Other combus-tion parameters, such as heat release rate and start of combustion(SOC) were computed by using Matlab� R2009a software.

Heat release rate (HRR) analysis is the most effective way togather information for the combustion mechanism in dieselengines. This method simplifies the identification of start of com-bustion (SOC) timing and differences in combustion rates fromthe HRR versus crank angle diagram [31]. Hence, HRR analysis isa significant parameter in understanding the combustion mecha-nism. Average in-cylinder pressure data of 100 consecutive cycleswith a 0.1 crank angle (CA) resolution were used to calculateHRR. Analysis was derived from the first law of thermodynamics,as shown in Eq. (4), without taking into account heat loss throughcylinder walls. Here, main combustion chamber and pre-combustion chamber were considered to be combined into a singlezone thermodynamic model. It is expected that, in between thetwo chambers, there is no passage throttling losses. Fuel vaporiza-tion and mixing, temperature gradients, non-equilibriumconditions and pressure waves can be ignored [32].

dQdh¼

V dPdh þ cP dV

dh

c� 1ð4Þ

where dQdh ¼ rate of heat release (J/�CA), V = instantaneous cylinder

volume (m3), h ¼ crank angle (�CA), P = instantaneous cylinder pres-sure (Pa), c ¼ specific heat ratio which is considered constant at1.35 [33]. The input values are the pressure data and cylinder vol-ume (with respect to crank angle). The V and dV

dh terms are shownin the following equations:

V ¼ V c þ A � r 1� cosph

180

� �þ 1

k1�

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1� k2 sin2 ph

180

� �s( )" #

ð5Þ

dVdh¼ pA

180

� �� r sin

ph180

� �þ

k2 sin2 ph180

� �2�

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1� k2 sin2 ph

180

� �q8><>:

9>=>; ð6Þ

Here, k ¼ lr and A = pD2

4 , where l = connecting rod length, r = crankradius = 0.5 � stroke, D = cylinder bore, and Vc = clearance volume.

2.8. Accuracies and uncertainties

Uncertainty in the measurements may happen due to experi-mental conditions, equipment calibration, instrument selectionand inaccuracies. Therefore, it is much needed to analyze theuncertainty of the measured values. Uncertainty of this experimentwas analyzed through a study of the instruments’ precision andaccuracy (given in Table 7) along with the repeatability of the testsusing the similar method by Fattah et al. [34]. Experiments wereperformed several times, and data were collected at least threetimes. Average values were used for graph plotting.

3. Results and discussions

3.1. Combustion characteristics

3.1.1. Analysis of in-cylinder pressureThe parameters used to compare the combustion characteristics

in this investigation were cylinder gas pressure, start of combus-tion (SOC) and heat release rate (HRR). With focus on the ‘hot’ partaround TDC (top dead center), cylinder pressure against crankangle diagram for jatropha biodiesel blend and its modified blendswith n-butanol are illustrated in Fig. 2 at 1000, 2000 and 3000 rpmkeeping the toque constant at 80 N m. It can be seen from the fig-ure that, there were no significant differences on the maximum in-cylinder pressures among the fuels. Such result actually replicatesthat, conversion of fuel energy into mechanical energy was as effi-cient for the modified blends as for the diesel fuel [32].

However, for J20 and its modified blends with additives, maxi-mum in-cylinder pressure occurred after top dead center (ATDC)within the range of 8–10.5� CA. It can be seen from Fig. 2 that, asthe speed increased, in-cylinder pressure increased accordingly.Up to 2000 rpm, J20 showed higher maximum in-cylinder pressurethan diesel. Higher and slight early maximum pressure for the J20blend can be attributed to the higher cetane number of the jatro-pha biodiesel compared to diesel [4]. However, at 3000 rpm, max-imum pressure for J20 was lower compared to diesel. Pooratomization and air–fuel mixing due to higher density, viscosityof J20 and less available time due to higher speed resulted reducedpremixed charge. Consequently peak in-cylinder pressure reduced[23]. With the addition of n-butanol into the jatropha biodiesel-diesel blend, it was observed that the peak cylinder pressuredecreased and occurred a bit late at all the observed engine speeds.At 3000 rpm, J15B5 and J10B10 produced 86.95 bar and 86.07 barof maximum in-cylinder pressures respectively at 9.4� ATDC and9.9� ATDC. Crank angles for the maximum pressures of these two

(a)

(b)

-10

0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70

-20 -10 0 10 20 30 40

Heat

rele

ase

rate

(J/

°CA)

Cylin

der p

ress

ure

(bar

)

Crank angle (°CA)

Diesel J20 J15B5 J10B10

-10

0

10

20

30

40

50

60

70

80

0

10

20

30

40

50

60

70

80

-20 -10 0 10 20 30 40

Heat

rele

ase

rate

(J/°

CA)

Cylin

der p

ress

ure

(bar

)

Crank angle (°CA)

Diesel J20 J15B5 J10B10

(c)

-20

0

20

40

60

80

100

0

10

20

30

40

50

60

70

80

90

100

-20 -10 0 10 20 30 40

Heat

rele

ase

rate

(J/°

CA)

Cylin

der p

ress

ure

(bar

)

Crank angle (°CA)

Diesel J20 J15B5 J10B10

Fig. 2. Cylinder pressure and heat release rate vs crank angle diagram for n-butanolblends at (a) 1000 rpm, (b) 2000 rpm and (c) 3000 rpm.

S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94 89

blends were almost similar at the other engine speeds. Descendingpressures with the increment of the percentage of n-butanol can beexplained by lower calorific value of the n-butanol compared todiesel and biodiesels [35].

Fig. 3 shows the in-cylinder pressure against crank angle dia-gram for jatropha biodiesel blend and its modified blends with

DEE at different engine speed. Similar to n-butanol blends, additionof DEE reduced the maximum in-cylinder pressure. At 3000 rpm,Maximum in-cylinder pressures for J15D5 and J10D10 wereobserved 86.92 and 86.10 bar respectively at 10.1� ATDC and10.4� ATDC. Slight late and lower maximum in-cylinder pressuresfor the DEE blends can be explained more clearly by combining itto the HRR analysis of the corresponding fuels.

3.1.2. Analysis of heat release rateHeat release rate analysis is one of the finest tools to get in-

depth understanding of the combustion phenomena in an engine.In-cylinder pressure characteristics of the fuels can be explainedin a better way conjoining the HRR analysis. In the present study,the engine has a pump-line-nozzle fuel injection system andadvanced start of injection (SOI) can take place if the fuel is denserand has higher bulk modulus of compressibility (and vice versa).Therefore, instead of measuring the ignition delay, in this studycombustion scenario is described with the help of SOCs (start ofcombustion). In this investigation, SOCs were acquired from theHRR against crank angle diagram. Theoretically, as the piston isnear the TDC, fuel vaporization causes a negative heat releaseand with the start of combustion, heat release momentarilybecomes positive at a point. This point is called SOC.

Heat release rate of the jatropha biodiesel blend and its modi-fied blends with n-butanol are given in the Fig. 2 at different speed.It can be seen in the figure that, at 1000 and 2000 rpm, premixedcombustion (area under the first sharp peak in the HRR diagram)of the J20 blend was quite higher than the diesel fuel, which actu-ally led to a little higher maximum pressure for this fuel [23]. How-ever, at 3000 rpm, premixed part of the combustion was lower forJ20 than diesel, which reflected slight lower in-cylinder peak pres-sure discussed earlier. At 3000 rpm, SOC of the J20 was observed at-3.7�ATDC while at 1000 and 2000 rpm SOCs were almost sameat -4�ATDC. It actually demonstrates that J20 encountered difficul-ties regarding proper atomization and consequently at higherspeed, higher crank angle revolution was needed to make thecharge combustible.

With the addition of n-butanol, it was detected that J15B5 andJ10B10 got late SOCs compared to J20 and diesel at all the observedengine speeds. SOC of J15B5 was observed on -3.9�ATDC whereasfor J10B10 it was on -3.5�ATDC on average regarding the 1000,2000 and 3000 rpm. Similarly, from Fig. 3 it can be seen that SOCsof J15D5 and J10D10 were at -3.7�ATDC and -3.1�ATDC on averageregarding the observed engine speeds respectively. Since, n-butanolhas a lower cetane number, SOC occurred late for comparativelyhigher ignition delay [36]. On the contrary, despite of higher cetanenumber of DEE, SOCs of DEE blends retarded due to its higher latentheat of evaporation which is supported by the work of Rakopoulos[13]. Such offset of SOCs were translated into comparatively lowermaximum in-cylinder pressures both for n-butanol and DEE blends.Since the SOCs were late, it was more likely that combustionoccurred in a lower temperature environment, consequently low-ered the peak pressures. However, it can be seen that, 10% blendsof the additives got more retarded SOCs compared to 5% blends ofthe additives. Since, current investigation was conducted in aturbocharged engine; fuel–air ratio was very low. Therefore, it isevident that, effect of lower temperature during the vaporizationof the fuel was not significant enough for the 5% blends of n-butanoland DEE. However, 10% n-butanol and DEE helped to create signif-icantly lower temperature during the vaporization of the fuel anddelayed the SOCs more. However, in the mixing controlled zone(area after the first sharp peak) both of the modified blends exhib-ited higher HRR than J20, which actually indicates better atomiza-tion of fuel due to lower density and viscosity of n-butanol andDEE [13].

(a)

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Diesel J20 J15D5 J10D10

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Diesel J20 J15D5 J10D10

Fig. 3. Cylinder pressure and heat release rate vs crank angle diagram for DEEblends at (a) 1000 rpm, (b) 2000 rpm and (c) 3000 rpm.

260

280

300

320

340

360

380

1000 1500 2000 2500 3000

BSFC

(g/k

W-h

)

Speed (RPM)

Diesel J20 J15B5 J10B10 J15D5 J10D10

Fig. 4. BSFC vs speed diagram for jatropha biodiesel and its modified blends at80 N m torque.

90 S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94

3.2. Engine performance characteristics

3.2.1. Brake specific fuel consumptionAs the test running condition was constant torque (80Nm) with

variable speed ranging from 1000 rpm to 3000 rpm, to assess theengine performance with different fuel blends, brake specific fuelconsumption (BSFC) was used as a convenient parameter. BSFC

implies the ratio of fuel consumption rate to brake power output.As demonstrated in the Fig. 4, it can be seen that, BSFC of all thefuels decreased as the engine speed was increased from1000 rpm to 1500 rpm. Increased atomization ratio is responsiblefor such decrement whereas increment of BSFC after 1500 rpmcan be attributed to the decreased volumetric efficiency duringthe higher speeds. At 1000 rpm it can be seen that, BSFC of dieselfuel was the highest among the blends. As the injection pump ofthe test engine was distributor type, at low speed, delivered fuelquantity decreased which affected the atomization rate as wellas the fuel–air mixing rate. Therefore, modified biodiesel blendsperformed well than diesel as they were oxygenated, even in richfuel–air mixture condition. However, J20 and its modified blendswith n-butanol showed reasonably higher BSFC than diesel onaverage. J20 showed on average 5.4% increment of BSFC than die-sel. J15B5 and J10B10 showed better BSFC results than J20. Theyshowed on average 2.3% and 3.9% decrement of BSFC than J20.J15D5 and J10D10 showed even better results than n-butanolblends. They showed 5.5% and 6.8% decrement of BSFC than J20respectively. Reason behind for the higher BSFCs of the jatrophabiodiesel blend and its modified blends than diesel is the lowerenergy content of the blends than diesel. Per unit mass heating val-ues of the blends were lower, therefore, consumption had to behigher to attain the constant 80 N m torque. However, DEE blendsshowed lower BSFCs than even diesel at lower speeds which actu-ally indicates better combustion efficiency of the blends due totheir high oxygen content, lower viscosity and density comparativeto n-butanol [4]. As the viscosity and density of J20 was higherthan its modified blends, adhesion of fuel in the cylinder walldue to higher spray penetration might happen for improper atom-ization. Therefore, these results surely indicate improvement ofatomization of the modified blends.

3.2.2. Brake specific energy consumptionBrake specific energy consumption (BSEC) is a tool for compar-

ing the performance of fuels with different heating values. It is theproduct of the BSFC and heating value of fuel. It measures howmuch energy is being consumed in one hour to develop a unitpower output. Usually, BSEC decreases with an increase in energyconsumption efficiency [37]. Fig. 5 illustrates the BSECs of thejatropha biodiesel blend and its modified blends with n-butanoland DEE at different engine speeds at constant 80 N m engine tor-que. It can be seen that, J20 gave the highest BSEC, which was onaverage 2.74% higher than diesel. However, modified blends withn-butanol and DEE showed lower BSECs compared to J20 blend.They showed on average 3.9% and 7% decrement of BSEC thanJ20 respectively. It can be seen that, increment of the percentageof n-butanol and DEE both decreased the BSECs. Such decrementcan be attributed to their higher combustion efficiency due to

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1000 1500 2000 2500 3000

BSEC

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)

Speed (RPM)

Diesel J20 J15B5 J10B10 J15D5 J10D10

Fig. 5. BSEC vs speed diagram for jatropha biodiesel and its modified blends at80 N m torque.

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NO

(PPM

)

Speed (RPM)

Diesel J20 J15B5 J10B10 J15D5 J10D10

Fig. 7. NO emission vs speed diagram for jatropha biodiesel and its modified blendsat 80 N m torque.

S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94 91

higher oxygen content and lower density and viscosity which in-turn improved atomization [38].

3.2.3. Brake thermal efficiencyBrake thermal efficiency (BTE) measures the efficiency of the

conversion of chemical energy into useful work in an engine.Dividing the useful work by the heating value of the fuel is theway to calculate BTE. Fig. 6 shows the BTEs of the modified blendsof jatropha biodiesel with n-butanol and DEE at different speedswith a constant 80 N m torque. It can be seen that, J20 exhibitedlowest BTE among the fuels on average (25.4%). On the other hand,modified blends of jatropha biodiesel J15B5 and J10B10, improvedBTE than J20 on average 2.8% and 5.3% respectively. Similarly,J15D5 and J10D10 improved the BTE on average 6.6% and 8.8% thanJ20. Reasons for the improvement of BTEs of the modified blendsare totally analogous to the reasons of improving the BSECs.

3.3. Engine emission characteristics

3.3.1. Nitrogen oxide emissionFig. 7 illustrates the NO emission for the test fuels. The mecha-

nisms which mostly take part inside the cylinder for NO formationare thermal (Zeldovich), N2O pathway, prompt (Fenimore), NNHmechanism and the fuel bound nitrogen [34]. NO formation gener-ally depends on oxygen concentration, air surplus coefficient, in-cylinder temperature and residence time [39]. In this investigation,J20 produced 8.2% higher NO emission on average than diesel.Higher NO for J20 can be attributed to higher fuel bound oxygen.Higher oxygen content of biodiesel delivers higher local peak tem-perature which results in higher NO formation. Another reasonwhich can be mentioned is the higher cetane number of jatrophabiodiesel. Due to higher cetane number, combustion advances,

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1000 1500 2000 2500 3000

BTE

(%)

Speed (RPM)

Diesel J20 J15B5 J10B10 J15D5 J10D10

Fig. 6. BTE vs speed diagram for jatropha biodiesel and its modified blends at80 N m torque.

combustion duration reduces and premixed part of the combustionincreases where NO is formed mostly [39]. However, 5% blend ofn-butanol showed even higher NO emission (5.05%) than J20.Higher oxygen content of the modified blend was the most proba-ble cause for such higher emission of NO. Nevertheless, increasedportion of n-butanol (J10B10) reduced NO emission than J20 about8.83% on average primarily due to higher latent heat of evaporationof n-butanol [24]. It is evident that, on the case of 5% blend theeffect of higher oxygen content was dominant while for 10% blend,amount of n-butanol was good enough to create lower in-cylindertemperature which has been shown by other researcher for otherfuels [17]. For higher latent heat of evaporation, in cylinder tem-perature and the premixed peak of the combustion was reduced(validated by comparative lower in-cylinder pressures). On top ofthat, for 10% n-butanol blend, the SOC was quite retarded andcombustion occurred on a comparatively lower temperatureenvironment [13]. Consequently, NO emission of J10B10 reduced.Similarly, J15D5 produced slight increased and J10D10 producedabout 12% decreased NO emission than J20. Explanation of the con-sequence is just analogous to the n-butanol case.

3.3.2. Carbon monoxide emissionIn two ways CO can be formed: through an overly lean mixture

or an overly rich mixture. Flame cannot propagate through mixturein overly lean mixtures, consequently fuel pyrolysis with partialoxidation causes CO. On the contrary, for the overly rich mixture,the fuel cannot mix with sufficient amount of air. Even if theymix, however, they do not have enough time to oxidize [40]. How-ever, generally CO forms at rich air–fuel mixture areas because ofunavailability of oxygen to completely oxidize all CO content inthe fuel. In Fig. 8, emission of CO for the test fuels at differentengine speed has been illustrated. It can be seen that, for all thefuels, up to 2000 rpm emission reduced and afterwards increased.Initially, increment of speed increased the in-cylinder temperaturewhich favored the CO oxidation, however, later on higher speedthan 2000 rpm may be reduced the time available for oxidationmechanism [39]. J20 produced quite a reduced emission comparedto diesel all over the speed range. About 27.5% decrement on aver-age was noticed for J20 than diesel. It can be attributed to higheroxygen content of biodiesel which assisted to achieve more com-plete combustion. Another explanation which can be mentionedhere is the lower carbon/hydrogen (C/H) ratio possessed by biodie-sel than diesel fuel. It was similarly assisting to produce lower COemission [34]. However, modified blends reduced the emissioneven better. J15B5, J10B10, J15D5 and J10D10 reduced the COemission than J20 about 23%, 30.7%, 11% and 20.6% respectivelybecause of more oxygen content [18]. Therefore, lower densityand viscosity of the modified blends increased the atomization effi-ciency and on top of that higher oxygen content really assistedcomplete oxidation of the fuels, hence reduced CO emission.

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CO (%

VO

L)

Speed (RPM)

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Fig. 8. CO emission vs speed diagram for jatropha biodiesel and its modified blendsat 80 N m torque.

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Smok

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Fig. 10. Smoke opacity vs speed diagram for jatropha biodiesel and its modifiedblends at 80 N m torque.

Table 8Cost analysis of the tested fuels.

Biodieselblends

CostUSD/L

CostUSD/g

AverageBSFC g/kW-h

CostUSD/kW-h

Diesel 0.66 0.000792 309.4 0.24Jatropha biodiesel 5.71 0.006632 – –n-Butanol 45.66 0.056232 – –Diethyl ether 62.7 0.088062 – –J20 1.67 0.001995 326.2 0.65J15B5 3.66 0.004388 319.2 1.40J10B10 5.64 0.006787 313.6 2.12J15D5 4.51 0.005434 308.2 1.67J10D10 7.36 0.008943 303.8 2.71

92 S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94

3.3.3. Hydrocarbon emissionComparative HC emission from the test fuels at constant 80 N m

torque with different engine speeds are shown in Fig. 9. There arenumber of reasons for the HC emission during combustion. Fueltrapping in the crevice volumes of the combustion chamber isone of the major reasons of HC emission. Locally over-lean orover-rich mixture, incomplete fuel evaporation and liquid wallfilms for excessive spray impingement are also have been men-tioned as significant factors [33]. It can be seen from the figure thatJ20 gave significantly lower HC than diesel fuel all over the enginespeed range. It gave about 28% decreased emission than diesel onaverage. Such decrement can be attributed to the higher oxygencontent of biodiesel which influenced the amount of hydrocarbonoxidation. On the contrary, J15B5 and J10B10 showed 28.4% and48% increment of HC emission than J20 on average while J15D5and J10D10 showed 32% and 52% increment. HC emission wassupposed to be reduced due to even higher oxygen content ofn-butanol and DEE. However, slip of fuel out of the cylinder espe-cially at low speed during expansion stroke might be the reason forsuch higher emission as additives like n-butanol and DEE madefuel evaporation easier [24]. Hence, IDI diesel engine inherentlycreates a homogeneous charge, consequently, addition ofn-butanol and DEE may create lean outer flame zone. This isactually the envelope of the spray boundary where because ofover-mixing the fuel is already beyond the flammability limit [4].Over-mixing is a common scenario during the combustion of thefuels with such additives as the lower density and viscosity cer-tainly affect the mixing process.

3.3.4. Smoke opacitySmoke opacity indicates the soot content on the exhaust gas

which is one of the main components of particulate matter. Hence,this parameter can be associated with fuels propensity to form par-ticulate matter during combustion. Fig. 10 illustrates the exhaust

0

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HC

(PPM

)

Speed (RPM)

Diesel J20 J15B5 J10B10 J15D5 J10D10

Fig. 9. HC emission vs speed diagram for jatropha biodiesel and its modified blendsat 80 N m torque.

smoke opacity of the test fuels. J20 gave about 6.2% decreasedsmoke opacity than diesel fuel. It can be attributed to advancedstart of combustion of J20 for higher cetane number. Hence, thecombustion started early, it allowed more time for the oxidationof soot [41]. Again, soot formation takes place generally at the ini-tial premixed combustion phase when the fuel–air equivalenceratio remains at stoichiometry. Therefore, higher oxygen contentof J20 provided oxygen in the fuel rich zones and reduced smokeopacity especially at higher speeds. J15B5 and J10B10 also followedthe trend of J20 and they gave on average 17% and 27% lowersmoke opacity respectively as they are more oxygenated. SimilarlyJ15D5 and J10D10 reduced smoke opacity about 30% and 38.5% onaverage than J20. Therefore, it is obvious that such oxygenatedblends reduced the probability of rich fuel zone formation andassisted to decrease the soot emission.

4. Economic analysis of the fuels

In Table 8, per liter cost of all the components of the blends andtested fuels are given. From the average BSFC and per gram cost ofthe respective fuels, cost for per kW-h was calculated to acquire acomparative idea of economic cost. As the prime purpose of thisstudy was to compare the engine performance-emission and com-bustion parameters of the sample fuel blends, the cost analysis pre-sented here is only a present market price scenario of the fuelblends. The analysis does not include the required subsidies forproduction and commercial distribution of the proposed samplefuel blends, which are currently provided for diesel. Thus, in thisanalysis the cost of modified fuel blends appears much higher thandiesel. Implementation of optimum production technologies ofjatropha biodiesel and the additives, analysis of global and localmarkets and subsidy from the government can surely trigger thecommercial application of these alternative fuel blends.

S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94 93

5. Conclusion

An inclusive investigation was performed to evaluate and com-pare the combustion, performance and exhaust emissions charac-teristics of jatropha biodiesel blend (J20) and its modified blendswith different percentages of n-butanol and DEE which were usedto fuel an IDI, high-speed, turbocharged diesel engine. Engine testruns were conducted by using the selected fuels at constant 80 N mtorque with variable engine speed ranging from 1000 rpm to3000 rpm. Exhaust emissions such as total unburned HC, NO, COand smoke opacity were measured for each test fuel. BSFC, BSECand BTE were measured and calculated to compare the engine per-formance characteristics. Combustion characteristics of the testfuels were discussed in terms of in-cylinder pressure diagramsand the HRR analysis at different engine speeds. The in-cylinderpressure diagrams and HRR analysis revealed some significant fea-tures of combustion mechanisms, which enlightened the perfor-mance and emissions characteristics. Thus, the followingconclusions are drawn:

� Incremental addition of n-butanol and DEE reduced the densityand viscosity of the diesel–biodiesel blend chronologically. Inspite of lower calorific value of n-butanol and DEE, modifiedblends showed insignificant difference of calorific values thandiesel fuel.� J20 produced higher in-cylinder pressure than diesel due to

higher cetane number. However, addition of n-butanol andDEE reduced the pressure in consequence of retarded SOC andhigher latent heat of evaporation of the additives. Effects ofthe additives were more prominent on the case of 10% additiveblends rather than 5% additive blends. HRR during the premixedpart of the combustion was decreased for the additives. How-ever, in the diffusion controlled zone, HRR was better for themodified blends compared to J20.� J20 showed 5.4% higher BSFC than diesel because of lower

calorific value and inferior atomization quality. However, 10%n-butanol blend showed 3.9% decreased BSFC than J20 on aver-age which was because of higher combustion efficiency due tohigher oxygen content, lower density and viscosity of n-butanol.Similarly 10% DEE blend showed 6.8% decrement of BSFC thanJ20 on average. Clearly indicating that DEE performed betterthan n-butanol. BSEC and BTE values of modified blends werealso promising indicating higher combustion efficiency.� J20 produced about 8.2% higher NO than diesel. 5% n-butanol

and DEE blends showed slight higher NO emission than J20due to higher oxygen content. However, 10% blend of both ofthem reduced NO emission due to comparatively lower temper-ature environment during combustion. On average 8.8% and12% lower NO emission was observed for 10% n-butanol andDEE blends respectively.� J20 showed about 27.5% decrement of CO emission than diesel.

J15B5 and J10B10 showed even better results by reducing COemission by 23% and 30.7% respectively than J20 due to higheroxygen content while J15D5 and J10D10 reduced 11% and20.6%.� Smoke opacity was also reduced for J20 about 6.2% than diesel.

10% n-butanol and DEE blends reduced the smoke opacity about27% and 38.5% than J20 on average which is quite better thancorresponding 5% blends of the additives. Higher oxygen con-tent of n-butanol and DEE provided sufficient oxygen even infuel rich zones for the oxidation of soot. J20 reduced unburnedHC emission by 28% than diesel fuel on average. However, dueto slip of fuel out of the combustion chamber for the evapora-tive nature of n-butanol and DEE, HC emission increased forthe modified blends.

Therefore, regarding performance and emission characteristics,10% blends of n-butanol and DEE showed higher improvementthan 5% blends. Since, the addition of n-butanol and DEE into thediesel–biodiesel blend improved the performance and emissioncharacteristics of an engine, its use can be considered as an auspi-cious way to solve intrinsic problems with the use of jatropha bio-diesel at aforementioned operating condition.

Acknowledgement

The authors would like to appreciate University of Malaya forfinancial support through High Impact Research grant titled:‘‘Clean Diesel Technology for Military and Civilian Transport Vehi-cles’’ having grant number UM.C/HIR/MOHE/ENG/07.

References

[1] Ong HC, Mahlia TMI, Masjuki HH, Norhasyima RS. Comparison of palm oil,Jatropha curcas and Calophyllum inophyllum for biodiesel: a review. RenewSustain Energy Rev 2011;15:3501–15.

[2] Adnan H. Palm oil biodiesel programme to cover all of Malaysia by July. Thestar online; 2014.

[3] Mofijur M, Masjuki HH, Kalam MA, Hazrat MA, Liaquat AM, Shahabuddin M,et al. Prospects of biodiesel from Jatropha in Malaysia. Renew Sustain EnergyRev 2012;16:5007–20.

[4] Imtenan S, Masjuki HH, Varman M, Kalam MA, Arbab MI, Sajjad H, et al. Impactof oxygenated additives to palm and jatropha biodiesel blends in the context ofperformance and emissions characteristics of a light-duty diesel engine.Energy Convers Manage 2014;83:149–58.

[5] Lane J. FRIM completes Malaysian jatropha pilot, aims for scale. BiofuelsDigest; 2012.

[6] Huang J, Wang Y, Qin J-B, Roskilly AP. Comparative study of performance andemissions of a diesel engine using Chinese pistache and jatropha biodiesel.Fuel Process Technol 2010;91:1761–7.

[7] Sundaresan M, Chandrasekaran S, Porai PT. Analysis of combustion,performance and emission characteristics of blends of methyl esters ofJatropha Oil. SAE Technical Paper 2007-32-0066; 2007.

[8] Chauhan BS, Kumar N, Du Jun Y, Lee KB. Performance and emission study ofpreheated Jatropha oil on medium capacity diesel engine. Energy2010;35:2484–92.

[9] Manieniyan V, Sivaprakasam S. Investigation of diesel engine using bio-diesel(methyl ester of Jatropha oil) for various injection timing and injectionpressure. SAE paper 01-1577; 2008.

[10] Sahoo P, Das L, Babu M, Arora P, Singh V, Kumar N, et al. Comparativeevaluation of performance and emission characteristics of jatropha, karanjaand polanga based biodiesel as fuel in a tractor engine. Fuel2009;88:1698–707.

[11] Sharon H, Karuppasamy K, Soban Kumar D, Sundaresan A. A test on DI dieselengine fueled with methyl esters of used palm oil. Renew Energy2012;47:160–6.

[12] Arbab MI, Masjuki HH, Varman M, Kalam MA, Imtenan S, Sajjad H.Experimental investigation of optimum blend ratio of jatropha, palm andcoconut based biodiesel to improve fuel properties, engine performance andemission characteristics SAE Technical Paper 2013-01-2675; 2013.

[13] Rakopoulos DC. Combustion and emissions of cottonseed oil and its bio-dieselin blends with either n-butanol or diethyl ether in HSDI diesel engine. Fuel2013;105:603–13.

[14] Hansen AC, Zhang Q, Lyne PWL. Ethanol–diesel fuel blends––a review.Bioresour Technol 2005;96:277–85.

[15] Hansen AC, Kyritsis DC. Characteristics of biofuels and renewable fuelstandards. Biomass to biofuels: strategies for global industries; 2010. p. 1–26.

[16] Yao M, Wang H, Zheng Z, Yue Y. Experimental study of n-butanol additive andmulti-injection on HD diesel engine performance and emissions. Fuel2010;89:2191–201.

[17] Altun Se, Öner C, Yasar F, Adin H. Effect of n-butanol blending with a blend ofdiesel and biodiesel on performance and exhaust emissions of a diesel engine.Ind Eng Chem Res 2011;50:9425–30.

[18] Lebedevas S, Lebedeva G, Sendzikiene E, Makareviciene V. Investigation of theperformance and emission characteristics of biodiesel fuel containing butanolunder the conditions of diesel engine operation. Energy Fuels 2010;24:4503–9.

[19] Mehta RN, Chakraborty M, Mahanta P, Parikh PA. Evaluation of fuel propertiesof butanol�biodiesel�diesel blends and their impact on engine performanceand emissions. Ind Eng Chem Res 2010;49:7660–5.

[20] Rakopoulos DC, Rakopoulos CD, Giakoumis EG, Dimaratos AM. Characteristicsof performance and emissions in high-speed direct injection diesel enginefueled with diethyl ether/diesel fuel blends. Energy 2012;43:214–24.

[21] Rakopoulos C, Antonopoulos K, Rakopoulos D. Experimental heat releaseanalysis and emissions of a HSDI diesel engine fueled with ethanol–diesel fuelblends. Energy 2007;32:1791–808.

94 S. Imtenan et al. / Energy Conversion and Management 94 (2015) 84–94

[22] Babu PR, Rao KP, Rao BA, Srivastava S, Beohar H, Gupta B., et al. The role ofoxygenated fuel additive (DEE) along with mahuva methyl ester to estimateperformance and emission analysis of DI-diesel engine.

[23] Sivalakshmi S, Balusamy T. Effect of biodiesel and its blends with diethyl etheron the combustion, performance and emissions from a diesel engine. Fuel2013;106:106–10.

[24] Qi DH, Chen H, Geng LM, Bian YZ. Effect of diethyl ether and ethanol additiveson the combustion and emission characteristics of biodiesel-diesel blendedfuel engine. Renew Energy 2011;36:1252–8.

[25] Rizwanul Fattah IM, Masjuki HH, Kalam MA, Wakil MA, Rashedul HK, AbedinMJ. Performance and emission characteristics of a CI engine fueled with Cocosnucifera and Jatropha curcas B20 blends accompanying antioxidants. Ind CropsProd 2014;57:132–40.

[26] Atabani AE, Mahlia TMI, Masjuki HH, Badruddin IA, Yussof HW, Chong WT,et al. A comparative evaluation of physical and chemical properties ofbiodiesel synthesized from edible and non-edible oils and study on theeffect of biodiesel blending. Energy 2013;58:296–304.

[27] Kivevele TT, Mbarawa MM, Bereczky A, Laza T, Madarasz J. Impact ofantioxidant additives on the oxidation stability of biodiesel produced fromCroton Megalocarpus oil. Fuel Process Technol 2011;92:1244–8.

[28] Sanjid A, Masjuki HH, Kalam MA, Rahman SMA, Abedin MJ, Palash SM.Production of palm and jatropha based biodiesel and investigation of palm-jatropha combined blend properties, performance, exhaust emission and noisein an unmodified diesel engine. J Clean Prod.

[29] Agarwal AK, Das L. Biodiesel development and characterization for use as afuel in compression ignition engines. J Eng Gas Turbines Power2001;123:440–7.

[30] Chotwichien A, Luengnaruemitchai A, Jai-In S. Utilization of palm oil alkylesters as an additive in ethanol–diesel and butanol–diesel blends. Fuel2009;88:1618–24.

[31] Canakci M, Ozsezen AN, Turkcan A. Combustion analysis of preheated crudesunflower oil in an IDI diesel engine. Biomass Bioenergy 2009;33:760–7.

[32] Ozsezen AN, Canakci M, Sayin C. Effects of biodiesel from used frying palm oilon the performance, injection, and combustion characteristics of an indirectinjection diesel engine. Energy Fuels 2008;22:1297–305.

[33] Heywood JB. Internal combustion engine fundamentals. Singapore: McGraw-Hill; 1988.

[34] Rizwanul Fattah IM, Kalam MA, Masjuki HH, Wakil MA. Biodiesel production,characterization, engine performance, and emission characteristics ofMalaysian Alexandrian laurel oil. RSC Adv 2014;4:17787–96.

[35] Lujaji F, Kristóf L, Bereczky A, Mbarawa M. Experimental investigation of fuelproperties, engine performance, combustion and emissions of blendscontaining croton oil, butanol, and diesel on a CI engine. Fuel 2011;90:505–10.

[36] Rakopoulos DC, Rakopoulos CD, Papagiannakis RG, Kyritsis DC. Combustionheat release analysis of ethanol or n-butanol diesel fuel blends in heavy-dutyDI diesel engine. Fuel 2011;90:1855–67.

[37] Teoh YH, Masjuki HH, Kalam MA, Amalina MA, How HG. Impact of wastecooking oil biodiesel on performance, exhaust emission and combustioncharacteristics in a light-duty diesel engine. SAE Technical Paper. 2013-01-2679; 2013.

[38] Rakopoulos D, Rakopoulos C, Giakoumis E, Dimaratos A, Kyritsis D. Effects ofbutanol–diesel fuel blends on the performance and emissions of a high-speedDI diesel engine. Energy Convers Manage 2010;51:1989–97.

[39] Imtenan S, Varman M, Masjuki HH, Kalam MA, Sajjad H, Arbab MI, et al. Impactof low temperature combustion attaining strategies on diesel engineemissions for diesel and biodiesels: a review. Energy Convers Manage2014;80:329–56.

[40] Turns SR. An introduction to combustion: concepts and applications. 2nded. Singapore: McGraw-Hill; 2000.

[41] Ozsezen AN, Canakci M, Sayin C. Effects of biodiesel from used frying palm oilon the exhaust emissions of an indirect injection (IDI) diesel engine. EnergyFuels 2008;22:2796–804.