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Performance and emission characteristics of a CI engine operating on diesel-POME (palm oil methyl ester) blends.

Introduction

Vegetable oils have become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. Vegetable oils are a renewable and potentially inexhaustible source of energy with an energetic content close to diesel. One of the problems faced in utilizing vegetable oils as CI engine fuels is their higher viscosity, ranging from 9 to 17 times greater than petroleum diesel fuel which results in poor fuel atomization, incomplete combustion and carbon deposition on the injector and the valve seats causing serious engine fouling. Other constraints of the direct application of vegetable oil were its low volatility and polyunsaturated character. To overcome these constraints, the processes like cracking or pyrolysis, transesterification, micro-emulsification, and blending with diesel, etc were especially developed [1-4].

There are many plant species which bear seeds rich in oil. Of these some promising species produce oils like karanja, jatropha, palm, sal, neem, mahua, etc have great potential to make biodiesel for supplementing other conventional sources like fossil fuels. In this study, the palm oil is chosen as a potential alternative for producing biodiesel and use as fuel in compression ignition engines.

Transesterification of Palm Oil

Transesterification is a chemical reaction which occurs between triglyceride and alcohol (generally methyl alcohol) in the presence of a catalyst (generally NaOH or KOH). It consists of a sequence of three consecutive reactions where triglycerides are converted to diglycerides; diglycerides are converted to monoglycerides followed by the conversion of monoglycerides to glycerol. In each step an ester is produced and thus three ester molecules are produced from one molecule of triglyceride [4].

Palm oil is taken a round bottom flask of volume 500 [cm.sup.3] for the present analysis. The palm oil in the flask was heated up to 50 to 60[degrees]C on a hot plate having magnetic stirrer arrangement. Then methanol and sodium hydroxide (catalyst) are added to the oil. The mixture was then stirred at the speed of 1300 rpm for all test runs. Alcohol to vegetable oil molar ratio is one of the important factor that affects the conversion efficiency of the process. For the transesterification process, 3 mol of alcohol are required for each mole of the oil. However, in practice, the molar ratio should be higher than this theoretical ratio in order to drive the reaction towards early completion.

After the completion of reaction, the products are allowed to separate into two layers. The lower layer contains glycerol and the top layer contains ester which is separated and purified using distilled water. Hot distilled water (10% by volume) is sprayed over the ester and stirred gently and allowed to settle in the separating funnel. The lower layer is discarded and upper layer (purified biodiesel) is separated [5].

Methyl esters of palm oil (Biodiesel) have several outstanding advantages among other new-renewable and clean engine fuel alternatives. The properties of POME prepared in this experimental analysis were compared with diesel fuel in table 1.

Experimental Setup

Fig. 1 shows the experimental setup and the table 2 shows the specification of the engine.

[FIGURE 1 OMITTED]

Testing Procedure

Testing was carried out at constant seed rate of 1500 rpm, at no load condition to 100% of rated load condition for all the test fuel. The engine was first operated on diesel fuel ant then with blends of POME (bio-diesel blends) with diesel. The fuel consumption rate, air consumption rate, composition of exhaust gases were recorded for 5 different loads at steady state condition. Emission measurements were carried out using MRU Delta 1600L gas analyzer and the soot concentration was measured with AVL smoke meter.

Results and Discussions

It was observed that, while operating the engine with blends of POME it was smooth at all loads. The performance and emission characteristics such as brake thermal efficiency, specific fuel consumption, the composition of exhaust gases and soot formation are presented for different percentages of load for diesel oil POME blends.

Performance characteristics

Fig.2 shows the variation of brake thermal efficiency with different loads for different biodiesel blends and diesel. The brake thermal efficiency is defined as the actual brake work per cycle divided by the amount of fuel chemical energy. From the figure it is observed that brake thermal efficiency increases with increase of load. But on increasing the blend percentage there is nominal decrease in the brake thermal efficiency.

Fig.3 shows the specific fuel consumption of POME blends with diesel. The specific fuel consumption keeps on decreasing with increasing load. But the specific fuel consumption of B50 is slightly higher when compared to that of diesel. This is due to low volatility of biodiesel.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

Emission characteristics

Fig.4 shows the variation of exhaust temperature with load. The exhaust gas temperature increases with increasing in load. Due to incomplete combustion of injected fuel and part of the combustion extending into the exhaust stroke, there is a slight increase in exhaust gas temperature with biodiesel compared to diesel.

Fig.5 shows the variation of CO emissions with respect to different loads. The CO emissions were found to be comparable at lower loads but at higher loads it is slightly higher than that of others. From the figure it is observed that the CO value is higher for the blend B20.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

Fig.6 shows the variation of HC emission with respect to load. The HC value gradually increases with increase in load.

[FIGURE 6 OMITTED]

Fig.7 shows the variation of Nox emission with respect to load. The NOx emission is almost same for all fuels at lower loads but at higher loads it is slightly higher than that of others.

[FIGURE 7 OMITTED]

Conclusion

* The brake thermal efficiency of B50-D50 is slightly lower than that of others but the differences were negligible.

* The specific fuel consumption of B50-D50 is higher when compared with other blends and diesel fuel.

* B30-D70 blend is best in HC and CO emissions when compared to other blends.

Acknowledgements

The authors would like to thank the Almighty God for directing their thoughts and guiding their deeds to complete this work successfully.

References

[1] Ayhan Demirbas., 2008, "Relationships derived from physical properties of vegetable oil and biodiesel fuels", Fuel, pp. 1743-1748.

[2] Ayhan Demirbas., 2005, "Biodiesel production from vegetable oils via catalytic and non-catalytic supercritical methanol transesterification methods", Progress in Energy and Combustion Science, pp. 466-487.

[3] Saravanan, S., Nagarajan, G., Lakshmi Narayana Rao, G., Sampath, S., 2007, "Feasibility study of crude rice bran oil as a diesel substitute in a DI-CI engine without modifications", Energy for Sustainable Development, pp. 83-91.

[4] Sharma, Y. C., Singh, B., Upadhyay, S. N., 2008, "Advancements in development and characterization of biodiesel: A review", Fuel, pp. 2355-2373

[5] Ramadhas, A. S., Muraleedharan, C., Jayaraj, S., 2005, "Performance and emission evaluation of a diesel engine fueled with methyl esters of rubber seed oil", Renewable Energy, pp. 1789-1800.

B. Deepanraj (1) *, P. Lawrence (1), P. Koshy Mathews (2) and V. Suneetha (3)

(1) Department of Mechanical Engineering, Priyadarshini Engineering College, Vaniyambadi-635751, Tamilnadu, India

(2) Department of Mechanical Engineering, Coimbatore Institute if Technology, Coimbatore, Tamilnadu, India

(3) School of Biotechnology, Chemical and Biomedical Engineering, VIT University, Vellore-632014, Tamilnadu, India E-mail: babudeepan@gmail.com
Table 1: Properties of biodiesel.

Properties                                Diesel   Biodiesel

Calorific value (KJ/kg)                   42400    41930
Specific gravity                          0.822    0.843
Viscosity at 30[degrees]C (centi-stoke)   8.54     45.14
Cloud point ([degrees]C)                  13       5
Pour point ([degrees]C)                   1        -1
Flash point ([degrees]C)                  61       120
Fire point ([degrees]C)                   74       110

Table 2: Specification of engine.

Manufacturer   Kirloskar comet

Engine Type    Four stroke, single cylinder,
               CI diesel engine
Bore           80 mm
Stroke         110 mm
Rated output   3.68 kW
Rated speed    1500 rpm
Loading type   Electrical generator
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Article Details
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Author:Deepanraj, B.; Lawrence, P.; Mathews, P. Koshy; Suneetha, V.
Publication:International Journal of Applied Engineering Research
Article Type:Report
Geographic Code:1USA
Date:Apr 1, 2009
Words:1300
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