Prosiding Seminar Nasional Daur Bahan Bakar 2009Serpong, I3 Oktober 2009

ISSN 1693-4687

Analytical Study for Palm-Jatropha BiodieselSpray Characteristics

L. Shalahuddin, R. FajarBalai Tennodinamika Motor & Propulsi (BTMP) - BPPT

email: l_shalahuddin@yahoo.com

Abstract - ANALYTICAL STUDY FOR PALM-JATROPHA

BIODIESEL SPRAY CHARACTERISTICS. This paper presentsanalytical evaluation of biodiesel blends with diesel filels usingindirect injection spray injector. The biodieselunder study is a60:40 blend of used frying oil (from palm) and jatropha oil. Thereason for selecting this composition is the best trade off forobtaining oxidation stability and saturation properties. Usedfrying oil is selected for economical reason. The physico­chemical properties, i.e. density, suiface tension, and viscosity,are evaluated for B100, B5, B10, B20, and B30. Such data are

required for input parameters of a spray modelling which isunder preparation. The above properties can be used to predictthe spray characteristics under typical injection pressure andair density. In this study, only the Sauter mean diameter (SMD)is evaluted using semi-empirical formulae from other study. Itis found that the SMD for the above biodiesel blend is 24.6 f1l1J,compared with 20.4 flm for pure diesel filel. The SMD for othercompositions are also evaluated up to B30; in which it is foundthat the SMD is 21.6 flm. The effect of injection pressure is alsostudied.

Keywords: Palm, Jatropha, Biodiesel, Spray, Sauter meandiameter.

Abstraks - STUD! ANALITIK TERHADAPKARAKTERJSTIK SPRA Y BIOD!ESEL SAWIT-JARAK.Pada Makalah ini disampaikan anatisa terhadap karaktenstikcampuran biodiesel-minyak solar pada nosel injeksi taklangsung. Campuran yang sedang diteliti adalah minyakjelantah dari sawit dan minyak jarak dengan komposisi 60:40.Alasan pemilihan komposisi tersebut adalah berdasarkankompromi yang terbaik antara stabilitas oksidasi dan sifatjenuhnya. Minyak jelantah dipilih karena alasan ekonomis.Sifat-sifat fisika kimia, yaitu densitas, tegangan permukaan, danviskositas, dihitung untuk bahan bakar 8 I00 (minyak solarmurni), 85, 810, 820, dan 830. Data tersebut diperlukansebagai input untuk modeling spray yang tengah dalampersiapan. Sifat-sifat diatas dapat digunakan untuk memprediksikarakteristik spray pada kondisi tekanan injeksi dan densitasudata yang lazim terjadi pada mesin. Pada penelitian ini hanyaparameter diameter rata-rata Sauter (SMD) yang dihitungmenggunakan rumus semi empns dari studi lain.Hasilnyamenunjukkan bahwa SMD untuk campuran biodiesel diatasadalah 24.6 f1l1J,dibandingkan dengan 20.4 f1l1Juntuk minyaksolar murni. SMD untuk komposisi lain juga dihitung hinggaB30, dimana SMDnya diperoleh sebesar 21.6 f1l1J.Efek daritekanan injeksi juga dipelajari.

Kata Kunci: Sawit, Jarak, 8iodiesel, spray, diameter rata-rataSauter

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I. INTRODUCTION

Biodiesel is an environment friendly liquid fuel similarto petro-diesel in combustion properties. Increasingenvironmental concern, diminishing petroleum reservesand as a way to agriculture-based economy, are thedriving forces to promote biodiesel as an alternaterenewable transportation fuel. Biodiesel derived fromvegetable oil and animal fats is being used in othercountries to reduce air pollution, to reduce dependence onfossil fuel, whose resources are limited and localized tosome specific regions.

Indonesia has allowed biodesel blend as much as 10%

to be commercially purchased in public gas stations,especially in the Jakarta area.

In this study biodiesel blend of used frying oil (frompalm oil) and jatropha is investigated. The fonner hasbeen throughly studied due to its abundant availability,low cost, and good characteristics (oxidation stability andhigh cetane number) after treatment. Whereas the latter isused since it is non-edible oil and has better flow

properties than those of palm oil at low temperatures, i.e.pour point, cloud point, and cold flow plugging point.However, since the oxidation stability of jatropha is lowerthan palm oil, its fraction in the blend should be limited.Sarin [1] has showed that the jatropha's fraction in themixture with palm oil is limited to 40% maximum inorder to keep the oxidation stability within Internationalstandards (e.g. European standard requires minimum ofsix hours).

There has been significant work on biodiesel stability[2]. As biodiesel chemically is an ester molecule there isevery possibility that in the presence of air or oxygen itwill be hydrolyzed to alcohol and acid. Presence ofalcohol will lead to reduction in 'flash point and presenceof acid will increase total acid number. All these make

methyl ester relatively unstable on storage and causedamage to engine parts. This is why the oxidationstability is an important criterion for biodiesel. Stabilityof biodiesel is inferior compared to diesel fuel andtherefore doping of biodiesel in diesel fuel will affect thestability of fuel significantly [3]. The poor stability ofbiodiesel is also because of the double bonds in the fattyacids, which may lead to gum formation. In either of thecases the product will become off spec. Therefore, it wasconsidered to include a limit for oxidation stability in the

(Eq. 2)

Prosiding Seminar Nasional Daur Bahan Bakar 2009Serpong, 13 Oktober 2009

existing quality standard for biodiesel. Almost in allbiodiesel fuel significant amounts of esters of oleic,linoleic or linolenic acids are present and the trend ofincreasing stability was linolenic < linoleic < oleic. Theseesters undergo auto-oxidation with different ratesdepending upon the number and position of the doublebonds and results in formation of a series of by-products,like acids, esters, aldehydes, ketones, lactones, etc.

II. THEORY

The main objective of this study is to perform ananalytical comparison of atomisation characteristics ofvarious blends of biodiesel at 80°C, using a directinjection with the following blends: as the basis is 40%­60% jatropha-palm oil mix, and this is designated asB 100. This is to be blended with diesel fuel at 5, 10, 20,and 30 % v/v fraction, designated as B5, BIO, B20, andB30, respectively.

Physical properties of fatty acid methyl esther (FAME)at 80°C are given at Table 1. In this Table, the propertiesare broken down according to the composition of the acidconstituents.

TABLE 1. PHYSICAL PROPERTIES OF FAMEAT 8(f'C [5J

D (!!/mI)v (cSt)Y (mN/m)

caprylic

C8/00.8240.7221.77

canric

clOIO0.8230.9722.83

lauric

cl2/00.822I.3123.61

myristic

cl4/00.8211.6424.19

palmitic

cl6/00.822.0325.2

pahnitoleic

cl6/1

stearic

cl8/00.8212.5325.82

oleic

cl8/10.8382.1927.13

linoleic

cl8/20.8451.9227.49

linolenic

cl8/30.861.8128.23

amchidic

c2010- --

behenicc22/0- --

Pt111'.1r.

,,77/1o R4,77n ,Q

The kinematic viscosity of mixtures, ?mix, is predictedusing equation:

In(umLJ = 2:1'; lnui (Eq.l)

Where Y; is the mass fraction of the ith liquid orconstituent.

The surface tension of mixtures, ?mix, is calculated as:

Ym"~(~):Y;'" J'whereas the density of the mixtures, ?mix, are calculatedas:

(Eq. 3)

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ISSN 1693-4687

The droplet size correlation is derived from the aboveparameters, expressed in term of the Sauter meandiameter, Ds, and given as:

Ds = 6156uo.385ro.737 pO.737 Pa 0.06p-o.54 (Eq.4)

Eq. (4) is valid within the following ranges: 0.81 x 10'6 <?mix < 8.6 X 10'6 m2/s, 2004 < ?mix < 27.5 mN/m, 732 <?mix < 847 kg/m3, and 78 < p < 200 bar.

Droplet Spray ModelOne of the basic characteristics of an injection is the

distribution of drop size. For an atomizer, the dropletdiameter distribution is closely related to the nozzle state.A spray model is being prepared which uses a two­parameter Rosin-Rammler distribution, characterized bythe most probable droplet size and a spread parameter.The most probable droplet size, is obtained from the

Sauter mean diameter, Ds' In order to run the model,

therefore, reasonable prediction of the Sauter meandiameter is required. From the combustion point of view,smaller mean droplet diameter is preferred, since thiswould mean faster rate of evaporation, and hence, shorterignition delay.

III. RESULTS

Mass fraction of typical Indonesian palm oil andjatropha oil is given at second and sixth column,respectively, of Table 2. If ones intend to implement thestudy from Indonesian resources, this is more indigenousdata than those found from literatures [1] & [5],. Fromthese, predicted physical properties were calculated usingequations (1-3).

The Sauter mean diameters are then calculated from

Eq. (4). Two different setting of injection pressures arecalculated, 200 and 150 bars, as shown in Table 3 andTable 4.

IV. DISCUSSION

The last row of Table 3 shows the Sauter mean

diameter of various blends of the biodiesel under study.As expected, the droplet size of the biodiesel is largerthan those of diesel fuel. This implies that the atomisationcharacteristics of the biodiesel are not as good as dieselfuel. However, the magnitude of the differences is lessthan 4% for BI0; and the differences are certainlynegligible for B5. The combustion characteristics of thefuel is not only determined by the performance ofatomisation, but also by the cetane number and oxygencontent whereas the biodiesel blends have higher valuesthan that that of diesel fuel.

The importance of sufficiently high injection pressureis apparent from comparing Table 3 and Table 4. In Table4, the injection pressure is lowered from 200 bar to 150bar (25% lower), which result in larger droplet diameter,about 20% larger.

Prosiding Seminar Nasional Daur Bahan Bakar 2009Serpong, 13Oktober 2009

TABLE 4. PHYSICAL PROPERTIES OF FAME AT 8(f' C [5]

ISSN 1693-4687

Biodiesel from used frying oilJathropa

yp (g/m!)v (cSt)y (mN/m)yp (g/ml)v (cSt)y (mN/m)

caDrvlic

0.960.00791-0.003150.0207370000

capric

00000000

lauric

7.670.0630470.0207110.1690710000

myristic

3.370.0276680.0166710.0747380000

Dalmitic

59.730.4897860.422911.33826722.870.1875340.1619280.512408

palmitoleic

00 000 0

stearic

1.180.0096880.0109530.0265990000

oleic

24.140.2022930.1892340.55093445.920.384810.3599681.048007

linoleic

2.950.0249280.0192440.06754831.210.2637250.2035910.71464

linolenic

00000000

arachidic

00 000 0

behenic

00 000 0

erucic

00000000

0.676569 2.247894Aggregated

TABLE 3. SA UTER MEAN DIAMETER FOR INJECTION PRESSURE OF 200 BAR

0.725486 2.275056

Property dieselusedjathropa810085BI0820B30frying (Dal~)?(m"/s)

1.400E-61.967E-62.066E-62.006E-61.425E-61.451 E-61.504 E-61.560E6?(N/m)

0.02520.02550.02680.02600.02530.02530.02540.0255? (kg/m3)

801825836830802804807810? (kg/m3)

8.28.28.28.28.28.28.28.2p(bar)

200200200200200200200200D,(pm)

20.4124.0025.5824.6320.6020.792l.l921.59

TABLE 2. SAUTER MEAN DIAMETER OF VARIOUS BIODIESEL BLENDS (INJECTION PRESSURE OF 150 BAR & OTHER PARAMETERS BEING KEPTCONSTANT)

Property dieselusedjathropa8100B5BI0820B30frying (Dalm)?(III Is)

I .400 E-61.967E-62.066E-62.006E-61.425E-61.451 E-61.504E-61.560E6?(N/III)

0.02520.02550.02680.02600.02530.02530.02540.0255? (kg/1II3)

801825836830802804807810? (kg/1II3)

8.28.28.28.28.28.28.28.2p(bar)

150150150150150150150150D,(Jult)

23.8428.0429.8828.7624.0624.2924.7525.22

V. CONCLUSION

Prediction of Sauter mean diameter of various blends

of biodisel have been obtained using semi-empiricalformulae .. The results seem reasonable. The effect of

injection pressure is also logical. Thus, important data forinput for spray modelling are thus ready.

ACKNOWLEDGEMENT

The authors would like to thank to S. Yubaidah for

providing the data for Indonesian biodiesels, and toHimawan for preliminary steps of spray modelling.

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REFERENCES:

[1] RAKESH SARIN *, MEETA SHARMA, S. SINHARAY,R.K. MALHOTRA, "Jatropha-Palm biodiesel blends: Anoptimum mixfodsia", Fuel 86 1365-1371,2007.

[2] Proceedings of annual biodiesel technical workshop; 12­13, Chicago, January 2005.

[3] DUNN RO, KNOTHE G., "Oxidative stability of biodieselin blends with jet filel by analysis of oil stability index", JAm Oil Chern Soc,;80: I047-8,2003.

[4] POGOREYC, et aI., "Diesel and Biodiesel Fuel SpraySimulations", Energy & Fuels, 22, pp. 1266-1274,2008.

[5] EJIM, et aI., "Analytical study for atomization of bodieselsand their blends in a typical injector: Suiface tension andviscosity effect", Fuel, 86, pp. 1534-1544, 2006.