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Received in revised form21 May 2014Accepted 23 May 2014Available online 21 June 2014

The substitution of petroleum based synthetic lubricant with rapeseed oil based bio-lubricant in a var-

The rising price of crude oil the world over, the growing envi-

engine components such as ring sticking, injector and combustionchamber coking and formation of deposits [8,9]. It is felt during

may be due to the soot loading or oil degradation by oxidation atich may be due toich may be due todditives [10].ceived the idea ofmineral oil, as theecosystem [11,12].mineral oils for thent technical prop-high lubricity, low

evaporative loss and their ability of biodegradability [13,14]. Thus,the search for environmentally friendly substitutes to mineral oils(as base oils) in lubricants has become a frontier area of research inthe lubricant industry in the new paradigm of sustainable tech-nology development propelled by the alarms of environmentaldegradation. Bekal and Bhat investigated neat mineral oil, neatpongamia oil, and mixture of mineral oil and pongamia oil as lu-bricants for the diesel engine fueled with pongamia oil bio diesel.

* Corresponding author. Tel.: 91 99946 99223.E-mail addresses: aru_amace@yahoo.co.in (S. Arumugam), drg.sriram@gmail.

com (G. Sriram), ellsraaj@gmail.com (R. Ellappan).1 Tel.: 91 98948 38623.2

Contents lists available at ScienceDirect

Ener

journal homepage: www.els

Energy 72 (2014) 618e627Tel.: 91 94440 28162.ronmental awareness and the fast depleting crude oil reserves havespurred renewed research interest and advances in alternative fueland lubricant development from agricultural feed stock [1e3]. It isproven that bio diesel is a promising fuel for diesel engine up to 20%blendwith respect to emission, combustion as well as performance.Systematic efforts have been undertaken by many researchers todetermine the suitability of vegetable oil as fuel [4e7]. The use ofbio diesel despite its contribution to a large reduction in enginewear concomitantly creates various other long term problems in

high temperature operation (ii) Oil thinning, whfuel dilution (iii) Deposit formation and wear whthe depletion of wear protecting or dispersing a

Apart from bio diesel, researchers have conusing vegetable oil as the lubricant alternative todisposal of mineral oil leads to pollution ofVegetable oils are perceived to be alternatives topurpose of lubrication because of certain inhereerties like high ash point, high viscosity index,fueled with B20 bio diesel is affected by (i) Oil thickening whichKeywords:Bio-lubricantBio dieselNano CuORapeseed oilVariable compression engine

1. Introductionhttp://dx.doi.org/10.1016/j.energy.2014.05.0870360-5442/ 2014 Elsevier Ltd. All rights reserved.formulated through chemical modications like epoxidation, hydroxylation and esterication process forimproving its thermo-oxidative stability and cold ow properties. The nano CuO (copper oxide) an anti-wear nano additive was added to chemically modied rapeseed oil to improve anti-wear behavior. Tostudy the compatibility of formulated bio-lubricant, two endurance tests of 150 h each were conductedon a four-stroke variable compression ratio engine fueled with B20 rapeseed oil bio diesel at a standardCR (compression ratio) of 17.5:1 using synthetic lubricant (SAE20W40) and formulated bio-lubricant. Thevarious challenges related to performance and emission analysis are discussed and compared withSAE20W40 from no load to full load conditions and at different CR varies from 12:1, 15:1 and 17.5:1 withB20 rapeseed oil based biofuel/bio-lubricant combination. The main ndings show that the combineduse of biofuel/bio-lubricant of rapeseed oil reduced Fe, Al, Cu wear, soot and ash content, when comparedto bio fuel/SAE20W40 combination. The brake thermal, mechanical efciencies and brake power withrapeseed oil based bio-lubricant is comparable with SAE20W40 and also the similar emission spectra wasobserved in the bio-lubricant.

2014 Elsevier Ltd. All rights reserved.

usage: the lubrication oil performance especially for the engineArticle history:Received 20 June 2013 iable compression ratio diesel engine is explored in this study. Rapeseed oil based bio-lubricant wasa r t i c l e i n f o a b s t r a c tBio-lubricant-biodiesel combination of rinvestigation on engine oil tribology, pevariable compression engine

S. Arumugam*, G. Sriram 1, R. Ellappan 2

Department of Mechanical Engineering, Sri Chandrasekharendra Saraswathi Viswa Maheseed oil: An experimentalormance, and emissions of

yalaya, Enathur, Kanchipuram 631561, Tamilnadu, India

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evier .com/locate/energy

ring tribo pair, it does not show any improvement in anti-wearbehavior under tested conditions [24]. In the present study, nanoCuO (copper oxide) was added to the chemically modied rapeseedoil to improve its anti-wear characteristics.

Concomitantly, the examination of the degradation of vegetableoil based bio-lubricant in long term usage in a biodiesel engine isstill to be understood. All the review of literature done has left the

Chennai. Table 1 shows the fatty acid composition of rapeseed oil.

nergy 72 (2014) 618e627 619Further, they reported that the best results were recorded for thefuel-lubricant combination of neat pongamia oil [15].

Nevertheless, the principal weakness of vegetable oils forlubrication has been their tendency to oxidize at higher tempera-ture, and giving rise to gum, varnish and sludge formation at lowertemperature [16]. The existence of an unsaturated C]C bond isresponsible for their poor oxidative stability [17]. Many literaturerevealed that technical solutions such as chemical modication andadditivation were suggested to overcome the poor thermo-oxidative stability and low temperature uidity of vegetable oils.Efforts were made to improve the low temperature uidity ofvegetable oils using an additivation method by blending vegetable

Abbreviation

ASTM American Society for Testing of MaterialsBP brake powerBSFC brake specic fuel consumptionBTE brake thermal efciencyB100 100% by vol. rapeseed oil methyl esterCA crank angleCO carbon monoxideCMRO chemically modied rapeseed oilCR compression ratioCuO copper oxideFTIR Fourier Transform InfraredHC hydrocarbonHSU Hartridge Smoke UnitME mechanical efciencyNOx oxides of nitrogenRME rapeseed oil methyl esterSAE Society of Automotive EngineersTAN total acid numberTDC top dead centerVCR variable compression ratio

S. Arumugam et al. / Eoils with diluents such as poly-a-olen and diisodecyl adipate [18].Zulkii et al. made an attempt to improve the oxidative stability,low temperature uidity and anti-wear characteristics of palm oilby transesterication of trimethylolpropane with palm oil methylester [19].

The unsaturation present in the fatty acid molecule of thevegetable oil can be used to introduce various functional groups bycarrying out chemical modications. Among them, epoxidation andhydroxylation are a few of the most widely used reaction. Kim andSharma discussed the possibilities of utilization of epoxidizedproducts of vegetable oils in PVC (poly vinyl chloride) formulationsand bio-thermoset plastics [20]. The application of epoxidizedrapeseed oil as a potential biodegradable lubricant was describedby Wu et al. [21] and additionally they reported that the chemicalmodication treatment did not have any adverse effect on thebiodegradability of base stock. Although many valuable polymericmaterials and lubricants are derived from chemically modiedvegetable oil, use of chemically modied oil as automotive lubri-cant has not been reported. In line with that, the authors haveformulated bio-lubricant through chemical modications of rape-seed oil like epoxidation, hydroxylation and esterication process[22,23]. Further, the issue of friction and wear characteristics of thediesel engine's cylinder liner-piston ring combination under theinuence of formulated bio-lubricant and commercial syntheticlubricant (SAE20W40) using a high frequency reciprocating trib-ometer rig were addressed by Arumugam and Sriram [24]. Thoughthe bio-lubricant enhances the frictional characteristics of liner-

were adapted from our earlier investigation [24]. Furthermore 0.5%

w/w nano CuO are in the range of ~40e70 nm supplied by M/S USResearch Nano Materials Inc, USA, was used in this experimentalstudy, for which the true size and density were provided by thesuppliers. An ultrasonic bath sonicator, Make: OSCAR model PR-1000, ultrasonic power: 750 W and operating frequency:

Table 1Fatty acid composition of rapeseed oil.

Fatty acid % (w/w)

Palmitic acid (C16:0) 5.7Stearic acid (C18:0) 2.2Oleic acid (C18:1) 58.5Linoleic acid (C18:2) 24.5The transesterication process was carried out for the preparationof RME (rapeseed oil methyl ester). The transesterication processwas carried out rst by preparing sodium methoxide by mixingNaOH (sodium hydroxide) in methanol. The quantity of methanolused was in the molar ratio of 6:1 with oil. Two hundred millilitersof methoxide and 700ml of oil weremixed properly and heated in amantle at 60 C for one hour using a reux condenser. Then, it wasallowed to settle for another 12 h. Using a separating funnel,glycerol was separated. The bubble wash was done by mixingmethyl ester with distilled water to remove excess of alcohol,catalyst and glycerol. Then, to remove the moisture content in themethyl ester, it was treated with anhydrous sodium sulphate,which is commonly used as moisture absorbing agent. Further-more, B20R biodiesel was prepared by mixing 20% by vol. of RMEand 80% by vol. of diesel. Table 2 indicates the properties of bio-diesel and diesel fuel. Characterization of diesel and biodiesel wascarried out in accordance with ASTM (American Society for Testingof Materials) standards.

2.2. Formulation of rapeseed oil based bio-lubricant

To formulate the rapeseed oil based bio-lubricant, rapeseed oilwas chemically modied through epoxidation, hydroxylation orring opening process and followed by esterication process of thering opened product in order to improve its thermo-oxidativestability and lower the pour point. The detailed procedure forchemical modication process of rapeseed oil and its mechanismscope for the investigators to study the impact of chemicallymodied rapeseed oil with nano additive as automotive lubricantfor the engine fueled with rapeseed oil biodiesel to investigate theengine performance, emissions and long term durability of thelubricating oil.

2. Experimental details

2.1. Preparation of B20 rapeseed oil biodiesel

Raw rapeseed oil, methanol and sodium hydroxide, which arerequired for transesterication process, anhydrous sodium sul-phate, and concentrated hydrochloric acid used in bubble washingprocess, were procured from M/S Ganapathy Trading Company,Linolenic acid (C18:3) 9.1

36 kHz was used to ensure homogeneous dispersion of CuO nanoparticles into CMRO (chemically modied rapeseed oil) without

specialized Lab View based engine analysis software package En-gine SoftLVwas employed for online performance and combustionanalysis and that gave the output in graphical and numerical form.The photographic view of the VCR engine for performance andemission test is shown in Fig. 1(a). The specications of the VCR testengine are summarized in Table 5.

2.3.1. Performance and emission testThe performance and emission tests were carried out at the

rated speed of 1500 rpm, from no load to full load conditions and atvarious CRs (compression ratios), say 12:1, 15:1 and 17.5:1. Thethermal performance of the engine is evaluated in terms of BSFC(brake specic fuel consumption), BTE (brake thermal efciency),

Table 2Properties of B20 rapeseed oil and diesel.

Properties B100 B20 Diesel Equipment used

Density @15 C, kg/m3 (ASTM D1298) 870 852 840 HydrometerKinematic viscosity@40; C, cSt (ASTM D445) 4.52 2.73 3.02 Glass capillary viscometerFlash point, C (ASTM D92) 181 60 48 Cleveland open cup testerCaloric value, kJ/kg (ASTM D240) 37,100 39,340 44,500 Bomb calorimeter

S. Arumugam et al. / Energy 72 (2014) 618e627620agglomeration. The CMRO and CuO nano particles (0.5% by wt.)were initially taken in beaker. The beaker was kept in an ultrasonicbath sonicator and allowed to vibrate for a period of 2 h and thenthe blend was kept in a rotary shaker for another 5 h. Table 3 showsthe properties of raw rapeseed oil and chemically modied rape-seed oil dispersed with nano CuO. The chemical modication ofrapeseed oil was conrmed by using FTIR (Fourier TransformInfrared) spectroscopic analysis as described in our recent investi-gation [25]. Conventional methods for stabilization such as the useof surfactants was not tried out, as the presence of such materialswould affect the performance of the lubricating oil due to forma-tion of froth under continued use in the system. Instead, the studieswere conned to lowmass fractions of the nano particles to ensurethat agglomeration did not occur and chemically modied rape-seed oil with nano CuO was stable without any sedimentation for asubstantially long time period of several days after its preparation.Dispersion analysis was performed using an ultraviolet spectro-scope. The oil sample was lled in cuvette of square shaped 3.5 mlcapacity which was made of quartz subsequently ultraviolet lightrays were passed through the lubricant samples. The absorbancelevel of visible light, proportional to the dispersion of nano particlesin the lubricant sample was measured using visible spectroscopyover a period of time. From the dispersion analysis, it was observedthat nano CuO in chemically modied rapeseed oil remained stableup to 700 h of its preparation.

2.3. Experimental methodology

Engine performance, emission and endurance tests were con-ducted on a computerized four-stroke, single cylinder, water-cooled, direct injection, VCR (variable compression ratio) dieselengine using two different fuel-lubricant combinations. The enginewas operated with B20 rapeseed oil biodiesel/synthetic lubricant(SAE20W40) combination and then followed by B20 rapeseed oilbiodiesel/bio-lubricant (chemically modied rapeseed oildispersed with 0.5% by wt. nano CuO) combination. The engine wasdirectly coupled to an eddy current dynamo meter using exiblecoupling and a stub shaft assembly; the output of the eddy currentdynamo meter was connected to a strain gauge load cell of dataacquisition device-NI USB-6210 Bus Powered M series. The speci-cations of the dynamo meter are summarized in Table 4. A

Table 3

Properties of raw rapeseed oil, rapeseed oil based bio-lubricant and SAE20W40.

Properties Standard Raw rape

Viscosity @100 C (cSt) ASTM D445 8Pour point (C) ASTM D97 11Flash point (C) ASTM D92 320Viscosity index ASTM D2270 220Specic gravity @ 15 C ASTM D287 0.85Oxirane content (%) AOCS cd 9-57 0Biodegradability (%) CEC-L-33-A93 >95Rotary bomb oxidation time (min) ASTM D2272 16Iodine value AOCS cd 1-25 120and ME (mechanical efciency) at various CRs were calculatedautomatically and recorded while loading the engine from no loadto full load condition. The BSFC was evaluated by the software onthe basis of fuel ow and brake power developed by the engineusing an expression BSFC (Volumetric fuel ow in 1 h fueldensity/brake power); BTE (brake power 3600 100/volu-metric fuel ow in 1 h caloric value of fuel); ME (Brake power/Indicated power). The engine exhaust gas emissions such as CO(carbon monoxide), HC (hydrocarbon), NOx (oxides of nitrogen),and smoke emissions were measured. AVL 437 smoke meter andAVL DI gas analyzer were used for the smoke and other emissionmeasurements respectively. The pressure inside the combustionchamber was measured using a piezo sensor make: PCB piezo-tronics; model: HSM 111422; range 5000 psi which was mountedon center of the cylinder head to minimize error. The crank angleand the position of TDC (top dead center) were measured usingKubler-Crank angle sensor. The in-cylinder pressure, crank angleand net heat release was recorded at every crank angle and at aparticular load for 10 cycles.

Table 4Specications of Eddy current dynamo meter.

Description Specications

Make Saj Test Plant Pvt. Ltd.Model AG 10Maximum speed, rpm 10000Torque, Nm 11.5Hot coil voltage, volt 60Continuous current, amp 5.0Cold resistance, ohm 9.8Air gap, mm 0.77/0.63seed oil Chemically modied rapeseed oil SAE20W40

15.4 15.215 21242 250179 133

0.89 0.905.81 5.76

>95 >9535 385.1 e

S. Arumugam et al. / Energ2.3.2. Endurance testIn addition to the engine performance and emission tests, a real

time engine endurance test was also conducted on two differentdiesel engines of the same make and specications to check the

Fig. 1. (a) & (b) Expe

Table 5Specications of VCR engine.

Description Specications

Make & model Kirloskar/PS234Bore stroke 87.5 110 mmRated power 3.5 kW@1500 rpmCompression ratio 12:1e18:1Load indicator Digital, range 0e50 kgLoading Eddy current dynamo meterPiezo sensor Range 5000 psiy 72 (2014) 618e627 621compatibility of formulated bio-lubricant in accordance with In-dian standard IS: 10000 Part IX [26]. One engine was operated withB20 rapeseed oil biodiesel/synthetic lubricant (SAE20W40) com-bination and the other was operated with B20 rapeseed oilbiodiesel/bio-lubricant combination. Both the endurance testswere carried out for a period of 150 h each at a standard CR of 17.5:1and at 80% load condition. The 80% load point was determined byconsidering the stable operation of the engine. The photographicview of test engines for the endurance test is shown in Fig. 1(a) and(b). For the tribological evaluation of the lubricant, an oil samplewas drawn from the engine crankcase at regular intervals of 25 hwithout topping up the engine oil. Then the oil sample wasanalyzed for measuring various physio-chemical properties. Anatomic emission spectroscopy method, ASTM 6595 was used forthe wear debris analysis. The Karl Fischer method, ASTM D6304

rimental setup.

nge

500500 m50020,10%50110200120

nergwas used to measure water content in the oil samples sensitive tolow moisture content. The ash content of used engine oil wasmeasured as per ASTM D482. TAN (total acid number) wasmeasured as per ASTMD664. The InfraCal Soot meter, Model HATR-CP was used for on-site measurement of the soot level in usedengine oil and it was measured as per ASTM D7686. Fuel dilution inused engine oil was measured as per ASTM D322. Lubricant vis-cosity was measured @100 C as per ASTM D445. The ash point ofthe lubricant was evaluated bymeans of Pensky-Martens apparatusas per ASTM D92.

2.3.3. Error analysisThe experimental uncertainty may be taken as the possible

value the error may have. The uncertainties in the experimentsmayarise from the instrument type, calibration and observation. Sup-pose, a set of measurements is made and these measurements areused to calculate some desired result of the experiments. To esti-mate the uncertainty in the calculated result on the basis of un-certainties in the primary experiments, the methodology adoptedwas this: The result R represents the given function of the inde-pendent variables X1, X2, X3,Xn. Thus R R(X1, X2, X3,Xn).WR is the uncertainty in the result and W1, W2, W3Wn are theuncertainties in the independent variables. Then the uncertainty inthe result is given by WR {[(dR/dX1)W1]2 [(dR/dX2)W2]2 [(dR/dXn)Wn]2}1/2. The percentage of uncertainty of various pa-rameters were calculated by the above mentionedmethod [28] andis given in Table 6.

3. Results & discussion

3.1. Performance characteristics

The performance characteristics like BTE and ME of VCR enginefueled with B20 rapeseed oil biodiesel and lubricated with

Table 6List of instruments, their range, accuracy and percentage uncertainties.

Instrument Type/Manufacturer Ra

Fuel ow measurement Differential Pressure Transmitter 0eLoad sensor Strain Gauge, Load cell 0eAir ow measurement Pressure transmitter 20NOxHCCO

9=;

AVL-5gas analyzer 0e0e0e

Smoke meter AVL Smoke meter 0ePiezo sensor PCB Piezotranics 0eSpeed measuring unit Kubler Germany 0eTemperature sensor RTD PT100 type K Thermocouple 0eCrank angle encoder Kubler Germany

S. Arumugam et al. / E622SAE20W40/bio-lubricant at three distinct CRs like 17.5, 15 and 12from no load to full load are depicted in Fig. 2(a)e(c) respectively.The BTE increases with increase in CR and load for both fuel-lubricant combinations, as lesser frictional losses were encounteredat higher loads and higher CRs. The increasing trend of BTE for theengine lubricated with SAE20W40 and bio-lubricant was foundmuch closer to each other. At full load, the BTE for the biodiesel/bio-lubricant combination were 30%, 27%, and 25% and its corre-sponding values for biodiesel/SAE20W40 combination are 28%,26%, and 23% for CR 17.5, CR 15 and CR 12 respectively. With theincrease in CR from 12 to 17.5, the BTE was found to increase up to5% for both fuel-lubricant combinations. At higher CR, the highercombustion temperature which results in better combustion of fuelmight be the reason for the higher BTE. Similar variation was alsoobserved by Muralidharan et al. [5]. The marginal improvement inBTE with the use of biodiesel/bio-lubricant combination can beattributed to higher lubricity of fuel/lubricant combination ofrapeseed oil which reduces the frictional losses that ultimatelyleads to an improvement in brake power and consequently in-creases the BTE. Further, at higher CR the conversion of chemicalenergy of biodiesel into mechanical energy was also higher.

The ME is found to increase signicantly with increase in load aswell as CR. At full load, the ME for bio-lubricant was noticed having67%, 60% and 57% respectively, and its corresponding values forSAE20W40 were 58%, 55%, and 56% respectively for CR 17.5, CR 15,and CR 12.5 respectively. The signicant improvement in ME withbio-bio combination was due to the nano CuO present in rapeseedoil based bio-lubricant that played a vital role in reducing thefrictional power effectively improving the BP (brake power) andconsequently increased the ME. The same trend was also reportedby Muralidharan et al. [5] for biodiesel/SAE20W40 combination. Itis observed that from no load to full load, the BP increases withincrease in CR. At CR 17.5, the maximum BP observed at full loadcondition was 3.47 kW and 3.44 kW for the bio-lubricant andSAE20W40 respectively.

The variation of BSFC for both fuel-lubricant combinations andat different CRs with load is as shown in Fig. 2(d). The BSFC de-creases with load signicantly for both the fuel-lubricant combi-nations as the power output per unit fuel consumption increases athigher loads. The fuel required to operate the engine is less than theincrease in present in BP due to relatively less portion of the heatlosses at higher loads. Similarly, the BSFC decreases with the in-crease in CR. At full load, with biodiesel/SAE20W40 combination,the BSFC for CR 12, CR 15, and CR 17.5 are 0.38, 0.33, and 0.3 kg/kWhrespectively. The values for BSFC with bio/bio combination at CRs of12, 15, and 17.5 are 0.33, 0.31, and 0.29 kg/kWh respectively. Out ofthe three CRs selected, the CR 17.5 gave the lowest BSFC what wasevident was that at higher CR, the BP increased. During trials withdifferent fuel-lubricant combinations and CR, the synergic effectwas seen with the bio/bio combination when the CR was main-

Accuracy % Uncertainty

mm water column 1 mm of water column 1kg 0.1 kg 1m of water column 1 mm of water column 10 ppm 10 ppm 0.5000 ppm 10 ppm 0.1

0.01% 0.31 1

bar 0.5 bar 10 rpm 5 rpm 0.50 C 1 C 0.5

0.5CA 2

y 72 (2014) 618e627tained at 17.5 where the BSFC was minimum for the whole loadrange with an improvement of about 3.44% over the biodiesel/SAE20W40 combination while operating the engine at CR-17.5 andat full load conditions [1]. Higher lubricity of bio/bio combination ofrapeseed oil was responsible for improving the BP and lowering theBSFC in comparisonwith biodiesel/SAE20W40 combination. Hence,it become evident that bio-lubricant could be used as an alternativelubricant for synthetic lubricant on VCR engine without signicantchanges in engine power and fuel economy.

3.2. Emission characteristics

In diesel engine the CO was formed during intermediate com-bustion stages. However, diesel engines that operate on the leanside of stoichiometric ratios, the CO emissions were found low.Fig. 3(a) shows the variation of CO emissions with respect to load

nergS. Arumugam et al. / Efor both fuel-lubricant combinations at three distinct CRs. Almostsimilar CO emissions were observed with both bio/bio and bio-diesel/SAE20W40 combination. CO emission decreased with theincrease in CR and load. At full load conditions with biodiesel/SAE20W40 combination, CO emission for CR 12, CR 15, and CR 17.5were 0.17, 0.07, and 0.03% vol. respectively and this value corre-sponded to bio/bio combination of 0.16, 0.06, and 0.03% vol.

Fig. 2. Performance characteristics a) For CR-17.5 b) For

Fig. 3. Emission characteristics a)y 72 (2014) 618e627 623respectively. On comparing the emissions at different CRs, the COemissions were lower in CR 17.5. At higher load and CR, highertemperature in the combustion chamber resulted in better com-bustion of fuel leading to very low production of CO. These resultsconcurred with those obtained byMuralidharan et al., [5] and Tesfaet al., [6]. who compared the performance of a diesel enginerunning on biodiesel/SAE20W40 combination.

CR-15 c) For CR 12 (d) Variation of BSFC with load.

CO b) Smoke c) HC d) NOx.

nergS. Arumugam et al. / E624Smoke formation occurs where there is extreme air deciency.In general, air or oxygen deciency is locally present in diesel en-gine. It increases as the air to fuel ratio decreases. Fig. 3(b) showsthe variation of smoke emissions for both fuel-lubricant combina-tion with respect to load and at three distinct CRs. With increase inload, the smoke opacity increased because a richer mixture wasburnt in the cylinder. Smoke was less at higher CR, due to the factthat at higher CR, the heat of the compressed air was high enoughto cause better combustion of fuel. At lower CR, incomplete com-bustion of fuel took place. With the increase in CR from 12 to 17.5,HSU (Hartridge Smoke Unit) decreased upto 41% for both fuel-lubricant combinations. Higher BTE observed for higher CR alsosupports this fact. This result agrees with the ndings of Mur-alidharan et al. [5] and bekal and Bhat [15].

HC emissions consisted of fuel that was unburned or partiallyburned. The amount of HC depends on the engine operating con-ditions and fuel properties. Fig. 3(c) shows the variation of HCemissions with various loads for two fuel/lubricant combinations atthree different CR. At full load conditions, with biodiesel/SAE20W40 combination, HC emission for CR 12, CR 15, and CR 17.5were 100, 122 and 70 ppm respectively and it is corresponded tobio/bio combination of 101, 120, and 68 ppm respectively. An in-crease in CR results in a shorter ignition delay. A shorter delayperiod would result in less overmixing of fuel and air and lowerHC emissions. The high combustion temperature obtained at highCRs tended to increase oxidation of the unburned HC. Also at ahigher CR, HC emissions were low, might be because of increasedpeak combustion pressure and temperature, as better combustion

Fig. 4. P-q curve (a) for bio/bio combination (b) for biodiesel/SAE20W40 combination. Ny 72 (2014) 618e627could be ensured. Increase in CR although may reduce the HC, butdue to higher combustion temperature it may have adverse effecton NOx emissions. Higher combustion temperature on the otherhand would result in increase of soot oxidation. Fig. 3(d) shows thevariation of NOx emission with load for various CR. It is well knownthat the vegetable oil based fuel contains a small amount of ni-trogen. This contributes towards NOx production [2]. At full loadconditions, with biodiesel/SAE20W40 combination, the NOx emis-sion for CR 12, CR 15, and CR 17.5 were 125, 212, and 478 ppmrespectively and this value corresponded to bio/bio combination of130, 210, and 480 ppm respectively. It is observed that NOx emis-sion increased with load and the minimum NOx emissions corre-sponded to CR 12 and it increased as the CR increased, because theformation of NOx was dependent on the operating temperature ofthe cylinder and the oxygen availability. At lower CR, less oxygen isavailable for the formation of NOx from the biodiesel due toincomplete combustion of fuel but at higher CR, the NOx emissionsfor biodiesel are found to be higher because of greater availability ofoxygen from biodiesel due to complete combustion and properbreak up of the fuel droplets during injection. Nearly similaremission spectra was observed with both bio-lubricant as well asSAE20W40. The variation in NOx emission in this study was inaccordance with Yuksek et al., [27].

3.3. Combustion characteristics

Fig. 4(a) and (b) show the variation of cylinder pressure withcrank angle for bio/bio combination and biodiesel/SAE20W40

et heat release c) for bio/bio combination d) for biodiesel/SAE20W40 combination.

nergS. Arumugam et al. / Ecombination respectively at CR 17.5 and full load conditions. It isobserved from the gures that, the peak cylinder pressure de-creases at the start of combustion and increases further. Peakpressure depends mainly on the combustion rate in the initialstages, which is inuenced by the fuel intake component in theuncontrolled heat release phase [5]. It is observed that peak pres-sures of 56 bar and 48 bar were recorded for biodiesel/bio-lubricantcombination and biodiesel/SAE20W40 combination respectively.Better combustion with bio/bio combination than that of biodiesel/SAE20W40 combination is responsible for higher cylinder peakpressure. Fig. 4(c) and (d) shows the variation of net heat releasewith crank angle for biodiesel/bio-lubricant combination and bio-diesel/SAE20W40 combination respectively at CR 17.5, full loadcondition. It is seen that the maximum heat release rate occurred atthe premixed combustion phase for both fuel-lubricant

Fig. 5. As a function of lubricant usage a) Wear debris b) Water content c)y 72 (2014) 618e627 625combination. The heat release diagram also shows a shorter pre-mixed and longer diffusive combustion phase. The maximum heatrelease rate was 40 J/CA (crank angle) for bio/bio combination,while it was 36 J/CA for biodiesel/SAE20W40 combination. Themarginal improvement in net heat release and peak combustionpressure might be due to better spray formation, better airentrainment and improvement in volatility characteristics ofbiodiesel/bio-lubricant combination than with biodiesel/SAE20W40 combination [1].

3.4. Endurance test results

3.4.1. Wear debris analysisFig. 5(a) shows the comparison of iron (Fe), aluminum (Al), lead

(Pb) and copper (Cu) wear in SAE20W40 and chemically modied

Ash content d) TAN e) Soot level f) Kinematic viscosity g) Flash point.

Fuel soot level is a good indicator of engine combustion ef-

for SAE20W40 and bio-lubricant respectively. The test results

29% for the bio-lubricant respectively. Kinematic viscosity of engine

The trend of decrease in ash point values is shown in Fig. 5(g).

nergrapeseed oil bio-lubricant after 150 h of operation. The wear ele-ments namely Fe, Cr, Ni, Mo, Al, Cu, Sn, and Pb were measured inengine oil sample. As the wear elements like Cr, Ni, Mo, Sn are tooinsignicant to report, only Fe, Al, Pb and Cu wear are discussed. Ingeneral, ironwear in both lubricants were low and within expectedlimits. In biodiesel engine, lubricated with SAE20W40, the ironwear was 90 ppm compared to 73 ppm with that of bio-lubricant.The low iron wear pattern found in biodiesel engine could havebeen because of less soot formation and consequently there wasless abrasive wear. Furthermore, the presence of anti-wear additive(nano CuO) in bio-lubricant plays a vital role in reducing the weareffectively. Ironwear elements are due to the wear of cylinder linerand piston ring, gear, crank shaft, cam shaft, valve train and wristpin. It is observed that the aluminum wear was 11 ppm with bio-lubricant compared to 24 ppm with SAE20W40. This shows thatAl wear of both lubricants are comparable. The Al particle in theengine oil was because of piston wear.

Similarly, the higher Cu wear with SAE20W40 was about266 ppm and for the bio-lubricant it was only about 15 ppm as aresult of lower bushing, main and connecting rod bearing wear.This increase in copper wear with SAE20W40 may be due to theacidity of blow by gases entering into the oil sump and coming intocontact with the bearing. Further, lower Pb wear of about 7 ppmwith bio-lubricant compared to 66 ppm with SAE20W40 wasobserved and this might be due tomain and connecting rod bearingbushes. The above trend supports the higher lubricity of rapeseedoil based bio-lubricant. The presence of anti-wear nano CuO in bio-lubricant predominantly reduced the wear while, as per the nd-ings of Yuksek et al. [27] higher copper, iron and negligible Pb wearwere reported with the use of B100 rapeseed oil biodiesel/SAE20W40 combination [27].

3.4.2. Water contentWater presence in engine oil indicates contamination from

outside sources. These sources may be condensation of moisturefrom the atmosphere. Fig. 5(b) shows the water content of usedengine oil. It was observed that the water content was not inmeasuring range for bio-lubricant as compared to that ofSAE20W40 which accounts to 0.18%. The additional lubricity pro-vided by rapeseed oil bio-lubricant results in lower blow by gasesthat leads to lower amount of water vapor condensing in thecrankcase oil which might be the reason for this.

3.4.3. Ash contentAsh content in lubricating oil is primarily due to non-

carbonaceous materials present in the lubricating oil that in-dicates metallic wear debris and foreign bodies in the system. Dueto similar operating conditions of the both the lubricants, thecontribution of foreign particles was assumed to be similar. Hencethe ash content present in the engine oil mainly reected the weardebris. The ash content of used engine oil is shown in Fig. 5(c). It isobserved that the ash content in the bio-lubricant is approximately70% lower than that of biodiesel fueled engine lubricated withSAE20W40. The lower Fe, Al, Cu, and Pb wear with bio-lubricantsupport these results.

3.4.4. TANTAN is the quantity of the acid or acid-like derivatives in the

lubricant. TAN is an indicator of oil serviceability. The TAN value offresh oil cannot be nil since base oil/oil additives can be acidic innature. Fig. 5(d) shows the TAN variation in the used lubrication oil.A 15% decrease in TAN value is observed with the bio-lubricantengine while TAN decreased by 40% for the engine lubricated withSAE20W40 from its initial value which is not in line with the

S. Arumugam et al. / E626ndings of Yuksek et al. [27]. It was reported that engine oil withIt is observed that ash point of both lubricants decreased signi-cantly for every sampling period. After 150 h of engine oil usage, theash point of SAE20W40 and bio-lubricant was 210 C and 195 Crespectively. This clearly shows that the decomposition of lubricantin bio-lubricant engine was comparatively higher than that of theengine lubricated with SAE20W40. This trend was due to higheroil may decrease in the beginning due to shear stress of the vis-cosity index improver and start increasing later due to oil oxidation.Other than nano CuO as anti-wear additive, bio-lubricant doesn'thave any other additive elements which might be the primaryreason for excess viscosity reductionwith bio-lubricant. Excess fueldilution with bio-lubricant might be the secondary cause of thistrend. However, the synthetic lubricant contains nearly 10% addi-tive package. Similarly Ramprabhu et al. [10] reported 18% reduc-tion in kinematic viscosity with the use of biodiesel/syntheticlubricant combination.

3.4.8. Flash pointdemonstrated that low percentage of fuel dilution was observedwith SAE20W40. Excess fuel dilution in bio-lubricant indicates thata potential problem may occur with the injector, fuel pump, gasketor seals. Faulty operation of fuel systemmay lead to excessively richmixture. This hypothesis was supported by an excessive reductionof oil viscosity and ash point. Agarwal [29] observed the sametrend of fuel dilution with B20 biodiesel/SAE20W40 combination.

3.4.7. Kinematic viscosityViscosity measurement gives information about oil thickening

due to soot ingress, oil oxidation, oil degradation, and oil dilution/contamination with fuel, water or coolant and this trend is shownin Fig. 5(f). The decrease in viscosity is compared with initial oilviscosity during the period of 150 h of engine operation. It isobserved that the viscosity reduction is 21% for the SAE20W40 andciency. Fig. 5(e) shows the soot content present in the lubricating oilafter 150 h of engine operation. The soot level in the bio-lubricant isfound to be almost 40% lower compared to that of SAE20W40. Dueto better combustion of bio-lubricant/B20 biodiesel combination,bio-lubricant engine showed a comparatively lower soot level. Sootis formed due to incomplete combustion products of fuel whichcomes into oil through blow by gases into the crankcase. Theseresults are also in consistence with previous research ndings ofYuksek et al. [27]. This indicates the usage of biodiesel/bio-lubricantcombination reduces oil thickening by soot loading.

3.4.6. Fuel dilutionEngine lubricant can become contaminatedwhen unburned fuel

blows by through the piston ring and ends up in the crankcase. Fueldilution reduces the oil viscosity and attenuates detergent or ad-ditive performance. In general, excess fuel dilution makes the oilunt for further use. Hence, fuel dilution should be clearly moni-tored. The dilution eventually reaches

4. Conclusions

Nearly all agricultural farmmachinery use direct injection dieselengine and keeping this point in mind, a typical engine systemwhich widely used in agriculture sector was selected for the pre-sent experimental work. Based on the present experimental in-vestigations, the conclusions are drawn.

The engine can be safely operated with biodiesel/bio-lubricantcombination without any modication of the engine and sig-nicant changes in engine power and fuel economy.

A marginal improvement in brake power, brake thermal ef-ciency, and mechanical efciency was observed with the use ofrapeseed oil based bio-lubricant. The marginal improvement inbrake thermal efciency can be attributed to higher lubricity of

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[9] Basinger M, Reding T, Rodriguez-Sanchez FS, Lackner KS, Modi V. Durabilitytesting modied compression ignition engine fueled with straight plant oil.Energy 2010;35:3204e20.

[10] Ramaprabhu R, Bharadwaj O, Abraham M. Comparative study of engine oilcharacteristics in utility vehicles powered by turbo-charged direct injectiondiesel engines fuelled with biodiesel blend and diesel fuel. SAE. 2008-28-0117.

[11] Dowson D. History of tribology. Bury St. Edmunds, Suffolk, UK: ProfessionalEngineering Publication Limited; 1998.

[12] Ssempebwa JC, Carpenter DO. The generation, use and disposal of wastecrankcase oil in developing countries: a case for Kampala district of Uganda.Hazard Mater 2009;161(2e3):835e41.

[13] Mercurio P, Burns KA, Negri A. Testing the eco toxicology of vegetable versusmineral based lubricating oils: degradation rates using tropical marine mi-crobes. Environ Pollut 2004;129(2):165e73.

[14] Cheenkachorn Kraipat, Fungtammasan Bundit. Development of engine oilusing palm oil as a base stock for four-stroke engines. Energy 2010;35:2552e6.

[15] Bekal S, Bhat NR. Bio-lubricant as an alternative to mineral oil for a CI engine

S. Arumugam et al. / Energy 72 (2014) 618e627 627rapeseed oil based bio-lubricant. Nearly similar emission spectra were observed with both bio-lubricant as well as SAE20W40 at all loads and compressionratios.

Ferrogram revealed a reduced Fe, Al and Cu wear for biodiesel/bio-lubricant combination, suggesting inherent lubricity ofrapeseed oil as bio fuel and bio-lubricant.

On the whole, the use of bio fuel/bio-lubricant combination ofrapeseed oil can play a vital role in helping developing countries toreduce the environmental impact of fossil energy sources. Withadditional R&D, genetic development of rapeseed and improved oilprocessing technologies, there is a possibility that a rapeseed oilbased automotive lubricant will be able to exist in the near future.

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Bio-lubricant-biodiesel combination of rapeseed oil: An experimental investigation on engine oil tribology, performance, an ...1 Introduction2 Experimental details2.1 Preparation of B20 rapeseed oil biodiesel2.2 Formulation of rapeseed oil based bio-lubricant2.3 Experimental methodology2.3.1 Performance and emission test2.3.2 Endurance test2.3.3 Error analysis

3 Results & discussion3.1 Performance characteristics3.2 Emission characteristics3.3 Combustion characteristics3.4 Endurance test results3.4.1 Wear debris analysis3.4.2 Water content3.4.3 Ash content3.4.4 TAN3.4.5 Soot content3.4.6 Fuel dilution3.4.7 Kinematic viscosity3.4.8 Flash point

4 ConclusionsReferences