diesel engine alternate

Applied Thermal Engineering 29 (2009) 2738–2744

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Applied Thermal Engineering

journal homepage: www.elsevier .com/locate /apthermeng

Performance, emission and combustion characteristics of a DI diesel engineusing waste plastic oil

M. Mani a,*, C. Subash b, G. Nagarajan b

a Department of Mechanical Engineering, Rajalakshmi Engineering College, Chennai, Tamil Nadu, Indiab Department of Mechanical Engineering, College of Engineering Guindy, Anna University, Chennai, India

a r t i c l e i n f o

Article history:Received 3 October 2008Accepted 20 January 2009Available online 25 January 2009

Keywords:Diesel engineDieselWaste plastic oilPerformanceEmissionCombustion

1359-4311/$ - see front matter � 2009 Elsevier Ltd. Adoi:10.1016/j.applthermaleng.2009.01.007

* Corresponding author. Tel.: +91 4562 238160; moE-mail address: [email protected] (M

a b s t r a c t

Increase in energy demand, stringent emission norms and depletion of oil resources have led theresearchers to find alternative fuels for internal combustion engines. On the other hand waste plasticpose a very serious environment challenge because of their disposal problems all over the world. Plasticshave now become indispensable materials in the modern world and application in the industrial field iscontinually increasing. In this context, waste plastic solid is currently receiving renewed interest. Theproperties of the oil derived from waste plastics were analyzed and compared with the petroleum prod-ucts and found that it has properties similar to that of diesel. In the present work, waste plastic oil wasused as an alternate fuel in a DI diesel engine without any modification. The present investigation was tostudy the performance, emission and combustion characteristics of a single cylinder, four-stroke, air-cooled DI diesel engine run with waste plastic oil. The experimental results have showed a stable perfor-mance with brake thermal efficiency similar to that of diesel. Carbon dioxide and unburned hydrocarbonwere marginally higher than that of the diesel baseline. The toxic gas carbon monoxide emission of wasteplastic oil was higher than diesel. Smoke reduced by about 40% to 50% in waste plastic oil at all loads.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Plastics have become an indispensable part in today’s world.Due to their lightweight, durability, energy efficiency, coupled witha faster rate of production and design flexibility, these plastics areemployed in entire gamut of industrial and domestic areas. Plasticsare produced from petroleum derivates and are composed primar-ily of hydrocarbons but also contain additives such as antioxidants,colorants and other stabilizers [1,2]. Disposal of the waste plasticsposes a great hazard to the environment and effective method hasnot yet been implemented.

Plastics are non-biodegradable polymers mostly containing car-bon, hydrogen, and few other elements like nitrogen. Due to itsnon-biodegradable nature, the plastic waste contributes signifi-cantly to the problem of waste management. According to anationwide survey which was conducted in the year 2000, approx-imately 6000 tonnes of plastic waste were generated every day inIndia, and only 60% of it was recycled, the balance of 40% could notbe disposed off. Today about 129 million tonnes of plastics are pro-duced annually all over the world, out of which 77 million tonnesare produced from petroleum [3]. In India alone, the demand forplastics is about 8 million tonnes per year. More than 10,000 met-ric tonnes per day of plastics are produced in India and almost the

ll rights reserved.

bile: +91 9884647061.. Mani).

same amount is imported by India from other countries. The percapita consumption of plastics in India is about 3 kg when com-pared to 30 kg to 40 kg in the developed countries. Most of thesecome from packaging and food industries. Most of the plasticsare recycled and sometimes they are not done so due to lack of suf-ficient market value. Of the waste plastics not recycled about 43%is polyethylene, with most of them in containers and packaging.

2. Waste plastic oil in diesel engines

Diesel engines are most preferred power plants due to theirexcellent driveability and higher thermal efficiency. Despite theiradvantages, they emit high levels of NOx and smoke which willhave an effect on human health. Hence, stringent emission normsand the depletion of petroleum fuels have necessitated the searchfor alternate fuels for diesel engines. On the other hand, due to therapid growth of automotive vehicles in transportation sector, theconsumption of oil keeps increasing. Most of the research workhas been done by mixing oil developed from waste plastic disposalwith heavy oil for marine application .The results showed thatwaste plastic disposal oil when mixed with heavy oils reducesthe viscosity significantly and improves the engine performance.However, very little has been done to test their use in high-speeddiesel engines. A pilot level method of recycling waste plastic dis-posal in India produces waste plastic oil of 25,000 liter/day. Thekind of plastic materials are Polyethylene, Polypropylene, Teflon,

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Nomenclature

LPG liquid petroleum gasTFC total fuel consumptionNOx oxides of nitrogen.UHC unburned hydrocarbon.CO carbon monoxideCO2 carbon dioxideTDC top dead centreCA BTDC crank angle before top dead centreY total percentages uncertainty

X1 uncertainty of total fuel consumptionX2 uncertainty of brake powerX3 uncertainty of brake thermal efficiencyX4 uncertainty of COX5 uncertainty of unburned hydrocarbonX6 uncertainty of NOx

X7 uncertainty of smoke numberX8 uncertainty of exhaust gas temperatureX9 uncertainty of pressure pickup

M. Mani et al. / Applied Thermal Engineering 29 (2009) 2738–2744 2739

Nylon and Dacron. For marine application, waste plastic oil is usedin marine diesel engine [19]. An industry plastic waste with marineheavy fuel oil reduces the viscosity of the heavy oil significantly.Plastic bags, bottles, ropes and nets trap, choke, starve and drownmany thousands of marine animals and seabirds around the worldeach year are threat the marine creatures [20].

2.1. Conversion process

The feed system consists of equipments for sizing hard, thickflexible and thin flexible materials, which normally constitutesthe municipal waste stream. The system essentially consists ofsorters and sizing equipments like crusher, cutter and shredder.The various sizes and shapes of the material are sorted into catego-ries suitable for crushing, cutting and shredding. The sorted mate-rial was crushed or cut or shredded and graded into uniform sizefor ease of handling and melting in the melting/preheating process.This process of sizing and grading the waste was semi automatic.The graded feed was stored in a hopper before feeding to the pro-cess by a conveyor feeder. The sorted feedstock of known compo-sition was stored separately for proportionate feeding forprocessing nonstandard feed design or processing special feed de-signs. The dust and other fine wastes collected from the cyclone fil-ter were disposed through a vent with particle size monitoringsystem. The assorted waste plastic was fed into a reactor alongwith 1% (by weight) catalyst and 10% (by weight) coal and main-tained at a temperature of 300 �C to 400 �C at atmospheric pres-sure for about 3 hours to 4 hours. The pyrolysis process involvesthe break down of large molecules to smaller molecules. Produceshydrocarbons with small molecular mass (e.g. ethane) that can beseparated by fractional distillation and used as fuels and chemicals.This process gives on weight basis 75% of liquid hydrocarbon,which is a mixture of petrol, diesel and kerosene, 5% to 10% resid-ual coke and the rest is LPG.

2.2. Comparison of waste plastic oil and waste tyre pyrolysis oil

Waste tyre pyrolysis liquids are a complex mixture of C5 to C20

organic compounds, with a great proportion of aromatics [4]whereas waste plastic oil is a mixture of C10 to C30 organic com-pounds. Waste plastic oil has high calorific value than the wastetyre pyrolysis oil. Sulphur and distillation temperature is lesserthan waste tyre pyrolysis oil. The properties of waste plastic oil,waste tyre pyrolysis oil [5,6] and diesel are compared in Table 1.The gaseous products and chemical composition of waste plasticoil are given in Tables 2 and 3.

3. Experimental setup

The schematic of the experimental set up is shown in Fig. 1.The research engine specifications are given in Table 4. An elec-

trical dynamometer was used to provide the engine load. An airbox was fitted to the engine for airflow measurement. The fuelflow rate was measured on volumetric basis using a buretteand a stopwatch. Chromel alumel thermocouple in conjunctionwith a digital temperature indicator was used to measure theexhaust gas temperature. A pressure transducer mounted onthe cylinder head with a charge amplifier and a computer wereused to measure and record the cylinder pressure. A TDC enco-der was used to detect the engine crank angle. An exhaust gasanalyzer was used to measure NOx/HC/CO emissions in the ex-haust. Smoke was measured in Bosch Smoke Units (BSU) by anAVL smoke meter. All the experiments were conducted at therated engine speed of 1500 rpm. All the tests were conductedby starting the engine with diesel only and then switched overto run with waste plastic oil. At the end of the test, the enginewas run for some time with diesel to flush out the waste plasticoil from the fuel line and the injection system.

4. Error analysis

Errors and uncertainties in the experiments can arise frominstrument selection, condition, calibration, environment, observa-tion, reading and test planning. Uncertainty analysis is needed toprove the accuracy of the experiments [7]. The percentage uncer-tainties of various parameters like brake power and brake thermalefficiency were calculated using the percentage uncertainties ofvarious instruments given in Table 5. An uncertainly analysis wasperformed using Eq. (1).

Y ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiðX2

1þX22þX2

3þX24þX2

5þX26þX2

7þX28þX2

9Þq

ð1Þ

Y ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffið1Þ2þð0:2Þ2þð1Þ2þð0:2Þ2þð0:2Þ2þð0:2Þ2þð1Þ2þð0:15Þ2þð1Þ2

q

Y ¼�2:28%

5. Results and discussion

A series of performance, emission and combustion tests werecarried out on a 4.4 kW constant speed engine using diesel andwaste plastic oil and the results are presented.

5.1. Combustion parameters

5.1.1. Delay periodFrom Fig. 2, it can be observed that the ignition delay of waste

plastic oil is considerably longer than that of diesel. The longer de-lay period of waste plastic oil, results in a rise in-cylinder peakpressure. It may also be seen that the ignition delay is longer byabout 2� CA to 2.5� CA for waste plastic oil than that of dieseland the peak pressure increases by 5 bar for waste plastic oil com-pared to diesel because of longer ignition delay.

Table 1Comparison of waste plastic oil, waste tyre pyrolysis oil and diesel.

Property Waste plastic oil Waste tyre pyrolysis oil Diesel

Density @ 30 �C in (g/cc) 0.8355 0.935 0.840Ash content (%) 0.00023 0.31 0.045Gross calorific value (kJ/kg) 44,340 42,830 46,500Kinematic viscosity, cst @ 40 �C 2.52 3.2 2.0Cetane number 51 – 55Flash point (�C) 42 43 50Fire point (�C) 45 50 56Carbon residue (%) 82.49 2.14 26Sulphur content (%) 0.030 0.95 0.045Distillation temperature (�C) @ 85% 344 381 328Distillation temperature (�C) @ 95% 362 388 340

1. Diesel engine 9. TDC position sensor

2. Alternator 10. Charge amplifier

3. Dynamometer controls 11. TDC amplifier circuit

4. Air box 12. A/D card

5. U – Tube manometer 13. Personal computer

6. Fuel tank 14. Exhaust gas analyzer

7. Fuel measurement flask 15. AVL smoke meter

8. Pressure pickup

14

13

9

8

1 2

7

6

5 4

10 12

11

315

Fig. 1. Experimental setup of the test engine.

Table 2Gaseous product of the waste plastic oil.

Component Quantity (wt%)

Methane 6.6Ethane ethylene 10.6Propane 7.4Propylene 29.1Iso-butane 1.9n-Butane 0.9C4 (unsaturated) 25.6Iso C5–n-C5 0.1C5+higher 15.3Hydrogen 2.5CO/CO2 <400 ppm

Table 3Chemical composition of waste plastic oil.

Composition Percentage

C10 61C10–C13 2.4C13–C16 8.5C16–C20 4.1C20–C23 7.6C23–C30 16.4

2740 M. Mani et al. / Applied Thermal Engineering 29 (2009) 2738–2744

5.1.2. Cylinder pressure crank angle diagramFig. 3 indicates the cylinder pressure with crank angle for both

fuels at rated power. The cylinder peak pressure for diesel is 67 barat rated power and 71 bar in the case of waste plastic oil. Highercylinder pressure in the case of waste plastic oil compared to dieselis due to the evaporation of waste plastic oil inside the cylinder byabsorbing heat from the combustion chamber. Longer ignition de-lay at high load range increases the pressure of waste plastic oilthan that of diesel. In other words, this period depicts the abnormalcombustion or premixed combustion. However, this is the usualbehaviour of high-octane fuel in high compression ratio engines.This can be controlled by proper selection of compression ratio.

5.1.3. Cylinder peak pressureThe variation of cylinder peak pressure with brake power for

waste plastic oil and diesel operation at different loads is givenin Fig. 4. It may be noticed that the cylinder peak pressure forthe waste plastic oil is higher than the diesel. The cylinder peakpressure for diesel increases from 57 bar at no load to 67 bar atrated power and from 54 bar at no load to 71 bar at rated powerin the case of waste plastic oil. In a CI engine, the peak pressure de-pends on the combustion rate in the initial stages, which is influ-enced by the amount of fuel taking part in the uncontrolledcombustion phase that is governed by the delay period. It is alsoaffected by the fuel mixture preparation during the delay period

[8]. Longer ignition delay is the reason for higher peak pressurein waste plastic oil operation at rated power.

5.1.4. Rate of heat releaseThe heat release rate of the waste plastic oil and diesel opera-

tion at rated power is given in Fig. 5. Rate of heat release can be cal-culated with this equation [9].

Rate of heat release ¼ ðr=r � 1ÞpðdV=dhÞ þ ð1=r � 1ÞVðdp=dhÞð2Þ

The first stage is from the start of ignition to the point where theheat release rate drops and this is due to the ignition of fuel–airmixture prepared during the delay period [8,9]. The second stagestarts from the end of the first stage to the end of combustion.Diesel shows the lowest heat release rate at initial stage and longercombustion duration at rated power. The heat release rate is 65J/�CA for diesel and 85 J/�CA for waste plastic oil. The maximumheat released in waste plastic oil is high compared to diesel. Itcan be noticed that in waste plastic oil, most of the heat release oc-curs only during the premixed combustion. Longer ignition delayresults in higher heat release during the premixed combustionphase. From Fig. 5 the heat release rate is higher in the case of wasteplastic oil due to the higher fuel–air ratio. The higher heat releaserate leads to an increase in exhaust gas temperature.

Table 5List of instruments and its range, accuracy and percentage uncertainties.

S. no. Instruments Range Accuracy Percentage uncertainties

1. Gas analyzer CO 0–10%, +0.02% to �0.02% +0.2 to �0.2CO2 0–20% +0.03% to �0.03% +0.15 to �0.15HC 0–10,000 ppm +20 ppm to �20 ppm +0.2 to �0.2NOx 0–5000 ppm +10 ppm to �10 ppm +0.2 to �0.2

2. Smoke level measuring instrument BSU 0–10 +0.1 to �0.1 +1 to �13. Exhaust gas temperature indicator 0–900 �C +1 �C to �1 �C +0.15 to �0.154. Speed measuring unit 0–1000 rpm +10 rpm to �10 rpm +0.1 to �0.15. Load indicator 0–100 kg +0.1 kg to �0.1 kg +0.2 to �0.26. Burette for fuel measurement +0.1 cc to �0.1 cc +1 to �17. Digital stop watch +0.6 s to �0.6 s +0.2 to �0.28. Manometer +1 mm to �1 mm +1 to �19. Pressure pickup 0–110 bar +0.1 kg to �0.1 kg +0.1 to �0.1

10. Crank angle encoder +1� to �1� +0.2 to �0.2

Table 4Engine specifications.

Make of model Kirloskar TAF1Engine type Four-stroke, CI, direct injection, air-cooled, single cylinder, constant speed engine.Bore (mm) 87.5Stroke (mm) 110Compression ratio 17.5:1Rated power@1500 rpm (kW) 4.4Nozzle opening pressure (bar) 200Injection timing (�CA) 23� BTDC

10

20

30

40

50

60

70

80

-30 -20 -10 0 10 20 30Crank angles (degrees)

Cyl

inde

r pre

ssur

e (b

ar)

DieselWaste plastic oil

Fig. 3. Variation of cylinder pressure crank angle diagram (full load).

-9

-8

-7

-6

-5

0 1 2 3 4 5

Brake power (kW)

Del

ay p

erio

d (b

TDC

)

Waste plastic oilDiesel

Fig. 2. Variation of delay period with brake power.

50

55

60

65

70

75

0 1 2 3 4 5

Brake power (kW)

Cyl

inde

r pea

k pr

essu

re (b

ar)

Waste plastic oilDiesel

Fig. 4. Variation of cylinder peak pressure with brake power.


5.2. Emissions

5.2.1. Oxides of nitrogenThe oxides of nitrogen in the emissions contain nitric oxide

(NO) and nitrogen dioxide (NO2). The formation of NOx is highlydependent on in-cylinder temperature, oxygen concentration andresidence time for the reactions to take place [10]. Fig. 6 showsthe comparison of oxides of nitrogen with brake power. It can benoticed that the NOx emission increases in the waste plastic oiloperation. NOx varies from 12.15 g/kWh at 25% of rated powerto 7.91 g/kWh at rated power for diesel and from 14.68 g/kWhat 25% of rated power to 8.93 g/kWh at rated power for wasteplastic oil. The reason for the increased NOx is due to the higherheat release rate and higher combustion temperature. CI enginesare always run lean and emit high amounts of NOx nonetheless.At high load, with higher peak pressures, and hence tempera-tures, and larger regions of close to stoichiometric burned gas,NO levels increase [11]. Increased ignition delay of waste plastic

30-

10-

10

30

50

70

90

110

130

-25 -20 -15 -10 -5 0 5 10 15 20 25Crank angle (degree)

Hea

t rel

ease

rate

(J/ º

CA

)


Fig. 5. Variation of heat release rate crank angle diagram (full load).

6

9

12

15

18

0 1 2 3 4 5Brake power (kW)

Oxi

des

of n

itrog

en (g

/kW

hr)

DieselWaste plasitc oil

Fig. 6. Variation of oxides of nitrogen with brake power.


oil promotes premixed combustion, by allowing more time forfuel to be injected prior to ignition, may also be another reasonfor increased NOx.

0.1

0.2

0.3

0.4

0.5

0 1 2 3 4 5

Brake power (kW)

Unb

urne

d hy

dro

carb

ons

(g/k

W h

r)


Fig. 7. Variation of unburned hydrocarbon with brake power.

5.2.2. Unburned hydrocarbonThe variation of unburned hydrocarbon with brake power for

tested fuels is shown in Fig. 7. Unburned hydrocarbon is a usefulmeasure of combustion inefficiency. Unburned hydrocarbon con-sists of fuel that is incompletely burned. The term hydrocarbonmeans organic compounds in the gaseous state and solid hydrocar-bons are the particulate matter [12]. At light load, large amounts ofexcess air and low exhaust temperature and lean fuel air mixtureregions may survive to escape into the exhaust. Unburned hydro-carbon varies from 0.431 g/kWh at 25% of rated power to0.1389 g/kWh at rated power for diesel. In the case of waste plasticoil it varies from 0.4393 g/kWh at 25% of rated power to 0.147g/kWh at rated power. From the results, it can be noticed thatthe concentration of the hydrocarbon of waste plastic oil is margin-ally higher than diesel. The reason behind increased unburnedhydrocarbon in waste plastic oil may be due to higher fumigationrate and non-availability of oxygen relative to diesel. At lighterloads due to charge homogeneity and higher oxygen availability,the unburned hydrocarbon level is less in the case of waste plasticoil, where as at higher load ranges due to higher quantity of fueladmission, unburned hydrocarbon increases.

5.2.3. Carbon monoxideThe variation of carbon monoxide with brake power is shown in

Fig. 8. Generally, CI engine operates with lean mixtures and hencethe CO emission would be low. CO emission is toxic and must becontrolled. It is an intermediate product in the combustion of ahydrocarbon fuel, so its emission results from incomplete combus-tion. Emission of CO is therefore greatly dependent on the air fuelratio relative to the stoichiometric proportions. Rich combustioninvariably produces CO, and emissions increase nearly linearlywith the deviation from the stoichiometry [13]. The concentrationof CO emission varies from 14.14 g/kWh at 25% of rated power to5.75 g/kWh at rated power for diesel, whereas it varies from18.51 g/kWh at 25% of rated power to 6.19 g/kWh at rated powerfor waste plastic oil. The results show that CO emission of wasteplastic oil is higher than diesel. The reason behind increased COemission is incomplete combustion due to reduced in-cylindertemperatures. The drastic increase in CO emission at higher loadsis due to higher fuel consumption.

5.2.4. Carbon dioxideCarbon dioxide occurs naturally in the atmosphere and is a nor-

mal product of combustion [14]. Ideally, combustion of a HC fuelshould produce only CO2 and water (H2O). The variation of carbondioxide with brake power is shown in Fig. 9. CO2 varies from1305.97 g/kWh at 25% of rated power to 789.36 g/kWh at rated

0

4

8

12

16

20

0 1 2 3 4 5

Brake power (kW)

Car

bon

mon

oxid

e (g

/kW

hr)

Diesel

Waste plastic oil

Fig. 8. Variation of carbon monoxide with brake power.

700

800

900

1000

1100

1200

1300

1400


Car

bon

diox

ide

(g/k

Whr

)


Fig. 9. Variation of carbon dioxide with brake power.

15

19

23

27

31


Brak

e th

erm

al e

ffici

ency

(%)


Fig. 11. Variation of brake thermal efficiency with brake power.


power for diesel. It can be observed that in waste plastic oil it var-ies from 1163.25 g/kWh at 25% of rated power to 888.715 g/kWh atrated power. From the results, it is observed that the amount ofCO2 produced while using waste plastic oil is lower than diesel.This may be due to late burning of fuel leading to incomplete oxi-dation of CO.

5.2.5. SmokeSmoke is nothing but solid soot particles suspended in exhaust

gas. Fig. 10 shows the variation of smoke with brake power. Smokevaries from 0.66 BSU to 5.3 BSU for diesel whereas in waste plasticoil it varies from 0.2 BSU to 3.48 BSU at rated power. It can be no-ticed that the smoke level for waste plastic oil is lower than diesel.The reason for the reduced smoke is the availability of premixedand homogeneous charge inside the engine well before the com-mencement of combustion. Higher combustion temperature, ex-tended duration of combustion and rapid flame propagation arethe other reasons for reduced smoke [15]. However, at higher loadrange due to non-availability of sufficient air and abnormal com-bustion there was a visible white smoke emission. Another reasonfor lower smoke may be better and complete combustion of fueldue to the oxygen present in the waste plastic oil.

5.3. Performance

5.3.1. Brake thermal efficiencyThe variation of brake thermal efficiency with brake power is

shown in Fig. 11 can be observed from the figure that the thermal

0

1

2

3

4

5

6

0 1 2 3 4 5Brake power(kW)

Smok

e (B

SU)


Fig. 10. Variation of smoke with brake power.

efficiency is 28.2% at rated power for diesel and for the waste plas-tic oil it is 27.4%. It is clear that the brake thermal efficiency of thewaste plastic oil is closer to diesel upto 75% of rated power, beyondwhich it starts decreasing. At full load, the efficiency is marginallyhigher for diesel fuel. This may be due to the fact that at full load,the exhaust gas temperature and the heat release rate are margin-ally higher for waste plastic oil compared to diesel [16]. This mayresult in higher heat losses and lower brake thermal efficiency inthe case of waste plastic oil.

5.3.2. Exhaust gas temperatureFig. 12 shows the variation of relative fuel air ratio with brake

power. The variation of exhaust gas temperature with brake poweris shown in Fig. 13. The exhaust gas temperature varies from221 �C at no load to 417 �C at rated power for diesel whereas inthe case of waste plastic oil it varies from 240 �C at no load to450 �C at rated power. The increase in exhaust gas temperaturewith engine load is clear from the simple fact that more amountof fuel was required by the engine to generate the extra powerneeded to take up the additional loading [17,18]. It can be seen thatthe fuel air ratio increases with brake power for both fuels. Fuel airratio is higher in the case of waste plastic oil compared to diesel atall loads. This results in higher exhaust gas temperature in the caseof waste plastic oil compared to diesel. Another reason for the in-creased exhaust gas temperature at rated power is the higher heatrelease.

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1.2 2.3 3.3 4.4

Brake power (kW)

Rel

ativ

e fu

el-a

ir ra

tio


Fig. 12. Variation of relative fuel–air ratio with brake power.

100

200

300

400

500


Exha

ust g

as te

mpe

ratu

re (º

C)


Fig. 13. Variation of exhaust gas temperature with brake power.


6. Conclusion

From the tests conducted with waste plastic oil and diesel on aDI diesel engine, the following conclusions are arrived:

� Engine was able to run with 100% waste plastic oil.� Ignition delay was longer by about 2.5 �CA in the case of waste

plastic oil compared to diesel.� NOx is higher by about 25% for waste plastic oil operation than

that of diesel operation.� CO emission increased by 5% in waste plastic oil compared to

diesel operation.� Unburned hydrocarbon emission is higher by about 15%.� Smoke reduced by 40% at rated power in waste plastic oil com-

pared to diesel operation.� Engine fueled with waste plastic oil exhibits higher thermal effi-

ciency upto 75% of the rated power.

Acknowledgements

The authors sincerely thank Prof. Alka Zadgoankar and Mr. Sur-esh Shah of Asian Electronic Ltd., for having supplied the fuelneeded to conduct the experimental study.

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