International Journal of Scientific & Engineering Research, Volume 4, Issue 11, November-2013 701
ISSN 2229-5518
Performance Analysis of Blends of Jatropha
Biodiesel
Partha Protim Borthakur, Pranjal Sarmah
Abstract—This paper investigates the performance analysis of blends of Jatropha biodiesel. The experiment was carried out on a single cylinder, four stroke, water cooled compression ignition engine where blends of Jatropha bio-diesel and pure diesel were tested with load variations and its effect on the parameters like brake thermal efficiency, exhaust gas temperature, volumetric efficiency, specific fuel consumption, air-fuel ratio, heat loss in brake power, heat content in Jacket cooling water, radiant heat loss and heat content in exhaust were observed and compared. Eventually, it was found that blends of Jatropha bio-diesel proved to be a better environmental friendly fuel than that of pure diesel.
Index Terms — Biodiesel,Blends, Environmental friendly fuel,Jatropha oil, Non conventional energy,.
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Biodiesel are biodegradable. They are non-toxic. They have significantly fewer noxious emissions than petrole- um-based diesel, when burned. They are renewable. With a much higher flash point than it is for petro-diesel (bio- diesels have a flash point of about 160 °C), biodiesel is clas- sified as a non-flammable liquid by the Occupational Safe- ty and Health Administration. This property makes a vehi- cle fuelled by pure biodiesel far safer in an accident than one powered by petroleum diesel or the explosively com- bustible gasoline. Combustion of biodiesel alone provides over 90% reduction in total unburned hydrocarbons, and a
75-90% reduction in aromatic hydrocarbons. When burned
in a diesel engine, biodiesel replaces the exhaust odor of
petroleum diesel with the pleasant smell of popcorn or French fries. Biodiesel further provides significant reduc- tions in particulates and carbon monoxide than petroleum diesel fuel. Thus, biodiesel provides a 90% reduction in cancer risks. In sum, the use of biodiesel will also reduce the following emissions, Carbon monoxide, Hazardous diesel particulates of solid combustion products, Acid rain- causing sulfur dioxide, arbon dioxide. The use of biodiesel can extend the life of diesel engines because it is more lu- bricating than petroleum diesel fuel, while fuel consump- tion, auto ignition, power output, and engine torque are relatively unaffected by biodiesel. Biodiesel is safe to han- dle and transport because it is as biodegradable as sugar,
10 times less toxic than table salt, and has a high flashpoint
of about 300 °F compared to petroleum diesel fuel, which
has a flash point of 125 °F, making it one of the safest alter- native fuels, in terms of combustibility.
The method used to blend the fuel is the most important factor contributing to blend accuracy. The two major blending tech-
niques used are splash blending and in-line (injection) blend- ing. Currently, the most widely implemented technique is splash blending. This blending process involves adding bio-
diesel or any other constituent to a fuel vehicle that is partially filled with diesel fuel. The blending occurs as the vehicle drives and the fuel splashes around in the tank. Unfortunately, in many cases, the vehicle does not drive far enough for the two fuels to blend uniformly. In addition, environmental fac- tors such as temperature and humidity can affect the speed at which the fuels blend. A second, more accurate blending method is in-line blending. This type of blending occurs at a fuel rack, where dedicated blending equipment delivers a me- tered amount of fuel into a waiting truck. Ethanol and other fuel additives are commonly blended using this method. With in-line blending, the correct ratio of blending component is metered with automated control valves into the diesel fuel before it is dispensed into a truck. Since the resulting fuel is blended prior to entering the truck, the mixing problem asso- ciated with splash blending is eliminated. Although in-line blending offers a more accurate blending method than splash blending, any mechanical system is subject to wear and/or failures. The need to test the diesel blend ratio after final mix- ing is necessary regardless of the blending method. An accu- rate method to determine the biodiesel blend is just as im- portant as an accurate blending method
It has been observed that lower molecular weight blended diesels have higher cloud points. Because fuel that has reached its cloud point will clog fuel filters, high blend percentages made from low molecular weight feed-stocks cannot be used in colder climates. Understanding the cli- mate to which engines will be subjected and the feed- stocks available will allow a distributor to determine the optimal blend ratio to deliver to customers. In many cases the optimal blend will change depending on the season.
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If waste vegetable oil (WVO) is used, it is filtered to re- move dirt, charred food, and other non-oil material often
found. Water is removed because its presence causes the triglycerides to hydrolyze, giving salts of the fatty acids (soaps) instead of undergoing transesterification to give bi- odiesel.
If waste vegetable oil (WVO) is used, it is filtered to remove dirt, charred food, and other non oil material often found. Water is removed because its presence causes the triglycer- ides to hydrolyze, giving salts of the fatty acids (soaps) in- stead of undergoing transesterification to give biodiesel.
A reaction scheme for transesterification is shown in the figure below. R1, R2, and R3 in this equation represent long carbon chains that are too lengthy to include in the dia- gram. Animal and plant fats and oils are typically made of triglycerides which are esters of free fatty acids with the trihydric alcohol, glycerol. In the transesterification pro- cess, the alcohol is deprotonated with a base to make it a stronger nucleophile. Commonly, ethanol or methanol is used. As can be seen, the reaction has no other inputs than the triglyceride and the alcohol. Normally, this reaction will proceed either exceedingly slowly or not at all. Heat, as well as an acid or base are used to help the reaction pro- ceed more quickly. It is important to note that the acid or base are not consumed by the transesterification reaction, thus they are not reactants but catalysts. Almost all bio- diesel is produced from virgin vegetable oils using the base-catalyzed technique as it is the most economical pro- cess for treating virgin vegetable oils, requiring only low temperatures and pressures and producing over 98% con- version yield (provided the starting oil is low in moisture and free fatty acids). However, biodiesel produced from other sources or by other methods may require acid cataly- sis which is much slower. Since it is the predominant method for commercial-scale production, only the base- catalyzed transesterification process will be described be- low.
During the esterification process, the triglyceride is reacted with alcohol in the presence of a catalyst, usually a strong alkali (NaOH, KOH, or Alkoxides). The main reason for doing a titration to produce biodiesel, is to find out how much alkaline is needed to completely neutralize any free fatty acids present, thus ensuring a complete transesterifi- cation. Empirically 6.25 g / L NaOH produces a very usable fuel. One uses about 6 g NaOH when the WVO is light in color and about 7 g NaOH when it is dark in color. The al- cohol reacts with the fatty acids to form the mono-alkyl es- ter (or biodiesel) and crude glycerol. The reaction between
the bio-lipid (fat or oil) and the alcohol is a reversible reac- tion so the alcohol must be added in excess to drive the re-
action towards the right and ensure complete conversion. (A) First stage: The glycerine phase is much denser than
biodiesel phase and the two can be gravity separated with glycerine simply drawn off the bottom of the settling vessel. In some cases, a centrifuge is used to separate the two materials faster.
(B) Second stage: Once the glycerine and biodiesel phases
have been separated, the excess alcohol in each phase is removed with a flash evaporation process or by distillation. In other systems, the alcohol is removed and the mixture neutralized before the glycerine and esters have been sepa- rated. In either case, the alcohol is recovered using distilla- tion equipment and is re-used. Care must be taken to en- sure no water accumulates in the recovered alcohol stream. (C) Third stage: The glycerine by-product contains unused catalyst and soaps that are neutralized with an acid and sent to storage as crude glycerine (water and alcohol are removed later, chiefly using evaporation, to produce 80-
88% pure glycerine).
(D) Final stage: Once separated from the glycerin, the bio-
diesel is sometimes purified by washing gently with warm water to remove residual catalyst, dried and then sent to storage..
The experiment was carried out on a single cylinder, four stroke, water cooled compression ignition engine where blends of Jatropha bio-diesel and pure diesel were tested with load variations and its effect on the parameters like brake thermal efficiency, exhaust gas temperature, volumetric effi- ciency, specific fuel consumption, air-fuel ratio, heat loss in brake power, heat content in Jacket cooling water, radiant heat loss and heat content in exhaust were observed and compared.
20% blends of jatropha oil and pure diesel were tested sepa-
rately. We obtained some good comparative results which are discussed bellow
Brake power and indicated power:
At loads of 6.02 kg, 9.02 kg and 11.92 kg, we find that the val- ues of BP are approximately same for both blended (20%) and pure diesels. But the IP seems to be quite higher in case of bio- diesel than diesel. This is mainly due to the more viscosity of
20% blended fuel. So, it will have a low calorific value as indi-
cated from the set of results. Bio-diesel blends(20%) have a calorific value of 43.20 MJ/Kg. as against 46.97 MJ/Kg.
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SFC:
At loads of 6.09 kg, 9.02 kg and 11.92 kg, results yielded that range of BMEP and IMEP values are slightly higher for bio- diesels than pure diesel. Increase in BMEP will increase the pressure on the piston rings, causing greater friction and will cause a greater side force on the piston skirt, causing greater friction. It will probably have an influence on the power ex- pended on oil pump water pump because there will have to be larger for an engine of the same displacement but greater out- put.
At nearly loads of 6.09 kg, 9.02 kg and 11.92 kg, we find that brake thermal efficiency is slightly lower for bio-diesel (20% blend) than diesel. This is due to higher viscosity of bio-diesel. Results are expected due to the lower energy content of the bio-diesel fuel. So at part loads, it will be lower, as a result of which bmep will be lower. Similarly the mechanical efficien- cies obtained are 34.19%, 43.82% and 51.26% for 20% blend as against 58.18%, 82.98% and 86.45% at the same corresponding loads, making it undesirable for commercial use in the long r
At nearly loads of 6.09 kg, 9.02 kg and 11.92 kg, the SFC ob- tained are 0.47 kg/kW-h, 0.40 kg/kW-h, 0.34 kg/kW-h for 20% blend against 0.43 kg/kW-h, 0.35 kg/kW-h and 0.32 kg/kW-h for pure diesel. Specific fuel consumption is slightly more in the case of blended fuels. This can be attributed to viscous nature, lower calorific value and high torque developed in case of bio-diesel.
Volumetric efficiency:
We observed the volumetric efficiencies are lower for the 20% blend with respect to the pure diesel for the same brake loads. The lower volumetric efficiency ascertains lower volume of fuel charge swept in the cylinder. This may be due to low heat- ing value of the blend supplemented by higher initial tem- perature by the domination of residual gases. This leads to increase in cylinder pressure in the case of bio-diesels. But the oxygenated nature of bio-diesel improves the combustion pro- cess. Similar results are also carried with A/F ratio.
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At approximate loads of 6.09 kg, 9.02 kg and 11.92 kg the range of HJW values so obtained are higher for pure diesel as compared to blended fuel. The greater heat content in Jacket Cooling Water is mainly due to poor combustion and poor atomization in the case of pure diesel. But in the case of blend- ed fuels, it induces lubricity. So, frictional losses decreases. So, the heat circulated by the coolant decreases, hence lesser heat content in Jacket cooling water.
HBP:
At nearly loads of 6.09 kg, 9.02 kg and 11.92 kg, the range of values of heat lost in brake power is more for pure diesel than the 20% blend one. It shows 19.76%, 24.47% and 27.01% for pure diesel as against 18.28%, 21.83% and 25.16% for the blend. Percentage indicates the fraction of the total power produced. Consequently, it contributes to increase in BMEP due to relatively less portion of the heat lost at higher torques.
RAD:
It is the radiated heat loss, expressed in terms of percentage of the total heat loss. At same loads, we observed that heat loss is greater for blended fuels as compared to pure diesel. This re- duces the chances of having an abnormal combustion as it prevents overheating of the area around the exhaust valves quickly. Also, it will have cleaner burning due to greater avail- able oxygen content. This increased radiated heat loss makes the bio-diesel a greater value as a home-heating fue
Heat lost
At near loads of 6.09 kg, 9.02 kg and 11.92 kg, the heat lost in exhaust gases are higher for pure diesel than the blend. This indicates low latent heat of vaporization of Jatropha oil in the blends and also more availability of oxygen in the case of blended fuels. This indicates a high exhaust gas temperature for pure diesel than bio-diesel.
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IMEP,BMEP,FMEP:
Again in case of indicated mean effective pressure for the load
6.08kg,9.10 kg and for 12.02 kg,we have seen that imep at first
increased from 4.5 bar to 6 bar and again there is a sharp in- creased in imep to 8 bar with increased in load with imep
6.01bar,7.15 bar and 7.91 bar for blend of 20%.And imep for
the pure diesel is increases for same load. For the bmep or brake mean effective pressure we have seen that for the load
6.08kg,9.10 kg and 12.02 kg for pure diesel we have the in- creased in bmep is 2.08bar,3.11 bar and 4.11 bar. For the blend fuel with increased in load 6.08kg,9.10 kg and 12.02 kg the increased in bmep are obtained from 2.06 to 4.01 bar.
From the above we can have the imep for both the cases is
large then bmep,this is because the imep is the average pres- sure over a cycle in the combustion chamber of the engine, that means the average pressure that would have to be present in each cylinder during the power stroke to generate the max- imum horsepower. While the bmep is the average pressure that imposed on the piston uniformly from top to the bottom of each power 705ylinder.
Torque and mechanical efficiency:
We find that for 100% pure diesel, for loads 6.02, 9.02 and
11.92 kg, the torque is 11.03, 16.52 and 21.81 Nm. While for
20% blend the torque is 10.93, 16.37 and 21.63 Nm. Thus we
find that as the load increases the torque also increases gradu-
ally for both 100% pure diesel and 20% blend.This is signifi-
cant since torque is directly proportional to load.
The mechanical efficiency of the engine for loads 6.02, 9.02 and
11.92 kg are 34.19, 43.82 and 51.26%, while for 20% blend, it is
58.18, 82.98 and 86.45% for the same loads. This is because
mechanical efficiency is directly proportional to brake power,
brake power directly depends on load. Thus as the load in-
creases the mechanical efficiency increases.
Air and fuel flow:
For 100% pure diesel for loads 6.02, 9.02 and 11.92 kg, the air
flow rate is 31.63, 31.15 and 30.40 kg/hr respectively. While for
20% blend the air flow rate is 29.78, 29.00 and 29.39 kg/hr for
the same loads. We observed that for 100% pure diesel the air
flow rate gradually decreases. But in case of 20% blend we
noticed that the air flow rate first of all decreases from 29.78 to
29.00 kg/hr for loads 6.02 and 9.02 kg, but for load of 11.92 kg
it again increases to 29.39 kg/hr. This indicates that there is
slight reduction in volumetric efficiency, since A/F ratio goes
on decreasing with increase in load as the intake temperature
Increases. But one advantage is of the fact that the delay peri-
od will decrease since increasein intake temperature at suction
will increase the temperature of compressed air inside the cyl-
inder, thus reducing the tendency to knock.
Also for fuel flow rate, we find that for 100% pure diesel for
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loads 6.02, 9.02 and 11.92 kg, the fuel flow rate is 0.78, 0.94 and
1.11 kg/hr. While for 20% blend the fuel flow rate is0.86, 1.06
and 1.20 kg/hr. In this case we observe that the fuel flow rate
gradually increases with an increase in load. Similarly for 10%
blend also the fuel flow rate increases gradually.This is signifi-
cant since A/F ratio decreases, thus enriching the desired mix-
ture to be introduced per stroke. Flame speed becomes low
and the timing losses increases.
Indicated thermal efficiency, Brake thermal efficiency and specific fuel consumption:
For 100% pure diesel we find for loads 6.02, 9.02 and 11.92 kg, the indicated thermal efficiencies to be 33.97, 29.48 and 31.24% respectively. And for 20 % blend, the indicated thermal effi- ciencies to be 53.47, 49.82 and 49.07 % for the same loads. Thus we observed that for 100% pure diesel the indicated thermal efficiency first decreases with an increase in load, and then it again increases. But for 20% blend, it decreases gradually with an increase in load.
And for 100% pure diesel we find for loads 6.02, 9.02 and 11.92 kg, the brake thermal efficiencies are 19.76, 24.47 and 27.01 % respectively. And for 20% blend, the brake thermal efficiencies are 18.28, 21.83 and 25.16 %. Thus we observed that both for
100% pure diesel and 10% blend, the brake thermal efficiencies increases gradually with an increase in load.
For 100% pure diesel, the specific fuel consumption is found to
be 0.43, 0.35 and 0.32Kg/Kw-Hr for loads 6.02, 9.02 and 11.92 kg respectively. And for 20% blend, it is 0.47, 0.40 and
0.34Kg/Kw-Hr respectively for the same loads. In this case we observed that the specific fuel consumption decreases gradual- ly with an increase in load for both pure diesel and 20% blend. Here in this case the indicated thermal efficiency is an ideal
efficiency. Again brake thermal efficiency deals with the effi- ciency deals with the measure of the output power that trans- fer from the engine. And specific fuel consumption is the fuel consumed per unit kilo-Watt per unit time. And in can in- creases with the increases with load increases
HBP, HJW and HExh:
For 100% pure diesel, we find for loads 6.02, 9.02 and 11.92 kg,
the HBP to be 19.76, 24.47 and 27.01 %. And for 20 % blend, it
is 18.28, 21.83 and 25.16 %. Thus in both the cases we se that
there is an increase in HBP with a gradual increase in load.
And for 100 % pure diesel, we find that for loads 6.02, 9.02 and
11.92 kg, the HJW to be 33.69, 32.70 and 30.71 %. And for 20 %
blend, it is 33.03, 28.83 and 29.42 % respectively for the same
loads.
We observe that for 100 % pure diesel the HJW decreases
gradually with an increase in load. And in all cases of 20%
blend all the parameters are increases gradually. This happen due to friction cause for hbp,colling water for the calorimeter in case for hjw,and the dissociation loss for the heat loss at exhaust gas.
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From results obtained above, it was concluded that blends of
Jatropha biodiesel proved to be both a better and undesired
fuel than that of pure diesel, depending on the type of work- ing conditions. But the IP seems to be quite higher in case of bio-diesel than diesel. This is mainly due to the more viscosity of 20% blended fuel. So, it will have a low calorific value as indicated from the set of results. At any load, the specific fuel consumption is higher for pure diesel than its blends of Jatropha bio-diesel. For all fuels tested , specific fuel consump- tion
increases with increase in load. One possible explanation for
this increment could be due to higher percentage of increase in
brake power with load as compared to fuel consumption. The heat loss in brake power is more for pure diesel than the blends. This could be due to better atomization and easy for- mation of volatile compounds in the blends of biodiesel tested due to availability of oxygen in the blended fuel. The presence of oxygen in the biodiesel helps for complete combustion of fuel in the engine. Addition of a small quantity of biodiesel with diesel increases the flash point of diesel. Hence, it is safer to store biodiesel. The greater heat content in jacket cooling water for pure diesel is mainly due to poor combustion, slow mixing and poor atomization. But in the case of blended fuels, viscosity gets reduced, hence frictional power decreases. So, the heat circulated by the coolant decreases, hence there is lesser heat content in Jacket Cooling Water. These results indi- cate that radiated heat loss for blended fuels are less than that of pure diesel. This could be mainly due to better combustion of blended fuels as they are of low viscosity and more volatile than that of diesel. So, viscosity gets reduced, hence frictional power decreases. On the whole it is concluded that the Jatropha oil will be a good alternative fuel for diesel engine both for agricultural and industrial applications.
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DETAILS ABOUT AUTHORS Partha Protim Borthakur Assistant Professor
Department of Mechanical Engineering,
Dibrugarh University Institute of Engineering and Tech- nology
Dibrugarh, Assam 786004
Email address - parthaborthakur22@gmail.com
Pranjal Sarmah
Assistant Professor
Department of Mechanical Engineering,
Dibrugarh University Institute of Engineering and Tech- nology
Dibrugarh, Assam 786004
Email address- pksnit07@gmail.com
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