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Keywords:

BiodieselBioethanol

erimbioarchsitiore eutio

sured. An increasing of brake specic fuel consumption has been observed, especially at lower engines

NOx emissions slightly increase, especially at partial and high loads, meanwhile HC and smoke emissions

for thhe mosssil fuesel, al

for transport [3].The main advantages of using biodiesel for CI engines are as

follows [2,4]: biodiesel is non-toxic; biodiesel degrades four timesfaster than diesel; pure biodiesel degrades 8588% in water; thehigher ash point makes the storage safer; provides a domestic,renewable energy supply; biodiesel does not produce greenhouseeffects, because the balance between the amount of CO2 emissionsand the amount of CO2 absorbed by the plants producing vegetable

feedstocks: sugar, starch or cellulose. Even if it is conceived mainlyas an alternative fuel for spark ignition engines, it also has applica-tions for CI engines. The main methods of using ethanol in CI en-gines are described in [1]: the alcoholdiesel fuel blend; alcoholfumigation; alcoholdiesel fuel emulsion with emulsier; and dualinjection.

The use of some bioethanoldiesel blends in CI engines isrestricted mainly by the limited miscibility at low temperatures[10], as well as the necessity of some modications in the enginefuel system, because the lower heating value drops which needsan increase of fuel dose per engine cycle. Density and viscosity of

* Corresponding author. Tel.: +40 (0) 264 401 674; fax: +40 (0) 264 415 490.

Fuel 89 (2010) 38273832

Contents lists availab

ue

.eE-mail address: istvan.barabas@arma.utcluj.ro (I. Barabs).biodiesel is produced from vegetable oils (fresh or used) and alsofrom animal fat.

The use of biodiesel for partial or total diesel fuel substitutiondoes not constitute a novelty, because the vegetable oils have beenproposed as compression ignition (CI) engines fuel since 1895 [2].Today, the minimal quality conditions of biodiesel are regulated bythe European Standard for Biodiesel EN 14214.

The sequential introducing of biofuels for internal combustionengines is regulated by the 2003/30/EC Directive, which providesthe step by step implementation of biofuels in the classic ones

more expensive due to less production of vegetable oil. The useof biodiesel can be considered as an alternative for CI engines,but some of its properties, as density and viscosity, are higher thanthose of classic diesel fuel. These properties can be ameliorated byadding bioethanol, which on one hand allows the biofuels level-in-crease in the whole blend, and on the other hand brings the men-tioned properties in standard diesel fuel prescribed limits.

The biodiesel density at 15 C is between 860 and 894 kg/m3

[68]. The commercial biodiesel viscosity at 40 C is between 3.3and 5.2 mm2/s [79]. Bioethanol can be produced from different1. Introduction

In the last decades many methodsICE gases have been studied. One of tto add oxygenated components to foated organic compounds are biodie0016-2361/$ - see front matter 2010 Elsevier Ltd. Adoi:10.1016/j.fuel.2010.07.011decrease in all engines load cycles. 2010 Elsevier Ltd. All rights reserved.

e pollution reduction oft important methods isl [1]. The main oxygen-cohols and ethers. The

oil is equal; biodiesel can be used directly in compression ignitionengines with no substantial modications of the engine.

Nevertheless, biodiesel use has also a number of disadvantages[2,5]: light decrease in fuel economy on energy basics (about 10%for pure biodiesel); density is higher than that of diesel fuel in coldweather, but may need to use blends in sub-freezing conditions;PerformanceEmission loads, with maximum 32.4%, reducing engine brake thermal efciency with maximum 21.7%. CO emis-

sions decrease, especially at high loads with maximum 59%, on the basis of CO2 increased emissions.Performance and emission characteristicwith dieselbiodieselbioethanol blends

Istvn Barabs *, Adrian Todorut, Doru BaldeanDepartment of Automobiles and Agricultural Machinery, Technical University of Cluj-Na

a r t i c l e i n f o

Article history:Received 18 July 2009Received in revised form 10 July 2010Accepted 12 July 2010Available online 23 July 2010

a b s t r a c t

The paper presents the expengine fueled with dieselmain properties of the resesel fuel (chemical compoEngines performances wethermal efciency. For poll

F

journal homepage: wwwll rights reserved.f an CI engine fueled

, Muncii 103-105, 400641 Cluj-Napoca, Romania

ental results obtained concerning performances and pollution of a dieseldieselethanol blends compared with diesel fuel in laboratory tests. Theed fuels are presented within this paper, in comparison with classical die-n, density, kinematic viscosity, cold lter plugging point, ash point).valuated by determining the brake specic fuel consumption and braken evaluation the emissions of CO, CO2, NOx, HC and smoke have been mea-

le at ScienceDirect

l

l sevier .com/locate / fuel

l 89 (2010) 382738323828 I. Barabs et al. / Fuebioethanoldiesel fuel blends is lower than that of classic dieselfuel, which reduces the fuel lubricating capacity.

Density is a fuel-property which has direct effects on the engineperformance characteristics [11]. Many fuel properties such as ce-tane number and heating value are related to the density. Fuel den-sity inuences the efciency of fuel atomization and combustioncharacteristics [11,12]. Because diesel fuel injection systems meterthe fuel by volume, the change of the fuel density will inuence theengine output power due to a different mass injected fuel. The eth-anol density is lower than diesel fuel density, but biodiesel densityis higher.

Viscosity is one of the most important fuel properties, because itaffects the operating conditions of injection systems, especially atlow temperatures when fuel uidity is reduced. Also, viscosity af-fects fuel lubricating capacity [4], ensuring fuel pumps and injec-tors lubrication [1,13].

In the case of dieselbiodieselethanol blends it has an emulsi-er role [1416], some blends being stable even at negative tem-peratures [17]. The heating value is comparable with the one ofdiesel fuel, having a higher lubricating capacity than the previous,facilitating the increase of biofuels content in the whole blend[18,19].

The most important objectives of this study consist in evaluat-ing the main properties of the studied dieselbiodieselethanolblends and comparing them with those of classical diesel fuel.The performance and emissions at different engines loads havebeen studied through fuel blends tests on ICE, and some conclu-sions have resulted concerning the use of dieselbiodieselethanolblends for diesel engines and the dual-fuel operating systempossibility.

Fig. 1. Stand diagram: (1) diesel fuel tank; (2) biodiesel tank; (3, 4, 6, 7) valves; (5) rebetween diesel/blends; (DA diesel access; BA blends access; DR diesel return; anpressure transducer (plo); (13) lubricating oil temperature transducer (tlo); (14) cardanhydraulic brake; (18) electronic control unit (ECU); (19) electronic data processing unit ((23) input air temperature transducer (t0); (24) exhaust gas static pressure transductemperature transducer (teg); and E.G. exhaust gases.2. Material and methods

The experimental research concerning the ICE performancesand pollution have been directed toward three fuel blends ofdieselbiodieselethanol, for which diesel fuel has been used asreference. The fuel blends have been chosen taking into consider-ation the previous research recommendations from the specializedliterature [1417], and on the basis of some researches of a grantResearches aiming partial substitution of diesel fuels for dieselengine with dieselbiodieselethanol mixtures (RomanianNational University Research Council, Research Programme ID1098, No. 88/01.10.2007), the main criteria being that their densityand viscosity should be very close to that of classical diesel fuel,having a corresponding lubricating capacity at the same time. Inorder to prepare the blends the following components were used:commercial diesel fuel, biodiesel obtained from rape oil andethanol 99.3%.

cipient to measure the fuel consumption; (8) diesel engine; (9) commutable valved BR blends return); (10) injection pump; (11) feeder pump; (12) lubricating oiltransmission; (15) brake torque transducer (M); (16) rotation transducer (n); (17)EDPU); (20) cooling agent temperature transducer (tc); (21) fuel lter; (22) injector;er (pegs); (25) exhaust gas dynamic pressure transducer (pegd); (26) exhaust gas

Table 1Main engine specications.

Number of cylinders 4 in lineBore 110 mmStroke 130 mmCompression ratio 17:1Rated power 46.5 kW at 1800 rpmRated torque 285 N m at 1200 rpmDisplacement volume 4.76 lNozzle opening pressure 175 5 barSize of nozzle 4 0.275 mmInjection system Direct, mechanical

The experimental researches concerning the performances andthe determination of pollutant emissions were developed on thetest bench presented in Fig. 1. The bench is equipped with a D-2402.000 type CI engine, having the main characteristics presentedin Table 1, hydraulic dynamometer and a data acquisition systemfor recording the operating parameters. For pollutant emissionsevaluation the Bosch BEA 350 type gas analyzer has been used.

Diesel engines of the given type were designed in the 1990s,redesigned in 2002 and were produced and exported until 2006.These engine have been widely used up to the present day in agri-cultural machinery in Romania. On these grounds, the results ofthe research performed by the authors are used for preliminary

is very close to that of diesel, and the differences get smaller with

ping and storage classication of fuels and the precautions thatshould be used in handling and transporting the fuel. As a result,the storage, handling and transportation of dieselbiodieselethanol mixtures must be managed in a special and proper way,in order to avoid an explosion.

Concerning the cold lter plugging point (CFPP) it was observedthat in the case of 5% ethanol blends it decreases, but it gets higherin the case of D80B10E10 blend because of the limited ethanol mis-cibility, which restricts its use at low temperatures.

The cetane number and cetane index is also in proportion todensity value. The cetane number of the dieselbiodieselethanolblend is decreasing with the bioethanol content, because ethanol

I. Barabs et al. / Fuel 89 (2010) 38273832 3829temperature increase. Because the ethanol vaporizing temperatureis quite small (approximately 78 C), it will be in vapor state at theoperating injector temperature. The compensation of biodieselhigher density and viscosity levels is important especially at lowengine operating temperatures.

At the same time, a signicant decrease in the blends ashpoint can be observed (1217 C). The ash point of a dieselbiodieselethanol mixture is mainly dominated by ethanol. All ofthe blends containing ethanol were highly ammable with a ashpoint temperature that was below the ambient temperature, whichconstitutes a major disadvantage, especially concerning theirtransportation, depositing and distribution, which affects the ship-

Table 2The main properties of analyzed fuels.

Properties Unit Method Diesel

Diesel content % vol. Preparated 100Biodiesel content % vol. Preparated 0Ethanol content % vol. Preparated 0Oxygenate content % vol. Calculated 0Carbonate content % wt. Calculated 85.21Hydrogen content % wt. Calculated 14.79Density at 15 C kg/m3 EN ISO 12185 843Kinematic viscosity at 40 C mm2/s ASTM D7042-04 2.485Flash point C EN ISO 2719 61CFPP C EN 116 9evaluation of the expected efciency of the replacement of fossildiesel fuel with dieselbiodieselethanol mixtures for the abovementioned diesel engine and other similar types of diesel engines.

The load characteristics have been drawn at the 1400 rpm en-gine speed, this one being between the maximum torque speedand the maximum power speed. Before each test the fuel lterswere replaced and the engine was brought to the nominal operat-ing temperature. For evaluation the obtained results werecompared with those obtained in the case of diesel fuel. Theresults-evaluation has been made for three engine loadingdomains: small loads (040%), medium loads (4080%) and highloads (>80%).

3. Results and discussion

3.1. Fuel properties

The main characteristics of the studied fuels are presented inTable 2.

The fuel blends density variation with temperature is pre-sented in Fig. 2. It can be seen that the dieselbiodieselethanolblends have a very close density to diesel fuel on the whole consid-ered temperature domain.

The constituents viscosity and the blends viscosity variationare presented in Fig. 3. There may be seen that the blends viscosityCetane number [20,21] ASTM D613 5155Cetane index [14] ASTM D976 47.64itself has very low cetane number. The lower the cetane numberis, the poorer the ignition property will be. Cetane number alsohas an effect on the engine start up, combustion control, and en-gine performance [14]. However, biodiesel, due to its high cetanenumber value, could improve this property, so the blend can fulllthe cetane number requirement for diesel, 51 CN [20,21].

3.2. Engine performances

3.2.1. Break specic fuel consumptionThe obtained results in the case of specic fuel consumption re-

lated to engine load are presented in Fig. 4. The brake specic con-sumption is greater at smaller loads, but it decreases at mediumand higher loads. The brake specic fuel consumption is greaterfor the blends, because their heating value is smaller. The sequenceis D100, D85B10E5, D80B10E10 and D70B25E5, being the same atall engine loads, maintaining the increasing sequence of biofuelscontent. The increase is higher at small loads (32.4% in the caseof D70B25E5); at medium and high loads the determined valuesfor blends are comparable with the values for diesel, being be-tween 6.2% and 15.8%.

3.2.2. Brake thermal efciencyThe engine efciency variation with load for the studied fuels is

shown in Fig. 5. As it was expected, the engine efciency decreasesfor fuel blends, the tendencies being similar with those of brakespecic fuel consumption. The engine efciency decrease is be-tween 0.4% and 21.7%.

3.3. Pollutant emissions

3.3.1. Carbon monoxideThe carbon monoxide emissions differ with the fuel and engine

load (Fig. 6). Thus, at small and medium loads, the greatest emis-sions have been measured for diesel fuel and the lowest forD80B10E10 fuel blend. As it was expected, at high loads CO emis-sion increases, being with approximately 50% lower in the case ofstudied fuel blends. This fact is explained in [14] through high level

Biodiesel Ethanol D85B10E5 D70B25E5 D80B10E10

0 0 85 70 80100 0 10 25 100 100 5 5 1010.79 34.76 2.82 4.43 4.5576.97 52.14 82.73 81.50 81.0812.24 13.13 14.45 14.07 14.37887.5 794.85 845 852 8435.540 1.070 2.421 2.756 2.275126 13 14 18 1514 17 17 6

5556 8 51 52 5155.4 58 47.7 48.66 46.85

Fig. 4. Variation of brake specic fuel consumption of different fuels.

Fig. 2. Density variation of analyzed fuels with temperature.

Fig. 3. Viscosity variation with temperature.

3830 I. Barabs et al. / Fuel 89 (2010) 38273832of oxygen content in biodiesel and ethanol, which sustain the oxi-dation process during the exhaust process as well. The experimen-tal results have shown, that in the case of high engine loads, thelowest CO emission is for the D85B10E5 fuel blend (0.234% vol.),which compared with the one for diesel fuel (0.575% vol.) repre-sents a reduction with 59%. The experimentally obtained resultsfor CO emissions are comparable with those presented in [14].

3.3.2. Carbon dioxideThe CO2 emissions for the studied fuel blends are superior to the

measured values in the case of an engine running with diesel fuelin all three load operating conditions taken into account in this pa-per (Fig. 7). The increase of CO2 emission levels may be due to theCO decrease, which continues the oxidation process because of thehigh oxygen level of the studied fuels, ensuring a more completecombustion. Also, the oxygen overow makes the CO oxidationpossible in the exhaust time, including in the exhaust gas pipelines. Similar results are presented also in [2,16]. This explanationis also sustained by CO emissions reduction compared to those ob-

Fig. 5. Engines efciency variation with load for analyzed fuels.

Fig. 6. Variation of CO emission with percentage of load for different fuels.

vel generate less HC. This fact suggests that the presence of ethanol

I. Barabs et al. / Fuel 89tained for diesel fuel. Increased CO2 emission level should not beconsidered as a negative consequence, because it is reused (con-sumed) in the photosynthesis process of the plants used for biofu-els production.

3.3.3. Nitrogen oxidesThe engines NOx emission level for the analyzed fuels at differ-

ent loads is presented in Fig. 8. It may be observed that the pres-ence of oxygenated components in the studied fuels at smallloads has an unimportant inuence on the NOx emission level, pre-senting especially a small reduction. At medium and high engineloads the NOx emission level is greater compared to those of dieselfuel with 1026%. The increased NOx emission level is explained bythe increased fuel combustion temperature, due to the oxygen con-tent of biodiesel and ethanol, which makes possible a more com-plete combustion and thus an increased combustion

Fig. 7. Variation of CO2 emission with percentage of load for different fuels.temperature, which facilitates the generation of NOx. Also, due tothe ethanols reduced cetane number, the whole blends cetanenumber will decrease. This fact will lead to an increasing fuel ignit-

Fig. 8. Variation of NOx emission with percentage of load for different fuels.in the fuel blend is the reason for increasing HC emissions, and bio-diesel-presence leads to their reduction. An explanation could besustained by the cetane number inuence: biodiesel having a high-er cetane number than diesel fuel facilitates an easier ignition andmore complete fuel blends combustion, meanwhile the ethanolsing delay, which consequently will cause a faster combustion ofair/fuel mixture, generating a faster heat release at the beginningof the combustion process, having as result a higher temperature,which facilitates the formation of NOx [22].

3.3.4. HydrocarbonsHC emission variation with engine loads for the analyzed fuels

is shown in Fig. 9. It may be observed that in the case of 5% ethanolblends HC emissions signicantly decrease compared to diesel fuelin all three engine loads domains. The higher level ethanol blendsgenerate greater HC emissions, and those with higher biodiesel le-

Fig. 9. Variation of HC emission with percentage of load for different fuels.(2010) 38273832 3831low cetane number acts in the opposite direction. Due to its re-duced cetane number ethanol will ignite later and will not burncompletely, increasing in this way the unburned HC level fromthe exhaust gases. The most signicant decrease is with approxi-mately 50% at high loads operating level.

At low and medium loads the obtained results of Kwanchareonet al. [14] are opposed to ours.

3.3.5. SmokeThe CI engines smoke emissions were evaluated through ex-

haust gases opacity measurements, made obvious by the lightabsorbing coefcient (Fig. 10). Exhaust gases opacity has signi-cantly decreased (with more than 50%) in the case of all fuelblends, especially at low and medium loads. At high loads thereduction is between 27.6% in the case of D70B25E5 fuel blendand 50.3% in the case of D85B10E5. Even if it is known that inthe case of using oxygenated fuel blends the particle emissions ofCI engine are lower [15,16], the whole mechanism through whichthe fact is possible has no plausible explanation yet. The smokegeneration takes place in fuel-rich areas of the combustion cham-ber, especially in the fuel-spray core (liquid phase) of the pulver-ized jet. Considering that the oxygen from biofuels ensuresoxidant for the pirolize processes from the jet combustion area, itresults a decrease in solid particle formation [16]. The obtained re-sults are conrmed by the published ones in [16], with the note

Acknowledgment

The research has been nanced by The National University Re-search Council through Executive Agency for Higher Educationand Research Founding, Project No. ID 1098, Contract No. 88/01.10.2007.

References

3832 I. Barabs et al. / Fuel 89 (2010) 38273832that in the mentioned work the solid particle content of exhaustgases was analyzed.

4. Conclusion

In this paper the experimental research results have been pre-sented concerning the CI engines performances and pollutionfueled with three dieselbiodieselbioethanol blend types, whichwere compared to diesel fuel. Due to the used biofuels lower heat-ing value compared to that of diesel fuel, the engines perfor-mances decrease, especially at low engine loads. CO emissionsdecrease signicantly due to an important increase of CO2 emis-sions, as a result of a prolonged oxidation process even in the ex-haust phase, which is possible due to the fact that the analyzedfuel blends have up to 4.55% oxygen. NOx emissions increase espe-cially at medium and high loads, a fact explained by more completecombustion and by increased combustion temperature, due to thepresence of oxygen in fuel. HC emissions decrease in all engineloading conditions. Concerning the smoke emissions it has been

Fig. 10. Particle emissions.observed that they decrease compared to the ones recorded inthe case of diesel fuel, being higher for the fuel blends with highbiofuel content.

In general it may be concluded that the studied fuel blends havelower pollution levels, especially at medium and small loads of en-gine, exceptions being CO2 and NOx, cases in which the recordedvalues are superior to those recorded for diesel fuel.

Concerning the CO emissions, they differ with the engine loads.The presence of the oxygenated organic components in the fuel hasa small effect at low engine loads, but at medium and high loadsthese emissions decrease signicantly.

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Performance and emission characteristics of an CI engine fueled with dieselbiodieselbioethanol blendsIntroductionMaterial and methodsResults and discussionFuel propertiesEngine performancesBreak specific fuel consumptionBrake thermal efficiency

Pollutant emissionsCarbon monoxideCarbon dioxideNitrogen oxidesHydrocarbonsSmoke

ConclusionAcknowledgmentReferences